Galathea tirmiziae, Tiwari & Padate & Cubelio & Osawa, 2022

Tiwari, Shivam, Padate, Vinay P., Cubelio, Sherine Sonia & Osawa, Masayuki, 2022, Two new species of the genus Galathea Fabricius, 1793 (Crustacea: Decapoda Anomura: Galatheidae) from the Andaman Sea, India, Zootaxa 5219 (2), pp. 175-184 : 180-183

Galathea tirmiziae sp. nov.

urn:lsid:zoobank.org:act:00DAEA78-4A2A-4C17-A1E9-0E691DD153B1

( Figs. 2B , 4 )

Type material. Holotype: female ( IO /SS/ANO/00129; PCL 3.0 mm, CW 2.9 mm), Andaman Sea , off Little Andaman Island, FORVSS stn. 38806, 10.72°N, 92.7°E, 53 m depth, chain dredge, coll. Vinay P. Padate, 10 August 2019.

Diagnosis. Carapace with distinct transverse ridges; anterior protogastric ridge gently convex medially; scalelike median ridge behind anterior protogastric ridge; mesogastric ridge between anteriormost branchial marginal spines long but interrupted laterally; anterior metagastric ridge not medially interrupted; 2 epigastric, 1 hepatic, and 1 parahepatic spines; lateral margin with small spine between anterolateral spine and anteriormost spine of branchial margin; anterolateral spine not reaching tip of lateral limit of orbit; branchial margin with 5 spines. Rostrum 1.5 times longer than wide, triangular; lateral margins nearly straight, each with 4 deeply incised teeth. Pterygostomian flap unarmed on surface and upper margin. Antennular article 1 with 3 well-developed distal spines. Mxp3 merus with 2 subequal spines on flexor margin, disto-extensor margin unarmed. P1 fingers distally spooned. Epipods absent from P1–3.

Description. Carapace (PCL) approximately as long as wide; transverse ridges anteriorly bearing dense short setae, few scattered long non-plumose setae. Gastric region with 6 transverse ridges: 1 epigastric ridge with pair of spines; 2 protogastric ridges, anterior ridge uninterrupted, convex medially, bearing parahepatic spine laterally, posterior ridge short, scale-like; uninterrupted mesogastric ridge, not extending laterally to anterior-most branchial marginal spine; 2 metagastric ridges, anterior ridge not interrupted medially, extending laterally to anterior branchial ridge, posterior ridge short, scale-like. Mid-transverse ridge uninterrupted, preceded by shallow cervical groove, followed by 6 ridges including submarginal ridge, first and fifth ridges widely separated medially, second to fourth and sixth ridges uninterrupted. Hepatic region with 1 small spine behind anterolateral spine. Lateral margins gently convex, with 7 spines; first anterolateral, well-developed, not reaching tip of lateral limit of orbit; second spine minute, located at midlength between anterolateral spine and anteriormost branchial spine; 2 anterior branchial and 3 posterior branchial spines, last spine smallest. Lateral limit of orbit ending in distinct spine; infraorbital margin with strong spine ( Figs. 2B , 4A, B ). Rostrum 1.5 times longer than wide, length 0.4 times PCL, width 0.3 times CW; distance between distalmost lateral incisions 0.3 of that between proximalmost incisions; dorsal surface nearly horizontal in lateral view, bearing few setose scales; lateral margins nearly straight, each with 4 deeply incised sharp teeth ( Fig. 4A ).

Pterygostomian flap unarmed but with undulate ridges bearing short setae on surface; dorsal margin unarmed; anterior margin ending in small slender spine ( Fig. 4B ).

Sternal plastron 0.8 times as long as wide, lateral extremities gently divergent posteriorly. Sternite 3 2.2 times as wide as long; anterior margin minutely serrated, with 2 lobes separated by narrow median notch. Sternite 4 distinctly concave on anterior margin; anterior width distinctly larger than sternite 3 width; surface with pair of submedian striae anteriorly and short median stria posteriorly ( Fig. 4C ).

Abdominal tergites 2–4 each with 2 uninterrupted transverse ridges, anterior ridge corresponding to dorsoanterior margin. Tergites 5–6 each with 2 medially interrupted ridges ( Fig. 4A ). Tergite 6 with posteromedian margin nearly transverse ( Fig. 4D ). Telson wider than long, not distinctly subdivided, with scale-like striae ( Fig. 4D ).

Ocular peduncle 1.3 times as long as wide, maximum corneal diameter 0.7 rostrum width ( Fig. 4A ).

Antennular article 1 with 3 well-developed distal spines, distomesial spine subequal in size to distoventral spine, distodorsal largest ( Fig. 4E ). Ultimate article with few short fine setae not in tuft on distodorsal margin.

Antennal article 1 with distomesial spine reaching distal margin of article 3; article 2 with distomesial and distolateral spines reaching midlength of article 3; article 3 with small but distinct distomesial spine; article 4 unarmed ( Fig. 4E ).

Mxp3 ischium with small distal spine each on flexor and extensor margins, crista dentata with 23 denticles. Merus slightly longer than ischium (measured on lateral midline); flexor margin with 2 subequal spines; distoextensor margin unarmed. Carpus with low protuberances on extensor surface. Propodus moderately slender. Dactylus oblong ( Fig. 4F ).

