Pedomorphic morphogenesis in sea spiders (Pycnogonida) connected with introduction into the Arctic basin

Against the background of earlier known illustrations of pedomorphic evolution in different systematic groups of animals and plants, an example of a finding of sea spider individuals of the genus Achelia, which conserve a juvenile feature (pincers of cheliphores not reduced in ontogenesis), is studied. It is shown that Achelia borealis japonica is an initial form of Achelia borealis s.l., penetrated into northern seas of the Pacific Ocean, and formed there two subspecies with pedomorphic features of different developmental phases: Achelia borealis neotenica and Achelia borealis borealis. It is proposed to examine the high-latitude conditions of the seas of the Arctic basin with desalination of their surface waters and inconstancy of hydrological characteristics as a reason for pedomorphic speciation. © 2010, Pleiades Publishing, Ltd.