Parvitaenia cochlearii (Cestoda: Gryporhynchidae) in a cultivation of Pacific fat sleeper Dormitator latifrons from Ecuador

Objective. To identify and determine the infection parameters of the metacestode Parvitaenia in different culture stages of Dormitator latifrons and to evaluate the histological damage caused by this parasite. Materials and methods. Forty-five specimens were examined, 15 in each phase: prebreeding, pre-fattening, and fattening, to identify the metacestode and tissue damage caused using conventional parasitology and histology techniques. Prevalence, intensity, and median intensity were calculated. A Mood's median test evaluated the difference between intensity per culture phase. Total length, weight, condition factor, and hepatosomatic index were correlated with intensity by linear correlation analysis. Liver fragments were evaluated to identify the tissue damage. Results. A total of 29,151 cestodes were found and were identified as Parvitaenia cochlearii. Cestode prevalence was 100% in each culture phase. The median intensity ranged from 22 to 625 individuals and showed significant differences between culture phases (X-2 = 29.391; p<0.0001). Intensity showed moderate positive correlation with total fish length (r(2) = 0.45; p<0.05) and low correlation with weight (r(2) = 0.38; p<0.05). In less parasitized livers, fibrosis, and congestion around the cysts were observed, while in livers with high levels of infection, parenchymal reduction, fibrosis, and increase in melanomacrophage centers were observed. Conclusions. This is the first report of P. cochlearii on D. latifrons in aquaculture. We suggest that there is a tendency for cestode accumulation during fish growth, which could have negative implications for trade.