HeleophrynidaeGhost Frogs
This small family of stream-adapted frogs contains but one genus, Heleophryne, with which the family is often synonymized. There are two to five species, depending on author and definition. Distribution is restricted to the mountain streams in the southern tip of Africa.
These small to medium sized frogs (30 -65 mm snout vent length) are known as ghost frogs, perhaps because of their thin, white belly skin. As in glass frogs (Centrolenidae), abdominal muscles and organs can be seen through this skin. Several morphological characters in the ghost frogs reflect adaptations for life in fast-moving streams. They have expanded finger and toe tips, and fully webbed feet. The family is diagnosed by the lack of a beak in tadpoles. Tadpoles do have several rows of denticles, as well as a large, ventrally placed, suctorial oral disk -- a suction-cup shaped mouth with which it clings to rocks in fast water. The combination of tadpole head characters -- no beak, multiple denticle rows, and a large oral disk -- is otherwise unknown in anurans. Heleophrynids are further characterized by a lack of ribs, dentate upper jaws, eight ectochordal-amphicoelous presacral vertebrae with a persistent notochord, a vertically elliptical pupil, and the astragalus and calcaneum fused only at their ends. Diploid number is 26.
Ghost frogs live on and under rocks in cascading mountain streams. Unlike most neobatrachians, amplexus is inguinal. Clutch size is 100 - 200, and the large, unpigmented eggs are attached to rocks in quickly-moving streams. Typically, tadpoles that develop in cold, mountain streams take a long time to develop, and ghost frogs are no exception -- metamorphosis takes two years. At least one, and perhaps more, species are threatened by urban development.
Ghost frogs are unambiguously placed in the Neobatrachia, but relationships among the families of these "advanced" frogs is controversial at best. Most authors identify a superfamily, alternately called Bufonoidea or Hyloidea, which includes all the neobatrachians that are not Ranoids or Microhyloids. The group Bufonoidea is thus sketchy at best. Within Bufonoidea, ghost frogs may be related to the Australian family Myobatrachidae, which would imply an evolutionary divergence before Gondwana broke up and separated the modern-day southern landmasses. As with most current hypotheses of neobatrachian relationships, this is far from certain. Most neobatrachian phylogenies leave the relationship of Heleophrynidae to other clades unresolved.
No fossil ghost frogs are known.
Cannatella, D. 1996. Heleophryne: Tree of Life. (Website.) http://tolweb.org/tree?group=Heleophryne&contgroup=Neobatrachia
Cogger, H. G., and R. G. Zweifel, editors. 1998. Encyclopedia of Reptiles and Amphibians, 2nd edition. Academic Press, San Diego.
Duellman, W. E., and L. Trueb. 1986. Biology of Amphibians. Johns Hopkins University Press, Baltimore, MD.
Pough, F. H., R. M. Andrews, J. E. Cadle, M. L. Crump, A. H. Savitzky, and K. D. Wells. 1998. Herpetology. Prentice-Hall, Inc., Upper Saddle River, NJ.
Zug, G. R. 1993. Herpetology: an introductory biology of amphibians and reptiles. Academic Press, San Diego.
Contributors
Heather Heying (author).
Glossary
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- ectothermic
-
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- metamorphosis
-
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
- motile
-
having the capacity to move from one place to another.