Introduction
Vitamins are essential micronutrients that regulate key physiological processes such as growth, moulting, reproduction, and metabolic homeostasis in arthropods. Most insects acquire their B vitamin requirements through dietary intake, symbiotic microorganisms, or a combination of both sources (Douglas, Reference Douglas2017), while vitamin C has long been recognised as an essential micronutrient for normal development, fertility, and ecdysis in insects (Kramer and Seib, Reference Kramer and Seib1982). Vitamin E is a lipid-soluble antioxidant that plays a vital role in maintaining cellular integrity by mitigating oxidative damage. Its positive effects on reproduction and immune function have been extensively documented in vertebrates such as poultry and mammals (Yin et al., Reference Yin, Xu and Zhou2012; Fu et al., Reference Fu, Zhong, Wan, Xu, Yang, Han and Wang2022). Comparable evidence in arthropods remains limited, although vitamin E has been shown to promote development and successful reproduction in at least some insect species (Levinson and Navon, Reference Levinson and Navon1969). Despite growing interest in the nutritional ecology of beneficial arthropods, the role of vitamins in shaping predator performance, especially in phytoseiid mites, remains poorly understood. Unlike macronutrients such as proteins or carbohydrates, which are routinely studied in artificial diets (Huang et al., Reference Huang, Xu, Lv, Li, Wang and Gao2013; Pirayeshfar et al., Reference Pirayeshfar, Safavi, Sarraf Moayeri and Messelink2020; San et al., Reference San, Tuda, Nakahira and Takagi2020; Rho and Lee, Reference Rho and Lee2022), the inclusion and optimisation of vitamins in factitious rearing systems has received comparatively limited attention. Given their low dietary requirement but potentially high physiological impact, vitamins may serve as a critical yet underexplored component in enhancing the efficacy and sustainability of predator mass-rearing systems. Among the various vitamins potentially involved in arthropod physiology, vitamins B complex, C, and E were selected because they represent complementary metabolic, developmental, and antioxidant functions and had previously shown the most promising performance during preliminary diet optimisation for A. swirskii. The present study was therefore designed to evaluate the effects of vitamin delivery route using this validated formulation rather than to determine the relative importance of individual vitamins or the complete vitamin requirements of the predator.
Direct feeding of predatory mites with vitamin-enriched diets has also been investigated, albeit with inconsistent and often adverse outcomes. Khanamani et al. (Reference Khanamani, Fathipour, Talebi and Mehrabadi2017a) evaluated the effects of ten artificial diets on Neoseiulus californicus (McGregor), two of which included multivitamin additives: one with multivitamin capsules (AD9) and the other with syrup (AD10). Despite the nutritional enrichment, AD9 resulted in complete juvenile mortality (Immature survival = 0.00), and AD10 significantly reduced survival compared to the base diet. These findings suggest that while vitamins are essential micronutrients, their direct provision, especially in high concentrations or unsuitable formulations, may disrupt developmental processes or lead to nutritional imbalances. The study further reported sharp declines in fecundity and increased pre-adult mortality in vitamin-supplemented treatments, underscoring the need for careful assessment of vitamin form, dosage, and compatibility with the predator’s physiology. Such results indicate that although vitamins hold potential in optimising artificial diets, indiscriminate inclusion without empirical validation may compromise predator viability.
Indirect vitamin delivery to predatory mites, via enrichment of factitious prey, has shown more promising outcomes compared to direct feeding. In a recent study by Jahanbazi et al. (Reference Jahanbazi, Zibaee and Fathipour2025b), a tri-trophic system was used in which Carpoglyphus lactis L. served as the intermediate host for nutrient transfer. Among eight tested powdered diets, one treatment (Diet 4: wheat bran + yeast + vitamin mix) notably enhanced the demographic performance of Amblyseius swirskii (Athias-Henriot). Although the vitamin mix was not directly ingested by the predator, its incorporation into the prey’s diet significantly shortened the predator’s pre-adult duration and yielded comparable values for key population growth parameters (e.g. net reproductive rate and intrinsic rate of increase) relative to diets supplemented with various animal- and plant-derived proteins. These findings suggest that vitamins, when metabolised and assimilated by the prey, may undergo biochemical transformations that improve their bioavailability and compatibility for the predator. The superior performance of Diet 4 in reducing developmental time further underscores the potential value of targeted micronutrient supplementation, especially when delivered through a prey-mediated pathway, in enhancing the efficiency of predatory mite rearing systems.
Despite promising short-term outcomes following indirect vitamin supplementation via factitious prey, it remains unclear whether these benefits persist when vitamins are directly offered to the predator or accumulated over extended rearing. In previous studies, the inclusion of a vitamin mix (comprising B, C, and E) in the prey’s diet, particularly C. lactis, resulted in improved pre-adult development and favourable demographic traits in A. swirskii during first-generation assessments (Jahanbazi et al., Reference Jahanbazi, Zibaee and Fathipour2025b). However, no study has yet evaluated whether direct exposure to such vitamin-enriched diets, without trophic mediation, can sustain predator performance. Furthermore, the potential for adverse effects due to transgenerational accumulation of vitamins in predator tissues, especially when reared on vitamin-fed prey, remains unexplored. To address these knowledge gaps, the present study pursued a two-tiered approach: (i) assessing the demographic responses of A. swirskii to direct consumption of a vitamin-enriched dry diet, and comparing it with previously tested prey-based delivery systems, and (ii) investigating long-term demographic stability across four generational checkpoints (G1, G5, G10, and G20) when A. swirskii was reared on two vitamin-supplemented prey species (T. putrescentiae and C. lactis). This design enabled us to disentangle the short- and long-term effects of dietary vitamin exposure across different trophic routes, offering novel insights into the risks and benefits of micronutrient manipulation in artificial predator-prey food chains.
Materials and methods
Stock culture of stored mite
Populations of C. lactis and T. putrescentiae used in this study were initially sourced from the University of Tehran and Tarbiat Modares University, respectively. Upon acquisition, both species were transferred to the Entomology Laboratory at the Faculty of Agriculture, Tarbiat Modares University, where they were purified and subsequently maintained under standardised conditions (25 ± 1 °C, 60 ± 5% RH, and a 16:8 h (L:D) photoperiod) in Plexiglas containers (10 × 7 × 4 cm). For the long-term rearing experiment spanning 20 consecutive generations of A. swirskii, both mite species were continuously propagated on a formulated dry diet composed of wheat bran, baker’s yeast, and a vitamin mix (equal proportions of vitamins B complex, C, and E).
Stock colony of A. swirskii
The initial colony of A. swirskii was obtained in 2022 by a company serving as the official representative of the Biobest Company in Iran. The rearing setup consisted of a transparent polyethene sheet (20 × 25 cm) placed atop a water-saturated sponge of the same size, all housed within a plastic tray (25 × 40 cm). To prevent mite escape, moistened strips of folded tissue were positioned along the tray edges, partially immersed in water, following the method described by McMurtry and Scriven (Reference McMurtry and Scriven1985). Cotton fibres were dispersed across the surface to promote oviposition and provide refuge. The colony was maintained in a controlled environment chamber set at 25 ± 1 °C, 60 ± 5% RH, and a 16:8 h (L:D) photoperiod. Prior to the initiation of the breeding experiments, predators were fed every four days with a mixture of plant-derived pollen. During quality monitoring stages, the colony was provisioned with storage mites reared on the specified experimental diets.
Preparation of various treatments
The dry diets used in this study were formulated using fixed proportions: 1 part wheat bran, 1/3 part baker’s yeast, and 1/4 part vitamin mixture. following the formulation previously established for artificial diets of A. swirskii (Jahanbazi et al., Reference Jahanbazi, Zibaee and Fathipour2025b, Reference Jahanbazi, Zibaee and Fathipour2026). The vitamin blend was composed of equal amounts of vitamins B complex, C, and E. The mixed pollen component consisted of equal parts corn pollen and bee-collected flower pollen. All ingredients were finely ground and homogenised using a sieve to ensure uniform particle size. The prepared diets were stored at 4 °C for short-term use to maintain their nutritional integrity.
