title: Effects of algal food quality on sexual reproduction of Daphnia magna.
abstract: The objective of our study was to investigate sexual reproduction of Daphnia magna associated with mating behaviors and hatching rates, according to different algal food sources. Since a diatom is known to contain more abundant long-chain poly unsaturated fatty acids (PUFAs), we hypothesized that the diatom-consuming D. magna would exhibit more successful reproduction rates. Upon the hypothesis, we designed three experiments using two algal species, a green alga (Chlorella vulgaris) and a diatom (Stephanodiscus hantzschii). From the results, we found that the mating frequency and copulation duration increased in the treatment with S. hantzschii, resulting in a significant increase of hatching rates of resting eggs. In the other two repetitive mating strategies (e.g., one female vs. multiple males, and one male vs. multiple females), we found that the hatching rates of resting eggs were greater in the S. hantzschii treatment. In addition to the mating strategy, male body size significantly increased in the diatom treatment, hence average diameter of penis was also statistically different among the treatments (greater diameter in the S. hantzschii treatment). To examine the effect of algal food quality, we estimated quantity of fatty acids in the two algal species. Our result showed that S. hantzschii had a higher proportion of long-chain PUFAs than C. vulgaris. Furthermore, a stable isotope analysis revealed that carbon and nitrogen originated from S. hantzschii were more assimilated to D. magna. In summary, our study manifested that diatom consumption of D. magna leads to more successful sexual reproduction. We then discussed how the diatom consumption of zooplankton influences food web dynamics in a freshwater ecosystem.
authors.affiliation: National Institute of Ecology Seo-Cheon Gun Chungcheongnam Province 325-813 Korea.
authors.forename: Jong-Yun
authors.initials: JY
authors.lastname: Choi
authors.affiliation: Department of Biological Sciences Pusan National  University Busan 609-735 Korea.
authors.forename: Seong-Ki
authors.initials: SK
authors.lastname: Kim
authors.affiliation: Department of Environmental Education Sunchon National University Sunchon 540-742 Korea.
authors.forename: Geung-Hwan
authors.initials: GH
authors.lastname: La
authors.affiliation: Department of Environmental Engineering Kyung-Hee University Yongin 446-701 Korea.
authors.forename: Kwang-Hyeon
authors.initials: KH
authors.lastname: Chang
authors.affiliation: Department of Physical & Environmental Sciences University of Toronto Toronto ON M1C 1A4 Canada.
authors.forename: Dong-Kyun
authors.initials: DK
authors.lastname: Kim
authors.affiliation: Institute of Environmental Science & Technology Pusan National University Busan 609-735 Korea.
authors.forename: Keon-Young
authors.initials: KY
authors.lastname: Jeong
authors.affiliation: Advanced Biomass R&D Center Korea Advanced Institute of Science & Technology Daejeon 305-701 Korea.
authors.forename: Min S
authors.initials: MS
authors.lastname: Park
authors.affiliation: Department of Biological Sciences Pusan National  University Busan 609-735 Korea.
authors.forename: Gea-Jae
authors.identifier: 0000-0001-8064-7880
authors.initials: GJ
authors.lastname: Joo
authors.affiliation: Department of Environmental Education Sunchon National University Sunchon 540-742 Korea.
authors.forename: Hyun-Woo
authors.initials: HW
authors.lastname: Kim
authors.affiliation: Department of Biological Sciences Pusan National University Busan 609-735 Korea; Institute of Environmental Science & Technology Pusan National University Busan 609-735 Korea.
authors.forename: Kwang-Seuk
authors.initials: KS
authors.lastname: Jeong
keywords: Algal food quality; Chlorella vulgaris; Daphnia magna; Stephanodiscus hantzschii; sexual reproduction