Life cycle strategy of herbivorous copepod Calanoides acutus (Crustacea, Calanoida) in the Antarctic Ocean
The dominant Antarctic herbivorous copepod Calanoides acutus accumulates large quantities of lipids as an energy reserve during the productive season, and migrates to deeper waters to enter a state of diapause during winter month. Lipid storage is a major adaptation to the extreme seasonality of phy...
| Main Authors: | , , |
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| Format: | Thesis |
| Language: | English |
| Published: |
2004
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| Subjects: | |
| Online Access: | https://ir.soken.ac.jp/?action=repository_uri&item_id=824 http://id.nii.ac.jp/1013/00000824/ |
| Summary: | The dominant Antarctic herbivorous copepod Calanoides acutus accumulates large quantities of lipids as an energy reserve during the productive season, and migrates to deeper waters to enter a state of diapause during winter month. Lipid storage is a major adaptation to the extreme seasonality of phytoplankton growth in the polar regions. Therefore, storage lipid is an important factor affecting their biological activity. However, there have only been sporadic studies on copepod lipid storage and life cycles in Antarctic waters. Taking the opportunity of multi-ship observations in the Indian sector of the Antarctic Ocean, the objectives in the present study were to examine both the preserved samples by a net sampling, and physiological characteristics of C. acutus over the whole summer, and to develop hypotheses of the species life cycle strategy. This is the first time that such time serial observations over the whole summer, combined with a comprehensive approach to the species life cycle from both preserved samples and physiological characteristics have been conducted. Copepods were collected on RSV Aurora Australis in November 2001, Hakuho Maru in January 2002 and RV Tangaroa in February 2002 along a transect on 140°E between 61 and 66.25°S using a twin NORPAC standard net. Closed 2-l jars served as cod ends to avoid damage to the specimens. Until recently it had been accepted that the life span of Calanoides acutus was one-year, and the overwintering stages are predominantly copepodite V （CV） stage. They molt to adulthood and mature at depth, and fertilized females ascend to the surface waters for spawning. However, from the observation of this study, CV stages were dominant in the surface in November ranging from 10 to 40％ of the total population. In previous studies, the development rate of C. acutus was reported to be around 15 to 30 days per copepodite stage. Therefore, CV stages at the surface in November had not developed from eggs in that spring, but had overwintered, and had not been able to mature ... |
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