Francisco José García

Quantitative analysis of macrobenthic soft-bottom assemblages in South Shetland waters (Antarctica)

Abstract Macrobenthic assemblages were investigated at 26 stations located around Livingston Island, Deception Island and the Bransfield Strait at depths ranging from 42 to 671 m. Representatives of 30 major taxa were found. The maximal density was 5,260 specimens·m−2 at Livingston Island; the mean abundance per station ranged from 160 to 4,380 specimens·m−2. The total biomass of the macrozoobenthos declined with depth, with mean values of 3,201 g·m−2 at shallower depths (< 100 m) and 210 g·m−2 further down (> 100 m). After multivariate analysis (cluster analysis, MDS) based on Bray-Curtis dissimilarities, most stations could be assigned to one of three groups on the basis of distinct biomass differences between sites. The first cluster with a rich Ascidiacea biomass is common on shallower bottoms. The second, with Ophiuroidea as a characteristic group, is common on deeper bottoms. The absence of an ‘indicator’ taxon is characteristic of the remaining cluster of those stations with the lowest biomass values. No significant correlations were detected between macrobenthic biomass and any sediment parameters measured, probably because part of the benthos (i.e. the epifauna) could be better explained by the coupling with a highly productive water column. The role of the epi-infauna sensu Gallardo as the main factor structuring benthic assemblages in the investigated area is discussed.

Quantitative analysis of soft‐bottom molluscs in the Bellingshausen Sea and around Peter I Island

Macrobenthic soft-bottom molluscs were sampled in 30 stations located in the Bellingshausen Sea at depths ranging from 90 to 3304 m. The samples were collected using a quantitative grab box-corer during the cruises BENTART 03, from 24 January to 3 March 2003, and BENTART 06, from 2 January to 16 February 2006. Molluscs represent 1074 specimens belonging to 62 species of Polyplacophora, Gastropoda, Bivalvia and Scaphopoda. The bivalve Cyamiocardium denticulatum was the most abundant species (448 specimens). The abundance per station varied between 1 and 446 specimens. The Shannon–Wiener diversity index ranged between one specimen and 2.36, the Pielou evenness index ranged between 0.00 and 1 and species richness ranged from 1 to 14 species. Diversity showed great variations at different stations. After multivariate analysis (cluster analysis and nonmetrical multidimensional scaling) based on Bray–Curtis similarities, we were able to separate two principal clusters. The first cluster groups together species from shallower bottoms near Peter I Island and the Antarctic Peninsula, and the second cluster groups together species from deeper bottoms in the Bellingshausen Sea. The combination of environmental variables with the highest correlations with faunistic data was that of depth and coarse sand at the surface.

Males and females gonad fatty acids of the sea urchins Paracentrotus lividus and Arbacia lixula (Echinodermata)

The aim of this study was to analyze male and female gonad fatty acids of two sea urchin species, Paracentrotus lividus and Arbacia lixula, from the south coast of Spain. Additionally, we investigated possible differences between two locations. The ovaries of both species showed higher percentages of 14:0, 16:0, 16:1n-7, 18:2n-6, 18:3n-3 and 18:4n-3 than testes and lower levels of 18:0, 22:1n-9, 20:4n-6 and 22:5n-3. In P. lividus but not in A. lixula, the level of 20:5n-3 was higher in testes than in ovaries. These differences between sexes probably indicate different requirements of males and females during gametogenesis although the presence of a large number of gametes in the mature gonad may also have influences on fatty acid composition. Significant differences in gonad fatty acid profiles where also found when individuals of P. lividus collected at a location of the Mediterranean region were compared with specimens collected at the Atlantic coast. The most remarkable changes were the lower levels of 14:0, 18:1n-7, 20:1n-9, 20:4n-6 and 22:4n-6 and the higher values of 20:1n-11, 20:5n-3 and 22:6n-3 found in males and females of the Mediterranean specimens compared to those of the Atlantic coast. These differences probably reflect the differences in potential food sources at each location.

A descriptive study of some Antarctic notaspidean opisthobranchs (Gastropoda), with description of a new genus and species

During the expedition “ANTARTIDA 9101”, organized by the Spanish Oceanographic Institute to the South Orkney Islands, four specimens of notaspidean gastropods were collected. Three of them have been identified as Bathyberthella antarctica Willan and Bertsch, 1987. However, one specimen, although externally similar to B. antarctica, had an internal anatomy exhibiting features that have enabled us to consider it to be a new genus and species. This new taxon is characterized by the presence of jaws without mandibular elements, and a vaginal gland that partially surrounds the distal region of the vaginal duct. In this paper the new genus and species is described. Additional anatomical data of the specimens of B. antarctica collected during the expedition are also included.

