Toads of Rhinella (=Bufo) arenarum were subjected to a condition of forced submersion during a 40-minute period, to deepen the understanding of the mechanisms involved in the control of both submersion and emersion. Animals previously submitted to a first control measurement series, were then injected with atropine or propranolol, or were vagotomized. In animals either injected with atropine or vagotomized, a higher heart rate (HR) than in the control group was observed, before, during and after the forced submersion. These animals were able to decrease HR, although in a lesser extent than controls, suggesting that other mechanisms in addition to vagal activity are also producing and maintaining bradycardia during the submersion period. In those animals injected with propranolol (a β-adrenergic blocker), a HR lower than that of controls were observed only at the beginning of the submersion and during the emersion phase. The low HR caused by propranolol during emersion with buccal pumping shows the importance of the sympathetic system in increasing HR during emersion.

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 Q10value 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.

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.

La langosta de agua dulce Cherax quadricarinatus es una especie tropical de gran interés para la acuicultura. Se midió la concentración de vitelogenina (Vg) en hemolinfa, ovario y hepatopáncreas de hembras adultas de esta especie, por medio de ELISA. Las mediciones fueron hechas en los cuatro períodos del ciclo reproductivo: pre-reproductivo, reproductivo medio, reproductivo tardío y post-reproductivo. Se detectaron variaciones significativas en los niveles de Vg tanto en hemolinfa como en hepatopáncreas, se observó el mayor valor durante el período reproductivo medio. Además, tales variaciones se correlacionaron positivamente con el índice hepatosomático. Se observó además una correlación positiva de los niveles de Vg entre hepatopáncreas y ovario. Estos resultados apoyan evidencias previas sobre el papel central del hepatopáncreas como sitio de síntesis de Vg, en esta especie, y también enfatizan la importancia de la hemolinfa para el transporte de la Vg del hepatopáncreas al ovario. Para propósitos de acuicultura, la medición de Vg en hemolinfa podría ser utilizada como un método no lesivo, con el fin de constatar la actividad reproductiva de hembras de C. quadricarinatus.

The freshwater crayfish Cherax quadricarinatus is a tropical species of great interest for aquaculture. Vitellogenin (Vg), a lipoprotein precursor of the vitellum accumulated in spawned eggs, can be synthesized in the ovary and/or hepatopancreas of most crustaceans, being the hemolymph the way for transporting Vg throughout the reproductive cycle. Concentration of Vg in hemolymph, ovary and hepatopancreas of Cherax quadricarinatus adult females was measured by means of ELISA, specifically developed after purifying the native Vg. Measurements were made at four periods of the reproductive cycle: pre-reproductive, mid-reproductive, late reproductive and post-reproductive. Besides, both hepatosomatic (HSI) and gonadosomatic (GSI) indexes were determined in each period. Significant variations in Vg levels were detected in both hemolymph and hepatopancreas, being the highest values observed during the mid-reproductive period. Besides, such variations were positively correlated to the HSI. A positive correlation between Vg levels in hepatopancreas and ovary was also seen. These results support previous evidences about the central role of the hepatopancreas as a site of Vg synthesis in the studied species, together with the relevancy of hemolymph for transporting Vg from the hepatopancreas to the ovary. For aquaculture purposes, Vg monitoring in hemolymph could be used as a non-injurious method, to check the reproductive activity of C. quadricarinatus females.

Se utilizó al anomuro de agua dulce Aegla platensis como modelo para inducir el crecimiento ovárico mediante el agregado de diferentes neuroreguladores a una formulación de alimento pelleteado. Los compuestos agregados fueron el inhibidor dopaminergico spiperona ó el inhibidor encefalinérgico naloxone, ambos a una dosis de 10-8 moles/animal. Los animales fueron alimentados dos veces a la semana con pellets enriquecidos con alguno de los neuroreguladores. Luego de 7 semanas, se calculó el índice gonadomático (IG) como (peso gonadal fresco/ peso corporal fresco) x 100. El IG mostró un incremento significativamente sólo en aquellas hembras alimentadas con pellets enriquecidos con spiperona, en comparación con un grupo control que recibió pellets sin agregado alguno. Durante el período ensayado, la spiperona estaría revirtiendo el arresto ejercido por la dopamina sobre la estimulación neuroendocrina del crecimiento ovárico. Por otro lado, para ambos grupos experimentales (spiperona y naloxone), un mayor valor de IG estuvo correlacionado a un mayor incremento del contenido de lípidos tanto en gonadas como en hepatopáncreas, sugiriendo una demanda energética incrementada en relación con una activa inversión en reproducción

The freshwater crab Aegla platensis was used as a model to induce ovarian growth by adding different neuroregulators to a pellet food formulation. Added compounds were the dopaminergic inhibitor spiperone or the enkephalinergic inhibitor naloxone, both of them at a dose of 10-8 mol/animal. Animals were fed on the enriched pellets twice a week. After 7 wk, the gonadosomatic index (GI) was calculated as (gonad fresh weight / body fresh weight) x 100. GI significantly increased only for those females fed on spiperone pellets, compared to a control group receiving pellets with no compound added. During the assayed period, spiperone would be reverting the arrest exerted by dopamine on the neuroendocrine stimulation of ovarian growth. On the other hand, for both spiperone and naloxone a higher GI was correlated to a higher lipid content of both gonads and/or hepatopancreas, suggesting an increased energetic demand in accordance with an active investment in reproduction. Rev. Biol. Trop. 56 (3): 1201-1207. Epub 2008 September 30.

Male and female juvenile crabs of the species Chasmagnathus granulata were collected in Samborombón Bay (Argentina), on October 1994 and February 1995; these dates correspond to the beginning and end of the reproductive period of the species, respectively. No differences in the initial size (measured as carapace width, CW) existed between both clutches. Each clutch of juveniles was observed during a 1-year period, recording the percentage of molted crabs, intermolt period and percentual increment of size after each molting. At the end of the observation period, males and females from the October clutch reached the size of sexual maturity, while crabs of the remaining clutch did not. This difference was due to the higher increment in size of the October crabs at the third and fourth molts, compared to the February ones. Such difference seems to be related to an increase in reproductive effort during the breeding season, once the sexual maturity was attained

Se recolectaron en Bahía Samborombón (Argentina), ejemplares juveniles de ambos sexos de la especie Chasmagnathus granulata, durante octubre de 1994 y febrero de 1995 ; estos meses corresponden, respectivamente, al inicio y al final del período reproductivo de la especie. No se hallaron diferencias entre lotes para el ancho inicial de caparazón (CW). Cada lote de cangrejos juveniles fue observado durante un año en condiciones de laboratorio, registrándose el porcentaje de cangrejos mudados, período de intermuda e incremento porcentual de talla luego de cada muda. Al finalizar el período de observación, machos y hembras del lote de octubre alcanzaron la talla de madurez sexual mientras que los del lote de febrero no consiguieron alcanzar esa talla. Esta diferencia se debió al mayor incremento de talla de los cangrejos del lote de octubre en su tercera y cuarta muda, comparados con los cangrejo del otro lote. Tal diferencia parece estar relacionada con un incremento del esfuerzo reproductivo durante el período reproductivo, una vez alcanzada la madurez sexual