Search

The aim of this study was to evaluate compositional differences between harpacticoid (Crustacea, Copepoda) assemblages at two widely separated abyssal locations. During the DIVA 1 cruise of RV METEOR (July/August 2000) to the Angola Basin (Southeast Atlantic), two deep-sea stations, approximately 300 nautical miles apart (Stations 325 and 346), were sampled repeatedly by Multicorer (MUC). For quantitative analyses, 5 MUC samples were selected at random from each of 15 deployments at both stations, totalling 75 cores. Across the study, 7,081 Harpacticoida specimens were encountered and of these 31.4 % were adults and could be analysed to species level: 682 species were identified, with 99.3 % new to science. At northern Station 346, a total of 600 species were recorded—the highest harpacticoid species number ever recorded for a single deep-sea locality. Most species (56 %) were represented by singletons. Multivariate tests identified significant differences between community compositions at the two stations. Diversity, species richness and species density were higher at Station 346, whilst taxonomic distinctness, evenness, and rarefaction were similar between stations. Regression and correlation analyses showed that the difference in species diversity was best explained by species densities rather than species richness. Under-sampling due to low densities was an issue at the southern Station 325. Nevertheless, our study demonstrated significant differences in regional-scale harpacticoid community structures within a single deep-sea basin that would usually be considered a uniform and stable habitat. These observed differences are thought to reflect differences in food availability at the two stations.

A new species of the new genus Keraia gen. nov. from the Guinea Basin is described in the present paper. The new taxon belongs to the Pseudomesochrinae Willen, 1996, which until now has contained only the genus Pseudomesochra T. Scott, 1902. Both genera are prevalent in the deep sea. Whereas Pseudomesochra reaches quite high individual and species numbers in the investigated samples of the DIVA 1, DIVA 2 and ANDEEP deep-sea expeditions, Keraia is found only occasionally and as single specimens. Keraia is characterised among others by a modified antenna exopodite and the shape of P1. Pseudomesochra on the other hand can still be identified as a monophylum by specialised setation on the P1 endopodite and the lack of the inner setae of the first segment of swimming leg exopodites. Other species of Keraia gen. nov. are K. longiseta (Vasconcelos, George & Santos 2008) and the type species K. tamara (Smirnov, 1946). The available records implicate a widespread occurrence of Keraia gen. nov. from the northern to the southern Atlantic, and even reaching both northern and southern polar regions. Up to now all individuals that have been found occur exclusively at deep-sea sites and in very low abundances.

The species diversity of Copepoda Harpacticoida in the deep sea of the Angola Basin (DIVA I expedition with RV Meteor) and in the Weddell Sea (ANDEEP II expedition with RV Polarstern) have been investigated. From the obtained multicorer samples two female specimens of Bathypsammis Huys & Gee, 1993 were collected. The only specimen known before was described as Psammis longifurca by Bodin in 1968 from the northern Atlantic. In the present paper a new species Bathypsammis polaris sp. n. from the Antarctic Weddell Sea is described. The monophyly of Bathypsammis within the Paranannopinae Por, 1986 can be confirmed by several new autapomorphies whereas the relation to other paranannopid taxa must remain open for the moment. The new findings implicate a widespread distribution of Bathypsammis from the northern to the southern Atlantic and even to the southern polar regions. Up to now all individuals that have been found occur exclusively at deep-sea sites and in very low abundances.

A new species of harpacticoid copepods, Xylora calyptogenae spec. n., from Edison Seamount, a hydrothermally active submarine volcano in the New Ireland Fore-Arc system (Papua New Guinea) is described. The new species belongs to the Donsiellinae Lang, 1944, a highly specialised taxon, the members of which have previously been encountered only in association with decaying wood and/or wood-boring isopods. A closer relationship of the Donsiellinae with the Pseudotachidiidae Lang, 1936, can be stated on the basis of characteristics concerning the setation and/or segmentation of A1, A2, Mxl, Mxp, the shape of the female P5, anal somite, sexual dimorphisms on P2 and P3 and missing caudal seta I. Within the Pseudotachidiidae, the Donsiellinae again can be well characterized, e.g. by the setation and segmentation of A2, Mxl, swimming-legs, the shape of P1, female P5, male P2, sexual dimorphism and male P5. The Donsiellinae share some apomorphies with the pseudotachidiid subtaxon Paranannopinae Por, 1986: setation/segmentation of Mx, P1, A1. X. calyptogenae spec. n. is more closely related to Xylora bathyalis Hicks 1988 living in the deep sea wood substrata in New Zealand waters. Some traits of the evolutionary history of the Donsiellinae become evident, probably starting from the more primitive deep sea taxa X .calyptogenae spec. n., which lives in the hydrothermal seafloor in the absence of decaying wood, and X. bathyalis, which is found in decaying wood but not necessarily associated with the wood-boring isopod Limnoria Leach, 1814, towards the more advanced genera such as Donsiella Stephensen, 1936, which invades shallow waters and, further, clings to Limnoria, forming a close and, for the copepod, probably obligatory association. The specialised mouthparts of X. calyptogenae spec. n. seem to facilitate the grabbing and fixing of larger and/or active food items. This is confirmed by the presence of a large prey organism, presumably a copepod, consumed either alive or dead, in the gut of one of the available specimens. This morphology of the mouthparts is also shared by the closely related X. bathyalis.

