Occurrence and significance of ovarian and follicular regression in cachara Pseudoplatystoma fasciatum (Linnaeus, 1766): a histology approach

The processes of ovarian regression and follicular atresia which reproduction was not induced by hormone in confined cachara, Pseudoplatystoma fasciatum, were investigated. The macro and microscopic characteristics (oocytes diameter and histology) of the ovaries were described every 20 days, in four stages: initial regression (Rg I = first 20 days), intermediate regression (Rg II = from 21st to 40th day), final regression (Rg III = from 41st to 80th day) and the recovering stage, called resting II (R II = from 81st to 150th day). The experiment was conducted from late January (summer - longer days) to May (autumn - shorter days). In the beginning, A0 samples showed oocyte diameters ranging from 437.5 to 1,187.5mm, suggesting that oocytes were in perinucleolar, at final maturation and atretic phases. After 150 days, the diameters reached the lowest values and a ruptured zona radiata, as well as the nearly complete reabsorption of the yolk could be visualized. At the same time, a sharp decrease in the mean values of the gonadosomatic index (GSI), water temperature, photophase and rainfall was observed. The gradual involution of this long process was dynamic and complex, affecting the spawning success (fertilization, eclosion and larvae survival rates) and, consequently, the whole productive system.

Estudaram-se os processos de regressão ovariana e atresia folicular em cachara, Pseudoplatystoma fasciatum, mantida em cativeiro, na reprodução não induzida por hormônios. As características macro e microscópicas (diâmetro dos ovócitos e histologia) dos ovários foram descritas a cada 20 dias, em quatro estádios: na regressão inicial (Rg I - os primeiros 20 dias), na regressão intermediária (Rg II - do 21° ao 40° dia), na regressão final (Rg III - do 41° ao 80° dia) e na fase de recuperação ou de repouso II (R II - do 81° ao 150° dia). O experimento foi realizado do final de janeiro (verão-dias longos) a maio (outono-dias curtos). No início do experimento, as amostras apresentaram ovócitos com diâmetros que variaram de 437,5 a 1.187,5mm, sugerindo encontrarem-se nas fases perinucleolar, de maturação final e atrésicos. Aos 150 dias, os diâmetros atingiram os menores valores e pôde-se visualizar a zona radiata rompida e o vitelo reabsorvido. Concomitantemente, houve diminuição abrupta dos valores médios do índice gonadossomático, da temperatura da água, das horas de luz e de chuva. A involução gradual do longo processo foi dinâmica e complexa, afetando o êxito da desova (taxas de fertilização, de eclosão e de sobrevivência de larvas) e, conseqüentemente, o sistema produtivo.

Plasma testosterone and 11-ketotestosterone levels of male pacu Piaractus mesopotamicus (Cypriniformes, Characidae)

The levels of testosterone (T) and 11-ketotestosterone (11-KT) of the South American pacu Piaractus mesopotamicus were determined by radioimmunoassay during two stages of the reproductive cycle, i.e., resting and maturation, and the gonadosomatic index (GSI) was calculated. The highest levels of T and 11-KT were reached during the maturation stage (T= 2400 + 56 pg/ml; 11-KT= 2300 + 60 pg/ml) and lower levels were maintained during the resting period. The rise in androgen levels occurred with the appearance of spermatozoa in the maturation stage, when GSI was highest.

Morphological and cytochemical characterization of cell types of the adenohypophysis of Manjuba, Anchoviella lepidentostole (Fowler, 1911) (Osteichthyes, Engraulidae)

A hipófise de Anchoviella lepidentostole apresenta-se dividida em neuro-hipófise e adeno-hipófise, sendo que a caracterizaçäo morfológica e citoquímica dos tipos celulares desta regiäo foi a proposta deste trabalho. A adeno-hipófise divide-se em pars intermedia (PI) e pars distalis (PD), sendo que esta última se divide em pars distalis rostralis (PDR) e pars distalis proximalis (PDP). As células da PDR organizam-se em folículos. No epitélio folicular foram caracterizados quatro tipos celulares: I-PDR (basófilo), II-PDR (positivo à hematoxilina-chumbo/HPb+), III-PDR (PAS+, AB pH2,5+ e AF+), e IV-PDR (acidófilas). A PDP possui dois tipos celulares: I-PDP (PAS+, AB pH2,5+ e AF+) e II-PDP (acidófilas). Na PI também foram caracterizados dois tipos celulares: I-PI (HPb+) e II-PI (cromófobo aos métodos empregados)

Plasma steroid and corticosteroid levels in female pacu Piaractus mesopotamicus, Teleostei-Characidae

We report the plasma levels of estradiol-l7Beta (E2), testosterone (T), 17(alpha-2Obeta-dihydroxy-4-pregnen-3-one (l7-2OP), and cortisol (F) in female pacu during the reproductive cycle (N = 44) and in females induced to ovulate with an analogue of luteinizing hormone releasing hormone (LHRHa; 10 mug/kg) (N = 24). The plasma hormone levels were determined by validated radioimmunoassays. Females sampled during the reproductive cycle were grouped into 4 gonadal stages: resting, early maturation, advanced maturation and regression. The calculated gonadosomatic index varied from 0.5 ñ 0.1 per cent in resting stage to 8.1 ñ 0.6 per cent in advanced maturation stage. The E2 and T values were highest during the early maturation stage (E2 = 2172 ñ 7.1 pg/ml; T = 412 ñ 58 pg/ml) and the F values were highest during the advanced maturation stage (l32 ñ 5 ng/ml). Females induced to ovulate by LHRHa injection were sampled at 0, 6, and 12 h after injection of LHRHa. Two additional groups were sampled at ovulation and 24 h after ovulation. The E2 values were highest at 6 h (2917 + 65 pg/ml). The T and F values were highest at ovulation (T = 3498 + 77 pg/ml; F = 387 ñ 16 ng/ml) and 17-20P was detected only at vulation (2163 ñ 80 pg/ml).