Cercarial chaetotaxy of Echinostoma miyagawai Ishii, 1932 (Digenea : Echinostomatidae), with a review of the sensory patterns in the 'revolutum' group

The chaetotaxy of cercaria of the echinostome Echinostoma miyagawai, found in naturally infected Planorbis planorbis in a brackish water lake in Bulga ria, is described and figured. Comparisons with sensory patterns of cercari ae of E. revolutum, E. echinatum, Echinostoma sp.? echinatum, E. audyi, E. lindoense, E. trivolvis, E. caproni and E. jurini, described by Kanev et al . (1987), Lie (1966), Dimitrov et al. (1997), Richard (1971), Richard & Bry goo (1978) and Dimitrov & Kanev (1992), showed the distinct species status of E. miyagawai which exhibits a unique number and distribution of sensilla in 10 groups (CII4, CIV3, CIV4, CIVD, ventral A, M and P; dorso-lateral A and M, and lateral P). A comparison of the chaetotaxy of cercariae of E. re volutum and two descriptions of E. audyi revealed that the sensory pattern in E. revolutum was incompletely described and that the three descriptions differ in 9 of the 16 groups on the head collar and in all groups along the body which casts doubt on their synonymy (sensu Kanev, 1985, 1994). Compar isons of chaetotaxy of cercariae of E. echinatum and its synonym E. lindoen se (sensu Kanev, 1985, 1994) showed differences in the CII4, CIII3, CIII4, CIV4, CIVD, ventral A and dorsal A and P groups, and indicated that incompl ete and contradictory information has been provided for E. echinatum by Kan ev et al. (1987). Examination of the descriptions of the sensilla in cercar iae of E. jurini and E. caproni suggested that the two species are indistin guishable with respect to their chaetotaxy. Comparative analysis of the var iability of a total of 27 groups of cercarial sensilla reveals three sets o f characters which are not useful in discrimination between the species of the 'revolutum' group because they exhibited either constancy (CI1, CII1, C II2, CIV1, MD, PDL), intraspecific variability (CIII1, CIII2) or overlappin g ranges (CII3, CIII3, CIV2, tail sensilla).