Spectacular reproductive strategies in polychaetes

摘要

Generations of scientists have been fascinated and puzzled by the tremendous variability of reproductive strategies in the animal kingdom. This variability is on the one hand and to a large extent based on the limitations set by the biotic and abiotic conditions of the habitat to the animals in question. On the other hand, variability is the result of the evolutionary constraint on the reproductive effort of the species in question. Any reproducing animal invests a certain amount of its somatic resources into the production of gametes. Since gametes secure the transfer of genetic information to the following generation, a large number of gametes seems to be beneficial to produce sufficient offspring. However, the production of numerous gametes also means a weakening of the soma. which in the case of semelparous species seems to be the reason for the moribundity of the individual. Moreover, in many semelparous species mature individuals undertake excursions or even long-distance migrations to meetsexual partners and to locate their offspring at particular habitats, like squid, lampreys, salmon and eels, thereby undergoing additional heavy risks of predation. Furthermore, when animals invest so much of their somatic resources they must also develop particularly effective mechanisms securing fertilization, i.e. the synchronization and rendezvous of sexual partners. Within the polyrchaetes we find a tremendous (adaptive?) diversity of reproductive modes.