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.     

Widespread formation of intracellular calcium carbonates by the bloom-forming cyanobacterium Microcystis

The formation of intracellular amorphous calcium carbonates (iACC) has been recently observed in a few cultured strains of Microcystis, a potentially toxic bloom-forming cyanobacterium found worldwide in freshwater ecosystems. If iACC-forming Microcystis are abundant within blooms, they may represent a significant amount of particulate Ca. Here, we investigate the significance of iACC biomineralization by Microcystis. First, the presence of iACC-forming Microcystis cells has been detected in several eutrophic lakes, indicating that this phenomenon occurs under environmental conditions. Second, some genotypic (presence/absence of ccyA, a marker gene of iACC biomineralization) and phenotypic (presence/absence of iACC) diversity have been detected within a collection of strains isolated from one single lake. This illustrates that this trait is frequent but also variable within Microcystis even at a single locality. Finally, one-third of publicly available genomes of Microcystis were shown to contain the ccyA gene, revealing a wide geographic and phylogenetic distribution within the genus. Overall, the present work shows that the formation of iACC by Microcystis is common under environmental conditions. While its biological function remains undetermined, this process should be further considered regarding the biology of Microcystis and implications on the Ca geochemical cycle in freshwater environments.     

POPULATION STRUCTURE IN AN INSHORE CETACEAN REVEALED BY MICROSATELLITE AND mtDNA ANALYSIS: BOTTLENOSE DOLPHINS (TURSIOPS SP.) IN SHARK BAY, WESTERN AUSTRALIA

We examined population substructure of bottlenose dolphins ( Tursiops sp). in Shark Bay, Western Australia, using 10 highly polymorphic microsatellite loci, and mitochondrial DNA (mtDNA). For microsatellite analysis, 302 different animals were sampled from seven localities throughout the bay. Analysis of genetic differentiation between sampling localities showed a significant correlation between the number of migrants ( Nm ) calculated from F _ST, R _ST and private alleles, and distance between localities–a pattern of isolation-by-distance. For mtDNA, 220 individuals from all seven localities were sequenced for a 351 base pair fragment of the control region, resulting in eight haplotypes, with two distinct clusters of haplotypes. Values of F _ST and (φ)_ST for mtDNA yielded statistically significant differences, mostly between localities that were not adjacent to each other, suggesting female gene flow over a scale larger than the sampled localities. We also observed a significant correlation between the number of female migrants calculated from F _ST and φ_ST and the distance of sampling localities. Our results indicate that dispersal in female dolphins in Shark Bay is more restricted than that of males.     

Bioecological Drivers of Rabies Virus Circulation in a Neotropical Bat Community

Introduction

In addition to the commonly accepted importance of the vampire bat in the maintenance and transmission of the rabies virus (RABV) in South America, RABV infection of other species is widely evidenced, challenging their role in the viral cycle.

Methodology / Principles findings

To identify the bioecological drivers of RABV circulation in neotropical bat communities, we conducted a molecular and serological survey on almost 1,000 bats from 30 species, and a 4-year longitudinal survey in two colonies of vampire bats in French Guiana. RABV was molecularly detected in a common vampire and in a frugivorous bat. The sequences corresponded to haematophagous bat-related strains and were close to viruses circulating in the Brazilian Amazon region. Species’ seroprevalence ranged from 0 to 20%, and the risk of seropositivity was higher in bats with a haematophagous diet, living in monospecific colonies and in dense forests. The longitudinal survey showed substantial temporal fluctuations, with individual waves of seroconversions and waning immunity. The high prevalences observed in bat communities, in most habitats and in species that do not share the same microhabitats and bioecological patterns, the temporal variations, and a rather short period of detectable antibodies as observed in recaptured vampires suggest (i) frequent exposure of animals, (ii) an ability of the infected host to control and eliminate the virus, (iii) more relaxed modes of exposure between bats than the commonly assumed infection via direct contact with saliva of infected animals, all of which should be further investigated.

