The Relationship of Body Length and Weight in the Litopenaeus vannamei Populations Detected Enterocytozoon hepatopenaei

Abstract:

Microsporidia Enterocytozoon hepatopenaei (EHP) was detected using probe based real-time PCR from 442 shrimp coming from 5 farmed Litopenaeus vannamei populations in Tianjin, Zhejiang, and Shandong Province. The biological length and body weight of shrimp were measured individually. The Rohrer’s ponderal index (PI, W/L3) originally used in medical science was introduced in this study to establish the fuction of body weight (W) and biological length (L) of shrimp. The results showed that the PI of 4 EHP positive populations with an average biological length at (5.37±1.19) cm was calculated as (5.19±0.26)× 10–3 g/cm3, while that of the EHP negative population with an average biological length was (7.96±0.51)×10–3 g/cm3. After adjusting of the difference of PI caused by biological length according to the function PI=a×L(b–3), the PI of EHP positive populations was about (70.5±8.7)% of that of the EHP negative populations at the same biological length. It indicated that the average body weight of shrimp in an EHP positive population was about 30% smaller than that of shrimp with same size in biological length in an EHP negative population. The coefficient of variation (CV) of biological length and body weight in EHP positive populations was (2.39±0.93) times and (2.05±0.86) times of those in the EHP population, respectively, suggesting significant size variation in the EHP positive populations. The deviation ratio of actual body weight to body weight estimated on biological length in the EHP positive populations was 2.34 to 3.45 times of that in the EHP negative population, indicating the shrimp with same size in the EHP positive populations had greater fluctuation in body weight.