Amblyops amamiensis, Murano, 2012

Murano, Masaaki, 2012, The Genus Amblyops (Crustacea: Mysida: Mysidae: Erythropinae) from East Asia and Australia, with Descriptions of Ten New Species, Species Diversity 17 (1), pp. 49-85 : 52

Amblyops amamiensis sp. nov.

(Figs 1, 2)

Type series. H olotype: adult female (13.6 mm), NS- MT-Cr 21344, RV “Tansei Maru”, KT-70-2 Cruise, St . 454, 29°08 .0′N 129°39 .1′E , east of Amami-Ohshima Island , Nansei Islands, southwestern Japan, 25 April 1970, 16:57–18:18, ORI net that contacted the sea oor at about 1000 m depth during an oblique haul, coll . M . Murano . Paratype: adult female (damaged, ca. 14.5 mm), NSMT-Cr 21345, same data as holotype .

Description.C arapace (Fig. 1A) with evenly rounded anterior margin without distinct rostral projection, covering proximal part of eyeplates; anterolateral corner rounded; posterior margin emarginate, leaving last thoracic somite exposed dorsally.

Eyes (Fig. 1A, B) plate-like without visual elements, rather small, separated from each other; each eyeplate quadrangular with rounded corners, without distinct papilliform projection on anterior margin in dorsal view, but upturned small knob recognized in lateral view (Fig. 1C); middle part of lateral margin and dorsal surface inconspicuously spinulose.

Female antennular peduncle (Fig. 1A, D) rather robust;

rst segment with anterolateral corner prolonged and tipped with several setae; second segment very short; third segment longer than wide, longer than preceding 2 segments combined, armed with many (more than 15) setae on mesial and anteromesial margins.

Antennal scale (Fig. 1A, E) long, extending beyond distal end of antennular peduncle by half of its length, 3.5 times as long as greatest width at about proximal 1/3, becoming somewhat abruptly narrower from widest part to apical end; lateral margin naked, nearly straight, terminating in denticle extending slightly beyond apex of blade; terminal denticle with subsidiary spinule near basal end of its inner margin; distal suture distinct. Antennal peduncle (Fig. 1E, F) 4-segmented, slightly shorter than antennular peduncle; second segment connected to ventral side of third segment, much narrower than succeeding 2 segments. Antennal sympod (Fig. 1E) with stout denticle at anterolateral corner.

Mandibular palp and maxilla as illustrated (Fig. 1H, I). Labrum (Fig. 1G) with anterior margin rounded.

First thoracopodal endopod (Fig. 2A) short and robust; dactylus half as long as carpopropodus, terminating in strong claw. Second thoracopodal endopod (Fig. 2B) rather small; merus longest, slightly longer than combined length of carpopropodus and dactylus; dactylus 1/4 of carpopropodus in length, with slender claw terminally. Fourth thoracopodal endopod (Fig. 2C) very slender; carpopropodus as long as merus, divided into 3 subsegments, proximal subsegment jointed very obliquely with middle subsegment, equal to combined length of succeeding 2 subsegments, distal subsegment slightly shorter than middle one; dactylus small, with slender terminal claw longer than segment supporting it. Fi h thoracopodal endopod (Fig. 2D) similar to fourth but slightly more slender. ffloracopodal exopods (Fig. 2A, B, D) with agellum divided into 9 or 10 segments; basal plate with pointed distolateral corner.

First abdominal somite 1.2 times longer than second, second to h somites subequal, sixth somite 1.8 times longer than h.

All female pleopods reduced to unsegmented single lobes.

Uropodal endopod (Fig. 2E–G) extending slightly beyond tips of posterior spines of telson, armed with 1 or 2 slender spines (2 in holotype, 1 in paratype) on ventral side near inner margin in statocyst region. Uropodal exopod (Fig. 2E) damaged, but extending far beyond end of telson.

Telson (Fig. 2E, H) narrowly linguiform, 1.3 times as long as last abdominal somite, 2.2 times as long as wide at base, abruptly narrowing close to base, then gradually narrowing towards posterior 1/3, and then narrowing again somewhat abruptly towards narrowly rounded apex; lateral margin concave in anterior half and convex in posterior half, armed along posterior 4/5 with about 37 spines, these increasing in length posteriorly; posterior margin armed with pair of long spines, longer than any marginal spines of telson and 1/11 of telson in length; pair of median plumose setae short and feeble, emerging from dorsal surface just in front of apical long spines.

Etymology.ffl e speci c name, amamiensis , is derived from Amami-Oshima, the island near which the specimens were collected.

Remarks. A mblyops amamiensis is recognized by its combined possession of the following four characteristics: (1) the eyeplate is not provided with distinct papilliform projection on the anterior margin; (2) the antennal scale is somewhat abruptly narrowed towards the apical end; (3) the telson has a narrowly rounded posterior margin that lacks small median spines; and (4) the telson is furnished with about 37 spines on the posterior four- hs of each lateral margin.

ffle male is unknown.