MONOGENETIC TREMATODES OF FRESHWATER FISHES:NOTE ON ANCYROCEPHALUS WITH DESCRIPTIONS OF TWO NEW SPECIES

The present paper deals with nine speeies of genus Ancyrocephalus collected fromJiayu County, Hubei Province, located,at the middle Yangtze Valley. Two species,A. scorpioidalis and A. flexuosus, are described as new to science. Diagnoses of thenew species are given below.1. Ancyrocephalus scorpioidalis sp. nov.(Fig. 1) Host: Paracanthobrama guichenoti. Location: Gills. Locality: Jiayu County, Hubei Province. Description: Body length 0.59--0.92mm, width 0.074--0.14mm. Pharynx 0.029--0.035×0.029 mm in size. Opisthohaptor 0.061--0.074×0.061--0.11 mm in size. Marginal hooklets 0.014--0.022mm in length. Ventral central large anchors0.027--0.029 mm in total length, basal portion 0.017--0.022mm, outer root 0.003 mm,inner root 0.015-0.018 mm, point 0.012--0.015 mm. Ventral connective plate 0.004×0.039--0.044mm in size. Dorsal central large anchors 0.036--0.042 mm, basal portion0.032mm, inner root 0.015--0.018mm, outer root 0.001--0.002mm, point 0.012--0.015 mm. Dorsal connective plate 0.010×0.030--0.036 mm in size. Copulatory tube curved and crescent in shape, 0.042--0.047mm. The supportingapparatus 0.026--0.032mm. Vagina 0.019--0.020mm in total length. Description is based on 5 specimens. Remarks: This worm is similar to A. assimilis Gussev, 1955 in the shape of thedorsal and ventral large anchors but differs from the latter in the shape of the malegenitalia and structure of the vagina.2. Ancyrocephalus flexuosus sp. nov.(fig. 2) Host: Hemirhamphus sajori. Location: Gills. locality: Middle Yangtze Valley in Jiayu. Description: Body length 0.35--0.50mm, width 0.16--0.18 mm. Opisthohaptor 0.061--0.074×0.15--0.18 mm in size. Marginal hooklets 0.013--0.023 mm in length. Ventral central large anchors 0.022--0.024 mm, basal portion 0.020--0.022mm, inner root 0.008--0.010mm, outer root 0.002--0.003mm, point0.008--0.010mm. Ventral connective plate 0.002--0.003×0.042--0.054mm. Dorsalcentral large anchors 0.022--0.024mm in total length, basal portion 0.020--0.022mm,inner root 0.005--0.007mm, point 0.007--0.009mm, outer root 0.002mm. Dorsalconnective plate 0.002×0.044--0.054mm. Length of copulatory tube 0.12--0.15mm according to its curvature. The sup-porting apparatus 0.056--0.059mm in total length. Description is based on 5 specimens. Remarks: This worm differs from any other known species of the genus in thestructure of the male genitalia. All the types are deposited in the Department of Biology South China Teacher'College and in the authors' collection.