Spiralothelphusa andhra, Pati & Mandal & Jaiswal, 2022

Pati, Sameer K., Mandal, Sudipta & Jaiswal, Deepa, 2022, Description of a new species of Spiralothelphusa Bott, 1968, and redescription of Spiralothelphusa wuellerstorfi (Heller, 1862) (Decapoda: Brachyura: Gecarcinucidae), European Journal of Taxonomy 798, pp. 1-29 : 18-24

Spiralothelphusa andhra sp. nov.

urn:lsid:zoobank.org:act:A02119B0-F118-48B2-BEF3-AC6A21B1D3E1

Figs 7L, N , 9–13

Carapace broader than long (CW/CL=1.3), deep ( CH /CL=0.6–0.7); dorsal surface strongly convex in frontal view; epigastric cristae well-developed, sharp, distinctly anterior to postorbital cristae; postorbital cristae sharp, almost straight to distinctly curved; external orbital angle triangular; epibranchial tooth distinct, sharp, above level of postorbital cristae; branchial regions gently inflated; cervical grooves shallow, narrow, discontinuous, not reaching to level of postorbital cristae; suborbital margin concave, discontinuous with supraorbital margin; frontal median triangle complete, as broad as frontal margin, lateral margins not joining dorsal margin; frontal margin medially gently concave in dorsal view; epistomal medial lobe with distinct, blunt tooth ( Figs 9A–C , 11A, C , 12A , 13 ). Eyes relatively large as compared to orbital space ( Fig. 9B ). Third maxilliped exopod with well-developed flagellum ( Fig. 9C ). Chelipeds generally smooth, subequal or unequal; chela with elongated dactylus and palm; carpus with long, narrow, sharp inner distal major tooth and very low sub-basal granule; merus lacking subterminal spine ( Figs 9A, D , 11A, C , 13 ). Ambulatory legs moderately stout, shorter than chelipeds ( Figs 9A, D , 11A, C , 13 ). Male S1 and S2 almost fused; male S2/S3 visible as shallow medial depression, not reaching lateral margins; male S3/S4 only visible as deep submedial depressions ( Figs 9D , 10A , 11D ). Male sternopleonal cavity reaching to imaginary line joining anterior part of cheliped coxae ( Figs 9D , 10A , 11D ). Male pleon narrowly triangular, with strongly concave lateral margins; somite 6 trapezoidal, relatively broader (proximal width circa 1.7 times medial length), with concave lateral margins ( Figs 7N , 9D , 10B ). Male telson slightly longer than pleonal somite 6, with almost straight lateral margins and broad apex ( Figs 7N , 9D , 10B , 11D ). G1 relatively slender, with tip gently hooked downwards; terminal segment and distal portion of subterminal segment longitudinally strongly twisted full turn, clockwise in left G1 and anticlockwise in right G1; twisted portion long, circa 0.6 times length of non-twisted portion; non-twisted portion with outer margin regularly, relatively more strongly curved, distinctly notched towards base ( Figs 7L , 10C, D , 11B, E ). G2 circa 1.0–1.1 times length of G1; distal segment long, circa 0.5 times length of basal segment ( Fig. 10E ).

Etymology

The species name, used here as a Latin noun in apposition, is after the Andhra Pradesh State of India.

Material examined

Holotype INDIA – Andhra Pradesh State • ♂ adult (CW 37.8 mm, CL 30.2 mm, CH 19.7 mm, FW 11.9 mm); Sri Potti Sriramulu Nellore District, Penna River, near Sangam Dam; 14.579° N, 79.487° E; alt. 56 m; 15 Dec. 2018; Boni Amin Laskar et al. leg.; GenBank: MN225969 ; ZSI-FBRC INV/2256 .

Paratypes INDIA – Andhra Pradesh State • 1 ♂, subadult (CW 15.1 mm, CL 11.5 mm, CH 7.5 mm, FW 5.2 mm); Sri Potti Sriramulu Nellore District, Penna River, near Jonnawada; 14.477° N, 79.863° E; alt. 19 m; 17 Dec. 2018; Boni Amin Laskar et al. leg.; GenBank: MN225972 ; ZSI-FBRC INV/2257 • 1 ♀, subadult (CW 13.3 mm, CL 10.7 mm, CH 6.8 mm, FW 4.3 mm); Sri Potti Sriramulu Nellore District, Penna River, near Nagarapamma Temple, Kolagatla ; 14.596° N, 79. 687° E; alt. 40 m; 15 Dec. 2018; Boni Amin Laskar et al. leg.; GenBank: MN225970 ; ZSI-FBRC INV/2258 • 1 ♂, subadult (CW 20.4 mm, CL 15.8 mm, CH 10.4 mm, FW 7.1 mm); Sri Potti Sriramulu Nellore District, Penna River, near Apparaopalem-Perumallapadu Bridge; 14.557° N, 79.625° E; alt. 46 m; 16 Dec. 2018; Boni Amin Laskar et al. leg.; GenBank: MN605600 ; ZSI-FBRC INV/2480 .

