Conservación ex situ de Cymodocea nodosa (Ucria) Ascherson. Propagación de semillas in vitro, y establecimiento de cultivos celulares.

[ES] El objetivo principal de esta tesis ha sido presentar soluciones a los problemas de conservación que afectan a la especie Cymodocea nodosa y su ecosistema en Canarias, llevando a cabo estrategias de conservación ex situ que incluyen el desarrollo de una técnica de propagación con la que obtener plántulas germinadas a partir de semillas, su aclimatación y trasplante al mar. Una vez desarrollada la técnica de propagación in vitro, nos planteamos abordar estrategias para optimizar el procedimiento establecido, interviniendo sobre la conservación de las semillas in vitro y sobre la mejora, previo al trasplante, del estatus nutritivo y del crecimiento de las plántulas. Con la experiencia adquirida se han establecido las bases del cultivo in vitro a partir de tejido embrionario, permitiendo el mantenimiento de cultivos celulares en condiciones asépticas. El protocolo desarrollado supone una herramienta nueva y fundamental para el futuro del cultivo in vitro de esta especie, ya que permite ensayar nuevas técnicas y protocolos de regeneración para poder obtener, en un futuro, embriones somáticos que se desarrollen hasta plantas completas aplicando la técnica de germinación y propagación desarrollada, y proveer, así, de material vegetal para llevar a cabo programas de restauración y trasplante sin recurrir a las praderas naturales.

Restoration of Cymodocea nodosa (Uchria) Ascherson seagrass prairies through seed propagation. Seed storage and growth of seedlings as affected by inorganic nutrients and plant hormones.

[EN] In the frame of the restoration of natural populations of Cymodocea nodosa of the Canary Islands, seeds are being collected at natural populations where germination is rather scarce and seasonal after dormancy. We have developed techniques of propagation in vitro of collected seeds, consisting in forced seed germination and seedlings propagation to obtain mature 20-30 cm plantlet, which eventually are being used for restoration. In order to improve the developed methodology, several experiments were conducted to adjust conditions for seed storage under different regimes of temperature without loosing germinative potential, fertilize during propagation with controlled released NPK fertilizers, and increase growth by dipping seedlings in solutions of the most common plant hormones.

Restoration of Cymodocea nodosa (Uchria) Ascherson seagrass prairies through seed propagation. Germination in vitro, plantlet acclimation and transplanting to natural meadows.

[EN] The seagrass Cymodocea nodosa (Ucria) Ascherson is the most abundant seagrass species in the Canary Islands (Spain), where it forms dense submerged, ecologically relevant communities as stable and protected habitats. As with other seagrasses, concern has arisen due to a decline in the number and extension of the communities as the result of adverse activities in coastal areas. Seed germination and planting are assumed as cost-effective method for restoration. In the frame of the restoration of natural populations of Cymodocea nodosa, pilot experiences not tested so far in the Canary Islands have been carried out to developed in vitro techniques to produce viable seedlings and its transference to the natural environment.

Axenic cell culture of the seagrass Cymodocea nodosa from cotyledonary tissue

[EN] Plant Tissue Culture, also called “micropropagation”, is the propagation of plants from different tissues (or explants) in a shorter time than conventional propagation, making use of the ability that many plant cells have to regenerate a whole plant (totipotency).There are two alternative mechanisms by which an explant can regenerate an entire plant, namely organogenesis and somatic embryogenesis. Since the last decades, the number of higher terrestrial plants species from which these techniques have been successfully applied has continually increased. However, few attempts have been carried out in marine plants. Previous seagrasses authors have focused their studies on i) vegetative propagation of rhizome fragments as explants in Ruppia maritima, Halophila engelmannii, Cymodocea nodosa and Posidonia oceanica; ii) culture of meristems in Heterozostera tasmanica, C. nodosa or P. oceanica; and iii) culture of germinated seeds on aseptic conditions, in Thalassia testudinum, H. ovalis, P. coriacea, P. oceanica, and H. decipiens. All these studies determine the most adequate culture medium for each species (seawater, nutrients, vitamins, carbon sources, etc...), often supplemented with different plant growth regulators and the necessary conditions for the culture maintenance, such as light and temperature. On the other hand, several studies have previously established protocols for cell or protoplast isolation in the species Zostera marina, Z. muelleri, P. oceanica, and C. nodosa, using shoots collected from natural meadows as original vegetal source, but further cell growth was never accomplished. Due to the absence of somatic embryogenesis or organogenetic studies in seagrasses we wonder: IS THE SUCCESSFUL APPLICATION OF TISSUE CULTURE TECHNIQUES POSSIBLE IN SEAGRASSES?

