Trapezionida bharuchai, Tiwari & Padate & Cubelio, 2023

Tiwari, Shivam, Padate, Vinay P. & Cubelio, Sherine Sonia, 2023, Chirostyloid and galatheoid squat lobsters (Decapoda: Anomura) from Andaman and Nicobar Islands, India, with three new species, Journal of Natural History 57 (9 - 12), pp. 520-556 : 546-550

Trapezionida bharuchai sp. nov.

( Figures 2 (f), 11, Supplementary Figure S4 )

Material examined

Holotype. Male (4.7 mm PCL, 3.9 mm CW) (IO/SS/ANO/00130), Andaman Sea, off Little Andaman Island, FORVSS stn 38806, 10.72°N, 92.70°E, 53 m depth, chain dredge, coll. Vinay P. Padate, 10 August 2019.

Paratypes. 1 female (3.6 mm PCL, 3.1 mm CW) (IO/SS/ANO/00131), same data as holotype; 1 male (5.1 mm PCL, 4.4 mm CW) (IO/SS/ANO/00132), Andaman Sea , off Great Nicobar Island, FORVSS stn 38818, 6.64°N, 93.82°E, 56 m depth, chain dredge, coll . Vinay P . Padate, 16 August 2019. 1 male (parasite attached to pleon) (4.6 mm PCL, 4.0 mm CW) (IO/SS/ANO/00154), south-eastern Bay of Bengal , off Car Nicobar Island, FORVSS stn 292II60, 9.28°N, 92.70°E, 50 m depth, Smith-McIntyre grab, coll . Aiswarya Gopal, 06 December 2011; 2 males (2.4–3.8 mm PCL, 2.2–3.1 mm CW) (IO/SS/ANO/00155), 2 ovigerous females (3.1–3.5 mm PCL, 3.4–3.8 mm CW) (IO/SS/ANO/00156), south-eastern Bay of Bengal , off Great Nicobar Island, FORVSS stn 292II86, 7.13°N, 93.54°E, 50 m depth, Smith-McIntyre grab, coll . Aiswarya Gopal, 11 December 2011.

Etymology

The species is named in honour of Dr. Erach Bharucha, a pioneer of environmental education in India.

Diagnosis

Carapace with main transverse ridges mostly uninterrupted; gastric ridges with 5 pairs of epigastric spines and 1 median spine; hepatic region with 1 or 2 spines; parahepatic, anterobranchial, postcervical regions each with 1 small spine; frontal margin strongly oblique; anterolateral spine not reaching sinus between rostrum and supraocular spines; branchial margins with 5 spines; posterior margin unarmed. Rostrum spiniform, half as long as PCL, supraocular spines one-fourth of rostral length. Pterygostomian flap with anterior margin terminating in 1 spinule. Thoracic sternite 4 with 1 pair of long oblique submedian striae and 1 pair of short submedian striae at midlength, anterior margin widely contiguous to sternite 3. Pleonal tergites 2–4 each with deep median groove, tergites 2 and 3 with 1 uninterrupted transverse ridge anterior and posterior to median groove, tergite 4 with 1 interrupted anterior ridge. Eye wider than sinus between rostrum and supraocular spine. Antennular peduncle article 1 bearing subequal distal spines, first lateral spine overreaching distal spines. Distomesial spine of antennal peduncle article 1 reaching distal margin of article 2; distomesial spine of article 2 not reaching distal margin of article 4, mesial margin with short spine, distolateral spine not reaching distal margin of article 3. Mxp 3 merus with 3 flexor spines, disto-extensor spine present. P1 length 3.5 times PCL, merus 5.2 times as long as wide, with 2 rows of 4–9 spines on dorsal surface, 2 rows of 3–4 spines on mesial face; palm 3.4 times as long as wide, dorsal surface with 6 spines, dorsomesial margin spinose; fingers 0.7 times as long as palm, fixed finger with 5 spines on dorsolateral surface, 2 subdistal spines on lateral margin, dactylus with short proximal spine, 2 spines on mesial margin and 2 subdistal spines. P2–4 smooth with iridescent setae on extensor margin; dactyli 0.6–0.7 times as long as propodi, flexor margins bearing 7 movable spines, distal tips corneous, with slender subterminal spine closely appressed to unguis.

