Fisiología Y Calidad Reproductiva De Machos De Camarón Blanco [Litopenaeus schmitti] En Condiciones De Cautiverio
To satisfy the needs of shrimp farms of southern white shrimp Litopenaeus schmitti in Cuba, an increased mating success of pond-reared broodstock is needed in commercial hatcheries, and this objective depends mostly on the quality of males. Even though this species can reproduce in a closed life-cycle, batches of low-performance pond-reared males have been obtained. To analyze whether the system of tanks is partly responsible, in a first experiment, reproductive performance was compared in unisex and mixed tanks during a production period lasting 28 days. In a second experiment, reproductive performance, sperm quality, and physiological condition was compared between pond-reared and wild males throughout a production period of 70 days. In the first experiment, reproductive performance of mature females, mating success, fertilization rate, number of nauplii, hatching rate, and survival for both sexes did not differ between systems. Additionally, mating success increased significantly throughout the test period, with maximum values reached the third week after residence in maturation tanks. This indicated an adaptation of the shrimp to conditions in the commercial hatchery. Because reproductive performance was not different between the two systems, unisex tanks were used in the second experiment because they are more efficient for obtaining experimental data. Similar to the results of the first experiment, pond-reared and wild shrimp completely adapted after a month of residence in maturation tanks, as measured by reproductive indicators (mating success percentage, fertilization and number of nauplii); metabolic measures (protein and glucose levels in hemolymph); immunological indicators (total hemocyte count, phenoloxidase activity, and hemoagglutinating activity), as well as sperm quality (total sperm count and percentage of normal sperm). Nevertheless, after two months, practically all indicators suggested a poor reproductive performance and physiological and health ix condition. This decline was more accentuated in wild shrimp. Decline in physiological condition was determined by high values of phenoloxidase activity, as well as by a decline in total hemocyte count, hemoagglutinating activity, and glucose levels. This particular deterioration of wild males also corresponded to lower total sperm count, lower proportion of normal sperm, and higher levels of dead sperm. The poor physiological condition of the animals at the end of the experiment corresponds to a lower capacity of immune response and reproductive exhaustion, resulting from a high reproductive activity and an increase in water temperature. On the other hand, the increase in body weight, together with the decrease in lipids, low levels of total proteins in the hepatopancreas, and decline in the levels of proteins and glucose in hemolymph suggests that these specimens used part of their body reserves not only for reproduction, but for growth. This double use of energy can explain a more pronounced physiological exhaustion for wild males. In conclusion, the present results suggest that, after two months, shrimp attained a reproductive exhaustion enhanced by an increase in water temperature that produced a decline in reproductive performance. This decline was more accentuated for wild shrimp, because they were less tolerant to captivity conditions. In contrast, pond-reared males were more tolerant to these conditions indicating that their use is still an adequate strategy for production of postlarvae because they present better adaptation to conditions of captivity.
- 2. Tesis (CIP)