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Background and aims: Planktonic dinoflagellates have a great ecological significance in marine environments. While some dinoflagellate species commonly reach bloom concentrations and are thus conspicuous components of marine phytoplankton, others occur in very low abundances which make them difficult to detect in field studies. Here we analyzed dinoflagellate composition and abundance in five oceanographic expeditions carried out in continental shelf and slope waters of the Argentine Sea. M&M: Plankton abundance was estimated by the Utermöhl method, using inverted microscopy, whereas further optical and scanning electron microscopy was applied for the identification of dinoflagellate species. Results: We focused on the occurrence of seven dinoflagellates that have been previously poorly documented or overlooked in marine environments worldwide: Dinophysis microstrigiliformis; Gyrodinium sp.; Karlodinium elegans; Oxytoxum laticeps; Peridiniella danica; Peridiniella globosa and Prorocentrum nux. The latest and K. elegans are observed for the first time in field conditions after their original descriptions based on cell cultures. While most species were detected in low or moderate abundances, P. nux, which is the smallest Prorocentrum species, reached 82,000 cells L-1 in slope waters. Very small Gyrodinium cells (11.5 μm long; 8.7 μm wide) with a distribution restricted to slope waters during spring, were not possible to be accurately assigned to a species. Conclusions: This study contributes to the understanding of dinoflagellate diversity in the Argentine Sea and the worldwide distribution of little known species. [ABSTRACT FROM AUTHOR]

Trichopeltarion corallinus (Faxon, 1893), a decapod of the family Atelecyclidae, is recorded for the first time in Chile. Seven specimens were captured by bottom trawling at five sites on the continental slope. All the specimens were associated with hard substrates and at least one was associated with a recently discovered methane seep area. The stations were located between 18° and 42°S and at depths from 507 to 922 m. After its original description, the species was reported for Peru from approximately 10° to 17° S and at depths of 860 to 870 m. This first record of the species for Chile extends its geographic distribution about 25° (about 2,775 km) southwards and expands its bathymetric range as well. Moreover, a male specimen of T. hystricosus was collected at an intermediate latitude (∼22°S) in relation to previous records, thereby confirming the presence of this species and the genus Trichopeltarion over deep hard substrates along the continental slope off Chile. [ABSTRACT FROM AUTHOR]

The pedunculate barnacle Scalpellum projectum Nilsson-Cantell, 1930, was described based on benthic material from a telegraph cable recovered from deep waters off Antofagasta (∼23°S). No new records have been reported for this species worldwide since its original description. Six adult females of S. projectum were collected during recent studies of communities associated with methane seeps. The material was taken from three stations located between 34°42' and 36°22'S and at depths of 846 to 922 m. We provide taxonomic information based on the external morphology of the specimens, whose sizes coincide in general terms with those of the original description. No male specimens were observed; these are smaller, aberrant in form, and live within the scuta in the capitulum of the females. With this second finding, the distributional range of this species, previously only reported for the slope off Chile, is extended about 17° latitude southwards (1,800 km) and its bathymetric range is expanded by 200 m. [ABSTRACT FROM AUTHOR]

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Copyright of Nova Acta Científica Compostelana is the property of Universidad de Santiago de Compostela, Servicio de Publicaciones and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)