Growth and distribution of young Mesonychoteuthis hamiltoni Robson (Mollusca: cephalopoda): an antarctic squid

• Main Authors: Rodhouse, P. G., Clarke, M. R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Laboratoire Arago 1985
• Subjects: Antarctic; Southern Ocean; The Antarctic; Antarc*; Antarctic Squid; Mesonychoteuthis hamiltoni
• Online Access: https://oceanrep.geomar.de/id/eprint/34250/; https://oceanrep.geomar.de/id/eprint/34250/1/1119.pdf

Thirty seven juvenile specimens and one adult specimen of the cranchiid squid Mesonychoteuthis hamiltoni were captured by the opening and closing RMT8 net during RRS ‘Discovery’ cruise 100 (1979) in the Southern Ocean. The collection extends the size ränge of juveniles of this species previously described and illustrated. The small specimens resemble small juveniles of Galiteuthis glacialis, which also occur in most hauls, but are separated on the following characters : (a) M. hamiltoni lacks paired tubercles at the nuchal mantle fusion, (b) M. hamiltoni possesses a more capacious and thicker mantle, which is freer at the nuchal fusion and less constricted posterior to the opening; (c) juvenile M. hamiltoni up to a size of 26.5 mm (the largest in the present collection) have very small fins, while in G. glacialis of this size the posterior portion of the mantle has begun to extend into a tail and prominent fins appears; (d) M. hamiltoni has longer tentacles until it reaches a dorsal mantle length of approximately 25 mm. All specimens of M. hamiltoni were captured to the south of the Antarctic Convergence, and most were captured at depths between 20 m and 500 m apparently concentrated in the upper zone of ‘Warm Deep Water’ beneath the surface layer. Four newly hatched specimens were captured at 55°35’S between 20 and 500 m. The adult specimen was captured in a haul which had sampled a depth horizon from 2 000 m to 2 200 m.