Anthropogenic CO₂-mediated freshwater acidification limits survival, calcification, metabolism, and behaviour in stress-tolerant freshwater crustaceans

Dissolution of anthropogenic CO2 is chronically acidifying aquatic ecosystems. Studies indicate that ocean acidification will cause marine life, especially calcifying species, to suffer at the organism and ecosystem levels. In comparison, freshwater acidification has received less attention, rendering its consequences unclear. Here, juvenile Chinese mitten crabs, Eriocheir sinensis, were used as a crustacean model to investigate the impact of CO2-mediated freshwater acidification. Our integrative approach, investigating changes in the animal's acid–base homeostasis, metabolism, calcification, locomotory behaviour, and survival rate, indicates that this economically relevant crustacean will face energetic consequences from future freshwater acidification. These energetic trade-offs allow the animal to maintain its acid–base homeostasis at the cost of reduced metabolic activity, exoskeletal calcification, and locomotion, reducing the animal's overall fitness and increasing its mortality. Results indicate that present-day Chinese mitten crab could be heavily affected by freshwater acidification like their marine counterparts and emphasize the importance of understanding the long-term implications of freshwater acidification on species' fitness.

Yellowfin Tuna Behavioural Ecology and Catchability in the South Atlantic: The Right Place at the Right Time (and Depth)

The yellowfin tuna (Thunnus albacares: YFT) is a widely distributed, migratory species that supports valuable commercial fisheries. Landings of YFT are seasonally and spatially variable, reflecting changes in their availability and accessibility to different fleets and metiers which, in turn, has implications for sustainable management. Understanding the dynamics of YFT behaviour and how it is affected by biological and ecological factors is therefore of consequence to fisheries management design. Archival and pop-up satellite tags (PSAT) were used in the South Atlantic Ocean around St Helena between 2015 and 2020 to collect information on the movements, foraging and locomotory behaviour of YFT. The study aimed to (1) identify vertical behaviour of YFT within St Helena’s EEZ; (2) assess the timing and depth of potential feeding events and (3) to use the information to inform on the catchability of YFT to the local pole and line fishing fleet. Results indicate that the YFT daytime behaviour shifted between shallow with high incidence of fast starts in surface waters in summer months (December to April), to deep with high incidence of strikes at depth in colder months (May to November). Catchability of YFT was significantly reduced between May and November as YFT spent more time at depths below 100 m during the day, which coincides with a reduction in the quantity of YFT caught by the inshore fleet.

Locomotory behaviour of early tetrapods from Blue Beach, Nova Scotia, revealed by novel microanatomical analysis

Evidence for terrestriality in early tetrapods is fundamentally contradictory. Fossil trackways attributed to early terrestrial tetrapods long predate the first body fossils from the Late Devonian. However, the Devonian body fossils demonstrate an obligatorily aquatic lifestyle. Complicating our understanding of the transition from water to land is a pronounced gap in the fossil record between the aquatic Devonian taxa and presumably terrestrial tetrapods from the later Early Carboniferous. Recent work suggests that an obligatorily aquatic habit persists much higher in the tetrapod tree than previously recognized. Here, we present independent microanatomical data of locomotor capability from the earliest Carboniferous of Blue Beach, Nova Scotia. The site preserves limb bones from taxa representative of Late Devonian to mid-Carboniferous faunas as well as a rich trackway record. Given that bone remodels in response to functional stresses including gravity and ground reaction forces, we analysed both the midshaft compactness profiles and trabecular anisotropy, the latter using a new whole bone approach. Our findings suggest that early tetrapods retained an aquatic lifestyle despite varied limb morphologies, prior to their emergence onto land. These results suggest that trackways attributed to early tetrapods be closely scrutinized for additional information regarding their creation conditions, and demand an expansion of sampling to better identify the first terrestrial tetrapods.

Anthropogenic CO₂-mediated freshwater acidification limits survival, calcification, metabolism, and behaviour in stress-tolerant freshwater crustaceans

Dissolution of anthropogenic CO2 is chronically acidifying aquatic ecosystems. Studies indicate that ocean acidification will cause marine life, especially calcifying species, to suffer at the organismal and ecosystem levels. In comparison, freshwater acidification has received less attention rendering its consequences unclear. Here, juvenile Chinese mitten crabs, Eriocheir sinensis, were used as a calcifying model to investigate the impacts of CO2-mediated freshwater acidification. Our integrative approach investigating changes in the animal's acid-base homeostasis, metabolism, calcification, locomotory behaviour, and survival rate indicate that the crab will face energetic consequences from future freshwater acidification. These energetic trade-offs allow the animal to maintain its acid-base homeostasis at the cost of reduced metabolic activity, exoskeletal calcification, and locomotion reducing the animal's overall fitness and increasing its mortality. Results suggest that present-day calcifying invertebrates could be heavily affected by freshwater acidification similar to their marine organisms and emphasizes the importance in understanding the long-term implications of freshwater acidification on species fitness.

Migrating lung monocytes internalize and inhibit growth of Aspergillus fumigatus conidia

Monocytes are important players to combat ubiquitously present fungus Aspergillus fumigatus. Recruitment of monocytes to sites of fungal infection was shown in vivo, and purified murine and human blood monocytes are able to induce inflammatory and fungicidal mediators as well as the host cell and the fungal transcriptional responses upon exposure to A.fumigatus. Mononuclear tissue phagocytes are phenotypically and functionally different from those circulating in the blood and their role in antifungal defences is much less understood.In this study, we identified a population of migrating CD43+ monocytes in cells isolated from rat distal lungs. These cells phenotypically different from alveolar macrophages, showed clearly distinct locomotory behaviour on the surface of primary alveolar cells resembling previously described endothelial patrolling. The CD43+ monocytes internalized live A.fumigatus conidia resulting in inhibition of conidial germination and hyphal growth. Thus, migrating lung monocytes might play an important role in local defence against pulmonary pathogens.

Toxicity of microplastic particles with and without adsorbed tributyltin (TBT) in Gammarus fossarum (Koch, 1835)

We investigate the toxicity of different types and sizes of microplastic particles (0.3–4 mm) under different conditions (new particles, aged particles with biofilm, and particles with adsorbed Tributyltin) on the freshwater amphipod Gammarus fossarum in 3-week exposures. All types of plastic particles, which were randomly taken up to a small extent, were mostly Polyphenylenoxide, Polybutylentherephthalate and Polypropylene, with particles < 1 mm in size. Plastic particles did not affect the feeding and locomotory behaviour of gammarids, and there was no strong difference between pristine plastic particles and aged particles with biofilm. Mortality tended to be higher compared with the control. Tributyltinhydride (TBTH) adsorbed to microplastic particles had no effect on uptake, survival, feeding and locomotory behaviour during the 3 weeks of exposure. Dissolved TBTH, however, was already very toxic after few days of exposure (LC50-96h < 1 ng l –1).