Siriella spinula Panampunnayil, 1995

Daneliya, Mikhail, Price, W. Wayne & Heard, Richard W., 2018, Revision of the Siriella brevicaudata species group (Crustacea: Mysida: Mysidae) from the West Indo-Pacific, European Journal of Taxonomy 426, pp. 1-80 : 50-51

Siriella spinula Panampunnayil, 1995

Siriella spinula Panampunnayil, 1995: 1942 , figs 24–47.

Siriella spinula – Lowry & Stoddart 2003: 468 (catalogue). — Murano & Fukuoka 2008: 37. — Anderson 2010: 23 (checklist).

Diagnosis

Carapace with anterodorsal margin angular. At least half of subrostral process covered by carapace. Carapace with cephalic part dorsally smooth. Telson as long as last abdominal somite, reaching level of lateral spiniform setae of uropodal exopods, about twice as long as wide anteriorly and 1.4 times as wide anteriorly as posteriorly. Lateral margins slightly convex in middle part and clearly tapering apically, with three anterior and 12 to 14 posterior spiniform setae, gradually increasing in length apically in male and with terminal posterolateral pair of spiniform setae shorter than subterminal pair in female; terminal spiniform setae 0.13–0.14 times as long as telson, 1.2 times as long as subterminal in male and 0.8 in female; subterminal spiniform setae 1.2 times as long as preceding posterolateral in male and 1.4–1.5 in female. Apically telson with three small, but well-visible spinules, 0.2–0.3 times as long as posterolateral terminal spiniform setae; without emargination. Labrum with rather small, but wellestablished, articulated anterior spine, about 0.15 times as long as rest of labrum. Maxilla 1: outer ramus with serrated setae. Maxilla 2: endopod segment 2 with two lateral setae. Pereopod 1–3 merus 4.2–4.8 times as long as wide. Uropodal exopod 4.0 times as long as wide; segment 1 is 2.5 times as long as segment 2, with three or four distolateral spiniform setae in female and four or five in male. Uropodal endopod with 19 to 27 medial spiniform setae in female and 15 to 21 in male; tip of terminal spiniform seta reaching apical margin of ramus.

Type material

Holotype

AUSTRALIA: ♂, 6.5 mm long, SW coast between 33° and 35° S, and 114° and 119° E, upper 50 m of the water column, oblique hauls ( IOBC 0493-10-50- 1994).

Paratype (labelled as allotype)

AUSTRALIA: ♀, 6.6 mm long, same collection data as for holotype ( IOBC 0493 A-10-50- 1994) ( Panampunnayil 1995). Deposited in the Regional Centre of the National Institute of Oceanography, Cochin, India. Not examined here.

Body length

Body length of male 4.9–6.5 mm, of female 5.5–6.6 mm ( Panampunnayil 1995).

Comparison

Siriella spinula is most similar to S. bassi sp. nov., but is distinguished from it by a number of characters (see differences in the comparison section for that species). Considering the body length measurements of Panampunnayil (1995), S. spinula is also smaller in size than S. bassi sp. nov., in which the body length is 7–10 mm. However, this requires verification, because the difference may be due to differences in measurement methods, as well as sampling season.

Siriella spinula is distinguishable from another South Australian species, S. vincenti , by having (1) the carapace lacking a dorsal cephalic tubercle and postcervical elevation (both present in females of S. vincenti ), (2) a narrower uropodal exopod (3.6–3.8 times as long as wide in S. vincenti ), (3) a uropodal exopod with a shorter distal segment (proximal segment 1.8–1.9 times as long as distal in S. vincenti ), (4) a maxilla 2 endopod with only two lateral setae (three or four in S. vincenti ), (5) a maxilla 1 outer

ramus with serrated robust setae (smooth in S. vincenti ) and (6) sexual dimorphism in the length of the telsonal terminal posterolateral pair of spiniform setae (dimorphism absent in S. vincenti ).

Distribution

Known only from the type locality, SW coast of Australia between 33° and 35° S, and 114° and 119° E ( Panampunnayil 1995) ( Fig. 1 ).

Habitat

Collected in <50 m layer of water column (type locality).

Remarks

The species was described rather recently and in good detail by Panampunnayil (1995), and our updated diagnosis and comparison with other species are based on that work. It has not been recorded since the original description.

Figures

Fig. 1. Distribution of species in the Siriella brevicaudata species group. Question mark (?) indicates published record requires verification.