Temporal and spatial distribution of the ichthyoplankton in the Canary Islands

A pesar del creciente interés en el estudio de las primeras fases de desarrollo de los peces, aún existen zonas donde esta comunidad es relativamente desconocida. Este es el caso de las Islas Canarias. En la presente tesis, gracias a una serie de muestreos semanales en la región costera de la isla de Gran Canaria durante más de dos años, se ha caracterizado de manera precisa la composición, estructura y variabilidad del ictioplancton presente en esta región subtropical. Clupeidos, Espáridos y Góbidos dominaron la comunidad neríticas, mientras que Mictófidos, Gonostomátidos y Photíctidos prevalecieron dentro de las familias oceánicas. La variabilidad temporal de la comunidad larvaria parece estar más relacionada con la temperatura y efectos a pequeña escala (hidrografía, productividad local, ciclo lunar), que con el aumento de productividad anual durante el bloom de finales de invierno. Se definieron dos asociaciones estacionales de larvas estrechamente ligadas a las características de la columna de agua: (1) invierno-primavera, en la que dominan Sardinella aurita, Boops boops y Cyclothone braueri, y son características especies como Pomacentridae sp1, Trachurus picturatus o Scomber colias; y (2) verano-otoño, donde Góbidos y Cyclothone braueri dominan, pero cuyas especies características son Ceratoscopelus warmingii, Pomacentridae sp2 y Anthias anthias, entre otras. Respecto a la variabilidad horizontal, se confirmó la presencia de dos zonas de retención para los huevos y larvas neríticas a barlovento y sotavento (estela cálida) de la isla. Sin embargo, no se encontraron diferencias significativas en la composición de la comunidad larvaria entre las diferentes zonas de la plataforma de la isla. La Zona de Transición Costera Canario-Africana se caracteriza por una gran actividad de mesoscala, que afectará a la distribución de las larvas neríticas de las costas africanas. Esta interacción resulta especialmente evidente en el caso de las larvas, principalmente sardina y anchoa, transportadas en filamentos de afloramiento generados en la región de Cabo Juby-Cabo Bojador. Estos filamentos pueden ser atrapados por remolinos ciclónicos situados al sur de Gran Canaria. Este sistema remolino-filamento podrá, en función de su evolución, actuar como un mecanismo de retención o dispersión para las larvas de especies neríticas africanas. Parte de estas larvas pueden llegar a las costas de Gran Canaria, suponiendo un aporte para las poblaciones larvarias locales, al menos durante el verano. A pesar de la gran cantidad de información obtenida a partir de esta tesis, es necesario continuar con este tipo de estudios para evaluar la importancia de este transporte larvario y su aplicación a la gestión pesquera.

Planktonic community structure and variability in the Canary Islands waters: the role of microplankton

[ES] En este trabajo hemos contribuido al estudio de la estructura de la comunidad planctónica y a su variabilidad temporal, utilizando un enfoque de end-to-end , desde las bacterias hasta el mesozooplancton haciendo especial énfasis en el microplancton. Nuestro trabajo muestra la importancia de los efectos bottom-up y top-down que regulan la estructura de las comunidades planctónicas.

Reproductive biology of the island grouper (Mycteroperca fusca) in the Canary Islands, northwest coast of Africa

[EN]This is the first time that the reproductive characteristics of Mycteroperca fusca have been analyzed over the whole area of its distribution, using the parameter of the histological analysis of the gonads. This species is a protogynous hermaphrodite with a marked predominance of females (1:4.9). The males and females displayed marked differences in the distribution of the sizes. The females were distributed over all the size ranges analyzed (229-725 mm total length), whereas the males were observed within the larger sizes, as of 428 mm. One transitional specimen (610 mm total length) was observed. The size at which the females first reached sexual maturity was 335 mm total length whereas the size at which 95% of females reached sexual maturity was 398 mm total length. The average size at which 50% of the females had inverted to the male condition was found to be 678 mm total length. The range of sizes at which the process of sexual inversion took place was broad, between 428 and 725 mm total length. The reproductive period was long, almost covering the annual cycle, although the maximum activity was observed between April and October, with a peak in spawning in June-July.

