Jassaoclairi 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 : 108

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.

Figures

FIGURE 10. Records of Northern Hemisphere species of Jassa that were found in the eastern and/or western North Pacific and seas. Red dot: identification confirmed by specimen examination; green triangle: literature record (Supplementary Table S1) with identification not confirmed but judged likely to be this species; blue x: suspected or known to be on the hull or interior of a boat or ship.

FIGURE 62. Jassa oclairi Conlan, 1990. Holotype, adult male, minor form, 7.7 mm, NMCC 1987-1071; allotype, adult female, 7.6 mm, NMCC 1987-1072; paratypes, juvenile male 1, 7.1 mm, NMCC 1987-1073; juvenile male 2, 4.1 mm, NMCC 1987- 1073 (CMN). Square Bay, Amchitka Island, Alaska (51°27.2ʹN, 170°11.5ʹE), 21 September 1969, C. E. O’Clair, coll., station CT 02069, amongst kelp community dominated by Laminaria longipes on exposed rocky shore in the intertidal zone below MLLW, 1976-30 (CMN). Lateral view: whole body; dorsal view: telson; other views medial. Appendages are of the holotype unless noted otherwise. Scale 0.1 mm. Illustration after Conlan (1990).

FIGURE 63. Jassa oclairi Conlan, 1990. Allotype, adult female, 7.6 mm; paratype, juvenile male 1, 7.1 mm; adult male, major form, 11.6 mm. Snipe Bay, Baranof Island, Alaska (56°25ʹN, 134°57ʹW), 8 July 1975, no further collection data (University of Alaska). All views medial. Scale 0.1 mm.

FIGURE 64. Jassa oclairi Conlan, 1990. Holotype, adult male, minor form, 7.7 mm, NMCC 1987-1071 (CMN). Mouthparts. Frontal view: upper lip; lateral view: maxilla 1; other views medial. Scale 0.1 mm.