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Cylindrical organelles associated with microtubules during sperm elongation in a mealybug
Abstract:
Spermiogenesis in the mealybug Pseudococcus obscurus involves the elongation of a cytoplasmic papilla from the surface of a spermatid. Longitudinally oriented fibers and microtubules, with diameters of 250 A and a non-9+2 arrangement, are associated with this process. Fibers alone are found in early stages of papilla emergence and in the basal region of the elongated papilla. They appear to be continuous with the microtubules in the more distal region of an elongated papilla. Disk-shaped, circular, and rectangular profiles are associated with the basal ends of the fibers. Probably the fibers are microtubular "anlagen" and the associated structures may be microtubular "organizing centers".
Insights
Mealybug sperm development involves a cytoplasmic papilla. Specialized fibers and microtubules, likely microtubule organizing centers, drive this unique spermiogenesis process in Pseudococcus obscurus.
Area of Science:
- Cell Biology
- Developmental Biology
- Entomology
Background:
- Spermiogenesis, the process of sperm development, exhibits diverse mechanisms across species.
- The mealybug Pseudococcus obscurus presents a unique model for studying sperm elongation.
Purpose of the Study:
- To investigate the ultrastructural basis of cytoplasmic papilla elongation during spermiogenesis in Pseudococcus obscurus.
- To identify the cellular components involved in the formation and elongation of the cytoplasmic papilla.
Main Methods:
- Transmission electron microscopy was used to examine the ultrastructure of developing spermatids.
- Detailed analysis of longitudinally oriented fibers and microtubules within the cytoplasmic papilla.
Main Results:
- Spermiogenesis involves cytoplasmic papilla elongation, characterized by longitudinally oriented fibers and microtubules (250 Å diameter) with a non-9+2 arrangement.
- Fibers are present in early stages and the basal region, appearing continuous with distal microtubules.
- Basal fiber ends are associated with disk-shaped, circular, and rectangular profiles, suggesting organizing centers.
Conclusions:
- The observed fibers are likely microtubule precursors (anlagen).
- Associated structures may function as microtubule organizing centers, crucial for papilla elongation.
- This study elucidates a novel mechanism of spermiogenesis in mealybugs.