Infection by Hysterothylacium geschei (Nematoda: Anisakidae) in fish of Panguipulli Lake, Chile

Abstract

The objectives of the present study were: 1) to identify host fish of Hysterothylacium geschei in Lake Panguipulli, (39° 43'S, 72° 13'W), Chile, 2) to determine prevalence, mean intensity, and mean abundance of infection distributed by length and sex in each host, and 3) to determine the proportion of different developmental stages in each host. During September 2006 and January, May, and July 2007 the following fish were examined: 44 Odontesthes mauleanum (Atherinopsidae), 48 Basilichthys australis (Atherinopsidae), 25 Percichthys trucha(Percichthyidae), all natives, and 77 rainbow trout, Oncorhynchus mykiss (Salmonidae), the latter being an introduced species. All examined fish species presented infection by H. geschei and B. australis with O. mykissbeing new hosts to H. geschei. The infection was present in 4, 3, and 1 of 4 samplings of O. mauleanum, O. mykissand B. australis, respectively, and in 2 of 3 samplings of P. trucha. Third and fourth stage-larvae were present in the 4 hosts; males were identified in 3 hosts, except in P. trucha. The occurrence of gravid females was evident only in O. mauleanum. The prevalence (63.6%), and mean abundance (9.8) were significantly greater in O. mauleanum compared to the other hosts (prevalence: 8.3%-16%, mean abundance: 0.2-0.7). The mean intensity (15.3) was significantly higher in O. mauleanum compared to P. trucha (1.3) and O. mykiss (1.9). Mean intensity was similar among O. mauleanum and B. australis (8.8). The prevalence, mean intensity, and mean abundance of infection were similar between sexes in all hosts. The abundance of infection was positively correlated with length for O. mauleanum and O. mykiss, which was not evident in P. trucha and B. australis. The L3 recruitment in O. mauleanum occurred in all the months of the study.