Microstructural analysis on the testicular cyst of the wolf spider by 3D volume rendering

Abstract

Spermatogenesis has long been a major research area in understanding the development of living organisms. In vertebrates, sperm is produced along the wall of the seminiferous tubules, leaving spermatogonia in the outermost layer, which undergo cell division and differentiation. However, sperm in many invertebrates is developed in a testicular cyst, which contains germ cells at the same developmental stages. On the contrary, in spiders, it is very difficult to count the exact number of cells in a cyst, since each spermatid gets transformed to a round sperm ball within the cyst through the flagellar coiling process. Therefore, in this study, we applied a 3D rendering technique to analyze the exact number of germ cells per cyst in spiders. For image processing and reconstruction, serial section images were scanned and reconstructed into 3D images. Upon successful 3‐dimensional reconstruction of testicular cysts, the exact number of germ cells produced from a single cyst appeared to be 64, 26 which indicates that a spider spermatogonium undergoes 6 cell divisions to produce spermatozoa.

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

“…Virkki (1969) suggested in insects that the more advanced orders and specialized groups are characterized by smaller number of sperms than the archaic or the less specialized groups. However, our findings obtained through serial researches among the familial levels of spiders do not seem to coincide with Virkki's proposal since a wandering lycosid spiders P. laura (Kim et al 2014) exhibited smaller number per cyst compared to a specialized group of web-building araneid spiders L. cornutus (Kim et al 2015).…”

“…The results of this study together with comparisons to our previous studies of the sperm number per cyst (Kim et al 2014(Kim et al , 2015 contribute novel biological and evolutionary knowledge of these sperm number and their competition. This study shows that the furrow orb-web spider L. cornutus (Araneae, Araneidae) produces 128 spermatozoa from one testicular cyst.…”

“…This study shows that the furrow orb-web spider L. cornutus (Araneae, Araneidae) produces 128 spermatozoa from one testicular cyst. However, previous studies have shown that both of the lycosid spider Pardosa laura (Kim et al 2014) and theridiid spider Achaearanea tepidariorum (Kim et al 2015) were composed of 64 sperms per cyst.…”

“…Up to now, this area of research in spiders is still limited and there are only few studies on the field revealing the exact number of sperms per cyst and the number of cell divisions during the spermatogenetic process (Kim et al 2014).…”

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

“…), the knowledge in terms of spider sperm division is still very limited and only a little is known on the number of germ cells produced per cyst (Kim et al . ). In this sense, this study aims to provide information regarding the number of sperm produced per single testicular cyst using a three dimensional image reconstruction technique on a species of the theridiid spider, Achaearanea tepidariorum .…”