From limb to fin: an Eocene protocetid forelimb from Senegal sheds new light on the early locomotor evolution of cetaceans

Cetaceans constitute a textbook example of the secondary adaptation of tetrapods to aquatic life. This major event in the evolutionary history of mammals is often linked in the literature to the limb-to-fin transition. Paradoxically, limb bones are scarce in the fossil record of early cetaceans, and the transition from a limb-adapted morphology for an amphibious life in shallow water to a fin-adapted morphology for a pelagic lifestyle remains poorly documented. Here, we describe new protocetid remains from the upper Lutetian of Senegal, including a nearly complete articulated forelimb. A cladistic analysis including 24 taxa and 137 morphological characters recovers the new African specimen close to Carolinacetus. It also confirms that cetacean dispersal to the New World was not the result of a single colonization event. A 3D model of the forelimb was reconstructed. Anatomical comparisons suggest that it is unlikely that the Senegalese forelimb was used as a rigid pectoral flipper for steering as in basilosaurids and modern cetaceans. Instead, we suggest that the hand was actively used during swimming. This challenges previous reconstructions of protocetids as mainly foot-powered swimmers, and suggests that swimming specializations of early cetaceans were probably more diverse than previously considered.     

Early Development of the Sofie, Chondrostoma toxostoma

The developmental biology of embryos, larvae and juveniles of sofie, Chondrostoma toxostoma, reared from artificial insemination, was examined under controlled laboratory conditions, using both in-vivo and preserved specimens. The complete remodelling process (metamorphosis) was described and interpreted according to the theory of saltatory ontogeny, providing a model within which the highly complex ecological niche and behaviour (habitat use, diet, etc.) of the free embryos and larvae can be evaluated. The sofie ova were relatively opaque and the free embryos presented a small yolksac. Consequently, the free embryo steps were short and the free embryos emerged rapidly from the substratum. The circulatory system appeared early and was simple, which suggests that sofie free embryos require well oxygenated water. The remodelling of the mouth from a superior to inferior position characterised changes in the sofie's diet during early life history, which is typical of the genus. Differences in development relative to the nase, C. naus, are discussed.     

Current distribution and potential expansion of the harmful benthic dinoflagellate Ostreopsis cf. siamensis towards the warming waters of the Bay of Biscay,North-East Atlantic

In a future scenario of increasing temperatures in North-Atlantic waters, the risk associated with the expansion of the harmful, benthic dinoflagellate Ostreopsis cf. siamensis has to be evaluated and monitored. Microscopy observations and spatio-temporal surveys of environmental DNA (eDNA) were associated with Lagrangian particle dispersal simulations to: (i) establish the current colonization of the species in the Bay of Biscay, (ii) assess the spatial connectivity among sampling zones that explain this distribution, and (iii) identify the sentinel zones to monitor future expansion. Throughout a sampling campaign carried out in August to September 2018, microscope analysis showed that the species develops in the south-east of the bay where optimal temperatures foster blooms. Quantitative PCR analyses revealed its presence across almost the whole bay to the western English Channel. An eDNA time-series collected on plastic samplers showed that the species occurs in the bay from April to September. Due to the water circulation, colonization of the whole bay from the southern blooming zones is explained by inter-site connectivity. Key areas in the middle of the bay permit continuous dispersal connectivity towards the north. These key areas are proposed as sentinel zones to monitor O. cf. siamensis invasions towards the presumably warming water of the North-East Atlantic.     

Occurrence of somaclonal variation among somatic embryo-derived white spruces (Picea glauca,Pinaceae)

Four different variegata phenotypes were identified among 2270 white spruce plants [Picea glauca (Moench.) Voss.] produced over a period of 2 yr from the time of induction of embryogenic tissues. The four variegated plants differed from each other in the extent and distribution of chlorophyll-deficient needles. Light microscopy showed that variegated leaves of a selected variant consisted of a chimeral mixture of green and white cells. Electron microscopy showed that cells in completely white needles had large nuclei with predominant euchromatin, lacked large cytoplasmic vacuoles, and harbored vacuolized plastids with aberrant morphologies. Various observations suggest that the recovered variegata phenotypes reflect some kind of genetic instability of either chloroplastic or nuclear genomes. To elucidate the genetic basis of these variegata phenotypes in white spruce, three out of the four variants were subjected to randomly amplified polymorphic DNA (RAPD) analysis. Out of more than 250 RAPD markers screened, only one correlated with white needles of variegated plants. The nucleotide sequence of this DNA fragment showed no homology with any known gene, but the amplified sequence appears most likely of nuclear origin.     

Enamel microstructure evolution in anthracotheres (Mammalia,Cetartiodactyla) and new insights on hippopotamoid phylogeny

Investigations on enamel microstructure provided new data for the debate on hippopotamid origin. Observations indicated a diversity of patterns relevant to phylogenetic inferences. Within Hippopotamoidea, the distribution of these patterns seems to be in favour of a hippopotamid origin within the Palaeogene African anthracotheres. Enamel microcharacters therefore prove to be particularly relevant for future phylogenetic analysis of the superfamily, and have implications for our understanding of ecological transitions within hippopotamoids at the end of the Miocene. Indeed, unlike equids or bovids, which developed grass feeding thanks to their hypsodont molars, hippopotamoids may have had another way to exploit this resource. The combination of inter‐row sheets, which appeared early in the evolutionary history of the group, and the increased thickness of radial enamel could have eased the consumption of highly abrasive graminoids. © 2014 The Linnean Society of London     

ETH 6022: an artificial enzyme? A comparison between enzymatic and chemical recognition for sensing ethanol

Routinely the quantification of ethanol in clinical chemistry and food chemistry is performed by enzymatic methods in addition to chemical methods. Liver and yeast alcohol:NAD⁺ oxidoreductase (ADH, EC. 1.1.1.1) and alcohol oxidase AOD (EC 1.1.3.13) are mainly applied for selective evaluations by different kinds of bioassay. Nevertheless, drawbacks of ethanol sensing make the evaluation of ethanol concentrations in alcoholic beverages by an optical sensor, in a concentration range between 0·7% and 40%, most attractive. The chemical recognition process is based on a lipophilic amide of trifluoroacetylaniline (ETH 6022) as a ligand for ethanol implanted in a solvent polymeric membrane. The interaction leads to a hypsochromic shift of the absorption band in the ultraviolet region (305 nm). The chemical reaction in the apolar environment of the optode membrane is reversible. The principle of this recognition process is compared to the enzymatic reaction of ADH. In both cases a highly electrophilic centre participates in the interaction between the hydroxy group of the alcohol and the ligand. The selectivity behaviour of the artificial recognition process may be tailored by the substituents of the aromatic trifluoroacetyl compound. The response characteristics of the optochemical sensors are compared.