Effects of different concentrations of the anaesthetic magnesium chloride on juveniles and adults of the gastropod Pomacea diffusa from allopatric populations

In scientific investigations involving molluscs, various anaesthetics are used, with magnesium chloride proving itself to be effective. In this study, the effect of different concentrations of magnesium chloride solutions (4%, 7% and 10% w/v) was evaluated in juvenile and adult Pomacea diffusa, measuring relaxation, anaesthesia and recovery times and analysing the influence of the origin of the gastropods on these parameters. Specimens were collected from two different localities (Jauary and Centenário) in Itacoatiara, Amazonas, Brazil. Increasing magnesium chloride concentration reduced relaxation and anaesthesia times in juveniles and adults. Relaxation times (4%, 7%, 10%) were 16.91 ± 3.65, 14.48 ± 2.50, and 12.40 ± 2.73 min in juveniles, and 30.12 ± 5.39, 29.44 ± 7.70, and 20.90 ± 7.49 min in adults. Anaesthesia times were 22.21 ± 3.85, 18.06 ± 2.72, and 16.12 ± 2.58 min in juveniles, and 37.25 ± 5.12, 36.54 ± 7.59, and 25.80 ± 7.94 min in adults. Relaxation, anaesthesia, and recovery times differed significantly between juveniles and adults, although the different populations responded similarly. Thus, anaesthetic efficacy in P. diffusa was influenced by concentration and sexual maturity, with higher concentrations increasing efficacy and adults showing longer recovery times.