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

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.

Skeletal development of the Mexican spadefoot, Spea multiplicata (Anura: Pelobatidae).

The larval chondrocranium of Spea multiplicata is described, as is the development and adult morphology of the skeleton. There are major modifications to the larval chondrocranium throughout development, including the presence of embryonic trabeculae in young tadpoles and significant reorganization of cartilaginous structures at metamorphosis. The first bone to ossify is the parasphenoid (Stage 35), followed by the presacral neural arches, ilium, and femur (Stage 36). By Stage 39, most of the postcranial elements have begun to ossify. Metamorphic climax is accomplished over three Gosner stages (39-41) and involves major modifications to the chondrocranium, as well as the appearance of three cranial elements (septomaxilla, nasal, and premaxilla). After metamorphosis, the exoccipital, vomer, dentary, angulosplenial, squamosal, pterygoid, sphenethmoid, ischium, and hyoid begin to ossify. The stapes, mentomeckelian, operculum, carpals, and tarsals do not appear until juvenile and adult stages. The development of the hyoid and cartilaginous condensations of the carpals and tarsals are described. In addition, phenotypic plasticity within the genus and the absence of a palatine (= neopalatine) bone are discussed.

Skeletal morphogenesis of the vertebral column of the miniature hylid frog Acris crepitans, with comments on anomalies.

Although the vertebral columns of anurans have received much study in the last 150 years, few detailed descriptions exist of the skeletal morphogenesis of this anatomical unit. Herein, the ontogeny of the vertebral skeleton of the hylid frog Acris crepitans is described based on cleared and double-stained specimens, radiographs, and 3D reconstructions generated from synchrotron microCT scans. The adult axial formula is 1-7-1-1, and the vertebral centra are epichordal and procoelous. The neural arches are nonimbricate, and there is a medial articulation between the laminae of Presacrals I and II. Free ribs are absent. The sacral diapophyses are uniform in width or slightly expanded distally. The urostyle is slender, round in cross section, and about equal in length to the presacral region. Presacral vertebrae are the first to form, developing in a cephalic-to-caudal sequence. However, development and growth are decoupled and growth is fastest initially in the posterior presacrals and sacrum. In addition, there is a time lag between the formation of the presacral/sacral region and the postsacral region. More than 8.5% of the specimens examined have vertebral anomalies, and about 50% display small variants from the typical vertebral column morphology. However, these malformations do not seem to have been so severe as to have affected survival.

An anatomical ontology for amphibians.

Herein, we describe our ongoing efforts to develop a robust ontology for amphibian anatomy that accommodates the diversity of anatomical structures present in the group. We discuss the design and implementation of the project, current resolutions to issues we have encountered, and future enhancements to the ontology. We also comment on future efforts to integrate other data sets via this amphibian anatomical ontology.

Nitrincola lacisaponensis gen. nov., sp. nov., a novel alkaliphilic bacterium isolated from an alkaline, saline lake.

A novel alkaliphilic bacterium, strain 4CAT, was isolated from decomposing wood taken from the shore of Soap Lake, a saline, alkaline lake in Grant County, WA, USA. Cells of the isolate were Gram-negative, asporogenous, short, motile rods that utilized only a limited range of organic acids as sole carbon and energy sources. In addition to oxygen, the strain possessed the ability to reduce in the presence of acetate. Strain 4CAT was oxidase- and catalase-positive; it degraded Tween 60, but not DNA, urea, gelatin or starch. It grew at pH values from 7.5 to 11.0, with optimum growth occurring at pH 9.0, and growth was observed in NaCl concentrations of 0.2-1.3 M, with optimum growth at 0.8 M NaCl. The optimum temperature for growth was 37 degrees C. Strain 4CAT was resistant to erythromycin, bacitracin, novobiocin, polymyxin B, neomycin, gentamicin, streptomycin, carbenicillin, rifampicin and tetracycline, and was susceptible to nalidixic acid, chloramphenicol, ampicillin and penicillin. The isolate's 16S rRNA gene sequence indicated that it belonged to the gamma-Proteobacteria, showing 90-94 % similarity to its closest relatives. Maximum-likelihood phylogenetic inferences placed strain 4CAT within a novel lineage related to the marine bacterial genera Neptunomonas and Marinobacterium. The DNA G+C content of the isolate was 47.4 mol%. On the basis of genotypic and phenotypic characterization, it was concluded that strain 4CAT should be placed in a separate taxon as a novel genus and species, with the proposed name Nitrincola lacisaponensis gen. nov., sp. nov. The type strain is 4CAT (=ATCC BAA-920T=DSM 16316T).