INTRODUCTION
Hyperiid amphipods are a group of pelagic crustaceans distributed all around the world; most of them are symbiotically associated with gelatinous animals (medusa, ctenophores, siphonophores and salps) for one portion of their life cycle (Gasca & Haddock, Reference Gasca and Haddock2004). In the near-shore environment, these species are most commonly found in association with true jellyfish (Cnidaria: Scyphozoa), especially during the summer months (Fleming et al., Reference Fleming, Harrod, Griffin, Newton and Houghton2014).
Nine recognized species of Hyperia are currently known: Hyperia bowmani M. Vinogradov, 1976 (found in the eastern equatorial part of the Pacific Ocean); Hyperia crassa Bowman, 1973 (west coast of Africa); Hyperia curticephala Vinogradov & Semenova, Reference Vinogradov and Semenova1985 (Peru to Chile); Hyperia galba (Montagu, 1815) (circumpolar distribution in the Arctic and Atlantic Ocean; Hyperia gaudichaudii Milne Edwards, 1840 (along the southern coasts of Africa, Australia and South America); Hyperia leptura Bowman, 1973 (off Bahía Ballenas, Baja California); Hyperia macrocephala (Dana, 1853) (Antarctic waters); Hyperia medusarum (Müller 1776); and Hyperia spinigera Bovallius, 1889 (worldwide distribution). All of the species in this genus are associated with jellyfish or ctenophorans (as ectoparasites, parasitoids and commensales), and they feed on the residual food of their hosts and eat away their tissues (Vinogradov et al., Reference Vinogradov, Volkov and Semenova1996). Hyperia curticephala has also been cited as a trophic link between jellyfish and fishes, being a primary prey for the palm ruff Seriolella violacea (Riascos et al., Reference Riascos, Vergara, Fajardo, Villegas and Pacheco2012).
Hyperia curticephala was first described by Vinogradov & Semenova (Reference Vinogradov and Semenova1985), from the type locality off Paita (05°04′S 81°07′W) in northern Peru. The only subsequent reports of this species in the Pacific Ocean were made by Oliva et al. (Reference Oliva, Maffet and Laudien2010) and Riascos et al. (Reference Riascos, Vergara, Fajardo, Villegas and Pacheco2012), reporting this species in Mejillones Bay (18°S), Antofagasta Region, Chile. So far, all the records of Hyperia curticephala have been related to the jellyfish Chrysaora plocamia, which reaches comparatively high abundances in shallow water during the summers in northern Chile (Mianzan et al., Reference Mianzan, Quiñones, Palma, Schiariti, Acha, Robinson, Graham, Pitt and Lucas2014).
Here we provide a new record of this species, which extends its current southern distribution by about 443 km beyond its previous range in Mejillones Bay, Antofagasta Region, northern Chile.
MATERIALS AND METHODS
Sampling was carried out during a bloom of the jellyfish Chrysaora plocamia (Lesson, 1830) stranded at beaches in Caldera (27°20′S 70°56′W), Atacama Region, northern Chile, on 22 January 2015. The 43 specimens of Hyperia curticephala were hand-picked from under the bell and the gonads of C. plocamia, together with the parasitic actiniaria Peachia chilensis Carlgren, 1931. The material was frozen and further preserved in 70% ethanol. Specimens were deposited under the accession number MZUC 39615 in the collections of the Museo de Zoología de la Universidad de Concepción, in Concepción, Chile.
RESULTS
SYSTEMATICS
Order AMPHIPODA Latreille, 1816
Suborder HYPERIIDAE Milne Edwards, 1830
Family HYPERIIDAE Dana, 1852
Genus Hyperia Latreille, in Desmarest, 1823
Hyperia curticephala Vinogradov & Semenova, Reference Vinogradov and Semenova1985
(Figure 1A–C)
Hyperia curticephala Vinogradov & Semenova, Reference Vinogradov and Semenova1985. (A) Male specimen in vivo on subumbrellar cavity of Chrysaora plocamia; (B) Detail of (A); (C) Female specimen, lateral view. Scale bars: A, 120 mm; B, 10 mm; C, 5 mm.
Hyperia curticephala Vinogradov & Semenova, Reference Vinogradov and Semenova1985, pp. 140–143, Figures 1 & 2. Vinogradov et al., Reference Vinogradov, Volkov and Semenova1996, pp. 609–610, Figure 1. Vinogradov, Reference Vinogradov and Boltovskoy1999, pp. 1182–1183, Figure 4.94.
Geographical distribution of Hyperia curticephala Vinogradov & Semenova, Reference Vinogradov and Semenova1985 in the Pacific Ocean. Black star indicates type location for the species, off Paita, Peru (Vinogradov & Semenova, Reference Vinogradov and Semenova1985). Black square indicates the only previous records of this species in the Pacific Ocean (Oliva et al., Reference Oliva, Maffet and Laudien2010; Riascos et al., Reference Oliva, Maffet and Laudien2012), the black circle indicates the southernmost record (presented in this study) and the hatched area indicates the known distribution of its host Chrysaora plocamia (Lesson, 1830).
