Carvalho's Surinam Toad
© 2010 Mauro Teixeira Jr (1 of 8)
Pipa carvalhoi is a moderate to large-sized species of Pipa, with females reaching 41-68 mm and males measuring 32-57 mm in SVL (Trueb and Cannatella 1986). The head is wide and triangular, but not depressed. The snout is broad and pointed, though rounded at the tip, and bears prominent and elliptical nares. Eyes are large and positioned dorsolaterally, with a diameter one-third of the interorbital distance (Trueb and Cannatella 1986; MCZ specimens). This species possesses the most pronounced and numerous teeth of all pipids, present on premaxillae and maxillae, with Trueb and Cannatella (1986) describing the teeth as fanglike.
The body of P. carvalhoi is long, robust and does not display the same dorsoventral compression present in other pipids (Trueb and Cannatella 1986). It is most similar in form to P. parva and unlike the other five Pipa species. The skin of P. carvalhoi is covered with conical tubercles, or small protuberances. The size and density of the tubercles vary greatly in different regions of the body. Dorsal surfaces display the most extreme tubercles, particularly the posterior portion of the back. Moving from posterior to anterior, the size and density of tubercles diminish. The shoulders have few, poorly defined tubercles and on the snout they are scarce and very small. The ventral portion of the body also has tubercles but they are less prominent and generally uniform in size (they do not intensify at the posterior). The limbs exhibit the same dorsal-ventral pattern as the rest of the body. Although young adults show the same patterns, the intensity of the posterior definition of the tubercles seems to increase with size (MCZ specimens).
The lateral line organs are numerous. Eight to ten lateral line organs appear on the dorsolateral surface of the snout, between the nostril and the eye. Another six organs spread out from the anterior and anterodorsal margin of the eye. Additionally, there is a double row of organs that parallels the mandible, ending in a proliferation of organs at the angle of the jaw, and still another set extending from the posterodorsal margin of the eye to the mandible. Dorsally, two series of lateral line organs run from the head to about mid-back. Two more series begin just before the forearm. Longitudinally oriented organs run along the flank and end at the groin. A ventrolateral series of vertically oriented organs extends along the flank and then posterodorsally to the vent. Yet another series is irregularly oriented and extends ventrolaterally from the axillary region along the flank posteromedially to the vent. Ventrally, there are scattered patches of organs in the pectoral region (Trueb and Cannatella 1986).
The fingertips are specially modified. While all pipids have lobes on the end of each fingertip, the exact arrangement and position varies with the species. Pipa carvalhoi has quadripartite lobes, which are symmetrical and terminally located. This formation is shared with P. aspera, P. arrabali, and P. snethlageae. The toes of P. carvalhoi are also noteworthy as toes I-III have keratinous caps (Caramaschi 1989). While this feature is rare among amphibians generally, all other Pipa except P. pipa and P. snethlageae share this trait. Another feature of the toes used to distinguish among species is the type/presence of an inner metatarsal tubercle. In P. carvalhoi, the tubercle is present but indistinct and poorly developed (Trueb and Cannatella 1986).
In preserved specimens, the dorsal coloration of the head, back and limbs is dark brown to reddish brown, with occasional dark brown spots. The dorsal surface of the limbs has the lightest ground color and the most distinct marking. Tubercles show no deviation in color. Ventrally, the dark brown fades into a light gray/tan, with some individuals having small spots. While the feet display the same coloration, the webbing between the fingers and toes is transparent (Trueb and Cannatella 1986; Caramaschi 1989; MCZ specimens).
As is characteristic of all pipids, P. carvalhoi has a labial modification consisting of a small dermal pocket at the angle of the jaw, extending over the mandible. While this labial modification is clearly visible in P. carvalhoi, it is not as extreme as that of P. pipa or P. snethlageae. The prearticular region of P. carvalhoi’s mandible is slightly rounded, but not as extreme as the medially directed curvature found in P. pipa or P. snethlageae. In the upper jaw, the pars palatina of the maxilla extends into a palatine process. This process articulates with that of the premaxilla, ultimately modifying and strengthening the palatal shelf of the upper jaw. This is a characteristic shared with five of the seven species of pipids. The pelvic girdle of pipids is distinctive as a genus, with only slight modification among species. While some, such as P. parva have dorsolaterally oriented iliac crests, those of P. carvalhoi are lateral. As in all pipids, Pipa carvalhoi has a modified arciferal pectoral girdle, and imbricate, opisthocoelous vertebrae. The sacrum and urostyle are fused, and the sacral diapophyses are elongated in the anterior-posterior direction. The ventral-anterior margin of the presacral I (atlas) is straight to slightly concave in P. carvalhoi (Trueb and Cannatella 1986).
Tadpoles are dark gray-brown dorsally, and transparent ventrally (Sokol 1977).
Distribution and Habitat
Life History, Abundance, Activity, and Special Behaviors
Pipa carvalhoi exhibits territorial behavior. Males have been observed defending underwater calling sites; however, their attachment to the same location is unknown. To defend their territory, males use visual displays, and may chase intruders, jump attack, and wrestle. While the behavior of many Pipa is difficult to observe, this territoriality and defense has also been described in P. pipa and P. parva (Duellman and Trueb 1994).