Experimental units
To establish the experimental arenas, green plastic discs (3 × 3 × 0.1 cm) were positioned on moistened sponges placed within plastic containers (7 × 5 × 4 cm) partially filled with water to maintain ambient humidity. Strips of moist tissue paper were aligned along the borders of each arena to deter mite escape, while tufts of cotton fibres were placed centrally to provide suitable microhabitats for oviposition and shelter. Water levels were monitored and replenished daily to ensure environmental consistency during the experimental period.
Experimental setup and generational evaluation
To standardise the physiological condition of the predatory mite (A. swirskii) before experimental treatments, the colony was reared for three successive generations on a mixed pollen diet consisting of Typha latifolia L., Crocus sativus L. (saffron), Prunus amygdalus Batsch (almond), and Caesalpinia gilliesii (Hook.) D. Dietr (bird-of-paradise). The pollen mixture (equal proportions of each pollen type) represents the standard colony maintenance diet routinely used in our laboratory for long-term maintenance of A. swirskii colonies and was applied solely for colony standardisation prior to the experiments. During this preconditioning phase, A. swirskii individuals were fed every four days with a mixture of plant-derived pollen as their primary food source. Additionally, for periodic quality assessments during colony maintenance, predators were also offered storage mites (C. lactis and T. putrescentiae) that had been previously reared on the same wheat bran + baker’s yeast + vitamin mixture.
For synchronisation, approximately 50 mated females were randomly selected from the stock colony and allowed to oviposit for 24 h. One freshly laid egg per female was then isolated and transferred individually to experimental arenas to ensure uniform age cohorts. Upon larval emergence, the individuals were randomly assigned to the dietary treatments. These included two storage mite species as prey (C. lactis and T. putrescentiae) that had been reared for three successive generations previously on a vitamin-enriched dry diet, and a treatment in which the same dry diet was directly provided to the predator. Each predator received 25–35 immature prey (larvae and nymphs only) during its juvenile stage, and 45–55 prey individuals daily during adulthood. In the dry diet treatment, a standardised amount of powdered diet, corresponding to one tip of a size 0000 fine paintbrush, was provided every other day. This quantity was previously determined to be sufficient to ensure continuous food availability, and leftover material was carefully removed to maintain hygienic conditions.
All individuals were monitored daily under a stereomicroscope to record survival and developmental transitions. After emergence, male–female pairs were kept together until female death, with males replaced when necessary. Daily fecundity, longevity, and reproductive periods were recorded throughout each female’s life.
To assess long-term prey suitability, life table parameters of A. swirskii were evaluated at three time points: generations 5, 10, and 20. All experiments were conducted in a growth chamber maintained at 25 ± 1 °C, 60 ± 5% RH, and a 16:8 h (L:D) photoperiod.
Life table analysis and demographic evaluation
Developmental duration, reproductive traits, and key population parameters including gross reproductive rate (GRR), net reproductive rate (R 0), intrinsic rate of increase (r), finite rate of increase (λ), and mean generation time (T) were calculated based on the age-stage, two-sex life table approach developed by Chi and colleagues (Chi and Liu, Reference Chi and Liu1985; Chi, Reference Chi1988; Chi et al., Reference Chi, You, Atlıhan, Smith, Kavousi, Özgökçe and Gökçe2020). This method enables accurate estimation of demographic metrics by accounting for the stage differentiation and contributions of both sexes throughout development. Life table data were collected from A. swirskii individuals fed on different astigmatid prey treatments and a dry diet.
In addition to the primary life history indices, age-specific survival rate (lx), age-stage-specific fecundity (fxj), age-specific fecundity (mx), and age-stage-specific population structure (pxj) (the proportion of individuals at age x and stage j available in the environment) were computed to illustrate the full demographic dynamics and reproductive patterns of the predator. All calculations were performed using the TWOSEX-MSChart software (Chi, Reference Chi2023). Statistical differences among treatments were determined using a paired bootstrap test with 100,000 resampling iterations, and standard errors were estimated via the same bootstrap procedure (Efron and Tibshirani, Reference Efron and Tibshirani1993; Reddy and Chi, Reference Reddy and Chi2015). These analyses provided robust comparisons of predator performance across dietary treatments under controlled environmental conditions.
Results
Demographic outcome of A. swirskii when directly fed with a vitamin-supplemented dry diet
Direct feeding of A. swirskii with a dry diet consisting of wheat bran, yeast, and a vitamin mix (B complex, C, and E) failed to support complete development and reproduction. Among 40 individuals tested, only three (7.5%) reached adulthood, comprising one male and two females, none of which laid any eggs during their lifetime. The adult females survived for an average of 7.3 days without oviposition, while the single male lived for 7 days. Furthermore, the average durations of the protonymph and deutonymph stages were prolonged, measured at 4.9 and 6.3 days, respectively, highlighting developmental inefficiency. These outcomes suggest that the offered dry formulation did not adequately support feeding and/or nutrient utilisation required for normal development. Consequently, no stable long-term rearing could be achieved on this formulation. Given the extremely low adult emergence and total absence of fecundity, life table analyses could not be conducted for this treatment.
Demographic responses of A. swirskii over successive generations on dry diet supplemented with mixed vitamin and mixed pollen
Successive generations of A. swirskii reared on a dry diet enriched with both a vitamin mix (B complex, C, and E) and mixed pollen (corn and bee-collected) displayed stable demographic performance across 20 generations (G1–G20), as shown in tables 1 and 2. The duration of the egg stage ranged from 1.98 days in G5 to 2.53 days in G1, with G5 being significantly shorter than other generations (P < 0.05). Other immature stages, including larval and protonymphal durations, remained statistically similar across generations. The deutonymphal period varied slightly (3.58–3.69 days) without significant differences, resulting in a pre-adult duration that remained relatively consistent across generations, except for a significantly shorter period observed in G5 (8.13 days) compared to other generations (P < 0.05). Immature survival remained statistically stable across generations, fluctuating between 0.80 in G1 and 0.89 in G20, with no significant differences observed (P > 0.05), indicating sustained juvenile viability over time.
