Reproductive biology ofAstyanax fasciatus(Pisces: Characiformes) in a reservoir in southeastern Brazil

Abstract

To study the reproductive biology of Astyanax fasciatus (Cuvier, 1819) in Furnas Reservoir, Minas Gerais, Brazil, a total of 1307 specimens were captured in bimonthly sampling from August 1993 to July 1994. The sex ratio showed a predominance of females, representing 65.2% of the total sample. The stages of gonadal maturation and spawning type were determined through macro-and microscopic analysis of the gonads as well as by variation in the gonadosomatic indices. A. fasciatus showed fractionated spawning and reproduction throughout the year, with spawning peaks influenced by water temperature and rainfall. Males and females initiated gonadal maturation at a mean standard length of 6.4 and 6.5 cm, respectively. During gonadal maturation, females showed a reduction in hepatosomatic index (from 1.06 to 0.83), suggesting that hepatic substances are transferred from the liver to the ovaries. In the reproductive period, A. fasciatus had lower stomach repletion and coelomic fat indices, indicating that this species ate less and consumed more fat reserves when reproduction had the maximum GSI (11.3 for females and 2.7 for males). Weight of the ovaries had a positive influence on the condition factor (K1), as the lowest K2 value (weight without gonads) were obtained during maturation, confirming the influence of the ovaries upon the physiological condition of the females. In weight-length relationship, parameter b was 3.02 for females and 2.23 for males, and the correlation coefficient (r 2 ) was 0.84 and 0.66, respectively.

Biologia reprodutiva de Astyanax henseli (Teleostei, Characidae) do curso superior do Rio dos Sinos, RS, Brasil

“…2009) e A. fasciatus (Cuvier, 1819) (CARVALHO et al, 2009), enquanto outros encontraram desova total para as espécies A. schubarti (NOMURA, 1975), A. fasciatus (NOMURA, 1975;GURGEL, 2004) e A. bimaculatus (NOMURA, 1975;SANTOS et al, 1996). Além dessa variação no tipo de desova entre espécies de Astyanax, GARUTTI (1989), estudando populações de A. bimaculatus da bacia do rio Paraná, sugeriu que a espécie exibe desova parcelada e período reprodutivo prolongado em hábitats como riachos e cabeceiras de rios e desova total e período reprodutivo curto em rios com maior volume de água, onde os indivíduos estariam menos expostos a mudanças abruptas.…”

Reproduction of Pimelodus maculatus(Siluriformes: Pimelodidae) in three section of Grande River basin, downstream Porto Colombia dam, south-eastern Brazil

“…Gonad fragments were fixed in Bouin's fluid for 8 to 12 hours, kept in alcohol 70% and were submitted to the routine histological techniques: paraffin embedding, 3-5 µm thick microtomy sections, and haematoxylin and eosin stain (HE). The gonadal maturation stages were established based on the oocyte distribution, spermatogenic lineage cells, and variations of the GSI (Santos et al, 2004;Carvalho et al, 2009;Arantes et al, 2010). The diameter of the vitellogenic follicles (follicular cells, zona pellucida and oocyte) was determined from histological slides of the mature ovaries using a micrometric ocular attached to a light microscope.…”

Seasonal changes in the gonadossomatic index, allometric condition factor and sex ratio of an auchenipterid catfish from eastern Amazonia

“…The breeding season was identified by using two different approaches: (1) the seasonal variation concerning relative frequencies of ovarian and testis classified according to the maturation stage; and (2) through the analysis of the seasonal variation in the gonadosomatic index (GSI) (Vazzoler, 1996;Becker et al, 2008;Carvalho et al, 2009;Santos et al, 2010).…”