title: When shape matters: strategies of different Antarctic ascidians morphotypes to deal with sedimentation.
abstract: Climate change leads to increased melting of tidewater glaciers in the Western Antarctic Peninsula region and sediment bearing glacial melt waters negatively affects filter feeding species as solitary ascidians. In previous work the erect-forms Molgula pedunculata and Cnemidocarpa verrucosa (Order Stolidobranchiata) appeared more sensitive than the flat form Ascidia challengeri (Order Phlebobranchiata). Sedimentation exposure is expected to induce up-regulation of anaerobic metabolism by obstructing the organs of gas exchange (environmental hypoxia) or causes enhanced squirting activity (functional hypoxia). In this study we evaluated the possible relationship between ascidian morphotype and their physiological response to sedimentation. Together with some behavioural observations, we analysed the response of anaerobic metabolic parameters (lactate formation and glycogen consumption) in different tissues of three Antarctic ascidians, exposed to high sediment concentrations (200 mgL(-1)). The results were compared to experimental hypoxia (10% pO2) and exercise (induced muscular contraction) effects, in order to discriminate the effect of sediment on each species and morpho-type (erect vs. flat forms). Our results suggest that the styled (erect) C. verrucosa increases muscular squirting activity in order to expulse excessive material, while the flat-form A. challengeri reacts more passively by down-regulating its aerobic metabolism under sediment exposure. Contrary, the erect ascidian M. pedunculata did not show any measurable response to the treatments, indicating that filtration and ingestion activities were not reduced or altered even under high sedimentation (low energetic material) which could be disadvantageous on the long-term and could explain why M. pedunculata densities decline in the study area.
authors.affiliation: Marine Ecology Department, Instituto de Diversidad y Ecología Animal (IDEA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba (UNC), Córdoba, Argentina. Electronic address: torreluciana@gmail.com.
authors.forename: Luciana
authors.initials: L
authors.lastname: Torre
authors.affiliation: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany.
authors.forename: Doris
authors.initials: D
authors.lastname: Abele
authors.affiliation: Marine Ecology Department, Instituto de Diversidad y Ecología Animal (IDEA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba (UNC), Córdoba, Argentina.
authors.forename: Cristian
authors.initials: C
authors.lastname: Lagger
authors.affiliation: Instituto de Ciencias Universidad Nacional de General Sarmiento, J. M. Gutierrez 1150 (1613), Los Polvorines, Buenos Aires, Argentina; INEDES, Universidad Nacional de Luján, CC 221, 6700 Luján, Argentina.
authors.forename: Fernando
authors.initials: F
authors.lastname: Momo
authors.affiliation: Marine Ecology Department, Instituto de Diversidad y Ecología Animal (IDEA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba (UNC), Córdoba, Argentina.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Sahade
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000693:Anaerobiosis; D000704:Analysis of Variance; D000818:Animals; D000864:Antarctic Regions; D004734:Energy Metabolism / Q000502:physiology*; D019015:Geologic Sediments; D006003:Glycogen / Q000378:metabolism; D019344:Lactic Acid / Q000096:biosynthesis; D009119:Muscle Contraction / Q000502:physiology; D019370:Observation; D010100:Oxygen / Q000378:metabolism; D013045:Species Specificity; D014561:Urochordata / Q000033:anatomy & histology* / Q000502:physiology
chemical_list: D019344:Lactic Acid; D006003:Glycogen; D010100:Oxygen
keywords: Ascidia challengeri; Cnemidocarpa verrucosa; Glycogen; Hypoxia; Lactate; Molgula pedunculata; Sedimentation