Changes in digestive enzymes activities during the initial ontogeny of wolf cichlid, Parachromis dovii (Perciformes: Cichlidae)

Wolf cichlid, Parachromis dovii, is a species with a high potential for aquaculture in Central America; however, the knowledge of the digestive physiology in larvae period is limited. For these reason, this study evaluated the changes on digestive enzymes (alkaline and acid proteases, trypsin, chymotrypsin, aminopeptidase, carboxypeptidase, lipases, amylases, and phosphatases) during early ontogeny by biochemical analysis. All digestive enzymes were detected at first feeding (6 days after hatching, DAH, 9.49 mm, 168 degree-days DD). Afterwards all enzymes reached two main peaks in activity at 14 or 22 DAH (15.10 mm, 364 DD and 20.83 mm, 550 DD, respectively). Later, there was a gradual decrease in activity for trypsin and acid and alkaline phosphatases until reach the lowest values at 41 DAH. In the case of acid proteases, chymotrypsin, aminopeptidase, carboxypeptidase, lipase and amylase, all activities reached their maximum values at the end of the larval period, except for alkaline proteases, which showed the maximum value at 14 DAH (15.10 mm, 364 DD). Parachromis dovii larvae have an early capability to hydrolyze exogenous food, agreeing with other carnivorous neotropical cichlid species, for this reason we proposed that the weaning process could begin at 14 DAH.(AU)

El guapote lagunero (Parachromis dovii) es una especie con un alto potencial para la acuicultura en la región de América Central; sin embargo, existe un conocimiento limitado sobre la capacidad digestiva en el periodo larval. Por este motivo, este estudio evaluó los cambios de las enzimas digestivas (proteasas alcalinas y ácidas, tripsina, quimotripsina, aminopeptidasa, carboxipeptidasa, lipasas, amilasas y fosfatasas) durante la ontogenia temprana mediante análisis bioquímico. Todas las enzimas digestivas analizadas se detectaron en la primera alimentación (6 días después de la eclosión, DAH, 9.49 mm, 168 día-grados DD). Después, todas las enzimas alcanzaron dos picos máximos a los 14 o 22 DAH (15.10 mm, 364 DD and 20.83 mm, 550 DD, respectivamente). Después las actividades tripsina, fosfatasas ácidas y alcalina disminuyeron a sus valores más bajos a los 41 DAH. En el caso de las proteasas ácidas y alcalinas, quimotripsina, aminopeptidasa, carboxipeptidasa, lipasa y amilasa, los niveles de actividad aumentaron y alcanzaron su máximo valor al final del período larvario, excepto las proteasas alcalinas, que mostraron su máximo valor a los 14 DAH (15.10 mm, 364 DD). Las larvas de P. dovii tienen una capacidad temprana para hidrolizar alimentos exógenos, lo que concuerda con otras especies de cíclidos neotropicales carnívoros, por lo que proponemos que el proceso de destete inicie a los 14 DAH.(AU)

In vitro digestibility and proteases inhibitory effect of several feedstuffs for Parachromis dovii juveniles and P. dovii hybrid larvae.

Parachromis dovii, a native cichlid from Costa Rica, is highly appreciated for its size and flesh quality. Further, P. dovii easily accept inert feed from the beginning of exogenous feeding; however, its growth is low compared to live food. For this reason, evaluation of several feedstuffs using two in vitro techniques was done. The quantification of the in vitro inhibitory effect of seven plant ingredients on the alkaline protease activity was done using enzymatic extracts from larvae samples of 6, 15, 22 and 30 days after hatching (DAH). The in vitro alkaline digestibility assays were run for six protein sources (from animal and plant origin) using the enzymatic extract from larvae 30 DAH. Independent of fish age, all plant feedstuffs reduced alkaline digestive proteases activity; however, the wheat flour (14.1 % at 6 DAH, 33.4 % at 15 DAH) and broken rice meal (51.6 % at 22 DAH) showed the lowest inhibition percentage of alkaline digestive activity, whereas the highest inhibition percentage was found with soybean and palm kernel meals (92.5 % at 30 DAH and 87.4 %, respectively) (P < 0.05). The alkaline proteases inhibition percentage of feedstuffs varied during larvae ontogeny. From six protein dietary sources tested, tankage and fish meal presented the highest in vitro digestibility values, 113.9 and 74.9 %, respectively. Contrary, the lowest digestibility was found for blood and soybean meals (38.07 and 19.82 %, respectively).

The proteolytic digestive activity and growth during ontogeny of Parachromis dovii larvae (Pisces: Cichlidae) using two feeding protocols.

The proteolytic digestive activity and growth of Parachromis dovii larvae during the ontogeny were evaluated in a recirculation system using two feeding strategies during a 28-day period. Larvae were reared using two feeding protocols (three replicates each): (A) Artemia nauplii (at satiation), fed from exogenous feeding [8 days after hatching (DAH)] until 15 DAH followed by nauplii substitution by formulated feed (20% day(-1)) until 20 DAH and then formulated feed until 28 DAH; (B) formulated feed (100 % BW daily) from exogenous feeding until 28 DAH. Levels of acid (pepsin type) and alkaline digestive proteases as well as growth and survival of larvae were measured along the feeding period. Survival was high and similar between treatments: 98.9 ± 0.0 for Artemia, 97.3 ± 0.0% for formulated feed. The specific growth rate for length and weight was higher in larvae fed with Artemia nauplii than in larvae reared with formulated feed: 3.4 ± 0.1 versus 1.8 ± 0.1% day(-1) for body length (P = 0.009) and 12.2 ± 0.1 versus 6.5 ± 0.3% day(-1) for body weight (P = 0.002). The acid and alkaline proteolytic activity was detected, in both treatments, from the beginning of the experiment, at 8 DAH. The total enzymatic activity (U larva(-1)) for acid and alkaline proteases was higher in larvae reared with Artemia after 12 DAH, whereas the specific enzymatic activity was similar for both enzyme types in the two treatments. The results suggest that P. dovii larvae were capable to digest formulated diets from the beginning of exogenous feeding and that they could be reared with formulated feeds. However, the formulated feed used should be nutritionally improved because of the poor growth obtained in this research.