Description of male holotype

Carapace broader than long (CW/CL= 1.3), deep ( CH /CL=0.7); dorsal surface strongly convex in frontal view, smooth except for epigastric cristae, postorbital cristae and posterolateral surfaces; anterolateral margins gently convex, cristate, shorter than posterolateral margins; posterolateral margins medially concave; epigastric cristae well-developed, sharp, distinctly anterior to postorbital cristae; postorbital cristae sharp, almost straight, each sloping posteriorly towards anterolateral margin; external orbital angle triangular, with outer margin circa 2 times length of inner margin; epibranchial tooth distinct, sharp, above level of postorbital cristae; postorbital region concave; branchial regions gently inflated; cervical grooves shallow, narrow, discontinuous, not reaching to level of postorbital cristae; mesogastric groove deep, narrow, short, bifurcated posteriorly; H-shaped groove distinct; subhepatic region rugose; suborbital region rugose; pterygostomial region smooth except for few anteriorly located tubercles; supraorbital margin cristate, smooth, medially straight; suborbital margin concave, cristate, with very low tubercles, discontinuous with supraorbital margin; frontal median triangle complete, as broad as frontal margin, lateral margins not joining dorsal margin; front gently sloping downwards, subtrapezoidal; frontal margin smooth, cristate, broad (FW/CW=0.3), medially gently concave in dorsal view; epistomal medial lobe with distinct, blunt tooth ( Figs 9A–C , 13 ).

Eyes relatively large as compared to orbital space; eyestalk short, narrow, laterally concave; cornea large, pigmented ( Fig. 9B ).

Antennules long, folded in longitudinally broad fossae; antennae distally deformed but still long, equal in length to eyestalk ( Fig. 9B, C ). Mandibular palp 2-segmented; terminal segment bilobed. First, second maxillipeds each with long flagellum on exopod ( Fig. 9C ). Third maxillipeds cover most of buccal cavity when closed; ischium subrectangular, longer than broad, with deep, oblique submedial groove; merus subrectangular, broader than long, sunken; exopod moderately stout, distally narrow, longer than ischium, reaching proximal half of merus, with well-developed flagellum ( Fig. 9B–D ).

Cheliped generally smooth, almost equal. Chela with 15–18 blunt teeth on each finger, small gap when fingers closed; dactylus curved, slender, elongated; palm smooth, elongated; carpus slightly rugose on upper surface, gently inflated, with long, narrow, sharp inner distal major tooth and very low sub-basal granule; merus rugose, lacking subterminal spine ( Figs 9A, D , 13 ).

Ambulatory legs moderately stout, shorter than chelipeds, P3 longest, glabrous; merus (P2–P5) lacking subdistal spine; dactylus (P2–P5) gently recurved, subequal in length to propodus, with few distinct, sharp chitinous spines on margins ( Figs 9A, D , 13 ).

Thoracic sternites smooth, glabrous, punctate; S1 and S2 almost fused; S2/S3 visible as shallow medial depression, not reaching lateral margins; S3/S4 only visible as deep submedial depressions; S4/S5, S5/ S6, S6/S7 deep, narrow, medially interrupted; S7/S8 shallow, narrow, with medial transverse ridge, interrupting longitudinal groove ( Figs 9D , 10A ). Pleonal locking mechanism with prominent tubercle on submedial part of S5 ( Fig. 10A ). Sternopleonal cavity deep, long, reaching to imaginary line joining anterior part of cheliped coxae ( Figs 9D , 10A ).

Pleon narrowly triangular, with strongly concave lateral margins; somites 1, 2 narrower than somite 3; somite 3 broadest, with strongly convex lateral margins; somites 4, 5 trapezoidal, with straight lateral margins; somite 6 trapezoidal, broader than long (proximal width circa 1.7 times medial length), distinctly longer than preceding somites, with concave lateral margins ( Figs 7N , 9D , 10B ). Telson slightly longer than pleonal somite 6, longer than broad (medial length circa 1.2 times proximal width), with almost straight lateral margins and broad apex ( Figs 7N , 9D , 10B ).

G1 relatively slender, with tip gently hooked downwards, not reaching S5/S6; terminal segment and distal portion of subterminal segment longitudinally strongly twisted full turn, clockwise in left G1 and anticlockwise in right G1; twisted portion long, circa 0.6 times length of non-twisted portion; nontwisted portion with outer margin regularly but strongly curved, distinctly notched towards base; groove for G2 lateral ( Figs 7L , 10A, C–D ). G2 circa 1.0 times length of G1; distal segment long, circa 0.5 times length of basal segment ( Fig. 10E ).

