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

Abstract

The chaetotaxy of cercaria of the echinostome Echinostoma miyagawai, found in naturally infected Planorbis planorbis in a brackish water lake in Bulgaria, is described and figured. Comparisons with sensory patterns of cercariae 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 & Brygoo (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. revolutum 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). Comparisons of chaetotaxy of cercariae of E. echinatum and its synonym E. lindoense (sensu Kanev, 1985, 1994) showed differences in the CII4, CIII3, CIII4, CIV4, CIVD, ventral A and dorsal A and P groups, and indicated that incomplete and contradictory information has been provided for E. echinatum by Kanev et al. (1987). Examination of the descriptions of the sensilla in cercariae of E. jurini and E. caproni suggested that the two species are indistinguishable with respect to their chaetotaxy. Comparative analysis of the variability of a total of 27 groups of cercarial sensilla reveals three sets of characters which are not useful in discrimination between the species of the 'revolutum' group because they exhibited either constancy (CI1, CII1, CII2, CIV1, MD, PDL), intraspecific variability (CIII1, CIII2) or overlapping ranges (CII3, CIII3, CIV2, tail sensilla).