Sublittoral Harpacticoida ( Crustacea , Copepoda ) from the Magellan Straits and the Beagle Channel ( Chile ) . Preliminary results on abundances and generic diversity *

Samples of meiofauna were collected with a Multicorer during the “Magellan ‘Victor Hensen’ Campaign” of RV ‘Victor Hensen’ in 1994 at 62 stations along the Magellan Straits and the Beagle Channel. Seventeen samples were analysed in the framework of a larger project. Only 69 species of Harpacticoida are known from Chile so far, all of them inhabiting the littoral zone. The “Magellan Campaign” of RV ‘Victor Hensen’ provided the first opportunity to obtain sublittoral samples of meiobenthos of Chilean coasts. In these samples the Copepoda were represented by 4 of its orders: Calanoida, Cyclopoida, Poecilostomatoida and Harpacticoida, the latter exhibiting the highest abundances. Representatives of 19 harpacticoid families (6 of which are new for Chilean waters) were identified in the samples. The species found in 15 of these families belong to 28 genera of which 18 are new to the Chilean fauna. With respect to taxa composition and distribution, the following preliminary results can be presented: the number of new families and new genera for the southern tip of South America increased considerably; a relatively high similarity between the Magellan Straits/Beagle Channel and areas of corresponding northern latitudes can be observed; the Magellan Straits and Beagle Channel show considerable differences with respect to taxa composition and diversity of the harpacticoid fauna.


INTRODUCTION
Compared with the marine meiofauna of temperate and polar regions of the Northern Hemisphere, the species composition and distribution of the meiofauna in Antarctic and Subantarctic regions are still poorly known.For zoogeographic reasons it is very important to compare the meiofauna of the southern tip of South America with that of the Antarctic.When these two continents started separating as the last of the Gondwanian fragments approximately 30 million years ago (see Brandt, 1991;Arntz, 1996;Winkler, 1994), the Drake Passage opened and the circumpolar currents became established, which led to a significant isolation of the Antarctic continent.Due to the relatively late separation of the two continents and the short distance between them, it is to be expected that faunal exchanges between the two have been more extensive and longer lasting than between the Antarctic and other southern continents (Arntz, 1996).
Whereas the study of High Antarctic meiofauna and in particular of Harpacticoida (Crustacea, Copepoda) has been intensified in the last decade (e.g.Dahms, 1992a, b;Dahms and Dieckmann, 1987;Dahms et al., 1990;George, 1993;Herman and Dahms, 1992;Schminke and Dahms, 1989;Vanhove et al., 1995;Willen, 1995;1996a, b), practical-ly nothing is known on the meiofauna of the southern tip of South America or the Antarctic Peninsula.As regards the Harpacticoida only 69 species are known so far from Chile, having been recorded from the littoral mainly along the coast of northern and central Chile (see George, 1996).Therefore, the "Magellan Campaign" of RV "Victor Hensen" in 1994 was a good opportunity to obtain material from an area poorly investigated so far, not only from the littoral but also from the sublittoral down to several hundred metres depth.
The preliminary results presented here are part of a larger project comparing harpacticoid communities of various parts of the Magellan Region with each other and with those in the Antarctic at the species level.This requires time-consuming taxonomic work because of a very high proportion of new species.This work is still in progress, so the results presented here refer to taxa of higher taxonomic levels.
of each core 30.38 cm 2 ).Thus, at each station a maximum of 4 could be taken.The material of each core was split into 2 fractions: an upper one, comprising the first 5 cm of substrate, and a second one containing the rest of the sampled material.The material was fixed on board with 5% buffered formaldehyde and later centrifuged in Gent (Belgium) for separation of the meiofauna from the substrate.
Copepoda were sent to Oldenburg for further research.The results presented here refer only to the upper fraction (first 5 cm) of each core.Of the 62 stations, 17 have been analyzed (Table 1, Fig. 1).
The copepods have been counted and identified at higher taxonomic levels (orders, families, genera).Identification was done with the aid of a Leitz-Dialux 20 EB stereo microscope, using identification keys from Lang (1948), Wells (1976), Huys et al. (1996) and original literature.

