Skeletal morphology and postmetamorphic ontogeny of Acris crepitans (Anura: Hylidae): A case of miniaturization in frogs

Abstract

Acris crepitans is a small, semiaquatic member of the treefrog family Hylidae. Much recent attention has been paid to this species because of reports of population declines and malformations, yet few works have considered the skeletal anatomy of this common North American frog. Herein, we provide a detailed description of the morphology and adult ontogeny of the skeleton of A. crepitans, and discuss novel morphologies, interesting postmetamorphic developmental patterns, and intraspecific skeletal variation. The reduced amount of adult ossification, as well as several novel morphologies present in this species, are consistent with patterns of miniaturization seen in other anurans. For example, the skull is poorly ossified, but most of the cranial cartilages are heavily mineralized, the nasal bones are fused to endochondral ossification of the tectum nasi, the palatines are reduced, and the prootics and exoccipitals are not fused to one another (although the prootics are well-developed and ornamented). In addition, several specimens exhibit abnormalities, which might indicate that: (1) the population was under an acute malformation outbreak, (2) a high incidence of small skeletal malformations is normal in this species, (3) the population is under stress because of habitat fragmentation, (4) there is environmental deterioration in the region where the specimens were collected, and/or (5) the species is now showing signs of decline in southern Missouri. Regardless of the cause, it is clear that further examination of skeletal variability in A. crepitans, including ossification patterns and the frequency of abnormalities, is warranted.

Heterochrony in Growth and Development in Anurans from the Chaco of South America

“…Mineralization of epiphyses, carpal/tarsal elements, and prepollical/prehallical elements takes place when growth stops or is decelerated (Fabrezi 1992(Fabrezi , 1993(Fabrezi , 2001Fabrezi and Alberch 1996;Fabrezi and Barg 2001;). Literature data for skull ossification in non-pipoid anuran are based on: de Sá (1988), Wiens (1989), Wild (1997Wild ( , 1999, Maglia (1997, 2007), Maglia and Pugener (1998), Haas (1999), Perotti (2001), Sheil and Alamillo (2005), Maglia et al (2007), Fabrezi and Quinzio (2008), and .…”

The ontogeny of Pseudis platensis (Anura, Hylidae): Heterochrony and the effects of larval development on postmetamorphic life

“…In Pseudacris maculata and P. triseriata, the oldest males are 3 years old, and the younger mature males are 2 years old (Platz and Lathrop, 1993). However, in Acris crepitans the complete population turnover occurs in 16 months and postmetamorphic growth involves increases of size and rapid attainment of reproductive maturity (Maglia et al, 2007). Larval development in P. platensis occurs, at least, in 6 months , and skeletochronological data on sexually mature specimens revealed they could reach 3 years of age, which could indicate postmetamorphic stages would comprise 75% of the life span.…”

“…Data on age for hylids are limited to a few miniature species (Platz and Lathrop, 1993;Maglia et al, 2007). In Pseudacris maculata and P. triseriata, the oldest males are 3 years old, and the younger mature males are 2 years old (Platz and Lathrop, 1993).…”

How can ontogeny help us to understand the morphology of anuran pectoral girdle?

“…There are also many studies on developmental osteology of Anura, but only several of them describe minutely an early ontogenetic development of the pectoral girdle (Wiens 1989;Trueb and Hanken 1992;Maglia and Púgener 1998;Perotti 2001;Sheil and Alamillo 2005;Maglia et al 2007) and only a few of them describe in detail the origin and growth of epicoracoid cartilage but only in isolated species (Shearman 2005(Shearman , 2008Havelková and Roček 2006). Also, an overlap of epicoracoids and presence or absence of epicoracoid horns were studied mainly by histological sections but in fact only on adult specimens or several isolated stages, so the developmental aspect of these arrangements remains neglected (Kaplan 2000(Kaplan , 2001(Kaplan , 2003(Kaplan , 2004.…”