Characterisation of an individual of the giant form of the purpleback flying squid Sthenoteuthis oualaniensis (Cephalopoda: Ommastriphidae) in the Arabian Sea and its biological descriptors

ABSTRACT

This paper describes a mated female of the giant form of purpleback flying squid Sthenoteuthis oualaniensis (545 mm dorsal mantle length and 5.46 kg body weight) caught in the Arabian Sea, with biological, morphological, and molecular descriptors. Based on the growth increments within statoliths, its age was found to be 203 days with a high growth rate of 2.68 mm DML/day. Its diet contained squids (72.3%) and fish (27.3%) with a high degree (70%) of cannibalism. The total fecundity of the individual was estimated as 702,240 eggs. Three species of parasites were found, two species of Platyhelminthes from the mantle cavity (Phyllobothrium sp. and Nybelinia sp.) and one of Nematoda from the stomach (Anisakis simplex). The COI barcode confirmed the identity of the giant form as S. oualaniensis, and the high genetic divergence (6.18–9.35%) that was observed between the current specimen and other forms from various oceans points to the probability that it might be a genetically distinct lineage from the northern Indian Ocean. The present record forms the southernmost (10°05′ N) record of the giant form of this flying squid.

KEYWORDS:

• Age and growth
• Arabian Sea
• fecundity
• purpleback flying squid
• parasites
• statolith

Acknowledgements

We are thankful to the Director of ICAR-CMFRI for facilities. Thanks to Dr N.K. Sanal, CMFRI for his dedicated support in the SEM session. We are also grateful to the fishermen for sharing the details of the location and other vital fishing information. We thank two anonymous reviewers for their comments on a previous version of the manuscript.

Disclosure statement

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

Additional information

Funding

This work was supported by Indian Council of Agricultural Research [grant number DEM/RMS/07].