AJP - Regulatory, Integrative and Comparative Physiology, Vol 263, Issue 3 472-R481, Copyright © 1992 by American Physiological Society
Invertebrate gut diverticula are nutrient absorptive organs
G. A. Ahearn, G. A. Gerencser, M. Thamotharan, R. D. Behnke and T. H. Lemme
Department of Zoology, University of Hawaii, Manoa, Honolulu 96822.
Physiological mechanisms of gastrointestinal absorption and secretion of
organic and inorganic solutes among invertebrates remain severely
underinvestigated. In this review we briefly discuss some of the physical
and biological forces affecting solute transfer across epithelial cells and
membranes of vertebrate and invertebrate guts. Next, we present some
features of the described processes for sugar and amino acid transport in
the tubular portion of gastrointestinal tracts of three major invertebrate
groups: echinoderms, molluscs, and arthropods. A detailed discussion
follows of recent nutrient transport studies using purified epithelial
brush-border membrane vesicles of two invertebrate gut diverticula, the
crustacean hepatopancreas and the starfish pyloric cecum. Lastly,
transepithelial nutrient and ion transport studies of crustacean
hepatopancreatic epithelial cell monolayers, grown in primary culture and
mounted in flux chambers, are used to demonstrate the nature of absorption
and secretion of solutes by this organ and to show the general
applicability of these methods to structurally complex invertebrate organs.
