Family Pyxicephalidae

Arthroleptella Hewitt, 1926

moss frogs, chirping frogs, mospaddatjies (A)

By A. Channing

Currently accepted name: Arthroleptella indet. Hewitt, 1926
Red listing status:

Description

The name derives from arthron = joint; lepto = slender; the diminutive ella is used as these are very small frogs.

In appearance, Arthroleptella closely resembles Cacosternum, but is a terrestrial breeder with no free-swimming tadpole stage (Passmore and Carruthers 1995). The adults are small, with males being smaller than females. Males range in body length from 15–22 mm, while the largest recorded female (A. hewitti) measured 36 mm (Poynton 1964; Channing 2001). The pupil is horizontal, the tympanum small but generally distinct, and the digits lack webbing (Lambiris 1989a). The various species are morphologically similar, while colour and markings are extremely variable within species. The advertisement call and molecular characters provide the most reliable means of distinguishing the species (Channing et al. 1994b). The genus is currently under taxonomic investigation and at least two additional species are awaiting description. The common names refer to the cricket-like, chirping calls of most species and to their occurrence in mossy habitats.

Distribution

This is an endemic genus of seven species, confined to South Africa. It is found in localized populations associated with moist mountain slopes. Species are known from the Drakensberg and KwaZulu-Natal midlands in the north, and the Cape fold mountains, including the Cape Peninsula, in the Western Cape Province.

Habitat

Members of this genus are associated with mountainous terrain. In Western Cape Province they inhabit montane fynbos, sometimes entering forested kloofs that are also the preferred habitat of A. hewitti in KwaZulu-Natal. A. ngongoniensis inhabits grassland in the mist-belt of KwaZulu-Natal. Populations are associated with seepage areas, often at high altitude but also at sea level in Western Cape Province. The frogs are usually associated with moss on rocks or beneath sedges or grass.

Life history

Much remains to be discovered about the life histories of most of these cryptic species. The frogs aestivate during the dry season but become active after the first rains. Breeding commences with the rainy season: in winter in the Western Cape, and in summer along the KwaZulu-Natal escarpment and the Drakensberg. Males call from concealed sites under vegetation, often in places where water is dripping. Most species call predominantly during daylight hours. Eggs are laid beneath moss, under thick vegetation, or at the bases of grass tussocks. The male continues to call near the oviposition site, and may attract a second female. Clutches contain 5–40 relatively large eggs, up to 4 mm in diameter, covered in a thick jelly capsule up to 10 mm in diameter. The eggs develop directly into small froglets within 7–27 days, without passing through a free-swimming tadpole stage. Prey consists of very small arthropods. Predators have not been recorded.

Conservation

Four of the seven species have localized distributions below the thresholds of the IUCN criteria for extent of occurrence and/or area of occupancy. Many of the watered slopes on which this genus is found, especially in KwaZulu-Natal, are threatened by invasive alien vegetation, plantations of exotic trees, building developments, alteration of drainage patterns and frequent fires (Harrison et al. 2001). Special attention should be given to the Critically Endangered A. ngongoniensis.