Grimothea sp.

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 : 534-536

Grimothea sp.

( Figures 2 (c), 7)

Material examined

1 female (3.2 mm PCL, 2.7 mm CW) (IO/SS/ANO/00143), south-eastern Bay of Bengal , off South Andaman Island, FORVSS stn 334I09, 11.79°N, 92.34°E, 147 m depth, Naturalist̍s dredge, coll . Vinu Jacob, 14 January 2015.

Description

Carapace. PCL 1.2 times width, dorsal surface gently convex transversely; main transverse ridges mostly uninterrupted; ridges and striae with dense short setae and a few longer iridescent setae. Gastric region with 5 pairs of epigastric spines and 1 median spine. Cervical grooves distinct. Hepatic region with 2 spines, posterior spine located adjacent to parahepatic spine; anterobranchial and postcervical regions each with 1 small spine; lateral part of posterior branchial region with 7 transverse ridges including posterior submarginal ridge. Intestinal region without stria. Frontal margin sinuous, strongly oblique, with sharp ridge running obliquely from lateral base of supraocular spine up to level of parahepatic spine. Anterolateral spine not reaching sinus between rostrum and supraocular spines, followed by 1 distinctly shorter spine on anterolateral margin. Lateral margins subparallel; branchial margins with 5 spines (3 on anterior branchial margin, third spine minute; 2 on posterior branchial margin); third spine smallest ( Figures 2 (c), 7(a,b)). Rostrum spiniform, 0.4 times as long as PCL, directed nearly horizontally in lateral view; dorsal surface sparsely covered with short scales, lateral margins slightly crenulated along distal portion; supraocular spines moderately long, slender, parallel in dorsal view, half as long as rostrum ( Figures 2 (c), 7(a,b)). Pterygostomian flap inflated, partially visible in dorsal view, with long and short transverse ridges, anterior margin terminating in 1 spinule ( Figure 7 (a,b)).

Sternum. Sternal plastron widest at sternite 7. Thoracic sternite 3 4.8 times as wide as long, 0.4 times as wide as sternite 4; anterior margin serrated, with 2 sinuous lobes separated by wide V-shaped median notch. Sternite 4 with anterior margin contiguous to sternite 3 along half of its length. Sternites 4–6 smooth; sternite 7 lateral portion with granular patch ( Figure 7 (c)).

Pleon. Smooth, tergites 2 and 3 each with deep median transverse groove; tergite 2 with 8 spines on anterior ridge ( Figure 7 (a)); tergite 4 smooth, with 1 pair of minute submedian pits anteriorly; tergite 5 with 2 pairs of minute submedian pits alternating with 2 uninterrupted transverse ridges, posterior ridge longer; tergite 6 with 1 medially interrupted squamiform ridge. Telson wider than long ( Figure 7 (d)).

Eye. Moderately large; cornea dilated, lightly pigmented; maximum diameter 4.2 times distance between rostrum and supraocular spine, 0.4 times distance between anterolateral spines, 0.3 times PCL. Ocular peduncle without striae on dorsal surface; eyelash short ( Figure 7 (a)).

Antennule. Antennular peduncle article 1 2.2 times as long as wide, distinctly overreaching distal corneal margin; distomesial spine shorter than distolateral spine; lateral margin with 2 spines, first lateral spine distinctly overreaching distal spines, second lateral spine very short, located anterior to midlength of article; ventral surface with a few scattered, short squamiform ridges ( Figure 7 (e)).

Antenna. Antennal peduncle insertion visible in dorsal view, peduncle not reaching distal corneal margin. Article 1 fused with lateral margin of epistome ( Figure 7 (e)), distomesial spine reaching distal margin of article 2. Article 2 with distomesial spine overreaching distal margin of article 4, mesial margin armed with short spine; distolateral spine overreaching distal margin of article 3. Articles 3 and 4 unarmed ( Figure 7 (e, f)).

Mxp 3. Ischium length 1.8 times as long as merus, disto-flexor and disto-extensor angles terminating in sharp spine; crista dentata with 20–21 denticles. Merus flexor margin with 2 spines, proximal spine located at midlength distinctly longer, disto-extensor angle unarmed. Carpus, propodus and dactylus unarmed ( Figure 7 (g)).

P1–4. Missing.

Distribution

Presently known only from Andaman Sea, 147 m depth ( Figure 1 ).

Remarks

The unidentified specimen is here assigned to Grimothea because of the fusion of the first antennal peduncle article with the lateral margin of the epistome, and the unarmed, inflated pterygostomian flap visible in the dorsal view (although the latter character is seen only in a few congeneric species) ( Machordom et al. 2022). Like G. krishaha sp. nov., this specimen is morphologically close to G. lipkeholthuisi ( Hendrickx and Ayón-Parente, 2010) and M. macrobrachia ( Hendrickx, 2003) from the Eastern Pacific Ocean.

Further, Grimothea sp. differs from G. krishaha sp. nov. in the following characters:

(1) Carapace with 2 hepatic spines (vs 1 spine in G. krishaha sp. nov.);

(2) Frontal margin sinuous, strongly oblique with sharp ridge running obliquelyposteriorly from lateral base of supraocular spine to parahepatic spine (vs frontal margin slightly oblique, without sharp ridge in G. krishaha sp. nov.);

(3) Anterolateral spine not reaching sinus between rostrum and supraocular spines (vs reaching sinus in G. krishaha sp. nov.);

(4) Pleonal tergites 2–3 with deep median transverse groove; tergite 4 smooth (vs tergites 2–4 with deep median transverse groove in G. krishaha sp. nov.);

(5) Distomesial spine of antennular peduncle shorter than distolateral spine (vs distal spines subequal in length in G. krishaha sp. nov.).

In addition to the above, it resembles G. lipkeholthuisi in the presence of a granular patch laterally on thoracic sternite 7 and a transverse row of spines on pleonal tergite 2. Moreover, it shares the absence of spines on the posterior margin of carapace with G. macrobrachia . Morphological differences from the Eastern Pacific species are mentioned above in the ′Remarks̍ for G. krishaha sp. nov.

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 7. Grimothea sp., female, 3.2 mm PCL (IO/SS/ANO/00143). (a) Carapace and pleonal tergites 2–4, dorsal view; (b) carapace and pterygostomian flap, right lateral view; (c) thoracic sternum, ventral view; (d) pleonal tergite 6 and telson, dorsal view; (e) left antennular peduncle article 1 and antennal peduncle, ventral view; (f) left antennular peduncle article 1 and antennal peduncle, dorsal view; (g) left Mxp 3, lateral view. Scale bars: a, c, d = 1.0 mm; b = 2.0 mm; e–g = 0.5 mm.