Ontogeny of digestive enzymes in larvae of the Clown Anemonefish, Amphiprion ocellaris (Perciformes: Pomacentridae)

Introduction: The Clown anemonefish (Amphiprion ocellaris) is the most popular fish species in the marine aquarium trade; however, there is a lack of information on their digestive physiology during larval ontogeny, valuable information needed for diet design and management protocols. Objective: To characterize the early digestive enzymes of A. ocellaris larvae. Methods: We used three pools (10 larvae each) and extracted 10 samples per tank, from just before hatching to the 38th day. We analyzed the specific activity of acid and alkaline proteases, trypsin, chymotrypsin, leucine aminopeptidase and lipase; and did acid and alkaline protease zymograms. Results: We detected all measured enzymes at hatching. Acid proteases increased in activity until the 38th day. Alkaline proteases, trypsin, chymotrypsin, and leucine aminopeptidase had the same pattern, and maximum activity on the 8th day, decreasing at the 38th day. Lipase activity peaked on the 8th and 30th day. The acid zymogram had a single band, appearing on the 8th day. A total of eight alkaline proteases were revealed (154.2, 128.1, 104.0, 59.8, 53.5, 41.9, 36.5 and 25.1 KDa), with seven bands on the 1st day and all bands from the 3rd to 8th day, decreasing at two bands (41.9 and 25.1 KDa) in the 38th day. Conclusion: A. ocellaris has a functional stomach on the 8th day, and, on the 38th day, a digestive omnivore pattern with a tendency to carnivory.

Introducción: El pez payaso (Amphiprion ocellaris) es la especie de pez más popular en el comercio de acuarios marinos; sin embargo, falta información sobre su fisiología digestiva durante la ontogenia larval, información valiosa necesaria para protocolos de diseño y manejo dietético. Objetivo: Caracterizar las enzimas digestivas tempranas de larvas de A. ocellaris. Métodos: Usamos tres homogenados (con 10 larvas cada uno) y extrajimos 10 muestras por tanque, justo antes de la eclosión hasta el día 38. Analizamos la actividad específica de proteasas ácidas y alcalinas, tripsina, quimotripsina, leucina aminopeptidasa y lipasa; e hicimos zimogramas de proteasas ácidas y alcalinas. Resultados: Detectamos todas las enzimas medidas en la eclosión. La actividad de proteasas ácidas incrementó hasta el día 38. Proteasas alcalinas, tripsina, quimotripsina, y leucina aminopeptidasa tuvieron el mismo patrón, con actividad máxima en el octavo día, decreciendo en el día 38. Hubo picos en la actividad lipasa a los ocho y 30 días. El zimograma ácido tuvo una banda única, apareciendo al octavo día. Se hallaron ocho proteasas alcalinas (154.2, 128.1, 104.0, 59.8, 53.5, 41.9, 36.5 y 25.1 KDa), con siete bandas al primer día, y todas las bandas entre el tercer y octavo día, bajando a dos bandas (41.9 y 25.1 KDa) al día 38. Conclusión: A. ocellaris tiene un estómago funcional al octavo día, y, al día 38, un patrón digestivo omnívoro con tendencias carnívoras.

Metabolic responses of adult lion's paw scallops Nodipecten subnodosus exposed to acute hyperthermia in relation to seasonal reproductive effort.

In marine ectotherms, reproduction is an energetically expensive process that affects their thermal window tolerance. For most species, the impacts of hyperthermia during gametogenesis have still not been addressed. Our aim was to assess the metabolic response of adult Nodipecten subnodosus scallops to thermal challenges at early development (spring) and advanced gonad maturation (summer). Scallops collected in both seasons were exposed to acute hyperthermia (26 and 30 °C, 24 h), maintaining a group of scallops at acclimation temperature (22 °C) as a control condition. During the summer, relatively low activity of hexokinase (HK), as well as low levels of ATP and GTP were found in the adductor muscle, suggesting a shift in energy investment for reproduction, although arginine phosphate (ArgP) levels were higher in summer scallops. Hyperthermia (30 °C) induced an increased energy expenditure reflected by a transitory enhanced oxygen consumption (VO2) and relatively high activities of HK and arginine kinase (AK). Moreover, a slight decrease in adenylic energy charge (AEC) was partially compensated by a decrease in ArgP. An increase in nucleotide by-products inosine monophosphate (IMP) and hypoxanthine (HX) indicated a thermal stress at 30 °C. Some of the responses to acute hyperthermia were more pronounced at advanced maturation stages (summer scallops), indicating a possible lack of energy balance, with possible implications in animals challenged to global warming scenario.