Siriella bassi, 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 : 6-13

Siriella bassi sp. nov.

urn:lsid:zoobank.org:act:E3819332-0BFE-49CF-BC7E-DB52118EF46D

Figs 3–6

Siriella vincenti – Fenton 1986: 48, partim (part of Bass Strait samples). — Lowry & Stoddart 2003: 469, partim (catalogue).

Diagnosis

Carapace with anterodorsal margin angular, apically rounded; sides concave. At least half of subrostral process covered by carapace. Carapace with slight dorsal cephalic and postcervical elevations, more strongly established in male. Telson 1.0–1.1 times as long as last abdominal somite, 2.35–2.5 times as long as wide and 1.3–1.5 times as wide anteriorly as posteriorly, reaching level of lateral spiniform setae of uropodal exopods, narrowing posteriorly. Lateral margins of telson with three or four anterior and 15 to 20 posterior spiniform setae, graded in length posteriorly in males, and terminal posterolateral pair shorter than subterminal or rarely equal to them in females; terminal posterolateral pair of spiniform setae 0.07–0.08 times as long as telson, 1.0–1.2 times as long as subterminal spiniform setae in male and 0.7–1.0 times in female; subterminal pair of spiniform setae 0.8–1.4 times as long as previous posterolateral pair of spiniform setae. Telson apically without emargination; three apical spinules rather well developed, 0.3–0.5 times as long as posterolateral terminal pair of spiniform setae. Labrum with relatively long anterior spine, about 0.25–0.3 times as long as rest of labrum. Maxilla 1: outer apical spiniform setae of outer ramus serrated. Maxilla 2: endopodal segment 2 with two lateral setae. Pereopodal endopod 1–2 merus 4.3–4.4 times as long as wide. Uropodal exopod 3.8–4.0 times as long as wide; segment 1 with four to eight distolateral spiniform setae, 1.9–2.0 times as long as segment 2. Uropodal endopod with 22 to 29 medial spiniform setae, without sexual dimorphism in number, distributed rather unevenly in median part (often in pairs); apical spiniform seta reaching apex of ramus.

Etymology

This species is named after the British explorer of Australia, George Bass (1771–1803). The name also denotes the type locality of the species, the Bass Strait, named after George Bass as well.

Material examined

Holotype

AUSTRALIA: ♀, 8.5 mm long, Victoria, Western Bass Strait , 44 km SW of Cape Otway, 39°06′18″ S, 42°55′36″ E, 81 m, sandy shell, rock, BSS, NZOI R/ V Tangiaroa, cruise 81-T-1, st. 192, bottle 192/14, dredge, 21 Nov. 1981, R.S. Wilson et al. leg., previously identified as S. vincenti by G. Fenton in 1985 ( NMV J5384 ).

Paratypes

AUSTRALIA: 6 ♀♀, 7–8 mm long, Victoria, Central Bass Strait, 100 km SSE of Cape Liptrap, 39°45′54″ S, 145°33′18″ E, 74 m, BSS, R/V Tangaroa, st. 156, grab, sled, 13 Nov. 1981, R.S. Wilson leg., previously identified as S. vincenti by G. Fenton in 1985 ( MNV J11242 ); 2 ♂♂, 8 mm long, Tasmania, Central Bass Strait, 47 km E of Cape Rochon, Three Hummock Island, 40°23′48″ S, 145°32′00″ E, 66 m, mud with shell and sand, FR/V Sarda, cruise 80-Sa-1, st. 113, epibenthic sled, 3 Nov. 1980, M.F. Gomon and G.C.B. Poore leg., previously identified as S. vincenti by G. Fenton in 1985 ( MNV 5430); 1 ♂, 7.5 mm long, Victoria, Eastern Bass Strait, 43 km SE of Port Albert, 38°53′42″ S (38°53.7′ S), 147°06′30″ E (147°06.5′ E), 58 m, coarse shell, BSS, cruise 81-T-1, NZOI R/V Tangaroa, st. 177, Smith- McIntyre grab, sled or trawl, 18 Nov. 1981, R.S. Wilson leg., previously identified as S. vincenti by G. Fenton in 1985 ( MNV J5424); 1 ♂, 7.5 mm long, Victoria, Port Phillip Bay, western sandy region, 38°09′55″ S, 144°44′39″ E, 12 m, PPBES-5 114 3, Smith-McIntyre grab, 18 Oct. 1995, R.S. Wilson, S.P. Heislers et al. leg., previously identified as S. vincenti by S.P. Heislers in 1996 ( NMV J43692 ); 2 ♂♂, 10 mm long, Tasmania, Ransonnet Bay, 40°40′ S, 145°00′ E, FR/V Sarda, cruise 80-Sa-1, plankton net, 3 Nov. 1980, 01:00, P. Forsyth leg., previously identified as S. vincenti by G. Fenton in 1985 ( MNV J5428).

