Estudos de helmintos da ordem Trypanorhyncha, parasitos de elasmobrânquios pescados no litoral sul do Estado do Rio Grande do Sul: taxonomia, prevalência e intensidade de infecção

Abstract

From 154 sharks captured off the south coast of Rio Grande do Sul State, Brazil (30°40'S - 33°40'S and 53°20'W - 50°40'W), 34(22.0%) were found parasitized by cestodes of the order Trypanorhyncha, representing four families, four genera and five species. Sphyrna zigaena (L., 1758), Galeorhinus vitaminicus Buen, 1950 and Squalus megalops (Macleay) were negative for parasites. The five parasitized host species are definitive hosts for six species of Trypanorhyncha, as follows: Sphyrna lewini (Griffith & Smith, 1834) for Nybelinia (Syngenes) rougetcampanae Dollfus, 1960; Carcharhinus brachyurus (Gunther, 1860) for Dasyrhynchus pacificus Robinson, 1965; Mustelus canis (Mitchill, 1815) for Callitetrarhynchus gracilis (Rudolphi, 1819), Nybelinia (Nybelinia) lingualis (Cuvier, 1817) and Eutetrarhynchus vooremi sp. n.; Mustelus schmitti Springer, 1939 for N. (N.) Lingualis and E. vooremi sp. n.; Notorhynchus pectorosus (Garmann, 1884) for N. (N.) bisulcata (Linton, 1889). xxi Adult specimens of D. pacificus and N. (S. rougetcampanae are described for the first time. Except for N. (N.) lingualis and C. gracilis the known geographical distribution of the remaining species is amplified. Prevalence regarding host species/parasitism, was of 40.5% in females and 13.5% in males of M. canis; 25.7% and 5.7% of N. schmitti respectively. 0nly females of C. brachyurus (25.0%), N. pectorusus (16.7%) and S. lewini (20.0%) were found harbouring parasites. Examined female hosts were of higher prevalence (26.2%) than the males (13.7%) and also showed higher mean infection intensity except for M. canis regarding the parasitism by E. vooremi sp. n. with values of 4.92 in the females and 5.25 in the males. This species was most frequent occurring in 90.0% of the M. canis and 100% of the M. schmitti specimens parasitized. Considering single and associated infections, it was observed that 75.0% of infected M. canis only harboured E. vooremi sp. n., 10.0% were found with E. vooremi sp. n. and N. (N.) lingualis and 5.0% with E. vooremi sp. n. and C. gracilis. Nybelinia (N.) lingualis also ocurred in 5.0% as a single infection and the association of this species with 5.0% of C. gracilis was observed in this host. In M. schmittii, E. vooremi sp. n. was associated (18.2%) with N. (N.) lingualis. Single infections of D. pacificus, N. (N.) lingualis and N. (S.) rougetcampanae were harboured by C. brachyurus, N. pectorosus and S. lewini, respectively.