Related Experiment Video
Updated: Feb 16, 2026

Fish Sperm Assessment Using Software and Cooling Devices
Published on: July 28, 2018
Ultrastructure of spermatozoa in cobia, Rachycentron canadum (Linnaeus, 1766)
Krishnamoorthy Dhanasekar1, Narasimman Selvakumar1, Natesan Munuswamy1
1Unit of Aquaculture and Cryobiology, Department of Zoology, University of Madras, Guindy Campus, Chennai, 600 025, Tamil Nadu, India.
Abstract:
Ultrastructure and development of spermatozoa in cobia, Rachycentron canadum are described. Sections through the testis show different developmental stages viz, Spermatocytes, spermatids and sperm. Spermatozoa of R. canadum exhibit the configuration of uniflagellated, anacrosomal Type I aquasperm, typical for externally fertilizing fish. Mature spermatozoon is seen with a prominent head and long cylindrical flagellum. Ultrastructure of sperm shows invaginated 'U' shaped nucleus and other organelles. The mitochondrial matrix is electron-dense with irregular arrangement of the cristae. The nucleus reveals a deep invagination (nuclear fossa) in which the centriolar complex is located. The centriolar complex lies inside the nuclear fossa and is composed of a proximal and a distal centriole. The two centrioles are placed perpendicular to each other. The flagellum has a typical eukaryotic organization (microtubule doublets 9 + 2 pattern) and measures around 36.21 ± 0.42 μm in length. This study for the first time provides a comprehensive detail on the ultrastructure and developmental process of sperm in cobia, R. canadum.
Related Concept Videos
Sperm Structure and Semen Composition
Lampbrush Chromosomes
LBCs are made up of two pairs of conjugating homologous chromatids. Each chromatid consists of alternatively positioned regions of condensed-inactive chromatin and loosely placed-active side loops, which can be contracted and extended. The loops...
Microtubules in Cell Motility
Sperm Transport
The maturation phase occurs in the epididymis, where sperm...
Spermatogenesis
Microtubules in Signaling

