MORPHOLOGY AND MICROSTRUCTURE OF THE GLADIUS AND STATOLITH FROM THE BOREAL PACIFIC GIANT-SQUID MOROTEUTHIS-ROBUSTA (OEGOPSIDA, ONYCHOTEUTHIDAE)

Morphology and microstructure of the gladius and statolith were studie d rom 11 specimens of the boreal Pacific giant squid Moroteuthis robus ta (mantle length (ML) ranging from 97.5 to 141.5 cm) captured on the slope of the north-west Bering Sea in summer and autumn 1993. The most specific feature of the M. robusta gladius is a large and, in cross-s ection, round rostrum which has been found to be homologous to that of extinct Belemnitida. The functional morphology of the different gladi us elements is discussed. Distinct growth increments have been reveale d in all three gladius layers in M. robusta. Comparison of peculiariti es of microstructure of growth increments, their ways of deposition an d their numbers in different gladius layers has shown that all three l ayers in the M. robusta gladius grow synchronously. M. robusta statoli ths are tiny (0.07-0.1% ML) and resemble in shape those of the ommastr ephid Illex argentinus. It was impossible to count the total number of growth increments within the statoliths, owing to their complete disa ppearance in the outer portion of the peripheral zone, and therefore i mpossible to estimate the age of the M. robusta by using the statolith ageing technique. However, assuming the deposition of growth incremen ts within the gladius as daily, the age of the specimens analysed may vary from 413 to 520 days.