The basic plan of the crustacean endocrine system 1 The endocrine structures 2 X-organ-sinus gland complex 2 Postcommissural organ 3 Pericardial organ 3 Y -o rg a n .... ....... .. ...... ......... ... ......... 3 Androgenic gland 4 O vary 4 Mandibular organ 4 The roles of hormones 5

The endocrine mechanisms of crustaceans

SUMMARY This study investigates the involvement of eyestalk neuroendocrine factors
on osmoregulation in the crayfish Astacus leptodactylus maintained in
freshwater. Eyestalk removal was followed by a significant decrease in
hemolymph osmolality and Na + concentration and by a 50% increase in
mass after one molting cycle. Several neurohormones have been isolated from
the sinus gland through high-performance liquid chromatography (HPLC), and
different crustacean hyperglycemic hormone (CHH)-related peptides, including
stereoisomers (L-CHH and D-Phe 3 CHH), have been identified by
direct enzyme-linked immunosorbent assay (ELISA). A glucose quantification
bioassay demonstrated a strong hyperglycemic activity following injection of
the immunoreactive chromatographic fractions and showed that the
D-Phe 3 CHH was the most efficient. Destalked crayfish were then
injected with purified CHH HPLC fractions. The D-Phe 3 CHH fraction
significantly increased the hemolymph osmolality and Na + content 24
h after injection. Two other CHH-related peptides caused a smaller increase in
Na + concentration. No significant variation was observed in
hemolymph Cl - concentration following injection of any of the CHH
isoforms. These results constitute the first observation of the effects of a
CHH isoform, specifically the D-Phe 3 CHH, on osmoregulatory
parameters in a freshwater crustacean. The effects of eyestalk ablation and
CHH injection on osmoregulation and the identification of different
CHH-related peptides and isoforms in crustaceans are discussed.

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Putative involvement of crustacean hyperglycemic hormone isoforms in the neuroendocrine mediation of osmoregulation in the crayfish Astacus leptodactylus.

The effect of bilateral eyestalk ablation on haemolymph osmotic and Na+, Cl−, K+, Mg2+ and Ca2+ concentrations was investigated in the freshwater shrimp Macrobrachium olfersii during acute exposure (1, 3, 6, 12 and 24 h) to sea-water of 21% S. Analysis of variance treatment indicated that haemolymph osmotic and Na+, Cl−, K+, Mg2+ and Ca+ concentrations were affected by exposure time (p ≤ 0.01). However, only [Na+] was affected by eyestalk ablation (p < 0.01), destalked shrimps exhibiting haemolymph Na+ concentrations approximately 15 to 30% lower than control shrimps. These results are interpreted to indicate that less Na+ enters the haemolymph of eyestalkless shrimps on exposure to seawater of 21% S, presumably resulting from the absence of an eyestalk-located neurofactor. A factor causing the influx of Na+ into the haemolymph is thus proposed to be present in the eyestalk ganglionic system of intact Macrobrachium olfersii in freshwater. Reduction in secretion of the factor may act to reduce Na+ entry in high salt environments.

The effect of eyestalk ablation on haemolymph osmotic and ionic concentrations during acute salinity exposure in the freshwater shrimp Macrobrachium olfersii (Wiegmann)(Crustacea, Decapoda)

Relation entre osmorégulation et activités d'ATPase Na+ -K+ et d'anhydrase carbonique chez larves et postlarves de Homarus gammarus (L.) (Crustacea: Decapoda)

Involvement of the central nervous system in neuroendocrine mediation of osmotic and ionic regulation in the freshwater shrimp Macrobrachium olfersii (Crustacea, Decapoda).

The hemolymph ionic composition and unidirectional Na+ fluxes were analyzed in fiddler crabs (Uca) acclimated to 500 mosmol seawater. Eyestalkless crabs had lower hemolymph osmotic, Na+, and Cl- concentrations. The Na+ efflux was increased from 13.6 +/- 0.6 in control crabs to 19.6 +/- 1.3 mueq.g-1.h-1 in eyestalkless crabs; this increase was shown to be due to a higher Na+ permeability in eyestalkless crabs. Hemolymph Na+ in eyestalkless crabs was increased by an injection of eyestalk extract. The Na+ influx was increased from 11.1 in intact to 15.8 mueq.g-1.h-1 in eyestalkless animals. A kinetic study showed that 1) the influx was higher at all external Na+ concentrations in eyestalkless and intact-Na+-depleted crabs than in intact controls, and 2) the influx mechanism exhibited allosterism. The elevated Na+ influx in eyestalkless crabs was decreased by an injected eyestalk extract. An injected brain extract caused in increase in the Na+ influx in intact animals. It is concluded that the Na+ uptake mechanism is activated by decreasing the hemolymph Na+ concentration and that a brain hormone mediates the effect.

I. R. Hagadorn

Papers

Neuroendocrine control of Na+ balance in the fiddler crab Uca pugilator.