Description: Female
Body length of adult specimens 9 to 12 mm, with a rotund body shape, which is translucent, whitish, with brown-reddish star-shaped chromatophores. Head is noticeably shorter than the first two pereonites, its height is 2.5 times greater than the length; antennal gland cone with a rounded apex. Maxilliped with oval-conical outer blades, medial lobe is relatively longer than the middle of the lateral lobe, tilted forward and densely covered with short bristles. Medial lobe of the maxilliped armed with two closely spaced strong apical spines. Pereon severely swollen, pereopods II–III segments highest, coxal plates are small, with rounded edges, pereopods I–II armed with groups of bristles at the rear of the distal edge; elongated 5th segments expanded distally. Pereopods III–IV with expanded second segment; 2–5th segments with short spines along the back edge; 2nd, 3rd and 5th segments, in addition, armed with bundles of several longer spines in the posterior distal corners. Pereopods V–VII shorter than preceding, in length almost equal to each other, unarmed except for 1–2 spikes in the front distal corner of second segment of pereopod VII; armature of posterior edge of 6th segment of pereopod IV smooth or with very small, indistinct teeth. Article 6 of pereopoda VII unarmed. Claws as in preceding extremities; strong, short and slightly curved. Pleon length does not exceed the total length of pereopod III–VII segments. Edge of epimerons of first pleon segment rounded; rear corners of the distal epimerons of segments II–III of pleon pointed. Urosoma (without uropods) is shorter than II + III segments of pleon. The rounded-triangular peaked telson has a length of half the length of basipodite of uropods III (after Vinogradov & Semenova, Reference Vinogradov and Semenova1985).
Description: Male
Body more narrow, elongated and more pigmented than in females, 8–10 mm in length. Head slightly shorter or equal to the length of pereonites 1–2 combined. The filiform antennae are longer or approximately equal to the length of the body. The structures of the mouthparts and the armament of pereiopods are similar to that of the females. Uropods relatively thin and long (after Vinogradov & Semenova, Reference Vinogradov and Semenova1985).
GEOGRAPHICAL DISTRIBUTION
This species has been previously found along the southern Pacific Ocean, from Paita (05°S), Peru to Mejillones Bay (18°S), Chile (Oliva et al., Reference Oliva, Maffet and Laudien2010) and in the Indian Ocean near the shores of south-eastern Africa and in the South Atlantic, off Namibia (Vinogradov, Reference Vinogradov1988, Reference Vinogradov and Boltovskoy1999; Vinogradov et al., Reference Vinogradov, Volkov and Semenova1996).
REMARKS
A high proportion of the female specimens of Hyperia curticephala were evident in all of the specimens of Chrysaora plocamia examined; a similar trend was also reported by Oliva et al. (Reference Oliva, Maffet and Laudien2010). It is also interesting to note that the cuticle pattern of most of the specimens of H. curticephala imitates the pattern found in the exumbrella of the jellyfish: with brown stars over a translucent background. A strong, positive phototactic response was also observed in all of the collected specimens.
DISCUSSION
Hyperia curticephala is one of two species of the genus Hyperia distributed in Chile (González et al., Reference González, Haye, Balanda and Thiel2008) and one of the few parasitic amphipods in this region. Most of the specimens are mesoparasitic; living in the subumbrella of the jellyfish Chrysaora plocamia (Figure 1B). This species was abundant in most of the examined specimens of C. plocamia; however the majority of the specimens were females, with about 1–3 males per jellyfish. Along with H. curticephala, all the specimens of C. plocamia examined were infested by the parasitic sea anemone Peachia chilensis Carlgren, 1937.
It has been already established that the distribution of hyperiid amphipods is closely related to their association with jellyfishes and other gelatinous organisms (Gasca & Haddock, Reference Gasca and Haddock2004), and so, H. curticephala in particular may be more widespread in Chile or in southern South America, whereas, C. plocamia has been found from Paita, Peru to Puerto Madryn, Argentina (Morandini & Marques, Reference Morandini and Marques2010). The scarcity of records of this amphipod reflects a lack of sampling surveys of pelagic organisms, an artefact consequence of the sampling devices used in local plankton research (Oliva et al., Reference Oliva, Maffet and Laudien2010) or by the paucity of specialists working in the field. In conclusion, the new record extends the known geographical range of H. curticephala to 443 km southwards in the south-eastern Pacific Ocean (Figure 2) and confirms its association with C. plocamia. Further, it would be interesting to know if the Atlantic specimens of C. plocamia also host this particular hyperiid amphipod.
ACKNOWLEDGEMENTS
We thank Jorge A. Pérez Schultheiss (Departamento de Sistemática Animal, Centro de Estudios en Biodiversidad, Osorno, Chile) and Georgy Vinogradov (P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia) for their help with essential literature, and our thanks to Edison Villalobos (Caldera, Chile) for his help in collecting specimens in situ. Two anonymous reviewers are also thanked for their valuable comments and suggestions, which greatly improved our manuscript.
