Siriella talbotae, Daneliya & Price & Heard, 2018

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 : 57-63

Siriella talbotae sp. nov.

urn:lsid:zoobank.org:act:681E1A77-B712-493A-B05B-606A2E199224

Figs 26–28

Siriella vincenti – Fenton 1986: 48, partim (Lizard Island). — Talbot 2009: 33 , figs 21–22.

Diagnosis

Carapace with anterodorsal margin rather shallow, weakly angular or nearly rounded, not covering subrostral process. Telson about as long as last abdominal somite, 2.0–2.1 times as long as wide anteriorly and 1.3–1.4 times as wide anteriorly as posteriorly; lateral margins with four anterior and 14 to 17 gradually increasing in length terminally posterior spiniform setae; terminal posterolateral pair of spiniform setae 0.09 times as long as telson and 1.3–1.4 times as long as subterminal pair of spiniform setae; subterminal spiniform setae 1.1–1.2 times as long as preceding posterolateral spiniform setae; without emargination. Telson with apically minute spinules rather long, 0.4 times as long as terminal posterolateral pair of spiniform setae. Labral spine rather long, 0.25–0.3 times as long as rest of labrum. Maxilla 1 outer ramus with robust, smooth setae. Maxilla 2 endopod with two distolateral setae. Pereopod 1–3 merus 3.4–3.5 times as long as wide. Uropodal exopod 3.5–3.7 times as long as wide, with four to six lateral spiniform setae; segment 1 is 1.7–1.8 times as long as segment 2. Uropodal endopod with 17 or 18 small medial spiniform setae, distributed rather evenly; apical spiniform seta not reaching apex of ramus.

Etymology

Named after the species collector Mabel Suzette Talbot, for her distinguished contribution to our knowledge of the Australian mysid fauna.

Material examined

Holotype

AUSTRALIA: ♂, 5 mm long, Queensland, Lizard Island , lagoon passage between Palfrey Island and South Island, 14°40′ S, 145°28′ E, on sand, STL 76 L14, light trap, 18 May 1976, M.S. Talbot leg., previously identified as S. vincenti by M.S. Talbot in 2006 ( Talbot 2009) ( AM P.98726).

Paratypes

AUSTRALIA: 2 juveniles, same collection data as for holotype ( AM P.74065); 1 ♂ (dissected, cephalothorax and abdominal segment 6 missing; figs 21–22 in Talbot 2009 are probably based on it), 1 juvenile, same collection data as for holotype, STL 76 L13 ( AM P.74064).

Description

Male (holotype)

CARAPACE. Anterodorsal margin of carapace short, weakly angular, with slightly convex lateral margins ( Fig. 26A ). Subrostral process not covered by carapace. Dorsal surface of carapace deformed in head part, with slight postcervical elevation.

TELSON. About as long as last abdominal somite, 2.1 times as long as wide anteriorly and 1.3 times as wide anteriorly as posteriorly; lateral margins with four anterior and 14 and 17 gradually increasing in length terminally posterior spiniform setae; terminal spiniform setae 0.09 times as long as telson and 1.3–1.4 times as long as subterminal spiniform setae; subterminal spiniform setae 1.1–1.2 times as long as preceding posterolateral spiniform setae; without emargination; apically with three minute spinules, 0.4 times as long as terminal spiniform setae ( Fig. 26 B–C).

HEAD APPENDAGES. Eyes 0.6 times as long as wide and 0.7 times as long as head width. Antennular peduncle same as in other species of the group ( Fig. 26A, D ). Male process curved medially, conical, with numerous fine, long setae. Antennular inner flagellum normal, not dilated or meandering in proximal part. Antennal scale reaching half of antennular peduncle segment 3, 3.1 times as long as wide. Total antennal scale length 1.3 of length from scale base to lateral spine base; maximal width 1.2 of distal width ( Fig. 26E ). Labrum with strong anterior spine, about 0.3 times as long as rest of labrum ( Fig. 26F ). Mandibles typical for the genus ( Fig. 27 B–C); palp segment 2 is 1.9 times as long as wide and 1.5 times as long as segment 3, with short and long outer setae; palp segment 3 with five proximomedial and seven distomedial setae ( Fig. 27A ). Maxilla 1 ( Fig. 27D ): apical robust setae of outer ramus mostly smooth, with occasional, fine serration. Maxilla 2: exopod with 10 setae; endopod segment 2 with two lateral setae.

MAXILLIPEDS. Maxillipeds 1 and 2 as typical for the genus, both with strong dactylar unguis. Maxilliped 2 merus 1.2 times as long as carpopropodus ( Fig. 27E ).

PEREOPODS. Pereopod 1 endopod ( Fig. 27F ): preischium without setae; ischium 2.1 times as long as wide; merus 3.4 times as long as wide, 1.5 times as long as ischium; carpopropodus 5.4 times as long as wide and 0.9 times as long as merus, its segment 1 is 0.3 times as long as segment 2; dactylus with unguis 0.4 times as long as carpopropodus; paradactylary setae not reaching unguis apex. Penis tubular, curved anteriorly, with four subapical setae ( Fig. 27G ).

