LYCAEOPSIDAE Chevreux, 1913

Zeidler, Wolfgang, 2004, A review of the hyperiidean amphipod superfamily Lycaeopsoidea Bowman & Gruner, 1973 (Crustacea: Amphipoda: Hyperiidea), Zootaxa 520, pp. 1-18 : 3-4

Family LYCAEOPSIDAE Chevreux, 1913

Diagnosis

Body length up to 6 mm, but usually only 3–4 mm, slender, slightly compressed laterally. Head globular, as long as first three pereonites. Eyes large, occupying most of head surface. Pereonites all separate. Coxae separate from pereonites. Antennae 1 short, slightly longer than half of head in males; less than half of head in females; in male, first flagellar article (callynophore) and 2­articulate peduncle, enlarged forming triangularshaped structure, callynophore with brush of aesthestascs ventrally and anterodorsally on lateral surface, with row of robust setae on anterodorsally on medial surface, remainder of flagellum consists of three slender articles inserted sub­terminally on dorsal margin of callynophore; in females peduncle is 2–3 articulate, callynophore is elongate, tapering with one smaller elongate article forming remainder of flagellum. Antennae 2 inserted on ventral surface of head, just anterior to buccal mass; very short, curved 5­articulate, similar in both sexes. Mandibles with palp in males; without palp in females; palp relatively long with all articles usually fused; molar, spine row and lacina mobilis absent; incisor reduced to small bifid pincer. Maxillae 1 reduced to small, slender single lobe with 3–4 terminal teeth. Maxillae 2 reduced to small, single lobes, slightly curved with rounded bulge medially. Gnathopods and pereopods simple. Pereopod 5 the longest in mature males as a result of extreme elongation of four distal articles; similar to, but shorter than, P 6 in females. Pereopod 6 the longest in females; basis and merus especially broad in males. Pereopod 7 reduced in size, but all articles present. Uropods with articulated endopods and exopods. Telson triangular, sometimes bottle­shaped in males, exceeding peduncle of U 3 in length. Gills on pereonites 5 & 6. Oostegites on pereonites 2–5.

One genus: Lycaeopsis .

Remarks

The family has several unusual characters that distinguish it from all other families of Hyperiidea . The morphology of the first antennae of males is unlike that of any other family. The second antennae are reduced in size, but similar in both sexes. In this respect, males of Lycaeopsis resemble those of Thamneus , whereas males of most other hyperiideans have longer second antennae. The mouthparts are styliform and relatively small and have not previously been described for females ( Figs 1 & 2 ). The mandibular palp, which is absent in females, usually has all articles fused, a character not found in any other family. It is relatively long, filamentous, and projected forward between the second antennae. The mandible itself is reduced, with the only morphological feature being a small, pincerlike structure at the apex, probably all that remains of the incisor. Members of the superfamily Platysceloidea are also noted for having reduced mandibles but all have a recognisable incisor with several teeth. However, the maxillae are like some families of the Platysceloidea, especially the second maxillae, which closely resemble those of the family Platyscelidae . The sexual dimorphism of pereopod 5 is a character not observed in any other family. A reduction in the number of gills on the pereonites is also rare amongst the Hyperiidea .

Prior to this review, it was assumed that the second antennae were absent in females of Lycaeopsis (e.g. Bowman & Gruner 1973, Vinogradov et al. 1982), but second antennae were found in all specimens examined. In both sexes the second antennae are very short, curved medially, and composed of five short articles. Their small size might explain why previous authors thought they were absent in females, but they are no smaller in females than in males, and both Claus (1879) and Stebbing (1888) record females with second antennae of five articles.

Figures

FIGURE 1. Lycaeopsis themistoides, male 4.4 mm, Tasman Sea, SAMA C 5098 (m); ovigerous female 3.1 mm, Indian Ocean, off South Africa, SAMA C 5830 (f). A, lateral view of male. Scale bars = 0.5 mm (A 1 & 2 ­ m), 0.05 mm (remainder).

FIGURE 2. Lycaeopsis themistoides, male 4.4 mm, Tasman Sea, SAMA C 5098. Scale bar = 0.2 mm.