Current status of American bullfrog, Lithobates catesbeianus, invasion in Uruguay and exploration of chytrid infection

The American bullfrog Lithobates catesbeianus is an invasive species that can strongly affect native amphibian communities through competition, predation, or introduction of diseases. This frog has invaded multiple areas in South America, for which niche models predict suitable environments across much of the continent. This paper reveals the state of the invasion of this species in Uruguay and its possible relationship with the chytrid pathogenic fungus, Batrachochytrium dendrobatidis. Surveys at invaded sites were conducted from 2007 to 2015, identified two populations undergoing recent range expansion (one of them exponential), two populations that failed to establish, and a new record in an urban area of the capital city, Montevideo. In all the analysed feral populations, chytridiomycosis was found. Our data suggest that the invasion of L. catesbeianus in Uruguay is at an early stage, with very localized populations, which might allow for the implementation of cost-effective management plans, with eradication constituting a plausible option

Assessment of the calling detection probability throughout the day of two invasive populations of bullfrog (Lithobates catesbeianus) in Uruguay

Bullfrog invasion is a major conservation concern in South America, so there is an urgent need to detect and monitor its many invasion foci. Amphibian sampling methods commonly use calling display, specifically the nuptial calls of males. With the aim of obtaining the better day period to sample and monitor Lithobates catesbeianus presence, we recorded its calls at three ponds in two invaded localities in Uruguay (Aceguá, Cerro Largo, and San Carlos, Maldonado) during the reproductive season. Then, we studied the records, obtaining a subsample of calling intensity at the first 5 minutes for each hour. We detected that vocalization intensity remained almost constant between 20:00 and 05:00 h. Detection probability remained high and constant during this period, and then decreased. Therefore, bullfrog displays a constant calling activity during the nights of its reproductive period, even longer than native anurans. This long calling period facilitates its detection during nocturnal sampling

Assessment of the calling detection probability throughout the day of two invasive populations of bullfrog (<i>Lithobates catesbeianus</i>) in Uruguay

Bullfrog invasion is a major conservation concern in South America, so there is an urgent need to detect and monitor its many invasion foci. Amphibian sampling methods commonly use calling display, specifically the nuptial calls of males. With the aim of obtaining the better day period to sample and monitor Lithobates catesbeianus presence, we recorded its calls at three ponds in two invaded localities in Uruguay (Aceguá, Cerro Largo, and San Carlos, Maldonado) during the reproductive season. Then, we studied the records, obtaining a subsample of calling intensity at the first 5 minutes for each hour. We detected that vocalization intensity remained almost constant between 20:00 and 05:00 h. Detection probability remained high and constant during this period, and then decreased. Therefore, bullfrog displays a constant calling activity during the nights of its reproductive period, even longer than native anurans. This long calling period facilitates its detection during nocturnal sampling.Asociación Herpetológica Argentina (AHA

American bullfrog (Lithobates catesbeianus) diet in Uruguay compared with other invasive populations in Southern South America

Between 2000-2020, more than ten new populations of the invasive American bullfrog (Lithobates catesbeianus) have been reported in the southern cone of South America. We studied the stomach contents of 126 bullfrogs from a population at an early invasion stage in Uruguay (Acegua, Cerro Largo Department). We observed a rich diet, with extensive prey volume range (1 mm3 to more than 7 000 mm(3)); the most frequent items were Hymenoptera (19.6%), Coleoptera (16.4%), Amphipoda (13.3%), Anura (8.9%) and Heteroptera (8.7%). Despite some overlap, differences were observed in volume (chi(2) = 54.6, p \u3c0.001, d.f. = 2) and prey quantity (F = 8.1, p \u3c0.001, d.f. = 79) between males, females, and juveniles. Juveniles showed significantly higher consumption of terrestrial prey by count (82% of their total ingestion) than adults (29% for males and 32% for females) (chi(2) = 28.5, p \u3c0.001, d.f. = 2). Adults, especially females, showed a high frequency of cannibalism (33% of their total ingestion; chi(2) = 20.9, p \u3c0.001, d.f. = 2). Comparing our data with other bullfrog regional studies, we found great plasticity in trophic habits and differences in the incidence of cannibalism (higher incidence in the populations of Acegua, Uruguay, and Buenos Aires, Argentina). These differences could be related to local biodiversity, but also could be affected by the invasion phase. Cannibalism frequency was higher in small bullfrog populations, where it could be favoring the establishment success. This shift in foraging strategies during the invasion process had been insufficiently evaluated in amphibians. Knowing the ecological determinants for the invasion by bullfrogs can be useful to the development of management strategies

The tadpole and karyotype of Rhinella (Bufo) achavali (Anura: Bufonidae)

We describe the external morphology, buccal cavity, chondrocranium, hyobranchial skeleton and musculature of the tadpole of R. achavali, along with its karyotype. Tadpoles were found in a permanent streamlet, showing schooling behavior. External larval morphology seems to be much conserved in Rhinella, not helping in the characterization of the proposed species groups. Buccal cavity morphology confirms the distinctiveness of the R. veraguensis group with respect to other known Rhinella. Musculoskeletal characters show most features shared with other Bufonidae, except for some typical of the basal genus Melanophryniscus. Karyotype is composed of 22 biarmed chromosomes, with secondary constrictions in pair 7, like the other species in the R. marina group.Fil: Kolenc, Francisco. Museo Nacional de Historia Natural. Sección Herpetología; UruguayFil: Borteiro, Claudio. Museo Nacional de Historia Natural. Sección Herpetología; UruguayFil: Cotichelli, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Baldo, Juan Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Martinez Debat, Claudio. Universidad de la Republica; UruguayFil: Vera Candioti, María Florencia. Fundación Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán; Argentin