Life History of Spirorchis Elephantis (Cort, 1917), a New Blood Fluke from Chrysemys Picta

Cercaria elephantis, named and briefly described by Cort (1917) from Douglas Lake, Cheboygan County, Michigan, was thought by him to be a schistosome. This species of cercaria, along with the cercaria of Spirorchis parr us, first came to my attention in the summer of 1938 when they were found emerging from the snails Helisoma trivolvis (Say) and H. campanulatum (Say), collected from tributaries of the Huron River and from lakes and ponds inhabited by turtles in Washtenaw County, Michigan. At first the two species of cercariae, which are of about the same size and similar in most of the details of the excretory system and in the arrangement of their other organ systems, were considered by me to constitute a single species of schistosome cercaria. Attempts were made to infect several species of birds and mammals, with negative results. Fishes, frogs and salamanders were also exposed to them, likewise without results. Nine species belonging to seven genera of turtles were next exposed to the cercariae and one species proved to be susceptible. In the spring of 1939 this species, Chrysemys piet?, was infected; all others were negative. The finding of two species of blood flukes in some of these experimental turtles suggested that two species of cercariae had been used in the infection experiments. Further investigation proved this surmise to be correct. The two species of cercariae, when subjejeted to careful study, although superficially similar, showed significant differences in size and form of certain organs as well as in their habits of swimming and in positions assumed in floating and resting. The first species proved to be the cercariae of Spirorchis parvus (Stunkard, 1923) whose life history was briefly related by me (Wall, 1939, 1940) and is more fully described by me (Wall, unpublished research). The other was identified as the cercaria of Spirorchis elephantis. This infection experiment with turtles, noted above, furnished the clue to the definitive host of Spirorchis elephantis and led to the investigation of its life history, and to the establishment of a new group of cercariae (Wall, unpublished research).