Siriella muranoi, 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 : 36-43

Siriella muranoi sp. nov.

urn:lsid:zoobank.org:act:011E640D-911B-46D1-A770-169C86EE7797

Figs 14–17

Diagnosis

Carapace with anterodorsal margin rounded, not covering subrostral process. Carapace with slight tubercle and postcervical elevation. Telson 0.9 times as long as last abdominal somite, 1.6–1.7 times as long as wide anteriorly and 1.5 times as wide anteriorly as posteriorly. Telson lateral margins with three anterior and 10 to 16 posterior spiniform setae after gap; last two posterolateral pairs of about same length, longer than preceding posterolateral. Telson with terminal posterolateral pair of spiniform setae 0.13–0.14 times as long as telson and 1.0–1.1 times as long as subterminal. Subterminal pair of spiniform setae 1.2 times as long as preceding posterolateral. Telson apically without emargination, with small, but well-visible spinules, 0.25–0.3 times as long as posterolateral terminal pair of spiniform setae. Labrum with small, but well-developed anterior spine, about 0.2 times as long as rest of labrum. Maxilla 1 with distal robust smooth setae. Maxilla 2 endopod segment 2 with three or four lateral setae along entire margin. Pereopod 1–3 merus 3.8–4.1 times as long as wide. Uropodal exopod 4.2 times as long as wide; exopod segment 1 is 1.7 times as long as segment 2, with three to five distolateral spiniform setae. Uropodal endopod with 11 to 14 medial spiniform setae, extending nearly to ramus apex.

Etymology

The species is dedicated to the distinguished Japanese mysid taxonomist Masaaki Murano for his outstanding contributions to the study of the Indo-Pacific fauna.

Material examined

Holotype

AUSTRALIA: ♂, 5.5 mm long, Northern Territory, Port Essington, Table Head , 11°14.8′ S, 132°11.2′ E, low water, CP / 45, 11 May 1983, A. J. Bruce leg., previously identified as Siriella hanseni by M. Murano ( NTM Cr018984).

Paratypes

AUSTRALIA: 2 ♂♂, 5.5–6.5 mm long, 3 ♀♀, 3.5–7.0 mm long, 3 subadult ♀♀, 4 juveniles, Northern Territory, Port Essington, Table Head, 11°14.8′ S, 132°11.2′ E, low water, CP / 45, 11 May 1983, A. J. Bruce leg., previously identified as Siriella hanseni by M. Murano ( NTM Cr 012269); 1 ♂, 6 mm long, 1 ♀, 6.5 mm long, Northern Territory, Darwin, East Point, Dudley Point Reef, 12°25.2′ S, 130°49.1′ E, AJB/4, LWS, poison, 6 Sep. 1982, A. J. Bruce leg., previously identified as Siriella hanseni by M. Murano ( NTM Cr 012248); 1 ♂ (appendages and telson in same vial), 6.5 mm long, 1 ♀, 6 mm long, 2 subadult ♀♀, 5.0 mm long, Northern Territory, Darwin, Dudley Point Reef, AJB/ 3, 19 Sep. 1981, A. J. Bruce leg., previously identified as Siriella hanseni by A. Udrescu ( NTM Cr000109); 1 juvenile, Northern Territory, Darwin, Nightcliff Beach, 12°24.0′ S, 130°51.0′ E, AJB/35, LWS, rotenone, 11 Sep. 1987, D. Sachs leg., previously identified as Siriella hanseni by M. Murano ( NTM Cr 012258).

Description

Body length of males 5.5–6.5 mm, of females 3.5–7.0 mm.

Male (holotype)

CARAPACE. Anterior part slightly wider than abdominal somite 1. Carapace anterodorsal margin rounded, not covering spiniform subrostral process ( Fig. 14B ). Posterior margin of carapace exposing three thoracic somites dorsally.

TELSON. Telson 0.9 times as long as last abdominal somite ( Fig.14A ), 0.6 times as long as uropodal endopod, 1.6 times as long as wide anteriorly and 1.5 times as wide anteriorly as posteriorly ( Fig. 14D ). Apical margin of telson with three rather small spinules, clearly visible in dorsal view, 0.3 times as long as posterolateral terminal pair of spiniform setae, and two long plumose setae, longer than spiniform setae flanking them. Lateral margins of telson, with three anterior and 12 and 14 posterior spiniform setae after gap, with groups of shorter spiniform setae followed by longer, but generally increasing in length towards apex. Terminal posterolateral pair of spiniform setae 0.14 times as long as telson and about as long as subterminal pair of spiniform setae; subterminal spiniform setae 1.2 times as long as preceding posterolateral.