A new species of harpacticoid copepod, Stenhelia gundulae (Stenheliinae), is described from Edison seamount, a hydrothermal active submarine volcano in the New Ireland Fore-Arc system (Papua New Guinea). Some species groups are identified within the genus Stenhelia. The new species is assigned to the ‘S. normani group’, which is characterized within a more inclusive taxon by the male P5 exp being fused to the basis and lacking two outer spines. The species most closely related to S. gundulae s.n. appear to be S. giesbrechti T. and A. Scott, 1896, S. tethysensis Monard, 1928 and S. normani T. Scott, 1905 including its former subspecies S. polluta Monard, 1928 and S. acutirostris Willey, 1935. The other known deep sea species of Stenhelia, S. noodti Schriever, 1982, S. islandico Schriever, 1982, S. lima Becker and Schriever, 1979 and S. diegensis Thistle and Coull, 1979, on the other hand belong to a different lineage, the ‘S. longicaudata group’ which is characterized by the apomorphic shape of the P1. It ...

A new species of the genusPseudotachidius T.Scott, 1898 from Potter Cove on King George Island, South Shetland Islands, Antarctica is described. It is confirmed that the genusPseudotachidius can be separated into two groups: thesimilis- and thecoronatus-group due to the shape of the PI, the rostral setation, a modified Mxp and the female P5.Pseudotachidius jubanyensis sp. nov. is the first representative of the genus to be found in such shallow waters (20 m depth). The characterization of the site as a low energy soft bottom habitat gives rise to the assumption that in Antarctic shallow waters members of the mainly deep-sea genusPseudotachidius encounter suitable conditions. Despite its low individual numbersPseudotachidius jubanyensis nearly outranges all other harpacticoid copepods regarding biovolume per sediment surface unit because of its large body size. Therefore it tends to play an important role in the benthic meiofauna community.

Three new species of the genusPseudomesochraT. Scott 1902 from the Antarctic Weddell Sea and the Arctic Laptev Sea are described. The male CV stage specimen ofPseudomesochra meridianensis s.n. found in the Weddell Sea is regarded as the first true record of a male ofPseudomesochra. It is shown that the genus has to be removed from the family DiosaccidaeSars 1906 and instead has affinities with the ParanannopidaePor 1986. The Paranannopidae includingPseudomesochra share a Mxp with only 2 syncoxal and 1 basal seta, a deeply incised anal somite with a pseudoperculum instead of a well developed anal operculum, a lost or vestigial caudal seta I, a similar structure of the female genital field and a segmental apophysis on the male P3 enp2, a non-prehensile and 2-segmented Plenp, only 4 endopodal setae and a spine-like pinnate seta on the proximal syncoxal endite of the Mx. The latter 3 characters seem to separate the Parannopidae from closely related taxa of the thalestrid subfamilies Pseudotachidiinae sensuLang 1936 and DonsiellinaeHicks 1988. Showing several autapomorphies,Pseudomesochra has an isolated position within the Paranannopidae, therefore a new subfamily Pseudomesochrinae is proposed containing only the type genusPseudomesochra. An amended key to the species is given.

Two new genera of the harpacticoid family Laophontidae from the high Antarctic Weddell Sea are described. At present, both taxa cannot be assigned to any of the known genera or lineages of the family. The Antarctic shows the greatest degree of endemism worldwide in several already investigated taxa and, considering the available records, the Laophontidae appear to be no exception to this rule. The available data on the Laophontidae of the Weddell Sea seem to support a hypothesis of an ‘old’ antarctic fauna rather than a recolonization by ‘phylogenetic younger’ taxa after the major climatic changes, which took place in the Antarctic continent and the surrounding waters from the Miocene onwards.

