Population variation and sexual dimorphism in the deep-sea crab Parilia alcocki (Brachyura, Leucosiidae)

ABSTRACT

Parilia alcocki is a deep-sea crab inhabiting the continental shelves and slopes of the eastern Arabian Sea and western Bay of Bengal at a depth of 128–457 m. No published information is available on its population characteristics and sexual dimorphism. The present study provides the first-ever insight into the population differentiation and sexual dimorphism in P. alcocki using Geometric Morphometric Analysis (GMA) of carapace and chela shapes. The Arabian Sea population possessed carapaces with a more pointed anterior and a rounded posterior margin as compared with the Bay of Bengal population. When chela shapes are compared, the Arabian Sea crabs possess an elongated, narrower arm, and shorter pollex. The observed shape variations could be attributed to heterogeneous habitat conditions in these regions which influence feeding and predation. Sexual dimorphism in carapace shapes was indiscernible. However, males exhibited wider intra-specific variations in carapace shape and show a larger average and maximum size for linear carapace measurements. Also, male crabs possess elongated and narrow arms and shorter pollex, whereas the females have a broader and shorter arm and longer pollex, indicative of classical sexual size dimorphism. Our study confirmed the suitability of GMA to understand the ecological and biological characteristics and trait-habitat linkages of P. alcocki.

KEYWORDS:

• Parilia alcocki
• Brachyura
• phenotypic variations
• Arabian Sea
• Bay of Bengal

Acknowledgements

The authors express their sincere thanks to the Secretary of the Ministry of Earth Sciences (MoES), New Delhi and the Director of the Centre for Marine Living Resources and Ecology (MoES), Government of India, for the cooperation and providing the facilities onboard FORV Sagar Sampada for the sample collection. We are very grateful to the chief scientists, fishing master, fishing hands and all participants of FORV Sagar Sampada for their valuable help for the sample collections. We are expressing our sincere gratitude to the two anonymous reviewers for critically evaluating the manuscript and for providing excellent suggestions which certainly enhanced the quality of the manuscript. The study was carried out as part of the in-house project ‘Resource Exploration and Inventorisation Systems (REIS)’ under the Marine Living Resource Programme of CMLRE, MoES. The financial, technical and logistical support from CMLRE is thankfully acknowledged. This is CMLRE contribution no XX.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Conflict of interest statement

Authors do not have any conflict of interest in publishing this manuscript.

Data availability statement

Data will be available on personnel request to the corresponding author.