ABSTRACT. In general, flagella and cilia of eukaryotes show an axoneme composed of a 9 + 2 microtubular pattern. However, the axoneme of spider spermatozoa is characterized by an exceptional 9 + 3 microtubular pattern, which is known as a synapomorphy of the Megoperculata (Amblypygi, Uropygi and Araneae). In contrast to all other observed spiders, the axoneme of the linyphiid spider Linyphia triangularis, was shown to lack the central microtubules thus representing a 9 + 0 axoneme. ...