| Popis: |
There is increasing evidence that the use of sperm structure can be of great help in phylogenetic reconstruction at any taxonomic level [see Baccetti and Afzelius’ (1976) and Jamieson’s (1987) extensive reviews]. Quoting the latter author, ‘opposition to its (sperm structure) use is usually dispelled when its effectiveness for resolving hitherto intractable problems of taxonomic placement and relationship is demonstrated’. The range of sperm structural diversity is so large that it is often possible to ascribe quite reliably any single sperm cell to a hierarchy of taxa (i.e. phylum, order, family, genus and even species). A primitive sperm architecture can be recognized throughout the metazoans in unrelated species which have retained the primitive mode of fertilization (Franzen 1977). As a consequence, animals with a primitive spermatozoon are very unlikely to have arisen from animals with a derived one. Implicit in this, apomorphies and plesiomorphies between related taxa can be clearly determined and hence questionable phylogenetic relationships solved. |
