Gonad Growth (gonad + growth)

Distribution by Scientific Domains

Selected Abstracts

Plasma sex steroid concentrations and gonadal aromatase activities in African clawed frogs (Xenopus laevis) from South Africa

Markus Hecker
Abstract Adult African clawed frogs (Xenopus laevis) were collected from a corn-growing region (CGR) and a non-corn-growing region (NCGR) with different exposure profiles for atrazine and related triazines. Physical, chemical, and biological parameters from the catchment areas were also measured. Frogs were surveyed for possible effects of exposure to triazine herbicides on plasma testosterone (T) and estradiol (E2) titers, gonadal aromatase activity, and gonad growth (GSI). Concentrations of both T and E2 varied among locations and were correlated to some accessory factors, such as pH, several ions, and metals. Greatest median plasma T concentrations (males: 19 ng/ml; females: 16 ng/ml) occurred in frogs inhabiting NCGR as compared to those from the CGR (males: 4 ng/ml; females: 1 ng/ml). Median E2 concentrations were also greater in frogs collected from the NCGR (males: 3 ng/ml; females: 28 ng/ml) than those in frogs from the CGR (males: 2 ng/ml; females: 5 ng/ml). Because some exposure to agricultural chemicals at both regions occurred, as did simultaneous exposures to multiple chemicals, a regression analysis was employed. Negative correlations were observed between plasma T concentrations and concentrations of atrazine, deisopropylatrazine, deethylatrazine, and tertbuthylazine in females and between T and diaminochlorotriazine in males. Estradiol in females exhibited a significant negative correlation with atrazine and deethylatrazine. No correlations were observed between gonadal aromatase activity or GSI and any of the agricultural chemicals measured. Median aromatase activities in ovaries varied among sampling sites ranging from 7 to >3,000 times greater than those in males when measurable. Testicular aromatase activity was below the detection limit of the assay in male frogs at most of the sites. Although exposure to agricultural inputs did not affect aromatase activities, effects of atrazine or coapplied pesticides on sex steroid homeostasis cannot be excluded at this point. [source]

Reproduction of Micropogonias funieri in a shallow temperate coastal lagoon in the southern Atlantic

D. Vizziano
The white croaker Micropogonias furnieri, in the coastal Rocha Lagoon, spawned during 5 months, in late spring and summer. It was eurythermic (gonad growth at 12·5 to 25·5° C, spawning at 20 to 27° C) and mesoxic (living at 5·2 to 9·1 mg l -1). The spawning occurred in brackish (8,18 salinity), basic (c. 8 pH) and oxygenated (c. 8·0 mg l -1) waters. The temperature appeared to be an important environmental factor affecting the timing of reproduction. The size at first maturity (19,20 cm) was 11,12 cm lower than the reported for the Río de la Plata spawning area (Uruguay). Juveniles were observed throughout most of the year suggesting that the lagoon is also a nursery area. In Brazil, M. furnieri spawns in marine areas while in Uruguay it spawns in estuaries. This is the first time that a coastal lagoon of the subtropical and temperate western coast of the South Atlantic Ocean has been shown to be a spawning area of a marine species. [source]

The Effect of Dietary Carotenoids on Gonad Production and Carotenoid Profiles in the Sea Urchin Lytechinus variegatus

Larry R. Plank
Although dietary carotenoids are generally considered important in sea urchin aquaculture only for their effect on gonad color, they also have important biological roles. The effects of dietary carotenoids on gonad production and organ carotenoid profiles of Lytechinus variegatus were examined. Individuals were collected in January 1999 and fed a replete diet with a level of 0.60 mg carotenoids/kg for 4 wk, followed by one of four prepared diets for 8 wk: one without supplemental carotenoids, one with ,-carotene (16.92 mg carotenoids/kg feed), and two carotenoid mixtures, one high in zeaxanthin (5.28 mg carotenoids/kg feed) and another high in capsanthin (9.63 mg carotenoids/kg feed). The carotenoid profiles of the body compartments differed. The primary carotenoid in gonads of males and females was echi-nenone. The carotenoid profile of the test was similar to that of the gonad. The carotenoid profile of the gut varied with diet, but was not identical to composition of the diet. The gut profiles included echinenone but at lower concentrations than in the gonad and test. The carotenoid profile in the gut probably results from the presence of the carotenoids absorbed and those metabolized. The results suggest that several pathways exist to metabolize dietary carotenoids and that some of them are in the gut. The concentration of carotenoids in the gut (g wet weight) was higher than that of the gonad, which was higher than that of the test. The gonads increased significantly in size regardless of diet, indicating carotenoids are not required for gonad production under the conditions of this experiment. Although the concentration of carotenoids in the gonad decreased over time, the absolute amount of carotenoids increased with the increase in gonad size. Either gonad growth was more rapid than carotenoid deposition or differential deposition in nutritive cells and gametogenic cells occurred, or the amount of carotenoids used in the diets was too low to have an effect. [source]

Ascorbic acid and reproduction in fish: endocrine regulation and gamete quality

K Dabrowski
Abstract High ascorbic acid concentrations have been associated with gonad and brain tissues in teleost fishes. Although a direct dietary effect on gamete quality has been given some attention recently, the mechanism of action of ascorbate along the cascade of reproductive events in the hypothalamus, pituitary and gonads has not been defined. Data relating to gamete production and quality, as well as a possible protective role for ascorbate against cumulative genetic defects during gametogenesis and congenital malformation during gestation (embryonic development) is reviewed. It is suggested that the gonad growth in response to gonadotropin stimulation involves direct interaction between catecholamines and steroid hormones and their receptor sites. This interaction acts as a regulatory mechanism of ascorbate absorption, transfer and metabolism (degradation and/or renewal) in the reproductive system. We conclude that ascorbic acid is a leading nutrient in reproductive tissue functions and further research is needed on: (1) its antioxidant effect on gametes' (sperm and ova) capacity to prevent DNA damage occurring prior to (endogenous) and after spawning (environmental insults); (2) its dietary requirement to optimize survival and physiological recovery in multiple spawners; (3) the integration mechanism of ascorbic acid action as part of the overall endocrine regulation of neurohormonal,hormonal pathway in fish reproduction; and (4) the possible role for ascorbate in regulating fish maturation and/or infertility in the presence of enhanced UV-radiation or conditions of intensive aquaculture (hypoxia, oxygen supersaturation, dietary pro,, and antioxidants). [source]