Emerald Glass Frog, Nicaragua Giant Glassfrog
© 2011 César L. Barrio Amoros (1 of 44)
Espadarana prosoblepon is a medium-sized centrolenid frog (Cisneros-Heredia and McDiarmid 2007), measuring 21-28 mm in males and 25-31 mm in females. The head is broader than it is long, with a truncate snout, and appears round when viewed from above (Savage 2002). The eyes are large and bulging, with a horizontally elliptical pupil (Leenders 2001), and the space between the eyes measuring less than the diameter of one eye (Savage 2002). The tympanum is indistinct. Vomerine teeth are present in a slightly diagonal patch between choanae, separated medially (Savage 2002). Bones and intestines are visible through skin, although the intestines are less discernible because they are covered by a white membrane, the parietal peritoneal sheath (Leenders 2001; Savage 2002). The skin is smooth, although there are two regions where the skin becomes granular: on the belly below the vent and on the ventral surface of the thighs. On the thighs, the granular skin surrounds cloacal ornamentations (a pair of warts, one on each thigh) (Cisneros-Heredia and McDiarmid 2007).
Finger I is longer than finger II. The fingers and toes have truncate discs, and the disc on finger III usually has a diameter equal to that of the eye (Cisneros-Heredia and McDiarmid 2007). Fingers are webbed, although there is no webbing between fingers I and II. A bubble-like structure called the “bulla” is embedded in the webbing between the outer fingers (Cisneros-Heredia and McDiarmid 2007). Toe webbing is moderate. The webbing formula for fingers and toes is as follows: Fingers = II 2-3 ¾ III 2 ½-1 ½ IV. Toes = I 1+-2 ½ II 1 ½-1 ¼ III 1 ¼-2 ¼ IV 2 ½-1 ½ V (Savage 2002). On the hand, the thenar tubercle is elongate, and the palmar tubercle is round and large; on the foot, the inner metatarsal tubercle is small, flat, and elongate, and the outer metatarsal tubercle is small and ovoid. There is no tarsal tubercle. A well-developed nuptial pad is present on outer lateral and dorsal surfaces of the thumb base in adult males (Savage 2002). Breeding males also develop conspicuous, abundant spicules. All males have a sharp, protruding spur on the upper arm called the humeral spine. Females and juvenile males will sometimes exhibit an underdeveloped version of the spine (Cisneros-Heredia and McDiarmid 2007).
Dorsal surfaces are emerald green, usually with black flecks. False ocelli, (irregular light spots surrounded by ill-defined dark borders, which form a reticulated pattern) are present in some specimens (Cisneros-Heredia and McDiarmid 2007). Finger coloration is slightly paler than the dorsum (Cisneros-Heredia and McDiarmid 2007). The ventral coloration is yellow (Savage 2002). Bones are green because of the presence of biliverdin (Cisneros-Heredia and McDiarmid 2007). The iris is gray/silver (Leenders 2001) and has a fine, dark reticulation (Cisneros-Heredia and McDiarmid 2007).
At stage 25, the total length of the tadpole is 12.3 mm (Starrett 1960). The larval body shape is elongate and somewhat depressed, with a long, rounded tail and very low fins (Starrett 1960). Tadpoles have dorsal, C-shaped eyes and dorsal nostrils (Starrett 1960). The mouth is ventral and nearly terminal, with wide, papillate lips (Starrett 1960). It has a complete oral disc with medium-sized beaks and 2/3 rows of denticles present (Starrett 1960; Cisneros-Heredia and McDiarmid 2007). The spiracle is midlateral, posterior, and sinistral (Starrett 1960). The vent tube is long and medially located (Starrett 1960).
At hatching the tadpole is black (Starrett 1960), with the coloration changing later in development to a pale brown dorsally; the ventral coloration is lighter but can appear bright red (Savage 2002). There are brown dorsal and lateral streaks on the musculature and fins anteriorly, with uniform coloration posteriorly except for the fin margins (Starrett 1960).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Colombia, Costa Rica, Ecuador, Nicaragua, Panama
This species is found along the Caribbean from Honduras to Colombia, and along Pacific slopes from Honduras to Ecuador (Guyer and Donnelly 2005). It is found at elevations ranging from 20-1,900 m in humid lowland, premontane and lower montane zones of wet and moist forests and rainforests (Savage 2002). The preferred habitat consists of densely vegetated areas of lowland and foothill seasonal and non-seasonal evergreen forests, and semideciduous evergreen forests, along the banks of fast-moving streams (Savage 2002; Cisneros-Heredia and McDiarmid 2007).
