Agassiz Trawl Research Articles

Ammothea bigibbosa (Arthropoda, Pycnogonida), a new species of the Antarctic Peninsula waters

A new species Ammothea bigibbosa, collected with the Agassiz trawl in Margarita Bay at 517 m, is described, illustrated and compared with the similar species A. gordonae and A. adunca.

Atyloella tribinicuspidata sp. n. (Crustacea, Amphipoda, Gammaridea, Eusiridae), a common amphipod in benthic communities off Bouvet Island (Southern Ocean)

Atyloella tribinicuspidata sp. n. was obtained and described from Agassiz trawl and dredging samples carried out in waters off Bouvet Island during the FS “Polarstern” ANT XXI/2 expedition in November 2003. Atyloella tribinicuspidata is a very common amphipod species characteristic of the deeper sublittoral, from 122 m to 134 m water depth. Atyloella tribinicuspidata is closely related to A. magellanicus Stebbing 1888, from the Magellan region of southernmost America. This allowed suggesting a speciation process within the genus, which is briefly discussed.

A most isolated benthos: coastal bryozoans of Bouvet Island

Bouvet Island is, uniquely, thousands of km from the next nearest land, even other islands. Its Southern Ocean location, isolation and the exposure of its surrounding cliffs have resulted in only rare visits by ship and its coastal marine fauna is little known. For animal taxa with non-pelagic larvae, such as cheilostome bryozoans, the shelf environment of Bouvet is a rare example of isolated oceanic communities. Agassiz trawl samples of the 2003 ANT XXI-2 cruise of the PFS Polarstern collected a total of 18 species of cheilostomes at four sites around Bouvet Island. Of these only four had been reported before amongst the 20 species of cheilostome previously known from this locality. Furthermore eight of the genera are reported for the first time from Bouvet Island. The assemblages were dominated by Austroflustra vulgaris, and in one case Nematoflustra flagellata. The bryozoan fauna seems to be depauperate and bears only low (32% at species and 46% at genus level) similarity to any location within 3,000 km. Its species composition is typically Southern Ocean, with most affinity to the Scotia Arc and Weddell Sea whereas at generic level it is most similar to the Subantarctic Prince Edward Archipelago.

Poliquetos bentónicos submareales de fondos blandos de la región de Aysén, Chile: Clado Phyllodocida (Annelida, Polychaeta)

Results from a taxonomic analysis of benthic polychaetes of the clade Phyllodocida, obtained during the Cimar-7 and Cimar-8 Fjords research cruises are presented. Synonymy, distribution, morphological remarks, and illustrations for each species are included. The samples were obtained in the region of Aysen, on the southern coast of Chile, from silt-clay bottoms using an Agassiz trawl between 20 and 444 m depth. A total of 119 specimens of polychaetes from the clade Phyllodocida were collected. These specimens consisted of 15 species, grouped into 12 genera and 6 families. One incomplete specimen of Syllidae recovered was included only for the taxonomic record. The samples analyzed included a total of seven species of Polynoidae (46.7% of total abundance of all samples), four species of Nereididae (26.7% abundance) and one each of the Aphroditidae, Sigalionidae, Glyceridae and Nephtyidae (6.7% abundance). During the Cimar-7 cruise a total of 67 specimens of polychaetes were collected, including the sigalionid Leanira quatrefagesi (Kinberg) which accounted for 29.9% of the total abundance. During the Cimar-8 cruise, 52 specimens of polychaetes were collected, in particular Leanira quatrefagesi accounting for 42.3% of total abundance, followed by the polynoid Harmothoe spinosa (Kinberg) with 40.4% abundance. Our findings increased the number of benthic polychaetes recorded for the Aysen region to 66 species.

Melinnopsis angolensis (Annelida: Polychaeta: Ampharetidae), a new species from the Angola Basin

A new species of ampharetid polychaetes, Melinnopsis angolensis sp. nov. is described. It was collected with an Agassiz trawl at seven stations in the Angola Basin in depths between 5385 and 5448 m. The new species differs from the few other species described in this genus by the number of thoracic setigers, the number of enlarged tentacles, presence of reduced notosetae in the anterior thorax, and morphological details of the gills and postbranchial membrane. A brief overview of the other species of the genus is given, and the synonymization of Amelinna and Melinnopsides with Melinnopsis is discussed.

