Fine structural reconstruction on the testicular cyst of the furrow orb weaver, Larinioides cornutus by 3D volume rendering

Morphological study on spermatids and spermatozoa have long been performed regarding various changes of cell organelles during spermiogenesis as a potential phylogenetic inference. Based on the fact that the number of germ cells per cyst increases according to a geometric series, knowing the exact number of germ cells in a certain stage may lead to the total number of sperms produced per cyst. In spiders, however, the entire process takes place in a cyst represented by a spermatogonium, producing sperms in spherical shape. It is very difficult to count the exact number of germ cells produced per cyst through a 2D image analysis. Therefore, we applied a 3D image of testicular cyst of an orb-weaving spider to visualize the exact number of germ cells produced from a cyst. In this study, 2D images obtained from serially sectioned micrographs were scanned precisely and reconstructed using a 3D-rendering technique. Finally, this research reveals that the exact number of spermatozoa produced each cyst in Larinioides cornutus appeared to be 128 ($2^7$), which indicates that a single spermatogonium undergoes five mitotic divisions and two maturing divisions (meiosis) to produce final spermatozoa.