Developmental pattern and larval stages of Polystoma indicum Diengdoh & Tandon, 1991 (Monogenea: Polystomatidae) in rhacophorid anurans.

摘要

The developmental pattern of Polystoma indicum in the urinary bladder of the frogs Rhacophorus nigropalmatus, R. reinwardtii and Polypedates leucomystax from Meghalaya (north-east India) was studied. A total of 648 adults were examined. Non-ciliatedlarval stages were recovered in the gyrodactyloid-I and post-gyrodactyloid-I stage mostly from the branchial chambers of the tadpoles; only rarely were they found in the intestines. These stages possessed features of bladder-destined forms and showed agradual acquisition of 2, 4 and then 6 opisthaptoral suckers, coupled with an increase in the size of the body and various structures. Although a conspicuous increase was noticeable in the dimensions of the hamuli, the size of the microhooks remained almost the same from the 2-suckered larval stage to the adult. The larval migration to the final destination seemed to follow an external route leading to the cloaca of the metamorphosing host. The prevalence data of both the larvae and the adult flukes indicated a preference towards R. nigropalmatus amongst the 3 rhacophorid host species. The gyrodactyloid-II (i.e. neotenic larvae) were not encountered at all, either on the external gills of the very young tadpoles or even in the branchial chambers of theolder ones.