Occurrence of Oral Deformities in Larval Anurans

We quantified deformities in the marginal papillae, tooth rows, and jaw sheaths of tadpoles from 13 population samples representing three families and 11 sites in the southeastern United States. Oral deformities were observed in all samples and in 13.5–98% of the specimens per sample. Batrachochytrium dendrobatidis (chytrid) infections were detected in three samples. There was high variability among samples in the pattern and number of discovered deformities. Pairwise associations between oral structures containing deformities were nonrandom for several populations, especially those with B. dendrobatidis infections or high total numbers of deformities. Comparisons of deformities among samples using multivariate analyses revealed that tadpole samples grouped together by family. Analyses of ordination indicated that three variables, the number of deformities, the number of significant associations among deformity types within populations, and whether populations were infected with B. dendrobatidis, were significantly correlated with the pattern of deformities. Our data indicate that the incidence of oral deformities can be high in natural populations and that phylogeny and B. dendrobatidis infection exert a strong influence on the occurrence and type of oral deformities in tadpoles.

Figure 1

Illustration of five morphological regions, including 19 morphological zones of the tadpole oral disc, used in quantifying deformities. UJS = Upper Jaw Sheath; A 1–2 = Anterior tooth rows 1 and 2; P 1–3 = Posterior tooth rows 1 through 3; VMP = Ventral Marginal Papillae; LJS = Lower Jaw Sheath; MP = Marginal Papillae; M = Mouth.

Figure 2

Examples of oral deformities found in tadpoles collected for study. (A) Gap in marginal papillae (MP code 2); (B) large, single flap replacing upper and lower marginal papillae (MP code 1); (C) teeth growing in marginal papillae (MP code 3); (D) (1) missing and stunted teeth (tooth row (TR) codes 1 and 4), (2) lack of keratinization in jaw sheath (jaw sheath [JS] code 3), (3) erosion of cutting edge of lower jaw sheath (JS code 1); (E) right A-1, A-2, and marginal papillae are absent (TR code 2 and MP code 2); (F) missing teeth in P-2 (TR code 1); (G) absent and stunted teeth, teeth with disrupted adjacent tissue in P-1, P-2 (TR codes 1, 2, 4); (H) (1) missing teeth with disrupted adjacent tissue in A-1 (TR code 2), (2) intersecting and convoluted tooth rows (TR codes 5 and 6), (3) teeth growing freely in marginal papillae (MP code 3). To facilitate comparison, all images are of Rana sphenocephala.

Figure 3

Two-dimensional ordination of tadpole oral deformities. Axes scores represent relative dissimilarity between numbers and types of deformities; separation of points in the graph is proportional to the magnitude of differences between them. Despite the detection of Batrachochytrium dendrobatidis in some samples, the types and quantities of oral defects were related to family. RASP = Rana sphenocephala, RASE = Rana sevosa, RACL = Rana clamitans, HYVE = Hyla versicolor/chrysoscelis, HYSQ = Hyla squirella, BUWO = Bufo woodhousii, BUFO = Bufo fowleri, BUNE = Bufo nebulifer.