Polymely of feeding appendages in Tegenavia atvica (Araneae: Agelenidae)

摘要

Two interesting cases of polymely of the chelicerae were obtained after using thermal shocks in the form of temperatures of 14 and 32 °C acting alternately on spider embryos in the first 10 days of development. An analysis of histological sections made by the paraffin method and stained with haematoxylin and eosin demonstrated changes in the neuromerism of the central nervous system. The chelicerae are the first, comparatively short, pair of cephalic appendages in spiders. They consist of only two joints: the large cylindrical basal joint and the terminal one developed in the form of a claw with the opening of the poison gland. This pair of appendages is innervated by the syncerebrum, which is believed by some arachnologists to have formed as a result of fusion of the protocerebrum and deutocerebrum (Babu & Barth, 1984; Legendre, 1959). As demonstrated by many years' teratological studies of Tegenaria atrica C. L. Koch embryos, the chelicerae, like other prosomal appendages, are subject to variousdevelopmental anomalies (Jacuhski, 1984; Jacunski et al, 2002, 2004). Most frequently these anomalies occur in the structure of the basal joint. However, the shape and size of the claw may also change relatively rarely. These deformities impede food ingestion but are of no major significance for the overall structure of the fore part of the spider's body. Serious complications in the body morphology occur only in the case of absence of the chelicerae or of the presence of an accessory one, which can be caused by disturbances in the metamerism of the germ band. The effects of these anomalies are perceivable in the anatomical structure and architectonics of internal organs, particularly in the structure of the nervous system.