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Spikethumb frogs are a genus ( Plectrohyla) of in the family Hylidae found in Central America from southern Mexico through Guatemala and northern El Salvador to central and northern Honduras. A major revision of the Hylidae moved an additional 21 species to this genus from the genus Hyla., 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, Num. 294, pp.1-240. [1] The additional species moved to Plectrohyla were identified as the Hyla bistincta group, also called the Plectrohyla bistincta group; a separate group from the initial Plectrohyla guatemalensis group. This Phylogenetics classification was later revised by moving the Plectrohyla bistincta group from the genus Plectrohyla into a new genus called Sarcohyla. Meanwhile, the guatemalensis group remained in Plectrohyla. They are called spikethumb because of the spike on their thumbs, which is called a prepollex. The genus name comes from the Greek language word plēktron ("spur") and hyla (the genus in which it was formerly placed).
| Thorny spikethumb frog |
| Greater spikethumb frog |
| Honduras spikethumb frog |
| Forest spikethumb frog |
| Guatemala spikethumb frog |
| Hartweg's spikethumb frog |
| Hazel's tree frog |
| Ixil spikethumb frog |
| Pop-eyed spikethumb frog |
| Matuda's spikethumb frog |
| Rio Sananja spikethumb frog |
| Thick-lipped spikethumb frog |
| Las Palmas spikethumb frog |
| Arcane spikethumb frog |
| Cave spikethumb frog |
| Alta Verapaz spikethumb frog |
Research suggests that males engage in male-male combat to maintain control of their mating sites, located within the crevices between rocks, as mating sites are likely a limiting resource. The prepollex may be used during this combat, leaving scars on the head and forelimbs of males. These scars are not observed on females.
In Plectrohyla, the specialized mucous glands in the lips of males produce sodefrin precursor-like factors (SPF), which function as allohormones. Allohormones are substances that are directly transmitted from one individual to another, circumventing the special senses, and can have various effects on copulation, including increased female receptivity, inhibition of remating, and altered sperm storage in females. Male spikethumb frogs deliver allohormones via tramautic mating, in which the male presses its swollen upper lip and protruding premaxillary and maxillary teeth into the back of the female, leaving scratches on the female's back. These scratches allow for direct transmission of the SPF allohormone into the bloodstream of the female, preventing loss to the environment. These differ from , which are released into the environment and detected via the special senses. Upon transmission into the bloodstream, SPF allohormones function by shortening courtship duration, however the exact effect of SPF allohormones on the physiological and behavioral changes to the female have not been determined. Shortened courtship duration reduces risks of predation during copulation, increasing fitness.
This copulatory mechanism resembles the condition of the plethodontid salamander, in which males use their elongated teeth to scratch the backs of females to deliver allohormones directly from the mental glands on their chin. These allohormones increase female receptivity, which results in increased probability that the female will accept the male's sperm.
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