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Dormancy is an adaptive mechanism found in cladoceran species to tolerate hydrologic fluctuations in temporary habitats. However, the effects of hydroperiod length on invertebrate community structure remain not fully understood. In this study, we conducted an experiment to assess changes in community structure of dormant stages of cladoceran species among ponds with different hydroperiods. Dry sediment samples were collected from intermittent ponds in southern Brazil, posteriorly assigned to three hydroperiod categories (long, medium and short). We tested for differences in the richness and composition of emerging cladoceran species along this hydroperiod gradient. Nine species emerged over the experiment, and cladoceran community structure changed among hydroperiods. Cladoceran richness was higher in medium‐ than in short‐ and long‐hydroperiod ponds. In addition, the composition of cladoceran species changed significantly between short‐ and long‐hydroperiod ponds. Our results indicated that changes in hydroperiod of intermittent ponds influenced the dormant stages of Cladocera, an important result regarding future predicted changes in hydric regime of freshwater ecosystems due to human‐induced climate change. We propose that desiccation‐resistant cladoceran species are likely to predominate and that richness of egg banks tends to be higher in ponds that hold water for periods shorter than 1 year.

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The sensitivity of Danio rerio to three chemicals was compared at two growth stages [larval (10 ± 2 after hatching) and post-larval (60 ± 4 days after hatching)] based on acute toxicity tests. Thirty-nine 48 h acute toxicity tests were performed with the substances CuSO4, NaCl and KCl. The 48 h LC50 values at the two growth stages were compared by independent samples t-tests. The results showed a clear decrease in sensitivity when post-larval organisms were used. Since acute toxicity test methods for D. rerio that recommend using post-larval stage fish do not represent the most sensitive stage of the test organism, our study suggests a revision of the methods to use larval fish.

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The community structure of aquatic invertebrates producing dormant propagules has been associated with both local and regional-scale factors in temporary wetlands. We explore how patterns in the diversity of drought-resistant aquatic invertebrates are related to different spatial scales in ponds with distinct plant structural complexities. We tested 3 hypotheses: (1) the finest spatial scale (fine-scale diversity) has the strongest contribution to diversity and composition; (2) the fine-scale diversity will be higher in habitats that are more complex; and (3) the habitat-scale diversity has a higher contribution to regional diversity than broad-and fine-scale diversity. Dry sediment samples were collected from 3 ponds with 2 distinct plant habitats. The findings from individual partitions show that the importance of spatial scales was different between habitats. Fine-scale diversity represented a greater fraction of the total diversity for the habitat with the highest complexity, and broad-scale diversity showed a substantial contribution to total diversity in the habitat with the lowest complexity. Habitat-scale diversity contributed most to regional diversity, which underlines the importance of habitat type in the diversity of aquatic invertebrates that produce dormant propagules in temporary ponds.

Most zooplankton species inhabiting seasonal ponds produce dormant stages to overcome the dry seasons. Zooplankton specimens emerging from the sediment contribute to the ecological dynamics of these ecosystems, because they constitute important energy sources for higher trophic levels in aquatic food webs. In contrast to snapshot studies of the active communities, studying the ecological correlates of the distribution of the egg bank can help identify the potential drivers of zooplankton composition. We tested the association of local (habitat structure and water chemistry), climatic and spatial predictors with the alpha and beta diversity of zooplankton hatchling communities in subtropical seasonal ponds. Incubation experiments were conducted with sediment samples from 11 ponds distributed along an approximately 500‐km latitudinal gradient in southern Brazil. We assessed the patterns for the total community, Cladocera only and Rotifera only. The alpha diversity of the total community and Cladocera were primarily related to substrate heterogeneity. Annual rainfall and substrate heterogeneity jointly influenced the beta diversity of the total community. Annual rainfall solely influenced the beta diversity of Cladocera, while substrate heterogeneity influenced the overall beta diversity of Rotifera. Overall, the distinct relationships of the total hatchling community and Cladocera and Rotifera with the explanatory datasets suggest differing sensitivities of the zooplankton groups to impacts in habitat structure and climatic conditions in subtropical seasonal ponds.

Acantholeberis smirnovi Paggi & Herrera-Martinez, 2020 (Cladocera: Acantholeberidae) was recently described from Andean habitats in South America. The presence of a population on the eastern coast of the continent brought the hypothesis of a new Neotropical species different from A. smirnovi. This hypothesis was confirmed from morphological, ecological and biogeographic evidence. Acantholeberis accolismaris Sousa, Elmoor-Loureiro & Álvarez-Silva sp. nov. differs from A. smirnovi in the morphology of the head, the valves and the limbs (especially the second and third limbs). Species of Acantholeberis are adapted to live in acid water bodies, with A. accolismaris sp. nov. presenting the same ecological requirements. However, the new species is adapted to live in temporary ponds near the Atlantic Ocean in Brazil in altitudes ranging between 4 and 15 meters above sea level. Considering that Acantholeberidae is an ancient taxon with a pre-Mesozoic origin, geological and environmental changes may have been relevant to speciation and to the observed biogeographic pattern of species of Acantholeberis in Neotropics.