Effects of isolated and combined exposures of Boana curupi (Anura: Hylidae) tadpoles to environmental doses of trichlorfon and ultraviolet radiation.

The biodiversity collapse strongly affects the amphibian group and many factors have been pointed out as catalytic agents. It is estimated that several events in the amphibian population decline worldwide may have been caused by the interaction of multiple drivers. Thus, this study aimed to evaluate the stressful effects of the exposure to environmental doses of trichlorfon (TCF) pesticide (0.5 µg/L; and an additional 100-fold concentration of 50 µg/L) and ultraviolet radiation (UV) (184.0 kJ/m² of UVA and 3.4 kJ/m² of UVB, which correspond to 5% of the daily dose) in tadpoles of the Boana curupi species (Anura: Hylidae). The isolated and combined exposures to TCF happened within 24 h of acute treatments under laboratory-controlled conditions. In the combined treatments, we adopted three different moments (M) of tadpole irradiation from the beginning of the exposures to TCF (0 h - M1; 12 h - M2; and 24 h - M3). Then, we evaluated tadpole survival, change in morphological characters, induction of apoptotic cells, lipid peroxidation (LPO), protein carbonyl content (PCC), glutathione S-transferase (GST), non-protein thiols (NPSH), and acetylcholinesterase (AChE), as well as the induction of genomic DNA (gDNA) damage. UVB treatment alone resulted in high mortality, along with a high level of apoptosis induction. Both UVA, UVB, and TCF increased LPO, PC, and AChE, while decreased GST activity. Regarding co-exposures, the most striking effect was observed in the interaction between UVB and TCF, which surprisingly decreased UVB-induced tadpole mortality, apoptosis, and gDNA damage. These results reinforce the B. curupi sensitivity to solar UVB radiation and indicate a complex response in face of UVB interaction with TCF, which may be related to activation of DNA repair pathways and/or inhibition of apoptosis, decreasing UVB-induced tadpole mortality.

Diversity and distribution of mollusks along the Contas River in a tropical semiarid region (Caatinga), Northeastern Brazil

An inventory of macroinvertebrates conducted in the Contas River basin in Northeastern Brazil found 13 species of freshwater mollusks. Most of the community was represented by pulmonate gastropods, including Physa acuta, Drepanotrema anatinum, D. cimex, D. lucidum, Biomphalaria straminea?, Gundlachia radiata?, G. ticaga and Hebetancylus moricandi; the prosobranchs Pomacea archimedis?, Melanoides tuberculata and Littoridina sp. were also found. Bivalves were less diversified, represented only by Pisidium pulchellum? and Eupera simoni?. The taxonomic composition and the small size of many species reflect the intermittent condition of the basin. Additionally, the occurrence of shells of five terrestrial species (Helicina angulata, Gastrocopta pellucida hordeacella?, Beckianum beckianum, Succinea sp. and Systrophiidae gen. et sp. indet.) in the rivers reflects the occasional heavy rainfalls and floods in the region. The invasive gastropod M. tuberculata was the most abundant and widely distributed species. All 13 species were found in the lower course, in the Atlantic Forest region, and most, but not all, were recorded in the upper course, in the Caatinga region. The distribution and the occurrence of the bivalve species exclusively in the Atlantic Forest region indicate that the locally higher annual precipitation provides favorable conditions for the survival of these mollusks, such as a more stable hydroperiod.

Treze espécies de moluscos de água doce foram encontradas em um inventário de macroinvertebrados realizado ao longo da bacia do Rio de Contas, no Nordeste do Brasil. A maioria da comunidade foi representada por gastrópodes pulmonados, como Physa acuta, Drepanotrema anatinum, D. cimex, D. lucidum, Biomphalaria straminea?, Gundlachia radiata?, G. ticaga e Hebetancylus moricandi, embora prosobrânquios, como Pomacea archimedis?, Melanoides tuberculata e Littoridina sp. também tenham sido encontrados. Bivalves foram menos diversificados, e foram representados por Pisidium pulchellum? e Eupera simoni?. A composição taxonômica e o pequeno tamanho alcançado por muitas espécies refletem a condição intermitente da bacia. Além disso, a ocorrência de conchas de cinco espécies terrestres (Helicina angulata, Gastrocopta pellucida hordeacella?, Beckianum beckianum, Succinea sp. e Systrophiidae gen. et sp. indet.) dentro dos rios reflete as fortes chuvas e inundações que ocorrem ocasionalmente na região. O gastrópode invasor M. tuberculata foi a espécie mais abundante e bem distribuída. Todas as espécies foram encontradas no curso inferior, na região da Mata Atlântica, e a maioria, mas não todas, foram registradas no curso superior, na região da Caatinga. Esta distribuição e a ocorrência das espécies de bivalves exclusivamente na região da Mata Atlântica indicam que a maior precipitação anual desta região fornece condições favoráveis para a sobrevivência destes moluscos, como um hidroperíodo mais estável.

Diversidade de moluscos em riachos de uma regiao de encosta no extremo sul do Brasil / Diversity of mollusks in streams of a montane region in southern Brazil

Moluscos de riachos de uma região de encosta, no extremo sul do Brasil (Bacia do Rio Toropi) foram inventariados através de coletas conduzidas em 40 locais, com altitudes variando entre 70 e 500 metros. Ao todo, 18 espécies foram encontradas, representadas predominantemente por gastrópodes (11 espécies, 89,5% dos indivíduos). Potamolithus catharinae e Uncancylus concentricus foram as espécies dominantes. A última espécie também foi a melhor distribuída, estando presente em 81% dos locais amostrados. Entre os bivalves, apenas a espécie asiática invasora Corbicula fluminea foi abundante, mas ocorreu em um único local de coleta. Cerca de quatro espécies foram raras, estando representadas por não mais que três indivíduos. Apenas duas espécies de Unionoida foram encontradas. A dominância e a maior diversidade de gastrópodes em relação ao registrado para bivalves reflete o substrato predominantemente cascalhoso dos riachos da Bacia do Rio Toropi. A baixa riqueza registrada na área de estudo pode ser atribuída à escassez de sedimentos finos e de macrófitas, fatores que costumam favorecer a diversidade de moluscos. Essa condição também caracteriza outros riachos do sul do Brasil.

Stream mollusks in a region of slope in southern Brazil (Toropi River Basin) were inventoried by means of collections conducted in 40 sites, in altitudes ranging from 70 to 500 meters. At a whole, 18 species were found, represented predominantly by gastropods (11 species, 89.5% of the individuals). Potamolithus catharinae and Uncancylus concentricus were the dominant species. The latter was also well distributed, occurring in 81% of the sampling sites. Among the bivalves, only the invasive Asian clam Corbicula fluminea was abundant, but it occurred in only one sampling site. Four species were rare, being represented by less than three individuals, and the Unionoida were represented by two species only. Dominance and diversity of gastropods were higher than the bivalves, reflecting the gravel substrate of stream beds in the Toropi River Basin. The low richness recorded in the area studied is related to paucity of fine sediments and macrophytes in the streams, factors that commonly favors mollusks diversity. This condition also characterizes other southern Brazilian streams.