Multi-Partner Urochordate Chimeras Outperform Two-Partner Chimerical Entities

Environmental split between germ cell parasitism and somatic cell synergism in chimeras of a colonial urochordate

“…Colonies were divided into several subclones at least one month before their use. Subclones from each colony were acclimated to temperature changes (15°C, 25°C) for one month and then paired with similar-sized subclones of the compatible partner and placed on glass slides fitted within glass racks (Rinkevich et al, 1993;Pancer et al, 1995;Rinkevich and Shapira, 1999). Fusions were established within 48-72·h after first ampulla-to-ampulla contacts.…”

“…Chimeras from a variety of protists, plants and animals are documented in nature (Buss, 1982). Several studies (Buss, 1982;Weissman, 1987b, 1992;Rinkevich and Shapira, 1999) have dealt with the evolutionary significance of chimerism by evaluating fitness costs and benefits of the chimeral entity, relative to the state of genetically homogeneous individuals. Of all the different suggested classes of benefits for chimerism (none has been recorded in organisms more developed than primitive slime molds and algae; Rinkevich and Shapira, 1999), one has focused on the possible synergistic impact of both partners' genetic constituents on the chimeric fitness (Rinkevich and Weissman, 1987a;Rinkevich and Shapira, 1999).…”

“…Several studies (Buss, 1982;Weissman, 1987b, 1992;Rinkevich and Shapira, 1999) have dealt with the evolutionary significance of chimerism by evaluating fitness costs and benefits of the chimeral entity, relative to the state of genetically homogeneous individuals. Of all the different suggested classes of benefits for chimerism (none has been recorded in organisms more developed than primitive slime molds and algae; Rinkevich and Shapira, 1999), one has focused on the possible synergistic impact of both partners' genetic constituents on the chimeric fitness (Rinkevich and Weissman, 1987a;Rinkevich and Shapira, 1999). It was suggested (Buss, 1982) that since a chimera has a greater store of genetic variability, and hence a wider range of effective physiological qualities and characteristics, this organismic state may tolerate a greater range of environmental variation than the organismic state of genetically homogeneous entity.…”

“…It should also be taken into consideration that, while intraspecific interactions within chimeras go on, larger botryllid chimeras successfully control feeding substrates. This should effectively prevent colonization of that surface area by other competitive species and/or may increase interspecific competitive abilities (Rinkevich and Shapira, 1999).…”

“…Several studies (Buss, 1982;Grosberg and Quinn, 1986;Rinkevich and Weissman, 1992;Rinkevich and Shapira, 1999;Rinkevich, 2002) were set up to define the evolutionary significance of natural chimeras by evaluating the fitness costs and benefits of chimerism as compared with the state of genetically homogeneous entities or by analysing bi-vs-multipartner chimeras. No definite benefit was recorded in the kingdom Animalia for any case of chimerism.…”