Establishment of aquatic Rio Cauca Caecilians, Typhlonectes natans (Fischer 1880) (Gymnophiona: Typhlonectidae), in Florida, with notes on their relative abundance, distribution, and natural history

Abstract

In 2021, the first occurrence of an aquatic caecilian identified as a Rio Cauca Caecilian, Typhlonectes natans
(Gymnophiona: Typhlonectidae), in the Tamiami (C-4) Canal was documented in Florida, USA. However, whether
the species was established at the time was not known. We subsequently trapped for caecilians at nine different sites
along the main C-4 Canal and secondary canals between 2021 and 2024. We captured 115 caecilians and received
numerous additional reports and observations from multiple individuals. Caecilians of both sexes and all age classes
were captured. Twenty-seven preserved specimens were X-ray-imaged to check for pregnancy and stomach contents,
and 11 of those specimens were microCT-scanned. Three specimens contained late-stage fetuses, and one contained
stomach contents identified as fish bones. We screened 78 specimens for the presence of the amphibian fungal
pathogen, Batrachochytrium dendrobatidis (Bd), but did not detect Bd on any specimens. Results suggest that T. natans
is well established and locally abundant in at least 16 km of the C-4 Canal system. Preliminary results suggest their
diet consists primarily of soft-bodied prey and/or scavenged vertebrate carrion. The caecilians do not appear to be a
reservoir for transmission of Bd, although further testing is required. Further studies are needed to better understand
their distribution, biomass, reproductive cycles, diet, movement patterns, role in disease transmission, risk of spread,
and basic biology. Efforts are needed to assess the viability of eradication or control and to understand how the
establishment of these aquatic caecilians might affect freshwater ecosystems in southern Florida.