Myomenippe hardwickii

Myomenippe hardwickii (Gray, 1831)

(Plate 1a – g; Table 1)

Material examined

Single female specimen; voucher no. ESLDZRUBC1; dated 28.02.2021; collected from Hukitola Bay, in the proximity of mangroves (20°22.908 N, 86°47.462 E) of Jambu Kharnasi region, Odisha, India, from a depth of 3.96 m.

Synonyms

Cancer Hardwickii Gray, Zool Miscell, London: 40 (1831), type locality: Indian Ocean.

Menippe (Myomenippe) granulosa, Alcock, J Asiat Soc Bengal, 67 (2) (1898) pp. 179.

Menippe hardwickii, Deb, Zool Surv India, State Fauna Series 3: Fauna of West Bengal, Part, 10: 373 (1998).

Diagnosis

Carapace predominantly muddy brownish and pale yellow colored with a faint greenish tinge; shape oval, broader than long, slightly domed; well-defined regions on carapace evident, separated by shallow depressions and overlaid with several small granules. Gastric region distinguished into three portions-two anterolateral and one posterior. Raised portions of epibranchial region feature clusters of prominent vesciculous granules. Margin of carapace conspicuously granular. Anterolateral margins relatively thin and jagged, with four rather conspicuous teeth, separated by deep nicks; first three teeth close to the frontal region comparatively broad and anteriorly acuminate; last tooth short, narrow, and keeled. Low granular convexities seen on the anterolateral areas. Lateral regions of the carapace moderately undulated distinctly granular. Two ridged fragmented lines correspond with the curvature of anterolateral boundaries. Eyes green, ringed with red in fresh condition. Orbit wholly closed. Antennary flagellum excluded from the orbital gap. Frontal margin bilobed, approximately one-fourth of carapace breadth, separated from the orbit by a marked indent; each lobe has three teeth- one broad, squarish, pronounced, and the other two acuminate; third tooth, a little larger than the second. Third maxilliped rather large and fitted to buccal cavity. Both inner and outer margins of merus softly fuzzy. Hairy tufts on the inner apical region of carpus, propodus and dactylus. Chelipeds robust, right cheliped comparatively larger than the left; chela bulky, digits distinctly black, portly bearing serrated margins; bulbous molariform tooth present towards basal region of dactylus of larger chela. A contour of spaced-out granules extends from the distal end of the cheliped, culminating into tightly packed smaller granules towards the proximal inner slant of the cheliped. A minor spine stretches out from the curved carpus's inner corner; the outer surface of carpus grainy, pitted, and uneven with large vesciculous granules. Walking legs thin compared to chelipeds. Bristly exterior, joints profusely fringed with thin firm setae characterizing mainly margins of the upper four joints 8, 22, 23, 26, 29. Abdomen broad, flattened, consisting of seven distinct segments, sixth segment much wider than long, almost three times the length. Two pear shaped gonopore laterally present on sixth thoracic sternites.

Remarks

In contrast with the smooth carapace and chelipeds of Menippe rumphii, Myomenippe hardwickii has a much granular carapace and chelipeds. Further, each lobe of the bilobed front in the latter species has three teeth, differing from Menippe rumphii, with only two teeth in each lobe. In the fresh condition, the eyes of Menippe rumphii are red, while those of Myomenippe hardwickii are green, ringed with red.

Ecology

The specimen was recorded from a depth of 3.96 m with salinity 24.58 PSU; dissolved oxygen 5.32 mg /l; pH 8.2; water temperature 29 °C; sediment organic matter 2.19 % with silty sand texture (Sand – 10.76 %, Silt – 88.58 % and Clay – 0.66 %). The species cohabited with decapod crustaceans such as Penaeus sp., and Metopograpsus messor, besides molluscs for example Pirenella cingulata, Telescopium telescopium, Volegalea cochlidium, Indothais lacera, Tegillarca granosa, Placuna placenta, Vepricardium coronatum, and Paratapes textilis.