Sobre el origen y la evolución de Peracarida (Crustacea, Malacostraca) de la Antártida

The early separation of Gondwana and the subsequent isolation of Antarctica caused a long evolutionary history of its fauna. Both, long environmental stability over millions of years and habitat heterogeneity, due to an abundance of sessile suspension feeders on the continental shelf, favoured evolutionary processes of preadapted taxa, like for example the Peracarida. This taxon performs brood protection and this might be one of the most important reasons why it is very successful (i.e. abundant and diverse) in most terrestrial and aquatic environments, with some species even occupying deserts. The extinction of many decapod crustaceans in the Cenozoic might have allowed the Peracarida to find and use free ecological niches. Therefore the palaeogeographic, palaeoclimatologic, and palaeo-hydrographic changes since the Palaeocene (at least since about 60 Ma ago) and the evolutionary success of some peracarid taxa (e.g. Amphipoda, Isopoda) led to the evolution of many endemic species in the Antarctic. Based on a phylogenetic analysis of the Antarctic Tanaidacea, Sieg (1988) demonstrated that the tanaid fauna of the Antarctic is mainly represented by phylogenetically younger taxa, and data from other crustacean taxa led Sieg (1988) to conclude that the recent Antarctic crustacean fauna must be comparatively young. His arguments are scrutinized on the basis of more recent data on the phylogeny and biodiversity of crustacean taxa, namely the Ostracoda, Decapoda, Mysidacea, Cumacea, Amphipoda, and Isopoda. This analysis demonstrates that the origin of the Antarctic fauna probably has different roots: an adaptive radiation of descendants from old Gondwanian ancestors was hypothesized for the isopod families Serolidae and Arcturidae, an evolution and radiation of phylogenetically old taxa in Antarctica could also be shown for the Ostracoda and the amphipod family Iphimediidae. A recolonization via the Scotia Arc appears possible for some species, though it is not very likely (some Isopoda, like the Sphaeromatidea, are widely distributed in the Subantarctic, but rare in the high Antarctic). However, it could also be that the species of this family and others were not able to survive when the ice reached the sublittoral shelf in the high Antarctic during glacial periods.La separación de Gondwana y el subsecuente aislamiento de la Antártida dió lugar a la larga historia evolutiva de su fauna. La larga estabilidad ambiental a lo largo de millones de años y la heterogeneidad de hábitats, debida a una abundancia de suspensívoros bentónicos sésiles en la plataforma continental, favorecieron los procesos evolutivos de los taxones “preadaptados”, como por ejemplo los Peracarida. Este taxón, que desarrolló mecanismos de protección de las crías, es muy exitoso (abundante y con una elevada diversidad) en la mayoría de los ambientes acuáticos y terrestres, inclusive en desiertos. La extinción de muchos crustáceos decápodos durante el Cenozoico pudo haber permitido a los Peracarida encontrar y explotar nichos ecológicos que quedaron libres. Por tanto los cambios paleogeográficos, paleoclimatológicos y paleohidrográficos ocurridos desde el Paleoceno (como mínimo desde hace 60 millones de años) y los procesos evolutivos de algunos taxones de Peracarida (por ejemplo Amphipoda e Isopoda) condujeron hacia la evolución de bastantes especies endémicas en la Antártida. Basándose en el análisis filogenético de los Tanaidacea antárticos, Sieg (1988) demostró que la fauna de Tanaidacea de la Antártida está representada principalmente por taxones filogenéticamente jóvenes; datos de otros taxones de crustáceos llevaron a Sieg (1988) a la conclusión de que la fauna reciente de crustáceos antárticos debe ser comparativamente joven. Estos argumentos han sido reexaminados basándose en los datos más recientes sobre la filogenia y biodiversidad de los taxones de los siguientes crustáceos: Ostracoda, Decapoda, Mysidacea, Cumacea, Amphipoda e Isopoda. Este análisis demuestra que el origen de la fauna antártica probablemente tiene diferentes raíces: se ha planteado la hipótesis de una radiación adaptativa de los descendientes de antiguos ancestros de Gondwana para las siguientes familias de Isopoda: Serolidae y Arcturidae; los Ostracoda y la familia de Amphipoda Iphimediidae, podrían mostrar también una evolución y radiación de taxones filogenéticamente antiguos en la Antártida. La recolonización a través del Arco de Escocia parece posible para algunas especies, aunque no es muy probable (algunos, como los Sphaeromatidea están ampliamente distribuidos en las zonas subantárticas, pero raramente en la alta Antártida). Por otro lado, también sería posible que las especies de esta familia y de otras, no hayan sido capaces de sobrevivir en las situaciones en que el hielo alcanzaba la plataforma sublitoral en la alta Antártida durante los períodos glaciales

Composition of the abyssal infauna of the Kuril–Kamchatka area (NW Pacific) collected with a box corer