Contribution to the biology and fishery of the deep-water red crab, Chaceon Affinis (A. Milne-Edwards & Bouvier, 1894) (Decapoda, Brachyura, Geryonidae) in deep waters of the Canary Islands (Central-East Atlantic)

[EN] This crab was captured in the whole range of depths sampled, although its highest abundance was found between 600 and 800 m, on muddy-rocky bottoms. Moreover, significant differences were observed in the average weight and length, according to depth of capture, island of origin, and date of survey. In general, the b parameter of length-weight relationship indicates a negative allometric growth pattern, although in some cases it was not statistically different from isometry, particularly in males. Males were heavier, larger, and more abundant in catches than females.

Effect of the Canary Islands in the blockage and mixing of the North Atlantic eastern water masses

[EN] We apply an inverse model to a hydrographic cruise that completely closes the Canary Islands to investigate their effect on the water masses transports. Most central waters are transported south between the eastern islands and the African coast, with 2.5 Sv out of a total of 3.5 Sv. Intermediate waters are effectively blocked by the islands passages, with Mediterranean/Antarctic waters predominantly found north/south of the islands, and most deep waters loop around the archipelago plateau. A process model upholds the existence of intense two-way exchange between central and intermediate waters along the eastern passage, with vertical velocities of order 10 m s.

Phenolic Constituents, Antioxidant and Preliminary Antimycoplasmic Activities of Leaf Skin and Flowers of Aloe vera (L.) Burm. f. (syn. A. barbadensis Mill.) from the Canary Islands (Spain)

[EN]The methanol extracts of leaf skins and flowers of Aloe vera from the Canary Islands were analyzed for their phenolic profiles and screened for their antioxidant and antimycoplasmic activities. The use of reversed phase high performance liquid chromatography (RP-HPLC) allowed the identification of 18 phenolic constituents. Leaf skin extracts were characterized by the abundance of catechin, sinapic acid and quercitrin. Gentisic acid, epicatechin and quercitrin were the most prominent phenolic compounds of the flowers. The in vitro antioxidant activities determined by using the 1,1-diphenyl-2- picrylhydrazyl (DPPH) and ferric antioxidant reducing power (FRAP) assays revealed that both extracts exhibited antioxidant activity, being the leaf skin extract the most active fraction. The leaf skin extract was also found to be active against the microbial strains tested. Therefore, A. vera extracts from leaf skin and flowers can be considered as good natural antioxidant sources.

Do the size shifts of marine macroalgae match the warming trends in the Canary Islands?

Departamento de Biología Vegetal (Botánica), Universidad de La Laguna, La Laguna, Canary Islands

Neogene and Pleistocene fossil brachiopods of the Eastern Islands. Current appointments.

[EN] Numerous specimens of fossil brachiopods have been found in the different fossiliferous outcrops of the Canary Islands. These fossils have been found in the deposits of Mio-Pliocene age of the eastern Canary Islands, described and illustrated in the work of Meco et ali. 2005 and in the outcrops interpreted as a tsunami deposits  in Piedra Alta, Lanzarote, belonging to the Marine Isotope Stage 11 dated to circa 330 ka. 4 species of fossil brachiopods have been identificated: Terebratula sinuous Brocchi 1814, Lacazella mediterranea Risso 1826 Terebratulina caputserpentis (Zbyszewski, 1957) and Thecidium cf . digitatum (Sowerby 1823). These fossils provides stratigraphic and paleoclimatic taxonomic information. Furthermore, in order to compare the fossil brachiopods with present in the Canary Island, a reference collection is defined with specimens obtained from marine sediment surveys at Gran Canaria, La Palma and El Hierro, identifying 3 species: Argyrotheca barrettiatia (Davidson, 1866), Megerlia truncata (Linaeus 1767 ) and Pajaudina atlantica (Logan 1988).