Grimothea krishaha, 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 : 529-533

Grimothea krishaha sp. nov.

( Figures 2 (b), 6)

Material examined

Holotype. Female (3.5 mm PCL, 2.7 mm CW) (IO/SS/ANO/00134), Andaman Sea, off Car Nicobar Island, FORVSS stn 334II05, 9.29°N, 92.91°E, 315 m depth, Naturalist ̍s dredge, coll. Vinu Jacob, 28 January 2015.

Paratypes. 2 males (3.8, 3.8 mm PCL, 3.0, 3.2 mm CW) (IO/SS/ANO/00135), 1 female (3.1 mm PCL, 2.4 mm CW) (IO/SS/ANO/00136), same data as holotype .

Etymology

The species name is derived from the Sanskrit term ′ krśah ̍ meaning slender, denoting the relatively narrow carapace.

Diagnosis

Carapace with dorsal ridges mostly uninterrupted, a few ridges bearing long iridescent setae. Gastric region with 5 pairs of epigastric spines and 1 median gastric spine; hepatic, parahepatic, anterobranchial and postcervical regions each with 1 small spine; frontal margin slightly oblique; anterolateral spine reaching sinus between rostrum and supraocular spines; branchial margins with 5 spines; posterior margin unarmed. Rostrum spiniform, 0.4–0.5 times as long as PCL, supraocular spines 0.4 times as long as rostrum. Pterygostomian flap laterally inflated, partially visible in dorsal view, anterior margin terminating in 1 spinule. Thoracic sternite 4 with 2 short median striae and 1 pair of long submedian striae, anterior margin widely contiguous to sternite 3. Sternite 7 with granular patch laterally. Pleonal tergites 2–4 each with deep median groove, tergite 2 with 4 pairs of spines on 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. Antennal peduncle insertion visible in dorsal view, article 1 fused with lateral margin of epistome; distomesial spine of article 1 overreaching distal margin of article 2; distomesial spine of article 2 overreaching distal margin of article 4, mesial margin with short spine, distolateral spine overreaching distal margin of article 3. Mxp 3 merus with 2–3 flexor spines, extensor distal margin unarmed. P1 length> 2.0 times PCL, merus 5.5 times as long as wide, with 8 spines on dorsal surface, 2 spines on mesial margin, 3 spines on ventral surface; palm 3.0 times as long as wide, dorsal surface with 6–8 spines, dorsomesial margin spinose; fingers 1.3 times as long as palm, fixed finger with 3 spines on dorsolateral margin, 2 subdistal spines on lateral margin, dactylus with distinct proximal spine, 4 spines on mesial margin including subdistal spine.

Description of holotype

Carapace. PCL 1.3 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, parahepatic, anterobranchial and postcervical regions with 1 small spine; lateral part of posterior branchial region with 7 transverse ridges including posterior submarginal ridge. Intestinal region with short stria. Frontal margin slightly oblique. Anterolateral spine 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, second spine appressed to carapace); third spine smallest ( Figures 2 (b), 6(a,b)). Rostrum spiniform, half 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, 0.4 times as long as rostrum ( Figure 2 (b), 6(a,b)). Pterygostomian flap visible in dorsal view, with long and short transverse ridges, anterior margin terminating in 1 spinule ( Figure 6 (b)).

Sternum. Sternal plastron widest at sternite 7. Sternite 3 4.4 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 2 short median striae, 1 pair of short submedian striae, anterior pair shorter than posterior pair, anterior margin widely contiguous to sternite 3 width ( Figure 6 (c)). Sternites 5–6 smooth; sternite 7 with granular patch laterally ( Figure 6 (d)).

Pleon. Smooth, tergites 2–4 each with deep median transverse groove ( Figure 6 (a)); tergite 2 with 8 spines on anterior ridge; tergite 4 with 2 pairs of minute pits in anterior half portion; tergite 5 with 2 pairs of minute submedian pits alternating with 2 uninterrupted transverse ridges, posterior ridge longer; tergite 6 with 1 squamiform ridge interrupted medially and laterally. Telson wider than long ( Figure 6 (e)).

Eye. Moderately large; cornea dilated, well pigmented; maximum diameter 3.8 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 6 (a,b)).

Antennule. Antennular peduncle article 1 2.4 times as long as wide, distinctly overreaching distal corneal margin; distal spines subequal in length; 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 6 (f)).

Antenna. Antennal peduncle insertion visible in dorsal view, peduncle not reaching distal corneal margin. Article 1 fused with lateral margin of epistome ( Figure 6 (f)), distomesial spine overreaching 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 6 (f,g)).

Mxp 3. Ischium length 1.7 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, posterior spine distinctly longer, disto-extensor angle unarmed. Carpus to dactylus unarmed ( Figure 6 (h)).

P1–4. Missing.

Variation in paratypes

Female paratype with rostrum 0.4 times PCL. Ratio of width to length of thoracic sternite 3 3.8 in the smaller male paratype, 4.8 in the larger male paratype and 4.7 in the female paratype. Antennular peduncle article 1 2.1 times as long as wide in the female paratype. Mxp 3 ischium 1.9 times as long as merus in the smaller male paratype; larger male paratype with Mxp 3 merus bearing 3 spines on flexor margin.

