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Centrolene prosoblepon

By Christina McArdle

Geographic Range

Centrolene prosoblepon is a small, arboreal frog that is found in the wet, lowland forests of Central and South America. It occurs along the Caribbean slopes of eastern Honduras through Central America to Panama, as well as along Pacific slopes from Colombia to Ecuador, which is its southernmost distribution. Centrolene prosoblepon is native to Honduras, Nicaragua, Costa Rica, Panama, Colombia, and Ecuador. (Cisneros-Heredia and McDiarmid, 2005; Guyer and Donelly, 2005; Henderson, 2002)

Habitat

Commonly known as emerald glass frogs, this species is found living in the vegetation of wet, tropical forests along rivers and streams. It occurs at elevations ranging from sea level to 2000 m. These frogs begin their lives in a terrestrial habitat, as an embryo within an egg clutch laid on a leaf overhanging a stream. As the tadpoles hatch, they drop into the water below, where they begin metamorphosis. Once they have reached adulthood, they return to the terrestrial habitat alongside the stream. (Beletsky, 2004; "IUCN Red List of Endangered Species", 2010; Jacobson, 1985)

  • Aquatic Biomes
  • rivers and streams
  • Range elevation
    0 to 2000 m
    0.00 to 6561.68 ft

Physical Description

Emerald glass frogs are small, green frogs that can exhibit dark green or black spots along the back. The body is translucent, which gives them their common name, and protects them from predation by allowing the background environment to show through. The translucent skin also makes it possible to see the frog’s internal organs, such as the beating heart, stomach, intestines, and blood vessels. The bones are green and also visible through the ventral skin. They have large eyes that are positioned approximately at a 45 degree forward angle. Although males and females both possess a humeral hook, a bony spike-like projection from the humerus, it is much larger on the male and can be used to grasp a challenger during male-male combat. When preserved, this species becomes light lavender in color. (Beletsky, 2004; Cisneros-Heredia and McDiarmid, 2007; Eaton, 1958; Guyer and Donelly, 2005; Henderson, 2002)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    3.75 (high) cm
    1.48 (high) in

Development

The eggs of Centrolene prosoblepon are laid on the upper surface of a leaf that is partially protected by surrounding vegetation above a flowing stream. On average, the egg mass is 50 mm in diameter. The eggs are spread in a single layer in loose jelly. The eggs are large, averaging 9 to 11 mm in diameter, and contain black embryos that develop in eight to twenty days. Immediately after hatching, the embryos are still black and average 12 mm in length. Once the tadpoles hatch, they drop into the stream below. This often occurs at a time of heavy rainfall, allowing the resulting turbidity to camouflage the tadpoles in the water. The body of the tadpole is elongate, having a tail that is over two times as long as the body. It possesses mouthparts that are well adapted to adhere to the stream substrate. Leaf litter on the bottom of the stream is used to conceal the tadpoles for several months while metamorphosis into their adult frog form is occurring. As adults, they live in vegetation along the stream. (Guyer and Donelly, 2005; Henderson, 2002; Starrett, 1960)

Reproduction

Emerald glass frogs have a polygynandrous mating system, in which males and females may have more than one mate throughout the mating season. Although males generally only tend to one clutch at a time, the literature has reported males tending to up to four clutches at one time. (Crump, 2000)

Emerald glass frogs are dioecious and breed through sexual external fertilization. The mating season begins in May and ends in September. Males use their call to attract females to their territory, which is a leaf suspended over a stream. When a willing female approaches, the male initiates amplexus by jumping on the females back. Throughout amplexus, as well as immediately after egg deposition, the male’s call is especially strong. Amplexus lasts on average 174 minutes, in which females release the eggs that are subsequently fertilized by a fluid containing sperm released by the male. After the eggs are deposited on the leaf top, the male may rub his hind legs over the female’s sides for a short period of time before hopping higher into the vegetation. (Jacobson, 1985)

  • Breeding interval
    Emerald glass frog breeding interval is not reported in the literature.
  • Breeding season
    Emerald glass frogs breed from May to September.
  • Range number of offspring
    20 to 50
  • Range time to hatching
    8 to 20 days

The literature presents conflicting information regarding parental investment. While recent information reports no parental care after egg deposition, a previous study conducted in Costa Rica reports parental care by both males and females post-egg deposition. Reproductive success may be correlated to the number of nights a male remains at the nest to protect his eggs. It has also been found that females occasionally remain on top of the clutch immediately after oviposition from 10 to 130 minutes. Female egg attendance is highly variable within the species and it does not seem to correlate to reproductive success. (Crump, 2000; Guyer and Donelly, 2005; Jacobson, 1985)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • protecting
      • male

