No abstract

The capacity of organisms to change their sex has evolved independently in several species. Sex change has been widely studied, but research approaches have differed and conclusions have often been specific. Although sex allocation theory provides a unifying framework for the study of sex change, this unity has not always been appreciated, Environmental sex reversal (ESR), which results in a mismatch between genotypic and phenotypic sex, is well documented in numerous species and may be induced by chemical exposure. In the present study, an attempt was made to hypothesize the phenomenon of sex reversal in both Asian species (Tachypleus gigas and Carcinoscorpius rotundicauda) of the horseshoe crab in accordance with the size of the animals. Our findings suggest that both Asian species of horseshoe crabs ultimately show a positive sign of sex reversal phenomenon, however, this hypothesis needs further confirmation by studying the hormonal changes at all moulting stages of the horseshoe crab.

Horseshoe crab (Tachypleus gigas) is an archaic group of marine creature which plays a vital role in the saline ecosystem. Many researchers emphasize and enhance the knowledge about the horseshoe crab's basic biology, morphology, and ecology, whereas very little information is available about its population genetics. We attempted to develop a baseline database about the ecology, phylogeography, and genetic variation among the horseshoe crab population from Odisha, India. We collected 152 samples of horseshoe crab from the coastal area of the Bay of Bengal. The generated Cytochrome C Oxidase Subunit I gene (COI) sequences of T. gigas were compared with the sequences of T. gigas obtained from GenBank. The GenBank sequences were of two populations from South China and Malaysia. A total of 26 unique haplotypes were observed in three populations of T. gigas. Pairwise F-statistic distance (FST) between South China-India was 0.708; Malaysia-India was 0.608, and South China-Malaysia was 0.136. It indicated that the South China population was closely related to the Malaysian population and the Indian population was appeared to be genetically distinct from the other two populations. It signifies the ecological importance of the Indian population. Furthermore, the migrant per generation (Nm) was 0.16, which indicated a low gene flow among T. gigas populations. The haplotype diversity (Hd) and nucleotide diversity (π) were 0.58826 and 0.00476, respectively. This study would help lay future strategy and conservation of horseshoe crab across the Bay of Bengal.

No abstract

Horseshoe crab (Tachypleus gigas) is an archaic group of marine species which plays a vital role in the saline ecosystem. We attempted to develop a baseline database about the ecology, phylogeography, and genetic variation among the horseshoe crab population from Odisha, India. We collected 152 samples of horseshoe crab from the coastal area of the Bay of Bengal. The generated cytochrome c oxidase subunit I gene (COI) sequences of T. gigas were compared with the GenBank sequences of five populations from Bangladesh, Thailand, Singapore, South China, and Malaysia. A total of 33 unique haplotypes were observed in six populations of T. gigas. Pairwise F‐statistic distance (FST) between South China‐India, Malaysia‐India, Singapore‐India, Thailand‐India, and Bangladesh‐India were 0.021, 0.020, 0.017, 0.015, and 0.008, respectively. It indicated that the Indian and Bangladesh populations were genetically close and distinct from the other four populations. Furthermore, the migrant per generation (Nm) was 0.16, which indicated a low gene flow among T. gigas populations. The haplotype diversity (Hd) and nucleotide diversity (π) were 0.7482 and 0.00313, respectively. It signifies the ecological importance of the Indian population that would help in formulating the future strategy for the conservation of horseshoe crab.