EFFECT OF FEEDING ON THE STRUCTURE OF THE DIGESTIVE GLAND OF THE TROPICAL SEPIOID IDIOSEPIUS-PYGMAEUS

The digestive gland of the tropical sepioid Idiosepius pygmaeus (Steen strup) (Cephalopoda: Idiosepiidae) is characterized by a single cell t ype which secretes proteinaceous spherical bodies, the secretory spher es. Changes in the structure of the gland with feeding were investigat ed through a field sampling programme and a laboratory feeding experim ent. Specimens were collected in the field on three consecutive days. There was a significant increase in the number of spheres during the d ay. A laboratory-based night trial showed that numbers of secretory sp heres remained high during the night. After feeding there was a rapid and marked increase in the number of secretory spheres, suggesting tha t upon registering a stimulus the digestive gland secretes large amoun ts of enzymes. The process is rapid with an increase in the number of secretory spheres detected 30 minutes after feeding. The major peak in numbers of spheres occurred one hour after feeding. A second peak occ urred 16 hours after feeding, suggesting that there may be two phases to the digestive cycle. This study examined natural and experimental p atterns in the digestive gland and estimated the time involved in the digestive activity of I. pygmaeus.