This study investigated the seasonal variation in the structure and secretory activity of the androgenic gland (AG) in the freshwater crab: Travancoriana schirnerae. The androgenic gland is an elongate structure, attached to one side on the wall of the ejaculatory duct. Histological studies showed the presence of three cell types, which differ in size, shape of nuclei, and presence or absence of secretory vesicles. Type I cells are small with large nuclei whereas type II cells are large with small nuclei. Type III cells are intermediate in size and exhibited streak-like nuclei and transparent cytoplasm. Seasonal changes were discerned in the morphology, histology and secretory activity of the gland. March-June appeared to be the active season with type II cells containing secretory vesicles. The mode of release of secretion found to be holocrine. The secretory activity almost completed by July-August (the mating season) with vacuolization of type II cells. The gland remained inactive from September-December with abundance of vacuoles, scattered pycnotic nuclei, indistinct cell membranes and total cellular degeneration. January-February was the revival period with type I cell proliferation. The present study revealed that the secretory activity of the gland is in tune with the male reproductive cycle.
A new species of freshwater crab, Spiralothelphusa gibberosa n. sp. is described from rice fields near Kizhoor in Thrissur district of Kerala in southern India. The new species is easily differentiated from its congeners by its first male pleopod (G1), which has a long, less strongly twisted terminal segment and distal portion of subterminal segment in addition to a setose hump on the outer margin of the non-twisted portion. Key to the species of the genus Spiralothelphusa Bott, 1968, is provided. We recognized S. wuellerstorfi (Heller, 1862), as a new record to Maharashtra based on specimens wrongly identified as S. hydrodroma (Herbst, 1794), by Pati & Sharma (2014).
The fine structure of the premoult Y organ in the freshwater crab Travancoriana schirnerae revealed elliptical epithelial gland cells with large, eccentric, multinucleolated nuclei and ample cytoplasm. The cytoplasm showed numerous polymorphic mitochondria with tubular cristae, highly anastomosed tubules and vesicles of smooth endoplasmic reticulum (SER), rich free ribosomes, small amounts of cisternae of rough endoplasmic reticulum (RER), microtubules and was devoid of Golgi complexes. Mitochondria were of two types the more abundant micromitochondria with electron dense matrix and the less abundant macromitochondria with moderately dense matrix. The tubular SER was particularly concentrated towards the basal region of the cell, intermingled with mitochondria and dense patches of free ribosomes while the vesicular SER lie close to the lateral plasma membrane. Large vesicles with flocculent substances, a few electron dense granules and multivesicular bodies could also be noticed in the gland cell cytoplasm. Aggregations of microvesicles which appeared close to the lateral plasma membrane, in association with dilated SER cisternae and microtubules, possibly suggest the intercellular exchange of substances. The plasma membrane beneath the basal lamina was composed of invaginations and the apical surface possessed numerous microvilli which serve to increase the surface area for metabolic exchange. Towards the apical region, the lateral plasma membrane of adjacent cells was linked by tight junctions. The presence of extraordinarily abundant tubular SER, high proportion of mitochondria with tubular cristae and rich free ribosomes could well be elucidated in favour of steroid production by the gland cells.
Kerala has the highest known diversity of freshwater crabs among the Indian states, and many more species are likely to be added to the state, especially from the Western Ghats. The present specimens from the Western Ghats of Kerala add two more species records to Kerala: Oziotelphusa wagrakarowensis (Rathbun, 1904) and Vanni nilgiriensis (Roux, 1931). Although O. wagrakarowensis was reported from the Indian states of Andhra Pradesh, Karnataka, and Maharashtra, it has not been recorded from Kerala previously. The present record of O. wagrakarowensis also constitutes the first reliable report of the species from the Western Ghats. The other species, V. nilgiriensis, was previously known from the Western Ghats of Karnataka and Tamil Nadu. Kerala now includes 37 species of gecarcinucid crabs with the addition of these two new records whereas the Western Ghats of India currently has 59 species.
Background: Freshwater crabs of the Western Ghats have been severely underestimated in their diversity. Since freshwater crabs have a small spatial scale endemism, many remote and poorly studied localities in the Western Ghats need to be surveyed. In this study, a new genus and new species is described. Results: Arcithelphusa cochleariformis gen. et sp. nov. is described from Ondayangadi, Wayanad district, Kerala, India. The new genus and new species is exceptional among Indian freshwater crabs due to its squarish, highly arched carapace, appearing box-like in frontal view, and long, stout, spoon-shaped male first gonopod.
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