Date of this Version
Aquaculture 287:3–4 (February 2009), pp. 271–277.
High levels of ciliate infestation can affect respiration, feed intake, and locomotion in farmed shrimps in the tropics. Information on seasonal variation of the infestation parameters of ciliates is scarce, but it would be useful for determining the suitability of preventive measures or therapeutic treatment if necessary. This study aimed to describe the prevalence and mean intensity of infestation (MII) of ciliates on wild native shrimps Penaeus (Farfantepenaeus) brasiliensis and P. (Farfantepenaeus) duorarum and farm-cultured juvenile shrimp Penaeus (Litopenaeus) vannamei over an annual cycle and to determine whether an association existed among physicochemical factors and infestation on cultured shrimp. The ectosymbiotic ciliates Acineta tuberosa, Epistylis sp., and Zoothamnium sp. infested both farmed and wild shrimps. Based on examination of 360 farmed specimens of P. vannamei (30 examined each month), the species with highest infestation were Epistylis sp., (prevalence range = 22 –100%; MII range = 13 ± 28 – 126 ± 124) and Zoothamnium sp. (0–87%; 0 – 144 ± 132). For both species, the highest values occurred during the rainy season. A total of 288 wild specimens of P. brasiliensis plus 120 of P. duorarum obtained during three recognized seasons—dry (February to May), rainy (June to September), and north-wind (October to January)—had ciliate infestations that were significantly lower than those from farmed shrimp. For P. brasiliensis, the ciliate species with the highest infestation values were Zoothamnium sp. (0–66%; 0.03 ± 0.2 – 66 ± 92), while on P. duorarum, were for Epistylis sp. (0–46%; 0 – 8 ± 16). Using multiple linear regression, we found significant relationships between stocking density, survival, temperature, turbidity, and intensity of infestation of the ciliates. However, the regression accounted for only 11–26% of the variance (R2), meaning that there are still other environmental and biological variables that should be included to increase the reliability of the model. Thus, the physicochemical conditions of the farm increase the probability of ciliate transmission, especially during the rainy season.