Phosphorus and calcium requirements in the diet of the American cichlid Cichlasoma urophthalmus (Günther)

An experiment was carried out with Cichlasoma urophthalmus (Günther) juveniles to determine the phosphorus requirement and its interaction with dietary calcium. Twelve isoenergetic and isoproteic diets were prepared using a basal artificial diet containing vitamin-free casein, dextrin, starch, corn oil, fish oil, vitamin mixture and a mineral mixture free of calcium and phosphorus. Calcium and phosphorus levels were determined in the casein. To the basal diets were added different concentrations of phosphorus as potassium monophosphate (0.5, 1.0, 1.5 and 2.5 g kg^–1) and calcium as calcium carbonate (0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0 and 4.0 g kg^–1). These concentrations resulted in varying Ca–P ratios (1:1, 1.33:1, 1.5:1, 1.6:1 and 2.0:1). Calcium and phosphorus concentrations in the water were 84 mg kg^–1 and 0.003 mg kg^–1, respectively. The diet with 0.5 g kg^–1 phosphorus resulted in deficiency signs such as reduced growth, high conversion ratio, high fat content and low bone mineralization. Increased levels of dietary calcium and phosphorus both gave improved growth and mineralization. Mineralization continued to increase with dietary phosphorus levels above that required for maximum growth. The optimum level of phosphorus in the diet was 1.5 g kg^–1, the optimum calcium level was 1.8 g kg^–1 and the optimum Ca–P ratio was 1.3. Carcass lipid levels were inversely related to dietary phosphorus.     

Histopathological Studies on Wild Broodstock of White Shrimp Penaeus vannamei in the Platanitos Area, Adjacent to San Blas, Nayarit, Mexico

In Mexico, the capture of wild broodstock of Penaeus vannamei or P. stylirostris for hatchery production of postlarvae is a common practice. During September 1995 and March-April 1996, high mortalities were observed in the wild broodstock captured in the Platanitos area, on the coast of San Blas, Nayarit, Mexico. As a result of these mortalities, many hatcheries closed down their facilities. Because early histological analysis had shown that some of these animals were infected with different pathological agents, such as bacteria and viruses, the present study was carried out to determine the prevalence and severity grade of infectious diseases affecting these shrimp. During March 1996, a total of 28 female and 28 male shrimp were randomly selected from a recently captured stock of 600 breeders of P. vannamei . A second sampling (28 females and 28 males) was performed from a stock of 800 breeders captured in April 1996. On this occasion, the shrimp were sampled after 10 d of acclimation in a hatchery. The animals selected for examination were those with necrosis in the cuticule, red coloration in the telson and uropods, soft cuticle, empty gut, and erratic swimming. All of the specimens were subjected to histological analysis and dot blot hybridization with a gene probe specific for Infectious Hypodermal and Hematopoietic Necrosis Virus (IHHNV). The results showed that both stocks were infected with at least three different viruses (Infectious Hypodermal and Hematopoitetic Virus, Taura Syndrome Virus and Hepatopancreatic Parvo-Like Virus), gram-negative bacteria and other parasites such as gregarines. It is likely that the high mortalities observed are due to the recent introduction of TSV in the wild population of P. vannamei .     

The effects of water temperature on food intake, growth and body composition of Cichlasoma urophthalmus (Günther) juveniles

The optimum growth, food intake, food conversion efficiency, final body composition and mortality of juvenile Cichlasoma urophthalmus (Günther) was studied at different temperatures, ranging from 22.5 to 36.3^°C. The results showed that food intake and specific growth rate increase rising to an apparent optimum at about 33.1^°C. Multiple regression equations were derived which can be used to predict food intake and specific growth rate when temperature and initial body weight are known.