Larval and metamorphic skeletal development in the fast-developing frog Pyxicephalus adspersus (Anura, Ranidae)

Abstract

The speed of larval development of the South African bullfrog, Pyxicephalus adspersus, is exceptional among living frogs. Embryonic development, larval phase, and metamorphosis can be completed in 17 days at a temperature of 29°C. The metamorphosis only takes 5 days. The present study shows that, despite the unusually short larval phase in P. adspersus, the state of skeletal differentiation reached at the end of metamorphosis is similar to that of other frog species. There is no shift of cranial bone formation postmetamorphosis as could have been expected and is known from other species. The majority of compared species are particularly similar in the sequence of bone formation in the postcranial skeleton. However, there are clear differences among species in the timing of these events relative to the larval growth trajectory, absolute time, and certain developmental markers, such as external limb differentiation. For example, skeletogenesis and externally visible limb differentiation are only loosely integrated. Interspecific comparisons show that, in P. adspersus, the early onset of skeletal ossification is an unusual feature among frogs. Freshly metamorphosed froglets of P. adspersus are already distinct from comparable stages of other species in having strong jaws, fang-like teeth, and a squamosal-maxilla contact. The latter stabilizes the maxillary arcade and the suspensorium and might relate to the ability to catch and swallow very large vigorous prey, such as siblings, shortly after metamorphosis. The presence of a complete set of dermatocranial elements and postmetamorphic ossification of only the sphenethmoid and operculum are considered plesiomorphic features, whereas the much less completely ossified skulls of metamorphosed froglets, particularly in Bufo and Hamptophryne, are likely apomorphic developmental traits within the Anura.& b d y :Larval and metamorphic skeletal development in the fast-developing frog Pyxicephalus adspersus (Anura, Ranidae)

Hyoid Skeleton, Its Related Muscles, and Morphological Novelties in the Frog Lepidobatrachus (Anura, Ceratophryidae)

“…The pars reuniens is reduced in basal anurans (Wiens, 1989;Haas, 1997;Maglia and Pugener, 1998;Pugener and Maglia, 1998) and in most anurans, the pars reuniens and basibranchial are incorporated into the anterior half of the hyoid plate (Sedra and Michael, 1958;Chacko, 1965;de Jongh, 1968;Haas, 1999;Fabrezi and Goldberg, 2009;among others). In Chacophrys pierottii and Ceratophrys spp.…”

Deconstructing cartilage shape and size into contributions from embryogenesis, metamorphosis, and tadpole and frog growth

“…Most tadpoles have a mobile suprarostral cartilage in the upper jaw and an infrarostral in the LJ that is of similar shape and size to the MC but aligned more laterally, anterolaterally or dorsomedially than the MC to complement the suprarostral (Pusey, 1938;Haas, 1999;Rocek, 2003;Haas et al 2006Haas et al , 2014. Xenopus tadpoles are distinguished by having their upper jaw skeleton comprised of a broad, immobile suprarostral plate, the edge of which remains straight and does not align with the curving LJ until late tadpole stages (Trueb & Hanken, 1992).…”

“…Despite many anatomical descriptions of PA skeletal development in metamorphosing frogs and salamanders (Pusey, 1938;Sedra & Michael, 1957, 1958van der Westhuizen, 1961;Chacko, 1965a;Wiens, 1989;Hall & Larsen, 1998;Haas, 1999;Rose, 2003), there has been little attempt to quantify changes in the shape and size of individual elements or to assess the contribution of growth to species-specific features of skeletal shape. This study uses allometric equations and thin-plate spline (TPSA), relative warp (RWA) and elliptic Fourier (EFA) analyses to describe shape and size changes of the ventral PA cartilages of the frog Xenopus laevis in tadpole and frog growth and metamorphosis.…”

Spawning and non-breeding activity of adult giant bullfrogs (Pyxicephalus adspersus)

“…Thus the largest count of males, and the duration of each observed spawning event was determined. Females were not counted because their smaller size and inconspicuous behaviour (Channing et al 1994;Cook 1996) made them difficult to detect.When eggs, tadpoles or newly-metamorphosed froglets were found without spawning having been observed, we estimated the date of spawning from the development of offspring (Gosner 1960;Van Wyk et al 1992;Haas 1999) and measurements of daily rainfall from Diepsloot Nature Reserve. Hence, for Summers 2-5, we estimated the annual number of spawning events as the sum of all spawning events that were observed or revealed by eggs, tadpoles or froglets.…”

“…When eggs, tadpoles or newly-metamorphosed froglets were found without spawning having been observed, we estimated the date of spawning from the development of offspring (Gosner 1960;Van Wyk et al 1992;Haas 1999) and measurements of daily rainfall from Diepsloot Nature Reserve. Hence, for Summers 2-5, we estimated the annual number of spawning events as the sum of all spawning events that were observed or revealed by eggs, tadpoles or froglets.…”