Moluscos marinos intermareales y submareales entre la Boca del Guafo y el estero Elefantes, sur de Chile

A study was made of marine molluscs collected in the fjord region of southern Chile, including the Jacaf and Puyuhuapi channels, Aysen Sound and the Quitralco and Cupquelan fjords. Samples were obtained during the Cimar 7- Fjords research cruise, of 8-20 July 2001. Collections of benthic samples were made between Boca del Guafo and the Elefantes fjord. Samples were taken by hand with an Agassiz trawl from 20 stations at various depths between 0 and 330 m. A total of 22 species were recorded (1 polyplacophoran, 7 gastropod, 12 bivalve and 2 scaphopod). Of these, 19 are described and illustrated, together with new information on habitat and geographical distribution. We report new geographical records for the following seven species: Calliostoma nudiusculum, Calliostoma consimilis, Capulus compressus, Falsilunatia patagonica, Aeneator fontainei, Fissidentalium majorinum and Rhabdus perceptum, six of these are northward extensions of the magellanic molluscan fauna while the record of Aenaeator fontainei is a new southern limit.

Scotia Arc deep-water bivalves: composition, distribution and relationship to the Antarctic shelf fauna

Abstract Agassiz trawl, epibenthic sledge and large box core samples were made in the Scotia and northern Weddell Seas during the 2002 ANDEEP expeditions with R.V. Polarstern at 21 locations (774–6348 m depth). The deep-water bivalve fauna sampled was species rich; in total 40 species of bivalves belonging to 17 families were found. At least seven of these species are new to science. Per location species richness varied from 5 to 15 species. Kelliella sirenkoi was the most common and abundant species, occurring at 17 locations (1121–6348 m), followed by Genaxius sp.1 occurring at 12 locations. The epibenthic sledge hauls were characterised by low abundances, varying from 1 to 68 individuals 1000 m−2 in depths greater than 1000 m. In comparison with the shelf fauna of the Scotia Arc, the deep-water bivalve community showed similar species richness. This indicates that there is no diversity cline with depth in Antarctic bivalves, but it does provide evidence for underestimated species richness in deep water because of lack of sampling.

Ophiuroid community structure of the South Shetland Islands and Antarctic Peninsula region

During the BENTART 95 survey, epifauna was sampled with an Agassiz trawl at 24 stations ranging from north of Livingston Island (South Shetland Islands) to the Antarctic Peninsula at depths from 40 to 850 m. Four assemblages of ophiuroids were identified and correspond to Deception Island, Trinity Island, and the southern and northern zones of Livingston Island. In addition to these regions, gradients related to depth and filter-feeder biomass were found. The brittle-star assemblages were dominated by Ophionotus victoriae Bell, 1902, which to a large extent determine the biogeographic structure in the South Shetland Islands.

Fish length-weight relationships in the Weddell Sea and Bransfield Strait

Length-weight relationships are provided for 49 Antarctic fishes from 9 families. The fish were from three research cruises of 1996, 1998 and 2000 to the Weddell Sea and Antarctic Peninsula. Samples were collected by benthopelagic net, Agassiz trawl and bottom trawl at depths of 200–2,300 m. The exponent b in the length-weight relationship W=aL b ranged from 2.53 to 4.05. With a mean of 3.33, 50% of the values ranged between 3.157 and 3.480. In 31 species, the parameters were determined for each sex. For 64.5% of species, b was higher in females than in males. Exceptions were the Channichthyidae where b for six species was higher for males.

Reproductive ecology of the deep-sea scleractinian coral Fungiacyathus marenzelleri (Vaughan, 1906) in the northeast Atlantic Ocean

The reproductive biology and its seasonality were examined in the deep-water, solitary coral Fungiacyathus marenzelleri from 2,200 m depth in the NE Atlantic, using histological techniques. A total of 186 corals were collected using either an Otter trawl (semi-balloon) or Agassiz trawl from the research vessel RRS Challenger between 1979 and 1991. All individuals were gonochoric, with all 48 mesenteries being fertile. A high fecundity was recorded (2,892 ±44.4 oocytes per polyp) with strong size-dependency. This species is a quasi-continuous reproducer with overlapping gametogenesis for both spermacysts and oocytes. No planulae were observed and broadcasting of gametes is inferred, with the large egg size (max. 750-µm diameter) suggesting lecithotrophic development. There is a non-significant trend towards a synchronous spawning event during June/July. Asexual fission was observed, though in low numbers.

