Tiron canadense, Just, 2022

Just, Jean, 2022, Tirons of the world: a review of ‘ tironid’ amphipods, description of new genera and species, and establishment of a new subfamily Tironinae Stebbing, 1906 stat. nov. (Crustacea, Synopiidae), Zootaxa 5139 (1), pp. 1-89 : 13-16

Tiron canadense sp. nov.

( Figs 4–5 )

Type fixation. Holotype, ♀.—Here designated.

Etymology. This species is named for Canada.

Material examined. Holotype, ♀ with fully developed oostegites, 10.0 mm. Canada, Vancouver Island , Strait of Georgia, 49ᵒ10’N, 123ᵒ16’W, 40 fv [old Danish measure, here = 75 m], mud, sponges, trawl, Dr. Th. Mortensen’s Pacific Expedition 1914–16, 16 June 1915, NHMD 916107 . (Unique).

Description. Rostrum down curved, acutely pointed. Interantennal lobes rounded with a few small marginal setae on apex. Eyes large oval, accessory eye of 2 separate ocelli.

Mouthparts. Maxilla 1 palp apex with 7 short, acute, denticulate setae, and single elongate, smooth lateralmost seta; outer plate with 10 setae in 2 rows, inner row of short bifid setae, outer row of 6 elongate, acute and finely serrate. Mouthparts otherwise normal.

Antenna 1 as long as pereonite 1–4 and half of 5 combined along dorsum, peduncle article 2 about 2/3 length of 1, article 3 4/5 length of article 2, flagellum of 8+ articles, slightly longer than peduncle, accessory flagellum of 6 articles, as long as flagellum articles 1–5 and half of 6. Antenna 2 peduncle with few short setae, article 4 2.5 times as long as article 3, 1.4 times as long as 5; (flagellum broken).

Coxal plates 1–3 of equal length, 4 slightly shorter and more tapering to broadly rounded apex, all with row of long setae along distal margin, plates 5–7 normal, plate 6 posterior lobe larger than in 5.

Gnathopod 1 basis as long as ischium, merus and carpus combined, posterior margin with long and medium length setae along entire length, anterior margin with short setae in proximal half, long setae more distally, carpus broadest at posterior proximal 1/4 point immediately anterior to merus, anterior margin with a few setae only, posterior margin densely beset with long setae, lateral face with several short setae in row, propodus 0.45 length of carpus, with 5 pairs of unequally long pectinate setae on posterior margin, dactylus with unguis about half as long as propodus. G nathopod 2 basis slightly longer than ischium and merus combined, posterior margin with row of long setae, anterior margin densely beset with long and short setae; (remaining parts of gnathopod 2 missing).

Pereopods 3–4 basis about 3 times longer than wide, as long as ischium, merus and half of carpus combined, posterior margin with scattered setae of varying length. Pereopod 5 and 6 basis ovoid, longer than wide, medially with row of a few short setae, carpus of pereopod 5 about 0.8 length of propodus. Pereopod 7 basis nearly circular, about as long as wide, medial surface with many scattered small setae, posterior margin smooth except micro-crenulation around distal curvature, entire posterior margin with numerous small setae, carpus 1.4 length of propodus. Pereopods 5–7 with row of 3 short robust setae on anterior margin of propodus.

Uropod 1 peduncle reaching as far as peduncle uropod 2, lateral margin with row of 11 small robust setae, medial margin with row of 8 very long robust setae, inner ramus the longer reaching 5/6 along outer ramus of uropod 3, with several long dorsal robust setae and a few short ventral robust setae. Uropod 2 peduncle reaching nearly 2/3 along uropod 3 peduncle, inner ramus longer than outer with long robust setae, reaching 2/3 along inner ramus of uropod 1, outer ramus with short robust setae. Uropod 3 peduncle about half as long as outer ramus, rami slender oval of subequal length, both reaching a fraction beyond telson, both rami with long plumose setae dorsally, outer ramus with dorsal row of 6 robust setae, mediolateral row of 8 robust setae, and ventrolateral row of 12–13 robust setae, apex pointed with 2 small robust setae in concavity, inner ramus distally with 2 robust setae on dorsal margin near apex and row of 8 robust setae ventrally; both rami with 2 apical small robust setae in hollow.

Telson. Length about 5.5 times greatest depth in lateral view, dorsal view length about 3 times greatest width, reaching to near apex of uropod 3 rami, lobes with 3 robust setae dorsally in distal half and 2 tiny robust setae on apex.

Size. Largest ♀, 10.0 mm. ♂ not known.

Distribution. Pacific Canada, Strait of Georgia, 75 m.

Figures

FIGURE 4. Tiron canadense sp. nov. Holotype, ♀, except S Tiron spiniferus from Western Greenland. clv, head lateral view; md plp, mandible palp; mx1, maxilla 1 (medial view); pleo, pleonites (1–3); tel, telson; up, uropods; uros, urosomites. Scale for holotype clv, 1 mm.

FIGURE 5. Tiron canadense sp. nov. Holotype, ♀. gp1–gp2, gnathopods 1 and 2; p3, 5, 7, pereopods 3, 5, and 7; p7 mv, pereopod 7 basis medial view.