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Dyscophus antongilii

By Aaron Rudolph

Geographic Range

Tomato frogs (Dyscophus antongilii) are native to Madagascar, specifically the northeastern part of the island. The species has been reported in areas like Antongil’s Bay, Andivoranto, Maroantsetra, and the Ambatovaky reserve. Other locations have been proposed, however confusion as to whether it was the tomato frog or a similar species (D. guineti) is unknown. Tomato frogs prefer a variety of areas in this range as long as there is a natural or manmade refuge, such as vegetation and detritus, and a stable, slow-moving water source. (Tessa, et al., 2007; Wisnieski, et al., 1997)

Habitat

This species of frog inhabits a variety of habitats throughout its range. These areas include both rainforest and wooded coastal areas, underbrush both wet and dry, and urban areas of varying levels of disturbance as long as there is somewhere to burrow. Eggs are laid are slow moving or stagnant waters whether found in natural wetland areas to urbanized drainage ditches and pools around houses and villages. Preferred habitat of this species is unknown, however it is known to thrive in the variety of settings it is present in. It occurs up to about 200 meters above sea level across its range. (Chiari, et al., 2006; Raxworthy, et al., 2008; Wisnieski, et al., 1997)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • temporary pools
  • Range elevation
    0 to 200 m
    0.00 to 656.17 ft

Physical Description

Tomato frogs gain their name due to the bright, reddish-orange coloration of their skin. The appearance of adults differs between the sexes. Females are known to be 8.5 to 10.5 cm long while males are slightly smaller at 6 to 6.5 cm. Males are also known to be less colorful than females almost appearing to be more brown than red. On the ventral portion of the frog the coloration goes from reddish to white. A black stripe is typically present from behind the eye to the abdomen. Tadpoles and young frogs are known to range from black to tan as they mature to adults. Adult coloration typically develops several months after hatching. (Raxworthy, et al., 2008; Tessa, et al., 2007; Wisnieski, et al., 1997)

  • Sexual Dimorphism
  • female larger
  • female more colorful
  • Average mass
    26 g
    0.92 oz
  • Range length
    6 to 10.5 cm
    2.36 to 4.13 in

Development

Tomato frogs lay their eggs in water with hatching as tadpoles occurring several days after oviposition. In captivity, typically the tadpoles began metamorphosing after approximately one month. Over several months the newly developed frogs transition from black to tan to red as they reach sexual maturity. (Segev, et al., 2012; )

Reproduction

Tomato frogs exhibit polygynandrous mating like most other anurans. In captive breeding programs, males have been recorded calling and amplexing females under simulated heavy rainstorms typical of the wet seasons in Madagascar. Such conditions are expected to be necessary for breeding in their native range. (Segev, et al., 2012)

Studies have shown that males calling for mates occurred at all months throughout both the wet and dry seasons in Madagascar. Observers also found eggs of the tomato frog in eleven out of twelve months. Most studies agree that reproduction is triggered after heavy rainfall events. After calling, the frogs begin amplexus after which several thousand eggs can be laid. Sexual maturity is typically reached between two to three years and breeding can occur throughout the year given the right conditions. (Segev, et al., 2012; Wisnieski, et al., 1997)

  • Breeding season
    Year-round
  • Range time to hatching
    2 to 4 days
  • Range age at sexual or reproductive maturity (female)
    2 to 3 years
  • Range age at sexual or reproductive maturity (male)
    2 to 3 years

Other than female investment in the provisioning of eggs, there appears to be no parental investment in this species.

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning

Lifespan/Longevity

Studies in the wild have shown that females can live as long as 11 years and males as long as seven. Those individuals that were larger typically lived longer. In captivity, tomato frogs are known to live more than 12 years. (Tessa, et al., 2007)

  • Typical lifespan
    Status: wild
    3 to 11 years
  • Typical lifespan
    Status: captivity
    3 to 12+ years

Behavior

Tomato frogs are generalists that live not only in their specified range, but are shown to adapt quite well to urban environments. They can typically be found in drainage ditches and farmlands where there is easy access to slow moving water and refuge. As shown in captivity, the species is fond of burrowing and will typically exhibit this behavior in soft substrate. Otherwise, few studies have been done on actual behavior in the wild. (Raxworthy, et al., 2008; Segev, et al., 2012; Tessa, et al., 2007)

Home Range

No data on home range size have been collected.