Duration of different life stages (days) and fecundity (eggs/female) (mean ± SE) of Amblyseius swirskii when fed on the supplemented dry diet
Table 1 Long description
Mean plus or minus standard error is reported for life stage durations in days and fecundity in eggs per female for four groups labeled, G1, G5, G10, and G20, with sample sizes shown in parentheses for each row and group. Egg duration is 2.53 with 0.09 and letter a at G1 with 36 individuals, 1.98 with 0.12 and letter b at G5 with 49, 2.40 with 0.10 and letter a at G10 with 45, and 2.36 with 0.11 and letter a at G20 with 45. Larva duration is 1.03 with 0.03 letter a at G1, 1.10 with 0.07 letter a at G5, 1.13 with 0.08 letter a at G10, and 1.11 with 0.08 letter a at G20, with sample sizes 36, 49, 45, and 45. Protonymph duration is 1.00 with 0.00 letter a for all groups, with sample sizes 34, 42, 38, and 38; deutonymph duration is 3.66 with 1.00 letter a at G1, 3.58 with 0.09 letter a at G5, 3.69 with 0.10 letter a at G10, and 3.67 with 0.10 letter a at G20, with sample sizes 32, 40, 36, and 36. Pre adult duration is 8.28 with 0.13 letter a at G1, 7.65 with 0.16 letter b at G5, 8.28 with 0.12 letter a at G10, and 8.19 with 0.13 letter a at G20, with sample sizes 32, 40, 36, and 36; immature survival rate is 0.89 with 0.05 letter a at G1, 0.82 with 0.05 letter a at G5, 0.80 with 0.05 letter a at G10, and 0.80 with 0.05 letter a at G20, with sample sizes 36, 49, 45, and 45. Male longevity is 43.00 with 0.63 letter a at G1 with 12 individuals, 40.17 with 0.96 letter b at G5 with 18, 41.13 with 1.22 letters ab at G10 with 15, and 41.13 with 1.22 letters ab at G20 with 15; female longevity is 47.20 with 1.24 letter a at G1 with 20, 45.73 with 0.90 letter a at G5 with 22, 46.52 with 1.25 letter a at G10 with 21, and 46.10 with 1.09 letter a at G20 with 21. Adult longevity is 37.34 with 0.91 letter a at G1 with 36, 35.58 with 0.75 letter a at G5 with 43, 36.00 with 0.97 letter a at G10 with 36, and 35.83 with 0.87 letter a at G20 with 36; total lifespan is 41.08 with 2.31 letter a at G1 with 45, 36.18 with 2.24 letter a at G5 with 49, 36.47 with 2.49 letter a at G10 with 45, and 36.22 with 2.46 letter a at G20 with 45. APOP is 2.35 with 0.11 letter a at G1 with 20, 2.23 with 0.09 letter a at G5 with 22, 2.38 with 0.11 letter a at G10 with 21, and 2.29 with 0.10 letter a at G20 with 21; TPOP is 10.75 with 0.19 letters ab at G1, 10.23 with 0.24 letter b at G5, 10.86 with 0.19 letter a at G10, and 10.62 with 0.22 letters ab at G20, with sample sizes 20, 22, 21, and 21. Oviposition days are 19.15 with 0.58 letter a at G1, 18.18 with 0.35 letter a at G5, 18.29 with 0.59 letter a at G10, and 18.29 with 0.50 letter a at G20, with sample sizes 20, 22, 21, and 21; fecundity is 23.70 with 0.73 letter a at G1, 22.23 with 0.58 letter a at G5, 22.38 with 0.74 letter a at G10, and 22.38 with 0.68 letter a at G20, with sample sizes 20, 22, 21, and 21.
Note: *APOP, adult pre-oviposition period. **TPOP, total pre-ovipositional period (from egg to first oviposition). Means followed by different letters within the same row are significantly different. (P < 0.05, paired bootstrap test). The values inside the parentheses are the number of individuals evaluated. Dry diet composition: wheat bran, baker’s yeast, vitamin mixture (equal proportions of vitamins B complex, C, and E), and mixed pollen consisting of corn pollen and bee-collected flower pollen in equal amounts.
Mean (± SE) of population growth parameters of Amblyseius swirskii when fed on the supplemented dry diet
Table 2 Long description
Population growth parameters are reported as mean plus or minus standard error for four groups labeled G1, G5, G10, and G20. Gross reproductive rate in eggs per individual is 15.15 plus or minus 2.09 for G1, 12.50 plus or minus 1.78 for G5, 13.46 plus or minus 1.91 for G10, and 13.36 plus or minus 1.89 for G20, with sample sizes 36, 49, 45, and 45. Net reproductive rate in eggs per individual is 13.17 plus or minus 2.00 for G1, 9.98 plus or minus 1.60 for G5, 10.44 plus or minus 1.70 for G10, and 10.44 plus or minus 1.69 for G20, with the same sample sizes by group. Intrinsic rate of increase per day is 0.142 plus or minus 0.01 for G1, 0.133 plus or minus 0.01 for G5, 0.129 plus or minus 0.01 for G10, and 0.131 plus or minus 0.01 for G20. Finite rate of increase per day is 1.153 plus or minus 0.01 for G1, 1.142 plus or minus 0.01 for G5, 1.138 plus or minus 0.01 for G10, and 1.140 plus or minus 0.01 for G20. Mean generation time in days is 18.11 plus or minus 0.27 for G1, 17.29 plus or minus 0.37 for G5, 18.20 plus or minus 0.32 for G10, and 17.90 plus or minus 0.36 for G20. Each mean in every row carries the letter a.
Note: Means followed by different letters within the same row are significantly different. (P < 0.05, paired bootstrap test). The values inside the parentheses are the number of individuals evaluated. GRR: gross reproductive rate; R 0: net reproductive rate; r: intrinsic rate of increase; λ: finite rate of increase; T: mean generation time. Dry diet composition: wheat bran, baker’s yeast, vitamin mixture (equal proportions of vitamins B complex, C, and E), and mixed pollen consisting of corn pollen and bee-collected flower pollen in equal amounts.
Adult longevity showed no meaningful fluctuation, averaging around 36 days. Female longevity remained relatively stable (45.7–47.2 days), while male longevity ranged from 40.2 to 43 days. Total pre-oviposition period (TPOP) and APOP values exhibited minor generational variation, with TPOP ranging from 10.23 to 10.86 days and APOP from 2.23 to 2.38 days. The oviposition days (approximately 18.2–19.1 days) and fecundity (22.23–23.7 eggs/female) remained statistically unchanged, reflecting long-term reproductive consistency.
Similarly, life table parameters showed no significant variation. The intrinsic rate of increase (r) remained between 0.129 and 0.142 day−1, while net reproductive rate (R 0) ranged from 9.98 to 13.17. Mean generation time (T) fluctuated slightly across generations (17.29–18.11 days) but without significant change (P > 0.05). As shown in figs 1 and 2, age-stage structure or Age-stage-specific population structure curves (pxj) and reproductive curves (lx, mx, fxj) were comparable across all generations, further confirming the demographic reliability of the dry diet enriched with vitamin and pollen for A. swirskii over prolonged rearing cycles.
Age-stage-specific population structure curves (pxj) of immature Amblyseius swirskii when fed on the supplemented dry diet.
