2026-09-18T17:21:17Zhttps://gupea.ub.gu.se/server/oai/request

oai:gupea.ub.gu.se:2077/210302013-04-23T12:46:45Zcom_2077_4722com_2077_4716com_2077_10556col_2077_4723col_2077_10557

Lord, Hans 2009-10-19T10:31:43Z 2009-10-19T10:31:43Z 2009-10-19T10:31:43Z 978-91-628-7844-3 http://hdl.handle.net/2077/21030 Some Bosmina and Daphnia species have the ability to develop extreme morphological antipredator defences, such as long antennules, high carapaces and helmets. The relative sizes of these plastic traits may differ substantially between populations, and also between individuals within a population, between sexes and during ontogeny. In this thesis I examine how abiotic factors (trophic levels and temperature) and biotic factors (fish and invertebrate predators) affect the size and shape of these traits. In the first two studies, calculations based on experimental results using physical morphological models sinking in glycerine, were used to estimate body drag and energy consumption in Bosmina. Eubosmina longispina, with a low carapace and short antennules, and Eubosmina coregoni gibbera, with a very high carapace and long antennules, were examined. At 5○C, E. c. gibbera had 32-45 % higher body drag than E. longispina. At 20○C the difference was 20-45 %. A model of swimming predicted that, all else being equal, this difference should result in 18-20 % (at 5○C) or 14-16 % (at 20○C) lower swimming speed for E. c. gibbera than for E. longispina. This indicates substantial hydrodynamic costs of the morphological antipredator defences, particularly in low temperatures. The morphological antipredator defences in E. c. gibbera are larger and more variable in females than in males. Male models had lower body drag than models of asexual and sexual females, suggesting that males can swim 14-28 % faster with the same energy consumption. High speed video documentation of swimming E. c. gibbera showed that males advanced 55-73 % further than females in each swimming stroke. Hydrodynamic body drag may therefore have significant implications for swimming and evolution of sexual dimorphism in water fleas. Males may lack the defensive, but hydrodynamically expensive, high carapace of female E. c. gibbera probably because competition over mates favours low body drag. The morphology and size of heads and trunks in Daphnia cristata individuals were studied in twenty lakes in the same drainage basin. The lakes showed a variation in lake total phosphorus and in densities of invertebrate predators and fish. In the end of the summer D. cristata had varying shape and size of their heads. Our results indicate that D. cristata, in nutrient rich lakes, show adaptive morphological defences against both visually hunting and size limited predators. Female D. cristata head shape, in the examined lakes, varied from small and rounded to large and curved. A significant positive correlation between lake total phosphorus and the allometric head coefficients was found, suggesting that the most extremely shaped heads are found in nutrient-rich lakes. eng I.Lagergren R., Lord H. and Stenson J.A.E. (2000) Influence of temperature on hydrodynamic costs of morphological defence in zooplankton: experiments on models of Eubosmina (Cladocera). Funct. Ecol. 14: 380-387.::DOI::10.1046/j.1365-2435.2000.00433.x II. Lord H., Lagergren R., Svensson J-E. and Lundqvist N. (2006) Sexual dimorphism in Bosmina: the role of morphology, drag and swimming. Ecology 87(3): 788-795.::DOI::10.1890/05-0082 III. Lord H. and J-E Svensson. Size and shape of Daphnia cristata heads reflect trophic condition of lakes. Submitted. IV. Lord H. and J-E Svensson. Multipredator pressure; defences and consequences in Daphnia cristata. Manuscript. Body drag Daphnia cristata Reynolds number viscosity zooplankton Bosmina swimming velocity cyclomorphosis sexual dimorphism head area helmet angle trophic condition allometry invertebrate predator fish Morphological antipredator adaptations in water fleas Text Doctoral Theses Doctor of Philosophy hans.lord@zool.gu.se Morphological Antipredator Adaptations in Water Fleas Hans Lord, 2009 Department of Zoology Animal Ecology Box 463, SE-405 03 Gothenburg Sweden Akademisk avhandling för doktorsexamen i biologi med inriktning mot ekologi. Avhandlingen kommer att offentligt försvaras med början kl.10.00 fredagen den 6:e november 2009 i stora föreläsningssalen (entreplan), Zoologiska institutionen, Medicinaregatan 18 i Göteborg. Examinator är professor Staffan Andersson. Opponent är professor Petter Larsson från Institutt för biologi, Universitetet i Bergen, Norge. University of Gothenburg. Faculty of Science Department of Zoology ; Zoologiska institutionen Fredag den 6 november kl.10.00, stora föreläsningssalen, zoologiska institutionen, Medicinaregatan 18, Göteborg 2009-11-06 MNF open.access