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KMID : 0894520090130020115
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Development & Reproduction
2009 Volume.13 No. 2 p.115 ~ p.122
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Spermatogenesis and Ultrastructural Characteristics of Spermatozoa of Brackish Water Diploid Clam, Corbicula japonica (Bivalvia: Corbiculidae)
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Jun Je-Cheon
Kim Bong-Seok
Chung Ee-Yung
Kim Jin-Hee
Park Gab-Man
Park Sung-Woo
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Abstract
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Spermatogenesis and ultrastructural characteristics of sperm of brackish water diploid Corbicula japonica were investigated by electron microscope observations. Based on the cytological studies, the spermatozoon of this species (brackish water diploid) C. japonica is approximately 55 ㎛ in length. The sperm head (about 12 ㎛ long) is elongated and tapers with a slight curve. Sperm nucleus is about 7.90 ㎛ long, and the acrosome is about 2.70 ㎛ long: The morphologies of the sperm nucleus type and the acrosome shape of this species are a long arrow-like type and long cone-like shape, respectively. The sperm head of this species (external fertilization, dioecious and oviparous species) is partially modified from that of the primitive type, as seen in triploid Corbicula species (internal fertilization, hermaphrodite and ovoviparous species), reported by some authors. However, this species produces uniflagellate spermatozoa, unlike freshwater triploid hermaphroditic clams being possessed of partially modified biflagellate spermatozoa. Diploid C. japonica is similar to those of other bivalves being possessed of a short midpiece containing four mitochondria surrounding the centrioles. The axoneme of the sperm tail flagellum consists of nine pairs of microtubules at the periphery and a pair at the center. The axoneme of the sperm tail shows a 9+2 structure, and from uniflagellate sperm cross sectioned, in particular, wing-like axonemal lateral fins are observed, as seen in external fertilization fishes.
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KEYWORD
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Corbicula japonica, Diploid, Spermatogenesis
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