Figure 1 Long description
Four line graphs labeled G1, G5, G10 and G20. The horizontal axis is labeled, Age day, with a range from 0 to 12. The vertical axis is labeled, Age stage specific population structure p x j, with a range from 0 to 1. A legend lists Egg, Larva, Protonymph, Deutonymph. Line styles: Egg is a solid line, Larva is a dotted line, Protonymph is a dashed line, Deutonymph is a long dashed line. G1 plotted values: Egg: (0, 1), (1, 1), (2, 0). Larva: (1, 0), (2, 0.5), (3, 0). Protonymph: (2, 0), (3, 0.5), (4, 0). Deutonymph: (3, 0), (6, 1), (9, 0). Key points: Egg remains at 1 from age 0 to 1 then reaches 0 at age 2. Larva peaks at 0.5 at age 2. Protonymph peaks at 0.5 at age 3. Deutonymph peaks at 1 at age 6. G5 plotted values: Egg: (0, 1), (1, 1), (2, 0). Larva: (1, 0), (2, 0.4), (3, 0). Protonymph: (2, 0), (3, 0.4), (4, 0). Deutonymph: (3, 0), (6, 0.8), (9, 0). Key points: Larva peak is 0.4 at age 2. Protonymph peak is 0.4 at age 3. Deutonymph peak is 0.8 at age 6. G10 plotted values: Egg: (0, 1), (1, 1), (2, 0). Larva: (1, 0), (2, 0.6), (3, 0). Protonymph: (2, 0), (3, 0.5), (4, 0). Deutonymph: (3, 0), (6, 0.8), (9, 0). Key points: Larva peak is 0.6 at age 2. Protonymph peak is 0.5 at age 3. Deutonymph peak is 0.8 at age 6. G20 plotted values: Egg: (0, 1), (1, 1), (2, 0). Larva: (1, 0), (2, 0.4), (3, 0). Protonymph: (2, 0), (3, 0.4), (4, 0). Deutonymph: (3, 0), (6, 0.8), (9, 0). Key points: Larva peak is 0.4 at age 2. Protonymph peak is 0.4 at age 3. Deutonymph peak is 0.8 at age 6. Comparison across G1, G5, G10, G20 using the listed points: Egg reaches 0 at age 2 in all four graphs. Larva peaks at age 2 in all four graphs, with peak values 0.5 in G1, 0.4 in G5, 0.6 in G10, 0.4 in G20. Protonymph peaks at age 3 in all four graphs, with peak values 0.5 in G1, 0.4 in G5, 0.5 in G10, 0.4 in G20. Deutonymph peaks at age 6 in all four graphs, with peak values 1 in G1 and 0.8 in G5, G10 and G20. The image B showing four line graphs labeled G1, G5, G10 and G20. The horizontal axis has a range from 0 to 60. The vertical axis has a range from 0 to 1. A legend lists Female and Male. Line styles: Female is a solid line, Male is a dotted line. G1 plotted values: Female: (10, 0.6), (40, 0.6), (50, 0.4), (55, 0.2), (60, 0). Male: (10, 0.35), (40, 0.35), (50, 0.2), (55, 0.1), (60, 0). Key points: Female remains at 0.6 from age 10 to 40, then declines to 0 at age 60. Male remains at 0.35 from age 10 to 40, then declines to 0 at age 60. G5 plotted values: Female: (10, 0.45), (40, 0.45), (50, 0.2), (55, 0.05), (60, 0). Male: (10, 0.35), (40, 0.3), (50, 0.1), (55, 0.05), (60, 0). Key points: Female remains at 0.45 from age 10 to 40, then declines to 0 at age 60. Male is 0.35 at age 10 and 0.3 at age 40, then declines to 0 at age 60. G10 plotted values: Female: (10, 0.45), (40, 0.45), (50, 0.3), (55, 0.15), (60, 0). Male: (10, 0.3), (40, 0.3), (50, 0.2), (55, 0.1), (60, 0). Key points: Female remains at 0.45 from age 10 to 40, then declines to 0 at age 60. Male remains at 0.3 from age 10 to 40, then declines to 0 at age 60. G20 plotted values: Female: (10, 0.45), (40, 0.45), (50, 0.25), (55, 0.1), (60, 0). Male: (10, 0.3), (40, 0.3), (50, 0.15), (55, 0.05), (60, 0). Key points: Female remains at 0.45 from age 10 to 40, then declines to 0 at age 60. Male remains at 0.3 from age 10 to 40, then declines to 0 at age 60. Comparison across G1, G5, G10, G20 using the listed points: At age 10 and age 40, Female values are 0.6 and 0.6 in G1 and 0.45 and 0.45 in G5, G10 and G20. At age 10 and age 40, Male values are 0.35 and 0.35 in G1, 0.35 and 0.3 in G5, 0.3 and 0.3 in G10 and 0.3 and 0.3 in G20. At age 50, Female values are 0.4 in G1, 0.2 in G5, 0.3 in G10, 0.25 in G20. At age 50, Male values are 0.2 in G1, 0.1 in G5, 0.2 in G10, 0.15 in G20. At age 60, Female and Male values are 0 in all four graphs.
Age-specific survivorship (lx), age-specific fecundity (mx), and age-stage-specific fecundity (fxj) of Amblyseius swirskii when fed on the supplemented dry diet.
Figure 2 Long description
The horizontal axis represents age in days, ranging from 0 to 60. The left vertical axis shows survivorship (lx) from 0 to 1, while the right vertical axis shows fecundity from 0 to 2.5. Each graph includes three lines: a solid line for survivorship (lx), a dotted line for age-stage-specific fecundity (fxj) and a dashed line for age-specific fecundity (mx). In G1, survivorship declines sharply after day 30, with fecundity peaking around day 10. In G5, survivorship decreases after day 30, with fecundity peaking slightly later than G1. G10 shows a similar pattern, but with a more gradual decline in survivorship and a later fecundity peak. G20 displays the most gradual survivorship decline, with fecundity peaking around day 15. The graphs highlight differences in the timing and height of fecundity peaks and the onset of survivorship decline across generations.
Demographic responses of A. swirskii over successive generations on C. lactis
Continuous rearing of A. swirskii on C. lactis fed with wheat bran, yeast, and vitamin mixture over 20 generations revealed no significant generational decline in demographic traits, indicating long-term nutritional adequacy of this prey. Developmental durations across all immature stages (egg to deutonymph) remained statistically stable (P > 0.05), with total pre-adult duration fluctuating narrowly between 6.52 and 6.58 days (table 3). Immature survival rates were consistently high across generations (ranging from 90% to 94%), reflecting sustained prey quality.
Long-term effects of feeding Amblyseius swirskii on Carpoglyphus lactis fed wheat bran + baker’s yeast + vitamin mixture (B, C, and E) on the duration of different life stages (days), fecundity (eggs/female) and immature survival (%) (mean ± SE)
Table 3 Long description
Parameters are reported for generations G1, G5, G10, and G20 as mean plus or minus SE, with sample sizes shown in parentheses for each row and generation. Egg duration is 1.95, 2.07, 2.02, and 1.96 days for G1, G5, G10, and G20. Larva duration is 1.00 days for all four generations, and protonymph duration is 1.00 days for all four generations. Deutonymph duration is 2.68, 2.50, 2.55, and 2.57 days, and pre adult duration is 6.58, 6.52, 6.55, and 6.52 days. Immature survival rate is 0.90, 0.93, 0.93, and 0.94. Male longevity is 25.50, 29.19, 29.00, and 29.00 days, and female longevity is 28.96, 29.10, 30.86, and 30.70 days. Adult longevity is 21.11, 22.62, 23.48, and 23.52 days, and total lifespan is 25.50, 27.58, 28.26, and 28.38 days. APOP is 2.04, 2.00, 2.00, and 2.00 days, and TPOP is 8.92, 9.00, 8.95, and 9.00 days. Oviposition days are 16.62, 16.05, 17.55, and 18.07 days, and fecundity is 30.75, 32.05, 29.86, and 32.78 eggs per female.
Note: G generation, APOP adult pre-oviposition period, TPOP total pre-oviposition period (from egg to first oviposition). The means followed by different small letters within the same row are comparisons among different generations (P < 0.05, paired bootstrap test).
Notably, adult longevity showed a slight numerical increase across generations, although these differences were not statistically significant. Females in G5, G10, and G20 lived approximately 5–6% longer than those in G1, and male longevity increased by up to 14% from G1 (25.5 days) to G20 (29.0 days). As a result, total lifespan extended from 25.5 days in G1 to 28.4 days in G20. Oviposition days also lengthened over time, reaching 18.1 days in G20 compared to 16.6 days in G1. Fecundity peaked in G5 (32.05 eggs/female), followed by G20 (32.78 eggs/female), suggesting a minor non-linear fluctuation with no evidence of performance decline.
Life table parameters supported these observations. Although GRR and net reproductive rate (R 0) showed slight variations; G1 registering the highest GRR (32.31) and G20 the highest R₀ (18.83); intrinsic rate of increase (r), finite rate of increase (λ), and generation time (T) remained statistically unchanged (table 4). The r-values across generations ranged narrowly between 0.176 and 0.185 day−1.
Age-stage structure (pxj) curves (fig. 3) displayed consistent overlapping patterns with well-synchronised developmental transitions, while survivorship (lx) and fecundity curves (mx and fxj) exhibited stable profiles across generations (fig. 4). These results collectively indicate that C. lactis, when reared for 20 generations on a vitamin-supplemented diet, provides a reliable and demographically stable prey source for A. swirskii during extended mass-rearing cycles.
