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.

Moderate ethanol exposure during early ontogeny of the rat alters respiratory plasticity, ultrasonic distress vocalizations, increases brain catalase activity, and acetaldehyde-mediated ethanol intake.

Early ontogeny of the rat (late gestation and postnatal first week) is a sensitive period to ethanol's positive reinforcing effects and its detrimental effects on respiratory plasticity. Recent studies show that acetaldehyde, the first ethanol metabolite, plays a key role in the modulation of ethanol motivational effects. Ethanol brain metabolization into acetaldehyde via the catalase system appears critical in modulating ethanol positive reinforcing consequences. Catalase system activity peak levels occur early in the ontogeny. Yet, the role of ethanol-derived acetaldehyde during the late gestational period on respiration response, ultrasonic vocalizations (USVs), and ethanol intake during the first week of the rat remains poorly explored. In the present study, pregnant rats were given a subcutaneous injection of an acetaldehyde-sequestering agent (D-penicillamine, 50 mg/kg) or saline (0.9% NaCl), 30 min prior to an intragastric administration of ethanol (2.0 g/kg) or water (vehicle) on gestational days 17-20. Respiration rates (breaths/min) and apneic episodes in a whole-body plethysmograph were registered on postnatal days (PDs) 2 and 4, while simultaneously pups received milk or ethanol infusions for 40-min in an artificial lactation test. Each intake test was followed by a 5-min long USVs emission record. On PD 8, immediately after pups completed a 15-min ethanol intake test, brain samples were collected and kept frozen for catalase activity determination. Results indicated that a moderate experience with ethanol during the late gestational period disrupted breathing plasticity, increased ethanol intake, as well brain catalase activity. Animals postnatally exposed to ethanol increased their ethanol intake and exerted differential affective reactions on USVs and apneic episodes depending on whether the experience with ethanol occur prenatal or postnatally. Under the present experimental conditions, we failed to observe, a clear role of acetaldehyde mediating ethanol's effects on respiratory plasticity or affective states, nevertheless gestational acetaldehyde was of crucial importance in determining subsequent ethanol intake affinity. As a whole, results emphasize the importance of considering the participation of acetaldehyde in fetal programming processes derived from a brief moderate ethanol experience early in development, which in turn, argues against "safe or harmless" ethanol levels of exposure.

Characterization and expression of the gene glucose transporter 2 (GLUT2) in embryonic, larval and adult Bay snook Petenia splendida (Cichliformes: Cichlidae)

Bay snook (Petenia splendida) is a carnivorous cichlid species with excellent economic value in Southeast Mexico. Although this species presents an excellent potential for commercial aquaculture, the information about its nutritional, physiological, and reproductive metabolic pathways is meager. The current study focuses on the expression of glucose transporter 2 (glut2) in embryos and larvae at 5, 10, 15-, 20-, 25-, and 30-days post-hatch (dph) and in the liver, intestine, kidney, muscle, heart, testicle, gill, stomach, pancreas, and brain of adult fish. The partial sequence of glut2 was obtained, and specific qPCR primers were designed. In embryos, the expression was lower compared to larvae at 5, 15, and 20 dph. The highest expression in larvae occurred at 20 dph and the lowest at 25 and 30 dph. Maximum expression levels in adults occurred in the liver and intestine. Our results show that glut2 is expressed differentially across tissues of adult bay snook, and it fluctuates during larval development.(AU)

La mojarra tenguayaca (Petenia splendida) es una especie de cíclido carnívoro con excelente valor comercial en el sureste de México. A pesar de su potencial para la acuicultura, existe muy poca información sobre sus rutas metabólicas relacionadas con su nutrición, fisiología y reproducción. El presente estudio se enfoca en la expresión del transportador de glucosa (glut2) en embriones y larvas de 5, 10, 15, 20, 25 y 30 días post eclosión (dph) y en el hígado, intestino, riñón, músculo, corazón, testículo, branquias, estómago, páncreas y cerebro en peces adultos. Se diseñaron cebadores de qPCR específicos para glut2. La expresión en los embriones fue menor que en larvas a los 5, 15 y 20 dph. La expresión máxima en larvas se observó a los 20 dph y la mínima a los 25 y 30 dph. La expresión más alta en los adultos ocurrió en el hígado y el intestino. Nuestros resultados muestran que el gen glut2 se expresa de manera diferencial en los tejidos de adultos de la mojarra tenguayaca y su expresión fluctúa durante el desarrollo larvario.(AU)

Early ontogeny of Pimelodus blochii Valenciennes, 1840 (Siluriformes: Pimelodidae): Neotropical catfish.

Larval ontogeny of the long-whiskered catfish Pimelodus blochii Valenciennes, 1840 is described, providing useful characters for identification and determining the growth pattern throughout its development. Eighty-nine larvae classified in three stages (preflexion, flexion and postflexion) and 30 juveniles were analyzed, totaling 119 individuals. The specimens were collected monthly from January 2013 to May 2019 in the lower Amazon river. A suite of morphological, morphometric, and meristic data was used to describe the stages of development. Three analytical regression models were used: simple linear, quadratic and piecewise regressions. The larvae are characterized by small to moderate eyes, subinferior mouth, and long barbels (maxillary larger than the mental barbels), triangular-shaped adipose fin, and the final part of the intestine reaching half the body. Pigmentation consists of dendritic chromatophores distributed irregularly in the body, ventral region and head, intensifying in the flanks and dorsal region throughout development. The total number of myomeres has a mode of 42 muscle bundles, ranging from 40 to 42 (15 to 16 pre-and 25 to 26 post-anal) and the number of fin segments corresponded to: pectoral = I + 9, pelvic = 6, dorsal = I + 6 and anal = 11-12. All body variables showed discontinuous isometric growth, indicating a deceleration in the structural modeling of the body, between the flexion/post-flexion stages and acceleration in post-flexion/early juvenile period. Precisely when the formation of the fin rays, muscles and organs of the digestive system and ossification are observed, suggesting low morphological variation during ontogenetic development. Pimelodus blochii differs from other congeneric species in the lower Amazon river by meristic characters, which helps to correctly identify individuals in early stages of development.