Advertisement call of the Colombian Horned Frog Ceratophrys calcarata (Anura, Ceratophryidae)

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Ecophysiology of neotropical amphibians and reptiles: lessons learned from Colombia

Ecophysiology and herpetology share a close historical relationship, but earlier work at the interface of these disciplines was carried out in temperate regions. Tropical regions like the Neotropics exhibit the highest species richness for amphibians and reptiles, but the pace for ecophysiological research on tropical herpetofauna has been slower relative to temperate counterparts. We are a group of early-career, Latin American researchers interested in the physiological diversity exhibited by neotropical herpetofauna. As such, we have engaged in the organization of the Symposium on the Ecophysiology of Neotropical Amphibians and Reptiles (ECOPHYSHERP) to integrate the scientific community interested on these topics. ECOPHYSHERP has been held three times already within the Colombian Congress of Herpetology, and collectively it has hosted >60 contributions from researchers at 26 institutions and eight countries. Participation has been diverse in terms of gender, age, and career stage, but most participants have been young undergraduate biology students. This generation of early-career researchers is producing excellent research in a broad range of topics, but difficulties to convert this research into scientific publications may exist. Identifying and contributing in order to solve such problems are priorities for this organizing committee, and also our endeavours towards ECOPHYSHERP 4.0 in Santa Marta in 2025.

Contrasting effects of transdermal and implant corticosterone treatments in the American bullfrog wound healing

Glucocorticoid (GC) release is triggered by adverse stimuli that activate the hypothalamus-pituitary-adrenal/interrenal axis. Glucocorticoids may enhance or suppress immune functions depending on the level of elevation. In this study, we investigated the effects of transient and chronic increase of corticosterone (CORT) on the wound healing of the American bullfrog. Frogs were submitted to a daily transdermal hormonal application that acutely elevated CORT plasma levels, or vehicle as a control. Other frogs were surgically implanted with a silastic tube filled with CORT that resulted in chronic elevation of CORT plasma levels or received empty implants as a control. A dermal biopsy was performed to create a wound and was photographed every 3 days. Individuals treated with transdermal CORT started healing faster than their control 32 days after the biopsy. Frogs that received CORT implants tended to heal slower than control subjects. Plasma bacterial killing ability was not affected by treatment, which reinforces the constitutive nature of this innate immune trait. By the end of the experiment, frogs from the acute CORT treatment had smaller wounds compared with those receiving the CORT-filled implants, highlighting the differential effects of acute (immunoenhancing) and chronic (immunosuppressive) elevation of CORT plasma levels. This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'.

ACT-107, a novel variant of AmpC β-lactamase from Enterobacter huaxiensis isolated from Neotropical leaf frog (Phyllomedusa distincta) inhabiting the Brazilian Atlantic Forest

OBJECTIVE

The aim of this study was to characterize a broad-spectrum cephalosporin-resistant AmpC-positive Enterobacter huaxiensis colonizing the skin of a Neotropical frog (Phyllomedusa distincta) inhabiting the Brazilian Atlantic Forest.

METHODS

During a genomic surveillance study of antimicrobial resistance, we screened skin samples from P. distincta. Gram-negative bacteria growing on MacConkey agar plates supplemented with 2 µg/mL ceftriaxone were identified by MALDI-TOF-MS. A cephalosporin-resistant E. huaxiensis was sequenced by Illumina NextSeq platform. Genomic data were analized through bioinformatics tools, whereas AmpC β-lactamase was characterized in depth by comparative analysis of amino acids, in silico modeling, and susceptibility profile to β-lactam antibiotics and combinations with β-lactamase inhibitors.

RESULTS

Whole-genome sequencing analysis revealed a novel variant of AmpC β-lactamase belonging to the ACT family, designated as ACT-107 by NCBI. This variant contains twelve novel amino acid mutations within the ACT family, five in the signal peptide sequence (Ile2, Met14, Tyr16, Gly18 and Thr20), and seven in the mature protein (Gln22, His43, Cys60, Thr157, Glu225, Ala252 and Asn310). In silico modeling showed that substitutions occurring in the mature chain are localized in the solvent-accessible surface of the protein, where they are not expected to affect the β-lactamase activity, as observed in the resistance profile. Strikingly, undesignated ACT variants from E. huaxiensis were clustered (> 96% identity) with ACT-107.

CONCLUSIONS

Since E. huaxiensis has been isolated from human infection, clinical significance of ACT-107 needs surveillance and attention of clinicians.

A new small golden frog of the genus Pristimantis (Anura: Craugastoridae) from an Andean cloud forest of Colombia

A new species ofPristimantisis described from an Andean cloud forest at 2650 m in the Cordillera Oriental of Colombia.Pristimantis doradosp. nov. is similar to and could be closely related toP. acutirostris, but can be readily distinguished from this latter species by the absence of a tympanic annulus, vocal slits, vocal sac and reticulations on concealed surfaces, and by having a metallic gold iris with a brown horizontal streak. The phylogenetic position of the new species is recovered and we provide its advertisement call, which this species manages to emit despite lacking a vocal sac and vocal slits. This discovery reminds us that despite the extensive research on the alpha-taxonomy ofPristimantisin Colombia, fieldwork in high montane forests continues to yield previously unknown species.