Siriella hanseni W.M. Tattersall, 1922

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 : 26-33

Siriella hanseni W.M. Tattersall, 1922

Figs 11–13

Siriella hanseni W.M. Tattersall, 1922: 448 , figs 1–2.

Siriella hanseni – Illig 1930: 561 (key). — Gordan 1957: 379 (catalogue). — Ii 1964: 577. — Pillai 1965: 1691. — Mauchline & Murano 1977: 76 (checklist). — Băcescu 1986: 19 (identity questionable). — Müller 1993: 38 (catalogue). — Lowry & Stoddart 2003: 467 (catalogue). — Hanamura 2007: 35, fig. 1. — Anderson 2010: 22 (checklist). — Naser et al. 2012: 379 (list). — Sawamoto 2014: 4 (list).

Non Siriella hanseni – O.S. Tattersall 1960: 167. — Murano 1998: 46, fig. 2b.

Diagnosis

Carapace with anterodorsal margin almost evenly rounded, well exposing subrostral process. Carapace dorsal surface not elevated. Telson 1.0–1.1 times as long as last abdominal somite; length 1.6–1.9 times anterior width; anterior width 1.3–1.6 times posterior width; lateral margins with three or four anterior and 10 to 16 posterior spiniform setae, gradually increasing in length, except for three to six terminal, which are nearly equal in length; terminal pair sometimes slightly longer than subterminal. Telson with terminal posterolateral pair of spiniform setae 0.08–0.13 times as long as telson and 1.0–1.2 times as long as subterminal. Subterminal pair of spiniform setae 1.0–1.2 times as long as preceding posterolateral pair. Telson apically without emargination, bearing three small and clearly visible spinules, about 0.2–0.3 times as long as posterolateral terminal spiniform setae. Labrum with very short anterior spine, barely visible, <0.1 times as long as rest of labrum. Maxilla 1 with apical robust smooth setae. Maxilla 2 endopod segment 2 with three or four distolateral setae. Pereopod 1–3 merus 3.5–4.4 times as long as wide. Uropodal exopod 3.5–4.4 times as long as wide; segment 1 is 1.9–2.3 times as long as segment 2, with three to six distolateral spiniform setae in both sexes. Uropodal endopod with 10 to 13 medial spiniform setae in both sexes, along almost entire margin, with terminal spiniform seta not reaching apex of ramus.

Type material

Lectotype (here designated)

INDIA: ♂, 5.5 mm long, “ Siriella Hanseni WMT, Pambon , Rammad District ” ( NHM 1921.12 .19.9; appendages on slide NHM 1921.12 .19.9).

Paralectotypes

INDIA: 2 ♂♂, 5.5 mm long, 2 ♀♀, 5.5 mm long, 1 ♀ (broken, immeasurable), same label data as for lectotype ( NHM 1921.12.10 –13); 2 ♂♂, 4.5–6.0 mm long, 1 ♂ (broken, immeasurable), 1 ♀, 5.5 mm long, 2 ♀♀ (broken, unidentifiable, immeasurable), “ Siriella hanseni WMT, Pambon, Rammad District, 0–2 fms” ( NHM 1964.1.21.6186–6190). All specimens more or less damaged, without appendages; some broken parts and embryos in the same tubes. W. M. Tattersall (1922) mentions 60 type specimens, 4–7 mm long. Only 12 specimens were deposited in the NHM, and the fate of other type material is unknown. A lectotype is designated here from a relatively well-preserved specimen to stabilize the nomenclature of the species.

Type locality

Indian Ocean, Laccadive Sea, Gulf of Manaar, India, Ramanathapuram District, Pamban (modern geographical names specified here).

Description

Body length 4–7 mm (W.M. Tattersall 1922). Males 4.5–6.0 mm long, females 5.5 mm long (available types). Specimens from Dampier Archipelago, Western Australia, 7.5 mm long ( Hanamura 2007).

Male (lectotype)

CARAPACE. Anterior part slightly wider than abdominal somite 1; anterior margin broadly and almost evenly rounded ( Fig. 11A ); dorsal surface smooth; posterior margin exposing three thoracic somites. Subrostral process spiniform, well-exposed.