Other material

AUSTRALIA: 1 ♀ (broken telson and pereopods), Tasmania, Central Bass Strait, 35 km N of Cape Wickham, King Island, 39°13′36″ S, 143°55′36″ E, 85 m, R/V Tangiaroa, epibenthic sled, 23 Nov. 1981, R.S. Wilson leg., previously identified as Siriella sp. by G. Fenton in 1985 ( MNV J11237 ); 1 ♀, 7.5 mm long, 1 ♀ (broken telson), 8 mm long, 1 juvenile (broken telson), 5.5–6.0 mm long, Tasmania, Western Bass Strait, 4 km SSW of Currie, King Island, 40°00′22″ S, 143°49′54″ E, 46 m, very fine sand, BSS, cruise 81-T-1, NZOI R/V Tangaroa, st. 197, bottle 197/9, epibenthic sled, 21 Nov. 1981, R.S. Wilson leg., previously identified as S. vincenti by G. Fenton in 1985 ( MNV 5447); 1 ♀, 7 mm long, Victoria, Central Bass Strait, 100 km SSE of Cape Liptrap, 39°45′54″ S, 145°33′18″ E, 74 m, R/V Tangaroa, 13 Nov. 1981, R.S. Wilson leg., previously identified as S. vincenti by G. Fenton in 1985 ( MNV J11218 ); 2 ♂♂, 7.5–8 mm long (both with broken telsons), 3 ♀♀ (no pereopods), 7–7.5 mm long, 1 subadult ♀, 6 mm long, 1 juvenile, 5 mm long, Tasmania, Central Bass Strait, 23 km E of Cape Rochon, Three Hummock Island, 40°22′12″ S, 145°17′00″ E, 40 m, sand, FR/V Sarda, st. 112, bottle 112/24, epibenthic sled, 3 Nov. 1980, M.F. Gomon and G.C.B. Poore leg., previously identified as S. vincenti by G. Fenton in 1985 ( MNV J5441); 1 ♂ (broken head), 7.5 mm long, 1 ♀, 7.5 mm long, 1 subadult ♂, Victoria, Eastern Bass Strait, 40 km SSW of Lakes Entrance, 38°18′00″ S, 147°37′00″ E, 55 m, F/V Silver Gull, st. 209, trawl or sled, 31 Jul. 1983, M.F. Gomon and R.S. Wilson leg., previously identified as S. vincenti by G. Fenton in 1985 ( NMV J11231 ); 1 ♀, Tasmania, Central Bass Strait, 65 km ENE of Cape Rochon, Three Hummock Island, 40°10′54″ S (40°10.9′ S), 145°44′18″ E (145°44.3′ E), 75 m, bryozoa mud, BSS, cruise 81-T-1, NZOI R/V Tangaroa, st. 157, epibenthic sled (Smith-McIntyre grab), 13 Nov. 1981, R.S. Wilson leg., previously identified as S. vincenti by G. Fenton in 1985 ( MNV J5448); 2 ♂♂ (1 broken), 5.5–7 mm long, 1 ♀, 6 mm long, Victoria, Southern Port Phillip Bay, southern section, 38°21′00″ S, 144°51′30″ E, 9 m, sand, PPBES, F/V Melita, st. 985, Smith-McIntyre grab, 9 Dec. 1971, G.C. Poore, S.F. Rainer et al. leg., previously identified as S. vincenti by G.C. Poore in 1975 ( MNV J5468); 2 spec., Tasmania, Central Bass Strait, 20 km NNE of North Point, 40°38′ S, 145°23′ E, 38 m, FR/V Sarda, 4 Nov. 1980, M.F. Gomon and G.C. Poore leg., previously identified as S. vincenti by G. Fenton in 1985 ( MNV J5391).

Description

Body length 7–10 mm.

Female (holotype)

CARAPACE. With anterodorsal margin angular, covering more than half of subrostral process; lateral margins slightly concave ( Fig. 3A ). Carapace with slight cephalic tubercle and postcervical elevation ( Fig. 3C ).

