Matuda’s Spikethumb Frog
© 2019 Maria Delia Basanta (1 of 19)
The species’ arms are relatively short and robust, and in some breeding males, the arms show signs of swelling. A row of longitudinal tubercles is present on the ventrolateral edge of the forearm. There is a transverse dermal fold on the wrist. The palmar tubercle is elevated and bifid. The prepollex is moderately enlarged and is curved at the end. In some male specimens a sharp prepollical spine also protrudes from the prepollex. The long and slender fingers have moderately large discs with the disc diameter of the third finger being larger than the diameter of the tympanum. The webbing on the hands is vestigial. The large subarticular tubercles are conical with the distal tubercle on the third and fourth fingers being bifid in some individuals. There are also large, subconical supernumerary tubercles present as a single or double row on the proximal segments of the fingers (Duellman 2001).
The legs are relatively short. When adpressed at right angles to the body, the limbs barely overlap. When adpressed along the body, the tibotarsal articulation reaches the eye. There is no transverse dermal fold on the heel but there is an elevated tarsal fold that extends the length of the tarsus. There are a few small tubercles on the heel and an oval, subconical inner metatarsal tubercle. There is no outer metatarsal tubercle. The long and slender toes have discs that are smaller than those on its fingers. The toes are roughly three-fourths webbed, with the webbing extending from the base of the penultimate phalanxes of each toe. The small subarticular tubercles are conical while the supernumerary tubercles are large and subconical. The supernumerary tubercles are presented in a single row along each toe until the proximal segment at which point they are arranged irregularly (Duellman 2001).
The dorsal skin is tuberculate with tubercles also present on the flanks. The skin on the throat, belly, and ventral surfaces is coarse and granular while the skin on other ventral surfaces is smoother. The anal opening is directed posteroventrally, halfway up its thighs, and its anal sheath is bordered on both sides by a large tubercle (Duellman 2001).
Tadpoles examined at stage 25 had body lengths of 10.5 to 13.1 mm, and total lengths of 29.5 to 38.2 mm. Typical tadpoles in developmental stage 28 have a body length of 13.7 mm and a total length of 40.5 mm. Plectrohyla matudai tadpoles have an ovoid body that is slightly wider than it is deep. From the dorsal view, the snout is bluntly rounded, while in the lateral view the snout is truncated. The nostrils situated midway between the eyes and the tip of the snout. The eyes are small and are directed dorsolaterally. The mouth is ventral and is of a moderately large size, roughly two-thirds of the tadpoles’ body length. The mouth is bordered entirely by a single row of short papillae. However, medial to this row of papillae sits an irregular row of larger papillae. The upper part of the beak is broad and barely arched, with long and pointed serrations present. One serration on each side is enlarged into a fang-like projection. The lower part of the beak is narrow, forming a broad and curved arch. The lower beak also bears small, pointed serrations. Two upper and three lower rows of teeth are present. The upper rows are long and equal in length, though the second upper row is interrupted medially. The first and second lower rows are equal in length to each other, though noticeably shorter than the upper rows, and the third lower row is shorter than the first and second rows. The sinistral spiracle has an opening roughly midway on the body’s length at the midline. The cloacal tube is long and positioned dextrally. The tail has heavy caudal musculature that extends to the rounded tip and shallow caudal fins. The tail’s dorsal fin is deeper than that of the ventral fin and neither extends onto the body. The dorsal fin is deepest at the mid-length of the tail, but at that point the caudal musculature is still much deeper (Duellman 2001).
Plectrohyla matudai, like P. quecchi, P. sagorum, and P. ixil (three similarly sized species within genus Plectrohyla) has a pointed prepollical spine. However, P. matudai has a vertical rostral keel that distinguishes the focal species from P. quecchi and P. sagorum. More tuberculated skin differentiates it from P. ixil and P. sagorum. Additionally, P. ixil has a pale lateral stripe and acuminate snout, which P. matudai does not. Other members of Plectrohyla are larger and lack vocal slits, allowing them to be easily differentiated from P. matudai (Duellman and Campbell 1992, Duellman 2001).
Plectrohyla matudai tadpoles can be differentiated from other of their genus by their mouthparts. The focal species is most easily differentiated from P. guatemalensis by the former having one row of fringed papillae instead of two, very few lateral papillae, shorter upper tooth rows, a third lower tooth row that is much shorter than the others, and fang-like serrations on the upper beak. Fewer lateral papillae and fang-like upper beak serrations also differentiate the focal species from P. ixil and P. sagorum. More lateral papillae and fang-like serrations on the upper beak differentiate the focal species from P. quecchi and P. glandulosa (Duellman 2001).
In life, Plectrohyla matudai has a tan to pale brown dorsum covered with darker brown, olive brown, or black reticulations or flecks. In some specimens, metallic green flecks can be found on dorsal surfaces. There is typically a dark, narrow stripe on the upper lip and below the eye. The area below the shoulder is typically a plain or bluish gray with a thin outline of black. Narrow, dark bars or flecks are present on the limb’s dorsal surfaces. The thighs are typically a creamy tan color anteriorly, while the posterior surfaces of the thigh are pale brown. A dark, irregular stripe extends from the supratympanic fold nearly to P. matudai’s groin, separating the dorsal coloration from the cream color on the frogs’ flanks. This stripe is sometimes fragmented, resulting in a series of dashes or flecks, or is absent entirely. The venter is creamy white and the vocal sac a grayish brown. The iris is coppery-tan with fine black reticulations. In preservative, dorsum becomes a dull brown with darker brown or black markings. On the thighs, the anterior and posterior surfaces become pale tan or brown. The ventrum becomes creamy tan or pale grayish brown (Duellman 2001).