TELSON. About 1.0 times as long as last abdominal somite and 0.7 times as long as uropodal endopod, with slightly tapering lateral margins ( Fig. 11C ); 1.9 times as long as wide anteriorly and 1.6 times as wide anteriorly as posteriorly; lateral margins with four anterior and nine short and four about equally long (three on the right side broken) posterior spiniform setae after gap; apically with three short spinules and two (one broken) long plumose setae, longer than spiniform setae flanking them, and about 0.3 times as long as subterminal spiniform setae. Telson apically not emarginated. Terminal posterolateral spiniform setae of telson 0.13 times as long as telson and 1.1–1.2 times as long as subterminal. Subterminal pair of spiniform setae 1.1 times as long as preceding pair of posterolateral.

HEAD APPENDAGES. Eyes 1.5 times as long as wide and 0.7 times as long as width of anterior part of carapace. Peduncle of antennae 1 ( Fig. 11E ) more robust than in female, about twice as long as peduncle of antenna 2; segment 1 is 1.7 times as long as wide; segment 3 twice as long as wide and 1.2 times as long as segment 1; male process along posteromedial margin of segment 3, conical, distally produced part 0.4 times as long as segment 3. Antennular inner flagellum normal, not dilated or meandering in proximal part. Antennal scale shorter than peduncle of antenna 1, reaching half-length of peduncle segment 3 ( Fig. 11A ), and 1.5 times as long as peduncle of antenna 2; scale 3.8 times as long as wide, 1.2 times as long as distance from scale base to base of outer spine ( Fig. 11F ). Labrum with very small, barely visible anterior spine, <0.1 times as long as rest of labrum ( Fig. 11G ). Mandible ( Fig. 11 I–J): incisor with two lamellar cusps, with planes perpendicular to each other; lacinia mobilis and molar lamellar; medial spines short, odontoid; palp segment 2 with about 10 setae along medial margin and six setae along lateral margin; palp segment 3 is 0.3 times as long as segment 2, with five long plumose proximal and seven short palmar setae ( Fig. 11H ). Maxilla 1 ( Fig. 12A ): outer ramus with about 10 smooth robust apical setae; inner ramus with 4 simple apical setae. Maxilla 2 ( Fig. 12B ): exopod oval, with 13 plumose, equally long setae; endopod segment 1 with two medial plumose setae; endopod segment 2 oval, larger than exopod, with three lateral setae and about 10 medial strong setae with setules, interspersed with simple long setae; endites with multiple, strong setae.

MAXILLIPEDS. Exopod of thoracopods 8–9-segmented. Maxilliped 1 endopod ( Fig. 12 C–D) without endites; segments short and strong; basis with one medial and a group of distomedial setae; preischium with one seta; ischium with three medial setae; merus, the largest segment, 1.2 times as long as wide, with seven medial and two distolateral setae; carpopropodus with distomedial and distolateral setae; dactylus with strong smooth unguis, four strong weakly serrated setae and about five simple setae. Maxilliped 2 endopod ( Fig. 12 E–F): basis with proximal medial seta and distal medial group of setae; preischium with one medial seta; ischium, the widest segment, 1.3 times as long as wide, with numerous setae along medial margin; merus two times as long as wide and 1.3 times as long as ischium, with three medial groups of two setae and two distolateral setae; carpopropodus 2.3 times as long as wide, with three distolateral setae, medial bunch of three long setae and distomedial bunch of three short setae; dactylus slightly longer than wide and 0.3 times as long as carpopropodus, with strong smooth unguis, four medial and three distal strong serrated setae; unguis 1.7 times as long as dactylus.

PEREOPODS. Pereopodal endopods ( Figs 12G , 13 A–D): preischium with one or two setae; ischium about half as long as merus; medial and paradactylary setae of carpopropodus distally serrated; carpopropodus secondary joint present, with 2 medial bunches of long setae; dactylus 1.3 times as long as wide and 0.2 times as long as carpopropodus; dactylus with strong unguis, 2.8 times as long as dactylus, and subungulary robust seta about half as long as unguis; dactylus together with unguis 0.5 times as long as carpopropodus; paradactylary setae exposing nearly half of unguis. Pereopods 1–3: basis with distomedial bunch of setae; ischium laterally strongly convex, about 2.5 times as long as wide, with one lateral seta and many short and long medial setae; merus 3.5–4.4 times as long as wide, with five medial groups of long and short setal bunches; carpopropodus about five times as long as wide and 0.9 times as long as merus. Pereopod 6 (paralectotypes) ( Fig. 13D ): ischium with parallel margins, 3.3 times as long as wide, with three medial setae and distomedial bunch of setae; merus about six times as long as wide, with three bunches of one or two setae; carpopropodus about 6.5 times as long as wide. Penis rather thin, slightly curved, with apical setae only ( Fig. 13E ).

