Family Heleophrynidae

Heleophryne Sclater, 1898

ghost frogs, spookpaddas (A)

By R.C. Boycott

Currently accepted name: Heleophryne indet.
Red listing status:

Description

The name Heleophryne is derived from the Greek: hélos = marsh; phrynes = toad. This is an inappropriate appellation because these frogs do not frequent marshes, nor are they toads (Du Preez 1996).

The adults and tadpoles have developed remarkable adaptations to survive in their habitat. The head and body of the adults are flattened, allowing the frogs to enter narrow cracks and crevices between or under rocks. The limbs are long, the toes extensively webbed, and the digits on the hands and feet are broad and flattened (spatulate) at their tips, thereby increasing the surface area in contact with wet, slippery substrate. The pupils are vertically elliptical and a glandular skin fold is present behind the eye, above the tympanum. The pattern and colour of the dorsum is cryptic and varies greatly from a dark, mottled pattern with indistinct blotches to a pattern of clearly defined, often white-edged, dark patches on a lighter background. Males develop a variety of secondary sexual characters during the breeding season, including asperities on various parts of the body (see below). The tadpoles are streamlined and possess a large, sucker-like oral disc which enables them to remain attached to the substrate in swift-flowing water, and to climb wet, vertical rock surfaces (Rose 1926; Boycott 1972; Boycott and De Villiers 1986).

Distribution

The family Heleophrynidae comprises a single genus, Heleophryne, that is endemic to South Africa, Swaziland and Lesotho (Boycott 1999). Because its closest relatives are found in Australia and South America, the family may be considered to be a Gondwanaland relic. The genus occurs in high-rainfall, mountainous regions of South Africa, Swaziland and Lesotho. The elevation of H. purcelli orientalis to a full species by Visser (1990), a decision supported by Channing (2001) and the present author, brings the number of species in this genus to six. Five species are restricted to Western and Eastern Cape provinces, while H. natalensis extends into KwaZulu-Natal, Lesotho, Swaziland, Mpumalanga and Limpopo Province. It has been suggested that additional cryptic species await discovery (Boycott 1988a; Channing 2001).

The taxonomic status of populations from the Kammanassie, Kouga and Baviaanskloof mountains remains unclear (Boycott and Branch 1988; Branch and Bauer 1995). These localities were plotted on the genus map but not on the species maps.

Habitat

The genus inhabits the Fynbos, Forest and Grassland biomes at altitudes of 60–2675 m. Adults and tadpoles are usually associated with perennial, slow- and swift-flowing mountain streams with cool, clear water and rocky substrates.

Life history

Very little is known of the non-breeding behaviour of these species, except that adults may move considerable distances from their breeding habitats during the non-breeding period. All species for which data are available, appear to breed when river and stream flows are reduced (Boycott 1982, 1988a, 1999). At this time, adults may be found beneath submerged and partly submerged rocks, on rocks near waterfalls and cascades, on moss-covered rock faces, in rock cracks, and in caves.

Males call from sites near waterfalls and cascades and from under rocks. With one exception, the calls of the various species are quite similar, consisting of a series of high-pitched ringing notes, not unlike the sound produced by the Anvil Bat (Boycott 1982). The call is high pitched so that it is audible to females above the background noise of rushing water (Boycott 1982; Passmore 1985). Males also call under the water, usually beneath a submerged or partly submerged rock. Calling males in peak breeding condition will call during the day and at night.

Prior to the breeding period, reproductively mature individuals develop secondary sexual characteristics. These include the development of asperities on the forefingers, forearms, head, body and around the cloaca. Dorsal skin folds develop and nuptial pads develop on the forefingers or forearms. The distribution and concentration of asperities and nuptial pads varies between species and can be used to identify the taxa (Boycott 1982).

Amplexus is probably inguinal, having been observed once in captivity when a male was seen to clasp a female around the groin (Boycott 1988b). Although oviposition has not been witnessed, a pair with a partially laid clutch of eggs was uncovered when a large rock lying across a shallow stream was lifted (pers. obs.). The eggs are large and yellow with a stiff jelly capsule. Between 100 and 200 eggs per clutch are laid (exceptionally as few as 50 or as many as 208), usually under submerged or partly submerged rocks in streams (Visser 1971; Boycott 1988a), but also in quiet shady pools (Boycott 1972) and, in one species, on wet gravel under rocks (Visser 1990).

After four or five days the eggs hatch and the young tadpoles subsist on a large reserve of yolk. The tadpoles feed on algae growing on the surface of rocks and substrate bedrock, which they scrape off using their many rows of teeth. In larger, quieter pools, feeding trails on the surface of rocks may be evident, indicating the presence of a Heleophryne population (Boycott 1999). Larval life covers at least two breeding seasons, hence the species are dependent on perennial streams to sustain populations (Boycott 1988a; Passmore and Carruthers 1995).

Conservation

Of the six species recognized in this publication, two species, H. hewitti and H. rosei, are listed as Critically Endangered. While the maps reflect the general area of occurrence of the two species, the actual area of occupancy of both is highly restricted. The principal threats to these, and other species in the genus, are loss and degradation of habitat resulting from afforestation, fire, erosion, damming of rivers, and the introduction of alien fish species. The ghost frogs’ dependence on perennial streams (see paragraph on tadpoles above) is an important life history feature to be taken into account in all conservation plans.