Ontogenetic changes in size and shape of statoliths: implications for age and growth of the short-lived tropical squid Sepioteuthis lessoniana. (Cephalopoda: Loliginidae)

摘要

This study examined the relation between statolith and somatic growth in the tropical squid Sepioteuthis lessoniana. Five separate linear dimensions were measured on the statoliths of 103 individuals (17–245 mm mantle length). In addition the statoliths of 80 adults (82–245 mm mantle length) were weighed. Statolith increment analysis provided age estimates for 78 individuals. Statolith total length was correlated with age for squid less than ~60 days of age, although neither statolith total length nor weight was a useful predictor of age in older squid. Combining the five statolith dimensions to produce a description of statolith shape provided only slightly better estimates of age than statolith total length or weight alone. Statolith shape changed during ontogeny, developing from relatively elongate juvenile statoliths into the adult form with more robust dorsal and lateral domes. This development was reflected in wider spacing and superior optical definition of daily growth increments in the dorsal and lateral domes of adult statoliths, in relation to the slower growing rostrum. Growth of S. lessoniana statoliths does not appear to be strongly linked to mantle growth; both statolith total length and weight increase more slowly than mantle length.