INTRODUCTION
Jasus edwardsii (Hutton, 1875) and Jasus paulensis (Heller, 1862) are commercially fished palinurid spiny lobster. Jasus edwardii are broadly distributed throughout New Zealand and south-eastern Australia, south of about 30°S (Phillips, Reference Phillips2006), whereas, Jasus paulensis are confined to the isolated islands of Amsterdam and the Saint Paul Islands, as well as nearby seamounts in the southern Indian Ocean (Booth, Reference Booth and Phillips2006).
The total catch of Jasus edwardsii across Australia and New Zealand is approximately 5500 tonnes, while annual catches of Jasus paulensis range between 300 and 400 tonnes. Both species are captured using baited traps.
The reproductive morphology in each species follows the general dioecious decapod pattern of dorsally positioned paired ovaries or testes, leading via paired oviducts to reproductive gonopores on the coxopodite at the base of the third pair of pereiopods in females and the fifth pair in males (Meglitsch, Reference Meglitsch1967). The male uses the gonopore as the sperm transfer organ to the female external sternal region, while the female gonopore is used for egg extrusion. In addition, the fifth pereiopod in females terminates in a specialized pincer used to groom the setae and manipulate the egg mass.
This paper reports on abnormal gonopore and pincer characteristics in both Jasus edwardsii and Jasus paulensis, and discusses the findings in relation to rare cases of gynandromorphism in crustacean species.
MATERIALS AND METHODS
The individuals described here were collected as part of a catch sampling program, which is broadly similar in both the Jasus edwardsii and Jasus paulensis fisheries. The primary aim of the programme is to attain data to support routine stock assessments undertaken in each region. It involves scientific observers undertaking trips on-board commercial vessels, where data on numbers, length, sex ratios and the reproductive condition of females are recorded from some or all of the pots hauled on a daily basis. These programs have been running for over 20 years and involve the handling and inspection of animals for recording data or inserting tags. Photographs were collected where individuals were observed with unusual traits.
RESULTS
Jasus edwardsii
Of the ~700,000 lobsters sampled in South Australia, only one individual was recorded as having the reproductive morphological characteristics shown in Figure 1A. In addition to the normal pair of gonopores at the base of the third pair of pereiopods, a pair of gonopores were observed on the coxopodites of the fourth pair of pereiopods.
Specimens of Jasus edwardsii exhibiting abnormal morphological reproductive characteristics. Additional pair of gonopores on the fourth pair of pereiopods (A) and specialized female pincer on a male individual (B). Gonopores and specialized pincer on the right propopodite are marked by arrows.
In Tasmania, the individual shown in Figure 1B reflects the only specimen of its type recorded in the research catch from ~1 million lobsters sampled. On the basis of gonopore location, the lobster was identified as male, but this individual also exhibited the specialized pincer on the right propopodite, normally only observed in females. As in South Australia, it is important to acknowledge that the unusual traits reported here were not formally included in data records and, therefore, it is possible that individuals were encountered but not recorded.
Jasus paulensis
The frequency of abnormal morphological reproductive characteristics appears to be higher in Jasus paulensis compared to that of Jasus edwardsii. From ~17,000 lobsters sampled to date, 14 individuals have exhibited unusual features. The individuals highlighted here were captured in 2014 and 2015. All exhibit abnormal location of gonopores, with examples of general variations provided in Figure 2.
Specimens of Jasus paulensis exhibiting abnormal morphological reproductive characteristics (A–F). Gonopores are marked by arrows.
Abnormalities included male individuals with an additional pair of gonopores on the coxopodites of the third (Figure 2A) and fourth (Figure 2B) pair of pereiopods. In addition, we observed both female (Figure 2C) and male (Figure 2D) individuals with an extra single gonopore on the fourth pereiopod. Finally, male (Figure 2E) and female (Figure 2F) individuals with just a single gonopore were observed. As for Jasus edwardsii, it is important to acknowledge that the unusual traits reported here were not historically included in data records and, therefore, it is possible that individuals were encountered informally but were not recorded.
DISCUSSION
Gynandromorphy is a condition of having both female and male reproductive characteristics that occurs in bilaterally symmetrical organisms such as crustaceans. Although gynandromorphs exhibit characteristics from both sexes, they are generally unable to function as either sex and the condition is often incorrectly reported as hermaphroditism where individuals spend part of their lives as male and another part as female, or spend their entire lives as both sexes. The condition arises from a genetic abnormality in the early stages of mitosis when dividing cells fail to split sex chromosomes typically. Although cases are extremely rare, gynandromorphism has been recorded in a range of crustacean species such as crab (Johnson & Otto, Reference Johnson and Otto1981; Taylor, Reference Taylor1986; Micheli, Reference Micheli1991), shrimp (Belk, Reference Belk1978) and brine shrimp (Bowen & Hanson, Reference Bowen and Hanson1962).
In lobster species, the condition can be expressed under a wide range of morphological variations. As early as the 18th Century, Nicholls (Reference Nicholls1730) described a specimen of the European lobster Homarus gammarus that exhibited bilaterally symmetrical internal and external male and female organs and morphological characteristics. More recent examples of gynandromorphism in lobsters have been described for Homarus gammarus (Gordon, Reference Gordon1957), Homarus americanus (Chace & Moore, Reference Chace and Moore1959) and Nephrops norvegicus (Farmer, Reference Farmer1972). There is variation in expression of gynandromorphy with complete internal and external bilateral separation of the reproductive system into male and female components observed in some cases. In others, it has been reported as a manifestation of various anomalies in the external morphology of the abdomen and its appendages. In particular, the presence of both male and female gonopores, as observed here for Jasus edwardsii and Jasus paulensis, has been periodically observed elsewhere across a range of species (Ridewood, Reference Ridewood1909; Gordon, Reference Gordon1957; Sagi et al., Reference Sagi, Khalaila, Barki, Hulata and Karplus1996). Internal examinations were not undertaken on any of the specimens reported here. However, Ridewood (Reference Ridewood1909) described a female specimen of Homarus gammarus where gonopores were reported on the third right, and the fourth and fifth left pereiopods. Internal examination revealed normal, paired ovaries, with each of the three oviducts leading to the gonopores appearing to be fully functional.
Finally, it is worth noting that, while observations of gynandromorphism are extremely rare in Jasus edwardsii, the condition appears to be more prevalent in the much smaller and isolated population of Jasus paulensis. Sangalang & Jones (Reference Sangalang and Jones1997) also reported on unusually high numbers of gynandromorphic specimens of Homarus americanus from a specific region of Nova Scotia and suggested that some environmental forcing factors may be implicated in the higher prevalence. Whether the higher number of cases reported here from Amsterdam and the Saint Paul Islands are genetically or environmentally driven, remains largely unknown. Overall, given that gynandromorph lobsters are rare and appear to be fully functional, the condition will have negligible impacts on a population level.
ACKNOWLEDGEMENTS
We thank the Terres Australes et Antarctiques Françaises for providing some of the Jasus paulensis images (Eva Biger) and Alan Jones for images of Jasus edwardsii from South Australia.
