Ventojassa palauensis, Myers, A. A., 2013

Myers, A. A., 2013, Amphipoda (Crustacea) from Palau, Micronesia: Families Dexaminidae, Eusiridae, Hyalidae, Ischyroceridae, Leucothoidae and Lysianassidae, Zootaxa 3731 (3), pp. 301-323 : 303-306

Ventojassa palauensis sp. nov.

( Figs 2 , 3 )

Ventojassa ventosa Myers, 1985 , 90, fig. 70.

Type material. Male holotype, 1.8 mm. (OUMNH.ZC.2002.24.096) Ngeritaal Pass, from Polycarpa capitosa Sluiter (Ascidiacea: Styelidae ), - 5 m depth; 07°19.223'N, 134°28.271'E; leg. S. De Grave & C. Burras, 20 May 2002.

Etymology. Named after the country of the type locality.

Description. Based on male holotype, 1.8 mm.

Head. Head with lateral lobes moderately produced, rounded; eye round, one third dorsal length of head. Antenna 1 about half body length, articles 1 and 3 subequal in length; accessory flagellum composed of one long article and one vestigial second article; flagellum slightly longer than the third peduncular article; all articles with long, fine setae on the posterior margin. Antenna 2 subequal in length with antenna 1, peduncular articles 4 and 5 subequal, bearing long slender setae on the posterior margin; flagellum a little longer than peduncular article 5.

Pereon. Coxae 1–5 of equal depth. Gnathopod 1 much smaller than gnathopod 2; coxa subtriangular; basis weakly expanded distally; left gnathopod with propodus ovoid, about two thirds length of carpus, lacking a dactylus; right gnathopod propodus a little shorter than the carpus, with concave posterior margin and short, rudimentary, subtrianglar dactylus. Gnathopod 2 coxa broader than deep, basis strongly expanded distally with large anterodistal flange; carpus very short, cup-shaped; propodus enlarged, more than 4 × length of carpus, palm scalloped, with three blunt spines and two robust setae; dactylus strong, slightly overlapping inner face of propodus. Pereopods 3–4 basis weakly expanded, merus weakly expanded, without robust setae on any articles Pereopod 5 basis with large posterior flange, broadest proximally. Pereopod 6 basis with well developed posterior flange, widest medially. Pereopod 7 missing.

Pleon. Epimeron 3, posterodistal margin with small notch bearing a fine seta. Uropod 1 peduncle elongate, nearly twice length of inner ramus, with a strong distoventral spine about one third length of peduncle; inner ramus longer than outer. Uropod 2 peduncle longer than inner ramus and with short distoventral spine about one quarter length of peduncle; inner ramus longer than outer. Uropod 3 peduncle stout, about twice as long as broad, rami short, about half length of peduncle, both rami with a single terminal robust seta, outer ramus with weak serration on outer distal margin. Telson subtriangular, with single seta on each lateral margin.

Female. Unknown.

Remarks. The peculiar, left and right gnathopod 1 of present material is unique amongst ischyrocerids. The possibility exists that this feature is a growth deformity in the single known specimen, although it would be unusual for the gnathopods on both sides to have been affected. Whether this is truly a diagnostic character cannot be ascertained until further material of this species becomes available for study. The following discussion therefore ignores this character.

Ventojassa paluensis sp. nov. resembles Ventojassa ventosa (Barnard, 1962) ; however, it differs from the holotype of Eurystheus ventosa from California, in having the basis of pereopods 6–7 lacking crenulation, in having only one long article on the accessory flagellum and in lacking ‘wire’ setae on the outer ramus of uropod 3. Material described under the name Ventojassa ventosa from Hawaii (Barnard 1970), also resembles present material, but like material from California, also has two long articles on the accessory flagellum and wire setae on the outer ramus of uropod 3. The basis of pereopods 6 and 7 is not precisely figured by Barnard (1970). Specimens of Ventojassa ventosa from Madagascar (Ledoyer 1986), have a single long article on the accessory flagellum and lack crenulations on the basis of pereopods 6–7 and in this respect resemble present material. Materials from California, Hawaii and Madagascar measure between 2.8 and 4.0 mm., significantly larger than present material.

Myers (1985) described specimens from Fiji under the name Ventojassa ventosa . These closely resemble the material described here from Palau. They also were small specimens 1.3–1.5 mm in body length. The only significant difference appears to be the presence of a single wire seta on uropod 3 outer ramus in Fiji specimens. The Fiji and Palau specimens are probably conspecific, but they differ from the Californian type material of Eurystheus ventosa sufficiently to consider them separate species. The crenulated basis of pereopods 6–7 and the two-articulate accessory flagellum, in addition to its large size (4.0 mm in V. ventosa as compared with 1.8 mm in V. palauensis sp. nov.) separate V. ventosa from V. palauensis sp. nov.

Habitat. Amongst ascidians.

Distribution. Known from Fiji and Palau.

Figures

FIGURE 2. Ventojassa palauensis sp. nov., holotype male, Palau.

FIGURE 3. Ventojassa palauensis sp. nov., holotype male, Palau.