ONTOGENY OF KINEMATICS IN THE GUT OF THE WHITE SHRIMP PENAEUS SETIFERUS (DECAPODA: PENAEIDAE)

Abstract

Motility of the gut in developmental stages of Penaeus setiferus (Linnaeus) was monitored in vivo with video microscopy. Oral drinking, anal drinking, and propagation of contractile waves in the midgut trunk (MGT) were observed in larval and postlarval stages. A gastric mill and functional gland filter were absent in larvae. In early postlarval stages, the gastric mill did not function in trituration. The gland filter appeared to function in emulsification rather than in exclusion of large-sized particles from the hepatopancreas. Chyme from within the peritrophic membrane, as far posteriad as abdominal segment 2, was moved at times anteriad into the hepatopancreas. Both antiperistaltic and peristaltic waves mixed and transported chyme within the midgut. Substantial ontogenetic change in function of the foregut and midgut occurred (1) at metamorphosis, (2) at onset of motility in the median tooth, and (3) with differentiation of hepatopancreatic tubules. We propose that antiperistalsis along the MGT, anal drinking, oral drinking, and contractions of the foregut maintain positive hydraulic pressure within the midgut. This pressure expands regions of the midgut following contractions of intrinsic muscles. Hydraulic pressure, particularly that propagated by antiperistalsis of the MGT, is responsible for expansion of contracted hepatopancreatic tubules. We further propose that the peritrophic membrane separates stored chyme and rejected fecal matter from water taken up by anal drinking and pumped anteriad by antiperistaltic waves. In P. setiferus hydraulic pressure in the extraperitrophic space of the midgut lumen, together with pressure exerted by constriction of the MGT in abdominal segments 3 and 4, compresses the peritrophic membrane around its contents. This compression expels fluids anteriad and compacts feces before the fecal strand reaches the hindgut.