LA SIMBIOSIS ALGAL EN ELYSIA TIMIDA RISSO 1818. PRIMEROS RESULTADOS

Preliminary ecological, microstructural and metabolical results are presented of a study on the symbiotic relationship between the Saccoglossan Opisthobranch Elysia timida, from the Mar Menor hypersaline lagoon (Murcia. SE Spain), and its algal chloroplasts. The intimate metabolical relationship is demonstrated from different points of view and using different techniques: cytological study through electron microscopy; primary production of the chloroplasts through the measure of the produced oxygen and of the incorporated I4C, etc. Some data on the biology of the species in its lagoon habitats complete the paper, which closes with a consideration on the work to be still done on the subject.Se presentan los primeros datos acerca de la simbiosis del opistobranquio sacogloso Elysia timida, relativamente abundante en la zona litoral del Mediterráneo ibérico y muy abundante en el Mar Menor (de donde proceden los individuos estudiados), con cloroplastos algales. La íntima relación metabólica de la simbiosis se demuestra desde diferentes enfoques y aplicando técnicas diversas: estudio citológico mediante microscopía electrónica; producción primaria de los cloroplastos a partir de la medida del oxígeno desprendido y del 14C fijado, etc. Los datos de metabolismo se acompañan de algunas consideraciones sobre la biología de la especie en el Mar Menor, y el artículo termina listando las grandes líneas de investigación que sobre el tema de la simbiosis cloroplasto-sacogloso siguen planteadas

Cartografía bionómica del poblamiento bentónico de las islas del Mar Menor. 1: Islas Perdiguera y del Barón.

Bionomic cartography of the benthic assem blages of the Mar Menor lagoon islands. 1: Perdiguera and Barón islands. The bionomic composition and cartography is given of the hard and soft bottoms of two of the islands of the Mar Menor lagoon, an hypersaline water basin on the SE Spain coast. The tittoral wnation etages are narrow (because of the reduced hydrodynamism), reduced in number (the circalittoral etage laeks due to lhe lagoon shallowness) and of empoverished faunistie and floristie composition when compared with the neighboring Mediterranean ones (because of the environmenta1 stresses associated to an hypersaline lagoon environment). The rocky substrates are also reduced in extent, and lhere are virtually no sciaphi1ic communities. In general, lhe benthie assemblages are those eorresponding to the euryhaline and eurytherma1 lagoon community of PÉRES & PICARD ( 1 964), bul the large size of lhe lagoon and i lS increasing water exchangc with the Mediterranean have somewhat diversified the benthic communities, which now lie half way between the typically marine and those proper of Mediterranean coastal lagoons. The main communities are those dominatcd by macrophytes on 50ft bOlloms (infralittoral etage): the meadows of Cau/erpa prolifera and of Caulerpa-Cymodocea on muddy bonoms, and those of Cymodocea nodosa on sandy ones. PhOlOphilic algae communities, of varying but tinúted composition, are restricted to the hard bottoms.Bionomic maps and represenlative transects of these two islands bottoms are given; the other islands of the lagoon will be dealt with in a fortheoming paper, where the overall bionomic features of the lagoon benthic eommunities wiU be treated.B ionomic cartography of the benthic assem blages of the Mar Menor lagoon islands. 1: Perdiguera and Barón islands. The bionomic composition and cartography is given of the hard and soft bottoms of two of the islands of the Mar Menor lagoon, an hypersaline water basin on the SE Spain coasl. The tittoral wnation etages are narrow (because of the reduced hydrodynamism), reduced in number (the circalittoral etage laeks due to lhe 1agoon shallowness) and of empoverished faunistie and floristie eomposition when compared wilh the neighboring Mediterranean ones (because of the environmenta1 stresses associated to an hypersaline lagoon environment). The rocky substrates are also reduced in extent, and lhere are virtually no sciaphi1ic communities. In general, lhe benthie assemblages are those eorresponding to the euryhaline and eurytherma1 lagoon community of PÉRES & PICARD ( 1 964), bul the large size of lhe lagoon and i lS increasing water exchangc with the Mediterranean have somewhat diversified the benthic communities, which now lie half way between the typically marine and those proper of Mediterranean coastal lagoons. The main communities are those dominatcd by macrophytes on 50ft bOlloms (infralittoral etage): the meadows of Cau/erpa prolifera and of Caulerpa-Cymodocea on muddy bonoms, and those of Cymodocea nodosa on sandy ones. PhOlOphilic algae communities, of varying but tinúted composition, are restricted to the hard bottoms.Bionomic maps and represenlative transects of these two islands bottoms are given; the other islands of the lagoon will be dealt with in a fortheoming paper, where the overall bionomic features of the lagoon benthic eommunities wiU be treated

GRUPOS DE ESPECIES ASOCIADAS EN LOS MOLUSCOS BENTÓNICOS DE FONDOS DUROS DEL LITORAL CATALÁN

From the data of the PROGRAMA DE BENTOS (1972-74) samples, corresponding to six localities on the Catalan coast (Mediterranean Sea, hard substrates between O and 40 m in depth), the presence of groups of ecologically associated molluscan species is studied. Two methods have been used: a similarity index between species and a principal component analysis. Of the formed groups, some have a clear ecological or bionomic meaning, whereas others are not easy to interpret. The reduced number of species used in the analyses (only 56 of the total 189 in the similarity index, and only 21 in the principal component analysis) is the main factor blumng somewhat these results. The meaning of the obtained groups is discussed; they are also compared with the molluscan groups found in other studies: that of the benthos of Medes lslands (one of the previously studied localities), and of other Mediterranean littoral areas.A partir de los datos procedentes de los muestreos del PROGRAMA DE BENTOS (1972-74) se analiza la formación de grupos de especies ecológicamente asociadas, obtenidos mediante el análisis de los inventarios elaborados a lo largo del citado programa. Se han empleado dos métodos: el cálculo de índices de afinidad entre especies, por un lado, y el análisis de componentes principales, por otro. Se forman grupos de especies asociadas, algunos con claro sentido ecológico y10 bionómico, y otros apenas entrevistos. Existe una cierta limitación de los resultados atribuible al número de especies consideradas (únicamente 56 de las 189 obtenidas en total se utilizaron en el cálculo de los índices de afinidad, y sólo 21 en el análisis de componentes principales, en los dos casos atendiendo al mayor número de presencias en los inventarios). Se discute el significado de tales grupos y se comparan éstos con los obtenidos en estudios más recientes; uno de ellos corresponde a los moluscos de una sola de las localidades previamente estudiadas (las islas Medes), y los otros a distintas regiones litorales mediterráneas

EVOLUCIÓN DE LAS CARACTERÍSTICAS AMBIENTALES y DE LOS POBLAMIENTOS DEL MAR MENOR (MURCIA, SE DE ESPAÑA)

Since its formation, the Mar Menor has been subjected to a sequence of transformations as a result of both normal events and the increasing pressures of human settlements. The environmental characteristics and communities evolution reconstruction through the time, by means of the scarce and scattered bibliography and the results obtained by the marine biology team in wich the authors are inc1uded, are presented in this paper.Desde su constitución, el Mar Menor ha estado sometido a una serie de transformaciones como consecuencia de fenómenos naturales y de su propia evolución lagunar para más adelante sufrir las presiones derivadas de la colonización humana y sus actuaciones directas o indirectas en su entorno. Se presenta la reconstrucción de las características ambientales y de los poblamientos del Mar Menor y su evolución en el tiempo, basados en la escasa y dispersa bibliografía disponible y en los resultados obtenidos por el equipo de biología marina en el que se encuadran los autores