Effect of temperature on the survival and growth of freshwater prawns Macrobrachium borellii and Palaemonetes argentinus (Crustacea, Palaemonidae)

During the two-month rearing period, the effect of four water temperatures (15°C, 20°C, 25°C and 30°C) on survival rate, number of molts, and growth rate (molt increment and intermolt period) of juvenile Macrobrachium borellii Nobili, 1896 and Palaemonetes argentinus Nobili, 1901 prawns was evaluated in laboratory conditions. The two species showed some similarities in their both survival and growth pattern at different temperatures. The survival rate was highest at 20°C and 25°C, decreasing at the lowest temperature. The number of molts increased at higher temperatures, ranging the intermolt period from 22.2 days to 9.9 days, for M. borellii, and from 20.8 to 9.5 days for P. argentinus, corresponding those values to 15°C and 30°C, respectively. No difference between species was noted in the intermolt period. The size increment by molting increased significantly from 15°C to 25°C, whereas a reduction in the growth of prawns was observed at 30°C. Significant differences among temperatures were found in the slope of regressions between the size increment by molting and the cephalothorax length. M. borellii showed a significantly higher tolerance to elevated temperature and a faster growth (about twice at 25°C) than P. argentinus. These differences could provide M. borellii a competitive advantage for a better adaptation to the dynamic of freshwater environment, especially in areas with anthropogenic impact.

SNP analysis of Molting related genes in <i>Penaeus monodon</i> and <i>Litopenaeus vannamei</i> shrimp (Brief report)

Molting is a very important growth period in shrimp. During the intermolt cycle, the accumulations of carbohydrate protein provide steady growth. The molt-inhibiting hormone (MIH) and the crustacean hyperglycemic hormone (CHH) belong to a large neuropeptide family, which are involved in the regulation of the length of the intermolt period, keeping shrimp in the intermolt stage (GU et al., 2000; YODMUANG et al., 2004). There are two kinds of MIH (MIH1 and MIH2) and one CHH. Therefore, the MIH1, MIH2 and CHH genes are candidate genes for detecting polymorphisms associated with the molting pathway and growth

Temperature-dependent growth of the blue crab (Callinectes sapidus): a molt process approach

Crustaceans display discrete and biphasic growth as a result of the molting process, so the traditionally used von Bertalanffy growth model does not capture well the phenomena associated with molting-based growth. A molt-process model can predict crustacean growth, including the temperature dependence of intermolt period that can produce the extended overwintering phenomena during which growth ceases. This study parameterized a molt-process model for the blue crab (Callinectes sapidus; Portunidae). Crab growth histories were observed for individual crabs held in field enclosures and temperature-controlled, recirculating tanks. A growth-based temperature of torpor (Tmin) of 10.8 °C was determined. A mean growth per molt of 119.5% increase in carapace width was observed. The average intermolt period observed was 536 ± 231 degree-days. The predictive ability of these growth parameter estimates was evaluated against growth observed in the field based on data on interannual changes in size frequencies of crabs from a winter dredge survey. The evaluated model was used to explore recruitment timing in warm (1996) and cold (1998) years. A 10% shift in the timing of juvenile crabs becoming available for legal exploitation was predicted from the simulations.