Acta Biológica Colombiana

Morphological anomalies, both skeletal and non-skeletal, have been reported in natural populations of amphibian anurans from a variety of habitats around the world (Henle et al., 2017a). In Brazil, some previous studies have described these anomalies, and most have focused on specific taxa (e.g., Pedroso-Santos et al., 2020; Souza et al., 2021). Among anomalies in anurans, brachydactyly (defined as normal number of metatarsals but an abnormal number of phalanges) are the most widespread and relatively common in semi-aquatic and terrestrial species, as well as anophthalmia (characterized by the absence of one or both eyes) in juveniles and post-metamorphic individuals (Henle et al., 2017a, b; Souza et al., 2021). Herein we report two records of anophthalmia in the genus Pristimantis Jimenez de la Espada, 1870 and one of brachydactyly in the genus Rhinella Fitzinger, 1826 in eastern Amazonia, Brazil.

Specimens of P. gutturalis were found in 2021 during surveys at Parque Nacional Montanhas do Tumucumaque (1.2699°N, 2.4389°W), and specimens of P. chiastonotus and R. castaneotica were found in 2022 at Parque Natural Municipal do Cancão (0.9027°N, 52.0049°W), both in the municipality of Serra do Navio, state of Amapá, Brazil. Both areas are inserted in the Amazonian rainforest, particularly in upland (non-flooding) primary forest with closed canopy and emergent trees, with climate tropical monsoonal (Am) (according to the Köppen-Geiger classification; Álvares et al., 2013).

On 07 September 2021, we found an anophtalmic P. gutturalis adult male (unvouchered specimen) with a missing left eye and a normal right eye (Fig. 1A). The second anophtalmic individual (P. chiastonotus; HERPLAP 3836; SVL = 32.8 mm) was registered on 30 April 2022, with missing right eye (Fig. 1B), and on 29 June 2022, we found an adult male R. castaneotica (HERPLAP 3913; SVL = 30.0 mm) showing brachydactyly in the right hindlimb (Fig. 1C–D). Classification of anomalies followed Henle et al. (2017b). The specimens were deposited in the Herpetological Collection of Universidade Federal do Amapá, Brazil.

To our knowledge, the data presented here demonstrate the first records of brachydactyly on R. castaneotica and anophthalmia on the frogs P. chiastonotus and P. gutturalis. According to Souza et al. (2021), brachydactyly is common in semi-aquatic and terrestrial species such as toads of the genus Rhinella. On the other hand, the occurrence of only one anomaly (eye colouration abnormal) in the family Craugastoridae (P. reichlei) suggests that anomalies both skeletal and non-skeletal may be rare in arboreal species (see Souza et al., 2021). Therefore, our data reinforce that anecdotal records are important for better knowledge about abnormalities in anurans.

In addition, both protected areas are well-preserved, and, therefore, the causes of the anomalies recorded here are unknown. While cases of anomalies in urban and perturbed areas are related to factors such as chemical contaminants (e.g. Ferrante and Fearnside, 2020), the cases within protected areas could be related to intrinsic genetic and developmental imperfections (Lunde and Johnson, 2012). In this sense, we suggest that all individuals were probably affected during the embryonary developing stage. Thus, future ecotoxicological studies of amphibian populations in protected areas are needed to investigate the causes of anomalies, which will provide important input for the conservation of the anuran population.

Figure 1: Anomalies in three frog species from eastern Amazonia.