RESULTS AND DISCUSSION
In the material studied, 4 orders of Copepoda were represented: Calanoida, Cyclopoida, Poecilostomatoida and Harpacticoida, which showed the highest abundances varying between 4 and 779 individuals per core.Among Harpacticoida the highest abundances were found in the eastern Beagle Channel, and the lowest in the northern Magellan Straits.
A total number of 19 harpacticoid families has been recorded, 6 of which are new for Chilean waters (Table 2).At the generic level, identifications are still in progress, but so far 28 genera belonging to 15 families have been identified, 18 of them being new for Chile (Table 3).It is to be expected that at the species level the number of new taxa will increase drastically.
One of the aims of the project is the comparison of species composition in the cold temperate region of the Southern Hemisphere with corresponding regions in the Northern Hemisphere.In this context it can be said that at the family level there is a rela-SUBLITTORAL HARPACTICOIDA FROM SOUTHERN CHILE 135 tively high similarity between the "Magellan Straits/Beagle Channel Region" and the northern "Laptev Sea/Barents Sea Region" (Table 4) (additional data by P. Martínez, unpubl.).Of 26 families known from both regions, 15 have been found in the southern as well as in the northern region, whereas 11 families seem to be restricted to one of the two regions.Furthermore, in material from the Patagonian continental shelf (see Arntz et al., 1997) which is not part of this study a few additional families also known from the northern region were detected (Cylindropsyllidae, Peltidiidae, Tegastidae), underlining the above mentioned high similarity.This similarity seems to be valid also at lower taxonomic levels.The genus Ceratonotus Sars, 1909 (Ancorabolidae), the distribution of which seemed to be restricted to the Northern Hemisphere, was also recorded in the Magellan Straits (George and Schminke, 1998).The genus Arthropsyllus Sars, 1909 (Ancorabolidae), which seemed to be restricted to boreal and northern subpolar seas, was found to be represented also in the Beagle Channel (George, 1998).
If the taxa composition in the samples of the Magellan Strait and the Beagle Channel is com-pared, clear differences can be seen between the two areas.At family as well as at genus level 3 groups of taxa can be distinguished; in one group the distribution covers the whole area, whereas two other groups are restricted in their distribution either to the "Magellan Area" or to the "Beagle Area" (Fig. 1).The first group comprises 12 out of the 19 families, whereas the "Magellan group" comprises 4 and the "Beagle group" 3 families (Table 2).At the generic level the differences are even more clearcut.The first group comprises 12 genera, the "Magellan group" 13 genera and the "Beagle group" only 3 (Table 3).The high number of genera in the "Magellan Area" is remarkable and contributes to the high diversity (in the sense of taxa richness) in this area as compared with the "Beagle Area" (Fig. 2).At stations 840-877 in the "Magellan Area" the number of genera in relation to the number of specimens is very high.It will be interesting to see how this relationship will look at the species level employing multivariate analyses, and how distributions and abundances correlate with parameters such as depth, temperature, salinity, granulometry and content of the substrate in organic matter.

TABLE 1 .
-List of the sampling stations studied from the Magellan Straits and the Beagle Channel.The list presents the station number, its locality, geographical position and depth.

TABLE 2 .
-List of harpacticoid families found in the sampled area, including relative abundances (rel.abund.)(in %) of each taxon in the Magellan Straits and/or the Beagle Channel respectively.Taxa restricted to one of the areas indicated by bold names and data.Families marked by an asterisk* are new for the Chilean marine fauna.

TABLE 3 .
136 K.H. GEORGE and H.K. SCHMINKE -List of harpacticoid genera found in the Magellan Straits and/or Beagle Channel.+ = present, -= absent.Taxa restricted to one of the areas indicated by bold names and symbols.Genera marked with an asterisk* are new for the Chilean marine fauna.

TABLE 4 .
-List of harpacticoid families collected in the Magellan Straits/Beagle Channel and the Laptev Sea/Barents Sea, respectively.Presences marked with +, absences marked with -.Taxa restricted to one of the regions indicated by bold names and symbols.Data of the Laptev and Barents Sea after P. Martínez, unpublished.