Oocyte adhesiveness and embryonic development ofAstyanax bimaculatus(Linnaeus, 1758) (Pisces: Characidae)

Abstract

This study shows for the first time the presence of a jelly coat on oocytes of neotropical Characiformes fish. This structure could be responsible for the adhesiveness of Astyanax bimaculatus oocytes, a species widely distributed in South America including in the São Francisco River basin in Brazil. Adult specimens of A. bimaculatus were submitted to artificial reproduction in order to analyse the egg morphology and embryonic development. The eggs were fertilised and kept in incubators with a water temperature of 24°C so that embryogenesis could be monitored. Ovulated and unfertilised oocytes were also collected and submitted to routine histological techniques. Astyanax bimaculatus oocytes were found to be spherical, yellowish, and covered by a thin jelly coat with a slightly adhesive surface. The mean oocyte diameter was 1.03 ± 0.03 mm, the perivitelline space was 0.21 ± 0.02 mm and the jelly coat's thickness was 0.04 ± 0.01 mm. Positive periodic acid-Schiff (PAS) stain and Alcian blue stain pH 2.5 indicated the presence of neutral glycoproteins, and carboxylated acid glycoconjugates on the jelly coat that formed mucosubstances that may be associated with egg adhesiveness. At a water temperature of 24°C, blastopore closure and hatching occurred at 5 h and 17 h after fertilisation, respectively. The results of this study provide essential information for phylogenetic studies and for a better understanding of the reproductive strategy of A. bimaculatus, currently included in the incertae sedis group of the Characidae family due to the lack of monophyly among the families of the group.

Environmental manipulation on Astyanax altiparanae out of season spawning

“…These subsamples were stored in Gilson solution (Simpson, 1951), and egg diameter (average length of longitudinal and latitudinal axis) of 50 eggs per female was analyzed afterward. The measurements were performed in a stereo- After a period of 120 degree-hours from fertilization (blastopore closure, Weber et al, 2012) 100 eggs of each female were separated to estimate the fertilization rates (RF = number of eggs × 100 / total number of eggs, Romagosa et al, 1990). The translucent eggs were considered fertilized, while the opaque eggs were the unfertilized eggs (Woynarovich & Horvath, 1989).…”

Gonadal development and reproductive period of the characin Astyanax aff. bimaculatus (Characiformes: Characidae) in a tropical reservoir in southeastern Brazil

“…This species seems to perform small movements for reproduction in both lentic and lotic environments (Godinho et al 2010, Weber et al 2012. Species of Astyanax are pelagic spawners normally reproducing in schools during upstream movements (Breder and Rosen 1966, Mazzoni and Iglesias-Rios 2004, Súarez et al 2017.…”

Spawning Behavior, Egg Development, Larvae and Juvenile Morphology of Hyphessobrycon eques (Pisces: Characidae) Characidae Fishes

“…There are several domestic studies regarding fine structures of embryos membranes of Hemigrammus ocellifer, Gymnocorymbus ternetzi, H. caudovittatus (Kim et al, 1996) and H. serpae (Kim et al, 2005a) whereas anti-oxidative capacity against ammonia stress (Pan et al, 2011), early development of the skull (Vandewalle et al, 2005), and embryonic development (Weber et al, 2012;Nakaghi et al, 2013) of Characidae were reported in international studies.…”