BIOMETRIC STUDIES ON OLIGOMELIC INDIVIDUALS OF THE SPIDER TEGENARIA ATRICA (ARTHROPODA, ARACHNIDA) / BADANIA BIOMETRYCZNE OSOBNIKóW OLIGOMELICZNYCH PAJ?KA TEGENARIA ATRICA (ARTHROPODA, ARACHNIDA)

摘要

Oligomely is a type of developmental anomaly occurring in embryos of the spider Tegenaria atrica C.L. Koch under the teratogenic influence of temperature. This anomaly is of metameric origin, as it results from a disorder of metamere formation on the germ band during embryogenesis, resulting in the absence of one half or the whole metamere. In such a case, one or more appendages are missing on one or both sides of the body in a spider leaving a chorion. This anomaly induces changes both in the anatomical structure and exoskeleton of a spider (deformation of carapace and sternum). Carapace length and sternum area were measured, as well as the duration of the subsequent nymph stages of oligomelic individuals with one of the walking appendages missing (always on the right side of the body) was recorded. The consecutive nymph stages of oligomelic individuals lasted for a much shorter time compared with control specimens. This acceleration of development is probably to offset losses incurred during embryogenesis. In the early postembryogenesis, oligomelic specimens exhibited shorter carapace length and smaller surface area of the sternum compared to control individuals, which resulted from the lack of half of the metamere corresponding to the missing leg. However, in older nymph stages, a strong tendency for the faster growth of both carapace and sternum was observed, which can be defined as a compensatory growth increase making up for the losses caused by the anomaly.