Anatomical and taxonomical studies of the Antarctic nudibranchsAustrodoris kerguelenensis (Bergh, 1884) andA. georgiensis n. sp. from the Scotia Sea

During the expedition “ANTARTIDA 8611” to the Scotia Sea, organized by the Spanish Oceanographic Institute, several specimens ofAustrodoris were collected. Although nearly all have been identified asAustrodoris kerguelenensis (Bergh, 1884), one of them shows some anatomical features, mainly related to the reproductive system, that allows us to identify this specimen as a new species, which we have namedA. georgiensis. Therefore, with the aim of clarifying the taxonomical value of this species, a comparative study of the anatomy ofA. kerguelenensis andA. georgiensis is presented. Some new data on the diet ofA. kerguelenensis are also presented.

FATTY ACID COMPOSITION AND UTILIZATION IN DEVELOPING EGGS OF SOME MARINE NUDIBRANCHS (MOLLUSCA: GASTROPODA: OPISTOBRANCHIA) FROM SOUTHWEST SPAIN

Abstract The fatty acid composition of whole egg masses was investigated in 4 marine nudibranchs collected from the southwest of Spain: Polycera aurantiomarginata, Polycera quadrilineata, Berghia columbina and Berghia verrucicornis. The four species are carnivorous. All nudibranchs were characterized by high levels of n-3 polyunsaturated fatty acids (n-3 PUFA), mainly eicosapentaenoic acid (20:5n-3), docosapentaenoic acid (22:5n-3) and docosahexaenoic acid (22:6n-3). Other major fatty acids were the saturated palmitic (16:0) and stearic (18:0) acids, the monounsaturated oleic acid (18:1n-9) and the n-6 PUFA arachidonic (20:4n-6) and docosatetraenoic (22:4n-6) acids. Relative high percentages of the plasmalogen derivatives 16:0DMA and 18:0DMA were also detected. Univariate analysis showed that egg fatty acids from P. aurantiomarginata and P. quadrilineata significantly differed from those of B. columbina and B. verrucicornis. Higher levels of saturated fatty acids and 22:6n-3 and lower percentages of 18:0DMA, 22:4n-6 and 22:5n-3 were found in the spawns of both species of Polycera as compared with both of Berghia. Analysis of the bryozoon Bugula neritina and the sea anemone Sagartia troglodites, main preys of Polycera and Berghia respectively, showed that the differences observed in egg fatty acid composition were likely related to diet. Fatty acids of the fully developed embryos from P. aurantiomarginata and B. columbina, sampled immediately prior to hatching, were analyzed to investigate the dynamics of fatty acids during embryogenesis. The long chain PUFA 20:4n-6, 22:4n-6, 20:5n-3 and 22:5n-3 increased or remained stable during embryogenesis in both species whereas palmitoleic acid (16:1n-7) in B. columbina and 16:0, 17:0, 18:0 and 18:1n-9 in P. aurantiomarginata decreased. The major n-3 PUFA, 22:6n-3, marked decreased in B. columbina but remained unchanged in P. aurantiomarginata. These data indicate that fatty acids play different roles during embryogenesis and that in both nudibranchs the embryo requirements are not the same.

Ultrastructure of the gametolytic gland and seminal receptacle in Hypselodoris messinensis (Gastropoda, Opisthobranchia)

The gametolytic gland of Hypselodoris messinensis is a voluminous globular structure that encloses a large mass of degenerative gametes, especially waste exogenous sperm. The epithelial cells of this organ show some features characteristic of secretory cells and probably release hydrolytic enzymes into the lumen. The amorphous material accumulated in the gametolytic gland does not appear to be reabsorbed by the lining epithelium.

Description of the antarctic notaspideanPolictenidia tomasi gen.nov. and sp.nov. (Gastropoda, Opisthobranchia) from the Scotia Sea proposing also a new notaspidean tribe

During the expedition “ANTARTIDA 9101”, organized by the Spanish Oceanographic Institute, two specimens of an unknown notaspidean species were collected. These differed considerably from other notaspidean species, mainly by the presence of three gills and a prebranchial sac with large external expansions. Since these specimens have three gills, while members of the order Notaspidea have been described as having only one, this feature is doubly interesting: firstly, from the systematic point of view, the definition of the order has to be modified, and secondly, it generates a phylogenetic discussion of the possible affinity between the notaspideans with one gill and doridaceans, which possess several gills.