Cronodrilus
Family Bdellodrilidae (ref. ID; 6451, 6466)
- Cronodrilus ogygius (ref. ID; 6451, 6466)
Descriptions
The acrosome is long. The acrosome tube is straight, the anterior portion having an external helical ridge that extends for about 3 gyres and contains a short limen. The acrosome vesicle forms a bulbous protrusion anteriorly beyond the tube that is covered by a plasma membrane supporting a large apical corona. In the anterior bulbous region are two electron-dense rings, the anterior one being less dense. The vesicle ends posteriorly in a thickened ring parallel to the end of the tube. An invagination passes through the ring and extends almost to the anterior end of the tube, thus forming the subacrosomal space. The space is filled with electron-dense material with an acrosome rod located basally and passing through the vesicular ring. The posterior end of the rod contacts an electron-dense disc situated next to the nucleus. The nucleus is straight with a concavity in both the anterior end and the posterior end. The midpiece is short and the central tubules of the axoneme penetrate midway into the midpiece. The flagellum has an axoneme with prominent central sheath and a long, electron-dense-staining cylinder surrounding the base. The helical marginal fiber starts at the base of the flagellum and passes through the cylinder wall, with the fiber's thickness tapering towards the tail tip. (ref. ID; 6466)