Clarisa de Lourdes Bionda

Reproductive Ecology of the Common South American Toad Rhinella arenarum (Anura: Bufonidae): Reproductive Effort, Clutch Size, Fecundity, and Mate Selection

Abstract Understanding the causes of population declines is difficult when the ecology of the organisms themselves is insufficiently known. The common South American toad, Rhinella arenarum, inhabits a wide variety of habitats. Their populations are abundant; however, life-history characteristics of the adult, including reproductive traits, are poorly known. We studied the reproductive ecology of R. arenarum for several populations in central Argentina during two breeding seasons (2007–08). Breeding activity was compared for the two seasons with respect to variation in habitat variables. Females deposited a mean of 23,226.67 eggs per clutch (N  =  10), and snout–vent length did not show any significant effect on the number of eggs. Spawning females lost 27% of their mass when spawning occurred, and the heavier females had greater reproductive output. We found a significantly positive relationship between amplexed male and female snout–vent lengths, indicating size-assortative mating. Females in good body and somatic condition produced larger clutches independent of snout–vent length. Because clutch hydration in ponds occurs, reproductive effort as a function of body loss mass of spawning females is a more appropriate estimate of reproductive output for R. arenarum. Trends in the number of egg strings over several breeding periods can provide information about changes in population size. Long-term studies designed to monitor populations are needed to determine the impacts and consequences of environmental changes.

Health status of tadpoles and metamorphs of Rhinella arenarum (Anura, Bufonidae) that inhabit agroecosystems and its implications for land use

Perturbations of water bodies near agricultural and livestock systems can affect embryonic and larval stages of anurans and negatively impact adult populations and structure of amphibian communities. This study is focused on early development of Rhinella arenarum, for which body growth, abnormalities in the oral disc and genetic damage on erythrocytes were analyzed to establish the impact of agroecosystems on local populations of amphibians. Tadpoles and metamorphs of R. arenarum were collected in three agroecosystems (namely, C1, C2, and C3) and in a site without agricultural and livestock activities (SM) from central Argentina. Egg masses of C1 were extracted for breeding tadpoles under laboratory conditions (Lab). Tadpoles were in small size and lighter in weight in C1 and C2. Metamorphs were shorter and lighter in weight in C1 and C3. In SM and Lab samples, no tadpoles with abnormal LTRF (labial tooth row formula) or without labial teeth were observed. In C1, the highest frequency of abnormal LTRF was recorded and was the only site in which tadpoles without labial teeth were found. In C1 and C2 the tadpoles had highest micronucleus frequencies and nuclear abnormalities. C1 can be considered as the site with the highest anthropogenic perturbation and with less healthy tadpoles. Livestock practices such as alternating cattle between parcel and keeping a buffer between crops and water bodies, would allow a better development of the first aquatic stages that are essential for the conservation of the anuran populations.

Common toad Rhinella arenarum (Hensel, 1867) and its importance in assessing environmental health: test of micronuclei and nuclear abnormalities in erythrocytes

Anthropogenic activities may generate significant changes in the integrity of aquatic ecosystems, so long-term monitoring of populations that inhabit them is crucial. Counting micronucleated erythrocytes (MN) and erythrocytic nuclear abnormalities (ENA) in peripheral blood is a widely used method for detecting chromosomal damage due to chemical agents in the water. We analyzed MN and ENA frequency in blood obtained from the common toad Rhinella arenarum populations in sites with different degrees of environmental degradation. The results of this study indicate that there is an association between the frequency of micronuclei and nuclear abnormalities and the degree of environmental alteration recorded for the sites studied.

Variation in erythrocyte size between juveniles and adults of Odontophrynus americanus

Differences in erythrocyte size between tadpoles and adults have been found in numerous anuran species but there are no references about erythrocyte size of juveniles. We measured the size of red blood cells and nuclei of juvenile and adult individuals of Odontophrynus americanus. Erythrocyte and nuclear size of juvenile were significantly smaller than the corresponding sizes of adults. The erythrocytes of juvenile O. americanus were comparable in size to the erythrocytes of adult O. cordobae. We discuss about the possibility of correctly distinguishing juvenile O. americanus (tetraploid) from adult O. cordobae (cryptic diploid counterpart) specimens using erythrocytes. We also discuss possible causes of variation.

Adverse effect of agroecosystem pond water on biological endpoints of common toad (Rhinella arenarum) tadpoles

Chemical prroducts used in farming and wastes from livestock can contaminate pond water in agroecosystems due to runoff. Amphibians using these ponds for breeding are probably exposed to pollutants, and serious consequences might be observed afterward at the population level. Assessment biological endpoints of anuran to water quality give a realistic estimate of the probability of occurrence of adverse effects and provide an early warning signal. In this study, the ecotoxicity of agroecosystem ponds from the south of Córdoba province, Argentina, was investigated. Ponds in four sites with different degrees of human disturbance were selected: three agroecosystems (A1, A2, A3) and a site without crops or livestock (SM). The effect of pond water quality on the biological endpoint of Rhinella arenarum tadpoles was examined using microcosms with pond water from sites. Biological endpoints assessed were as follows: mortality, growth, development, morphological abnormalities (in body shape, gut, and labial tooth row formula), behavior, and blood cell parameters (micronucleus and nuclear abnormalities). Results indicated that water from agroecosystems has adverse effect on early life stage of R. arenarum. High mortality and fewer metamorphs were recorded in the A1 and A3 treatments. Tadpoles and metamorphs from A1 and A2 treatments had lower body condition. Tadpoles from A1 and A3 showed the highest prevalence of morphological abnormalities. The lowest amount of tadpoles feeding and the highest percentage of tadpoles swimming on the surface were observed in treatments with agroecosystem pond water. The higher frequencies of micronuclei and nuclear abnormalities were recorded in tadpoles from A1, A2, and A3 treatments. We check the sensitivity of the biological endpoints of R. arenarum tadpoles like early warning indicators of water quality. We found that the poor water quality of agroecosystem ponds has impact on the health of the tadpoles, and this could affect the persistence of populations. We recommend implementation of management actions before the harmful effects of agroecosystem pond water on early life stage of anuran become evident in higher ecological levels.