Structural analysis of theridiid spider's testicular cyst using 3D reconstruction rendering

A three dimensional reconstruction technique was used for the analysis of a theridiid spider's (Achaearanea tepidariorum) testicular cyst. Although microscopic techniques have greatly improved, most of the information gathered is still based on two‐dimensional images. Particularly in spiders, it is very difficult to count the exact number of sperm in a single cyst, since their spermatogenetic processes takes place within the spherical cysts through the flagellar coiling process. Since morphological features of spider sperm provide detailed information on the whole spermatogenetic processes, we analyzed the exact number of germ cells per cyst in A. tepidariorum through a three‐dimensional image reconstruction technique. For image processing, serially sectioned histological images were scanned using a light microscope and 3D rendering images were reconstructed from these sections. Based on the three dimensional image analysis of the testicular cyst, the number of secondary spermatocytes per cyst was calculated to be 32 (2⁵). Therefore the total number of sperm produced from a single cyst can be calculated as 64 (2⁶), which indicates that a single spermatogonium undergoes four mitotic divisions and an additional two meiotic divisions to produce mature spermatozoa.