Our objective was to assess the quality of eggs and juvenile of Nile tilapia (Oreochromis niloticus) from broodstock of three commercial hatcheries (H1, H2, and H3). Larval weight was significantly ...higher for H2 and H3 hatcheries (P < 0.05). After 45-day growth, weight of juveniles of H2 was higher, while specific growth rate was significantly higher for H1 and H2 (P < 0.05). After the ammonia stress test, no significant differences in mortality were found among larvae from the three hatcheries, although a positive relationship between carbohydrate content in eggs and juvenile mortality was observed (P < 0.05). After the salinity stress test, the lowest and highest mortality (P < 0.05) occurred respectively in tilapia larvae from the H1 (24.2%) and H3 (57.8%) hatcheries. We concluded that egg quality was not affected by tilapia broodstock from the three hatcheries studied, but differences were obtained for growth performance, carbohydrate content, and survival of juveniles when exposed to the salinity stress test. These three indexes should be considered as potential juvenile quality criteria for tilapia.
The relationship between the energy storage cycle and gametogenesis of the pearl oyster, Pinctada mazatlanica was studied over an annual cycle (January to December 1999). Histological analysis, ...combined with oocyte examination and measurements of carbohydrate, protein, total lipid, and triacylglycerides levels from gonadal tissue, digestive gland, and adductor muscle were performed. One-way ANOVA was used for assessing differences in the area of oocytes over time. Similarly, a two-way ANOVA was applied for differences in the biochemical composition of specimens over time and sex. The gametogenic cycle was affected by the presence of "La Nina" cold event during the first half of 1999. Gametogenesis commenced early in February and occurred synchronously throughout the annual cycle. There were two reproductive peaks, one in spring (March to May) and other in summer (July to September). A massive spawning was observed in September-October when water temperature was 29-29.5 degree C. Carbohydrates, either stored or obtained from ingested food, were used as an immediate fuel for the production of oocytes, which grew and increased their protein content during the first half of the year. Lipids and triacylglycerides also showed two important peaks in the female gonadal tissue and digestive gland, corresponding to the same peaks described histologically. Reserves stored in the muscle and digestive gland were actively used for gametogenesis. Muscle proteins were mobilized to the gonad during the first half of the year, while carbohydrates were used during the second half. The digestive gland acted as a short-term storage site of carbohydrates and lipids during gonad development. More studies on seasonal changes and energy storage and mobilization in pearl oysters are required, especially involving the participation of the mantle tissue.
The present study was designed to delineate the neuronal site, the nature, and the gastrointestinal origin of the stimulation of the hypothalamic magnocellular system induced by the ingestion of ...sweetened condensed milk. Concomitant localization of the c‐fos protein (Fos) with either arginine‐vasopressin (AVP) mRNA or oxytocin (OT) mRNA in the paraventricular nucleus of the hypothalamus (PVH) and the supraoptic nucleus (SON) revealed that the hypothalamic neurons containing AVP and OT were activated following ingestion of sweetened condensed milk. Expression of c‐fos mRNA was also determined in rats implanted with a gastric cannula that allowed for real, sham, and gastric feeding of sweetened condensed milk. The results provide evidence that the stimulation of the PVH and SON induced by sweetened condensed milk originate from oropharyngeal stimuli. Indeed, in real‐and sham‐fed rats, the postprandial levels of c‐fos mRNA in the PVH and SON were significantly higher than the preprandial values, whereas there was no early postprandial rise in c‐fos mRNA levels within the magnocellular division of the PVH and SON after gastric feeding. The results of this study also suggested that the stimulation of the PVH and SON induced by sweetened condensed milk was related to the hypertonicity of the milk. Indeed, ingestion of an hypertonic solution of sucrose with a carbohydrate content close to that of sweetened condensed milk led to a stimulation of the PVH and SON that was comparable to that induced by the milk, whereas ingestion of an isotonic solution of sucrose did not trigger any significant activation of the PVH and SON. Taken together, the present results indicate that magnocellular neurosecretory neurons are sensitive to oropharyngeal stimuli and further support the view of the existence of oropharyngeal osmoreceptors.
The present work deals with the existence of differential gonadal development between grafted and ungrafted specimens of the pearl oyster, Pinctada mazatlanica. Oysters were collected as spat and ...extensively cultured until they were suitable for pearl formation. A mantle allograft was placed within the gonadal tissue and the treated oysters were maintained under the same culture conditions as untreated oysters. After a year of Keshi pearl formation, samples of gonadal tissue, digestive gland, and muscle were excised from each oyster and used for histological and biochemical analyses. The histological examination of gonads was supported with measurements of the oocyte frequency and diameter and the use gonadic and muscle performance indices. For biochemical analyses, the concentration of carbohydrates, proteins, lipids, and triacylglycerides was studied. A two-way ANOVA was applied for differences in the oocyte diameter, index values, and biochemical composition of specimens over time and experimental treatments. All histological and biochemical results showed that grafted oysters achieved greater gonadal performance and were in better reproductive condition than the controls. They presented higher gonadic index values and lower muscle performance index values than untreated specimens. In addition, grafted oysters showed higher concentrations of lipids and triacylglycerides in the gonadal tissue and digestive gland and lower concentrations of proteins in the muscle than ungrafted oysters. Apparently the mantle allograft stimulates redirection of energy flows to reproduction and gonadal development. The muscle and digestive gland (particularly the former) are the main sources for this energy-requiring process. A neuroendocrine control involving the formation of a complex relationship between both mantle and gonadal tissues is suggested. More studies of the histological, histochemical, biochemical, and endocrine composition of mantle of pearl oysters are required to confirm these findings.
Inorganic elements, calcium (Ca), magnesium (Mg), zinc (Zn), copper (Cu), iron (Fe), and manganese (Mn), were quantified at the end of a commercial hatchery cycle in muscle and hepatopancreas of ...adult male and female white shrimp, Penaeus vannamei, newly caught from the wild. The duration of the hatchery cycle is about 100-120 days, during which unilaterally eyestalk-ablated females and intact males had continual reproduction. Calcium in muscle and Mg in muscle and hepa-topancreas were lower in males and females at the end of the hatchery cycle, compared to those in newly caught wild animals. The trace elements (Zn, Cu, Fe, and Mn) in muscle were higher in animals from the hatchery than in newly caught animals. When compared to newly caught organisms, females at the end of the hatchery cycle had lower hepatopan-creas levels of Zn and Cu, an effect not observed for males. In the hepatopancreas of hatchery organisms (males and females), Fe was decreased and Mn increased compared to values in animals from the wild. The present results showed that changes in shrimp-tissue mineral composition occur during the hatchery cycle, at the end of which reproductive exhaustion is attained. Some of these changes may reflect metabolic adjustments to intense reproduction or transfer of some elements to gonads accompanied by hepatopancreas depletion.
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