Lifespan/Longevity

Emerald glass frogs have one of the highest and most stable adult survival rates for amphibians that have a lifespan over one year. A study of the survival and abundance of C. prosoblepon showed that the species has a mean weekly survival rate of 0.78 to 0.95, a monthly survival rate of 0.4 to 0.9, and an annual survival rate of 0.46. These high survival rates indicate a relatively long lifespan. In the wild, emerald glass frogs generally live up to 4 years, while some individuals may even live longer than 5 years. There is no information reported in the literature regarding lifespan in captivity. (McCaffery and Lips, 2013; Roberton, et al., 2008)

  • Range lifespan
    Status: wild
    5 (high) years
  • Typical lifespan
    Status: wild
    4 (high) years

Behavior

Emerald glass frogs are arboreal and nocturnal. Violent behavior between males is rarely seen, despite their territoriality during mating season. Combat usually consists of two males holding the bottom of a leaf with their hind legs while dangling upside down to grapple. Termination of combat may occur either by one of the males dropping to a lower leaf, or by one of the males flattening its body against a leaf. (Guyer and Donelly, 2005; "IUCN Red List of Endangered Species", 2010; Jacobson, 1985; Roberton, et al., 2008)

Home Range

Emerald glass frogs have strong fidelity to territories. A study conducted over two years in four Panamanian streams showed that on average they move sites 2.33 m, but most often do not move at all. Population studies have indicated that long distance migration may occur.

Communication and Perception

Most anuran species are very vocal. Emerald glass frog males use their call to attract female mates during breeding season, as well as to defend their breeding territory. The call is high-pitched and consists of three chirps or beeps, sounding like “chee-chee-chee”. Males also intermittently produce two-to-five chirp sequences. A rapid short series of beeps is often used when another frog is within 0.15 m of a calling male. There is no information reported in the literature regarding how they perceive their environment but, like other frogs, they are likely to use visual, auditory, and tactile. (Guyer and Donelly, 2005; Jacobson, 1985)

Food Habits

Like other frogs, emerald glass frogs are predatory as adults. Their main food source is invertebrates, mainly preying upon small insects, including orthopterans and coleopterans. Anuran tadpoles can either be predaceous, consuming aquatic invertebrates and occasionally other tadpoles, or herbivorous, consuming small bits of algae. There is no information about feeding habits of tadpoles of C. prosoblepon reported in the literature. (Guyer and Donelly, 2005)

  • Animal Foods
  • insects

Predation

Although little is known about predation on members of the family Centrolenidae, a study conducted in Costa Rica reported direct observations of predation on three glass frog species, including Centrolene prosoblepon. Observations took place at two different sites in which all three centrolenids were living sympatrically. Predation by various predators occurred in both pre-hatching and adult stages. A female Sesarma species crab was observed using her cheliped to pull an egg mass of Centrolene grandulosa off a leaf and into her mouth. Although the jelly encasing the egg mass hindered her progress, the crab was able to ingest 16 of 58 embryos in the clutch. Centrolene fleischmanni in the prehatching stages was observed to be preyed on by the phalangids, Prionostemma frontale. The spider used its chelicerae to slice the jelly capsule and reveal the eggs or embryos to be eaten. The early cleavage stages of the same species of glass frog were also preyed upon by a species of cricket, Paroecanthus tibialis. The only reported predation on C. prosoblepon occurred during its adult stages, in which a ctenid spider in the genus Cupiennus was observed after recently capturing the frog. The frog was weakly struggling while being held belly-up with its legs outstretched. The shoulder of the frog showed hemorrhage-like discoloration, which is where it was bitten by the spider. Another individual was found dead the next day with a discolored wound on its shoulder, similar in appearance and position to the bite on the previously observed frog. A ctenid was also observed preying upon C. fleishmanni, indicating that it may be a major predator on centrolenids. (Hayes, 1983; Henderson, 2002)

  • Anti-predator Adaptations
  • cryptic
  • Known Predators
    • graspid crab (Sesarma)
    • phalangid spider (Prionostemma)
    • gryllid cricket (Paroecanthus)
    • ctenid spider (Cupiennus)

Ecosystem Roles

A chytrid fungus, Batrachochytrium dendrobatidis (Bd), is the cause of an emerging infectious disease called chytridiomycosis that affects amphibians. The fungus affects the keratin levels in the skin of frogs, impeding diffusion through the skin and ultimately resulting in death. All amphibians are not affected equally by this fungus, leading scientists believe that some species may be more resistant to it than others. Antimicrobial peptides in the skin of amphibians may play a role in defending an organism against Bd. Emerald glass frogs are thought to have a relatively high resistance to the fungus due to its high survival rate throughout a massive species decline in 2004 that is thought to have been caused by chytridiomycosis. Variation seems to exist within the species and surviving populations are thought to have the highest level of resistance. Additional studies also found cutaneous bacteria in C. prosoblepon that produce anti-fungal metabolites. (Lauer, et al., 2008; Woodhams, et al., 2006)

Commensal/Parasitic Species
  • chytrid fungus (Batrachochytrium dentrobatidis)

Economic Importance for Humans: Positive

There is no information about the positive economic importance of emerald glass frogs.

