Embryonic and larval development of Jundiá (Rhamdia quelen, Quoy & Gaimard, 1824, Pisces, Teleostei), a South American Catfish

The jundiá (Rhamdia quelen, Quoy & Gaimard) is an endemic South American fish species. Because this species supports cold winters and grows faster during warm months, it has begun to be viewed as an ideal species for fish production in southern South America. In the present study, jundiá oocytes used were obtained by extrusion from females after hormone injection. Soon after hydration, the eggs were transferred to 50 L conic glass incubators, with constant and controlled water influx. Samples of fertilized eggs were transferred to Petri dishes and, examined under a stereoscopic microscope, were spherical, demersal, and non-adhesive with defined perivitelline space and resistant chorion. Cleavage stages occurred during the first 3.5 h. After hatching, larvae were transferred to 200 L glass fiber incubators. First signs of embryo movement were observed 21 h after fertilization; larval eclosion occurred 30.5 h after fertilization. Present findings may provide a basis for studies aimed at determining the complete ontogeny of jundiá and may be useful in eco-toxicological studies.

O jundiá (Rhamdia quelen, Quoy & Gaimard) é uma espécie endêmica da América do Sul. Por ser adaptada ao frio do inverno e ter um crescimento rápido durante os meses quentes, o jundiá é uma espécie adequada para aqüicultura no sul da América do Sul. Muitos aspectos da fisiologia reprodutiva, larvicultura, hematologia, fisiologia da resposta ao estresse, têm sido recentemente estudados. Os ovócitos utilizados neste estudo foram obtidos pela extrusão de fêmeas após indução hormonal. Logo após a hidratação, foram transferidos para incubadoras cônicas de vidro com capacidade para 50 L, com fluxo de água constante e controlado. Amostras de ovos fertilizados foram colocadas em placas de Petri e examinadas através de estereomicroscópio. Os ovos eram esféricos, demersais e não-adesivos, com espaço perivitelino definido e córion resistente. Os estágios de clivagem ocorreram durante as 3,5 primeiras horas. Após a eclosão, as larvas foram transferidas para incubadoras de fibra de vidro de 200 l. Os primeiros sinais de movimento embrionário foram observados 21 h após a fertilização, e a eclosão das larvas ocorreu 30,5 h após a fertilização. Estes resultados podem servir como base para muitos estudos, objetivando o conhecimento da ontogenia completa do jundiá, e para aplicação em estudos ecotoxicológicos.

Embryonic and larval development of jundiá (Rhamdia quelen, Quoy and Gaimard, 1824, Pisces, TeleosteI), a South American catfish.

The jundiá (Rhamdia quelen, Quoy and Gaimard) is an endemic South American fish species. Because this species supports cold winters and grows faster during warm months, it has begun to be viewed as an ideal species for fish production in southern South America. In the present study, jundiá oocytes used were obtained by extrusion from females after hormone injection. Soon after hydration, the eggs were transferred to 50 L conic glass incubators, with constant and controlled water influx. Samples of fertilized eggs were transferred to Petri dishes and, examined under a stereoscopic microscope, were spherical, demersal, and non-adhesive with defined perivitelline space and resistant chorion. Cleavage stages occurred during the first 3.5 h. After hatching, larvae were transferred to 200 L glass fiber incubators. First signs of embryo movement were observed 21 h after fertilization; larval eclosion occurred 30.5 h after fertilization. Present findings may provide a basis for studies aimed at determining the complete ontogeny of jundiá and may be useful in eco-toxicological studies.

Steroid profiles in cultured female jundiá, the Siluridae Rhamdia quelen (Quoy and Gaimard, Pisces Teleostei), during the first reproductive cycle.

The jundiá Rhamdia quelen (Quoy and Gaimard) is a teleost species from the Siluridae family and is an important species for aquaculture in temperate and subtropical climates. Gonad and blood tissue samples were taken from cultured jundiá females between 1998 and 1999. Plasma concentrations of 17beta-estradiol (E(2)), testosterone (T), 11-ketotestosterone (11-KT), 17-hydroxy-4-pregnene-3,20-dione (17-P), 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P), and 17,20beta,21-trihydroxy-4-pregnen-3-one (20beta-S) were measured by radioimmunoassay and potential correlations with the stage of oogenesis and sexual maturation examined. During the experimental period two spawning episodes were observed. Plasma concentrations of E(2) increased progressively during oocyte development, simultaneously with the appearance of yolk vesicles and increasing amounts of deposited yolk. In female jundiá, the T peak occurred in October and was coincident with the peak in gonadosomatic index. Two distinct peaks of progestogens were detected, corresponding to the two spawning episodes, suggesting that one or more of these steroids might act as the "maturational-inducing steroid" in jundiá. Unusually large amounts of 11-KT were also measured in the plasma of mature jundiá females. The identity of 11-KT was confirmed by thin-layer chromatography. Although the profiles of the other steroids are compatible with the roles proposed for the action of these hormones in other teleosts, the role of 11-KT, normally found only in males, is unknown.

The effects of two different periods of weight-reduction on selected performance parameters in elite lightweight oarswomen.

Six successful members of the British Women's Lightweight Rowing Team were assessed before and after two-month (1990) and four-month (1991) periods of weight-reduction controlled by reduced caloric intake, while engaged in their normal physical training. Fat free mass (FFM) was calculated from body weight (BW) by utilising total body potassium measurements. Maximal oxygen intake (VO2max), respiratory anaerobic threshold (Tvent), upper body anaerobic peak power (PP) and mean power (MP) outputs, and knee flexor (KF) and extensor (KE) isokinetic peak torques were among the physiological parameters assessed. No statistical differences were noted between the data obtained prior to the two weight-reduction periods, and both periods resulted in lower BW (p < 0.001) and FFM (p < 0.05); approximately 50% of the lost BW was FFM. At the end of the two-month weight-reduction period Tvent (p < 0.02) and KF (p < 0.02) decreased. In contrast, a similar BW loss during the four-month period was associated with higher VO2max (p < 0.01) and PP (p < 0.05) compared with values prior to weight reduction. Comparisons between the percentage changes pre to post BW loss showed that the longer weight-reduction period was associated with significantly improved VO2max (p < 0.01), Tvent (p < 0.005), PP (p < 0.05) and KF (p < 0.05). We conclude: a) the proportion (50%) of weight lost as FFM in the present elite rowers is higher than the suggested optimal figure of 22%, and b) compared to four months, 6-7% of BW loss over two months may adversely influence fitness-related parameters in international lightweight oarswomen.

The nutritional sensitivity of the diurnal cycling of body protein enables protein deposition to be measured in subjects at nitrogen equilibrium.

In adults in overall protein balance on intakes of protein equal to or greater than minimum requirements, the diurnal pattern of feeding and fasting results in cycling of body protein, with fasted losses and fed state gains of increasing amplitude with increasing habitual protein intake. Measurement of the slope of the fed state gain-intake relationship enables investigation of the ability of various patient groups to utilise dietary protein, without the need to impose negative nitrogen balance due to sub-maintenance protein intakes.