PLEOPODS. Pleopod 1 uniramous ( Fig. 13F ); ramus 10-segmented; pseudobranchiae bilobate, nearly straight, with two basal setae.Pleopods2–5 biramous( Fig. 13G );rami11–12-segmented;pseudobranchiae bilobate, spirally coiled, with four basal setae. Terminal setae of pleopod rami not modified. Proximal segments of pleopod rami 0.6–0.8 times as long as wide.

UROPODS. Uropodal exopod 1.1–1.2 times as long as endopod and 3.8 times as long as wide; exopod segment 1 is 2.2 times as long as segment 2, with four distolateral spiniform setae ( Fig. 11K ). Uropodal endopod with 10 medial broadly set spiniform setae of about equal length, extending almost to ramus apex.

Female

Antennae 0.3 times as long as body. Peduncles of antenna 1 thin ( Fig. 11B ); segment 1 slightly longer than segments 2 and 3 together, with two distolateral bunches of one and two plumose setae; segment 2 with two distolateral and one distomedial plumose setae; segment 3 with bunch of two short lateral setae and two distomedial bunches of one and three long plumose setae. Segment 2 of antenna 2 peduncle 2.2 times as long as segment 3. Antennal scale about as long as peduncle of antenna 1. Marsupium with two pairs of oostegites. Pleopods reduced, uniramous.

Comparison

Siriella hanseni differs from all other species of the brevicaudata group by the armature of the posterior part of the telson: three to six nearly equally long apical spiniform setae, gradually transitioning into posterolateral spiniform setae. It most closely resembles S. lingvura and S. tabaniocula sp. nov., but differs from the former species, found only in Japan, by (1) telson length, which is 1.0–1.1 times as long as last abdominal somite (0.9 in S. lingvura ), (2) telson armature (terminal posterolateral pair of spiniform setae clearly longer than subterminal and other posterolateral in S. lingvura ), (3) labrum with shorter median spine (about 0.15 times as long as the rest of the labrum in S. lingvura ), (4) narrower pereopodal endopods (merus of pereopods 1–3 is 3.5 times as long as wide in S. lingvura ), (5) slightly narrower uropodal exopod (3.6–3.7 times as long as wide in S. lingvura ), (6) telson with three or four anterior lateral spiniform setae (against five or six in S. lingvura ) and (7) uropodal endopod with fewer spiniform setae (10 to 13 against 15 to 16 in S. lingvura ). Differences from S. tabaniocula sp. nov. can be seen in the comparison section for that species. Previously, S. hanseni was confused with S. muranoi sp. nov. (see differences in comparison section for S. muranoi sp. nov.). For comparisons of S. hanseni with other species of the brevicaudata group, see Table 1 .

Variation (other than diagnostic)

Eyes 1.2–1.5 times as long as wide. Antennal scale 3.3–3.8 times as long as wide.

Distribution

Except from the type locality in Laccadive Sea, Gulf of Manaar (W.M. Tattersall 1922), the only confirmed record is from the Dampier Archipelago, Western Australia ( Hanamura 2007). Considering the revised status of the species, a record from Channel Island, Beagle Gulf, Northern Australia ( Băcescu 1986), still requires verification, because no information on the specimens was provided ( Fig. 1 ).

Habitat

Seagrasses, 0– 12 m.

Remarks

The original description (W.M. Tattersall 1922) was not specifically detailed enough to adequately distinguish this species from the other members of the brevicaudata group. Based on examination of

the type specimens in the Natural History Museum in London, we present a detailed redescription of S. hanseni herein.

