The aim of this study was to determine seasonal differences in the temperature dependence of neuromuscular parameters of the dactylopodite walking leg closer muscle in two species of freshly caught summer and winter decapod crabs. The relatively stenothermal Cancer pagurus (Cp) and eurythermal Carcinus maenas (Cm) muscle resting potential (RP) hyperpolarised significantly with increasing experimental temperature. The muscle RP in Cm was seasonally dependent at acute temperatures above 20 °C whereas in Cp no seasonal effect was observed. The latent period of the muscle excitatory junction potential (EJP) following tonic motor nerve stimulation was significantly longer in winter-caught crabs in both species, although the effect was significantly more marked in Cp than Cm. Summer-caught Cp had larger excitatory junction potentials (EJPs) than did winter-caught crabs, a seasonal effect not seen in Cm. In contrast, marked seasonal differences were found in the EJP decay time constant in Cm having significantly longer time constants in winter-caught crabs, where no seasonal difference was found in Cp. These results suggest that different seasonal effects of neuromuscular parameters between Cm and Cp may reflect different strategies of response to their different seasonal temperature environments.
Critical thermal maxima (CTMax) and minima (CTMin) were determined for the blue crab, Portunus pelagicus acclimated at 15, 20, 25, 30, and 35° ± 1°C. The CTMax of blue crabs at those acclimation temperatures were 38.17, 39.08, 40.07, 41.26, and 42.66°C, respectively. The corresponding CTMin values were 12. 28, 12.57, 14.84, 16.34, and 16.57°C, respectively. The zone of thermal tolerance assessed using the CTMax an(f CTMin boundaries was 519.7°C2. Acclimation response ratios ranged between 0.05 and 0.28.
A total of 27 fatty acids (FAs) were identified in testis throughout the spawning season of male R. sarba. In male gonad saturated fatty acids (SFA) were the main fatty acid group in total lipid in testis (34%) followed by PUFA (29.1%) and MUFA (11.6%). In all maturation stages SFA were the main fatty acid group in testis (30.4-35.4%). Of individual fatty acid, the major constituents of SFA were Palmitic acid C16:0 (18. 5%) and Stearic acid C18:0 (8.5%) in nearly ripe and ripe stages respectively. Oleic acid C18:1 (8.8%) was found to be the main MUFA in ripe stage and Linoleic acid C18:2 (10.8%) was the main PUFA in nearly ripe stage. During spawning and maturation stages there were a significant differences in total SFA and MUFA (P<0.05).
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