Observations on the Segmental Anatomy of the Tapeworm, Mesocestoides variabilis Mueller, 1928, from the Opossum

Abstract

Recently one of us (J.W.W.) obtained several incomplete specimens of a tapeworm from the small intestine of the opossum Didelphis virginiana Kerr, from Mississippi. Unfortunately only incomplete strobilae were obtained and in no case was a scolex recovered. Hence no measurements on the total length of single specimens can be made nor can we determine the total number of proglottides in the strobila of the individual. However a sufficient number of both mature and gravid proglottides was obtained for making whole mounts and sections. A study of these segments from the same chain and from similar chains in the collection has convinced us all of our material belongs to the same species of tapeworm. Although our material came from the opossum, the size of the mature and gravid proglottides, the nature and arrangement of the musculature within the segment, the presence of rather large calcareous corpuscles and the nature of the egg-capsule of the fully gravid segment definitely determine the species to be identical with Mesocestoides variabilis Mueller, 1928. Since no complete strobilae were obtained we are permitted only to give a description of the anatomy of the segment. Such a detailed description seems to be timely since in our opinion no paper familiar to us on the group of tapeworms here considered adequately describes the connections made by the various ducts that compose the reproductive system. Therefore in the present paper we propose to give a somewhat extended description of the internal anatomy of the species and to present our observations on the dorso-ventral axis of the strobila as worked out by us from cross, sagittal and frontal sections of both the mature and gravid proglottides.