HEAD APPENDAGES. Eyes 1.1–1.2 times as long as wide and 0.6 times as long as width of anterior part of carapace. Peduncle of antennae more robust than in female, about twice as long as peduncle of antenna 2; segment 1 about twice as long as wide; segment 3 is 1.9 times as long as wide and as long as segment 1; male process along posteromedial margin of segment 3, conical, distal advanced part 0.4 times as long as segment 3 ( Figs 14B , 15A ). Antennal scale with clear distal articulation, shorter than peduncle of antenna 1 and 1.5 times as long as peduncle of antenna 2; scale 3.3 times as long as wide, 1.3 times as long as distance from scale base to outer spine base; maximal width 1.3 times distal width; distal segment with five setae ( Figs 14B , 15B ). Labrum with small, but well-established anterior spine, about 0.2 times as long as rest of labrum ( Fig. 15E ). Mandible ( Fig. 15 C–D): palp segment 2 is 1.7 times as long as wide with long setae along margins; segment 3 is 0.7 times as long as segment 2, with six long proximomedial, six short distomedial and three long distolateral setae. Distal robust setae of maxilla 1 smooth ( Fig. 15F ). Maxilla 2 exopod oval, with 13 setae along outer margin; endopod segment 2 with four lateral setae along entire margin and multiple medial setae and stronger, finely serrated setae flanking them; endites with strong, spiniform setae.

MAXILLIPEDS. Exopod of thoracopods 8–9-segmented. Maxilliped 1 without endites; segments short and strong; basis with a group of distomedial setae; preischium with one seta; ischium with seven medial setae; merus, the largest segment, 1.2 times as long as wide, with about 10 medial and one distolateral setae; carpopropodus with three lateral and four distomedial setae; dactylus with strong smooth unguis; dactylary setae about as long as unguis; unguis more than twice as long as dactylus ( Fig. 15G ). Maxilliped 2: basis with proximal medial seta and distal medial group of setae; preischium with one medial seta; ischium, the widest segment, 1.1–1.2 times as long as wide, with numerous setae along medial margin and one lateral seta; merus 1.9 times as long as wide and 1.7 times as long as ischium, with three medial groups of two–three setae and two distolateral setae; carpopropodus 2.3 times as long as wide, with seven distal anterolateral setae, two medial bunches of two or three long setae, and three short distal posteromedial setae; dactylus longer than wide, 0.3 times as long as carpopropodus, with strong smooth unguis, three anterior and three lateral bunches of thin, strong smooth setae; unguis 2.1 times as long as dactylus ( Fig. 16A ).

PEREOPODS. Pereopodal endopods ( Figs 16 B–D, 17A–C): ischium about 0.6–0.7 times as long as merus; carpopropodus without secondary joint. Pereopod 1 ( Fig. 16B ): preischium with one seta; ischium laterally convex, twice as long as wide, with one lateral seta and many short and long medial setae; merus 3.9 times as long as wide, with about 10 medial groups of long and short setae, three lateral setae and distolateral bunch of two setae; carpopropodus about 5 times as long as wide and 0.8 times as long as merus; dactylus 0.18–0.2 times as long as carpopropodus and 2.2 times as long as wide; dactylar unguis 1.7–1.8 times as long as dactylus; paradactylary setae nearly reaching ungual apex. Pereopods 2–4 show slight reduction in width of segments (except for pereopod 2) and number of setae; paradactylary setae not reaching ungual apex ( Figs 16 C–D, 17A). Pereopods 5–6 ( Fig. 17 B–C): preischium with one–two setae; ischium 2.8–2.9 times as long as wide, with nearly parallel margins, one or two medial setae and distomedial bunch of two setae; merus 3.9–4.3 times as long as wide, with two–three medial groups of one–three setae; carpopropodus 7.0 times as long as wide; dactylus 3.7 times as long as wide; dactylary unguis 1.8 times as long as dactylus; paradactylary setae not reaching half-length of unguis. Penis cylindrical, curved, with two long subapical setae, directed posteriorly ( Fig. 17D ).

PLEOPODS. Pleopod 1 uniramous. Pleopods 2–5 biramous; rami 11-segmented; pseudobranchiae bilobate, spirally coiled in pleopods 2–4 and straight in pleopod 5 ( Fig. 17 E–G). Terminal setae of pleopod rami not modified.

UROPODS. Uropodal exopod 1.2 times as long as endopod and 4.2 times as long as wide; exopod segment 1 is 1.7 times as long as segment 2, with four distolateral spiniform setae ( Fig. 14D ). Uropodal endopod with 12 medial spiniform setae, distally not becoming longer, occupying almost entire ramus length, though not extending to apex.

Female

Peduncle of antenna 1 slender and longer than in male; segment 1 about 3 times as long as wide and 1.2 times as long as segments 2 and 3 together, with five short distal dorsolateral setae; segment 2 with five short distal dorsolateral and one long plumose distomedial setae; segment 3 is 1.2 times as long as wide, with one medial and four long plumose distomedial setae. Segment 3 of mandibular palp with three or four proximomedial setae. Pereopods 5 and 6 each with oostegite. Pleopods lamelliform, setose.

