Embryonic development in Zungaro jahu

Captive Breeding and Early Developmental Dynamics of Cirrhinus mrigala: Implications for Sustainable Seed Production

Cirrhinus mrigala is an important edible fish with a significant aquaculture contribution in Southeast Asian countries. The current study aims to enhance our understanding of the developmental biology of Cirrhinus mrigala, which is crucial for implementing sustainable fish farming practices. To induce spermiation and ovulation in Cirrhinus mrigala brooders, the synthetic hormone Ovaprim® (GnRH + dopamine inhibitor) was administrated as a single injection dose of 0.2 mL/kg to males and 0.4 mL/kg to females. After induction, the fish spawned, and the eggs produced were fertilized artificially and cell division commenced successfully. The characteristics of each larval developmental stage were closely observed and recorded using a time-lapse imaging technique. The fertilized eggs were spherical, demersal, and non-adhesive throughout their incubation period. The spawned eggs ranged in diameter from 2.1 mm to 2.13 mm and possessed circular yolk sacs. The gastrula stage initiated approximately 4 h after fertilization, with 25% of the yolk sphere covered by blastoderm, reaching 75% coverage at the end of the gastrula stage, approximately 6 h post fertilization. Organogenesis was marked by the formation of notochord and the visibility of rudimentary organs such as the heart, eyes, and gills, followed by tail movement, which was observed at the time of hatching. Compared to other cyprinid fishes, C. mrigala exhibited distinct features at certain stages of embryonic development. Blood circulation was observed to start at the onset of hatching. The lengths of the newly hatched larvae ranged from 2.9 to 3.2 mm, smaller than other reports on induced breeding in carps. The findings of the present study provide a detailed reference for the embryonic development of C. mrigala, which will assist its future research endeavors and large-scale seed production for sustainable aquaculture.

Larval development of Brycon amazonicus (Teleostei, Bryconidae) with a focus on locomotory, respiratory and feeding structures

In the present work we describe the larval development of Brycon amazonicus, with emphasis on structures linked to swimming, respiration and feeding. We monitored from larval hatching (13 h post-fertilization) to juvenile stage. Formation of the oral cavity and differentiation of gill arches began within 4 h post-hatching (hph) and within 11 hph the primordium of the pectoral fin appeared. At 25 hph, the head was in a rectilinear position with a terminal mouth, when the onset of tooth formation appeared. At 35 hph, gill arches were covered by the operculum and branchiostegal membrane and cusps of teeth pierced the epithelium of the premaxilla and anterior dentary region. Sharp teeth were observed in the maxilla at 171 hph and the pelvic fin primordium appeared at 243 hph, with taste buds on the tongue and the roof of the buccopharyngeal cavity. At 579 hph, all structures related to swimming and food capture were formed. Exogenous feeding of the larvae started at 29 hph, before the endogenous reserves were used up and the development of efficient swimming ability, reflecting the species' need to increasingly specialize on prey capture.

Embryonic development of teleost Brycon orbignyanus

Brycon orbignyanus is an important large teleost that is currently on the list of endangered species, therefore studies on its reproductive biology and embryology are fundamental to help species conservation and recovery. The objective of this research was to characterize the events that occur during extrusion, fertilization and embryonic development of the species. The samples were collected at predetermined times, fixed and processed for light microscopy and scanning electron microscopy. The greenish oocytes were spherical, had translucent chorion and a mean diameter of 1.3±0.11 mm. The eggs had well defined animal and vegetative poles approximately 18 min post-fertilization. Stages from 2 to 128 blastomeres occurred between 20 min and 3 h post-fertilization (hPF), when the morula was characterized. The blastula stage was observed between 2 and 3 hPF, and the gastrula between 3 and 7 hPF, when the embryonic shield emerged and the cellular migration with the consequent formation of epiblast and hypoblast. At 8 hPF, the formation of the neural tube, above the notochord and the encephalic region, was observed, delimiting the forebrain, mesencephalon and rhombencephalon regions. From 11 hPF onward, the optic vesicle was formed close to the forebrain and the embryo tail was well developed. The optic vesicle was observed from 12 hPF onward, and the tail showed an intense movement that culminated with the rupture of the chorion and consequent hatching of the larva at 13 hPF and 27°C.