4 – Functional Aspects of Nutrition and Digestion

Physiological mechanisms of gastrointestinal absorption of organic solutes among crustaceans remain severely underinvestigated, in spite of the considerable relevance of characterizing the routes of nutrient absorption for both nutritional purposes and formulation of balanced diets in aquaculture Several lines of evidence attribute a primary absorptive role to the digestive gland (hepatopancreas) and a secondary role to the midgut (intestine) Among absorbed organic solutes, the importance of D-glucose in crustacean metabolism is paramount Its plasma levels are finely tuned by hormones (crustacean hyperglycemic hormone, insulin-like peptides and insulin-like growth factors) and the function of certain organs (ie brain and muscle) largely depends on a balanced D-glucose supply In the last few decades, D-glucose absorptive processes of the gastrointestinal tract of crustaceans have been described and transport mechanisms investigated, but not fully disclosed We briefly review our present knowledge of D-glucose transport processes in the crustacean hepatopancreas A discussion of previous results from experiments with hepatopancreatic epithelial brush-border membrane vesicles is presented In addition, recent advances in our understandings of hepatopancreatic D-glucose transport are shown, as obtained (1) after isolation of purified R-, F-, B- and E-cell suspensions from the whole organ by centrifugal elutriation, and (2) by protein expression in hepatopancreatic mRNA-injected Xenopus laevis oocytes In a perspective, the applicability of these novel methods to the study of hepatopancreatic absorptive function will certainly improve our knowledge of this structurally complex organ

D-glucose transport in decapod crustacean hepatopancreas.

We studied the mechanism(s) by which a deposit feeder can solubilize PAH from contaminated sediments as well as the implications of these mechanisms for factors controlling PAH bioavailability. Arenicola marina digestive fluids solubilize 4.6 μg mL-1 phenanthrene and 2.0 μg mL-1 benzo[a]pyreneconcentrations greater than the PAH's seawater solubilitieswhen incubated with pure PAH solids. This enhanced solubilization is largely due to surfactant micelles in the digestive fluid. In experiments with contaminated sediments that repeat the incubation or vary the solid−fluid ratio, these and other PAHs saturate at much lower concentrations (often between 0.01 and 0.1 μg mL-1). Less solubilization is likely due to sorption of digestive surfactants by sedimentary organic matter and competition from other sedimentary hydrophobic solutes, such as aliphatic hydrocarbons, for remaining micellar space. Nevertheless, gut fluid concentrations of high molecular weight PAHs are greater than those predicted from equilibrium...

Dissolution of Sedimentary Polycyclic Aromatic Hydrocarbons into the Lugworm's (Arenicola marina) Digestive Fluids

A successful purified diet for the culture of juvenile lobsters: The effect of lecithin

Chapter 16 – Digestive Physiology and Nutrition

Although crustacean tissue cholesterol content is high, Crustacea, like other arthropods; are incapable of cholesterol synthesis, and presumably are dependent for maintaining tissue cholesterol stores on the intestinal absorption of ingested sterol. A detergent, N-(N-dodecanoylsarcosyl)taurine, representative of a set of detergents synthesized by the crustacean hepatopancreas and secreted into the intestine, is capable of efficient cholesterol solubilization, and thus of promoting sterol absorption.

http://science.sciencemag.org/content/sci/189/4208/1098.full.pdf

Dowd

Papers

Crustacean intestinal detergent promotes sterol solubilization.