Generation-dependent population growth parameters (mean ± SE) of Amblyseius swirskii reared on Carpoglyphus lactis fed with wheat bran + baker’s yeast + vitamin mixture (B complex, C, and E)
Table 4 Long description
Population growth parameters are reported as mean plus or minus standard error for four generations labeled G1, G5, G10, and G20. Parameters listed are GRR and R0 in eggs per individual, r per day, lambda per day, and T in days. GRR values are 32.31 plus or minus 2.81 at G1, 16.40 plus or minus 2.68 at G5, 16.83 plus or minus 2.56 at G10, and 20.57 plus or minus 2.6 at G20. R0 values are 17.57 plus or minus 2.60 at G1, 14.96 plus or minus 2.51 at G5, 15.28 plus or minus 2.44 at G10, and 18.83 plus or minus 2.52 at G20. r values are 0.183 plus or minus 0.01 at G1, 0.176 plus or minus 0.01 at G5, 0.176 plus or minus 0.01 at G10, and 0.185 plus or minus 0.01 at G20. Lambda values are 1.201 plus or minus 0.01 at G1, 1.193 plus or minus 0.01 at G5, 1.192 plus or minus 0.01 at G10, and 1.203 plus or minus 0.01 at G20. T values are 15.66 plus or minus 0.25 at G1, 15.34 plus or minus 0.25 at G5, 15.52 plus or minus 0.21 at G10, and 15.87 plus or minus 0.21 at G20. Each generation column also includes a parenthetical value: 42 for G1, 45 for G5, 43 for G10, and 47 for G20.
Note: G generation; the means followed by different small letters within the same row are comparisons among different generations (P < 0.05, paired bootstrap test).
Age-stage-specific population structure curves (pxj) of sequential generations (G1–G20) of Amblyseius swirskii reared on Carpoglyphus lactis.
Figure 3 Long description
Four line graphs labeled G1, G5, G10 and G20. The horizontal axis label is Age day, with values 0, 2, 4, 6, 8, 10. The vertical axis label is Age stage specific population structure p subscript x j, with values 0, 0.2, 0.4, 0.6, 0.8, 1. A legend lists Egg, Larva, Protonymph, Deutonymph, shown with different line styles. G1: Egg starts near (0, 1) and declines to near (2, 0). Larva forms a hump between about age 1 and 4 with a peak near age 2 to 3 around 0.5. Protonymph forms a hump between about age 2 and 5 with a peak near age 3 to 4 around 0.5. Deutonymph forms a wider hump from about age 3 to 9 with a peak near age 6 around 0.9. G5: Egg starts near (0, 1) and declines to near (2, 0). Larva forms a hump between about age 1 and 4 with a peak near age 2 to 3 around 0.5. Protonymph forms a hump between about age 2 and 5 with a peak near age 3 to 4 around 0.5. Deutonymph forms a wider hump from about age 3 to 9 with a peak near age 6 around 0.85. G10: Egg starts near (0, 1) and declines to near (2, 0). Larva forms a hump between about age 1 and 4 with a peak near age 2 to 3 around 0.5. Protonymph forms a hump between about age 2 and 5 with a peak near age 3 to 4 around 0.5. Deutonymph forms a wider hump from about age 3 to 9 with a peak near age 6 around 0.9. G20: Egg starts near (0, 1) and declines to near (2, 0). Larva forms a hump between about age 1 and 4 with a peak near age 2 to 3 around 0.4. Protonymph forms a hump between about age 2 and 5 with a peak near age 3 to 4 around 0.4. Deutonymph forms a wider hump from about age 3 to 9 with a peak near age 6 around 0.8. The image B showing four line graphs labeled G1, G5, G10 and G20. The horizontal axis label is Age day, with values 0, 5, 10, 15, 20, 25, 30, 35, 40. The vertical axis label is l subscript x, with values 0, 0.2, 0.4, 0.6, 0.8, 1. A legend lists Female and Male, shown with different line styles. G1: Female rises from near (5, 0) to about (8, 0.6), stays near 0.6 until about age 27, then declines to near (33, 0). Male rises from near (5, 0) to about (8, 0.35), stays near 0.35 until about age 24 to 25, then declines to near (33, 0). G5: Female rises from near (6, 0) to about (9, 0.45), stays near 0.45 until about age 25, then declines to near (33, 0). Male rises from near (6, 0) to about (9, 0.45), stays near 0.45 until about age 24 to 25, then declines to near (33, 0). G10: Female rises from near (6, 0) to about (9, 0.55), stays near 0.55 until about age 27, then declines to near (34, 0). Male rises from near (6, 0) to about (9, 0.4), stays near 0.4 until about age 26 to 27, then declines to near (34, 0). G20: Female rises from near (6, 0) to about (9, 0.6), stays near 0.6 until about age 30, then declines to near (34, 0). Male rises from near (6, 0) to about (9, 0.35), stays near 0.35 until about age 27 to 28, then declines to near (34, 0).
Age-specific survivorship (lx), age-specific fecundity (mx), and age-stage-specific fecundity (fxj) of sequential generations (G1–G20) of Amblyseius swirskii reared on Carpoglyphus lactis.
Figure 4 Long description
A line graph labeled, G1. The horizontal axis is labeled, Age day, with a range from 0 to 40. The left vertical axis is labeled, Survivorship lx, with a range from 0 to 1. The right vertical axis is labeled, Fecundity, with a range from 0 to 3.5. A legend shows three series: lx as a solid line, fxj as a dotted line and mx as a dashed line. Series lx coordinate pairs: (0, 1), (25, 1), (30, 0.8), (33, 0.2), (35, 0). Series fxj coordinate pairs: (10, 0), (15, 3.0), (20, 1.5), (25, 1.0), (30, 0.2). Series mx coordinate pairs: (10, 0), (15, 1.5), (20, 1.2), (25, 0.8), (30, 0.1). The image B showing a line graph labeled, G5. The horizontal axis is labeled, Age day, with a range from 0 to 40. The left vertical axis is labeled, Survivorship lx, with a range from 0 to 1. The right vertical axis is labeled, Fecundity, with a range from 0 to 3. A legend shows three series: lx as a solid line, fxj as a dotted line and mx as a dashed line. Series lx coordinate pairs: (0, 1), (25, 1), (30, 0.7), (33, 0.2), (35, 0). Series fxj coordinate pairs: (8, 0), (10, 2.5), (20, 2.0), (25, 1.0), (30, 0.2). Series mx coordinate pairs: (8, 0), (10, 1.2), (20, 1.0), (25, 0.6), (30, 0.1). The image C showing a line graph labeled, G10. The horizontal axis is labeled, Age day, with a range from 0 to 40. The left vertical axis is labeled, Survivorship lx, with a range from 0 to 1. The right vertical axis is labeled, Fecundity, with a range from 0 to 2.5. A legend shows three series: lx as a solid line, fxj as a dotted line and mx as a dashed line. Series lx coordinate pairs: (0, 1), (25, 1), (30, 0.6), (33, 0.2), (35, 0). Series fxj coordinate pairs: (8, 0), (10, 2.2), (20, 1.5), (25, 0.8), (30, 0.2). Series mx coordinate pairs: (8, 0), (10, 1.2), (20, 0.9), (25, 0.5), (30, 0.1). The image D showing a line graph labeled, G20. The horizontal axis is labeled, Age day, with a range from 0 to 40. The left vertical axis is labeled, Survivorship lx, with a range from 0 to 1. The right vertical axis is labeled, Fecundity, with a range from 0 to 3.5. A legend shows three series: lx as a solid line, fxj as a dotted line and mx as a dashed line. Series lx coordinate pairs: (0, 1), (25, 1), (30, 0.7), (33, 0.2), (35, 0). Series fxj coordinate pairs: (8, 0), (12, 2.0), (16, 3.2), (20, 1.5), (30, 0.2). Series mx coordinate pairs: (8, 0), (12, 1.2), (16, 1.6), (20, 1.0), (30, 0.1).