Pipa carvalhoi's reproductive behavior closely resembles that of other pipids and is nearly identical to that of P. pipa and P. parva, including somersaulting and female dorsal skin brooding. Adult P. carvalhoi are sexually mature at 7 to 9 months. Amplexus is inguinal (the male grabs the female around the waist above the thighs) and occurs while the mating pair is completely submerged in water. The pair, led by the female, begins a series of maneuvers where they swim toward (not reaching) the surface, the female releases eggs mid way, and then during mid-water turnovers, the male fertilizes the eggs and pushes them into the female’s dorsum with his vent region. The cycle is repeated until all the eggs are released, fertilized, and implanted (Duellman and Trueb 1994).
After the eggs have been fertilized, they are implanted in the skin of the female’s dorsum. The epidermis and dermis of the female’s back during this time undergo significant change: the egg chambers are highly vascularized and adhere to the single jelly capsule of the egg. The small gills of the developing embryos then engage in gas exchange with the vascularized tissue of the mother. In P. carvalhoi, along with P. parva and P. myersi but unlike other Pipa, the free-living larval stage is still present (Sokol 1977). After 14 to 28 days of dermal brooding, the eggs hatch from the mother’s skin as the tadpoles push their way through the small aperture of the egg chamber. Other pipids such as P. pipa undergo direct development, hatching miniature adult frogs instead of larvae. Because of the increased demands of direct developing young, pipid species with direct development usually have only one annual reproduction cycle. However, species such as P. carvalhoi that produce tadpoles are able to reproduce several times a year. Captive individuals have been recorded to produce clutches 4 to 8 weeks apart (Duellman and Trueb 1994).
Tadpoles of P. carvalhoi are between 50 and 60 mm in length at stage 60 (the beginning of cranial metamorphosis). The forelimbs are freed 14 to 21 days prior to cranial metamorphosis, which itself begins at about 60-80 days post-hatching. The mouth structure is about half the head width and is terminal. Notably, P. carvalhoi lacks the opercular flap extending across branchial slit II. Thus, internal gills are absent and forelimb development is external and visible, occurring in front of the branchial baskets. The skull and jaws are largely composed of embryonic cartilage and are long, broad and flat (Sokol 1977).
Both the tail and the lungs are important in hydrostatic stabilization. Tadpoles must fill their lungs before they can swim; with improperly filled lungs, P. carvalhoi larvae will struggle to get to the surface and move (Sokol 1977).
To feed, these tadpoles employ hyobranchial pumping to gather particles in the water; they are filter feeders. When food is lacking, the larvae attempt to stir the substrate. Adult feeding begins when the tail is reduced to one-half to one-third its original size (Sokol 1977).
Trends and Threats
Possible reasons for amphibian decline
General habitat alteration and loss
Pipa carvalhoi was originally described by Miranda-Ribeiro (1937a, 1937b). Later that year, Carvalho (1937) described its larval form. Caramaschi (1989) clarified the designation of the lectotype, since Miranda-Ribeiro (1937) did not specify the holotype and paratypes.
The specimens used for observation are located at the Harvard Museum of Comparative Zoology. The catalog numbers and localities are as follows: Brazil A-25737, A-85560, A-85561, A-85562, A-85563, A-88279; Ecuador A-97277, A-97278, A-97279.
Cannatella, D., and de Sá, R. O. (1993). ''Xenopus laevis as a model organism.'' Systematic Biology, 42, 476-507.
Caramaschi, U. (1989). ''Notes on the type specimens of Pipa carvalhoi (Miranda-Ribeiro, 1937) (Anura, Pipidae).'' Journal of Herpetology, 23, 192-193.
Carvalho, A. L. de (1937). ''Notas oecologicas e zoogeographicas sobre vertebrados do nordeste brasileiro.'' O Campo (Mar.), 1937, 12-15.
Duellman, W. E., and Trueb., L. (1994). Biology of Amphibians. Johns Hopkins University Press, Maryland.
IUCN, Conservation International, and NatureServe. 2006. Global Amphibian Assessment: Pipa carvalhoi. www.globalamphibians.org. Accessed on 10 May 2008.
Miranda-Ribeiro, A. de (1937). ''Ainda os batrachios do nordeste.'' O Campo (Mar.), 1937, 26.
Miranda-Ribeiro, A. de (1937). ''Sobre una collecção de vertebrados do nordeste brasileiro. Primeira parte: peixes e batrachios.'' O Campo (Jan.), 1937, 54-56.
Rabb, G. B., and Rabb, M. S. (1963). ''Additional observations on breeding behavior of the Surinam Toad, Pipa pipa.'' Copeia, 1963(4), 636-642.
Sokol, O. M. (1977). ''The free swimming Pipa larvae, with a review of pipid larvae and pipid phylogeny (Anura: Pipidae).'' Journal of Morphology, 154(3), 357-425.
Trueb, L., and Cannatella, D. C. (1986). ''Systematics, morphology, and phylogeny of genus Pipa (Anura: Pipidae).'' Herpetologica, 42, 412-449.
Written by John Abraham (jabraham AT fas.harvard.edu), Harvard
First submitted 2008-05-13
Edited by Kellie Whittaker (2008-08-09)
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