High frequency of larval abnormalities of the toad Rhinella arenarum (Anura: Bufonidae) in an Argentinian agroecosystem

SANSIÑENA, JESICA A.; PLAUL, SILVIA E.; BAHL, M.F.; PICCININI A.; LAUBE, ANDRES; ALCALDE, LEANDRO; NATALE, GUILLERMO S.

REVISTA DE BIOLOGíA TROPICAL

REVISTA DE BIOLOGIA TROPICAL

Año: 2023 vol. 71

0034-7744

Introduction: The frequent use of pesticides is currently considered a cause of environmental pollution due tothe high rate of entry of these substances into agroecosystems. This constitutes a risk for the species that inhabitthese ecosystems, in particular anurans whose characteristics make them prone to exposure to and interactionwith environmental pollutants.Objective: To report the occurrence of abnormalities in larvae of the common toad Rhinella arenarum inhabitingponds surrounded by agroecosystems.Methods: In two consecutive springs (2015 and 2016), reproductive events of common toads were monitoredin temporary pond systems in agricultural and non-agricultural areas, located near the city of La Plata (BuenosAires, Argentina). The physicochemical parameters of the ponds were measured, and the stage of each reproductiveevent was recorded, such as the numbers of adult toads, amplexus and clutches. In the laboratory, thelarvae were measured and photographed, their stage of development was recorded, and their morphology wasexamined under a stereomicroscope. Representative samples (normal and abnormal) from each pond studiedwere processed for histopathological analysis.Results: In the field studies carried out on a population of R. arenarum collected in an agroecosystem, a lowernumber of reproductive adults and clutches were observed in relation to the population of a non-agriculturalpond. A total of 1 910 larvae were collected: 529 and 1 381 larvae from ponds located in non-agricultural andagricultural areas, respectively. Larvae from the agroecosystem showed two types of abnormalities: severe tailflexure and abdominal bloating. In addition, five degrees of severity could be determined in relation to abdominalbloating.Conclusions: This work reports the high frequency and severity of abnormalities observed in the early stages ofR. arenarum larvae living within an agroecosystem, providing evidence of the negative impact that agriculturalactivities cause on aquatic ecosystems surrounded by farming areas.Key words: anuran larvae; abdominal bloating; histopathological studies; common toad; crop areas.