Demographic responses of A. swirskii over successive generations on T. putrescentiae
Over 20 generations of rearing A. swirskii on T. putrescentiae enriched with vitamins B, C, and E, the predator maintained its ability to develop and reproduce across generations. Immature survival showed a significant increase between the first and subsequent generations, rising from 80% in G1 to a consistent range of 90%–95% in later generations (P < 0.05), while total pre-adult duration significantly declined from 7.94 days in G1 to 6.37 days in G20 (P < 0.05), primarily due to a shortened deutonymphal stage. Adult longevity remained consistent across cohorts (P > 0.05), averaging approximately 31.6–31.8 days for females and 36.6–40.1 days for males. Fecundity increased slightly over generations but did not differ significantly (P > 0.05), reaching a maximum of 26.90 eggs/female in G20. Notably, TPOP declined significantly from 10.60 days in G1 to 8.90 days in G20 (P < 0.05), suggesting a trend toward earlier reproductive onset in later generations (table 5). Population growth indices followed a similarly stable trend. The net reproductive rate (R 0), intrinsic rate of increase (r), and finite rate of increase (λ) did not differ significantly across generations (P > 0.05), with r ranging from 0.140 to 0.152 and λ between 1.151 and 1.164 (table 6). However, the mean generation time (T) decreased significantly from 18.32 days in G1 to 16.96 days in G20 (P 0.05).
Long-term effects of feeding Amblyseius swirskii on Tyrophagus putrescentiae fed with wheat bran + baker’s yeast + vitamin mixture (B complex, C, and E) on the duration of different life stages (days), fecundity (eggs/female) and immature survival (%) (mean ± SE)
Table 5 Long description
Parameters are reported for generations G1, G5, G10, and G20 as mean plus or minus standard error, with a sample size shown in parentheses under each row. Egg duration is 1.96 days in G1, 1.98 in G5, 2.00 in G10, and 1.91 in G20, with sample sizes 45, 48, 44, and 43. Larva duration is 1.02 days in G1 and 1.00 days in G5, G10, and G20, with sample sizes 45, 46, 40, and 44; protonymph duration is 1.00 day for all generations, with sample sizes 38, 44, 39, and 41. Deutonymph duration is 3.94 days in G1, 2.72 in G5, 2.77 in G10, and 2.49 in G20, with sample sizes 36, 43, 40, and 41; pre adult duration is 7.94, 6.60, 6.78, and 6.37 days with the same sample sizes. Immature survival rate is 0.80 in G1, 0.90 in G5, 0.91 in G10, and 0.95 in G20, with sample sizes 45, 48, 44, and 43. Male longevity is 36.27, 35.91, 36.50, and 36.38 days with sample sizes 11, 22, 18, and 21; female longevity is 40.92, 40.81, 40.09, and 40.15 days with sample sizes 25, 21, 22, and 20; adult longevity is 31.56, 31.70, 31.70, and 31.85 days with sample sizes 36, 43, 40, and 41. Total lifespan is 32.44, 34.85, 35.39, and 36.65 days with sample sizes 45, 48, 44, and 43. APOP is 2.20, 2.00, 2.09, and 2.00 days with sample sizes 25, 21, 22, and 20; TPOP is 10.60, 9.10, 9.14, and 8.90 days with the same sample sizes. Oviposition days are 18.56, 20.33, 20.64, and 21.35 days with sample sizes 25, 21, 22, and 20, and fecundity is 23.72, 26.24, 26.09, and 26.90 eggs per female with the same sample sizes; letter markers appear after means within each row.
Note: G, generation, APOP adult pre-oviposition period, TPOP total pre-oviposition period (from egg to first oviposition). The means followed by different small letters within the same row are comparisons among different generations (P < 0.05, paired bootstrap test).
Generation-dependent population growth parameters (mean ± SE) of Amblyseius swirskii reared on Tyrophagus putrescentiae fed by wheat bran + baker’s yeast + vitamin mixture (B complex, C, and E)
Table 6 Long description
Population growth parameters are reported as mean plus or minus standard error for four generations labeled G1, G5, G10, and G20. Gross reproductive rate, eggs per individual, is 20.16 plus or minus 2.29 with letter a at G1, 14.88 plus or minus 2.18 with letter a at G5, 15.42 plus or minus 2.17 with letter a at G10, and 14.10 plus or minus 2.20 with letter a at G20; sample sizes shown beneath are 45, 45, 42, and 43. Net reproductive rate, eggs per individual, is 13.18 plus or minus 1.92 with letter a at G1, 11.48 plus or minus 1.94 with letter a at G5, 13.05 plus or minus 2.05 with letter a at G10, and 12.51 plus or minus 2.11 with letter a at G20; sample sizes are 45, 37, 42, and 43. Intrinsic rate of increase, per day, is 0.141 plus or minus 0.01 with letter a at G1, 0.140 plus or minus 0.01 with letter a at G5, 0.152 plus or minus 0.01 with letter a at G10, and 0.149 plus or minus 0.01 with letter a at G20; sample sizes are 45, 37, 42, and 43. Finite rate of increase, per day, is 1.151 plus or minus 0.01 with letter a at G1, 1.151 plus or minus 0.01 with letter a at G5, 1.164 plus or minus 0.01 with letter a at G10, and 1.160 plus or minus 0.01 with letter a at G20; sample sizes are 45, 37, 42, and 43. Mean generation time, days, is 18.32 plus or minus 0.25 with letter a at G1, 17.38 plus or minus 0.26 with letters a and b at G5, 16.90 plus or minus 0.45 with letter b at G10, and 16.96 plus or minus 0.21 with letter b at G20; sample sizes are 45, 37, 42, and 43.
Note: G, generation; the means followed by different small letters within the same row are comparisons among different generations (P < 0.05, paired bootstrap test).
The age-stage-specific reproductive and survival curves remained largely consistent across generations, with only subtle shifts in peak fecundity timing and overlap between developmental stages. These curves illustrate that the reproductive window of A. swirskii was maintained over time, and that the general shape and timing of population structure did not drastically change, indicating demographic stability during long-term rearing. Age-stage structure (age-stage-specific population structure curves) (pxj) demonstrated consistent population distribution patterns across generations, with only minimal variation in the timing and magnitude of stage overlaps (fig. 5). Likewise, fig. 6 shows that age-specific survivorship (lx), age-specific fecundity (mx), and age-stage-specific fecundity (fxj) remained largely stable throughout generations G1–G20. These curves indicate that both the timing and intensity of reproductive output and survival probabilities were maintained. Collectively, these findings indicate that T. putrescentiae supplemented with a vitamin mixture supports stable demographic performance of A. swirskii over extended rearing cycles. However, the absence of major improvements across generations also suggests that transgenerational accumulation of dietary vitamins did not enhance predator fitness over time.
Age-stage-specific population structure curves (pxj) of sequential generations (G1–G20) of Amblyseius swirskii reared on Tyrophagus putrescentiae.
Figure 5 Long description
Four line graphs labeled G1, G5, G10 and G20. The horizontal axis label is, Age day, with a range from 0 to 10. The vertical axis label is, Age stage specific population structure l x, with a range from 0 to 1. G1: Four curves are shown with a legend listing, Egg, Larva, Protonymph, Deutonymph. Egg starts at 1 at age 0 and decreases to 0 by about age 2. Larva rises from 0 to about 0.5 near age 2 and decreases to 0 by about age 4. Protonymph rises to about 0.5 near age 3 and decreases to 0 by about age 5. Deutonymph rises to about 0.8 near age 6 and decreases to 0 by about age 10. G5: Egg starts at 1 at age 0 and decreases to 0 by about age 2. Larva rises to about 0.4 near age 2 and decreases to 0 by about age 4. Protonymph rises to about 0.35 near age 3 and decreases to 0 by about age 5. Deutonymph rises to about 0.75 near age 5 and decreases to 0 by about age 8. G10: Egg starts at 1 at age 0 and decreases to 0 by about age 2. Larva rises to about 0.4 near age 2 and decreases to 0 by about age 4. Protonymph rises to about 0.35 near age 3 and decreases to 0 by about age 5. Deutonymph rises to about 0.8 near age 6 and decreases to 0 by about age 10. G20: Egg starts at 1 at age 0 and decreases to 0 by about age 2. Larva rises to about 0.4 near age 2 and decreases to 0 by about age 4. Protonymph rises to about 0.35 near age 3 and decreases to 0 by about age 5. Deutonymph rises to about 0.75 near age 5 and decreases to 0 by about age 9. The image B showing four line graphs labeled G1, G5, G10 and G20. The horizontal axis has a range from 0 to 60. The vertical axis has a range from 0 to 1. A legend lists, Female, Male. G1: Female rises from 0 to about 0.55 near age 10, stays near 0.55 until about age 30, then decreases to 0 by about age 50. Male rises from 0 to about 0.25 near age 10, stays near 0.25 until about age 30, then decreases to 0 by about age 45. G5: Female rises from 0 to about 0.45 near age 10, stays near 0.45 until about age 30, then decreases to 0 by about age 45. Male rises from 0 to about 0.45 near age 10, stays near 0.45 until about age 30, then decreases to 0 by about age 40. G10: Female rises from 0 to about 0.5 near age 10, stays near 0.5 until about age 35, then decreases to 0 by about age 45. Male rises from 0 to about 0.4 near age 10, stays near 0.4 until about age 35, then decreases to 0 by about age 42. G20: Female rises from 0 to about 0.5 near age 10, stays near 0.5 until about age 35, then decreases to 0 by about age 45. Male rises from 0 to about 0.5 near age 10, stays near 0.5 until about age 35, then decreases to 0 by about age 42.
