Larval development of hoplias cf. Lacerdae (Pisces: Erythrinidae) and delayed initial feeding effects

Larval development of Hoplias cf. lacerdae was studied under laboratory conditions. After hatching, ontogenetic changes were recorded on food-deprived larvae in 12-hour intervals. Mouth opening occurred after 2.5 days and notochord terminated flexure in 6.5 days. Notochord length increased at a constant rate until complete yolk absorption (13,5 days). Larval dry weight and body height diminished gradually up to 21 days after hatching, when all starved larvae died. Every 12 hours after yolk absorption, groups of larvae (n=15), were separeted, and fed with Artemia nauplii for 10 days. The point-of-no-return (when 50% of larvae were unable to feed or to assimilate ingested food after delayed feeding), was not apparent in this species

Reproductive biology of Oligosarcus argenteus (Gunther, 1864) adult males and description of the gonadal maturation stages

Oligosarcus argenteus belongs to the Acestrorhynchinae subfamily, being restricted to South America, and found in several Brazilian hydrographic basins, in lotic and lentic environments, where they are able to reproduce. With the purpose of studying the reproductive biology of the males from this species, many morphological parameters were analyzed during a 24 month period, as well as characterizing the different testicular maturation stages. A maturity scale, with three stages (I - Initial Maturing, II - Intermediate Maturing, III - Final Maturing) was proposed for the adult males of Oligosarcus argenteus. The reproductive period was established by the bimonthly frequency of spermatogenesis and by the gonadal maturation stages.<br>Oligosarcus argenteus é uma espécie pertencente à subfamília Acestrorhynchinae, restrita à América do Sul, sendo comumente encontrada nas várias bacias hidrográficas brasileiras, em ambientes lóticos e lênticos, onde se reproduzem. Com o objetivo de estudar a biologia reprodutiva de machos desta espécie, vários parâmetros morfológicos foram analisados durante um período de 24 meses, assim como foram caracterizados os diferentes estádios de maturação testicular. Estes foram descritos, considerando-se exemplares adultos, em: Estádio I - Maturação Inicial, Estádio II - Maturação Intermediária e Estádio III - Maturação Final. Pela freqüência bimestral das células germinativas e dos estádios de maturação gonadal, a época de reprodução foi determinada