Distribution of macrobenthos in spring and autumn in the East China Sea

This paper presents the results of ecological study of the macrobenthic fauna in the East China Sea in autumn and spring. The materials were collected from 30 stations located between 121°～127°E and 26°～32°N in November 2000 and April 2001. For quantitative analysis, samples were collected by 0.1 m 2 box corer. Two successful grabs were regarded as one sample at a station. Samples were prepared by removing the mud and sand by whirlpool mud remover, filtering the specimens through a 0.1 mm sieve, and fixing them in 75% alcohol for small samples or 10% formalin for large. For qualitative analysis, samples were collected with a 1.5 m width×0.5 m height Agassiz trawl, effectively trawling for 15 minute at 2 knots speed, fixing the specimens as per the quantitative analysis. Biomass was measured by weighing the wet specimens with a 1/1000 gram precision electric balance. Altogether in the samples, 392 species of macrobenthos were identified, which belong respectively to Polychaeta, 95 species, Mollusca, 131 species, Crustacea, 118 species and Echinodermata, 48 species. Based upon the analysis of the data obtained during the survey, biomass of the macrobenthos averaged 7.21 g/m 2 in spring and 8.79 in fall, and density averaged 132.95 individuals/m 2 in spring and 101.45 in fall. There were no clear differences in density or distribution of the macrobenthos between spring and fall. In autumn, some species migrate from shore and Changjiang Estuary to the Kuroshio Current. Compared with the benthos research results of "The comprehensive resource investigation of Chinese coast and shallow waters" (1958～1960) and the Survey of "Jinxing" Vessel (1975～1976) in the same region, the distribution pattern and the ecological characteristics of the macrobenthos have not changed dramatically, although the biomass in spring of 2001 was lower than that of 1959.

Species diversity and assemblages of macrobenthic Mollusca from the South Shetland Islands and Bransfield Strait (Antarctica)

During the research program BENTART 95, carried out from 16 January to 4 February 1995 on board RV Hesperides, a semi-quantitative Agassiz trawl and quantitative Van-Veen grabs were used at 31 subtidal stations between 40 and 850 m depth around Livingston Island, at Deception Island and in the Bransfield Strait. These data were used to search for and analyse the malacological assemblages. Among the molluscs sampled were 1,786 individuals belonging to 70 species of Solenogastres, Gastropoda Prosobranchia and Opisthobranchia, Scaphopoda and Bivalvia. The values of Shannon-Wiener diversity index ranged between 0.00 (one specimen) and 3.95, while Pielou's evenness index varied between 0.0 and 1.00. The bivalve Thyasira cf. dearborni was the most abundant species (227 specimens). Species richness varied from 1 to 19 species. Diversity showed great variations at different stations. The clustering analysis applying the Bray-Curtis coefficient allowed species classification according to constancy and fidelity, and distinguished four groups of stations: one that gathers clearly the stations of the inner bay of Deception Island, excepting station 1, and the other three fitting the remaining stations, located north and south of Livingston Island and in the Bransfield Strait, and correlated with environmental factors (granulometric composition, organic matter and carbonates).

Faunal diversity of the benthic amphipods (Crustacea) of the Magellan region as compared to the Antarctic (preliminary results)

To investigate the marine benthic ecosystems of the Magellan region and to compare them with the better known Antarctic systems, three campaigns were recently carried out in this area: the Joint Magellan Victor Hensen Campaign 1994, the Polarstern ANT XIII/4 cruise 1996, and the Vidal Gormaz CIMAR FIORDO II cruise 1996. Numerous and diverse zoobenthos samples were collected mostly with an Agassiz trawl and with a small dredge, an epibenthic sledge, with baited traps or by diving. All gears together gathered more than 132,000 specimens of gammaridean and caprellidean amphipods. 137 species of gammaridean amphipods have been identified from the material to date. About 20% of these species appear to be new for science. This taxonomic work takes place in the framework of a general revision of the Southern Ocean amphipod fauna undertaken by theAntarctic Amphipodologists Network. A complete list of the benthic species of gammaridean and caprellidean amphipods is presented, including the zoogeographical distribution and the new records. The new abundant material collected, still under study, will allow a comparison of faunal diversity, zoogeographical and ecological traits of the Magellan benthic amphipod taxocoenoses with those of the West and East Antarctic benthos.

