Jassaborowskyae 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 : 112-114

Jassaborowskyae Conlan, 1990

( Table 12 , Figs 65–66 )

Diagnosis.

Both sexes:

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 without a row of short setae along its length; carpus with a single or small cluster of long setae at the anterodistal junction of the propodus (setae 95% of anterior margin length and slightly lateral).

Gnathopod 2: basis with a row of setae along the anterolateral margin (setae>50% of basis width); carpus and propodus, setae on the anterior margin short and simple (setal length <basis width).

Pereopods 5–7: propodus not expanded anteriorly.

Uropod 1: ventral peduncular spinous process very short, underlying only 10% 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 with plumose setae on the flagellum and peduncular article 5 and lacking long filter setae.

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 acute, short relative to body length and located on the distal half of the propodus. The dactyl is not strongly centrally toothed. In major males, the thumb is distally squared, longer relative to body length and on the proximal half of the propodus. The dactyl is expanded close to the junction with the propodus but is not centrally toothed.

Adult female:

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

Gnathopod 2: propodus, palm concave, palmar defining angle acute.

Remarks. Jassa borowskyae shares the abbreviated process on uropod 1 with two other Northeastern Pacific species, J. myersi and J. shawi while all other species of Jassa have a well developed peduncular process that is 25% to 50% the length of the longest ramus. However, these latter two species lack the diagnostic dense setal fringe on the basis of gnathopod 2 that J. borowskyae possesses. Many more minor than major form adult males were found in the collections of J. borowskyae available for study but there were not enough specimens from a single population to plot the relationship of thumb length or propodus length to body length.

Figures

FIGURE 65. Jassa borowskyae Conlan, 1990. Holotype, adult male, minor form, 4.5 mm, NMCC 1987-1064; allotype, adult female, 5.0 mm, NMCC 1987-1065. Brady’s Beach, Barkley Sound, Vancouver Island, British Columbia, 26 June 1976, E. L. Bousfield, coll., station B5, scrapes of boulders embedded in sand, Phyllospadix, kelp, brown algae, at low water, 1976-157 (CMN). Subadult male, 4.3 mm; adult male, major form, 5.0 mm. Point Grenville, Washington, 22 July 1966, E. L. Bousfield, coll., station W22, scrapes of boulders embedded in sand at low water, 1966-211 (CMN). Lateral views: whole body and uropods; dorsal view: telson; other views medial.Appendages are of the holotype unless noted otherwise. Scale 0.1 mm. Illustration after Conlan (1990).

FIGURE 66. Jassa borowskyae Conlan, 1990. Holotype, adult male, minor form, 4.5 mm, NMCC 1987-1064. Brady’s Beach, Barkley Sound, Vancouver Island, British Columbia, 26 June 1976, E. L. Bousfield, coll., station B5, scrapes of boulders embedded in sand, Phyllospadix, kelp, brown algae, at low water, 1976-157 (CMN). Mouthparts. Frontal view: upper lip; lateral views: maxillae 1 and 2 and maxilliped; other views medial. Scale 0.1 mm.