RESUMO

Se evaluaron las reservas energéticas, el crecimiento y la tasa metabólica de langostas juveniles de agua dulce Cherax quadricarinatus (von Martens, 1868), aclimatadas durante 16 semanas tanto a 25ºC (temperatura cercana al óptimo) como a 20ºC (temperatura marginal para la especie). Adicionalmente, se evaluó el efecto modulador de la ecdisona sobre la aclimatación. Luego de 12 semanas de exposición, la ganancia en peso de ambos grupos experimentales aclimatados a 25ºC (control: C25, y tratados con ecdisona: E25) fue significativamente mayor que la de los grupos aclimatados a 20ºC (C20 and E20). Se verificó una compensación total en la tasa metabólica, luego de la aclimatación desde 25 a 20ºC, tanto para el grupo control como para el tratado con ecdisona. Solamente se observó un valor de Q10 significativamente mayor en el grupo aclimatado a 20ºC y tratado con ecdisona. En ambos grupos aclimatados a 20ºC, se determinó un reducción en la reservas de glucógeno, tanto en hepatopancreas como en músculo, así como un menor contenido de proteína en músculo. Correspondiente, la glucemia resultó siempre más elevada en esos grupos, que también mostraron un mayor nivel de lípidos en el hepatopancreas, siendo mayor el nivel de lípidos en músculo sólo para los juveniles aclimatados a 20ºC y tratados con ecdisona.(AU)

Growth, metabolic rate, and energy reserves of Cherax quadricarinatus (von Martens, 1868) juveniles were evaluated in crayfish acclimated for 16 weeks to either 25ºC (temperature near optimum) or 20ºC (marginal for the species). Additionally, the modulating effect of ecdsyone on acclimation was studied. After 12 weeks of exposure, weight gain of both experimental groups acclimated to 25ºC (control: C25, and ecdysone treated: E25) was significantly higher than that of those groups acclimated to 20ºC (C20 and E20). A total compensation in metabolic rate was seen after acclimation from 25ºC to 20ºC; for both the control group and the group treated with ecdysone. A Q10 value significantly higher was only observed in the group acclimated to 20ºC and treated with ecdysone. A reduction of glycogen reserves in both hepatopancreas and muscle, as well as a lower protein content in muscle, was seen in both groups acclimated to 20ºC. Correspondingly, glycemia was always higher in these groups. Increased lipid levels were seen in the hepatopancreas of animals acclimated to 20ºC, while a higher lipid level was also observed in muscle at 20ºC, but only in ecdysone-treated crayfish.(AU)

Assuntos

RESUMO

Se evaluaron las reservas energéticas, el crecimiento y la tasa metabólica de langostas juveniles de agua dulce Cherax quadricarinatus (von Martens, 1868), aclimatadas durante 16 semanas tanto a 25ºC (temperatura cercana al óptimo) como a 20ºC (temperatura marginal para la especie). Adicionalmente, se evaluó el efecto modulador de la ecdisona sobre la aclimatación. Luego de 12 semanas de exposición, la ganancia en peso de ambos grupos experimentales aclimatados a 25ºC (control: C25, y tratados con ecdisona: E25) fue significativamente mayor que la de los grupos aclimatados a 20ºC (C20 and E20). Se verificó una compensación total en la tasa metabólica, luego de la aclimatación desde 25 a 20ºC, tanto para el grupo control como para el tratado con ecdisona. Solamente se observó un valor de Q10 significativamente mayor en el grupo aclimatado a 20ºC y tratado con ecdisona. En ambos grupos aclimatados a 20ºC, se determinó un reducción en la reservas de glucógeno, tanto en hepatopancreas como en músculo, así como un menor contenido de proteína en músculo. Correspondiente, la glucemia resultó siempre más elevada en esos grupos, que también mostraron un mayor nivel de lípidos en el hepatopancreas, siendo mayor el nivel de lípidos en músculo sólo para los juveniles aclimatados a 20ºC y tratados con ecdisona.

Growth, metabolic rate, and energy reserves of Cherax quadricarinatus (von Martens, 1868) juveniles were evaluated in crayfish acclimated for 16 weeks to either 25ºC (temperature near optimum) or 20ºC (marginal for the species). Additionally, the modulating effect of ecdsyone on acclimation was studied. After 12 weeks of exposure, weight gain of both experimental groups acclimated to 25ºC (control: C25, and ecdysone treated: E25) was significantly higher than that of those groups acclimated to 20ºC (C20 and E20). A total compensation in metabolic rate was seen after acclimation from 25ºC to 20ºC; for both the control group and the group treated with ecdysone. A Q10 value significantly higher was only observed in the group acclimated to 20ºC and treated with ecdysone. A reduction of glycogen reserves in both hepatopancreas and muscle, as well as a lower protein content in muscle, was seen in both groups acclimated to 20ºC. Correspondingly, glycemia was always higher in these groups. Increased lipid levels were seen in the hepatopancreas of animals acclimated to 20ºC, while a higher lipid level was also observed in muscle at 20ºC, but only in ecdysone-treated crayfish.

Assuntos

RESUMO

Freshwater crayfish Cherax quadricarinatus have a high commercial value and are cultured in farms where they are potentially exposed to pesticides. Therefore, we examined the sublethal effects of a 50-day exposure to glyphosate acid and polyoxyethylenamine (POEA), both alone and in a 3:1 mixture, on the growth and energetic reserves in muscle, hepatopancreas and hemolymph of growing juvenile crayfish. Exposure to two different glyphosate and POEA mixtures caused lower somatic growth and decreased muscle protein levels. These effects, caused by both compounds interacting in the mixture, could also be synergistic because they were expressed even at the lowest concentration. The decrease in protein levels could be related to the greater use of other energy reserves. This hypothesis is supported by the decrease in muscle glycogen stores due to glyphosate exposure and the decrease in lipid reserves associated with exposure to POEA.

Assuntos

RESUMO

The in vitro effect of both spiperone (dopaminergic antagonist) and naloxone (enkephalinergic antagonist), was assayed on small pieces of ovary dissected from C. quadricarinatus females, with the eventual addition of some neuroendocrine organs, such as thoracic ganglion or eyestalk tissue. The incorporation of tritiated leucine by the ovary was measured in order to estimate the ovarian growth. During the post-reproductive period, both mentioned antagonists were able to significantly stimulate the ovary in the presence of thoracic ganglion, but did not produce any significant effect in the preparation containing ovary and eyestalk tissue, or only ovary. No significant effects of the assayed antagonists were noted during the pre-reproductive period. These results were in accordance with previous models describing the neuroendocrine control of crustacean reproduction, and represent new findings about the hormonal context in different periods of the reproductive cycle of crayfish. Besides, by means of the experimental combination of the tested antagonists with dopamine or met-enkephalin, a new model dealing with the interaction of these two neurotransmitters on the hormonal secretion of thoracic ganglion has been proposed.

Assuntos