Two morphological types in the reproductive stock of three-spined stickleback,Gasterosteus aculeatus,in Lake Harutori,Hokkaido Island |
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Authors: | Seiichi Mori |
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Institution: | (1) Department of Zoology, Kyoto University, Sakyo Kyoto, 606, Japan |
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Abstract: | Synopsis Two morphological types of the trachurus form (completely plated morph) of three-spined stickleback, Gasterosteus aculeatus, are found in Lake Harutori, Kushiro, east district of Hokkaido Island. For convenience, the two forms are referred to as
‘large type’ and ‘small type’ on the basis of body length (discrimination at 70 mm in length). The two types were examined
for morphometric, meristic and reproductive characteristics. They differ in body length, the number of lateral plates, means
of the 2nd dorsal spine length/body length and of the pelvic spine length/body length, the relationship between body length
and head length, between body length and gonad weight, between body weight and gonad weight, and between body length and ovarian
egg number; significant differences were present for each sex. These two types were compared with the anadromous stickleback
migrating into the freshwater area near Lake Harutori to breed. The anadromous fish was morphologically much more similar
to the large type than the small type. It is suggested that the large type is also an anadromous form and the small type is
the permanent freshwater resident. |
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Keywords: | Lake resident population Sympatric pair Bimodal size frequency Morphological differences Landlocking |
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