The deep-sea crab Chaceon alcocki Ghosh & Manning, 1993 was recorded from the Arabian Sea off the Kollam coast, Kerala, India, in November 2015. A single female crab with 156 mm carapace width (CW), 146 mm carapace length (CL) and a total weight (TW) of 655 g, was collected from multiday trawl landings at the Sakthikulangara landing centre, Kollam, Kerala state. This species was first described by Ghosh & Manning in 1993, and the holotype, also a female crab, is kept in the Zoological Survey of India, Kolkata [formerly known as Calcutta].
Charybdis (Archias) omanensis septentrionalis Türkay & Spiridonov, 2006, has recently been recorded from the Arabian Sea, while the first record of the species was from the Red Sea. The specimens were collected in a shrimp trawl from a depth of 65-68 metres from the southwest coast of the Arabian Sea, off Kerala, India. The species size ranged between 17 and 37 mm carapace width, from 11 to 22.5 mm carapace length and in total weight between 0.39 and 5.53 g. The interrelationships between various morphometric characters, viz., carapace width and length and chelar propodus length and height in males, as well as carapace width and length and abdominal width and length in females, were estimated for the species and it was found that most relationships are positive and highly significant. In the carapace width/length-weight relationship, the estimated b values for carapace width-weight in males, females and pooled, were 2.674, 2.719 and 2.783, respectively, and for carapace length-weight they were 2.601, 2.588 and 2.681, respectively. The results show a significant deviation from an isometric growth pattern. An analysis of covariance indicated that there is a significant difference between sexes with respect to the carapace width/length-weight relationship. The relative condition factor values estimated in males and females were 0.9794 ± 0.16 and 1.1280 ± 0.26, respectively, also recording a significant variation () between sexes.
The portunid crab Lupocycloporus gracilimanus from Digha, Bay of Bengal, India was investigated for an infestation by the lepadomorph cirriped Octolasmis spp. About 93% of the epibionts examined were found attached to the surface of the carapace, abdomen and legs, and these were identified as Octolasmis warwicki (EOW). Only 7% of the epibionts were attached to the branchial lamellae, and these were identified as Octolasmis angulata (EOA). Twenty-seven O. warwicki were also found to have conspecific dwarf males (CDM) attached to the scutum: probably an adaptive strategy to maximize the total insemination. Both the epibionts and the CDM showed spatial preference for the posterior mesobranchial region of the carapace. Most of the CDM (27%) were seen as a single attachment on the epibiont. The distance between the epibiont and its nearest neighbour (DNN) was found to be strongly and negatively correlated (, ) with the number of epibionts, indicating its preference to stay in an intermediate-sized group rather than remain solitary, which probably would have facilitated the evolution of dwarf males (CDMs). A higher percentage of epibionts were observed to have attached CDMs when the DNN increased, and above the 25 mm DNN, all epibionts were having CDM attachments, which is believed to be a strategy to maximize the fertilization success of CDMs by reducing sperm competition. A strong, positive correlation (, ) was observed between the carapace width of the host crab and the numbers of the infesting epibionts, proving that the larger crabs are more susceptible to the infestation compared to the smaller ones. The sex ratio of the host crab was 1 : 5.5 (Male : Female), nevertheless, only the females were infested by the epibionts. The percentage of the prevalence, relative abundance and mean intensity of EOW infestation were recorded as 46.15%, 182.05% and 394.44%, respectively. None of the crabs had serious external or internal infestations that seemed to hinder the activities of the animal. This is the first report of the infestation of these Octolasmis species on the portunid crab Lupocycloporus gracilimanus from India.
Porcellana persica Haig, 1966 was collected from off the Kerala coast, Arabian Sea, India. This is the first record of both the genus and the species from Indian waters. The taxonomic characters are similar to the findings of Haig (1966), who described the species, and possibly this is the first detailed report on the species after her original description.
Charybdis (Goniohellenus) omanensis septentrionalis Türkay & Spiridonov, was collected from off the Kerala coast, Arabian Sea, India. This is the first record of the subspecies from India and the taxonomic characters are similar to the findings of Türkay & Spiridonov () who described the subspecies for the first time. The present work also records molecular sequences from the mitochondrial cytochrome oxidase I gene (COI), used to determine the genetic identity of the species.