PLEOPODS. Pleopod 1 uniramous, with linear pseudobranchia ( Fig. 28A ). Pleopods 2–4 biramous, with spiral pseudobranchia; rami11-segmented ( Fig. 28 B–E).Pleopod 5biramous, with linear pseudobranchia; rami 9–10-segmented ( Fig. 28F ).

UROPODS. Uropodal exopod 3.5 times as long as wide; segment 1 is 1.7 times as long as segment 2, with five distolateral spiniform setae ( Fig. 28H ). Uropodal endopod with 17 small medial spiniform setae, not reaching apex ( Fig. 28G ).

Female

Unknown.

Color

According to Talbot (2009), eyes brown-gold.

Comparison

Siriella talbotae sp. nov. was initially confused with S. vincenti , from which it differs by (1) the carapace having a shorter, nearly rounded anterodorsal margin, not covering most of the subrostral process (angular, covering almost entire subrostral process in S. vincenti ), (2) the cephalic tubercle being absent, (3) the eye color, which is brown-gold compared to black in S. vincenti , (4) the relative length of the telsonic terminal spiniform setae (shorter than or equal to subterminal and 0.11–0.13 times as long as telson in S. vincenti ), (5) the telson with longer apical spinules (0.2–0.3 of terminal spiniform setae in S. vincenti ); (6) labrum with longer anterior spine (about 0.2 times as long as rest of labrum in S. vincenti ), (7) the maxilla 2 endopod with fewer lateral setae (three or four setae in S. vincenti ) and (8) by the wider pereopods (merus 4.6–5.0 times as long as wide in S. vincenti ).

It is not possible to establish a morphological proximity of S. talbotae sp. nov. to any known species in the brevicaudata group, as this species takes an intermediate position between all of them. On the one hand, it is similar to Southern Australian species like S. bassi sp. nov. and S. vincenti by having a long telson and a long spine on the labrum, but at the same time, it is similar to all the tropical species by having a rounded anterodorsal margin of the carapace, wider pereopods and a small number of spiniform setae on the uropodal endopods.

Siriella talbotae sp. nov. can occasionally be found together with S. lacertilis and is distinguished from it by (1) the absence of a cephalic tubercle (present in females of S. lacertilis ), (2) a longer telson (shorter than last abdominal somite and 1.7 times as long as wide in anterior part in S. lacertilis ), (3) a telson with a larger number of posterior spiniform setae (only 9 known in S. lacertilis ), (4) a telson with a shorter terminal spiniform seta (0.25 times as long as telson in S. lacertilis ), (5) a telson with shorter subterminal spiniform setae (1.8–2.0 times as long as last posterolateral in S. lacertilis ) and (6) labrum with a long anterior spine (rather short, 0.1–0.15 times as long as rest of labrum in S. lacertilis ).

Distribution

The species is so far known only from the type locality Lizard Island of the Great Barrier Reef in the Coral Sea ( Fig. 1 ).

Habitat

Collected with Anisomysis pelewensis Ii, 1964 , at night above a sandy bottom ( Talbot 2009).

Remarks

Talbot (2009) provided a detailed description and illustrations of a male specimen of the species from the type material, and we chose not to illustrate maxilla 2, maxilliped 1 and pereopod 6 here ( Talbot 2009: figs 21–22). Though identified as S. vincenti from South Australia, she mentioned a number of differences from the original description (W.M. Tattersall 1927b), among them the eye color, carapace shape and other minor meristic variations. As in the case with other species of Siriella , the articulation in the distal part of the antennal scale and the proximal part of the pereopodal carpopropodi are not always clearly detected, and therefore cannot serve as distinguishing features, also mentioned by Talbot. After redescribing S. vincenti (see below), we noticed a number of additional characters that clearly distinguish it from the Queensland specimens, and describe the latter as S. talbotae sp. nov.

Figures

Fig. 26. Siriella talbotae sp. nov., holotype, ♂, length 5 mm, Lizard Island, Queensland, Australia. A. Anterior part of body. B. Telson. C. Posterior part of telson, dorsal view. D. Peduncle of antenna 1, dorsal view. E. Antennal scale. F. Labrum. G. Labium (left part not shown), posterior view. Scale bars: A = 1 mm; B, D–F = 0.5 mm; C, G = 0.25 mm.

Fig. 27. Siriella talbotae sp. nov., holotype, ♂, length 5 mm, Lizard Island, Queensland, Australia. A. Mandibular palp, lateral view. B. Right mandible. C. Left mandible. D. Maxilla 1, anterior view. E. Endopod of maxilliped 2, posterior view. F. Endopod of pereopod 1, posterior view. G. Penis. Scale bars: A–D = 0.25 mm; E–G = 0.5 mm.

Fig. 28. Siriella talbotae sp. nov., holotype, ♂, length 5 mm, Lizard Island, Queensland, Australia. A. Pleopod 1, lateral view. B. Pleopod 2, lateral view. C. Pleopod 3, anterior view. D. Pleopod 4, lateral view. E. Distal part of pleopod 4. F. Pleopod 5, lateral view. G. Endopod of uropod, ventral view. H. Exopod of uropod, ventral view. Scale bars: A–D, F–H = 0.5 mm; E = 0.25 mm.

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