Economic Importance for Humans: Negative

There are no adverse effects of emerald glass frogs on humans.

Conservation Status

The IUCN Red List currently classifies the conservation status of emerald glass frogs as least concern. They are widely distributed and are believed to have large populations. Much of the habitat in Colombia and Central America is in protected areas. Despite drastic population declines since the mid-1980s, the species has been able to persist at lower densities. Studies of gene flow and subpopulation movement suggest that populations within and between adjacent streams are connected due to long distance and upstream dispersal. This may have implications on conservation because it suggests that sites affected by population declines may be recolonized by individuals from unaffected sites. Populations are currently considered stable and do not show any signs of declining. Major threats are deforestation and pollution. Agricultural development, logging, and illegal crops are leading to a reduction in habitat for emerald glass frogs. Furthermore, spraying of the illegal crops leads to pollution in what is left of its habitat. Further investigation of the disease chytridiomycosis may determine it that is responsible for recent population declines in Costa Rica. ("IUCN Red List of Endangered Species", 2010; McCaffery and Lips, 2013; Roberton, et al., 2008)

Other Comments

The geographic range of emerald glass frogs has yet to be fully explored. As new species are being discovered, the monophyly of C. prosoblepon, as currently recognized, has been questioned by several scientists. (Cisneros-Heredia and McDiarmid, 2007)

Contributors

Christina McArdle (author), The College of New Jersey, Keith Pecor (editor), The College of New Jersey, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

arboreal

Referring to an animal that lives in trees; tree-climbing.

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.

carnivore

an animal that mainly eats meat

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

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.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

References

IUCN. 2010. "IUCN Red List of Endangered Species" (On-line). Accessed October 21, 2013 at http://www.iucnredlist.org/details/54934/0.

Beletsky, L. 2004. Travellers' Wildlife Guides Costa Rica. Northampton, MA: Interlink Books.

Cisneros-Heredia, D., R. McDiarmid. 2005. Amphibia, Centrolenidae, Centrolene peristictum, Centrolene prosoblepon, Cochranella cochranae, Cochranella midas, Cochranella resplendens, Cochranella spinosa, Hyalinobatrachium munozorum: Range extensions and new provincial records. Check List: Journal of Species Lists and Distribution, 1: 18-22.

Cisneros-Heredia, D., R. McDiarmid. 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.

Crump, M. 2000. In Search of the Golden Frog. Chicago, IL: The University of Chicago Press.

Eaton, T. 1958. An anatomical study of a neotropical tree frog Centrolene prosoblepon (Salientia: Centrolenidae). The University of Kansas Science Bulletin, 39: 459-472.

Guayasamin, J., M. Bustamante, D. Almeida-Reinoso, C. Funk. 2006. Glass frogs (Centrolenidae) of Yanayacu Biological Station, Ecuador, with the description of a new species and comments on centrolenid systematics. Zoological Journal of the Linnean Society, 147: 489-513.

Guyer, C., M. Donelly. 2005. Amphibians and Reptiles of La Selva, Costa Rica, and the Caribbean Slope. Berkeley, CA: University of California Press.

Hayes, M. 1983. Predation of the adults and prehatching stages of glass frogs (Centrolenidae). Biotropica, 15: 74-76.

Henderson, C. 2002. Field Guide to the Wildlife of Costa Rica. Austin, TX: University of Texan Press.

Jacobson, S. 1985. Reproductive behavior and male mating success in two species of glass frogs (Centrolenidae). Herpetologica, 41: 396-404.

Lauer, A., M. Simon, J. Banning, B. Lam, R. Harris. 2008. Diversity of cutaneous bacterial with antifungal activity isolated from female four-toed salamanders. The ISME Journal, 2: 145-157.

McCaffery, R., K. Lips. 2013. Survival and abundance in males of the glass frog Espadarana (Centrolene) prosoblepon in Central Panama. Journal of Herpetology, 47: 162-168.

Roberton, J., K. Lips, E. Heist. 2008. Fine scale gene flow and individual movements among subpopulations of Centrolene prosoblepon. International Journal of Tropical Biology and Conservation, 56: 13-26.

Starrett, P. 1960. Descriptions of Tadpoles of Middle American Frogs. Ann Arbor, MI: University of Michigan Museum of Zoology.

Woodhams, D., J. Yoyles, K. Lips, C. Carey, L. Rollins-Smith. 2006. Predicted disease susceptibility in a Panamanian amphibian assemblage based on skin peptide defenses. Journal of Wildlife Diseases, 42: 207-216.

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