Postglacial expansion of the arctic keystone copepod calanus glacialis

Calanus glacialis, a major contributor to zooplankton biomass in the Arctic shelf seas, is a key link between primary production and higher trophic levels that may be sensitive to climate warming. The aim of this study was to explore genetic variation in contemporary populations of this species to infer possible changes during the Quaternary period, and to assess its population structure in both space and time. Calanus glacialis was sampled in the fjords of Spitsbergen (Hornsund and Kongsfjorden) in 2003, 2004, 2006, 2009 and 2012. The sequence of a mitochondrial marker, belonging to the ND5 gene, selected for the study was 1249 base pairs long and distinguished 75 unique haplotypes among 140 individuals that formed three main clades. There was no detectable pattern in the distribution of haplotypes by geographic distance or over time. Interestingly, a Bayesian skyline plot suggested that a 1000-fold increase in population size occurred approximately 10,000 years before present, suggesting a species expansion after the Last Glacial Maximum.GAME from the National Science Centre, the Polish Ministry of Science and Higher Education Iuventus Plus [IP2014 050573]; FCT-PT [CCMAR/Multi/04326/2013]; [2011/03/B/NZ8/02876

Productivity, pressure, and new perspectives: impacts of the COVID-19 pandemic on marine early-career researchers

The worldwide disruption caused by the beginning of the COVID-19 pandemic has dramatically impacted the activities of marine scientists working towards the goals of the UN Ocean Decade. As in other disciplines, marine early-career researchers (ECRs) are essential contributors to the development of novel and innovative science. Based on a survey of 322 of our peers, we show that the pandemic negatively impacted marine ECRs in ways that further exacerbate existing structural challenges such as social isolation, job insecurity, and short-term contracts, competitive funding, and work pressure. Furthermore, we find that the success and wellbeing of marine ECRs depends heavily on networking opportunities, gaining practical experience, collecting data, and producing publications, all of which were disrupted by the pandemic. Our analysis shows that those in the earliest stages of their careers feel most vulnerable to long-term career disadvantage as a result of the pandemic. This paper contributes to the empirical body of work about the impacts of the pandemic on marine science and offers recommendations on how marine ECRs should be supported to achieve the UN Ocean Decade’s goal of producing “the science we need for the ocean we want”

An unusual evolutionary strategy: the origins, genetic repertoire, and implications of doubly uniparental inheritance of mitochondrial DNA in bivalves

International audienceMitochondrial DNA (mtDNA) is typically passed on to progeny only by the female parent. The phenomenon of "doubly uniparental inheritance" (DUI) of mtDNA in many bivalve species is a fascinating exception to the paradigm of strict maternal inheritance of mtDNA. In this review, we survey the current state of knowledge of DUI, and discuss several active areas of research in this field. Topics/questions covered include: the number of times DUI evolved (once or multiple origins), the link between DUI and sex determination, the role(s) of mtDNA-encoded non-oxidative phosphorylation genes (i.e., ORFan/orf genes) in freshwater mussels, the function of conserved sequence motifs and sperm transmission elements in mtDNA of marine mussels, the challenges of annotating mtDNA genomes of DUI species, the presence of unorthodox features in venerid mtDNA, whether or not orf DNA sequences are useful in species-level identification of freshwater mussel, and finally, whether or not there are obvious benefits of DUI. For each topic we also highlight important avenues for future research within this fascinating field of mitochondrial evolutionary biology