AmphibiaWeb - Leptodactylus insularum
AMPHIBIAWEB
Leptodactylus insularum
Caribbean Ditchfrog, San Miguel Island Frog
family: Leptodactylidae
subfamily: Leptodactylinae
 
Species Description: Resurrected Barbour species from 1906. Heyer WR, de Sa RO 2011 Variation, systematics, and relationships of the Leptodactylus bolivianus complex (Amphibia: Anura: Leptodactylidae). Smithsonian Contrib Zoology 635:1-58.

© 2017 Twan Leenders (1 of 5)
Conservation Status (definitions)
IUCN (Red List) Status Least Concern (LC)
CITES No CITES Listing
National Status None
Regional Status None
Access Conservation Needs Assessment Report.

   

 

View distribution map in BerkeleyMapper.
View Bd and Bsal data (7 records).

Description
Leptodactylus insularum is a moderately-sized frog with a snout-vent length range in preserved specimens of 94 – 170 mm in males and 103 – 154 mm in females. From a dorsal and profile view, the adult snout has an almost rounded appearance. They possess a distinct canthus rostralis. They also have a prominent tympanum with a smooth tympanic annulus. There are short lateral folds extending from their supratympanic fold at the rear of the tympanum to their posterior arm. Their arms are smooth. The fingers are typically lined with weak lateral ridges or have completely smooth fingers. Two rounded and pointed spines can be found on each thumb in males. The hind limbs have a distinct tarsal fold that lacks tubercles. Their toes have basal webbing. Males have moderate toe fringes while females have weak fringes. The toe tips are rounded, swollen, and larger than the rest of their toes. They have a smooth dorsum with distinct folds from their sacrum to the juncture of their legs and body. There is no display of particular glands. Sexually active males possess a central chest patch of tubercles (Heyer and Heyer 2013).

For larval description, please see Heyer and Heyer (2013).

Based on morphological characteristics, geographical range, and genetics L. insularum is placed in the Leptodactlus bolivians complex, which includes L. bolivianus, and L. guianensis. Originally, these frogs were thought to be one species. Differences in adult male thumb spines is an easy way to distinguish between the species: L. insularum possesses two rounded and pointed spines on each of their thumbs while L. guianensis has a modestly chisel-shaped bone on a single spine and L. bolivianus has an extremely chisel-shaped spine bone (Heyer and Heyer 2013).

Their dorsum has dark mottled marks scattered between their dorsolateral folds. Both the supratympanic folds and the folds from behind the eye to their sacrum are distinct and dark. They also possess a dark, interrupted stripe from their nostril to their eye. Their posterior thighs display a boldly dark mottled pattern with large light irregular spots on a dark background, and their flank bares irregular dark brown spots on a tan to brown background. They have very light tan bellies with small tan dots, visible under a microscope, growing slightly darker towards the throat (Heyer and Heyer 2013).

Leptodactylus insularum displays morphological variation based on sex. Secondary sexual characters in males include central chest of tubercules and thumb spines. Coloration may also vary in lateral ridge stripe and posterior thigh color based on geography (Heyer and Heyer 2013).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Colombia, Costa Rica, Panama, Trinidad and Tobago, Venezuela

 

View distribution map in BerkeleyMapper.
View Bd and Bsal data (7 records).
Leptodactylus insularum is commonly found on the Pacific coast of Costa Rica, southern regions of Panama, northern parts of Colombia and Venezuela, and the island of Trinidad (Heyer and Heyer 2013). Although L. insularum was previously grouped with the species L. bolivianus and thought to live on both the islands of Trinidad and Tobago, L. insularum has only been recorded on Trinidad (Barren et al. 2020).

The species lives in a range of habitats such as forests and swamplands. They are found in lower elevations, but no known maximum elevation has been recorded (IUCN 2020).

Life History, Abundance, Activity, and Special Behaviors
Leptodactylus insularum is a terrestrial, nocturnal frog that breeds during the rainy season, from May to November, and build nests in shallow ponds or along the shoreline (Hurme 2014).

Males call at night from shallow waters, often after heavy rainfall (Hurme 2014). Leptodactylus insularum calls are short and quick, single notes with a minimum call rate of 0.63 per second and a maximum of 2.47 per second, averaging at 1.17 calls per second. There are three harmonic frequencies that each raise to a higher frequency than the last. The total ranges of frequencies are between 340 Hz to 2440 Hz (Heyer and Heyer 2013).

The species uses inguinal amplexus for mating in shallow water. Nest creation occurs with the female producing a thick mucus that the male aerates into a foam nest. The eggs are deposited into the nest, floating but hidden underneath leaves (Hurme 2014).

Females watch over the nest and tadpoles, signaling to them by a “pumping” action of their abdomen that encourages the tadpoles to keep close and follow her. If the tadpoles are in a small water body that is close to drying up, the mother will dig a route for them to swim into a nearby water source (Hurme 2014).

Leptodactylus insularum are generalist predators and eat many aquatic insects such as Elateridae, Formicidae, Belastomatidae, and Lycosidae (Mageski et. al 2014).

Tadpoles feed on decaying matter that falls to the lentic systems and benthic zones they inhabit (Heyer and Heyer 2013).

Adults use aposematic coloring on their hind legs, which they will showcase by stretching out their legs and inflating their abdomens in a defensive behavior (Franzen 2017).

Trends and Threats
The IUCN Red List has L. insularum listed as “Least Concern” because of its large distribution, wide range of habitats, and presumed large, stable population. The species is also tolerant of habitat change and is known to breed in ditches and fields. They are known to persist in areas with chytrid. Climate change may affect this species’ breeding timing (IUCN 2020).

