Delayed response to environmental conditions and infra-seasonal dynamics of the short-beaked common dolphin distribution.

Cetaceans adjust their distribution and abundance to encountered conditions across years and seasons, but we poorly understand such small-scale changes for many species, especially in winter. Crucial challenges confront some populations during this season, such as the high levels of fisheries-induced mortality faced by the common dolphin (Delphinus delphis) in the Northeast Atlantic shelves. For such species, understanding the winter fine-scale dynamics is crucial. We aimed to identify the dolphin distribution drivers during the winters of 2020 and 2021, with a focus on determining the lag between changes in oceanographic conditions and dolphin distribution. The changes were related to temporal delays specific to the nature and cascading effects that oceanographic processes had on the trophic chain. By determining the most important conditions and lags to dolphin distributions, we shed light on the poorly understood intrusions of dolphins within coastal waters during winter: they displayed a strong preference for the coastal-shelf waters front and extensively followed its spatial variations, with their overall densities increasing over the period and peaking in March-April. The results presented here provide invaluable information on the winter distribution dynamics and should inform management decisions to help reduce the unsustainable mortalities of this species in the by-catch of fisheries.

Setting the scene for Mediterranean litterscape management: The first basin-scale quantification and mapping of floating marine debris.

Plastic pollution has become one of the biggest environmental concerns of the Anthropocene as it represents a major threat to both wildlife and human health. Garbage patches in the world's oceans are well documented, but quantitative assessments of floating debris are still lacking in some major areas. The Mediterranean Sea is one such area, despite being one of the most plastic polluted environments. We used data from the first international basin-scale survey of the Mediterranean Sea to provide the first abundance estimate of floating mega-debris (>30 cm) and map their distribution over the entire Mediterranean Sea. We estimated the total number of floating mega-debris at 2.9 million items, taking into account imperfect detection. Items larger than 30 cm represent only one fourth of the complete load of anthropogenic debris (>2 cm) in the Mediterranean, which scales up the estimate to 11.5 million floating debris. The highest densities were observed in the central Mediterranean, and the lowest in the eastern basin. This acute marine pollution might threaten to disrupt entire ecosystems through its impact on marine fauna (entanglement, ingestion, contamination), eventually impacting the tourism industry and the well-being of Mediterranean populations.

The effect of a multi-target protocol on cetacean detection and abundance estimation in aerial surveys.

A double-platform protocol was implemented in the Bay of Biscay and English Channel during the SCANS-III survey (2016). Two observation platforms using different protocols were operating on board a single aircraft: the reference platform (Scans), targeting cetaceans, and the 'Megafauna' platform, recording all the marine fauna visible at the sea surface (jellyfish to seabirds). We tested for a potential bias in small cetacean detection and density estimation when recording all marine fauna. At a small temporal scale (30 s, roughly 1.5 km), our results provided overall similar perception probabilities for both platforms. Small cetacean perception was higher following the detection of another cetacean within the previous 30 s in both platforms. The only prior target that decreased small cetacean perception during the subsequent 30 s was seabirds, in the Megafauna platform. However, at a larger scale (study area), this small-scale perception bias had no effect on the density estimates, which were similar for the two protocols. As a result, there was no evidence of lower performance regarding small cetacean population monitoring for the multi-target protocol in our study area. Because our study area was characterized by moderate cetacean densities and small spatial overlap of cetaceans and seabirds, any extrapolation to other areas or time requires caution. Nonetheless, by permitting the collection of cost-effective quantitative data for marine fauna, anthropogenic activities and marine litter at the sea surface, the multi-target protocol is valuable for optimizing logistical and financial resources to efficiently monitor biodiversity and study community ecology.

Selection for increased body length in Subantarctic fur seals on Amsterdam Island.

The traditional distinction between ecological and evolutionary times is eroding, calling for tighter links between ecology and evolution. An example of such a brigde between the two disciplines is the so-called 'animal model', a methodology initially developed by animal breeders, which has become very popular among ecologists studying contemporary microevolution. Using a Bayesian multi-trait 'animal model', we investigated the quantitative genetics of body size, a fitness-related trait, in Subantarctic fur seals (Arctocephalus tropicalis) breeding on Amsterdam Island, Southern Ocean. Our approach jointly modelled the growth and selection processes at work in this population. Body length is heritable for both sexes, and females are under selection for increased body length in this population. We strongly suspect the peculiar ecological context of impoverished, suitable prey availability exacerbated by density-dependence phenomena to be an important selective agent on females breeding on Amsterdam Island.

Plasma lipoproteins of leukemic guinea pigs (L2C) can regulate cholesterol biosynthesis by lymphocytes of normal guinea pigs. A comparative study of plasma lipoproteins of normal and neoplastic animals.

The defect of regulation of cholesterol biosynthesis by leukemic (L2C) guinea pig lymphocytes is not a consequence of serum lipoprotein modifications which would make them unable to participate in the regulatory process. Low density lipoprotein of leukemic animals, in parallel to normal low density lipoprotein, can inhibit the cholesterol biosynthesis by normal cells. Surprisingly, very low density lipoprotein of leukemic animals have the same inhibitory property. Analyses of serum of leukemic animals showed a larger amount of the different lipoprotein fractions (+323% very low density, +27% low density lipoproteins, the high density lipoprotein staying undetectable in control and leukemic sera) than in normal serum. L2C leukemia produces low density lipoprotein slightly richer in unesterified cholesterol and very low density lipoprotein markedly modified by an increased proportion of unesterified cholesterol, phospholipids and apoprotein B. The inhibitory power of leukemic very low density lipoprotein is discussed by analogy with corresponding power of normal low density lipoprotein which can operate either by the way of binding to the low density lipoprotein receptor or by exchange of unesterified cholesterol between the lipoprotein and the cell.

[Solubilization and purification of Na+-K+ ATPase of human erythrocyte mambranes using sodium deoxycholate]. / Solubilisation et purification de l'ATPase (Na+-K+) de la membrane des erythrocytes humains sous l'action du déoxycholate de sodium

The (Na+-K+)-dependant ATPase prepared from human erythrocyte ghosts has been purified with sodium deoxycholate in a high ionic medium. After the purification, 60% of the native activity bound to the membranes was recovered.