Changes in shape associated with growth in the loliginid squidPhotololigosp.: a morphometric approach

Abstract

This study examined growth of squid by describing changes in shape and relative size of body structures in juvenile and adult Photololigo sp. Animals change shape during growth because body structures increase in size at different relative rates. These changes are of particular interest because they are generally concomitant with changes in ecology. Length and mass measurements were taken from Photololigo sp. ranging in size from 2.77 to 117.03 mm dorsal mantle length. Small squid (< 50 mm dorsal mantle length) had round bodies with large head and eyes and poorly developed tentacles and arms. Larger squid (> 50 mm dorsal mantle length) were more elongate and narrow, and the head and eyes were proportionally smaller. As squid reached a dorsal mantle length of 50 mm, the changes in shape with growth become slower and individuals reached a final shape. Small individuals allocated energy predominantly in the arms and tentacles during early stages of growth, while the viscera and head grew at a much slower rate. Once individuals began producing gametic tissue and gonad growth occurred, the mantle muscle grew more slowly than the gonad. Changes in shape could be related to changes in locomotion and feeding that occur during ontogeny.