Communication and Perception

As is typical of other anurans, male tomato frogs communicate via calling to females in order to mate, and then by touch during amplexus. They locate prey visually. (Segev, et al., 2012; Wisnieski, et al., 1997)

Food Habits

Small invertebrates and arthropods are thought to be the most common source of food for juveniles and adults of this species. In captivity these animals are normally fed insects and worms. The larvae may be filter-feeders.

More information on the biomechanics of tongue use of a closely related species, D. guineti, is known that may give more insight into how they capture prey. In this relative, when the prey is at an angle of less than 40 degrees to the side of the mouth they only turn their head toward the prey. In this way the tongue is projected by the opening of the jaw as is typical of most frogs. However, when this angle is greater than 40 degrees they are able to propel their tongue at an angle out of line with the head. This allows them to have a wider radius of prey capture which appears to overcome the limited neck mobility. If true for the genus, tomato frogs utilize different ways to maximize the energy going into launching the tongue that including inertial elongation found in most frogs and a muscular hydrostatic mechanism for tongue aiming. (Monroy and Nishikawa, 2009; Monroy and Nishikawa, 2011)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • terrestrial worms
  • zooplankton
  • Other Foods
  • microbes

Predation

Information on predation of the tomato frog is limited. In the urban areas where these frogs are common, dogs and cats can be a problem. Besides a bright aposematic coloring, both D. antongilii and closely related D. guineti both have the ability to secrete a white, glue-like substance that can be mildly irritating to humans. A likely more important feature of these secretions is their glue-like properties which are among the highest observed among amphibians. The secretions have been shown to attach snakes to substrate and foul the eyes and digits of predatory mammals. (Andreone, et al., 2006; Evans and Brodie, 1994)

Ecosystem Roles

Details of their ecosystem role are lacking. However, as a generalist species it can be assumed that they feed on any moving prey item both in their aquatic and terrestrial environments. In captivity they are usually fed a mixture of crickets and mealworms. In the wild it can be assumed they too feed on a variety of insects. (Raxworthy, et al., 2008; Tessa, et al., 2007; Wisnieski, et al., 1997)

Economic Importance for Humans: Positive

Tomato frogs have been a popular choice for unique pets among those in the amphibian pet trade. Successful breeding lines have been established which has ended the practice of exporting the species from their native Madagascar. Today they are prized for their bright and vibrant red color in the terrarium set ups. (Andreone, et al., 2006; Raxworthy, et al., 2008)

Economic Importance for Humans: Negative

Like many anurans, the tomato frog has the ability to excrete a whitish mucous from its skin when disturbed. While not toxic to humans, it has still been shown in some cases to cause skin irritation and allergic reaction. (Andreone, et al., 2006; Raxworthy, et al., 2008; Wisnieski, et al., 1997)

Conservation Status

Tomato frogs are listed by the IUCN as a Near Threatened. Several species in the genus Dyscophus, including D. antongilii are listed in CITES Appendix II, meaning that exporters are supposed to have a permit from their government. There are calls for authorities in their home range in Madagascar to begin conservation efforts (mostly in terms of preventing habitat degradation), and to clean up pollution as a broader effort to protect all amphibian species in Madagascar. Export for the pet trade has also been halted for this species as captive breeding populations are now well established. Breeding populations in zoos are also closely monitored to promote genetic diversity as studies in the wild have observed an excess of homozygosity among microsatellite markers which could indicate a lack of genetic diversity. (Andreone, et al., 2008; Andreone, et al., 2006; Chiari, et al., 2006; Raxworthy, et al., 2008)

