Paralycaea Claus, 1879

Zeidler, Wolfgang, 2016, A review of the families and genera of the superfamily PLATYSCELOIDEA Bowman & Gruner, 1973 (Crustacea: Amphipoda: Hyperiidea), together with keys to the families, genera and species, Zootaxa 4192 (1), pp. 1-136 : 36

Genus Paralycaea Claus, 1879

( Figs 11–12 )

Paralycaea Claus, 1879: 32 (key), 40.— Gerstaecker 1886: 486.— Claus 1887: 56 (key), 63–64.— Stebbing 1888: 1567.— Schellenberg 1927: 648 (key), 651–652.— Pirlot 1929: 135.— Hurley 1955: 174 (key), 175.— Bowman & Gruner 1973: 42 (key), 43–44.— Zeidler 1978: 21 (key), 25.— Vinogradov et al. 1982: 361 (key), 377–378.— Shih & Chen 1995: 146 (key), 158.— Vinogradov 1999: 1202 (key), 1203.

Type species. Paralycaea gracilis Claus, 1879 by monotypy. Type material could not be found at the MFN or ZMH and is considered lost. However, the description and figures provided by Claus (1879, 1887) readily characterise this genus. The type locality is unknown ( Claus 1879, 1887).

Diagnosis. Body shape robust or globular. Head rounded. Eyes occupying most of head surface, grouped in one field on each side of head. Antennae 1 of males with 1-articulate peduncle; flagellum with large, crescentshaped callynophore, with aesthetascs arranged in one-field brush medially; with two smaller articles inserted on antero-dorsal corner. Antennae 1 of females without peduncle; callynophore narrowly rectangular; with one smaller article inserted terminally. Antennae 2 absent in females. Antennae 2 of males 5-articulate; strongly zigzagged, with most articles folded back on each other; extending anteriorly under head and posteriorly between the gnathopoda and pereopoda to pereonite 2; basal article distinctly inflated, about half or less the length of following article; last two articles sub-equal in length to preceding one; terminal article pointing anteriorly. Mandibular incisor relatively broad, with several teeth; in male orientated more or less parallel to palp. Maxillae 1 very reduced in size, consisting of plate-like lobes, with four rounded teeth distally on medial margin. Maxillae 2 very reduced in size; bi-lobed, with two terminal teeth or robust setae on each lobe. Maxilliped with inner lobes completely fused; medial margin of outer lobes with membranous fringe. Gnathopods 1 & 2 simple. Pereopods 3 & 4 distinctly shorter than pereopods 5 & 6. Pereopod 5; basis about 3 x as wide as merus, non-locking but may overlap with P6; articles 3–7 inserted terminally to basis. Pereopod 6; basis very wide proximally, as wide or less than 5 x as wide as merus, but not operculate, does not overlap, or lock, with opposing pereopod; articles 3–7 inserted sub-terminally on basis; merus with antero-distal corner extended, distinctly overlapping carpus medially. Pereopod 7 reduced in size with basis not particularly enlarged, usually with only 1–3 terminal articles, but sometimes all articles are present. Uropod 1 with articulated exopoda and endopoda. Uropod 2; endopod sometimes fused with peduncle. Uropod 3; endopod fused with peduncle. Rami of all uropoda more-or-less lanceolate, usually with serrated margins.

Species. Paralycaea gracilis Claus, 1879 and P. hoylei Stebbing, 1888 .

Sexual dimorphism. Apart from the morphology of the mandibles and the antennae, no obvious sexual dimorphism could be determined.

Remarks. This genus differs from the other two in the family in that the basis of pereopod 6 lacks a fissure, and opposing pereopods do not seem to overlap. Also, the gnathopoda are simple.

The number of valid species in this genus is contentious. Vinogradov et al. (1982) consider it to be monotypic, but Harbison et al. (1977) argue for the recognition of at least two, if not all, of the three nominal species, viz. P. gracilis Claus, 1879 ; P. newtoniana Bovallius, 1887 and P. hoylei Stebbing, 1888 . Clearly a thorough taxonomic revision is long overdue.

The validity of P. gracilis and P. hoylei was established more recently ( Zeidler 1998), but the status of P. newtoniana is uncertain, as the description given by Bovallius is limited, the type material appears lost, and no figures are available in the literature. It seems to be very similar to P. hoylei , except for pereopod 6, in which the antero-distal corner of the merus does not overlap the carpus, but the two species may yet prove to be synonymous. The specimens mentioned by Harbison et al. (1977) were not available for examination, and until more material becomes available, only two species are currently recognised.

Very little is known about the biology of species. Stephensen (1925) recorded P. gracilis with a medusa, Aglantha (?), but most species seem to be associated with siphonophores, Harbison et al. (1977) having recorded P. gracilis from Agalma clausi , Sulculeolaria chuni and S. monoica ; P. h oy l ei from Nanomia bijuga and S. quadrivalvis , and P. newtoniana from S. chuni , S. monoica and S. quadrivalvis . Gasca et al. (2006) also record P. hoylei from Chelophyes appendiculata .

Paralycaea seems to be a relatively uncommon but widely distributed genus in tropical and temperate regions of the world’s oceans, occurring mainly in near-surface waters.

Figures

FIGURE 11. Paralycaea gracilis Claus, 1879, female (4.6 mm), Tasman Sea, SAMA C 5174; male (3.2 mm), Indian Ocean, off South Africa, SAMA C 5813. A – C, cuticular sculpture, habitus and dorsal view of head of female. Mouthparts from male. Scale bars = 0.5 mm (B, C), 0.2 mm (G 1 & 2), 0.1 mm (A 1 & 2), 0.05 mm (mouthparts).

FIGURE 12. Paralycaea gracilis Claus, 1879, female (4.6 mm), Tasman Sea, SAMA C 5174. Scale bar = 0.2 mm.