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| The Tobago Glass Frog, Hyalinobatrachium orientale tobagoensis Hardy, 1984. Photographed in northeast Tobago. A small (18-22 mm) frog that lives along fast moving streams, often near waterfalls. Eggs are deposited on the underside of leaves overhanging a stream so that hatching tadpoles drop into the water below. This species ranges from Meta, Colombia through the mountains of northern Venezuela and Guyana, with an isolated population in northeastern Tobago. It seems likely that this race will eventually be shown to be a species endemic to Tobago. Note the transparent nature of the skin on the ventral surface of the frog in the bottom photograph. |
Glass frogs range from Mexico to Argentina, and they can be found on the island of Tobago. These delicate, nocturnal, and at least partially transparent frogs live along streams and deposit their eggs on leaves over hanging the water. When the eggs are ready to hatch the tadpoles escape their gelatinous nest and drop into the stream below. The eyes are set high on the skull, and they have a single ankle bone and a single wrist bone (as opposed to two). Finger and toe tips are expanded into adhesive disks. Currently four genera and about 140 species are known from the neotropics. Few species reach more than 30 mm in total length. The genus Hyalinobatrachium derives its green color from the molecule biliverdin that is stored in the skin, and their eggs are also green from this same pigment. The other genera of glass frogs (Centrolenella, Centrolene, and Cochranella) have their green color as the result of structural modifications, that is they are not green because of a pigment. In these species the orange, yellow, and red wavelengths are absorbed by various layers and the green, blue and purple wavelengths are reflected. They are the sister to the Leptodactylidae and had a shared ancestor about 57.9 Ma (74-50 Ma). |