Description of holotype

Carapace. PCL 1.2 times width, dorsal surface slightly convex transversely; main transverse ridges mostly uninterrupted; ridges and striae with dense short setae and a few longer setae. Gastric region with transverse row of 5 pairs of epigastric spines and 1 median spine. Cervical grooves distinct. Hepatic region with 1 or 2 spines; parahepatic, anterobranchial and postcervical regions each with 1 small spine; lateral part of posterior branchial region with 9 transverse ridges including posterior submarginal ridge. Intestinal region without distinct transverse stria. Frontal margins strongly oblique. Lateral margins moderately convex in dorsal view. Anterolateral spine not reaching sinus between rostrum and supraocular spines, followed by 1 or 2 distinctly shorter spines on anterolateral margin. Branchial margins with 5 spines ( Figures 2 (f), 11(a,b)). Rostrum spiniform, half as long as PCL, directed slightly upwards in lateral view; lateral margins slightly crenulated distally; supraocular spines short, slender, parallel in dorsal view, one-fourth length of rostrum ( Figures 2 (f), 11(a,b)). Pterygostomian flap with long and short transverse ridges, anterior margin terminating in 1 spinule ( Figure 11 (b)).

Sternum. Thoracic sternite 3 3.1 times as wide as long, half width of sternite 4; anterior margin undulate, granulate, with wide V-shaped median notch. Sternite 4 with 1 pair of oblique submedian striae anteriorly and 1 pair of transverse striae at midlength, anterior margin contiguous and equal to sternite 3 width ( Figure 11 (c)). Sternites 5–7 smooth, with row of short setae on anterior ridge.

Pleon. Smooth, tergites 2–4 with deep median transverse groove, tergites 2 and 3 each with 1 uninterrupted transverse ridge anterior and posterior to median groove, tergite 4 with interrupted anterior ridge only. Tergite 5 with uninterrupted anterior and posterior transverse ridges. Tergite 6 with 2 squamiform ridges, posterior ridge interrupted laterally ( Figure 11 (d)). Telson wider than long, with short squamiform ridges ( Figure 11 (e)).

Eye. Moderately large; cornea dilated, maximum diameter 3.8 times distance between rostrum and supraocular spine, about 0.3 times distance between anterolateral spines, 0.2 times PCL. Ocular peduncle with 1 stria on dorsal surface; eyelash long ( Figure 11 (a)).

Antennule. Antennular peduncle article 1 2.1 times as long as wide, overreaching distal corneal margin; distal spines subequal in length; lateral margin with 2 spines, first lateral spine distinctly overreaching distal spines, second lateral spine short, located anterior to midlength of article; ventral surface with a few scattered, short squamiform ridges ( Figure 11 (f)).

Antenna. Antennal peduncle not reaching distal margin of cornea. Article 1 with distomesial spine reaching distal margin of article 2. Article 2 with distomesial spine not reaching distal margin of article 4, mesial margin armed with short spine; distolateral spine not reaching distal margin of article 3. Articles 3 and 4 unarmed ( Figure 11 (f)).

Mxp 3. Ischium 1.6 times as long as merus, disto-flexor angle terminating in spine. Merus flexor margin with 3 spines, extensor margin with distal spine. Carpus, propodus and dactylus unarmed ( Figure 11 (g)).

