Eutrichocheles modestus (Herbst, 1796), 2012

Balakrishnan, S., Prakash, S. & Tudu, Prasad Chandra, 2021, First record of a rare Axiid Shrimp Eutrichocheles modestus (Herbst, 1796) (Malacostraca: Decapoda: Axiidae) from Northwestern Bay of Bengal, Records of the Zoological Survey of India 121 (1), pp. 11-16 : 12-14

Eutrichocheles modestus (Herbst, 1796) ( Figures 1 , 2A–E ).

1796. Cancer modestus Herbst, Versuch einer Naturgeschichte der Krabben und Krebse: nebst einer systematischen Beschreibung ihrer verschiedenen Arten: 173, pl. 43, Fig. 2 .

2011. Eutrichocheles modestus : Sakai, Crustacean Monographs, 13: 112, Figs. 19, 20, 21A-G.

Material examined: Single individual, male (CL 35 mm, TL 76 mm), Digha Mohana fish landing centre (21°37’19.4916’’N; 87°31’25.8276’’E), Northwestern Bay of Bengal , India, coll. S. Balakrishnan & Sukanto Ghosh, 21 st July 2019, MARC /ZSI/A6840 .

Diagnosis: Rostrum acutely triangular and denticulate on lateral margins, with supraorbital spine at rostral base, extending posteriorly onto anterior half of gastric region as lateral carinae with tooth. Gastric region bearing smooth median carina with hepatic tubercle, and sub median carinae with 6 spines. Telson longer than wide, bearing proximal lobewith spine followed by 4 spines on lateral margin, median notch with or without spine on posterior margin, and paired divergent carinae with spines on dorsal surface. Uropodalendopod broad and armed with teeth on lateral margin and bearing median carina with 4 teeth dorsally ( Figure 2 A-E).

Colour pattern: Body generally orange brown, lateral surface of carapace yellowish-white, abdomen with three thick (1 median and 2 lateral) longitudinal white bands, median band slightly wider from the second abdominal segment and decreasing towards the last segment Eyes dark brown. Pereiopods 1 whitish and densely covered with dark brown setae, bearing a subdistal red spot on merus. Pereiopods 3 reddish brown with white rings at articulations Colouration of telson and uropodslike abdomen bearing numerous dark brown setae on the posterior margins ( Figures 1 , 2 A-E).

Type locality: Indian Ocean

Distribution: India – Porto Novo (Balasubrahmanyan & Jacob, 1961; Sakai, 2011); Malacca; Malaysia – Pinang; Singapore; and Vietnam – Ha-tien ( Ngoc-Ho, 1998; Sakai, 2011).

Molecular Identification

The nucleotide BLAST analysis revealed that the sequence of E. modestus exhibited 84.01%identity with existing COI sequence of Axiid shrimp Leonardsaxius amurensis in the NCBI GenBank database. The detailed genetic divergence of E. modestus along with other closely related genera within the family Axiidae were provided. This indicates that the percent identity matrix revealed that E. modestus has a lesser identity of 75.98% to Axius stirynchus and a maximum of 82.76% identity to L. amurensis ( Table 2 ).

Lastly, our study was limited to only one individual from the Digha Mohana coast of Northwestern Bay of Bengal. Nevertheless, the information on the population assessment, species biology and ecology of E. modestus is still lacking. Extensive sampling protocols along with the integrative approach of both morphology and molecular techniques will provide insight on the taxonomic ambiguity in the current classification of E. modestus within the family Axiidae .

Figures

Figure 1. Burrowing shrimpEutrichocheles modestus (Herbst, 1796), male from Digha Mohana Fish Landing Centre, Northwestern Bay of Bengal (MARC/ZSI/A6840). Scale bar = 2 mm.

Figure 2. Burrowing shrimp Eutrichocheles modestus (Herbst, 1796). A, carapace, lateral view; B, postero dorsal region of carapace showing rostrum; C, abdominal pleura of third to fifth segment, lateral view; D, dactylus and fixed finger of major cheliped showing numerous setae; E, telson and uropods, dorsal view. Scale bar: A-B = 2 mm; C-E = 1 mm.