Mysterious bio-duck sound attributed to the Antarctic minke whale (Balaenoptera bonaerensis)

For decades, the bio-duck sound has been recorded in the Southern Ocean, but the animal producing it has remained a mystery. Heard mainly during austral winter in the Southern Ocean, this ubiquitous sound has been recorded in Antarctic waters and contemporaneously off the Australian west coast. Here, we present conclusive evidence that the bio-duck sound is produced by Antarctic minke whales (Balaenoptera bonaerensis). We analysed data from multi-sensor acoustic recording tags that included intense bio-duck sounds as well as singular downsweeps that have previously been attributed to this species. This finding allows the interpretation of a wealth of long-term acoustic recordings for this previously acoustically concealed species, which will improve our understanding of the distribution, abundance and behaviour of Antarctic minke whales. This is critical information for a species that inhabits a difficult to access sea-ice environment that is changing rapidly in some regions and has been the subject of contentious lethal sampling efforts and ongoing international legal action.     

Recurrent Pseudo-nitzschia calliantha (Bacillariophyceae) and Alexandrium insuetum (Dinophyceae) winter blooms induced by agricultural runoff

A winter bloom dominated by Pseudo-nitzschia calliantha Lundholm, Moestrup et Hasle (Bacillariophyceae), a potential domoic acid producer, is reported for the first time in the Aegean Sea, Greece, in a semi-enclosed embayment (Kalloni Gulf) surrounded by agricultural land and drained by intermittent rivers. Abundances of this species in the inner part of the Gulf during February were extremely high (max 1.1 × 10⁷ cells l⁻¹). The species Alexandrium insuetum Balech (Dinophyceae) was also found in considerable cell numbers (max 1.4 × 10⁵ cells l⁻¹) during the bloom and reached up to 40% of the total biovolume. This study demonstrates an evident cause and effect relationship between nutrient inflows originating from agricultural activities in the watershed and the development of a potential HAB. The massive bloom formation was observed soon after an episodic rainfall event during the fertilizer application period (December to February). A bloom was also observed the following year, but it was less pronounced due to the fact that rainfalls were more evenly spaced in time and were of moderate intensity.     

Quorum Sensing Peptides Selectively Penetrate the Blood-Brain Barrier

Bacteria communicate with each other by the use of signaling molecules, a process called ‘quorum sensing’. One group of quorum sensing molecules includes the oligopeptides, which are mainly produced by Gram-positive bacteria. Recently, these quorum sensing peptides were found to biologically influence mammalian cells, promoting i.a. metastasis of cancer cells. Moreover, it was found that bacteria can influence different central nervous system related disorders as well, e.g. anxiety, depression and autism. Research currently focuses on the role of bacterial metabolites in this bacteria-brain interaction, with the role of the quorum sensing peptides not yet known. Here, three chemically diverse quorum sensing peptides were investigated for their brain influx (multiple time regression technique) and efflux properties in an in vivo mouse model (ICR-CD-1) to determine blood-brain transfer properties: PhrCACET1 demonstrated comparatively a very high initial influx into the mouse brain (K_in = 20.87 μl/(g×min)), while brain penetrabilities of BIP-2 and PhrANTH2 were found to be low (K_in = 2.68 μl/(g×min)) and very low (K_in = 0.18 μl/(g×min)), respectively. All three quorum sensing peptides were metabolically stable in plasma (in vitro) during the experimental time frame and no significant brain efflux was observed. Initial tissue distribution data showed remarkably high liver accumulation of BIP-2 as well. Our results thus support the potential role of some quorum sensing peptides in different neurological disorders, thereby enlarging our knowledge about the microbiome-brain axis.     

Relation between endurance time and maximal oxygen consumption during supramaximal running

The relationship between speed and the maximal length of time supramaximal runs can be sustained (temps-limite, tlim) has been studied in seven male subjects (physical education students). Within the range of intensity studied, tlim strictly depends on maximal oxygen consumption (VO2max). The relationship between tlim and the relative energy cost of the exercises per unit of time (E), calculated by subtracting the maximal power of aerobic metabolism (Emaxox) from E, removes the interindividual differences of tlim. The function tlim = f(E-Emaxox) is described by an empirical equation of the form: tlim = a.exp[-b(E-Emaxox)] (r = 0.979; P less than 0.001), where the parameters a and b are respectively equal to 330.8 and 0.14 and where tlim, E and Emaxox are respectively expressed in seconds and in watts per kg of body weight.     

Age and sex composition of small ruminants at Nouakchott markets, Mauritania

A survey of species, breeds, sex and age composition of sheep and goats offered for sale was made at Nouakchott (Mauritania) livestock markets. Some 82.8% of animals presented at the markets were sheep and 95% of these were of the Short-haired Maure breed, the remainder being Long-haired Maure. Goats of the Sahel breed comprised 81% of all animals of this species, the others being Sahara and Eastern Dwarf types, but goats represented only 17.2% of all animals brought to market. Castrated Short-haired Maure sheep were 63.6% of this breed whereas castrates of Long-haired Maure sheep were 40.6% of the total. There were significantly more castrates than entire males presented for sale for sheep but the reverse was the case for goats. Entire males of both species were sold at younger ages than castrates and males and castrates combined were sold at younger ages than females. This study has provided some indications of the types of stock offered for sale but further studies at peak sale times would allow more detailed analysis. Such an analysis should be coupled with a survey of owners/herders and of traders in order to determine the factors operating on market forces.     

Cardiovascular changes induced by isometric exercise in aged subjects

Blood pressure and heart rate during static contraction of forearm muscles holding a tension of 30% maximal voluntary strength for 5 mn have been measured. Eleven young men and 11 elderly male subjects were used. Maximal voluntary strength is reduced by 19% in elderly subjects. Relative mean cardio-vascular responses were unaffected by age.     

Electric activity of the rectus femoris in supramaximal running

The electrical activity of the rectus femoris has been analysed in nine subjects during the course of a supramaximal run performed until exhaustion. The integrated electromyogram and the median frequency do not change significantly as a function of time.     

Century‐long apparent decrease in intrinsic water‐use efficiency with no evidence of progressive nutrient limitation in African tropical forests

Forests exhibit leaf‐ and ecosystem‐level responses to environmental changes. Specifically, rising carbon dioxide (CO₂) levels over the past century are expected to have increased the intrinsic water‐use efficiency (iWUE) of tropical trees while the ecosystem is gradually pushed into progressive nutrient limitation. Due to the long‐term character of these changes, however, observational datasets to validate both paradigms are limited in space and time. In this study, we used a unique herbarium record to go back nearly a century and show that despite the rise in CO₂ concentrations, iWUE has decreased in central African tropical trees in the Congo Basin. Although we find evidence that points to leaf‐level adaptation to increasing CO₂—that is, increasing photosynthesis‐related nutrients and decreasing maximum stomatal conductance, a decrease in leaf δ¹³C clearly indicates a decreasing iWUE over time. Additionally, the stoichiometric carbon to nitrogen and nitrogen to phosphorus ratios in the leaves show no sign of progressive nutrient limitation as they have remained constant since 1938, which suggests that nutrients have not increasingly limited productivity in this biome. Altogether, the data suggest that other environmental factors, such as increasing temperature, might have negatively affected net photosynthesis and consequently downregulated the iWUE. Results from this study reveal that the second largest tropical forest on Earth has responded differently to recent environmental changes than expected, highlighting the need for further on‐ground monitoring in the Congo Basin.