title: Toxicity Overrides Morphology on Cylindrospermopsis raciborskii Grazing Resistance to the Calanoid Copepod Eudiaptomus gracilis.
abstract: Toxicity and morphology may function as defense mechanisms of bloom-forming cyanobacteria against zooplankton grazing. Yet, the relative importance of each of these factors and their plasticity remains poorly known. We tested the effects of chemical and morphological traits of the bloom-forming cyanobacterium Cylindrospermopsis raciborskii on the feeding response of the selective feeder Eudiaptomus gracilis (Calanoida, Copepoda), using a saxitoxin-producing strain (STX+) and a non-saxitoxin (STX-)-producing strain as food. From these two chemotypes, we established cultures of three different morphotypes that differed in filament length (short, medium, and long) by incubating the strains at 17, 25, and 32 °C. We hypothesized that the inhibitory effects of saxitoxins determine the avoidance of C. raciborskii, and that morphology would only become relevant in the absence of saxitoxins. Temperature affected two traits: higher temperature resulted in significantly shorter filaments in both strains and led to much higher toxin contents in the STX+ strain (1.7 μg eq STX L(-1) at 17 °C, 7.9 μg eq STX L(-1) at 25 °C, and 25.1 μg eq STX L(-1) at 32 °C). Copepods strongly reduced the ingestion of the STX+ strain in comparison with STX- cultures, regardless of filament length. Conversely, consumption of shorter filaments was significantly higher in the STX- strain. The great plasticity of morphological and chemical traits of C. raciborskii and their resultant contrasting effects on the feeding behavior of zooplankton might explain the success of this cyanobacterium in a variety of aquatic environments.
authors.affiliation: Departamento de Botânica - Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 20940-040, Brazil. luciana.rangel@gmail.com.|Department of Environmental Sciences, Aquatic Ecology and Water Quality Management Group, Wageningen University, Wageningen, The Netherlands. luciana.rangel@gmail.com.|Laboratório de Ecofisiologia e Toxicologia de Cianobactérias, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Avenida Carlos Chagas Filho, CCS-Bloco G-Cidade Universitária, Rio de Janeiro, 21941599, RJ, Brazil. luciana.rangel@gmail.com.
authors.forename: Luciana M
authors.initials: LM
authors.lastname: Rangel
authors.affiliation: Departamento de Ecologia, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil.
authors.forename: Kemal A
authors.initials: KA
authors.lastname: Ger
authors.affiliation: Departamento de Botânica - Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 20940-040, Brazil.
authors.forename: Lúcia H S
authors.initials: LH
authors.lastname: Silva
authors.affiliation: Departamento de Engenharia Sanitária e Ambiental, Universidade Federal de Juiz de Fora, Juiz de Fora, MG, Brazil.
authors.forename: Maria Carolina S
authors.initials: MC
authors.lastname: Soares
authors.affiliation: Department of Environmental Sciences, Aquatic Ecology and Water Quality Management Group, Wageningen University, Wageningen, The Netherlands.
authors.forename: Elisabeth J
authors.initials: EJ
authors.lastname: Faassen
authors.affiliation: Department of Environmental Sciences, Aquatic Ecology and Water Quality Management Group, Wageningen University, Wageningen, The Netherlands.|Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.
authors.forename: Miquel
authors.initials: M
authors.lastname: Lürling
mesh_terms: D000818:Animals; D033342:Copepoda / Q000502:physiology*; D046891:Cylindrospermopsis / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D005247:Feeding Behavior / Q000502:physiology; D005618:Fresh Water / Q000382:microbiology*; D060106:Lakes / Q000382:microbiology; D010839:Phytoplankton / Q000502:physiology; D012530:Saxitoxin / Q000096:biosynthesis / Q000633:toxicity; D015048:Zooplankton / Q000502:physiology
chemical_list: D012530:Saxitoxin
keywords: Cyanobacteria; Feeding inhibition; Harmful algal blooms; Saxitoxins; Temperature; Zooplankton