Description of growth in the tropical cuttlefish Sepia elliptica using muscle tissue

Abstract

The mantle muscle tissue of cuttlefish is predominantly made up of circular muscle fibres which run around the body. This circular muscle tissue is divided into discrete blocks by radial fibres, which run perpendicular to the main axis of the body. Growth of mantle muscle tissue was described in the tropical cuttlefish Sepia elliptica by examining muscle block size and the density and size distribution of muscle fibres. Changes in these variables were assessed in juvenile and adult cuttlefish. Generation of new muscle fibres, both within new and existing muscle blocks, occurred as animals grew across the size range. Anterior muscle blocks were smaller than muscle blocks in the middle and posterior regions of the mantle, suggesting that new blocks were generated anteriorly. Muscle blocks were also created in the middle and posterior regions by division of existing large blocks into small blocks by generation of circular and radial muscle fibres. The examination of cuttlefish muscle growth dynamics provided an alternative way of assessing cephalopod growth mechanisms.