Ontogenesis and embryogenesis of Megaleporinus elongatus larvae (Characiformes: Anostomidae) from the Jequitinhonha River Basin

Abstract

Summary Five females and five males of Megaleporinus elongatus captured in the Jequitinhonha River were transferred to hypophysation tanks with a constant water flow at 26°C at the Machado Mineiro Fish Farm. They were submitted to induced reproduction by the hypophysation method. Crude carp pituitary extract (Cyprinus carpio) was injected into the coelomic cavity in two doses (2.5 and 5.0 mg/kg) for males and 3 doses (2.5, 5.0, and 2.5 mg/kg) for females. The doses were applied with a 24‐hr interval between the 1st and 2nd doses and a 12‐hr interval between the 2nd and 3rd ones. Oocytes and semen were obtained by manual extrusion, and the dry method was used for fertilisation. The eggs were kept in funnel type 20‐litre incubators with constant water flow at 23°C. Egg samples were collected every 10 min and photographed under a stereomicroscope for analysis of embryonic development until hatching. The main events of embryogenesis and their respective duration times were: cleavage (45 min), blastula (3 hr 14 min), gastrula (5 hr 25 min), closure of blastopore (6 hr 34 min), differentiation of somites (13 hr 20 min), tail release (17 hr 50 min), and hatching (24 hr 50 min). During the larval ontogenesis, the yolk sac gradually decreased until its complete reabsorption on the 7th day after hatching. The opening of the mouth and digestive tract occurred from the 5th to the 7th day, indicating that larvae could feed exogenously. These results provide information to improve the techniques of induced spawning and cultivation of M. elongatus.

Early development ofProchilodus nigricansSpix & Agassiz 1829 (Characiformes: Prochilodontidae) in captivity

“…This information is relevant for the correct identification of the species in natural environments, and thus, it contributes to the understanding of spawning areas and periods. Moreover, larval descriptions organize morphological and biometric parameters that are necessary for the fish farming environment for the development of reproduction and larviculture protocols (Lima et al, 2021; Perrotti et al, 2019; Portella et al, 2014). Thus, significantly contributing to the development of technological packages aimed at maximizing the production cycle of native species in confined environments.…”

“…of the species in natural environments, and thus, it contributes to the understanding of spawning areas and periods. Moreover, larval descriptions organize morphological and biometric parameters that are necessary for the fish farming environment for the development of reproduction and larviculture protocols (Lima et al, 2021;Perrotti et al, 2019;Portella et al, 2014). Thus…”