Nectophrynoides viviparus (Tornier, 1905)
Original Published Description:
Morogoro Tree Toad (English), Robust Forest Toad (English)
Nectophrynoides viviparus is easily distinguished from other species of the genus by its large size and enormous glands. This toad is found restrict to highland areas in the Eastern Arc Mountains and Southern Highlands of Tanzania and is considered Vulnerable. Fertilization is internal, and females give birth to live toadlets.
The tympanum is visible at least in adults, the tip of forth toe exceeds the tip of the snout, and the fifth toe is shorter than third. This species is viviparous.
This species occurs in the Nguru, Rubeho, Uluguru, Udzungwa Mountains and in the Southern Highlands of eastern and southern Tanzania.
The specific name is from the Latin 'vivus' meaning alive or living and 'parere' meaning bring forth or bear, referring to the fact that this species gives birth to live young.
A robust Nectophrynoides with very large distinct glands on the limbs. The skin is smooth and glandular. The dorsal coloration can be extremely variable, including gray, reddish, and green colors, but the color of the glands is usually in contrast with the rest of the body. The tympanum is visible and round, but may be difficult to see. Fingers are webbed only slightly at the base. Toes have some webbing (Harper et al., 2010).
Loader et al. (2009) notes that the material from Berlin comprises a range of embryos and adult specimens (SUL: 10.8-32.9). The addition of SHCP material includes adult specimens (SUL: 32.0-40.0). The larger size reported by Channing & Howell (2006) for N. viviparus is based on 166 specimens collected by A. Loveridge from the Ulugurus (e.g. males reach max SUL 56, and females c. 60; Barbour & Loveridge 1928; Channing & Howell 2006). It is unclear whether there are significant geographical differences in SUL between populations. This will require examination of specimens across all the assumed distribution range of the species (e.g. Ulugurus, Udzungwa and Rubeho; Channing & Howell 2006). They present morphometric data and SUL ratios for key measures for the specimens of N. viviparus from the Southern Highlands.
Snout is pointed. Canthus rostralis is distinct. Loreal region is slightly concave. Snout is slightly longer than the eye diameter. Nares is positioned below the canthus rostralis, directed a bit caudally. The interorbital space is as wide as the upper eyelid. Pupil is horizontal. Tympanum is present but not very distinct, small (about 1/3 of eye diameter), and coloured dark brown. Head is comparatively large, markedly separated from body. Fingers are considerably long, widely splayed from each other and in life certainly not laying together. First finger is much shorter than second; second only half the length of third finger. Fourth finger is shorter than third and slightly longer than the second. Skin below fingers is without prominent bulges but swollen. First toe is much shorter than second, second much shorter than third, third shorter than fourth, fifth shorter than fourth and third. Below toes and on soles of feet, the tubercles are only almost plain, roundish bulges, as are the outer and inner metatarsal tubercle. When hind legs pulled forward, hock extends beyond snout tip, and toes extending snout by far. Skin is smooth. Parietal glands are remarkably large but not very prominent. No fold of skin along the chest. As juveniles they are uniformly blackish brown, bur as they grow older, the color fades. First the belly gets branching clear yellow spots, which extend in size in a way that finally a white-yellowish venter is covered with numerous blackish brown points. Dorsum of back and legs fade as well to chocolate brown, and finally the dorsal surfaces are irregularly blackish brown and clear chocolate brown (Tournier, 1905).
Description of the lectotype (measures in mm). ZMB 21775, adult female. Dissected at lower mid ventral region. Embryos presumably removed and separately stored in small jar (18 embryos, 2.0-2.2 diameter= head and body including yolk; total length variable: 4.8-6.4). Distance from tip of snout to urostyle 32.9, width of head at jaw articulation 12.6, length of tibia 15.0, length of foot 14.4; tympanum and tympanic annulus easily discernible, ovoid shape 1.5 in diameter; parotoid glands present as a smooth glandular mass, 7.8 in length and 5.4 at widest point starting on the dorsal surface just behind the eye, directed posteriorly; snout relatively short, nostrils closer (2.2) to the snout tip than to each other (2.7) and also to the corner of the eyes (3.5); interorbital distance 6.7; eyes sunk and just about visible ventrally; eye diameter 3.2 right and left, width of eyelid, right 2.7 and left 2.3; interorbital distance 3.8 (difficult to measure as eyes are almost sunken into skull); canthus rostralis concave; arms and legs relatively slender; continuous glandular mass on both arms and legs; on arms, glands are continuous on dorsal, lateral and ventral surfaces of radius/ulna, not present on humerus; on legs, glands are continuous on dorsal, lateral and ventral surfaces of tibiofibulae and tarsal joints, not present on femur; continuous glandular mass on lateral and dorsal margin of the foot, attenuating to the margin of the phalange; rudimentary webbing on hands and feet; first finger shortest with second and fourth equal in size shorter than third finger which is the longest (6.4); first and second toe equal in size, third and fifth toes equal and larger, with fourth toe longest (10.5); small inner metatarsal tubercle, and large expanded outer metatarsal tubercle (1.8), shortest toe 3.0; the body skin is smooth both on glandular and non-glandular areas.