TELSON. 1.1 times as long as last abdominal segment, reaching level of lateral spiniform setae of uropodal exopods, narrowing posteriorly ( Fig. 3D ), 2.4 times as long as wide anteriorly and 1.3 times as wide anteriorly as posteriorly. Lateral margins slightly convex in middle part, with four anterior and 18 posterior lateral spiniform setae; terminal posterolateral pair 0.7–1.0 times as long as subterminal pair; terminal pair of spiniform setae 0.08 of telson length; subterminal pair of spiniform setae 0.8–1.4 times as long as preceding posterolateral pair of spiniform setae. Telson apically without emargination, with three well-visible spinules ( Fig. 3E ), 0.3–0.5 times as long as terminal posterolateral pair of spiniform setae, and a pair of long plumose setae flanking them.

HEAD APPENDAGES. Antennular peduncle rather narrow ( Fig. 3A, G ); distal segment reaching about end of antennal scale and half as long as segment 1, with one medial and four distomedial setae. Antennal scale ( Fig. 3H ) 3.1 times as long as wide and 1.3 times as long as distance from scale base to base of outer spine. Labrum with relatively large anterior spine, 0.3 times as long as rest of labrum ( Fig. 4C ). Mandibular palp ( Fig. 4B ): segment 2 with about 10 inner setae; segment 3 is 0.5 times as long as segment 2, with three medial setae. Right mandible ( Fig. 4E ): incisor with two lamellar cusps, planes of which perpendicular to each other; lacinia mobilis and molar lamellar. Left mandible ( Fig. 4F ): triangular, lamellar, with strongly reduced molar. Maxilla 1 ( Fig. 4G ): outer ramus with 10 apical spiniform setae, among them outer spiniform setae serrated; posterior face with two setae; inner ramus laterally with two setae and apically with four plumose setae. Maxilla 2 ( Fig. 5A ): endopod of segment 2 with two lateral setae; endites with smooth spiniform setae; exopod with 13 setae.

MAXILLIPEDS. Maxilliped 1 endopod; dactylary unguis strong ( Fig. 5B ), 1.7 times as long as dactylus. Maxilliped 2 endopod ( Fig. 5C ): ischium 1.4 times as long as wide and 0.7 times as long as merus; merus 2.3 times as long as wide and as long as carpopropodus; carpopropodus 2.6 times as long as wide; dactylus 1.1 times as long as wide and 0.3 times as long as carpopropodus, with serrated setae; dactylary unguis smooth, 2.1 times as long as dactylus.

PEREOPODS. Pereopod 1 endopod ( Fig. 6A ): preischium without setae; ischium 2.3 times as long as wide; merus 4.3 times as long as wide and 1.6 times as long as ischium, with six groups of mostly concentrated setae; carpopropodus without clear articulation, 5 times as long as wide and 0.8 times as long as merus; dactylus 0.2 times as long as carpopropodus; dactylary unguis 1.75 times as long as dactylus. Pereopod 2 ( Fig. 6B ): preischium without setae; ischium 2.2 times as long as wide; merus 4.4 times as long as wide and 2 times as long as ischium, with four groups of setae; carpopropodus without clear articulation, 3.0 times as long as wide and 0.8 times as long as merus; dactylus 0.2 times as long as carpopropodus; dactylary unguis 1.9 times as long as dactylus; paradactylary setae not extending beyond tip of unguis.

UROPODS. Uropodal exopod ( Fig. 3D ) 3.8 times as long as wide, with clear joint between segments; segment 1 with five distolateral spiniform setae; segment 1 is 1.9 times as long as segment 2. Uropodal endopod with 26 medial spiniform setae, some of them medially in pairs; terminal spiniform seta reaching apex of ramus.

Male

Carapace dorsal surface with rather clearly established cephalic tubercle and postcervical elevation ( Fig. 3B ). Telson with terminal spiniform setae 1.0–1.2 times as long as subterminal ( Fig. 3F ).Antennular peduncle rather strong ( Fig. 3B ); distal segment extending anteriorly beyond antennal scale and about as long as segment 1, rather strong. Appendix masculina conical. Antennular inner flagellum normal, not dilated or meandering in proximal part.

Comparison

Siriella bassi sp. nov. is distinguished from all species within the brevicaudata group by having the telson typically longer than the last abdominal somite, 2.35–2.5 times as long as wide anteriorly and with relatively short terminal spiniform setae, less than 0.08 the length of the telson. In all other members of the group, the terminal spiniform setae are more than 0.08 times the telson length. Siriella bassi sp. nov. attains the largest reported body length (10 mm) and has a larger number of spiniform setae on the posterolateral margin of the telson, the distolateral margin on the proximal segment of the uropodal exopod, and the medial margin of the uropodal endopod than any in other species within the brevicaudata group.

