Degree Name

Master of Science (MS)

Semester of Degree Completion

1975

Thesis Director

Verne B. Kniskern

Abstract

The development of a method for karyotype determination of cercaria provides a basis for comparative karyotype analysis between cercaria and adult, possibly eliminating the need for infection experiments for positive identification of cercaria. Snails (Goniobasis livescens) were collected from below the spillway of Lake Charleston, on the Embarras River, near Charleston, Illinois. Of a total of 196 snails collected 42 (21.5%) were found to be infected with undetermined furcocyticercous cercariae. Infected snails were detected through isolation procedure. From the infected snails, emerged and non-emerged forms of the cercaria were recovered. Whole mounts of the cercaria were made and photomicrographs were taken for later use in identification.

Two drugs were utilized to arrest the chromosomes at the metaphase configuration: Colchicine, a drug widely used on other animal and plant tissue; and vinblastine sulfate, used by LoVerde (unpublished) on some species of the class Trematoda. The efficacy was compared by making simultaneous preparations using colchicine and vinblastine sulfate.

The squashes were examined under a light microscope. Photomicrographs were taken of the existing karyotypes. Although both drugs were successful in arresting mitotic cell division at metaphase, vinblastine sulfate was found to provide better delineated chromosome spreads. There was no difference between using non-emerged or emerged forms of cercaria.

Photomicrographs of the whole mounts and characteristics observed from the living cercariae were compared to species descriptions in the previous literature. The cercaria was identified as the cercaria of Proterometra macrostoma (Horsfall 1933). Positive identification through infection experiments was not attempted.

Twenty chromosomes were counted and characterized in an idogram. The karyotype provides a comparative tool for species identification of cercarial stage with the adult.

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