Comparison

Siriella muranoi sp. nov. has a distinct pattern of posterior spiniform setae on the telson: terminal and subterminal pairs are nearly equal in length and longer than preceding posterolateral spiniform setae. It most closely resembles S. lacertilis , S. lingvura and S. tabaniocula sp. nov., differing from the first species by (1) the telson with a shorter terminal posterolataral pair of spiniform setae (rather long, 0.25 times as long as telson and twice as long as preceding posterolateral in S. lacertilis ), (2) the telson with possibly a greater number of posterolateral spiniform setae (only nine were reported in S. lacertilis ), (3) maxilla 1 with smooth distal setae (serrated in S. lacertilis ) and (4) the uropodal exopod with slightly shorter distal segment (proximal 1.4–1.5 times as long as distal segment in S. lacertilis ).

Siriella muranoi sp. nov. is distinguished from S. lingvura by having (1) a cephalic tubercle, (2) a telson with fewer anterolateral spiniform setae (five or six in S. lingvura ), (3) a telson with a shorter terminal posterolateral pair of spiniform setae (clearly longer than subterminal in S. lingvura ), (4) slightly narrower pereopodal endopods (merus of pereopods 1–3 is 3.5 times as long as wide in S. lingvura ) and (5) a uropodal endopod with fewer spiniform setae (15 or 16 in S. lingvura ). For differences from another closely related species, S. tabaniocula sp. nov., see its corresponding section.

Previously, S. muranoi sp. nov. was confused with S. hanseni , from which it is, in fact, distinguished by a large set of characters: (1) carapace with dorsal cephalic tubercle and postcervical elevation (absent in S. hanseni ), (2) shorter telson, which is about as long as or slightly longer than the last abdominal somite in S. hanseni , (3) pattern of telsonal posterior spiniform setae (three to six terminal nearly equal in length in S. hanseni ), (4) labrum with quite well-established anterior spine (with very short, barely visible, <0.1 times as long as the rest of the labrum in S. hanseni ) and (5) uropodal exopod with slightly longer distal segment (proximal segment 1.7 times as long as distal, which is 1.9–2.3 in S. hanseni ).

Distribution

Australia: Northern Territory, Arafura Sea ( Fig. 1 ). Type locality: Port Essington inlet.

Habitat

Shallow water.

Remarks

The specimens which formed the type series of S. muranoi sp. nov. were identified by various scholars as S. hanseni , because the latter species was not originally described in sufficient detail to distinguish it from other related species. After redescription of the type material of S. hanseni (in this study; see above), it was determined that the specimens from the Northern Territory diverged in a number of characters and should be considered a new species.

Figures

Fig. 14. Siriella muranoi sp. nov., holotype, ♂, length 5.5 mm, Port Essington, Arafura Sea, Northern Territory, Australia. A. Habitus. B. Anterior part of body. C. Anterior part of carapace, lateral view. D. Posterior part of body (left uropods not shown). E. Uropodal endopod, ventral view. Scale bars: A, C = 1 mm; B, D–E = 0.5 mm.

Fig. 15. Siriella muranoi sp. nov., holotype, ♂, length 5.5 mm, Port Essington, Arafura Sea, Northern Territory, Australia. A. Antenna 1 peduncle, dorsal view. B. Antenna 2 (peduncle and antennal scale), ventral view. C. Mandibles, left and right. D. Mandibular palp, lateral view. E. Labrum. F. Inner ramus of maxilla 1, posterior view. G. Distal part of maxilliped 1, posterior view. Scale bars: A–B, D = 0.25 mm; C, E–G = 0.2 mm.

Fig. 16. Siriella muranoi sp. nov., holotype, ♂, length 5.5 mm, Port Essington, Arafura Sea, Northern Territory, Australia. A. Anterior part of maxilliped 2, posterior view. B. Endopod of pereopod 1, posterior view. C. Endopod of pereopod 2, posterior view. D. Endopod of pereopod 3, posterior view. Scale bars: A = 0.2 mm; B–D = 0.25 mm.

Fig. 17. Siriella muranoi sp. nov., holotype, ♂, length 5.5 mm, Port Essington, Arafura Sea, Northern Territory, Australia. A. Endopod of pereopod 4, posterior view. B. Endopod of pereopod 5, posterior view. C. Endopod of pereopod 6, posterior view. D. Penis. E. Pleopod 3 (endopod not shown), lateral view. F. Pleopod 5 (endopod not shown), lateral view. G. Pleopod 5 (rami setae not shown), anterior view. Scale bars: A–D = 0.5 mm; E–G = 0.2 mm.

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