— As a result of discussions among crustacean nutrition researchers at the annual meetings of the World Aquaculture Society (WAS) in 1984, feeding trials were conducted with over 22 different crustacean species to compare the potential use of two diets as Standard Reference Diets (SRD) in crustacean research. The two diets (BML 81 S, a casein/albumin based formula developed at the University of...

The modulatory actions of 5-hydroxytryptamine (5-HT) and octopamine (OA) were investigated in the opener nerve-muscle preparation of the crayfish, Astacus leptodactylus. Membrane resistance and resting potential were unaltered by 5-HT and OA at concentrations up to 2.5 X 10(-5) M; but EPSP-amplitudes were increased, up to 3-fold by OA and up to 18-fold by 5-HT. The lowest effective concentratio...

This study investigated the pattern of the electrical field potentials recorded near the prebranchial chamber of the native crayfish Astacus leptodactylus. Inside the prebranchial chamber, the electrical waves had maximal amplitude and showed 2-4 peaks per cycle. Potentials with the same frequency but smaller amplitude and simpler shape were also recorded outside the chamber, near the edge of t...

1. Efferent regulation of the activities of the slowly adapting and fast adapting stretch receptors (the MROX and MRO2l respectively) of Astacus fluviatilis was studied. 2. It was shown that the receptors activity is under the efferent control of two central inhibitory neurones: the main inhibitory neurone (MIN) and the accessory neurone (AIN). Their activities were determined by the degree of ...

Curve walking of crayfish Astacus leptodactylus was investigated by exploiting their optomotor response. The animal walked while spatially fixed on a motor-driven treadmill and turning behaviour was induced by an optical stimulus, a pattern consisting of vertical stripes moving in a horizontal direction. In this open-loop situation, the crayfish maintains the same step frequency for the legs on...

1. Contractures were evoked in isolated muscle fibres of the extensor carpopoditi muscle of the crayfish (Astacus fluviatilis) by increasing [K](o) at constant [Cl](o) or at constant [K](o)[Cl](o) product.2. The relation between tension and log [K](o) is S-shaped with a less steep slope if [K](o) was increased at constant [Cl](o). This is due to a smaller drop in membrane potential for a given ...

The effect of GABA on membrane potential and ionic currents of X-organ neurons isolated from the crayfish eyestalk was investigated. Under voltage-clamp conditions, GABA elicited an inward Na+ current followed by a sustained outward chloride current. Sodium current was partially blocked in a dose-dependent manner by antagonists of GABA plasma membrane transporters such as beta-alanine, nipecoti...

The present study examined the effects of two recently identified neuropeptides on crayfish hearts and on neuromuscular junctions of the crayfish deep abdominal extensor muscles. The two peptides, referred to as NF1 (Asn-Arg-Asn-Phe-Leu-Arg-Phe-NH2) and DF2 (Asp-Arg-Asn-Phe-Leu-Arg-Phe-NH2), increased the rate and amplitude of spontaneous cardiac contractions and increased the amplitude of exci...