Life History, Abundance, Activity, and Special Behaviors
The males are very territorial and will each occupy a space on the streamside at intervals of approximately 3.2 m, with spacing determined by calling (Savage 2002). Males vocalize from leaf perches and are most vocal during the wet season, from May to November. The calls consist of a rapid and condensed "dik-dik-dik", given at a relatively low rate of 1 to 43 calls per hour (Savage 2002). Note duration is 1.5 to 3 seconds, and the dominant frequency is 5.3 to 6.0 kHz (Jacobsen 1985).
If one male invades another’s territory, the two males will wrestle with their arms while dangling upside down, holding onto vegetation with their legs (Savage 2002). Wrestling can last up to thirty minutes, ending when one male drops from the vegetation or signals submission by flattening his body against a leaf substrate and then leaving (Savage 2002).
Breeding occurs during the rainy season, May to November (Savage 2002). The male initiates amplexus by jumping on the female’s back and grasping her, while continuing to call (Savage 2002). The pair may stay in one place or move up to 2 m away (Savage 2002). This species is oviparous. Egg deposition takes place from approximately 2:30 am until sunup, and occurs on the upper surfaces of leaves, moss-covered rocks, or branches, from 0-3 m above the water (Savage 2002). Starrett (1960) also reported a clutch fastened between two leaves, with the upper leaf partially covering the clutch. Each egg (including the envelope) has a diameter of about 10 mm (Starrett 1960). A clutch consists of about 20 black eggs, and is laid in a monolayer about 50 mm in diameter, with a thin, loose film of jelly covering the clutch (Starrett 1960). Females initially stay with the clutch for minutes or hours, but once they leave, neither parent returns (Savage 2002). After 10 days, tadpoles hatch from the eggs and drop into the stream underneath (Guyer and Donnelly 2005).
Trends and Threats
This species has experienced significant decline in Monteverde, Costa Rica since the 1980s, although it is stable in other parts of its range and is quite abundant in Panama and Nicaragua (IUCN 2006).
Possible reasons for amphibian decline
General habitat alteration and loss
The karyotype is 2N = 20 (Duellman 1967).
A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).
Cisneros-Heredia, D. F., and McDiarmid, R. W. (2007). ''Revision of the characters of Centrolenidae (Amphibia: Anura: Athesphatanura), with comments on its taxonomy and the description of new taxa of glassfrogs.'' Zootaxa, 1572, 1-82.
Duellman, W. E. (1967). ''Additional studies of chromosomes of anuran amphibians.'' Systematic Zoology, 16(1), 38-43.
Guyer, C., and Donnelly, M. A. (2005). Amphibians and Reptiles of La Selva, Costa Rica and the Caribbean Slope: A Comprehensive Guide. University of California Press, Berkeley.
IUCN, Conservation International, and NatureServe. (2006). Global Amphibian Assessment: Centrolene prosoblepon. www.globalamphibians.org. Accessed on 2 March 2008.
Jacobsen, S. K. (1985). ''Reproductive behavior and male mating success in two species of glass frogs (Centrolenidae).'' Herpetologica, 41(4), 396-404.
Leenders, T. (2001). A Guide to Amphibians And Reptiles of Costa Rica. Zona Tropical, Miami.
Savage, J. M. (2002). The Amphibians and Reptiles of Costa Rica. University of Chicago Press, Chicago and London.
Starrett, P. (1960). ''Descriptions of tadpoles of Middle American frogs.'' Miscellaneous Publications Museum of Zoology, University of Michigan, 110, 5-37.
Written by Sarah Richman (sarah_richman AT berkeley.edu), UC Berkeley
First submitted 2008-02-28
Edited by Keith Lui (2011-10-05)
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