Spermiogenesis and sperm ultrastructure of Asetocalamyzas laonicola Tzetlin, 1985 (Polychaeta), an ectoparasite of the large spionid Scolelepis cf. matsugae Sikorsfi, 1994, from the White Sea

• Published in: Scientia Marina
• Main Authors: Vortsepneva, Elena V., Zhadan, Anna E., Tzetlin, Alexander B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Consejo Superior de Investigaciones Científicas 2006
• Subjects: spermiogenesis; sperm ultrastructure; Asetocalamyzas laonicola; Scolelepis cf. matsugae; espermegiogénesis; ultraestructura del esperma; Asetocalamyza laonicola; Alta; Blanco; Periferia; White Sea
• Online Access: https://scientiamarina.revistas.csic.es/index.php/scientiamarina/article/view/140; https://doi.org/10.3989/scimar.2006.70s3343

The sperm ultrastructure and spermatogenesis of the ectoparasitic polychaete Asetocalamyzas laonicola Tzetlin, 1985 (Calamyzidae) is investigated. The male cells are located freely in the coelom. The spermatocytes are large cells of irregular shape; their nuclei have condensed chromatin in the periphery. Spermatocyte cytoplasm is granular and electron-dense with several spherical mitochondria. During early developmental stages spermatids are aggregated into a rosette (four cells). The early spermatids have a tiny acrosomal vesicle at one side of the cell, a few round mitochondria at another, and electron dense nuclei. The late spermatids have elongated mitochondria, a well-developed acrosome and a flagellum. The mature sperm are threadlike with a round acrosomal vesicle, an electron-dense structure. The elongated nuclei have anterior and posterior depressions. The supporting root zone of the acrosome is located behind the acrosomal vesicle in the anterior invagination of the nuclei. Six elongated mitochondria surround the flagellum and form the midpiece of the sperm. A single centriole lies in the posterior depression of the nucleus. The middle part of the flagellum possesses a normal (9+2x2) pattern. Probably, the terminal part of flagellum is modified. The sperm structure suggests internal fertilization or another type of specialized sperm transfer in A. laonicola. La ultraestructura del esperma y la espermatogénesis del poliqueto ectoparásito Asetocalamyzas laonicola Tzetlin, 1985 (Polychaeta) ha sido investigada. Las células masculinas están localizadas libres en el celoma. Los espermatocitos son células grandes de forma irregular cuyos núcleos presentan cromatina condensada en su periferia. El citoplasma de los espermatocitos es granular y presenta alta densidad a los electrones, así como distintas mitocondrias esféricas. Durante el desarrollo inicial, las espermatidas se encuentran agregadas en rosetas de cuatro células. Las espermatidas iniciales presentan una minúscula vesícula acrosomal a un lado de ...