Repoblando nuestras costas: propagación in vitro de la fanerogama marina Cymodocea nodosa (Cymodoceae)

[ES] Cymodocea nodosa (Ucria) Ascherson es una fanerógama marina que crece en fondos arenosos bien iluminados, dando lugar a las praderas submarinas (sebadales), hábitat que tiene una importante función ecológica y repercusiones económicas, por su beneficio para las poblaciones de peces. Las actividades humanas en el litoral amenazan a las comunidades de fanerógamas marinas, lo que ha llevado a la regresión de estos ecosistemas y al detrimento de la calidad de sus aguas. De forma natural, la especie sólo responde mediante la propagación vegetativa a estas alteraciones, ya que, estudios sobre la germinación de las semillas en Cymodocea nodosa muestran que, en relación con el alto número de frutos generalmente encontrados en el sedimento, sólo son detectadas un bajo número de plántulas con un rizoma desarrollado, y la viabilidad natural de estas nuevas plántulas es, además, baja. Ante tal situación natural, el empleo de técnicas de micropropagación puede contribuir a las labores que se realizan para la restauración o reimplantación de sebadales. Habiéndose comprobado que existen limitaciones para la propagación in vitro a partir de fragmentos de la planta (ej. rizoma, se ha pensado en incrementar la capacidad germinativa, venciendo i) la dormancia que presenta la semilla, aclimatando en acuarios y transplantando al mar nuevas plántulas, como primera medida, y ii) la inducción de embriogénesis somática, como segunda medida estratégica que asegure la provisión permanente de nuevas plántulas.

Ichthyofauna associated with Cymodocea nodosa meadows in the Canarian Archipelago (central eastern Atlantic): Community structure and nursery role

We carried out 84 trawls in 41 seagrass meadows composed of the phanerogam Cymodocea nodosa at three islands of the Canarian Archipelago, during June to September 2003, in order to describe the associated ichthyofauna (composition, richness, and abundance), to analyze the role that this habitat can play in fish recruitment, and to determine the potential relationship between the spatial structure of the seagrass meadow and the patterns of richness and abundance of the fish assemblage. A total of 8298 individuals were captured. The five most relevant species, in terms of abundance and frequency, were Spondyliosoma cantharus, Diplodus annularis, Syngnathus typhle, Mullus surmuletus, and Pagellus erythrinus. Gran Canaria had the largest species richness (36 species) and mean number of species per sample (8.69 ± 0.49; mean ± SE). Lanzarote had the largest number of individuals (64.83% of the total registered) and mean total abundance per sample (168.39 ± 30.91). High densities of individuals were registered (95.86 ± 13.5) and 92.91% of fishes were juveniles. Our data showed that the physical configuration of the seagrass meadows did not significantly affect the patterns of richness and abundance of the associated fish assemblage. In conclusion, the C. nodosa meadows exhibited a singular ichthyofauna and they contribute to the maintenance of the diversity of the coastal fish assemblages in the Canarian Archipelago. This habitat constitutes, during spring and summer, a nursery habitat for juvenile fishes of many species, several of them commercially targeted.

Propagación in vitro de Cymodocea nodosa para su utilización en la restauración de sebadales

[ES] Las técnicas de propagación in vitro son consideradas como una de las soluciones más plausibles al declive de las comunidades de fanerógamas que actualmente se registra en todo el mundo. En este trabajo, se establecieron cultivos de Cymodocea nodosa, a partir de explantos, que mediante multiplicación vegetativa o formación de callo previo emitieron hojas nuevas en medios que contenían la citoquinina TDZ. Otros reguladores afectaron a la extensión y la regeneración de la hoja. Los fragmentos, constituidos por hoja, rizoma y raíz, se comportaban como una unidad fisiológica, donde el carbono fijado por la hoja era rápidamente traslocado al resto del tejido. Estos explantos asimilaron preferentemente el amonio y el fosfato inorgánico, siendo indispensable la presencia de tejido sumergido para mantener los niveles de fósforo.