Jassa oclairi Conlan 1990
Creators: name: Conlan, Kathleen E.
name: Desiderato, Andrea
name: Beermann, Jan
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Ischyroceridae
Jassa
Jassa oclairi

description: Jassaoclairi Conlan, 1990
(Table 12, Figs 62–64)
Diagnosis.
Both sexes:
Mandibular palp: article 2, dorsal margin witha 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 only a few short setae distally; carpus with a single or small cluster of long setae at the anterodistal junction of the propodus (setae 40-50% of anterior margin length and slightly lateral).
Gnathopod 2: basis with a row of long plumose setae along the anterolateral margin (setae 75% of article width); carpus and propodus, setae on the anterior margin short and plumose (setal length <basis width).
Pereopods 5–7: propodus not expanded anteriorly.
Uropod 1: ventral peduncular spinous process underlying about 1/3 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: large individuals nearly asetose, without plumose setae on the flagellum and peduncular article 5 (which are present in smaller males).
Gnathopod 2: propodus, palmar defining spines not produced on a ledge, present in small thumbed males but absent in large thumbed males. In minor males, the thumb is distally squared, short relative to body length and located on the distal half of the propodus. The dactyl is centrally toothed on the inner margin. In the major form male, the thumb is distally squared, and originates more centrally on the propodus. The dactyl is expanded close to the junction with the propodus but is not centrally toothed.
Adult female:
Antenna 2: with abundant plumose setae on the flagellum and peduncular article 5.
Gnathopod 2: propodus, palm concave, palmar defining angle acute.
Remarks. Only one major form male was available for study. Although larger in body size than the minor form adult males, its thumb was relatively short (Fig. 63). However, its second antennae were substantially longer than in the juvenile or female and lacked their plumosity on the peduncle article 5 and flagellum. This is the largest of the Northern Hemisphere species of Jassa and also the most plumose, with plumose setae occurring on the antennae 1 and 2, gnathopod 2 and pereopods 5–7. It is only known from Alaska and northern British Columbia (Fig. 10). This is the only Pacific species known to have the dorsal fringe of setae on article 2 of the mandibular palp. It shares this character state with the European J. falcata and J. herdmani. All other species lack this fringe. This is the only Pacific species known to have the dorsal fringe of setae on article 2 of the mandibular palp. It shares this character state with the European J. falcata and J. herdmani. All other species lack this fringe.
description: Published as part of Conlan, Kathleen E., Desiderato, Andrea & Beermann, Jan, 2021, Jassa (Crustacea: Amphipoda): a new morphological and molecular assessment of the genus, pp. 1-191 in Zootaxa 4939 (1) on page 108, DOI: 10.11646/zootaxa.4939.1.1, http://zenodo.org/record/4580622