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Title :Seasonal development of gonads of the hagfish, Eptatretus burgeri, correlated with their seasonal migration
Authors :Nozaki, Masumi
Ichikawa, Tomoyuki
Tsuneki, Kazuhiko
Kobayashi, Hideshi
Publisher :Zoological Society of Japan
Issue Date :2000
Journal Title :Zoological Science
Volume :17
Issue :2
Start Page :225
End Page :232
ISSN :0289-0003
Description :Seasonal development of gonads was studied in the hagfish, Eptatretus burgeri, caught near the Misaki Marine Biological Station facing the Sagami Bay of the Pacific coast of Japan, during periods from October 1971 to March 1973 and from November 1977 to December 1978. The hagfish were collected at water depths of 6 to 10m (shallow water) in Koajiro Bay close to the Station or water depths of 50 and 100m (deep water), about 1,600 and 4.800m west to the Station. They were collected monthly from both shallow and deep waters, but they could not be collected from shallow water during warmer summer months (July-September) due to seasonal migration. The mean total lengths of the females collected in both shallow and deep waters during January to April were 40.7±0.4cm (±SEM; n=317) and 34.5±0.3cm (±SEM; n=556), respectively. In both locations, developing eggs longer than 5mm were found in females larger than 39cm in total length. There was no difference in the annual growth curves of developing eggs between shallow and deep water: the sizes of the developing eggs were the smallest in October, and was the largest in September. There was no apparent difference in testicular development between two locations, so these data were combined. Testicular development occurs in males larger than 38cm in total length. The testis weight was the heaviest in July, and was the lightest in September. In autumn and winter, most testicular follicles contained only spermatogonia. In spring, follicles containing spermatocytes increased. Follicles with spermatids or maturing sperms were relatively abundant in summer. Although egg deposition is supposed to occur in September and/or early October somewhere in deep water, both testis weight and spermatogenesis were minimal at this time. Why testis development is lowest at the time when females presumably deposit eggs is discussed in relation to the question of the location of the spawning ground.
Type Local :学術雑誌論文
Language :eng
URI :http://hdl.handle.net/10191/6285
fullTextURL :http://dspace.lib.niigata-u.ac.jp/dspace/bitstream/10191/6285/1/08_0004.pdf
Appears in Collections:10 査読済論文 = Postprint

Please use this identifier to cite or link to this item: http://hdl.handle.net/10191/6285