Conclusions / significance

We hypothesize that RABV circulation in French Guiana is mainly maintained in the pristine forest habitats that may provide sufficient food resources to allow vampire bats, the main prevalent species, to survive and RABV to be propagated. However, on the forest edge and in disturbed areas, human activities may induce more insidious effects such as defaunation. One of the ecological consequences is the disappearance of resources for tertiary or secondary consumers. Populations of vampires may then shift to alternative resources such as cattle, domestic animals and humans. Therefore, a good forest status, allowing both a dilution effect in highly rich bat communities and the maintenance of large populations of medium-sized and large mammals used as prey by vampires, should prevent their migration to anthropized areas.     

Space Use and Movement Patterns in a Semi-Free-Ranging Herd of European Bison (Bison bonasus)

The successful reintroduction and restocking of the European Bison demands a reliable knowledge of the biology of this species. Yet little is known to date about the European bison, and empirical data remains insufficient to set up a reliable plan ensuring the reintroduction, maintenance and survival of populations in habitats that have been largely modified by human activity. Studies of the ecology, social behaviour and management of bison are therefore crucial to the conservation of this species and its cohabitation with humans. To meet these challenges, we focused on movement patterns and space use in a semi-free-ranging herd of European bison living in the Réserve Biologique des Monts-d’Azur (France). Bison spend over 80% of their time foraging and resting; foraging mainly occurs around the artificial feeding sites (i.e., hay racks) or in meadows. The time of day and the presence of snow have no influence on the time budget allocated to each activity. Animals, however, spend more time at the food racks in winter. Bison also spend most of their time in small groups of individuals, confirming the occurrence of both fission-fusion dynamics and sexual segregation in this species. Bison seem to follow a Lévy walk pattern of movement, which is probably related to the geographical distribution and size of food patches in the reserve. The conclusions of this study provide a better understanding of the sociality, life habits and habitat use of bison, and also describe how the provision of hay affects all these behaviours. These results could be useful in the development of tools to select the most suitable habitats for the reintroduction, management and conservation of bison populations.     

Two different specific JNK activators are required to trigger apoptosis or compensatory proliferation in response to Rbf1 in Drosophila

The Jun Kinase (JNK) signaling pathway responds to diverse stimuli by appropriate and specific cellular responses such as apoptosis, differentiation or proliferation. The mechanisms that mediate this specificity remain largely unknown. The core of this signaling pathway, composed of a JNK protein and a JNK kinase (JNKK), can be activated by various putative JNKK kinases (JNKKK) which are themselves downstream of different adaptor proteins. A proposed hypothesis is that the JNK pathway specific response lies in the combination of a JNKKK and an adaptor protein upstream of the JNKK. We previously showed that the Drosophila homolog of pRb (Rbf1) and a mutant form of Rbf1 (Rbf1^D253A) have JNK-dependent pro-apoptotic properties. Rbf1^D253A is also able to induce a JNK-dependent abnormal proliferation. Here, we show that Rbf1-induced apoptosis triggers proliferation which depends on the JNK pathway activation. Taking advantage of these phenotypes, we investigated the JNK signaling involved in either Rbf1-induced apoptosis or in proliferation in response to Rbf1-induced apoptosis. We demonstrated that 2 different JNK pathways involving different adaptor proteins and kinases are involved in Rbf1-apoptosis (i.e. Rac1-dTak1-dMekk1-JNK pathway) and in proliferation in response to Rbf1-induced apoptosis (i.e., dTRAF1-Slipper-JNK pathway). Using a transient induction of rbf1, we show that Rbf1-induced apoptosis activates a compensatory proliferation mechanism which also depends on Slipper and dTRAF1. Thus, these 2 proteins seem to be key players of compensatory proliferation in Drosophila.     

Time-Restricted Feeding Prevents Obesity and Metabolic Syndrome in Mice Lacking a Circadian Clock

1. Download high-res image (187KB)
2. Download full-size image