Although in the past it has been confused with Siriella vincenti ( Fenton, 1986) , S. bassi sp. nov. appears most similar to S. spinula , which is known from the southwest coast of Australia. In addition to its longer telson and associated terminal spiniform setae, S. bassi sp. nov. is distinguished from S. spinula by having (1) the labrum apparently with a longer spine (0.25–0.3 against 0.15 of the rest of the labral length in S. spinula ), (2) the telson with a greater number of posterolateral spiniform setae (15 to 20 against 12 to 14 in S. spinula ), (3) a cephalic tubercle and a postcervical elevation (absent in S. spinula ) and (4) the uropodal exopod with a longer proximal article (1.9–2.0 times as long as the distal article in S. bassi sp. nov. compared to 2.5 times as long in S. spinula ).

Occasionally S. bassi sp. nov. occurs sympatrically with S. vincenti . Besides its distinctive telson and lengths of its terminal spiniform setae, the new species can be distinguished from S. vincenti by (1) a cephalic tubercle present in both sexes (absent in males of S. vincenti ), (2) labrum anterior spine rather long (relatively short, about 0.2 times as long as the rest of the labrum in S. vincenti ), (3) maxilla 1 having the outer ramus with serrated robust setae and (4) endopod of maxilla 2 with the distal article having two lateral setae (three to four on that of S. vincenti ). Furthermore, the male telson of S. bassi sp. nov. has a subterminal posterolateral pair of spiniform setae that is shorter than or about as long as the terminal pair of spiniform setae (terminal spiniform setae shorter or rarely as long as the subterminal setae on the telsons of both sexes in S. vincenti ). For more specific characters distinguishing S. bassi sp. nov. from the other members of the group, we refer to Table 1 and the dichotomous key herein.

Distribution

Numerous type and additional collections come from the Bass Strait between the Australian continent and the island of Tasmania, adjacent to Port Phillip Bay (continental side) and Ransonnet Bay (insular side) ( Figs 1–2 ). Not known beyond the Bass Strait region.

Habitat

Based on depth records from the sampling localities, the species is found in the Bass Strait from depths of 38 to 85 m, and only in two cases, in Port Phillip Bay, at 9– 12 m. In this respect it is seemingly distinguished from S. vincenti , found only in coastal areas at depths shallower than 20 m.

Remarks

The Museum Victoria (NMV) possessed 21 samples from Southern Australia, collected during Port Phillip Bay Environmental Study (PPBES, 1969–1973), Westernport Bay Environmental Study (WBES, 1973–1974) of the Australian Ministry of Conservation, and Bass Strait Survey of the Victoria Insitute of Marine Science (BSS, 1980, 1981, 1983), identified previously and deposited as S. vincenti . We re-examinated this material and recovered, apart from S. vincenti itself (see material in the relevant species section), a number of samples of a new species described here as S. bassi sp. nov., as well as S. cf. australis from the thompsonii group and damaged specimens of Doxomysis sp., which are not treated here.

Figures

Fig. 3. Siriella bassi sp. nov., Australia, Victoria, Western Bass Strait. A. ♀, anterior part of body. B. ♂, anterior part of body. C. Anterior part of carapace, lateral view. D. Telson and left uropods. E. ♀, posterior part of telson. F. ♂, posterior part of telson. G. Peduncle of antenna 1, dorsal view. H. Antennal scale and peduncle of antenna 2, ventral view. A, C–E, G–H = holotype, ♀, length 8.5 mm; B, F = paratype, ♂, length 7.5 mm. Scale bars: A–C = 1 mm; D, G–H = 0.25 mm; E–F = 0.1 mm.

Fig. 4. Siriella bassi sp. nov., holotype, ♀, length 8.5 mm, Australia, Victoria, Western Bass Strait. A. Distal part of mandibular palp, medial view. B. Mandibular palp, lateral view. C. Labrum, ventral view. D. Labium (left side not shown), posterior view. E. Right mandible. F. Left mandible. G. Maxilla 1, posterior view. Scale bars: A, C–G = 0.1 mm; B = 0.25 mm.

Fig. 5. Siriella bassi sp. nov. Australia, Victoria, Western Bass Strait. A. Maxilla 2, anterior view. B. Endopod of maxilliped 1, posterior view. C. Endopod of maxilliped 2, posterior view. D. Pleopod 4. A–C = holotype, ♀, length 8.5 mm; D = paratype, ♂, length 7.5 mm. Scale bars: 0.25 mm.

Fig. 6. Siriella bassi sp. nov., holotype, ♀, length 8.5 mm, Australia, Victoria, Western Bass Strait. A. Endopod of pereopod 1, posterior view. B. Endopod of pereopod 2, posterior view. Scale bars: 0.25 mm.

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

Fig. 2. Distribution of species in the Siriella brevicaudata species group along the southern Australian coast.