Other Comments

As exporting tomato frogs has been banned, zoos and other institutions in the pet trade have been working towards profiling breeding lines for the species. This is to ensure the genetic diversity and health of captive specimens. This work will aid promoting the overall genetic health of the species through responsible captive breeding and owning practices. (Andreone, et al., 2008; Andreone, et al., 2006; Chiari, et al., 2006)

Contributors

Aaron Rudolph (author), Indiana University - Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne, George Hammond (editor), Animal Diversity Web Staff.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

aposematic

having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

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

chemical

uses smells or other chemicals to communicate

choruses

to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species

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.

island endemic

animals that live only on an island or set of islands.

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).

marsh

marshes are wetland areas often dominated by grasses and reeds.

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.

oviparous

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

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

poisonous

an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).

polygynandrous

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

polymorphic

"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.

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.

saltatorial

specialized for leaping or bounding locomotion; jumps or hops.

scrub forest

scrub forests develop in areas that experience dry seasons.

sexual

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

suburban

living in residential areas on the outskirts of large cities or towns.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

tropical

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

urban

living in cities and large towns, landscapes dominated by human structures and activity.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

Andreone, F., A. Carpenter, N. Cox, L. du Preez, K. Freeman, S. Furrer, G. Garcia, F. Glaw, J. Glos, D. Knox, J. Kohler, J. Mendelson, V. Mercurio, R. Mittermeier, R. Moore, N. Rabibisoa, H. Randriamahazo, H. Randrianasolo, N. Raminosoa, O. Ramilijaona, C. Raxworthy, D. Vallan, M. Vences, D. Vietes, C. Weldon. 2008. The challenge of conserving amphibian megadiversity in Madagascar. PLOS Biology, 6(5): 943-946.

Andreone, F., V. Mercurio, F. Mattioli. 2006. Between environmental degradation and international pet trade: conservation strategies for the threatened amphibians of Madagascar. Natura, 95(2): 81-96.

Chiari, Y., P. Orozco-ter Wengel, M. Vences, D. Vietes, A. Sarvoy, J. Randrianirina, A. Meyer, E. Louis. 2006. Genetic identification of units for conservation in tomato frogs, genus Dyscophus. Conservation Genetics, 7(4): 473-482.

Evans, C., E. Brodie. 1994. Adhesive strength of amphibian skin secretions. Journal of Herpetology, 28/4: 499-502.

Monroy, J., K. Nishikawa. 2011. Prey capture in frogs: alternative strategies, biomechanical trade‐offs, and hierarchical decision making. Journal of Comparative Physiology, 315/2: 61-71.

Monroy, J., K. Nishikawa. 2009. Prey location, biomechanical constraints, and motor program choice during prey capture in the tomato frog, Dyscophus guineti. Journal of Comparative Physiology, 195/9: 843-852.

Raxworthy, C., M. Vences, F. Andreone, R. Nussbaum. 2008. "Dyscophus antongilii" (On-line). The IUCN Red List of Threatened Species 2008. Accessed March 02, 2016 at http://www.iucnredlist.org/details/6937/0.

Segev, O., F. Andreone, R. Pala, G. Tessa, M. Vences. 2012. Reproductive phenology of the tomato frog, Dyscophus antongili, in an urban pond of Madagascar’s east coast. Acta Herpetologica, 7(2): 331-340.

Tessa, G., F. Guarino, C. Giacoma, F. Mattioli, F. Andreone. 2007. Longevity and body size in three populations of Dyscophus antongilii (Microhylidae, Dyscophinae), the tomato frog from north-eastern Madagascar. Acta Herpetologica, 2(2): 139-146.

Wisnieski, A., V. Poole, E. Anderson. 1997. Conservation Spotlight: Tomato Frogs. Endangered Species Update, 14: 9 & 10: 17. Accessed January 31, 2017 at http://www.umich.edu/~esupdate/library/97.09-10/wisnieski.html.

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