Remarks

Spiralothelphusa andhra sp. nov. is unique among congeners due to the strongly concave (distinctly notched) outer margin of the G1 near the base ( Figs 7L , 10C–D , 11B, E ). In the G1 structure, S. andhra sp. nov. is most similar to S. wuellerstorfi in that both species possess a G1 with strongly, longitudinally twisted terminal segment and distal portion of the subterminal segment (fully turned clockwise in the left G1 and anticlockwise in the right G1), and the tip of the G 1 in them is gently hooked downwards ( Figs 4B–C , 6A–C , 7B, K–L , 10C–D , 11B, E ). Spiralothelphusa andhra sp. nov., however, is separated from S. wuellerstorfi by the almost straight lateral margins of the male telson ( Figs 7N , 9D , 10B , 11D ) (vs male telson with the concave lateral margins; Figs 3C , 7M ), and the regularly, relatively more strongly curved outer margin of the G1 non-twisted portion, which is distinctly notched towards base ( Figs 7L , 10C–D , 11B, E ) (vs G1 non-twisted portion with sharply, relatively less strongly curved outer margin, which is straight towards base; Figs 4B–C , 6A–C , 7B, K ).

The male paratypes (ZSI-FBRC INV/2257, 2480) of S. andhra sp. nov. are subadults but share most of the features of the carapace ( Fig. 11A, C–D ) with the male holotype. Their G1s possess the characteristically strongly concave outer margin towards the base ( Fig. 11B, E ). The following notable differences, however, are observed between the male paratypes and the male holotype. The postorbital cristae are distinctly curved in the larger male paratype (ZSI-FBRC INV/2480), i.e., each postorbital crista slopes posteriorly towards the postorbital region and then anteriorly towards the anterolateral margin ( Fig. 11A ) (vs almost straight postorbital cristae, each sloping posteriorly towards the anterolateral margin in the male holotype; Figs 9A , 13 ). This intraspecific variation raises doubt on the consistency or reliability of the shape of the postorbital cristae as one of the key characters for separating the species of Spiralothelphusa as used by Pati & Sudha Devi (2015). The smaller male paratype (ZSI- FBRC INV/2257) has a relatively broader telson, i.e., the medial length of the telson is almost equal to its proximal width ( Fig. 11D ) (vs relatively longer telson, with the medial length measuring about 1.2 times the proximal width in the male holotype; Figs 7N , 9D , 10B ).

The only female paratype (ZSI-FBRC INV/2258) of S. andhra sp. nov. is a subadult, which is similar to the male holotype in most of the non-sexual character states ( Fig. 12A ). Its pleonal somites and telson are subtriangular, which cover the thoracic sternum except for S1–S3 and lateral parts when closed ( Fig. 12B ). The pleonal somite 1 is the shortest; pleonal somites 2–5 are progressively longer; pleonal somite 6 is the longest, broader than long, as long as the telson, with the gently convex lateral margins ( Fig. 12B ). The telson is subtriangular, broader than long, with almost straight lateral margins ( Fig. 12B ). The vulvae on S 6 in the subadult female paratype are positioned apart from each other (VD/SW =circa 0.3), each opens ventrally, subovate, large (occupying circa 0.5 times length of S6), positioned some distance from S5/S6, and surrounded by a raised, broad rim ( Fig. 12C ).

Colour in life

Carapace, chelipeds and ambulatory legs all are brown with numerous purplish-brown spots on the dorsal surface ( Fig. 13 ). Their ventral surfaces are paler and spotless.

Ecological notes

Spiralothelphusa andhra sp. nov. was found among partly submerged long grasses (mostly Typha angustata Bory & Chaub., and Saccharum spontaneum Linnaeus) in the Penna river between the Somasila Reservoir and Nellore town of the Sri Potti Sriramulu Nellore District, Andhra Pradesh ( Fig. 14A–B ). Crabs were collected underneath pebbles in shallow water (depth <1 m) by scooping with a D-shaped aquatic net ( Fig. 14A–B ).

Geographical distribution

Spiralothelphusa andhra sp. nov. is known only from the lower reaches of the Penna River Basin in the Andhra Pradesh State, South India ( Fig. 8 ).