During the German–Russian KuramBio (Kuril–Kamchatka Biodiversity Studies) expedition with the RV Sonne from July to September 2012, a 0.25 m2 box corer was used to sample the benthic fauna of the Kuril–Kamchatka area. 23 cores were deployed at 12 stations, and in total 36,648 individuals could be identified from a combined surface area of 5.75 m2. Total faunal densities ranged from 1024 to 16,592 ind. m−2, respectively, for the macrofauna from 436 to 3520 ind. m−2. The fauna was dominated by Nematoda (65%), even though this group and other meiofaunal taxa were only partially retained by the 300 µm screen that was used as the smallest screen for this study. The remaining part of the fauna was dominated by polychaetes (23%), followed by peracarid crustaceans (6%) and molluscs (3%). Most of the collected taxa occurred very patchily. Over 80% of the animals were extracted from the upper 2 centimeters of the sediment. Compared to other regions of the Pacific the density of the benthic fauna was unusually high. At the upper slope of the continental margin of the trench and at the southern part of the area the benthic fauna was most taxon rich. Station 3 from the continental slope of the trench was also most rich in terms of faunal density (total numbers of ind. m−2), followed by the station 11 and 12 from that the southernmost part of the abyss. Although the Kuril–Kamchatka area has been sampled on several expeditions during the last century, and some studies on the biomass of the benthic fauna have been published, this study offers the first quantitative community analysis of the benthic fauna in terms of abundance and taxon richness

(Anti-)Control in German: evidence from comparative, corpus- and psycholinguistic studies

The present investigation targets the phenomenon commonly called control. Many languages including German and Polish employ non-finite clauses (besides finite clauses) as propositional complements. The subject of these complement clauses is left unexpressed and must generally be interpreted co-referentially with the subject or object of the matrix clause (subject or object control). However. there are also infinitive-selecting verbs that do not allow for a co- referential interpretation of the embedded subject - semantically, the embedded infinitives of these anti-control verbs are thus less dependent on or less unifiable with the matrix proposition. In Polish anti-control constructions, non-finite complements are overtly marked with the complementizer zeby, suggesting that they are structurally more complex (namely. containing a C-projection) than the non-finite complements in control constructions lacking zeby (modulo special contexts. viz. 'control switch'). In a comparative perspective, the paper brings corpuslinguistic and experimental evidence to bear on the question whether surface appearances notwithstanding, the infinitival complements of anti-control verbs in German should similarly be analyzed as truly sentential, i.e., C-headed structures

Harpacticoida (Crustacea, Copepoda) across a longitudinal transect of the Vema Fracture Zone and along a depth gradient in the Puerto Rico trench

The aim of this study was the investigation of abundance, composition and biodiversity of benthic deep-sea Harpacticoida (Crustacea, Copepoda) in the Verna Fracture Zone (VFZ) and Puerto Rico trench. The study revealed a clear East-West gradient in total abundance of Harpacticoida with a westward decrease in abundances in the VFZ and significant differences in the community composition in the Eastern (East Verna) and Western Atlantic basin (West Verna) on family and genus level. The Puerto Rico trench and its upper slope did not only differ in abundance, but were distinct with respect to community composition on family and genus level. Thus, the upper slope might be considered as an ecotone, a transition zone where a rapid distinction of species composition occurs. In our study fiarea, 837 adult harpacticoid specimens could be assigned to 16 families and 1 subfamily. The most abundant families found were Ameiridae Boeck, 1865, Pseudotachidiidae Lang, 1936 and Ectinosomatidae Sars, 1903. Genera and species were investigated within selected families (Argestidae Por, 1986, Cletodidae T. Scott, 1905, Canthocamptidae Brady, 1880 and Zosimeidae Seifried, 2003) where 11 genera, and 73 species could be discriminated. Within the selected families, the genera Zosime Boeck, 1873 and Mesocletades Sars, 1909 were dominant. In the study area, a high number of singletons was detected, which might be endemic to the respective region. Furthermore, a low total number of species in the trench was observed which was attributed to frequent disturbances in the dynamic environment of the Puerto Rico trench (e.g. turbidites or seismic activity) and high adaptability of specialists and opportunists to these disturbances

The effects of depth, distance, and the Mid-Atlantic Ridge on genetic differentiation of abyssal and hadal isopods (Macrostylidae)

