Cyllopus Dana, 1853

Zeidler, Wolfgang, 2003, A review of the hyperiidean amphipod superfamily Vibilioidea Bowman and Gruner, 1973 (Crustacea: Amphipoda: Hyperiidea), Zootaxa 280 (1), pp. 1-104 : 82-83

Genus Cyllopus Dana, 1853

Cyllopus Dana, 1853: 989 . — Bate 1862: 305. Gerstaecker 1886: 490. Bovallius 1887b: 555. Stebbing 1888: 1296. Bovallius 1889: 4. Spandl 1927: 174. Barnard 1930: 405–408. Hurley 1955: 129. Hurley 1960a: 111. Vinogradov 1962: 16–17. Bowman & Gruner 1973: 25. Vinogradov et al. 1982: 239. Weigmann­Haass 1983: 2. Vinogradov 1999: 1177.

Type species

Cyllopus magellanicus Dana, 1853 , by monotypy. Type material could not be found at the USNM or in any other major North American museum and is considered lost. However, Cyllopus is a readily recognisable genus.

Diagnosis

The characters of the family are also those of the genus.

Two species.

Sexual dimorphism

As in Vibilia , the sexes of Cyllopus are very similar morphologically. The most reliable character to differentiate them is the relative length of the second antennae. In males antennae 2 are longer than antennae 1 because of the elongation of articles, while in females the antennae are subequal in length. The shape of the callynophore of antennae 1 also differs slightly, tapering gradually in females but in males with a slight proximal bulge. Generally the head of males is slightly larger, and less rounded, with darker, almost black eyes. In females the rami of uropod 2 are narrower and more distinctly denticulate and in males the endopod is distinctly broader than the exopod.

Remarks

Cyllopus is a very distinctive genus somewhat resembling Themisto . Two species are currently recognised ( Weigmann­Haass 1983), both of which are restricted to the colder waters of the southern Hemisphere.

Virtually nothing is known about the biology of either species. The large eyes indicate an active pelagic life­style, but the rounded dactyls of pereopod 7 are like those of Vibilia and, as in Vibilia , may be used to transfer larvae to a gelatinous host ( Laval 1963, 1980). This view is supported by Weigmann­Haass (1983) who first described the larvae of Cyllopus and concluded “due to special morphological similarities … the larvae of both species display a parasitic way of life like Vibilia ”. To what extent adults are parasitic or commensal is not known.

As the genus has been reviewed by Weigmann­Haass (1983) only essential information and synonymies are provided for each species.