Microstructural Reconstruction for the Testicular Cysts of Wolf Spider Using 3D Volume Rendering Technique

In insects, the alignment of neighboring spermatid in the late stages is nearly perfect, so that a transverse section of a cyst containing late spermatids transects all the spermatids at approximately the same level. However, the testicular cysts of spiders are spherical, most cysts are arranged in order of increasing maturity from the periphery to the center of the testis. For this reason, it is difficult to observe the whole spermatids within a single microscopic slide and count them. Therefore, we demonstrate microstructural reconstruction technique enabling to count exact number of sperm cells per cyst with aid of 3D volume rendering. For image processing and reconstruction, serially sectioned histologic specimens were scanned with microscopy and 3D images were reconstructed using Amira 5.3.2 software from the image stacks of the germ cells and surrounding testicular cysts subsequentially. With the information gathered by 3D reconstruction, it has finally been counted that exactly 32 (2⁵) cells of the secondary spermatocytes per cyst. This means that most cysts in P. laura contain exactly 64 (2⁶) spermatids or spermatozoa, which presumably arose from four synchronous mitotic and two meiotic divisions. In addition, the number of divisions occurring in a cyst appears to be constant for this spider because it has been known that the number of spermatids per cyst is characteristic for each species.