Elvire Antajan

Biochemical survey of the polar head of plant glycosylinositolphosphoceramides unravels broad diversity

Although Glycosyl-Inositol-Phospho-Ceramides (GIPCs) are the main sphingolipids of plant tissues, they remain poorly characterized in term of structures. This lack of information, notably with regard to polar heads, currently hampers the understanding of GIPC functions in biological systems. This situation prompted us to undertake a large scale-analysis of plant GIPCs: 23 plant species chosen in various phylogenetic groups were surveyed for their total GIPC content. GIPCs were extracted and their polar heads were characterized by negative ion MALDI and ESI mass spectrometry. Our data shed light on an unexpected broad diversity of GIPC distributions within Plantae, and the occurrence of yet-unreported GIPC structures in green and red algae. In monocots, GIPCs with three saccharides were apparently found to be major, whereas a series with two saccharides was dominant in Eudicots within a few notable exceptions. In plant cell cultures, GIPC polar heads appeared to bear a higher number of glycan units than in the tissue from which they originate. Perspectives are discussed in term of GIPC metabolism diversity and function of these lipids.

Comparison of traditional microscopy and digitized image analysis to identify and delineate pelagic fish egg spatial distribution

One of the problems concerning studies of fish egg distribution is the weak spatial and temporal resolution due to the workload that examination of a large number of samples would demand. Recently, the development of a new laboratory imaging system, the ZooScan, capable of obtaining relatively good resolution images enables automated zooplankton identification using supervised learning algorithms. This new approach was applied to formalin-fixed fish egg samples collected during French winter IBTS (International Bottom Trawl Surveys) in the Eastern English Channel and the Southern North Sea. Fish egg spatial distributions of seven species based on the microscope and ZooScan identifications were compared. Abundance and distribution maps of winter-spawning areas of plaice, long rough dab, cod and whiting were similar for both methods. Low identification accuracy for small size eggs was due to microscope misidentification of standards used for the ZooScan learning (dab and flounder). The potential input of such a tool to quickly acquire valuable data on identification, enumeration, size frequency distribution of fish eggs and map spawning areas is of great interest for understanding and forecasting fisheries recruitment and will support ecosystem-based management.

Understanding winter distribution and transport pathways of the invasive ctenophore Mnemiopsis leidyi in the North Sea: coupling habitat and dispersal modelling approaches.

The invasive ctenophore Mnemiopsis leidyi has been reported in various coastal locations in the southern North Sea in the past years. Since 2009, International Bottom Trawl Surveys have recorded this species each winter in open waters. As this species, well-known for its dramatic disturbance of ecosystems, was expected not to be able to overwinter offshore it is crucial to understand its distribution dynamics. Two modelling methods, a quantile regression and a particle tracking model, were used (1) to identify habitats where the invasive ctenophore M. leidyi could survive the North Sea cold winters and (2) to investigate the dispersal of individuals between these different habitats, emphasizing favorable areas where sustainable populations could have been established. Temperature was found to be the crucial factor controlling the winter distribution of M. leidyi in the North Sea. High abundance predictions in winter were associated with low values of temperature, which characterise south-eastern coastal areas and estuaries influenced by riverine runoff. A retention-based M. leidyi population was indicated along the northern Dutch coast and German Bight and a transport-based population offshore from the western Danish coast. Individuals found in the open waters were transported from southern coasts of the North Sea, thus the open water population densities depend on the flux of offspring from these areas. This study provides the first estimates of the overwinter areas of this invasive species over the cold winters in the North Sea. Based on the agreement of habitat and dispersal model results, we conclude that M. leidyi has become established along south-eastern coasts of the North Sea where the environment conditions allows overwintering and it can be retained for later blooms.