Hyalinobatrachium fleischmanni (Boettger 1893)

Hyalinobatrachium fleischmanni is a relatively small frog with males ranging from 19.2 to 25.5 mm (Wild, 2003) and females reaching 23 to 32 mm (Guyer, 2005; Savage, 2002). This frog has a relatively flattened body, broad head, round snout, and forward-directed eyes. It has pale green skin with yellow or yellowish green spots and a white, partly transparent belly showing tiny white bones (Wild, 2003). The heart and anterior half of the liver are obscured by a white sheet of guanine. This layer of guanine also wraps around its digestive system (Guyer, 2005). Fingertips are yellow (Wild, 2003). The eye has a gold-colored iris surrounding a horizontally elliptical pupil (Leenders, 2001). Hyalinobatrachium fleischmanni is very similar in size and color to the Yellow-flecked Glassfrog (Cochranella albomaculata) and the Powdered Glassfrog (Hyalinobatrachium pulveratum). However, the latter two species have exposed digestive organs which are not wrapped in a white guanine sheath (Guyer, 2005).A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio) (http://darnis.inbio.ac.cr/FMPro?-DB=UBIpub.fp3&-lay=WebAll&-Format=/ubi/detail.html&-Op=bw&id=4388&-Find).

This frog ranges from Guerrero and Veracruz, Mexico, through Central America to Colombia, Venezuela, Guyana, and Surinam (Wild, 2003). It is arboreal and inhabits vegetation near moderate to fast flowing stream at lower elevation (Wild, 2003), sometimes in pastures and cleared sites (Savage, 2002).

This species is nocturnal and arboreal (Guyer, 2005). It can sometimes be found on the underside of a leaf several meters above the streams (Leenders, 2001). Male frogs are territorial. During the long mating season (early March to late November), males make an untrilled "wheet" sound and repeat it after a short pause. The louder the call, the more dominant the male is (Leenders, 2001). If the territory has been invaded by another male, the defending male gives off a "mew" call along with their normal mating call. If this call does not scare the invader away, the resident male will engage the invader in physical combat. The loser is pinned down on his ventral side and will withdraw when released. When a female approaches, the male call is a mixture of "mew" and "wheet" sounds (Savage, 2002). Females lay clutches of 18 to 30 eggs on the underside of a leaf just above a stream. During the incubation period, both males and females attend their eggs clutches by sitting on them during the night and sleeping near but not on the eggs during the day (Wild, 2003). The males sit on the egg mass and practice hydric brooding, which consists of occasionally excreting bladder water on the eggs to prevent desiccation (Guyer, 2005). However, if the males "overwater" the eggs it will cause the embryo to be more prone to fungal infection and predation by larvae of drosophilid flies (genus Zygothrica; Savage, 2002). The most common causes of embryo mortality are fungal infection, predation by frogfly larvae, and desiccation (Savage, 2002). Not much is known about the adult diet but it is assumed that they feed on small arthropods (Guyer, 2005). These frogs have many predators, particularly the ctenid spiders.

Hyalinobatrachium fleischmanni is probably the most abundant glassfrog in Costa Rica. It is not threatened (Leenders, 2001).