P1. Length 3.5 times PCL, surfaces with numerous squamiform ridges of various sizes bearing short setae. Ischium with small spine on distolateral margin. Merus 5.2 times as long as wide, dorsal surface with 9 spines in lateral row, 4 spines in mesial row; mesial face with 4 spines in upper row, 3 spines in lower row; distal margin with 4 spines (dorsomesial, dorsolateral, ventrolateral, ventromesial spines; dorsomesial spine strongest, ventromesial spine smallest) ( Figure 11 (h)). Carpus 2.3 times as long as wide, 0.6 times as long as palm; dorsolateral margin with 4–6 spines; dorsal surface with 0–3 spinules; ventrolateral distal angle produced in rounded lobe, with 1 spine ( Figure 11 (h,i)). Palm 3.4 times as long as wide; dorsal surface with median row of 6 spines and 1 spine at dactylar articulation; dorsomesial margin with 7 spines; dorsolateral margin with 6 spines. Fingers 0.7 times as long as palm, terminating in sharp claws crossing distally; dorsal surfaces with scattered short setae. Fixed finger with 1 row of 5 spines on dorsolateral surface, 2 subdistal spines on lateral margin, occlusal margin denticulate, with 1 rounded tooth on proximal one-third portion ( Figure 11 (j)). Dactylus with short proximal spine, 2 subdistal spines on mesial margin, and 2 spines on dorsomesial surface ( Figure 11 (j)).

P2–4. P2 missing; P3–4 surfaces smooth with iridescent setae on extensor margin. P3 and P4 lengths 1.9 and 1.7 times PCL, respectively; meri with lengths 0.6 and 0.5 times PCL, respectively, 5.1 and 4.7 times as long as high, extensor margins with 8 spines, distal spine longest, flexor margin with 1 strong distal spine followed by 2 small spines and transverse ridges; P3 carpus extensor margin with 1 distal spine and 2 spinules, flexor margin with 1 distal spine, P4 carpus with only distal spines; propodi 6.7 and 6.4 times as long as wide, respectively, extensor margins unarmed, flexor margins with 14 and 10 movable spines, respectively; dactyli 0.6 and 0.7 times as long as propodi, respectively, flexor margins with 7 movable spines along entire margin, distal tips corneous, with slender subterminal spine closely appressed to unguis.

Variation in paratypes

PCL 1.1 times width. P2–4 with lengths 2.4, 2.1 and 1.8 times PCL, respectively; meri extensor margins with 6, 8 and 5 spines, respectively; P2–3 carpi extensor margins with 1 large distal, 3 small spines, P4 carpus with large distal spine; propodi flexor margins with 9, 10 and 9 spines, respectively; dactyli flexor margins with 7 movable corneous spines ( Figure 11 (k–m, q)).

Distribution

Presently known only from Andaman Sea, 53–56 m depth ( Figure 1 ).

Remarks

Trapezionida bharuchai sp. nov. shares the oblique frontal margins of carapace, large eyes, subequal distal spines of antennular peduncle article 1, unarmed antennal peduncle article 3, lobes of thoracic sternite 3 separated anteriorly by wide V-shaped notch, abruptly inclined anterolateral margins of sternite 4, and unarmed pleonal somites with T. clinata Macpherson, 1994 from Western Pacific Ocean, T. munin Komai, 2011 from Japan and T. roshanei Tirmizi, 1966 from Gulf of Oman.

The new species closely resembles T. munin in the armature of the third maxilliped and the presence of a slender subterminal spine closely appressed to the unguis of P2–4 dactyli ( Komai 2011). The new species can be distinguished from the latter in the following characters:

(1) Carapace lateral margins moderately convex in dorsal view (vs feebly convex in T. munin );

(2) Pterygostomian flap with anterior margin terminating in 1 spinule (vs unarmed in T. munin );

(3) Pleonal tergite 4 with interrupted anterior ridge only (vs anterior ridge and 3–4 striae in T. munin );

(4) Antennal peduncle article 2 bearing spine on mesial margin (vs unarmed mesial margin in T. munin );

(5) P1 palm 3.4 times as long as wide, dorsolateral margin with 6 spines (vs palm 2.8 times as long as wide; dorsolateral margin with 2–4 spines in T. munin );

(6) P1 fixed finger with 1 rounded tooth on proximal one-third portion of occlusal margin (vs rounded tooth absent proximally on occlusal margin in T. munin );

(7) P4 merus with 5 spines on extensor margin (vs P4 merus with disto-extensor spine only in T. munin ).

