Single Snail Research Articles

An Experimental Test of the Life Cycle Described for Cotylurus communis (Hughes)

On the basis of experiments conducted in 1926 and 1927, Van Haitsma (1930) presented a description of the life cycle of a strigeid trematode designated by him as Cotylurus michiganensis. Later, La Rue (1932) pointed out that the correct name for the species is Cotylurus communis (Hughes, 1928). Van Haitsma demonstrated by feeding experiments that strigeid metacercariae identified as Tetracotyle communis Hughes found on and about the hearts of common suckers, Catostomus commersonnii (Lacepede), became adults of C. communis in the bursa Fabricii of the herring gull, Larus argentatus (Pont.). He then collected eggs from the bursae of the experimentally infected gulls and allowed them to embryonate. Seven species of snails were exposed to the miracidia which developed. One of the snails, a specimen of Lymnaea emarginata angulata Sowerby (= Stagnicola emarginata angulata), produced large numbers of strigeid cercariae forty days later. This snail had been collected from Douglas Lake and kept in the laboratory three weeks before it was exposed to the miracidia. The intestine of the gull, from which the eggs used in this particular experiment were obtained, harbored two specimens of a species of Diplostomum. The bursa contained many specimens of C. communis. Van Haitsma concluded that the single snail mentioned had been infected experimentally and that the cercariae belonged to C. communis. He stated that similar experiments conducted in 1928 yielded the same results but he did not describe these experiments. Cort and Brackett (1937) considered the cercariae obtained by Van Haitsma to be identical with C. emarginatae Cort, 1917 which was described from the same host in the Douglas Lake Region. Szidat (1931, p. 166) questioned the validity of the life cycle of C. communis as outlined above. He believed that the location of the penetration glands in the cercariae of members of the same genus should be similar. Since the penetration glands of Van Haitsma's cercaria lie behind the ventral sucker while those of the cercaria of C. cornutus are

Cercaria douglasi Cort, 1917 and Its Relation to the Cercaria of Cotylurus flabelliformis (Faust, 1917)

Cercaria douglasi was described briefly by Cort (1917) from a species of Physa from the Douglas Lake Region, Michigan. Later Cort and Brooks (1928) identified as this species cercariae from Lymnaea stagnalis appressa Say, L. stagnalis perampla Walker, Stagnicola emarginata angulata (Sowerby), and Physa parkeri Currier. Their description, however, was from the cercariae that emerged from three specimens of the varieties of L. stagnalis. Subsequent investigations have revealed that cercariae in the Douglas Lake Region, previously identified as C. douglasi, actually represent two distinct but closely related species. One of these, which is found only in members of the PHYSIDAE, we identify as C. douglasi Cort, 1917; the other, which develops only in members of the LYMNAEIDAE, was mistakenly identified by Cort and Brooks as C. douglasi. This second species has been shown by van Haitsma (1930) to be the cercaria of Cotylurus flabelliformis (Faust, 1917). Since Cort's original description of C. douglasi was very brief and was made from cercariae obtained by autopsy from a single snail, a redescription of this species is presented. Also, C. douglasi is compared with the cercaria of C. flabelliformis with which it has been confused.

Studies on Larval Trematodes from Kentucky with a Summary of Known Related Species

Although larval trematodes have received much attention in adjacent states, abstracts of the present study (Cable, 1935a, b) constitute the only record in the literature of cercariae from Kentucky. The present report is limited to the trematode parasites of a single snail species, Goniobasis semicarinata (Say), collected over a period of three years in the vicinity of Berea, Kentucky. These collections have yielded four new species of cercariae of types not commonly reported from freshwater habitats in the United States. For this reason, it seems desirable to describe these forms as completely as possible.

A New Harmostome Adolescaria from Campeloma decisum Say

During April and May, I933, large numbers of a gastropod, Campeloma decisum Say, were collected at Constantia, N. Y., from a pond formed by a dam across Frederick Creek, and serving as a reservoir for the operations of the State Fish Hatchery. All of the snails collected proved to be females,1 and were found to be IOO per cent infested with a larval trematode belonging to the Harmostomidae. This larva was in the adolescaria stage, and lay packed in large numbers in the uterus of the snail. The worms were especially abundant in the proximal portion of the uterus, but were also numerous in the lower portion of the tube where they found lodgement between the developing young. They were both free in the lumen and attached to the wall by means of their suckers, and not surrounded by a cyst. Depending upon the size of the host from OO to 400 worms occurred in a single snail. In other species of this group the transfer of the adolescaria from the snail to the final host is accomplished when the latter eats the former. If this method of transfer applies in the present case then the final host must be some bird or mammal that occasionally feeds upon Campeloma. The worms are slow moving but very muscular, and have considerable powers of extension and contraction. For the most part when undisturbed they lie motionless at nearly full length upon the bottom of a dish of tap water. In life the larva is of a ruddy color. Seen in mass through the translucent walls of the oviduct they impart a salmon pink tinge to the organ.

Sex Studies of Schistosoma japonicum

Sex Studies of Schistosoma japonicum