Relation to Humans
Recently, skin secretions from the Leptodactylus insularum have been found to produce peptides, Ocelattins, that represent a template for the design of long-acting, non-toxic, and broad-spectrum antimicrobial agents that can be used to target multidrug-resistant pathogens. Specifically, Ocellatin-3N was active against an antibiotic-resistant strain of Klebsiella pneumoniae and reference strains of Escherichia coli, K. pneumoniae, Pseudomonas aeruginosa, and Salmonella typhimurium (Barran et al 2020). Ocelattins, in general, are peptides found in the skin secretions of the Leptodactylus genus. This peptide could be monumental in public health.

Possible reasons for amphibian decline

Climate change, increased UVB or increased sensitivity to it, etc.

Comments
In 1906, the species was first described from the island of Saboga in the Gulf of Panama based on 12 specimens (Heyer and Heyer 2013). On the IUCN website, the species is recognized as the San Miguel Island frog. More recent published use the common name Caribbean Ditch Frog for L. insularum (Hedges et. al. 2019). Currently, this species holds both common names, however, the former has been used more frequently in past publications.

This species was featured as News of the Week on 2 August 2021:

Most amphibians secrete distasteful or toxic substances from their skin. Several groups wield toxins that can be lethal to other animals, or even to themselves. Animals can evolve resistance to toxins through mutations in proteins that prevent toxins from binding. Although these mutations can provide resistance, they often occur in important regions of a protein, such as those critical to nervous system functions. Thus, a problem arises: how can animals avoid the negative effects of mutations that also provide resistance? A pair of recent studies, one on the toxic salamanders Taricha (Gendreau et al. 2021) and another on frogs of the genus Leptodactylus (Mohammadi et al. 2021), which consume toxic toads, suggest that gene duplication is the key; one gene copy can help animals develop toxin resistance while the other copy maintains a functional nervous system. Both studies also show evidence for a fascinating molecular process known as gene conversion, wherein duplicate copies of one gene retain more similar-than-expected DNA sequences. During homologous recombination, two copies of a genome line up and exchange pieces of DNA; however, when two copies of a gene are near each other in the genome, the wrong genes can line up and exchange genetic material, maintaining genetic similarity between duplicate copies of a gene. In newts, gene conversion appears to have copied resistance-conferring mutations from one gene domain to another. In Leptodactylus frogs, strong natural selection countered the force of gene conversion, resulting in one toxin-resistant gene and one toxin-sensitive gene. How newts and frogs regulate the use of these different gene copies remains unknown and will be an exciting future research topic. (RT)

References

Barran, G., Kolodziejek, J., Coquet, L., Leprince, J., Joulenne, T., Nowotny, N., Conlon, M., Mechkarska, M. (2020). "Peptidomic analysis of skin secretions of the Caribbean frogs Leptodactylus insularum and Leptodactylus nesiotus (Leptocactylidae) identifies an Ocellatin with broad spectrum antimicrobial activity." Antibiotics, 9(10), 1-15. [link]

Franzen, M. (2017). "Leptodactylus insularum (San Miguel Island frog) defensive behavior." Herpetological Review, 48(3), 607-608. [link]

Hedges, S. B., Powell, R., Henderson, R. W., Hanson, S., Murphy, J. C. (2019). "Definition of the Caribbean Islands biogeographic region, with checklist and recommendations for standardized common names of amphibians and reptiles." Caribbean Herpetology, 67, 1-53.

Heyer, W. R., Heyer, M. M. (2013). "Systematics, distribution, and bibliography of the frog Leptodactylus insularum Barbour, 1906 (Amphibia: Leptodactylidae)." Proceedings of the Biological Society of Washington, 126(3), 204-233. [link]

Hurme, K., J. (2014). "Reproductive and spatial ecology of Leptodactylus insularum (Anura, Leptodactilidae) in Panama." Journal of Herpetology, 48(4), 1-11. [link]

IUCN SSC Amphibian Specialist Group. 2020. "Leptodactylus insularum". The IUCN Red List of Threatened Species 2020: e.T85854383A85910948. https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T85854383A85910948.en. Downloaded on 17 February 2021.

Mageski, M., Falcao, A., Ferreira, R. B. (2014). "Leptodactylus insularum (San Miguel Island frog) diet." Herpetological Review, 45(1), 113-114. [link]



Originally submitted by: Marguerite Schlutius, Victoria Cao, Vanessa Martinez (2021-06-21)
Description by: Marguerite Schlutius, Victoria Cao, Vanessa Martinez (updated 2021-06-21)
Distribution by: Marguerite Schlutius, Victoria Cao, Vanessa Martinez (updated 2021-06-21)
Life history by: Marguerite Schlutius, Victoria Cao, Vanessa Martinez (updated 2021-06-21)
Trends and threats by: Marguerite Schlutius, Victoria Cao, Vanessa Martinez (updated 2021-06-21)
Relation to humans by: Marguerite Schlutius, Victoria Cao, Vanessa Martinez (updated 2021-06-21)

Edited by: Ann T. Chang (2021-08-03)

Species Account Citation: AmphibiaWeb 2021 Leptodactylus insularum: Caribbean Ditchfrog <https://amphibiaweb.org/species/7722> University of California, Berkeley, CA, USA. Accessed Jan 19, 2022.



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Citation: AmphibiaWeb. 2022. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 19 Jan 2022.

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