P1 2.2 times PCL, covered with finely setose scales and with sparse long setae ( Fig. 4G ). Merus 0.6 times PCL, 1.6 times longer than carpus, with spines arranged roughly in row each on dorsomesial and dorsolateral margins; dorsomesial spines stronger, distalmost spine prominent; mesial surface with submedian spine; lateral surface with few small spines distally; ventral surface with spine each at distomesial and distolateral angles. Carpus 0.8 length of palm, 1.4 times width; dorsal surface with 2 and 3 spines on dorsomesial and dorsolateral margin, respectively; lateral surfaces with some small spines; mesial surface with 4 spines increasing in size distally, distal second largest. Palm 2.3 times as long as wide; dorsal surface with dorsolateral and dorsomesial rows of irregular spines; mesial and lateral margin each with row of larger spines, lateral row extending to fixed finger; lateral margin almost straight; mesial margin gently convex. Fingers 0.9 length of palm, spooned distally; opposable margins slightly gaping proximally, dactylus bearing 1 large tooth proximally; distal margins rounded, each with row of small blunt teeth; dactylus with dorsomesial row of sparse spinules ( Fig. 4G ).

P2–4 moderately slender, with setose striae and sparse long plumose setae ( Fig. 4H–J ). P2–4 2.1, 2.0, and 1.8 times PCL, respectively. Meri successively shorter posteriorly (P3 merus 0.9 times length of P2 merus, P4 merus 0.8 times length of P3 merus); P2 merus 0.7 times PCL, 5.3 times longer than high, 1.4 times P2 propodus length; extensor margins each with row of 5 (P4) and 6 (P2 and P3) proximally diminishing spines; flexor margins each with strong distal spine followed proximally by 1 small spine and few eminences; P4 lateral surface with 1 submedian spine adjacent to extensor margin. Carpi with extensor row of 4 spines on P2 and P3 and 1 disto-extensor spine on P4; distoflexor margins subacute. Propodi 4.1–4.3 times as long as high; extensor margins each with 2 small spines on proximal half; flexor margins with 5 (P3 and P4) and 6 (P2) corneous spines on P2, 5 spines on P3–4. Dactyli each ending in curved strong spine, length 0.7 of propodal length; flexor margins each with 5 (P3 and P4) and 6 (P2) proximally diminishing teeth, each tooth bearing slender corneous spine ( Fig. 4H–J ).

Epipods absent from P1–4.

Etymology. The species name honours the eminent crustacean taxonomist, Nasima Masoom Tirmizi, for her great contribution to the taxonomy of anomuran crustaceans in the Indian Ocean.

Remarks. Galathea tirmiziae sp. nov. is morphologically closest to G. consobrina De Man, 1902 from Vanuatu to Western Australia and Indonesia and G. tagaro Macpherson & Robainas-Barcia, 2015 from Vanuatu and the Solomon Islands (cf. Macpherson & Robainas-Barcia 2015). The three species share the following characters: carapace with distinct transverse ridges, including anterior protogastric ridge gently convex medially, scale-like median ridge behind anterior protogastric ridge, long but laterally interrupted anterior mesogastric ridge between anteriormost branchial marginal spines, and anterior metagastric ridge medially uninterrupted; two epigastric spines, absence of cardiac spines; lateral carapace margin with small but distinct spine between anterolateral spine and anteriormost spine of five branchial spines; rostrum triangular, with four deeply incised teeth; pterygostomian flap unarmed on upper margin; antennular article 1 with three well-developed distal spines; Mxp3 merus with 2 subequal spines on flexor margin; P1 fingers distally spooned; and epipod absent from P1. However, Galathea tirmiziae sp. nov. is distinguished from both of G. consobrina and G. tagaro by the Mxp3 merus without a distoextensor spine, which is present in the latter two species, the proportionally more slender P2 merus (5.3 vs 4.5 and 3.7 times longer than high in G. consobrina and G. tagaro , respectively), and the intermediate proportion of P2–4 propodi (4.1–4.3 times longer than high vs 3.5–4.0 times in G. consobrina and 4.5–4.8 times in G. tagaro ). Further, the new species differs from G. tagaro in the anterior margin of the thoracic sternite 4 being much wider than, rather subequal in width to the sternite 3, and the antennal article 3 with a small distomesial spine which is absent in the latter species.

Distribution. Presently only known from Andaman Sea, 53 m depth ( Fig. 1 ).

Figures

FIGURE 1. Map of the study area indicating collection sites in Indian EEZ. 1, Galathea nicobarica sp. nov.; 2, Galathea tirmiziae sp. nov.

FIGURE 2. Habitus, dorsal view. A, Galathea nicobarica sp. nov., holotype, ovigerous female (IO/SS/ANO/00144; PCL 3.8 mm, CW 3.6 mm); B, Galathea tirmizii sp. nov., holotype, female, (IO/SS/ANO/00129; PCL 3.0 mm, CW 2.9 mm). Scale bars: 2 mm.

FIGURE 4. Galathea tirmiziae sp. nov., holotype, female (IO/SS/ANO/00129; PCL 3.0 mm, CW 2.9 mm).A, carapace, dorsal view; B, carapace and pterygostomian flap, left lateral view; C, thoracic sternum, ventral view; D, telson, external view; E, right eye, antennular article 1 and antennal peduncle, ventral view; F, right Mxp3, lateral view; G, left P1, dorsal view; H–J, right P2–4, lateral view; K, right P5 dactylus, lateral view. Scale bars: A–B, G–J = 1.0 mm; C–F, K = 0.5 mm.