Jassafenwicki Conlan, 1990

Conlan, Kathleen E., Desiderato, Andrea & Beermann, Jan, 2021, Jassa (Crustacea: Amphipoda): a new morphological and molecular assessment of the genus, Zootaxa 4939 (1), pp. 1-191 : 147

Jassafenwicki Conlan, 1990

( Table 13 , Fig. 95 )

Diagnosis.

Mandibular palp: article 2, dorsal margin without a fringe of setae.

Maxilla 1: without a seta or setal cluster at the base of the palp article 1.

Gnathopod 1: basis, anterolateral margin with a fringe of short, spine-like setae; carpus without a single or cluster of setae at the anterodistal junction of the propodus.

Gnathopod 2: basis with a row of short, spine-like setae along the anterolateral margin; carpus and propodus, setae on the anterior margin short and simple (setal lengths <20% of the basis width).

Pereopods 5–7: propodus expanded anteroproximally, spines strong and along nearly its full length.

Uropod 1: ventral peduncular spinous process underlying about 1/2 of the longest ramus.

Uropod 3: inner ramus without spines mid-dorsally (with only the single apical spine).

Telson: tip without apical setae (only the usual short setae at each dorsolateral cusp).

Thumbed male:

Antenna 2: with plumose setae on the flagellum and peduncular article 5.

Gnathopod 2: propodus, palmar defining spines absent, the thumb distally squared and originating proximally. The dactyl is strongly expanded close to the junction with the propodus.

Subadult female:

Antenna 2: not plumose on the flagellum and peduncular article 5 (but see Remarks).

Gnathopod 2: propodus, palmsinuous.

Adult female: unknown

Remarks. Only one thumbed male, one subadult female and two juveniles are known from two collections in disparate locations (Cumberland Bay, South Georgia (54°14′S, 36°28′W), and The Snares, New Zealand (48°01′S, 166°32′E )). In both collections J. fenwicki was mixed with J. alonsoae . The appearance of the minor form male and the adult female are unknown. However, the combination of the spine-like fringes on gnathopods 1 and 2, lack of a seta on the gnathopod 1 carpus-propodus anterior junction and the proximally expanded and strongly spinous propodus of pereopods 5–7 are distinctive. Although the subadult female lacked plumose setae on the antenna 2 peduncular article 5, larger individuals may develop them. All other species of Jassa that develop plumose setae in the larger male also develop them in the larger female. It can be reasonably assumed that since the subadult female has a sinuous palm of gnathopod 2, an adult female would as well.

Figures

FIGURE 95. Jassa fenwicki Conlan, 1990. Holotype, adult male, major form, 7.4 mm, AM P34951. Punui Bay, The Snares Islands, New Zealand (48°01′ S, 166°32′ E), 21 January 1977, G. D. Fenwick, coll. (AM).Allotype, subadult female, Cumberland Bay, South Georgia (54°14′ S, 36°28′ W), 9 May 1902, among algae, 1–2 m depth, type no. 3946 from lot no. 3015 (NRM). All views lateral. Setae omitted from the female gnathopod 2 profile. Scale 0.1 mm. Illustration after Conlan (1990).