Heterochrony during skeletal development of Pseudis platensis (anura, hylidae) and the early offset of skeleton development and growth

Abstract

The aquatic frog Pseudis platensis has a giant tadpole, long developmental time, and dissociated metamorphic events that include later offset of larval somatic morphologies. Moreover, when the tadpole metamorphoses, the young frog is nearly the size of an adult, suggesting that this species has low rates of postmetamorphic growth. Herein, we study the development of the skeleton during larval development up to the end of metamorphosis, which is denoted by the complete lost of the tail in P. platensis. Our study revealed heterochronic differences in skeletal development compared with that of most anurans; these involve the complete differentiation of skull bones and the extensive ossification of the postcranial skeleton before completion of metamorphosis. The skull of metamorphosing P. platensis has an ossified sphenethmoid and a fully formed plectral apparatus, thus differing with regard to the pattern observed in most anurans in which both developmental events take place during the postmetamorphic life. Despite the fact that the iliosacral articulation and the urostyle are present at the end of metamorphosis as in most anurans, ossification/calcification of carpus, tarsus, and limb epihyses during metamorphosis of P. platensis suggests that the postcranial skeleton lacks postmetamorphic growth. This study also includes a discussion of the pattern of development of the plectral apparatus, which allows us to propose a new hypothesis regarding pars externa plectri homology.

Morphological Variation in Anuran Limbs: Constraints and Novelties

“…Evidence that intercalary elements and the digital pads have different developmental trajectories was seen in studies of finger regeneration in Hyperolius viridiflavus (Richards et al., ). A single case in which the intercalary element is present, but the digital pad is absent, is Pseudis paradoxa (Manzano et al., ; Fabrezi and Goldberg, ). This suggests that this primarily aquatic frog had an arboreal ancestor, but has secondarily lost the capability to climb.…”

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.…”

Calls and tadpoles of the species of Lysapsus (Anura, Hylidae, Pseudae)

“…Tadpoles would have a disruptive/deflecting coloration when small to deflect invertebrate predators (Dixon et al, 1995), but would become darker to avoid fish predators as they grew larger and were no longer threatened by small predators. However, because Pseudis populations vary in adult sizes (Garda et al, 2010) in response to size at metamorphosis (Downie et al, 2009b;Fabrezi and Goldberg, 2009), tadpoles in some populations may not present pigmented stages because metamorphosis is triggered faster where ponds' permanence is not long enough. In fact, tadpoles of the sister species of P. minuta (P. cardosoi) are pigmented when large (DJS pers.…”