Abstract
The objective of this work was to study the morphologic development and the swimming and feeding behaviors of piracanjuba larvae, Brycon orbignyanus Valenciennes (1849) (Characiformes, Characidae, Bryconinae), during the period from zero to 172 hours after hatching (standard length = 3.62 - 11.94 mm). The morphological analyses were accomplished by using a trinocular stereo microscope, while the behavioral analyses were performed through periodic observations. In 28 hours after hatching, the larvae (standard length = 6.25 ± 0.13 mm) showed the following structural and behavioral characteristics that made them become active predators able to overcome a larval critical phase, the beginning of exogenous feeding: presence of pigmented eyes, terminal and wide mouth, developed oral dentition, developing digestive tube, yolk sac reduction, fins and swim bladder formation, horizontal swimming, cannibalism, and predation. Intense cannibalism among larvae was verified from 26 to 72 hours. At the end of the metamorphosis - 172 hours after hatching - the larvae measuring 11.94 + 0.80 mm in standard length presented a flexed notochord, caudal fin bifurcation, dorsal and anal fin formation, synchronized movements, and formation of shoals, characteristics that together allow enhanced perception and locomotio in exploration of the environment, determining the best moment for transfering to the fishponds. New studies can contribute to commercial fish farming by improving feeding management, performance, survival, and productivity of this species.
Highlights
Newly-hatched larvae of freshwater fish suffer significant changes in body shape, metabolism, swimming skills, and behavior during morphogenesis, which is a quick and complex process (Gisbert et al, 2002).The determination of the first exogenous feeding is a decisive factor in the commercial rearing of fish larvae, because if the food is provided prior to this moment, it will increase production costs related to waste; on the other hand, if delayed, the lack of food may compromise the growth and survival of the larvae (Maciel, 2006).The feeding behavior of larvae may be related to the perception and success of food consumption, to the distance covered to capture the food item, and their nutritional requirements
The piracanjuba larvae were fed with curimba (Prochilodus lineatus) larvae at 14 hours of age that were added to the incubators to minimize cannibalism
Eighteen hours after spawning, the piracanjuba larvae presented a standard length of 3.62 ± 0.17 mm and an elongated and transparent body (Figure 1A)
Summary
The determination of the first exogenous feeding is a decisive factor in the commercial rearing of fish larvae, because if the food is provided prior to this moment, it will increase production costs related to waste; on the other hand, if delayed, the lack of food may compromise the growth and survival of the larvae (Maciel, 2006). The feeding behavior of larvae may be related to the perception and success of food consumption, to the distance covered to capture the food item, and their nutritional requirements. These variables are associated with feeding models, species, size, and distribution of the available food (Maciel, 2006). In order to establish rearing methods aimed at the production of high quality fingerlings for stocking in artificial fishponds and natural courses of water, the study of the biology of the initial stages of fish is necessary, for native species, and this has been investigated in a few Brazilian institutions
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