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Fish Reproduction (fish + reproduction)
Selected AbstractsAltered reproduction in fish exposed to pulp and paper mill effluents: Roles of individual compounds and mill operating conditionsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2008L. Mark Hewitt Abstract For the last 20 years, studies conducted in North America, Scandinavia, and New Zealand have shown that pulp and paper mill effluents affect fish reproduction. Despite the level of effort applied, few leads are available regarding the factors responsible. Effluents affect reproduction in multiple fish species, as evidenced by decreased gonad size, decreased circulating and gonadal production of reproductive steroids, altered expression of secondary sex characteristics, and decreased egg production. Several studies also have shown that effluent constituents are capable of accumulating in fish and binding to sex steroid receptors/binding proteins. Studies aimed at isolating biologically active substances within the pulping and papermaking process have provided clues about their source, and work has progressed in identifying opportunities for in-mill treatment technologies. Following comparisons of manufacturing processes and fish responses before and after process changes, it can be concluded that effluent from all types of mill processes are capable of affecting fish reproduction and that any improvements could not be attributed to a specific process modification (because mills normally performed multiple modifications simultaneously). Improved reproductive performance in fish generally was associated with reduced use of molecular chlorine, improved condensate handling, and liquor spill control. Effluent biotreatment has been effective in reducing some effects, but biotreated effluents also have shown no difference or an exacerbation of effects. The role of biotreatment in relation to effects on fish reproduction remains unclear and needs to be resolved. [source] Lunar cycles and reproductive activity in reef fishes with particular attention to rabbitfishesFISH AND FISHERIES, Issue 4 2004Akihiro Takemura Abstract Cues from the moon influence synchrony in growth, feeding, migration, behaviour and reproduction of many reef fishes. Compared with comprehensive studies on the annual and daily activities of fish, few physiological studies have paid attention to the importance of lunar cues in reproductive activities. We review mutual and interesting relationships between fish reproduction and environmental changes induced by the moon, with particular emphasis on the reproductive activity of the rabbitfishes (Siganidae). Rabbitfish species exhibit, in nature, a definitive reproductive season, which differs among the tropical areas. During the reproductive season, synchronous spawning of rabbitfish is associated with a particular lunar phase. The lunar phase used by the respective species is similar in different regions on the earth. Histological observations revealed that gonads develop synchronously towards a peak around the spawning lunar phase, after which the gonads return to spent condition. Concomitant with gonadal development, sex steroid hormones were produced under the influence of gonadotropin (GtH). Injections of human chronic gonadotropin (hCG) to the fish that are undergoing active spermatogenesis accelerated testicular maturation. These results suggest that hormonal response in maturing the gonads in rabbitfish is under the regulation of GtH, and that pituitary secretion of GtH according to the lunar cycle accounts for the lunar rhythm in gonadal development. We speculate that the cues from the moon can be recognized by the higher parts of the hypothalamus,pituitary,gonadal axis. Possible relationships between exogenous environmental factors and the lunar-reproductive rhythm are also discussed. [source] Temporal distribution and composition of the ichthyoplankton from Leopoldo's Inlet on the Upper Paraná River floodplain (Brazil)JOURNAL OF ZOOLOGY, Issue 4 2002Reinaldo José de Castro Abstract Temporal distribution and composition of ichthyoplankton and their relationships with some environmental variables of Leopoldo's Inlet (Ressaco do Leopoldo) on the upper Paraná River floodplain, southern Brazil, were analysed. Samples were taken from February 1991 to February 1992, and 3480 larvae were collected. The highest density of larvae was observed in November 1991 (36.79 larvae/10 m3) at night (night/day ratio 7: 1). Species composition showed a predominance of Characiformes (80%). There was a high density (4.28 larvae/10 m3) of Bryconamericus stramineus throughout almost the whole study period. The majority of the species were more frequently collected at night. Pearson's correlation indicated a relationship between larval density, temperature, and pluviometric index. Leopoldo's Inlet, whose ichthyofauna is mainly composed of grazing and resident species, shows favourable conditions for fish reproduction and development. [source] Ascorbic acid and reproduction in fish: endocrine regulation and gamete qualityAQUACULTURE RESEARCH, Issue 8 2001K 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] | |||||||||||||