The new species closely resembles T. roshanei in the antennal peduncle article 2 with distomesial spine overreaching distal margin of article 3, and distolateral spine not reaching distal margin of article 3 ( Tirmizi 1966). The new species can be distinguished from closely related species in the following characters:

(1) Carapace lateral margins moderately convex in dorsal view (vs feebly convex in T. roshanei );

(2) Antennal peduncle article 2 with spine on mesial margin (vs mesial spine absent in T. clinata and T. roshanei );

(3) Distomesial spine of antennal peduncle article 2 overreaching distal margin of article 3, and distolateral spine not reaching distal margin of article 3 (vs distomesial spine overreaching distal margin of article 4, distolateral spine overreaching distal margin of article 3 in T. clinata );

(4) P2–4 dactyli with slender subterminal spine closely appressed to unguis (vs absent in T. clinata and T. roshanei ).

Figures

Figure 1. Map indicating collection sites of present specimens. 1, Gastroptychus valdiviae (Balss, 1913); 2, Grimothea krishaha sp. nov.; 3, Grimothea sp.; 4, Leptonida vigiliarum (Alcock, 1901); 5, Trapezionida aequispina sp. nov.; 6, Trapezionida bharuchai sp. nov.; 7, Leiogalathea sp.

Figure 2. Dorsal habitus. (a) Gastroptychus valdiviae (Balss, 1913). male, 6.0 mm PCL (IO/SS/ANO/ 00127); (b) Grimothea krishaha sp. nov. holotype, female, 3.5 mm PCL (IO/SS/ANO/00134); (c) Grimothea sp., female, 3.2 mm PCL (IO/SS/ANO/00143); (d) Leptonida vigiliarum (Alcock, 1901), male, 6.2 mm PCL (IO/SS/ANO/00133); (e) Trapezionida aequispina sp. nov. holotype, female, 7.0 mm PCL (IO/SS/ANO/00137); (f) Trapezionida bharuchai sp. nov. holotype, male, 4.7 mm PCL (IO/SS/ANO/ 00130); Leiogalathea sp., undetermined sex, 2.9 mm PCL (IO/SS/ANO/00126); (g) carapace, dorsal view; (h) P1, dorsal view. Scale bars: a, b, d–f, h = 2.0 mm; c, g = 1.0 mm.

Figure 4. Gastroptychus valdiviae (Balss, 1913). Male, 6.0 mm PCL (IO/SS/ANO/00127). (a) Right P1 ischium, lateral view; (b) right P1 merus, dorsal view; (c) right P1 carpus, dorsal view; (d) right P1 propodus, dorsal view; (e) right P1 fingers, dorsal view; (f) left P2 ischium-merus, lateral view; (g) left P2 carpus, lateral view; (h) left P2 propodus-dactylus, lateral view; (i) P3 ischium-merus, lateral view; (j) left P3 carpus, lateral view; (k) left P2 propodus-dactylus, lateral view; (l) left P4 ischium-merus, lateral view; (m) left P3 carpus,lateral view; (n) left P2 propodus-dactylus, lateral view; (o–q) left P2–P4 dactyli, lateral view. Scale bars: a, g, j, m = 1.0 mm; b–f, h, i, k, l, n = 2.0 mm; o–q = 0.5 mm.

Figure 11. Trapezionida bharuchai sp. nov. (a–j, n–p) Holotype, male, 4.7 mm PCL (IO/SS/ANO/00130). (k–m, q) Paratype, female, 3.6 mm PCL (IO/SS/ANO/00131). (a) Carapace, dorsal view; (b) carapace and pterygostomian flap, left lateral view; (c) thoracic sternites 3 and 4, ventral view;(d) pleonal tergites 2–5, dorsal view; (e) telson and left uropods, external view; (f) left antennular peduncle article 1 and antennal peduncle, ventral view; (g) left Mxp 3, lateral view; (h) right P1 merus and carpus, dorsal view; (i) right P1 carpus, ventral view; (j) right P1 propodus and dactylus,dorsal view; (k) right P2, lateral view; (l) right P3, lateral view;(m) right P4, lateral view;(n) right P5 dactylus, lateral view;(o) right G1, dorsal view; (p) right G2, dorsal view;(q) right P4 dactylar tip, lateral view.Scale bars:a, b, d–h, j–m = 1.0 mm; c, i, n = 0.5 mm; o–q = 0.2 mm.