As a result of processing materials from the expeditions Saint-Petersburg State University in 2012–2013 and Transarctic expedition 2019, 131 polychaete taxa were recorded, which 124 identified to species. On basis data previous recent collections, general list polychaetes Kara Sea was updated; it includes 209 species belonging 98 genera, 37 families, 15 orders. The following are reported for fi...

Wiwaxiids are a problematic group of scale-covered lophotrochozoans known from Cambrian Stages 3-5. Their imbricating dorsal scleritome of leaf-like scales has prompted comparison with various annelids and molluscs, and has been used as a template to reconstruct the articulation pattern of isolated Small Shelly Fossils. The first articulated specimens of Wiwaxia from the Cambrian Stage 3 Chengj...

In recent years it has become evident that many marine invertebrates are sensitive to changes in hydrostatic pressure, and the subject has recently been reviewed by Knight-Jones & Morgan (1966). Most are planktonic forms, and their responses appear to be of a depth-regulatory nature (Baylor & Smith, 1957; Moore & Corwin, 1956). However, a few normally benthic types have also been shown to be pr...

Annelids, unlike their vertebrate or fruit fly cousins, are a bilaterian taxon often overlooked when addressing the question of body plan evolution. However, recent data suggest that annelids offer unique insights on the early evolution of spiral cleavage, anteroposterior axis formation, body axis segmentation, and head versus trunk distinction.

As Denes et al. (2007) reveal in this issue, the expression profile and roles of genes that pattern the nervous system in embryos of chordates and annelids are surprisingly similar. This extraordinary conservation suggests that the patterning mechanism has been inherited largely unchanged from the bilaterian common ancestor and that the central nervous system, although dorsal in fish and ventra...