Necrotizing hepatopancreatitis (NHP) infected Penaeus vannamei female broodstock: Effect on reproductive parameters, nauplii and larvae quality

Necrotizing hepatopancreatitis (NHP) is a disease of cultured Penaeus vannamei caused by a gram-negative intracellular bacterium rickettsia-like organism. NHP was first reported in Texas in 1985, as being responsible for mortalities in shrimp ponds in Central and South America. The growth and proliferation of NHP within the hepatopancreatic epithelial cells is associated with anorexia, lethargy, abdominal muscle atrophy, softened exoskeleton, growth retardation and mortalities ranging from 20% to 95%. Although NHP can cause high mortalities in commercial ponds, it has been considered a problem only in broodstock ponds and maturation laboratories due to an increase in broodstock mortalities in Colombia. In order to evaluate additional negative effects at this level, we investigated the effect of NHP infection upon the reproductive behavior of females and the effect of maternal infection on nauplii and larval quality. Broodstock from NHP affected ponds were transferred to a maturation laboratory. After copula, females were transferred to individual spawning tanks. After spawning, females were sacrificed for histopathology and PCR analysis, while the eggs were placed in individual tanks for hatching. Females were classified into three groups according to their histopathological findings: NHP negative (n = 23) had no NHP lesions, positive for NHP with lesions grade 1 (n = 20) and NHP positive females with lesions grade 2 (n = 12). For each group, we analyzed the number of eggs, hatching percentage and number of nauplii per female. Our results show that females with NHP lesions grade 2 presented a significant reduction in the number of eggs and nauplii (P < 0.05) as compared with NHP negative females and females grade 1 NHP disease. No significant differences were found in hatching percentage among the three groups. Triglyceride levels in nauplii II were significantly higher in NHP negative females than in females with grade 2 NHP (P < 0.05), whereas there was no difference between NHP negative and grade 1 females. No significant differences were found for glucose and cholesterol levels in nauplii among the three groups. No differences were found in survival at zoea I, mysis I, PL-1 and PL-10 for the three groups. However, after a salinity stress test, the PL-10 survival decreased significantly in larvae from NHP positive females. Also a significant decrease in PL-10 length was also observed in the progeny of these females (grades 1 and 2). This study demonstrated that NHP disease in female shrimp spawners affects both maturation and larviculture causing a decrease in the number of eggs and nauplii per female, a reduction in the levels of triglyceride in nauplii II and decreasing larvae growth and resistance to osmotic stress test at PL-10 stage.