Figures

Fig. 7. Telson and G1 in Spiralothelphusa species showing diagnostic features. – A, F, I. Spiralothelphusa gibberosa Pati & Sudha Devi, 2015, holotype, ♂ (28.0 × 23.0 mm) (ZSI-WRC C.1186). – B, K, M. S. wuellerstorfi (Heller, 1862). B. ♂ (37.5 × 27.1 mm) (ZSI-WRC C.1960). K, M. Lectotype, ♂ (37.4 × 28.5 mm) (NHMW CR 27063). – C. S. hydrodroma (Herbst, 1794), topotype, ♂ (27.2 × 21.4 mm) (ZMUC CRU 2824). – D, G. S. senex (Fabricius, 1798), lectotype, ♂ (25.9 × 20.3 mm) (ZMUC CRU 4626). – E, H. S. fernandoi Ng, 1994, holotype, ♂ (35.7 × 26.5 mm) (ZRC 1984.7547). – J. S. parvula (Fernando, 1961), paratype, ♂ (19.4 × 15.0 mm) (ZRC 1984.7887). – L, N. S. andhra sp. nov., holotype, ♂ (37.8 × 30.2 mm) (ZSI-FBRC INV/2256). A–B. Left G1, apical view. C, L. Right G1, dorsal view (horizontally flipped). D–F, J–K. Left G1, dorsal view. G–I, M–N. Pleonal somite 6 and telson. Scale bars: A–F, J–L=1 mm; G–I, M–N =5 mm. C–E, G–H, J adapted from Ng & Tay (2001) and I is adapted from Pati & Sudha Devi (2015).

Fig. 9. Spiralothelphusa andhra sp. nov., holotype, ♂ (37.8 × 30.2 mm) (ZSI-FBRC INV/2256). A. Entire animal, dorsal view. B. Cephalothorax, frontal view. C. Cephalothorax, frontal view of medial part. D. Entire animal, ventral view. Scale bars: A–B, D = 10 mm; C =5 mm.

Fig. 10. Spiralothelphusa andhra sp. nov., holotype, ♂ (37.8 × 30.2 mm) (ZSI-FBRC INV/2256). A. Thoracic sternites with G1 in situ (right G1 removed). B. Pleon. C. Right G1, dorsal view. D. Right G1, ventral view. E. Right G2. Scale bars: A–B =5 mm, C–E= 1 mm.

Fig. 11. Spiralothelphusa andhra sp. nov. – A–B. Paratype, ♂ (20.4 × 15.8 mm) (ZSI-FBRC INV/2480). C–E. Paratype, ♂ (15.1 × 11.5 mm) (ZSI-FBRC INV/2257). A, C. Entire animal, dorsal view. B. Right G1, dorsal view. D. S1–S4 with telson. E. Left G1, dorsal view. Scale bars: A, C= 10 mm; D =2 mm; B, E=1 mm.

Fig. 12. Spiralothelphusa andhra sp. nov., paratype, ♀ (13.3 × 10.7 mm) (ZSI-FBRC INV/2258). A. Cephalothorax, dorsal view. B. Pleon. C. Thoracic sternites showing vulvae. Scale bars: A=2 mm; B–C =1 mm.

Fig. 13. Spiralothelphusa andhra sp. nov., holotype, ♂ (37.8 × 30.2 mm) (ZSI-FBRC INV/2256), colour of dorsal surface when freshly preserved. Scale bar =10 mm.

Fig. 4. Spiralothelphusa wuellerstorfi (Heller, 1862), lectotype, ♂ (37.4 × 28.5 mm) (NHMW CR 27063). A. Thoracic sternites with G1 in situ. B. Left G1, dorsal view. C. Left G1, ventral view. D. Left G2. Scale bars: A= 5 mm; B–D =1 mm.

Fig. 6. Spiralothelphusa wuellerstorfi (Heller, 1862). Dorsal view of left G1. A. ♂ (38.3 × 29.0 mm) (ZRC 2003.0243; formerly WHT 10749). B. ♂ (41.0 × 30.8 mm) (ZSI-WRC C.1995). C. ♂ (37.5 × 27.1 mm) (ZSI-WRC C.1960). Scale bars =1 mm.

Fig. 3. Spiralothelphusa wuellerstorfi (Heller, 1862), lectotype, ♂ (37.4 × 28.5 mm) (NHMW CR 27063). A. Entire animal, dorsal view. B. Cephalothorax, frontal view. C. Entire animal, ventral view. Scale bar =10 mm.

Fig. 14. HabitatsofSpiralothelphusa andhra sp.nov.inthe PennaRiver, nearApparaopalem-Perumallapadu Bridge of Sri Potti Sriramulu Nellore District, Andhra Pradesh, South India. A. Habitat dominated with Typha angustata Bory & Chaub. B. Habitat dominated with Saccharum spontaneum Linnaeus.

Fig. 8. Map of South India showing precise records of Spiralothelphusa wuellerstorfi (Heller, 1862) and collection sites of Spiralothelphusa andhra sp. nov.