Male and female of a new genus and species of the family Laophontidae, Archilaophonte maxima, are described. The specimen was found in the high Antartic (Weddell Sea) and apprears to be the most primitive genus up to now within the superfamily Laophontoidea as defined by Huys (1990). Based on its setation of legs and mouth parts, however, it can be placed unequivocally into the family Laophontidae. Archilaophonte maxima gen. n. shows close affinities to the laophontid genus Esola Edwards 1891. Both genera form a monophyletic group which is interpreted here as the first and most primitive offshot in the evolution of the Laophontidae. The synapomorphies of the former lineage are the shape of the protopodite of the P1 and shape and setation of the female P5.

The species diversity of Copepoda Harpacticoida at several sampling locations in the Southern Atlantic has been investigated. From the obtained multicorer samples, a new taxon of Paranannopinae Por, 1986, Nyxis rostrocularis gen. nov., sp. nov., has been collected, which is described in the present paper. Specimens of the taxon have been encountered in the Angola Basin (DIVA 1 stations 325 and 346), in the Weddell Sea (ANDEEP station 138) and the Cape Basin (DIVA 1I station 36). Nyxis gen. nov. belongs to the group of paranannopid taxa bearing mouthpart aesthetascs. It can be characterised by several autapomorphies discussed in this paper, but takes up a quite isolated position within the Paranannopinae bearing mouthpart aethetascs.

A methodology for comparing repeatedly sampled multicorer stations as to significant differences in alpha diversity of selected cores is presented. This is demonstrated for Harpacticoida of the Angola Basin which were sampled during the DIVA-1 campaign of RV “Meteor” in the year 2000 (M48/1). Two replicatedly sampled multicorer stations were compared as to their species-level alpha diversity values of all adult Harpacticoida in single cores. This was done by a newly developed procedure: based on a rank-ordered alpha diversity matrix, using each a species richness, evenness, and dominance diversity index, a minimum spanning tree test (MST-test) was performed to test for significant diversity differences between the replicates of stations 325 (depth: 5448 m) and 346 (depth: 5389 m). The Canberra Metric was used as a measure of dissimilarity between multicorer deployments. With this procedure, any choice of combination of diversity indices can be made, according to the desired emphasis on certain aspects of diversity. This freedom of choice, together with the possibilities to test for significant diversity differences and to visualize this test, are desirable features of the presented procedure for diversity comparisons. Testing for diversity differences may be useful in the context of conservational purposes when politicians need clear statements from scientists. Due to sufficient replicates, for the first time a significant diversity difference between two abyssal (>2000 m depth) multicorer stations was detectable. Station 346 (eight replicates) was significantly more diverse in harpacticoid species than station 325 (seven replicates). Regional-scale differences in food availability are assumed to be of importance for the different patterns of diversity at stations 325 and 346. The slope of the line of regression in a species/individuals plot on single-core level was not far from 1 ( R 2 = 0.990 ; y = 0.877 x ) , indicating that most species were represented by singletons and the rest only by very few specimens. The data supported scale-dependent differences of harpacticoid diversity in the Angola Basin. Local-scale (between replicates) differences in harpacticoid within-core species diversity were lower than regional-scale (between stations) differences. At least 134 species of Harpacticoida were found at the two stations, of which the subgroups of Pseudotachidiidae, Argestidae, Ameiridae, and Ectinosomatidae turned out to be richest in species and individuals.

Within the multicorer deep-sea samples of the DIVA 1 expedition (METEOR cruise M48/1) some male harpacticoid specimens with strongly reduced mouthparts have been collected, each of them representing a hitherto unknown species. Despite their atrophic mouthparts, they can be identified easily as members of the Paranannopinae Por, 1986 because of showing the characteristic swimming-leg sexual dimorphisms of the latter. In the present paper, a species of Paranannopinae with reduced mouthparts is described for the first time. At the present state of systematic discussion the new species has to be placed within Paranannopus Lang, 1936. Males with atrophic mouthparts have been sporadically described also from other harpacticoid families (such as e.g. Argestidae Por, 1986 and Aegisthidae Giesbrecht, 1892) and the phenomenon is likely to be sexually dimorphic. This kind of sexual dimorphism within harpacticoid copepods combined with enlarged antennular aesthetacs seems to be predominantly a deep-sea phenomenon.