Age-specific survivorship (lx), age-specific fecundity (mx), and age-stage-specific fecundity (fxj) of sequential generations (G1–G20) of Amblyseius swirskii reared on Tyrophagus putrescentiae.
Figure 6 Long description
Multi-line graph labeled G1. The horizontal axis is Age day, from 0 to 60. The left vertical axis is Survivorship lx, from 0 to 1. The right vertical axis is Fecundity, from 0 to 2. The legend shows three line styles: lx as a solid line, fxj as a dotted line and mx as a dashed line. The solid lx line stays near 1 from about age 0 to the mid 30s, then drops steeply to near 0 by the mid to late 40s. The dotted fxj line rises from near 0 around age 10, shows repeated peaks and dips between about ages 10 and 40, then approaches near 0 by about age 45, with a later isolated spike near the mid 50s. The dashed mx line rises from near 0 around age 10, stays below the dotted fxj line with smaller peaks between about ages 10 and 40, then approaches near 0 by about age 45. Multi-line graph labeled G5. The horizontal axis is Age day, from 0 to 60. The left vertical axis is Survivorship lx, from 0 to 1. The right vertical axis is Fecundity, from 0 to 2. The legend shows lx as a solid line, fxj as a dotted line and mx as a dashed line. The solid lx line stays near 1 through the 30s, then declines to near 0 by the mid to late 40s. The dotted fxj line begins near age 10, reaches a high peak shortly after, then shows multiple smaller peaks and dips through about ages 15 to 40 and approaches near 0 by about age 45, with a later isolated spike near the mid 50s. The dashed mx line begins near age 10, peaks lower than the dotted fxj line, then declines with smaller fluctuations and approaches near 0 by about age 45. Multi-line graph labeled G10. The horizontal axis is Age day, from 0 to 60. The left vertical axis is Survivorship lx, from 0 to 1. The right vertical axis is Fecundity, from 0 to 2. The solid lx line stays near 1 through the 30s, then drops to near 0 by the mid 40s. The dotted fxj line rises from near 0 around age 10, reaches a high peak shortly after, then declines with smaller peaks and dips through about ages 15 to 40, approaching near 0 by about age 45. The dashed mx line rises from near 0 around age 10, remains below the dotted fxj line and declines with smaller fluctuations toward near 0 by about age 45. Multi-line graph labeled G20. The horizontal axis is Age day, from 0 to 60. The left vertical axis is Survivorship lx, from 0 to 1. The right vertical axis is Fecundity, from 0 to 2. The solid lx line stays near 1 through the 30s, then drops steeply to near 0 by the mid 40s. The dotted fxj line rises from near 0 around age 10, reaches a high peak shortly after, then declines with smaller peaks and dips through about ages 15 to 40, approaching near 0 by about age 45. The dashed mx line rises from near 0 around age 10, stays below the dotted fxj line and declines with smaller fluctuations toward near 0 by about age 45.
Discussion
This study demonstrated that the route of vitamin delivery – direct versus prey-mediated – has a profound impact on the developmental success and demographic performance of A. swirskii. When the predator was directly fed a dry diet enriched solely with vitamins B, C, and E, fewer than 10% of individuals completed development, and none reproduced, indicating acute dietary inadequacy likely due to the absence of prey-mediated nutrient transformation. Although an effect of vitamin concentration cannot be completely excluded, the successful performance of A. swirskii on the same vitamin formulation after supplementation with mixed pollen suggests that the mode of nutrient delivery and overall dietary matrix were more influential than vitamin concentration alone. However, when the same vitamin-enriched formulation was provided indirectly through two astigmatid prey species (C. lactis and T. putrescentiae), both of which had consumed the fortified diet for three generations, A. swirskii not only completed development (Jahanbazi et al., Reference Jahanbazi, Zibaee and Fathipour2025b, Reference Jahanbazi, Zibaee and Fathipour2026) but also maintained demographic stability across 20 successive generations, even when the intermediary prey species was of suboptimal quality. This contrast underscores the critical role of intermediate trophic processing in rendering micronutrients bioavailable or detoxified for higher-order consumers. There is growing evidence that the physiological impact of dietary vitamins on predatory mites is not universally beneficial and can vary based on formulation and bioavailability. Dicke et al. (Reference Dicke, de Jong, Alers, Stelder, Wunderink and Post1989) showed that specific micronutrients like carotenoids affect developmental and behavioural traits, while Khanamani et al. (Reference Khanamani, Fathipour, Talebi and Mehrabadi2017a) found that a capsule-based vitamin diet failed to sustain development, possibly due to limited digestibility or imbalanced nutrient profiles; yet when incorporated into prey metabolism, their negative impacts may be mitigated or even converted into beneficial outputs. The observed failure of direct vitamin supplementation, despite the same composition yielding robust results via prey transfer, suggests that A. swirskii may lack the enzymatic or microbial capacity to safely process certain vitamin forms in isolation. These findings highlight the importance of evaluating nutritional strategies not merely based on chemical composition, but within ecologically relevant trophic frameworks that consider metabolic compatibility and nutrient transformation.
When A. swirskii was directly provided with a dry diet supplemented with vitamins B complex, C, and E – composed only of wheat bran, yeast, and vitamin mix – fewer than 10% of individuals reached adulthood, and no oviposition occurred. This stark failure parallels the results of Khanamani et al. (Reference Khanamani, Fathipour, Talebi and Mehrabadi2017a), where N. californicus feeding directly on a multivitamin-capsule enriched diet (AD9) showed complete pre-adult mortality, while the vitamin-syrup treatment (AD10) supported development (immature survival ≈76%). The divergent outcomes underscore that the physicochemical form and bioavailability of the vitamin supplement critically influence predator viability: water-soluble syrups offer superior dispersion and reduced toxicity compared to encapsulated forms that may carry poorly soluble or disruptive fillers. Given that A. swirskii successfully completed development when pollen was present with the same vitamin mixture (in Diet 4), it is unlikely that feeding failure per se was the limiting factor. Instead, these observations suggest either impaired metabolic assimilation of vitamin compounds or sublethal toxicity from concentrated or improperly stabilised vitamin forms in the dry diet. According to the concept of trophic nutrient processing, vitamins ingested via prey are transformed into biochemically compatible compounds, whereas direct intake may result in unbalanced nutrient influx that disrupts endocrine or reproductive pathways – explaining the complete lack of reproduction observed. This interpretation aligns with previous findings showing that many insects rely on trophically mediated or microbially modulated vitamin acquisition to meet physiological demands, especially for B-group vitamins that cannot be synthesised endogenously (Douglas, Reference Douglas2017). Overall, these findings highlight that not only ‘what’ is delivered, but also ‘how’ it is delivered, fundamentally shapes demographic outcomes in artificial predator rearing systems.
