Turbellarian taxonomic database

Abstract / Notes

The pools characteristic of Stone Mountain and similar granite outcrops near Atlanta, Georgia have, from
November to April, a turbellarian fauna consisting almost exclusively of three new species, each from a
different one of the three fresh-water orders. The rhabdocoele is Mesostoma georgianum, a black,
cigar-shaped
form which is by far the most abundant. The large populations of this species are in part maintained by its
unusual ability to prey upon the numerous collembolans and upon its production of resistant eggs, which
remain viable in spite of extreme heat and desiccation during the summer. Serially sectioned specimens form
the basis for the study of the internal morphology; also, observations on the reproductive behavior were
reported, as well as studies based upon specimens sectioned in copula. On the basis of internal morphology
an
affinity with Mesostoma macroprostatum Hyman is indicated. The order Tricladida is represented by a slender,
white form, Phagocata bursaperforata, in which the lack of eyes and of body pigment resemble hypogean
species. From the morphology of the reproductive system it is suggested that this triclad is related to
Phagocata morgani (Stevens and Boring). The order Alloeocoela is represented by the prorhynchid worm,
Geocentrophora marcusi, a small, red-pigmented form found only on Mt. Panola. Serial section studies form
the
basis for the description of the internal morphology; laboratory observations on its ability to encyst are
presented. Certain features of these new species - pigmentation, reproduction, encystment - are discussed
with regard to their possible survival value in the unusual habitat of the granite outcrop pools.

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