Stefania evansi

Stefania evansi is a species of frog in the family Hemiphractidae. Stefania evansi is, along with other closely related frogs, known for its unusual reproductive mode where females carry the eggs and juveniles on their back.[1][2][3][4] It is sometimes known under common names Groete Creek carrying frog, Groete Creek treefrog, or Evans' stefania (the "treefrog" designation can be misleading as Stefania are no longer included in the family Hylidae[3]). These names refer to its type locality, Groete Creek in the region Essequibo Islands-West Demerara, Guyana, where the holotype was collected by one Dr. R. Evans.[3][5]

Stefania evansi
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Anura
Family: Hemiphractidae
Genus: Stefania
Species:
S. evansi
Binomial name
Stefania evansi
(Boulenger, 1904)
Synonyms

Hyla evansi Boulenger, 1904[2]
Cryptobatrachus evansi (Boulenger, 1904)

Distribution and habitat

Stefania evansi is endemic to Guyana[6] and distributed in forested lowlands of west-central Guyana[5] at altitudes below 900 m (3,000 ft).[7][8] Frogs collected at higher altitudes probably represent Stefania scalae, a species that was for a while considered to be synonymous with Stefania evansi.[9][10] It generally occurs in habitats with low human impact and is not considered threatened.[1]

Description

Stefania evansi is one of the largest members of the genus: males grow to up to 53 mm (2.1 in) in snout–vent length and females to 98 mm (3.9 in).[3] Stefania evansi is dimorphic with respect to colouration: one morph is plain, and the other one is striped. A single brood can contain both morphs.[9]

Reproduction

As is typical for the genus, female Stefania evansi carry the eggs on their back and juveniles develop fully on their mother's back.[11] The eggs and juveniles are exposed but adhere to a mucus layer.[3][9] Brood size is variable: among 11 recorded clutches, it is 11–30 eggs and increases with female size; 30 eggs is the highest brood size recorded in the genus.[4] Eggs containing tailed, gilled larvae measure 8–9 mm (0.31–0.35 in) in diameter.[2] Eggs hatch on the female's back as froglets, without free-living larval stage.[4] Juveniles stay on their mother's back until they are about 19 mm (0.75 in) in length,[3] although smaller (17–18 mm (0.67–0.71 in) SVL) independent juveniles can also be found. It is speculated that the juveniles leave their mother's back when the resorption of the gill stalks is complete, coinciding with the consumption of all yolk. Juveniles may leave their mother also prematurely, showing residual gill stalks and yolk in their bellies, in response to stress caused by handling or predation.[9]

The duration of development and brooding is not known, but is assumed to require about 2–3 months. Breeding seems more frequent during—but not strictly restricted to—the rainy season.[12]

References
  1. IUCN SSC Amphibian Specialist Group (2019). "Stefania evansi". The IUCN Red List of Threatened Species. IUCN. 2019: e.T56026A120467204.
  2. Boulenger, G. A. (1904). "Description of a new tree-frog of the genus Hyla, from British Guiana, carrying eggs on the back". Proceedings of the Zoological Society of London. 1904 (Vol. II): 106 +1 plate. doi:10.1111/j.1469-7998.1904.tb08315.x.
  3. MacCulloch, R.D.; Lathrop, A. (2006). "Stefania evansi". Catalogue of American Amphibians and Reptiles. 827: 1–3.
  4. Salerno, P. E.; Pauly, G. B. (2012). "Clutch size variation in egg-brooding Stefania". South American Journal of Herpetology. 7: 47–54. doi:10.2994/057.007.0106.
  5. Frost, Darrel R. (2013). "Stefania evansi (Boulenger, 1904)". Amphibian Species of the World 5.6, an Online Reference. American Museum of Natural History. Retrieved 10 January 2014.
  6. MacCulloch, RD & A Lathrop (2006). "Stefania evansi". Catalogue of American Amphibians and Reptiles. 827: 1–3.
  7. MacCulloch, R.D. & A. Lathrop (2002). "Exceptional diversity of the genus Stefania (Anura: Hylidae) on Mount Ayanganna, Guyana; three new species and new distributional records". Herpetologica. 58: 327–346. doi:10.1655/0018-0831(2002)058[0327:edosah]2.0.co;2.
  8. MacCulloch, R.D.; A. Lathrop & S.Z. Khan (2006). "Exceptional diversity of Stefania (Anura: Cryptobatrachidae) II: six species from Mount Wokomung, Guyana". Phyllomedusa. 5: 31–41. doi:10.11606/issn.2316-9079.v5i1p31-41.
  9. Kok, P. J. R.; Benjamin, P. (2007). "Stefania evansi (Groete Creek Carrying Frog): Froglet carrying" (PDF). Herpetological Bulletin. 100 (Summer 2007): 38–39.
  10. Frost, Darrel R. (2013). "Stefania scalae Rivero, 1970". Amphibian Species of the World 5.6, an Online Reference. American Museum of Natural History. Retrieved 12 January 2014.
  11. Jungfer, K-H & W. Boehme (1991). "The back-pack strategy of parental care in frogs, with notes on froglet-carrying in Stefania evansi (Boulenger, 1904) (Anura: Hylidae: Hemiphractinae)". Revue française d'Aquariologie. 18: 91–96.
  12. Kok, P. J. R.; Bourne, G.R.; Benjamin, P.; Lenglet, G.L. (2006). "Stefania evansi (Groete Creek Carrying Frog). Reproduction" (PDF). Herpetological Review. 37: 212–213.
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