Chevreuxiopsis franki, Halfter, Svenja & Oliver Coleman, Charles, 2019

Halfter, Svenja & Oliver Coleman, Charles, 2019, Chevreuxiopsisfranki gen. n., sp. n. (Crustacea, Amphipoda, Thoriellidae) from the deep sea southwest of Tasmania, Zoosystematics and Evolution 95 (1), pp. 125-132 : 125

Chevreuxiopsis franki sp. n. Figures 1, 2, 3, 4, 5

Material examined.

Holotype: female (the specimen appears to have unsetose oostegites), 12 mm.

Type locality.

The specimen was collected with a McLane 21-cup sediment trap at 1,000 m depth between the 11 and 26 August 1998 at the Southern Ocean Time Series site (SOTS, 46°45.52′S, 142°5.38′E), southwest of Tasmania, Australia (ZMB Crust 31700).

Etymology.

The species is named for Frank Halfter, the father of the first author.

Diagnosis.

As for generic diagnosis.

Description

(based on holotype, 12 mm).

Body (Fig. 1c). Head deeper than long, shorter than pereonite 1. Pereonite 2 slightly longer than 1. Pereonites 3 and 4 subequal in length. Pereonite 5 as long as pereonite 2. Pleonites subequal in length, posteroventrally rounded. Urosomite 1 longer than the fused urosomites 2 and 3. Telson absent.

Head (Fig. 1c) with anterior rounded lobe between insertion of antenna 1 and 2. Eyes present, dark pigments visible in alcohol; weakly reniform, extended dorsoventrally. Antenna 1 (Fig. 1a, c) about 2 × as long as antenna 2; peduncular article ratios 1: 0.4: 0.6, width successively smaller; 15 flagellum articles, slender, with very few slender setae. Antenna 2 (Figs 1b, 6) peduncle articles slender, with 2 minute basal articles (which were damaged during dissection), article 3 short; article 4 about 2 × as long as article 3; article 5 as long as article 1-4 combined; flagellum article 1 distally expanded, about 3 × as wide as basal articles, posterodistally lobate; article 2 and 3 proximally as wide as peduncular article 3 and posterodistally drawn out into long narrow lobes; article 4 lanceolate, distally pointed and inside with a dense mass of tissue. Mouthparts (Figs 1c, 2f) extended ventrally, all covered by large outer plates of maxilliped, which leave an anteriorly and ventrally slit-like opening and additionally surrounded posteriorly by wide bases of pereopods 1. Mandibles to maxilla 2 directed anteriorly; ventrally of these mouthparts is a dense tissue mass (dashed in Fig. 2f, 3a), that might represent the inner maxillipedal plates. Both mandibles slender without molar, setal rows or palp (Fig. 2a, b). Labrum without pronounced epistome, rounded from lateral view (Fig. 1d). Lower lip (Fig. 2e) with rather long rounded apices with few setae in the hypopharyngeal gap and with slender mandibular lobes. Maxilla 1 (Fig. 2c, d) inner plate with 2 plumose apical setae; outer plate with 6 plus 1 apical robust setae; palp 2-articulate, line between both articles barely visible, distal article lanceolate, with 1 short seta on tapering tip. Maxilla 2 (Fig. 2g) inner plate with some medial setae; outer plate with 4 distolateral plumose setae.

Pereon.Pereopod 1 (Fig. 3b) dark purple/black pigmented in ethanol; coxa subquadrate; basis anteromarginally expanded with short nose-shaped protrusion; ischium and merus subequal; carpus weakly expanded distally 2.2 × as long as wide; propodus slightly tapering distally with distal knob-like dactylus. Pereopod 2 (Fig. 3d, e) basis elongate and slender; ischium 2.7 × as long as wide; merus short, distally pointed; carpus longer than propodus with cushions of slender, hair-like setae on anterior and posterior margins; propodus anteromarginally rounded with similar setation as carpus; dactylus subapically, accompanied with long several long setulated setae and with few setae on the inner curvature. Pereopod 3 (Fig. 3c) coxa subrectangular, slightly directed anteriorly; basis as long as coxa; ischium 0.6 × the width of basis; merus relatively short, distally expanded; carpus wider than long, distally expanded; carpus curved posteriorly, distally oblique; dactylus with proximal rounded joint, weakly curved, slender; propodus and dactylus form subchelate complex. Pereopod 4 (Fig. 4a) coxa largest, about 4 × as long as coxa 1, surpassing basis, ischium and part of merus, anteriorly convex, posteriorly straight; basis to dactylus subequal to pereopod 3, except for the slightly longer carpus. Pereopod 5 (Fig. 4b) coxa bilobed; basis to merus subequal to pereopod 4; carpus shorter than wide, with anterior process; propodus curved anteriorly with oblique distal margin; carpus and long, slender, weakly curved dactylus form a very large subchela.

Pereopod 6 (Fig. 5a, d) coxa wide, weakly bilobate, posterior lobe slightly longer than anterior one; basis about half as long as coxa width; ischium longer than wide; merus expanded posterodistally; carpus short, distally expanded, with some small teeth anteromarginally; propodus, relatively slender, convex posteromarginally, anteromarginally straight, with marginal small teeth, especially on the medial face; dactylus falcate.

Pereopod 7 (Fig. 4c) coxa shorter than wide, subrectangular; basis posteroproximally weakly expanded, somewhat tapering distally; ischium subquadrate; merus weakly expanded posterodistally; carpus subquadrate; propodus convex posteromarginally, straight anteromarginally; dactylus much shorter than preceding appendages.

Pleon.Pleopod 1 (Fig. 5b, c) peduncle 2 × as long as wide; coupling hooks (Fig. 5c) long with rows of protrusions ventrally; both rami slightly longer than peduncle, inner ramus somewhat shorter than outer ramus; swimming setae moderately long with dense setulation (Fig. 5f).

Urosome. First urosomite longer than the fused second and third segment; urosomite 2 expanded midlaterally and weakly incised posteromarginally forming 2 short rounded lobes; peduncle of uropod 1 2.5 × as long as wide; outer ramus lanceolate; inner ramus spine-like, 25% of outer ramus length; uropod 2 peduncle shorter than that of uropod 1 and weakly expanded distally; outer ramus slightly wider compared to that of uropod 1; inner ramus 23% of outer ramus. Telson absent.

Distribution.

The species is so far only known from the type locality.