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Spermatozoa in triploids of the rosy bitterling Rhodeus ocellatus ocellatus
Author(s) -
Kawamura K.,
Ueda T.,
Aoki K.,
Hosoya K.
Publication year - 1999
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.1999.tb00688.x
Subject(s) - biology , milt , human fertilization , sperm , meiosis , andrology , spermatogenesis , ploidy , flagellum , reproduction , sperm motility , zoology , anatomy , botany , genetics , endocrinology , bacteria , gene , medicine
Artificially induced triploid male Rhodeus ocellatus ocellatus showed typical nuptial colorations, irrespective of spermiation. In milt from triploids, abnormal spermatozoa (malformation of the head and mitochondrion, excessive formation of the head, mitochondrion and flagellum, and no flagellum) occurred at 78°4% frequency. Spermatozoa with multiflagella were most common, often with a saccate‐like organ. Many triploid spermatozoa moved actively as long as those of diploids (10·92±0·91 min=mean±S.D., P >0·05), but did not advance like diploids, spinning around until movement ceased. The sperm density in triploids was < 2% of that from diploids. In triploid testes, deformed and variously sized spermatids were often observed, and normal spermatids and spermatozoa were seldom recognized. The DNA content of triploid spermatozoa varied greatly, compared with that of diploids. Peak of sperm DNA content differed slightly between two triploid samples with two peaks at 1·5 n and 1·9 n ( P <0·0001 in both), respectively. Triploids had the greatest average sperm head diameter of 2·25±0·67 μm (mean±S.D.), while that of diploids was 1·83±0·15 μm ( P =0·002). In the fertilization test using the eggs of diploids ( n =1500, 30 trials), only one egg developed. The embryo chromosome number was 60 (2·5 n) and the ploidy of spermatozoa contributing to fertilization appears to be 1·5 n. The extremely low fertility of triploid R. o. ocellatus spermatozoa seems to be caused by the reduced motility and large head size of spermatozoa, and the low sperm density of the milt. The ploidy of spermatozoa that are successful in fertilization is likely to be related to the distribution pattern in the DNA content of cells.