Barbour & Loveridge (1928) noted colour variation in Uluguru material of Nectophrynoides viviparus and hinted at a correlation with the habitats they were found – or “very slowly” changing their colouration to suit their habitat. Colour range from jet-black dorsal and ventral regions with glands marked rusty brown. Variations of this include dorsal regions coloured greenish, rufous-brown, bright yellow, in patches. The colour of the glands vary from rusty brown, to a lighter cream colour. In topotypic material colours from the original type series are all discoloured but Tornier (1905) provided some brief comments on their colour at the time of their descriptions and remarked that juveniles are uniform blackish brown. Dorsal parts of back and legs fade as well to a colour that is clear chocolate brown. Dorsal surfaces are irregularly blackish brown and clear chocolate brown. From a recent collection in the Southern Highlands Loader et al. (2009) noted colour variation. For dorsal and ventral surfaces we observed specimens jet black with cream light brown coloured glands. The chin region was often also lighter coloured being a cream light brown. Differences to this pattern included specimens with a mid dorsal reddish-brown colouration and ventral region reddish brown. Loader et al. (2009) also observed specimens with a light brown/yellow colouration completely covering dorsal and ventral aspects.
Habitat and Ecology
It is a terrestrial species living in forest, bamboo, and grasslands at the forest edge from 1,350-2,800 m asl. It has been found in maize cultivation, but needs to be close to the forest edge, and probably cannot tolerate complete opening up of its habitat (Loader et al., 2004).
Nectophrynoides viviparus has been collected in montane forest from approx. 1800 to 2700 m a.s.l in the Southern Highlands. This includes wet, open, secondary and disturbed montane forest, including logged Hagenia forest. In addition specimens have been collected in montane grassland and ericaceous heathland near the forest edge.
It is relatively common (Loader et al., 2004).
Populations of this species are believed to be decreasing (Loader et al., 2004).
Fertilization is internal. Females retain eggs and give birth to live toadlets (Harper et al., 2010). Tornier (1905) reported that an especially large female of the type series carried 67 larvae, 37 in the right oviduct and 30 in the left oviduct.
The lower parts of both oviducts are enlarged; internal walls smooth without diaphragms or protrusions where eggs or larvae could lie or adhere, at the lowest ends both oviducts fuse to one large cavity. In both oviducts a large number of mature frog-larvae lay loosely and independently from each other. In an especially large female the right oviduct had 37, the left oviduct 30, a total of 67 larvae. Accordingly a younger specimen carried less. The young have no “amnion” and apparently are far developed; i.e. they have the head and mouth shapes of adult animals, the eyes are large and fully developed, and the deep black iris distinctly contrasts from the only sparsely pigmented and hence still colourless individual. The vertebrae sit on the bulbously bloated body like a just closed medulla on a cleavage egg. The abdominal cavity is filled with a huge amount of unused yolk. The vertebrae end with a long, round tail. Both hind and front extremities are already visible as buds. The posterior buds seem to be a bit further developed. The vent is positioned between the hind legs and originates a bit further dorsally than them. The facts that these larvae do not have fins on the tail, that the extremities are well developed, the vent is positioned above the hind legs, and head and mouth already have the definite shape, makes it certain that this frog species is not only viviparous but gives birth to even young frogs that are fully metamorphosed.
Described by Channing and Howell (2006) as “A series of slow creaks…with 35 pulses at a rate of 52/s.”
IUCN Red List Category and Justification of Conservation Status
The IUCN Red List (2010) categorizes this species as Vulnerable because its Extent of Occurrence is probably less than 20,000 km2, its distribution is severely fragmented, and the quality and extent of its forest habitat in the Eastern Arc Mountains is declining (Loader et al., 2004).
The major threat to this species is habitat loss, especially at lower altitudes, due to agricultural encroachment, wood extraction and expanding human settlements (Loader et al., 2004).
Conservation Actions and Management
It occurs in several forest reserves, but has not been found in any well-protected area. It might occur in the Udzungwa National Park, but has thus far not been recorded (Loader et al., 2004).
- Pseudophryne vivipara Tornier, 1905 (synonym)
- Nectophryne werthi Nieden, 1911 "1911" (synonym)
- Tornierobates vivipara — Miranda-Ribeiro, 1926 (synonym)
- Nectophrynoides vivipara — Noble, 1926 (synonym)
- Nectophrynoides viviparus — Perret, 1971 (synonym)