Janet Higuti

Dormant structures produced by aquatic microorganisms are ecologically important for restoring ecosystems after extreme climatic events. Among these events, heat waves cause the desiccation of environments and expose sediments to high temperatures, which reduce the viability of dormant propagules. Here, we measured the richness and species composition of the dormant aquatic microfauna (ciliates, rotifers, cladocerans, copepods and ostracods) hatched from sediments heated under a gradient of increasing temperatures. Sediment samples were collected from a temporary lake in the Upper Paraná River floodplain, Brazil. The material was exposed at temperatures of 25°C, 30°C, 40°C, 50°C, and 60°C. They were subsequently inundated and kept in mesocosms at 25°C with a 12‐h light/dark photoperiod for 8 weeks. Hatched organisms were harvested weekly. Increasing drying temperature significantly reduced the richness of hatching aquatic microfauna and led to significant differences in species composition between temperature treatments, although these trends were less linear for microcrustacean. Temperatures above 50°C (not uncommon for dried sediments exposed to direct sun in humid tropical areas) negatively affected community richness and promoted biotic homogenization of the communities hatched from the egg bank. Therefore, increased sediment temperatures in dry wetlands are a potential threat to dormant microfauna through biotic homogenization and species loss. Mitigation measures may be needed to conserve wetland egg banks.

Environmental integrity is vital for the long‐term preservation of freshwater biodiversity, which is currently among the most threatened on Earth due to anthropogenic pressures such as dam construction. The present study investigated the temporal responses of ostracod communities over 8 years (2017–2024) in the Upper Paraná River floodplain, comparing a protected area (Ivinhema River) and a dam‐impacted area (Paraná River). We evaluated taxonomic and functional attributes including richness, abundance and composition, using Generalized Linear Mixed Models (GLMMs) and multivariate analyses. Results revealed contrasting dynamics: The protected area exhibited high temporal stability in abundance, functional richness and composition, with a slight richness increase correlated with electrical conductivity. Conversely, the dam‐impacted system showed significant temporal increases in species richness, abundance and functional richness, alongside significant taxonomic and functional reorganization. These shifts in the Paraná system were positively associated with dissolved oxygen levels, likely reflecting increased water transparency from upstream dams that promotes submerged macrophyte expansion and periphyton growth. The hatching of resistant egg banks and the influence of invasive species also contributed to these community changes. In conclusion, protected areas are effective at maintaining regional biodiversity stability and ecological integrity. Meanwhile, the impacted system demonstrates a trajectory of continuous community reorganization, highlighting how environmental stressors alter long‐term ecological dynamics. This research underscores the critical importance of long‐term ecological research for evaluating conservation policies.

The ostracod genus Elpidium is known so far for South and Insular America and all of its 20 known species are confined to phytotelmata, mostly in tank-bromeliads. These plants, with more than 1200 species in the Atlantic Forest along the eastern shores of Brazil, can be either terrestrial or epiphytic, and occur along a vast altitudinal gradient. In recent decades, an international, even intercontinental, trade in ornamental bromeliads has expanded. These plants can be transported over large distances, and in some cases contain “passenger” taxa in their tanks, mostly insects and crustaceans. Here, we report on the discovery of two species of Elpidium from bromeliad phytotelmata in New Caledonia (Melanesia, Pacific Ocean). By coincidence, the same two species had also recently been collected from their presumed native area, one from Insular America (Dominican Republic and US Virgin Islands) and one from South America (Itapeva park in southern Brazil). These two species, Elpidium alarconi Mesquita-Joanes et al., 2025 and Elpidium itapevaense sp. nov., are here reported and (re-) described. Morphological comparisons with the populations from New Caledonia are provided.

Subtropical wetlands are considered biodiversity hotspots due to their complex and diverse habitats; however, their ostracod communities remain underexplored, particularly in the Northeastern Argentina (NEA) region. This study presents the first regional survey that combined previously published literature with field sampling of ostracod communities. Five families and 30 ostracod species were identified from 28 wetlands across the NEA region, including water bodies with different anthropogenic influences, plant compositions and water regimes, such as temporary and permanent lakes, streams and paddy fields. Seventeen out of the 30 species were recorded for the first time in Argentina, and a further two are new records for the region, increasing to 84 species the ostracod fauna reported for the country. Some taxa are left in open nomenclature, highlighting the need for further taxonomic research, species identification and broader field sampling to fully understand the diversity and ecological roles of these invertebrates. This study provides a valuable baseline for future studies contributing to wetlands conservation efforts and sustainable management in this biodiverse but vulnerable region.

Cytheridella whitmani Martens, sp. nov. is described from lakes on Cape Cod (MA, USA). The species differs from its congeners mainly by the shape of the female carapace and by the morphology of the hemipenis, especially of the distal lobe and the copulatory process. The literature on the genus is reviewed and the synonymy of the fossil Cytheridella boldii Purper, 1974 with the type species C. ilosvayi Daday, 1905, both described from South America, is confirmed. The status of Cytheridella americana (Furtos, 1936) is reverted to that of “uncertain species”. Beside the type species and the new species, the genus currently includes only three further species from Africa: C. monodi Klie, 1936, C. damasi Klie, 1944 (with synonym C. chariessa Rome, 1977), and C. tepida Victor, 1987. The morphology of the new species is discussed in comparison with the congeneric species, especially regarding the valve ornamentation, the structure and function of the third thoracopod, the hemipenis and the caudal ramus. It is suggested that C. whitmani is a recent invasive species in the lakes of the Cape Cod peninsula. Its occurrence at northern latitudes is unexpected, as its congeneric species are consistently (sub-) tropical.

The New Caledonian Archipelago is a hot spot for biodiversity and endemism. Here, we report on new records of nine species from localities on the main island, Grande Terre, and illustrate these: Ilyodromus viridulus (Brady, 1886), Stenocypris hislopi Ferguson, 1969, S. macedonica Petkovski & Meisch, 1996¸ S. malayica Victor & Fernando, 1981, Bradleytriebella lineata (Victor & Fernando, 1981), Hemicypris pyxidata (Moniez, 1892), Heterocypris incongruens (Ramdohr, 1808), Cypridopis vidua (O.F. Müller, 1776) and Limnocythere stationis Vávra, 1891. We also provide redescriptions and illustrations of the valves and carapace of Stenocypris marginata Daday, 1910 sensu Méhes, 1939, Cypris granulata Daday, 1898 and Kennethia major (Méhes, 1939); for the latter species also including some soft parts. Therefore, twenty two certain species have thus far been reported from the New Caledonian Archipelago. The status of seven uncertain species is also discussed. Previous records of Stenocypris major (Baird, 1859) from Grande Terre, mainly by Méhes, are here considered to belong to S. hislopi. We propose to reject the presence of Cyprinotus cingalensis Brady, 1886 in New Caledonia and suggest to consider Cypridopsis sarasini Méhes, 1939 as an “uncertain species” (sensu Meisch et al. 2019). We also argue that Eucypris wolffhuegeli Méhes, 1914 might be a synonym of H. incongruens and suggest that Strandesia rouxi Méhes, 1939 might be considered a junior synonym of an existing species, pending further research.