The largest habitat on Earth, the abyssal oceans below 3500 m depth, is commonly assumed to represent a continuous environment due to homogeneity of environmental factors and the lack of physical barriers. Yet, the presence of bathymetric features, such as Mid-Ocean Ridges, and hadal trenches provide a discontinuation. During the Vema-TRANSIT expedition in 2014/2015 to the tropical North Atlantic, a transatlantic transect was studied following the full extent of the Vema Fracture Zone in an east-west direction and including the Puerto Rico Trench (PRT). The aim of this study was to test whether large bathymetric features represent barriers to dispersal and may lead to differentiation and eventually speciation. In this study, these potential barriers included the Mid-Atlantic Ridge (MAR) and the transition (similar to 3000 m) from the hadal PRT to the adjacent abyss. Genetic differentiation and differences in community structure (species composition) from east and west of the MAR, as well as abyssal and hadal depth zones were tested for using the poor dispersers Macrostylidae (Crustacea, Isopoda) as a model Distribution patterns showed that certain macrostylid species have ranges extending more than 2000 km, in some cases across oceanic ridges and trench-abyss transitions. Contrastingly, there was a clear signal for geographic population structure coinciding with the east-west division of the Atlantic by the MAR as well as with the abyss-hadal zonation. These results support the hypotheses that depth gradients as well as oceanic ridges reduce dispersal even though barriers may not be absolute. Additionally, positive correlation between genetic- and geographic distances showed that the vast size of the deep sea itself is a factor responsible for creating diversity

La biogeografía de Crustacea y Mollusca de las regiones Subantártica y Antártica

The Joint Magellan Victor Hensen Campaign in 1994 focused on the biogeographic relationships of the Antarctic and Magellan fauna. The Peracarida and Mollusca sampled at 18 stations in the Beagle Channel by means of an epibenthic sledge were compared with the knowledge about the distribution of species data from the Falkland Islands, South Georgia, Antarctica and the Kerguelen. Peracarida were an important fraction of the macrobenthos and sampled in high numbers. About 105,000 individuals were collected with the epibenthic sledge. Until now about 40 species of Amphipoda, about 42 species of Isopoda, 24 species of Cumacea, eight species of Mysidacea, and 16 species of Tanaidacea were found. 118 mollusc taxa were identified, nine species of Aplacophora, 52 of Gastropoda, five of Scaphopoda and 52 of Bivalvia. Although the species present different distribution trends, the zoogeographic comparison for six larger taxa (four Mollusca and two Peracarida) showed that the species similarities decreased from the Magellan region towards the Falkland Islands and from South Georgia to Antarctica. The Magellanic Gastropoda showed similarities with the fauna of the Falkland Islands and South Georgia (31-37 %), whereas the Bivalvia were more similar to the Antarctic fauna (29 %). With regard to Crustacea, 10% of Antarctic Isopoda species were also found in the Magellan region; the Weddell Sea and East Antarctica, and South Georgia and the Antarctic Peninsula shared most species of both Cumacea and Isopoda, whereas the lowest similarities were shown between Bellingshausen and Weddell Sea for the Isopoda, and interestingly between the Magellan region and South Georgia for the Cumacea. The highest degree of endemism of the Isopoda and Cumacea was found in the Magellan region, where as a consequence of the opening of the Drake Passage many new species seem to have evolved in these taxa.La campaña multidisciplinar realizada en el año 1994 a bordo del “Victor Hensen”, se enfocó al estudio de las relaciones biogeográficas entre la fauna de la zona magallánica y la Antártida. Se compararon los datos obtenidos a partir del muestreo de peracáridos y moluscos llevado a cabo en 18 estaciones en el Canal del Beagle mediante un patín epibentónico, con los datos existentes sobre la distribución en las Islas Malvinas, Georgia del Sur, Kerguelen y la Antártida. Los peracáridos representaron una fracción importante del macrobentos y se muestrearon en grandes cantidades. Se colectaron alrededor de 105.000 especímenes con el patín epibentónico. Hasta ahora se han encontrado alrededor de 40 especies de anfípodos, cerca de 42 especies de isópodos, 24 especies de cumáceos, 8 especies de misidáceos y 16 especies de tanaidáceos. Se identificaron 118 taxones de moluscos, 9 especies de aplacóforos, 52 especies de gastrópodos, 5 especies de escafópodos y 52 especies de bivalvos. Aunque las especies presentaron patrones de distribución muy diferentes, la comparación zoogeográfica realizada con 6 taxones (4 moluscos y 2 peracáridos) muestra, en el caso de moluscos, que la similaridad entre especies disminuye desde la región magallánica hasta las Islas Malvinas y desde Georgia del Sur hasta la Antártida. Los gasterópodos magallánicos muestran similaridad con la fauna de las Islas Malvinas y Georgia del Sur (31-37 %), mientras que los bivalvos fueron más similares a los pertenecientes a la fauna antártica (29 %). En relación a Crustacea, 10 % de las especies de isópodos antárticos fueron también encontrados en la región magallánica. El Mar de Weddell, la Antártida oriental, Georgia del Sur y la Península Antártica compartieron la mayoría de las especies de cumáceos e isópodos; similitudes más bajas se mostraron entre los isópodos de Bellinghausen y el Mar de Weddell, e interesantemente para los cumáceos entre la región magallánica y Georgia del Sur. El alto grado de endemismo de los isópodos y cumáceos de la región magallánica señalaría a este taxón como un foco de radiación con especies que evolucionaron in situ despues de la apertura del Paso de Drake