Tattersall’s description did not include such structures as the labrum, maxillae, anterior pereopods and others, which later proved to be taxonomically important ( Ii 1964; Murano & Fukuoka 2008; this study). He also failed to notice the joint between the segments of the antennal scale, the carpopropodus of the pereopodal endopods and between the dactylus and dactylary unguis of pereopod 1 (W.M. Tattersall 1922: fig. 1). Hence, Ii (1964), judging from Tattersall’s figures, considered the structure of the antennal scale and pereopods as diagnostic for S. hanseni in comparison with S. lingvura from Japan. The study of more material showed that it is not differentiated from S. lingvura by its telson width and the number of posterior lateral spiniform setae on the telson, as considered previously ( Ii 1964; Murano & Fukuoka 2008). Meanwhile, additional characters are reported here in the diagnosis distinguishing the two species.

A damaged specimen from the Arabian Gulf, partly described and figured by Murano (1998) and also mentioned in Murano & Fukuoka (2008) is distinguished from S. hanseni by the structure of the uropods and telson. In particular, the distal segment of the uropodal exopod is relatively shorter than in S. hanseni , the telson is shorter, and the terminal spiniforom setae of the telson longer (see details in Murano 1998). A similar structure of the uropod and telson can be found in an immature specimen from the Gulf of Kutch, northwest Indian coast of the Arabian Sea, illustrated by Biju (2008). The armature of the telson in both above mentioned cases is more similar to that in S. occulta sp. nov., but the distal segment of the uropodal exopod is 0.31–0.35 times as long as proximal segment (0.25–0.30 in S. occulta sp. nov.), and is, in fact, the shortest in the entire brevicaudata group. In addition, the illustrated specimen from the Gulf of Kutch lacks a subrostral process (not mentioned by Biju), as if it is covered by the carapace, also as in S. occulta sp. nov.

Specimens attributed to S. hanseni from Port Essington and the vicinity of Darwin in the Northern Territory during the late 1980 s were deposited in the Museum and Art Gallery of Northern Territory, Australia (NTM). Based on our comparison of these specimens with the type material of S. hanseni , they are attributed to a new species, Siriella muranoi sp. nov. within the brevicaudata group (described below).

Specimens from the Singapore Strait, identified as S. hanseni by O.S. Tattersall (1960), appear to be an identification error and belong to S. cf. chaitiamvongae Murano & Fukuoka, 2008 of the brevirostris group (see supplementary observations below). Thus, knowledge about S. hanseni is limited to the type locality and recent record from Dampier Archipelago ( Hanamura 2007).

Figures

Fig. 11. Siriella hanseni W.M. Tattersall, 1922, Laccadive Sea, Gulf of Manaar, India. A. Anterior part of body (right eye not shown). B. Anterior part of body (left eye not shown). C. Telson (two posterolateral subterminal spiniform setae missing). D. Telson, paralectotype. E. Antenna 1 peduncle, dorsal view. F. Antenna 2, lectotype, ventral view. G. Labrum. H. Mandibular palp, lateral view. I. Left mandible. J. Right mandible. A, C, E–J = lectotype, ♂, length 5.5 mm; B, D = paralectotype, ♀, length 5.5 mm. Scale bars: A–B = 1 mm; E–F, K = 0.5 mm; C–D, G–H = 0.25 mm; I–J = 0.1 mm.

Fig. 12. Siriella hanseni W.M. Tattersall, 1922, lectotype, ♂, length 5.5 mm, Laccadive Sea, Gulf of Manaar, India. A. Maxilla 1, posterior view, B. Maxilla 2, posterior view. C. Endopod of maxilliped 1, posterior view. D. Dactylus of maxilliped 1, posterior view. E. Endopod of maxilliped 2, posterior view. F. Dactylus of maxilliped 2, posterior view. G. Endopod of pereopod 1, posterior view. Scale bars: A–C, E, G = 0.25 mm; D, F = 0.1 mm.

Fig. 13. Siriella hanseni W.M. Tattersall, 1922, Laccadive Sea, Gulf of Manaar, India. A. Pereopod 2, anterior view. B. Endopod of pereopod 3, anterior view. C. Endopod of pereopod 5, anterior view. D. Endopod of pereopod 6, anterior view. E. Penis. F. Pleopod 1, anterior view. G. Pleopod 4, posterior view. A–C, E–G = lectotype, ♂, length 5.5 mm; D = paralectotype, ♂, length 5.5 mm. Scale bars: A–D, F–G = 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.