The consistent demographic performance of A. swirskii over 20 generations on a dry diet enriched with both vitamin mix (B complex, C, and E) and mixed pollen (corn and bee-collected) suggests that the addition of pollen may have contributed to overcoming the developmental and reproductive limitations observed with vitamin supplementation alone. This interpretation is consistent with our previous study, in which a mixed-pollen diet alone supported favourable demographic performance of A. swirskii during first-generation evaluation (Jahanbazi et al., Reference Jahanbazi, Zibaee and Fathipour2025a), indicating that mixed pollen itself represents a suitable nutritional resource for this predator. The two pollen types used in this study are likely to have offered a complementary nutritional profile that addressed both the energetic and reproductive needs of the predator. Corn pollen is relatively rich in protein, amino acids, and simple carbohydrates like sucrose, supporting predator metabolism and development. Bee-collected pollen adds glucose, fructose, vitamins, minerals, and potentially beneficial microbiota from diverse floral sources, enhancing physiological performance. Additionally, the thin and digestible exine of these pollens, especially maize, facilitates effective ingestion by A. swirskii, as shown in previous studies (Khanamani et al., Reference Khanamani, Fathipour, Talebi and Mehrabadi2017b). The stability in reproductive parameters across generations, including fecundity and intrinsic rate of increase (r), further indicates that the combined pollen sources supplied a balanced and sustainable nutrient input, thereby supporting long-term colony maintenance. Furthermore, the reproductive consistency observed, despite the presence of vitamins in the mix, suggests that potential toxicity or metabolic interference of isolated vitamins may have been mitigated by the nutritional buffering effect of pollen. This aligns with ecological observations where generalist predators thrive better on diverse natural diets than on artificial or chemically defined supplements alone (Labbé et al., Reference Labbé, Gagnier, Kostic and Shipp2018). These findings indicate that direct supplementation of vitamins alone was insufficient to support development and reproduction in A. swirskii, whereas their combination with digestible, nutrient-rich pollen proved essential for sustaining demographic performance across generations.
Sustained demographic performance of A. swirskii across 20 generations when fed in C. lactis enriched with wheat bran, yeast, and vitamins suggests more than mere nutritional adequacy – it points to a stable and compatible trophic relationship. The consistent immature survival rates (above 90%) and unchanged developmental durations imply that neither sublethal toxicity nor digestive constraints limited prey utilisation over time. Interestingly, the slight numerical increases observed in adult longevity and oviposition duration over generations, particularly in females, may reflect subtle physiological adjustment to prolonged dietary conditions rather than demographic deterioration. Although these differences were not statistically significant, they are consistent with the overall stability of life-history traits observed across generations and provide no evidence of cumulative negative effects associated with long-term consumption of vitamin-enriched prey. While intrinsic rate of increase (r) remained stable, the rising net reproductive rate (R 0) and lifespan hint at possible fine-tuning of energy allocation strategies under long-term feeding conditions. Unlike patterns observed in other natural enemies where prolonged exposure to artificial prey often leads to performance decline or metabolic cost (Sadat et al., Reference Sadat, Nazari, Jafari and Karahroudi2021), the absence of such deterioration here underscores the unique compatibility of C. lactis, when optimally provisioned, with A. swirskii’s nutritional physiology. Such resilience across generations suggests that the biochemical composition of this prey may buffer the predator against generational bottlenecks commonly reported in mass-rearing systems. Overall, the results indicate that long-term feeding of A. swirskii on C. lactis reared on a vitamin-enriched diet did not lead to any measurable decline in demographic traits over 20 generations.
Continuous exposure of A. swirskii to T. putrescentiae reared on a vitamin-enriched diet over 20 generations revealed a stable demographic pattern, with early improvements in juvenile survival and developmental timing that plateaued in later generations. The reduction in pre-adult duration and earlier onset of reproduction suggest physiological adjustments, likely mediated by the prey’s nutritional profile shaped by dietary supplementation. Despite the predator’s ability to sustain development and reproduction over time, no meaningful enhancement in fecundity or growth indices was observed, indicating a demographic ceiling. Given that T. putrescentiae is generally considered a suboptimal prey (Jahanbazi et al., Reference Jahanbazi, Zibaee and Fathipour2026), these findings imply that vitamin supplementation improved prey quality just enough to maintain predator viability, but not to elevate it beyond its inherent trophic limitations. Thus, although indirect provisioning of vitamins through this prey did not impair long-term performance, it was insufficient to transform T. putrescentiae into a high-quality food source for sustained rearing.
Although both C. lactis and T. putrescentiae supported the long-term development of A. swirskii when enriched with a vitamin mix, their demographic outcomes diverged – highlighting the modulatory role of prey identity in mediating the effects of micronutrient supplementation. The superior reproductive output and faster generation turnover observed on vitamin-fed C. lactis suggest a higher capacity of this prey to physiologically incorporate and transfer vitamin-derived benefits to the predator. This may be attributed to species-specific digestive efficiency, nutrient assimilation, or metabolic flexibility. In contrast, T. putrescentiae, despite vitamin enrichment, appeared to act merely as a passive carrier, buffering negative effects but failing to elevate predator performance beyond baseline. These findings underscore the critical interplay between prey nutritional physiology and dietary composition in optimising factitious food chains, reinforcing earlier reports that identified C. lactis as a superior factitious prey for A. swirskii in terms of both developmental rate and reproductive efficiency (Ji et al., Reference Ji, Zhang, Lin, Chen, Sun and Saito2015; San et al., Reference San, Tuda, Nakahira and Takagi2020). The minor shifts observed in the age-stage and reproductive curves across generations were consistent with the statistical differences detected in developmental duration and reproductive timing rather than indicating progressive demographic deterioration. Likewise, the greater fecundity peaks observed in C. lactis reflected the higher nutritional suitability of this prey relative to T. putrescentiae and the supplemented dry diet, whereas the overlap among developmental stages represented the natural age-stage variability inherent to the age-stage, two-sex life table approach under standardised environmental conditions.
The present study demonstrates that the biological response of A. swirskii to vitamin supplementation depends strongly on the route through which micronutrients are introduced into the feeding system. Direct supplementation through a vitamin-enriched dry diet alone failed to support normal development and reproduction, whereas the addition of pollen restored demographic performance and enabled population persistence across generations. In contrast, indirect vitamin delivery through prey mites supported stable long-term population performance, even when the prey species was considered nutritionally suboptimal. These findings suggest that trophic context and dietary complexity may substantially influence how micronutrients are utilised within predator rearing systems. The results further indicate that improvements in artificial or factitious diets cannot be evaluated solely based on nutrient presence, but should also consider nutrient integration within the broader feeding network. While the underlying physiological mechanisms remain to be clarified, the observed patterns highlight the importance of prey-mediated nutrient transfer in maintaining demographic stability in predatory mites. Overall, this study provides a practical and conceptual framework for future development of nutritionally optimised rearing systems for biological control agents. Further research integrating biochemical and physiological analyses would help clarify the mechanisms underlying these trophic effects and improve the predictability of micronutrient-based diet design.
Author contributions
Marziye Jahanbazi: Writing – original draft, Software, Methodology, Investigation, Data curation, Conceptualisation. Arash Zibaee: Writing – review & editing, Validation, Resources, Methodology, Conceptualisation. Yaghoub Fathipour: Writing – review & editing, Validation, Supervision, Project administration, Methodology, Funding acquisition, Data curation, Conceptualisation.
Financial support
We are extremely grateful to Tarbiat Modares University, Tehran, Iran, for their generous support and funding of this study.
Competing interests
The authors have no conflict of interest to declare. This manuscript has benefited from AI-based language enhancement tools to improve its English language quality.