In life, tadpoles of Plectrohyla matudai have a brown body with tan caudal musculature that is speckled with reddish-brown flecks. These flecks are often present on caudal fins as well. The tadpoles’ irises are a dull bronze in color. In preservative, the body becomes a dull or grayish brown with tan, pinkish caudal musculature covered in brown flecks (Duellman 2001).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Guatemala, Honduras, Mexico
Life History, Abundance, Activity, and Special Behaviors
Plectrohyla matudai’s call is described as a sharp, single note that resembles “two pebbles struck together underwater,” repeated at intervals of about two minutes. Calling males are typically seen sitting on vegetation, though there are reports of them calling from the water as well (Taylor and Smith 1945, Duellman 2001).
Of four females examined in 1992, there was a range of 101 - 144 ovarian eggs, with the diameter of the eggs ranging between 1.9 and 2.5 mm (Duellman and Campbell 1992).
Tadpoles develop in cascading streams, where they typically adhere to boulders in areas of the stream that are less turbulent (Duellman 2001).
Plectrohyla matudai often coincides sympatrically with P. sagorum and P. guatemalensis as the three species have largely overlapping distributions. However, P. guatemalensis typically inhabits larger mountain streams unlike P. sagorum and P. matudai (Duellman 2001).
Trends and Threats
Possible reasons for amphibian decline
General habitat alteration and loss
Analysis of mitochondrial and nuclear DNA sequences indicate that P. matudai is part of the Plectrohyla guatemalensis group, rather than the Hyla bistincta group (Faivovich et al. 2005).
Three morphological characteristics of P matudai and P. ixil were considered similar enough to group them as sister species: the lack of articulation between their squamosal and crista parotica, the presence of linea masculinea (bands of fibrous connective tissue), and the presence of enlarged, fanglike serrations on their upper jaw sheath as tadpoles (Duellman and Campbell 1992).
Molecular phylogenies suggest that the genus Sarcohyla and Plectrohyla are sister genera. Trees estimated with the nuclear genes Rag-1 and POMc support the monophyly of the Sarcohyla and Plectrohyla clades, however, only Plectrohyla's monophyly was supported by trees constructed using analysis of the 12s and ND1 mitochondrial genes (Caviedes-Solis and de Oca 2018).
The genus, “Plectrohyla” is derived from the Greek, “plectron” meaning “spur”, referring to their prepollical spine and “Hylas” of Greek mythology (Duellman et al. 2016).
The species epithet, "matudai”, is named in honor of Eizi Matuda, a botanist from Chiapas, Mexico who helped arrange Norman Hartweg’s expedition to Chiapas (Hartweg 1941, Duellman 2001).
Caviedes-Solis, I.W., de Oca, A.N.-M. (2018). ''A multilocus phylogeny of the genus Sarcohyla (Anura: Hylidae), and an investigation of species boundaries using statistical species delimitation.'' Molecular Phylogenetics and Evolution, 118, 184-193.
Duellman, W. E. (2001). The Hylid Frogs of Middle America. Society for the Study of Amphibians and Reptiles, Ithaca, New York.
Duellman, W. E., Campbell, J.A. (1992). ''Hylid frogs of the genus Plectrohyla: systematics and phylogenetic relationships.'' Miscellaneous Publications, Museum of Zoology, University of Michigan, 181, 1-32.
Duellman, W. E., Marion, A. B., Hedges, S. B. (2016). ''Phylogenetics, classification, and biogeography of the treefrogs (Amphibia: Anura: Arboranae).'' Zootaxa , 4104, 1 - 109.
Faivovich, J., Haddad, C. F. B., Garcia, P. C. A., Frost, D. R., Campbell, J. A., Wheeler, W. C. (2005). ''Systematic review of the frog family Hylidae, with special reference to Hylinae: phylogenetic analysis and taxonomic revision.'' Bulletin of the American Museum of Natural History, (294), 1-240. [link]
Hartweg, N. (1941). ''Notes on the genus Plectrohyla, with descriptions of new species.'' Occas. Papers Mus. Zool. Univ. Michigan, 437, 1-10.
IUCN SSC Amphibian Specialist Group 2016. ''Plectrohyla matudai.'' The IUCN Red List of Threatened Species 2016: e.T55880A53960697. http://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T55880A53960697.en. Downloaded on 2 June 2019.
Taylor, E.H. and Smith, H.M. (1945). ''Summary of the collections of amphibians made in Mexico under the Walter Rathbone Bacon Traveling Scholarship.'' Proceedings of the U.S. National Museum, 95, 521-613.
Written by Connor Sullivan (sulcon21 AT uw.edu), University of Washington
First submitted 2019-08-01
Edited by Ann T. Chang (2019-08-01)
Species Account Citation: AmphibiaWeb 2019 Plectrohyla matudai: Matuda’s Spikethumb Frog <http://amphibiaweb.org/species/1044> University of California, Berkeley, CA, USA. Accessed Oct 24, 2020.
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Citation: AmphibiaWeb. 2020. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 24 Oct 2020.
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