Description of P1 of unknown host

Length> 2.0 times PCL (judging from available specimens), moderately slender, surfaces of merus to palm covered with distinct rows of squamae, bearing long iridescent setae. Ischium unarmed. Merus 5.5 times as long as wide; dorsal surface with 2 irregular rows of 8 spines increasing in size distally; mesial margin with 2 spines increasing in size distally; ventral surface with 1 row of 3 spines; distal margin with 4 spines (dorsal, mesial, ventromesial and lateral spines), dorsomesial spine strongest, ventromesial spine smallest; lateral margin unarmed. Carpus 2.5 times as long as wide, 0.8 times as long as palm; dorsal surface with 1 row of 4 spines; mesial margin with 3 spines, second spine largest, flanked by dorsomesial row of 3 spines; lateral margin unarmed; ventral surface unarmed, ventromesial margin with row of 3 spinules, ventrolateral distal angle produced in rounded lobe, armed with acuminate spine ( Figure 6 (i, k)). Palm 3.0 times as long as wide; dorsal surface with 1 row of 6–8 spines and 1 spine at dactylar articulation; ventral surface with 1 spine at dactylar articulation; dorsomesial surface with row of 6 spines; ventromesial surface with 4 spines, dorsolateral surface with 5 spines. Fingers 1.3 times as long as palm, terminating in sharp claws crossing distally; dorsal surfaces with scattered long setae; fixed finger with 1 row of 3 spines on dorsolateral surface, 2 subdistal spines on lateral margin, occlusal margin denticulate, with slightly larger teeth at regular intervals, 2 excavations along proximal half portion. Dactylus with distinct proximal spine, 4 well-spaced spines along mesial margin including subdistal spine ( Figure 6 (j, l)).

Distribution

Presently known only from Andaman Sea, 315 m depth ( Figure 1 ).

Remarks

Grimothea krishaha sp. nov. is assigned to Grimothea owing to the fusion of the antennal peduncle article 1 with the lateral margin of the epistome, and an unarmed, inflated pterygostomian flap visible in dorsal view (although the latter character is seen only in a few congeneric species) ( Machordom et al. 2022). Among the species recently transferred to Grimothea by Machordom et al. (2022), only G. lipkeholthuisi ( Hendrickx and Ayón-Parente, 2010) and M. macrobrachia ( Hendrickx, 2003) from the Eastern Pacific Ocean were relatively closely related to G. krishaha sp. nov. The new species shares with G. lipkeholthuisi the presence of a granular patch laterally on the thoracic sternite 7 and transverse row of spines on the anterior ridge of the pleonal tergite 2; and with G. macrobrachia the absence of spines on the posterior margin of carapace. However, the new species differs from G. lipkeholthuisi in the following characters:

(1) Epigastric spines 5 pairs (vs 3 pairs of spines in G. lipkeholthuisi );

(2) Posterior marginal ridge of carapace unarmed (vs 12 spines in G. lipkeholthuisi );

(3) Thoracic sternite 3 almost as wide as, and widely contiguous to, sternite 4 (vs narrowly contiguous in G. lipkeholthuisi );

(4) Pleonal tergite 2 with 4 pairs of spines on the anterior ridge (vs 7–8 pairs of spines in G. lipkeholthuisi );

(5) Pleonal tergites 3 and 4 with unarmed anterior ridge (vs 10 and 2 spines on tergites 3 and 4, respectively, in G. lipkeholthuisi );

(6) First lateral spine of the antennular peduncle article 1 distinctly overreaching distal spines (vs overreaching distomesial spine and not reaching distolateral spine in G. lipkeholthuisi );

(7) Antennal peduncle article 2 with 1 spine on mesial margin (vs absent in G. lipkeholthuisi );

(8) Distomesial spine of antennal peduncle article 2 overreaching distal margin of article 4 (vs not reaching distal margin of article 3 in G. lipkeholthuisi );

(9) Mxp 3 merus with 2 flexor spines, disto-extensor margin unarmed (vs 2 flexor spines, series of small spines including disto-extensor in G. lipkeholthuisi ).

Moreover, it differs from G. macrobrachia in the following characters:

(1) Epigastric spines 5 pairs (vs 2 pairs of spines in G. macrobrachia );

(2) Thoracic sternite 3 almost as wide as, and widely contiguous to, sternite 4 (vs thoracic sternite 3 wider than and not contiguous with sternite 4 in G. macrobrachia );

(3) Pleonal tergite 2 with 4 pairs of spines on the anterior ridge (vs unarmed in G. macrobrachia );

(4) First lateral spine of antennular peduncle article 1 distinctly overreaching distal spines (vs not reaching level of distal spines in G. macrobrachia );

(5) Distomesial spine of antennal peduncle article 2 overreaching distal margin of article 4 (vs not reaching distal margin of article 3 in G. macrobrachia );

(6) Mxp 3 merus with 2 flexor spines, disto-extensor margin unarmed (vs 2 flexor spines and additional spinules, disto-extensor spine present in G. macrobrachia ).

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 6. Grimothea krishaha sp. nov. (a–l) Holotype, female, 3.5 mm PCL (IO/SS/ANO/00134). (m–n) Paratype, 3.8 mm PCL (IO/SS/ANO/00135). (a) Carapace and pleonal tergites 2–4, dorsal view; (b) carapace and pterygostomian flap, left lateral view; (c) thoracic sternum, ventral view; (d) thoracic sternite 7 lateral portion, ventral view; (e) pleonal tergite 6 and telson, dorsal view; (f) right antennular peduncle article 1 and antennal peduncle, ventral view; (g) right antennular peduncle article 1 and antennal peduncle, dorsal view; (h) left Mxp 3, lateral view; (i) left P1 merus-carpus, dorsal view; (j) left P1 propodus-dactylus, dorsal view; (k) left P1 merus-carpus, ventral view; (l) left P1 propodus-dactylus, ventral view; (m) right P5 dactylus; (n) right G1, dorsal view; (o) right G2, dorsal view. Scale bars: a = 2.0 mm; b, e, i–l = 1.0 mm; c, d, f–h, m–o = 0.5 mm.