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Summary Coccolithophores are an ideal test group for investigating fine-scale differentiation within the phytoplankton since their taxonomy is rather well-documented and their biomineralised periplasts – the coccoliths – provide a rich suite of qualitative and quantitative morphological characters and a uniquely extensive fossil record. In addition, extant coccolithophore species can be grown in culture...
Summary Most haptophytes are unicellular, photosynthetic flagellates, although some have coccoid, colonial, amoeboid or filamentous stages. Nearly all have a characteristic filamentous appendage, the haptonema, arising between the two flagella. We have amassed small subunit rRNA gene sequences (18S rDNA) from 125 haptophytes and aligned the sequences with those of over 300 published and unpublished...
Summary Multidisciplinary research on the cosmopolitan coccolithophore species Calcidiscus leptoporus within the CODENET research project has revealed that it is composed of at least two separate species (Calcidiscus leptoporus and Calcidiscus quadriperforatus), characterized by differences in their coccolith morphology, life cycle, distribution, ecology and molecular genetics. This situation, which...
Summary The most successful groups of pelagic protists in the modern Ocean have evolved convergent phenotypic traits, including the presence of hard skeletons enclosing the cell. These micro-skeletons – tests, coccoliths, frustules, theca – have accumulated kilometers of deep-sea sediments since the Jurassic, the most complete and continuous fossil record widely used for reconstructing Earth systems...
Thioredoxins are a class of evolutionarily conserved proteins that have been demonstrated to play a key role in many cellular processes involving redox reactions. We report here the genetic and biochemical characterization of Caenorhabditis elegans TRX-3, the first metazoan thioredoxin with an intestine-specific expression pattern. By using green fluorescent protein reporters we have found that TRX-3...
The Na/K pump, or Na,K-ATPase, is a key enzyme to the homeostasis of osmotic pressure, cell volume, and the maintenance of electrochemical gradients. Its α subunit, which holds most of its functions, belongs to a large family of ATPases known as P-type, and to the subfamily IIC, which also includes H,K-ATPases. In this study, we attempt to describe the evolutionary history of IIC ATPases by doing...
Some animals, such as the larvae of Drosophila melanogaster, the larvae of the Appendicularian chordate Oikopleura, and the adults of the nematode Caenorhabditis elegans, are unusual in that they grow largely by increases in cell size [1–3]. The giant cells of such species are highly polyploid, having undergone repeated rounds of endoreduplication [1, 2, 4–7]. Since germline polyploid strains tend...
We have examined the patterns of polymorphism at two linked loci, Sod and Est-6, separated by nearly 1000 kb on the left arm of chromosome 3 of Drosophila melanogaster. The evidence suggests that natural selection has been involved in shaping the polymorphisms. At the Sod locus, a fairly strong (s>0.01) selective sweep, started ≥2600 years ago, increased the frequency of a rare haplotype, F(A),...
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