Parsley Frogs (Pelodytidae)

views updated

Parsley frogs

(Pelodytidae)

Class Amphibia

Order Anura

Family Pelodytidae

Thumbnail description
Moderately small, primarily nocturnal, terrestrial Eurasian frogs

Size
1.8–2.2 in (45–55 mm)

Number of genera, species
1 genus; 3 species

Habitat
Moist areas from low elevations to midmountain regions

Conservation status
Data Deficient: 1 species

Distribution
Iberian Peninsula and southwestern Europe; Caucasus Mountains in Asia

Evolution and systematics

Fossil Pelodytidae (genus Miopelodytes) are known from the Middle Miocene of Nevada in the United States, and the Eocene of Germany (genus Propelodytes).

The designation Pelodytidae most commonly includes the fossil forms, and is characterized by the fusion of the "ankle bones" (astragalus and calcaneum). Fossils of Miopelodytes and the extinct Propelodytes arevacus have a fused astragalus and calcaneum, but other Propelodytes do not. Therefore, the status of Propelodytes as a pelodytid is questionable. No subfamilies are recognized.

Physical characteristics

Parsley frogs (named for their speckled green coloration), are small and gracile, with large, bulging eyes. They are distinguished from all other frogs by a unique set of morphological features that includes the presence of a parahyoid bone, fused Vertebrae I and II, fused astragalus and calcaneum, and three tarsalia bones in the foot. The average body size is 1.57–1.97 in (40–50 mm).

Distribution

The three species have a discontinuous distribution in Europe and western Asia. One species is in the northwestern Caucasus and western Trans-Caucasus, Russia, Georgia, and Turkey. The second is in southern Portugal and southern Spain, and the third is in Belgium, through France to eastern Spain and northwestern Italy.

Habitat

Parsley frogs are regularly found in deciduous and coniferous forested canyons, valleys drained by streams, and coastal zones. They can be found in or near shallow ponds, streams, and flooded quarries. One species seems prefer small streams with stony areas and/or sandy bottoms. Larval pelodytids are regularly found in brackish waters. These frogs can be found as far as 900 ft (275 m) away from the nearest water source.

Behavior

Pelodytids are generally nocturnal. During the day, they retreat to refugia under rocks or hide among vegetation at the base of large rocks or stone walls. At night, they forage near water sources. Parsley frogs hibernate from September to March, depending on the altitude and weather conditions.

Feeding ecology and diet

Parsley frogs generally forage at night. Their diet consists primarily of invertebrates, including flies, crickets, slugs, and worms.

Reproductive biology

Breeding in these frogs occurs during the spring and summer, with a second breeding season possible in the fall. Mating and egg laying seems to be triggered by rainfall. During the breeding season, males emit a low-volume acoustic signal, and apparently may call from under water. Amplexus (mating) is inguinal. Although the species are generally terrestrial, they breed in slow-moving to still waters, with eggs and tadpoles normally found in waters with high oxygen content and low plant nutrients. In France, several populations of pelodytid tadpoles have been found inhabiting brackish waters. The tadpoles have denticles, a sinistral spiracle, and well-defined jaw sheaths. Tadpole development can be prolonged, with some tadpoles regularly overwintering and completing their development the following year. Generally, tadpoles are medium-sized, but if they take two years to develop, can be quite large.

Conservation status

Although not listed (with one exception) by the IUCN or CITES, most populations are declining because of habitat destruction. Pelodytes caucasicus is categorized as Data Deficient by the IUCN; it is also listed in the Red Data Books of Russia, Georgia, and Azerbaijan and in the Bern Convention (Annex 2). Pelodytes punctatus is listed as endangered by the national standards of Belgium, Luxembourg, France, and as vulnerable in the other countries where it is found.

Significance to humans

None known.

Species accounts

List of Species

Parsley frog

Pelodytes punctatus

taxonomy

Rana punctata Daudin, 1803, Beauvoise, Oise, France. No sub-species are recognized.

other common names

English: Common parsley frog; French: Pélodyte ponctué; German: Westlicher Schlammtaucher; Spanish: Sapo moteado.

physical characteristics

This species is small, averaging only about 1.6 in (4 cm). It is brown in color, with green flecks on the dorsum. The common name seems to have originated because its coloring makes it appear to be coated with parsley. The parsley frog is similar to other species of pelodytids, but differs by several morphological and morphometric characteristics. P. punctatus is a smaller frog, with shorter hind legs. Also, the teeth found on the vomer bone (hard palate) are very close to the internal opening of the nares (the small hole connecting the nostrils and the inside of the mouth); this is not the case in other pelodytids.

distribution

P. punctatus is found in several countries in Europe. Its distribution includes Belgium, France, Luxembourg, eastern Spain, and northwestern Italy. Small populations occur in northern Spain.

habitat

This species generally inhabits open areas, including agricultural lands, as well as coniferous and deciduous forests. Although a terrestrial species, it can be found near slow, to still waters, such as deep ponds, small pools, flooded quarries, and slow-moving streams. It seems to prefer waters with stony or sandy areas. During the mating season, parsley frogs enter water to breed.

behavior

A primarily terrestrial, nocturnal species, these frogs generally hide under stones or in holes in the ground. They emerge only at night, after moderate rainfalls. Parsley frogs migrate to water during breeding season, and both males and females are good swimmers. Depending on the weather, climate, and altitude, the frogs may hibernate during the winter months (November to March).

feeding ecology and diet

These frogs actively forage at night, searching for small invertebrates, including crickets and flies.

reproductive biology

Depending on the climate, the breeding season begins in early spring (late February to April) and may occur again in fall (November to December). Reproduction seems to be triggered by rainfall. Males emit a low volume call from below the surface of the water. Amplexus (mating) is inguinal. Females lay an average of 50–300 eggs. During extended reproductive seasons, females may produce up to 1,600 eggs. The eggs are laid in small strings attached to aquatic plants. Tadpoles develop for approximately seven to eight months, and before metamorphosis, grow to be nearly 2.5 in (6.5 cm) long, which is larger than the adult frog. Metamorphosis occurs in January or February.

conservation status

Although not categorized by the IUCN, this species is listed as endangered by the national standards of Belgium, Luxembourg, France, and as vulnerable in the other countries where it is found. The most likely cause for its declines is the alteration and loss of its habitat through drainage of marshlands, canalization of rivers, and destruction of stream habitats. Its range is subsequently highly fragmented, and most populations are in steady decline.

significance to humans

None known.

Resources

Books

Duellman, William E., and Linda Trueb. Biology of Amphibians. Baltimore: Johns Hopkins University Press, 1994.

Garcia Paris, Mario. Los Anfibios de España. Madrid: Ministerio de Agricultura, Pesca y Alimentacion, 1985.

Gasc, Jean-Pierre, et al., eds. Atlas of Amphibians and Reptiles in Europe. Paris: Societas Europaea Herpetologica and Muséum National d'Histoire Naturelle, 1997.

Herrmann, Hans-Joachim. Terrarien Atlas Band 1. Melle, Germany: Mergus Verlag GmbH, 2001.

Zug, George R., Laurie J. Vitt, and Janalee P. Caldwell. Herpetology. 2nd edition. San Diego: Academic Press, 2001.