Mimoscina setosa ( Barnard, 1930 )

Zeidler, Wolfgang, 2012, A review of the hyperiidean amphipod families Mimonectidae and Proscinidae (Crustacea: Amphipoda: Hyperiidea: Scinoidea) 3533, Zootaxa 3533, pp. 1-74 : 62-63

Mimoscina setosa ( Barnard, 1930)

( Fig. 32)

Parascina setosa Barnard, 1930: 395–397 , fig. 51. Mimonectes setosus — Stephensen & Pirlot 1931: 552. Mimoscina setosa — Vinogradov 1962: 13, figs. 8–9. Hurley 1969: 33. Vinogradov et al. 1982: 129 (key), 130–132, fig. 58. De

Broyer & Jazdzewski 1993: 106. Shih & Hendrycks 1996: 591, 599 (table). Zeidler & De Broyer 2009: 15–16, fig. 3

(distribution map). non — Mori et al. 2010: 3 (list), 8 (list) (here re-determined as Mimonectes gaussi ).

Type material. This species was described from an immature, damaged male, measuring about 5–6 mm in length, from the Southern Ocean , near Scott Island (67°23’S 177°59’W), Terra Nova stn. 178, 0–500 m, 15 December 1910. The unique holotype is in the NHM, London, on one microscope slide (1954.4.30.1) .

Material examined. The unique holotype, as detailed above.

Diagnosis. Following examination of holotype male, 5–6 mm, and according to Barnard (1930) and Vinogradov (1962). Pereon not inflated. Antennae 1 with serrated margins; relative length not recorded. Antennae 2, in females, reduced to four tiny articles, together only as long as the peduncle of A1; in the immature holotype male they are multi-articulate and only slightly longer than half A1. Gnathopod 1; basis relatively short, length 0.6–0.7x remaining articles combined, 1.7x carpus; propodus similar in length to carpus; dactyl thin, relatively straight, length about 0.3x propodus. Gnathopod 2 marginally longer than G1 but similar in structure and relative lengths of articles. Pereopods 3 & 4 similar in structure and length; basis length 1.7–2.0x merus; carpus and propodus of similar length, slightly longer than merus, but in the type the carpus length is 1.6x merus, and propodus length is 0.7x carpus; propodus with long seta on antero-distal corner; dactyl very short; all articles with several long setae on both margins. Pereopod 5 marginally longer than P4; basis length 1.6x merus; carpus slightly shorter than merus, about 1.2x length propodus; dactyl very small, fully retractile. Pereopod 6 similar in length to P5; basis sub-equal in length to merus; carpus length almost 0.7x merus; propodus marginally shorter than carpus; dactyl as for P5. Pereopod 7 marginally shorter than P5; basis length almost twice merus; carpus sub-equal in length to merus; propodus length 0.7x carpus, slightly swollen in male; dactyl as for P6. Uropoda with slender, relatively long, lanceolate rami, with serrated margins; U1 & 2 with inner ramus distinctly longer than outer and much longer than peduncle. Uropod 1; inner ramus length 1.3–1.5x outer, and 1.4–1.5x peduncle; outer margin of peduncle distinctly convex, armed with numerous, short setae; outer margin of outer ramus also with few setae proximally. Uropod 2; inner ramus length 1.4x outer (or similar in length), 1.4x peduncle for female, slightly shorter than peduncle for holotype male; few fine setae distally on outer margin of peduncle and proximally on outer ramus. Uropod 3; inner ramus slightly longer than outer, and 1.4–1.5x length peduncle; peduncle width 0.3–0.4x length. Telson with rounded apex, slightly longer than broad, length almost 0.4x peduncle of U3.

Colour not known for living specimens.

Remarks. This species is distinguished from M. gracilipes by the more setose outer margin of uropod 1, but more readily by the relatively shorter, and less slender, pereopods 5–7, and the relatively shorter merus of pereopod 7. According to Vinogradov et al. (1982) the dactyl of pereopods 3 & 4 may also be retractile but this character is poorly discernible. In the holotype male the dactyl of pereopod 4 is very small but does not seem to be retractile.

In addition to the type there is only one other literature record of specimens captured, also from Antarctic waters. Vinogradov (1964) recorded a female, 4.5 mm, from the Pacific sector (64°03’S 161°59’E), Ob stn. 57, 0–3000 m and a juvenile female, 3.0 mm, from the Indian Ocean sector (64°25’S 92°52’E), Ob stn. 111, 0–2700 m.

Distribution. This seems to be a Southern Ocean species, although there are only three records, from the Pacific and Indian Ocean sectors of the Antarctic, as detailed above.