|Top: a male glass frog attending its egg mass about 10 m above a stream. Middle: a crab on the same plant with a glass frog. Bottom: the reason why Hyalinobatrachium oriental are commonly called glass frogs. All photos JCM.|
Castroviejo-Fisher et al. (2008) report that Hyalinobatrachium orientale has a complex taxonomic history and they reviewed the species in an attempt to clarify the taxonomic status by means of morphological, bioacoustic, and mitochondrial DNA sequence comparisons of specimens from Tobago and the Venezuelan Cordillera de la Costa. They resurrected Hyalinobatrachium orocostale, and restricted it to the Cordillera del Interior. Additionally, they found specimens from Cordillera del Litoral and Oriental Sector do not form a monophyletic group; and define it as Hyalinobatrachium sp. H. orientale sensu stricto made up the populations from the Oriental Sector. And, they found preliminary bioacoustic and morphological analyses indicated that the populations from Tobago are conspecific with Hyalinobatrachium orientale sensu stricto.
In the last few days we (JCM, Stevland Charles, & Josh Traub) walked streams in northeast Tobago and observed Hyalinobatrachium orientale along several of them. While it is much easier to hear them than see them, one stream was more open and level. Delia et al. (2010) suggested the underside of the leaf protects the frogs from aerial predators – particularly bats of the genus Trachops that specialize in feeding on frogs. However, on Tobago crabs were readily apparent and on the same plants being used by frogs. Crabs are likely a serious predator on frogs and their eggs, and the underside the leaf position of could easily provide protection for eggs and adults. The egg masses we observed tended to be positioned toward the distil portion of the leaf, making it unlikely a crab could gain access to the eggs or adults. A second, frog predator observed near but not immediately adjacent to the frogs was the snake Leptodiera annulata ashmeadi. Most of the specimens we observed were hunting frogs in drains along the roads side.
Positioning calling males, amplexus, and egg deposition on the underside of a leaf has advantages.
Castroviejo-Fisher, S., J. Celsa Señaris, J. Ayarzagüena, and C. Vilà. 2008. Resurrection of Hyalinobatrachium orocostale and Notes on the Hyalinobatrachium orientale Species Complex (Anura: Centrolenidae) Herpetologica 64:472-484.
Delia J., D. F. Cisneros-Heredia, J. Whitney and R. Murrieta-Galindo. 2010. Observations on the Reproductive Behavior of a Neotropical Glassfrog, Hyalinobatrachium fleischmanni (Anura: Centrolenidae). Journal of South American Herpetology 5:1-12.
Vockenhuber, E. A., W. Hödl, and A. Amézquita. 2009. Glassy Fathers Do Matter: Egg Attendance Enhances Embryonic Survivorship in the Glass Frog Hyalinobatrachium valerioi. Journal of Herpetology 43(2):340-344.