Comparative ecophysiology of two mixotrophic species of "Dinophysis" producers of lipophilic toxins

• Autores: María García Portela
• Directores de la Tesis: Francisco José Rodríguez Hernández (dir. tes.), Beatriz Reguera Ramírez (dir. tes.)
• Lectura: En la Universidade de Vigo ( España ) en 2019
• Idioma: inglés
• Tribunal Calificador de la Tesis: Raffaele Siano (presid.), Rosa Isabel Figueroa Pérez (secret.), Sandra Martínez García (voc.)
• Programa de doctorado: Programa de Doctorado en Ciencias Marinas, Tecnología y Gestión por la Universidad de A Coruña; la Universidad de Santiago de Compostela; la Universidad de Vigo; Universidade de Aveiro(Portugal); Universidade de Trás-os-Montes e Alto Douro(Portugal) y Universidade do Minho (Portugal)
• Materias:
  • Química
    • Química macromolecular
      • Plásticos celulares
  • Ciencias de la vida
    • Biología celular
      • Cultivo celular
• Enlaces
  • Tesis en acceso abierto en: Investigo
• Resumen

  • The Dinophysis species D. acuminata and D. acuta present different spatio-temporal patterns, toxin profiles and cause specific impacts (DSP events) on resources, being a problem in the Galician Rias. Closures due to DSP toxins range from 3 to 9 months per year, depending on the overlap between the appearance of D. acuminata (spring-early autumn) and D. acuta (late autumn). Laboratory cultures of the genus Dinophysis are difficult to establish mainly due to its mixotropic character, capable of obtaining energy by ingesting other organisms (e.g., phagotrophy of the ciliate Mesodinium) and through photosynthesis. Thanks to the discovery in 2006 of a system based on the trophic chain of three organisms (cryptophyceae of the genus Teleaulax, the ciliate Mesodinium and the dinoflagellate Dinophysis) cultures of Dinophysis were established in the laboratory for the first time.

    Despite the similarity between both species, the spatio-temporal gap observed in the distribution and development of populations of D. acuminata and D. acuta suggests that, apart from prey availability, these species may benefit from various environmental factors.

    Based on the above considerations, the following objectives are proposed:

    I. Main objective: comparative ecophysiological study of Dinophysis acuminata and D. acuta as an experimental contribution to the description of their niches.

    This main objective will be addressed through four secondary objectives: I. Photosynthetic characterization (photosynthesis/Irradiance curves), toxinological and pigment composition of well-fed cells of D. acuminata and D. acuta exposed to different light conditions.

    II. Comparative response of D. acuminata and D. acuta to small-scale turbulence conditions to study the influence of physical factors.

    III. Identification of the main nitrogen source took up by D. acuminata and D. acuta.

    IV. Biochemical characterization of the species D. acuminata and D. acuta through the comparison of their metabolomic profiles.

    The main results were:

    I. The purely autotrophic cryptophyte Teleaulax amphioxeia and the phototrophic ciliate Mesodinium rubrum took advantage of higher intensities of white light (75-650 μmol photons m-2 s-1). Dinophysis acuta was more resistant to darkness than D. acuminata while changes in photosynthetic light curves examined in the latter were compatible with photoaclimation.

    Dinophysis acuminata contains okadaic acid (OA), while D. acuta, in addition to OA, contains dinophysistoxin-2 (DTX2) and pectenotoxin-2 (PTX2). The highest content of intracellular toxin was recorded for PTX2 under high light conditions (350 μmol photons m-2 s-1) during the stationary phase of growth in D. acuta.

    II. Dinophysis acuta was more sensitive to the turbulence than D. acuminata, and the effects of high levels of turbulence (ε = 10-4 m2 s-3), induced negativegrowth in the first. On the contrary, D. acuminata continuously grew under the same high turbulence conditions but at a considerably lower rate than in the controls.

    III. Both Dinophysis species preferred regenerated sources (ammonium and urea). The incorporation of both sources was always higher in the two Dinophysis species in well fed cells than in those starved. The uptake by D. acuta was always higher than that of D. acuminata in both nutritional states.

    IV. The variable "species" was the one that most separated D. acuminata and D. acuta, followed by the variable "origin of the prey" (danish and spanish strains of Mesodinium rubrum). Many of the compounds obtained were tentatively identified (e.g., alkaloids previously reported in starfish and sponges), including a new diol ester derived from OA.