Size structure and sex composition of <i>Eurypodius latreillii</i> Guérin, 1828 (Brachyura) and <i>Pagurus comptus</i> White, 1847 (Anomura) in southern Chile

SUMMARY: The decapod crustaceans Eurypodius latreillii (Brachyura) and Pagurus comptus (Paguridae) were the most frequently occurring species in Agassiz trawl (AGT) samples obtained during the Chilean - German - Italian “Victor Hensen” Expedition in the Straits of Magellan and south of the Beagle Channel. Sex composition and length structure aspects were studied using the material from 15 stations in the two areas, which comprised 773 specimens of E. latreillii and 647 P. comptus. The size frequency of both species was characterized by the presence of small individuals in shallow waters. The sex composition varied with depth, indicating a dominance of E. latreillii females in deep waters, whereas no such pattern was observed in P. comptus. These differences may be caused by epizoites of E. latreillii and the availability of vacant gastropod shells for P. comptus, in addition to geographical aspects and life-cycle patterns of these species.

Egg production of <i>Austropandalus grayi</i> (Decapoda, Caridea, Pandalidae) from the Magellan Region, South America

Austropandalus grayi is one of three pandalid shrimp species reported from Chilean waters. Here we describe fecundity, reproductive output, and chemical composition of the incubated embryos of A. grayi, providing the first account of such information for a pandalid species inhabiting the southern hemisphere. Ovigerous females (n = 96) were collected during October - November 1994 with an Agassiz trawl in waters off Patagonia and Tierra del Fuego, South America. Both egg production (between 50 and 1858 embryos) and early egg volume (x- = 0.069 mm3) of A. grayi were low when compared to values reported from other pandalids. Clutch size increased with maternal size, however, the size of recently-spawned eggs was not linked to female size. Although the egg mass volume remained almost stable during the incubation period, females lost on average 51.1% of their initially-laid embryos; however, this loss was more than compensated by an 88.4% increase of the egg volume during embryogenesis. Mean reproductive output was relatively low (0.133) and not related to maternal size. The RO-data of A. grayi and other pandalids seem to indicate an increasing energy allocation for reproduction towards higher latitudes, a trend which would be contrary to the results of studies with other crustaceans. Water was the predominant constituent of the chemical composition of developing embryos and increased from 62.2% to 70.2% during the incubation period. At the same time, organic matter declined and mineral content augmented. Generally, our results are in agreement with previous findings with regard to the chemical composition of developing decapod embryos.

The benthic decapod fauna in the channels and fjords along the South Patagonian Icefield, Southern Chile

The species composition and distribution of decapod crustaceans opposite the South Patagonian Icefield (SPI) was analyzed by means of 33 Agassiz trawl hauls, taken during August 1995 and October-November 1996 from board RV Vidal Gormaz. A total of 13 benthic decapod species were found, and the material yielded a total of 248 individuals. In addition, the pelagic shrimp Pasiphaea acutifrons appeared in just one haul. The number of species declined from the Pacific towards the inner fjords. Brachyura was the most frequent group within all areas, whereas caridean shrimps were frequent only in the channels and anomuran crabs in the fjords. Altogether the decapod species covered the whole depth range of sampling between 45 and 1218 m. Species number of decapods in the waters along the SPI was low, compared to a total number of 46 species, which are known from the total area between Chiloe island and the Straits of Magellan. The low species number may be related to the impact of the glaciers in southern Patagonia.

Preliminary report on Echinoidea and Asteroidea (Echinodermata) of the Joint Chilean-German-Italian Magellan Victor Hensen Campaign, 17 October - 25 November 1994

Part of the echinoderm material (Echinoidea and Asteroidea) sampled by 59 Agassiz trawls during the Victor Hensen Campaign 1994 is summarized in a preliminary species list. In total, 7 echinoids and 21 asteroids have been determined to species from the area between Paso Ancho and Cape Horn. All of them were known from the area before.

Genetic and morphometric comparisons of squat lobster, Munidopsis scobina (Decapoda: Anomura: Galatheidae) populations, with notes on the phylogeny of the genus Munidopsis

Specimens of the galatheid Munidopsis scobina were collected from two stations on the continental slope off Oman, at depths of 900 and 1000 m, using an Agassiz trawl. Starch gel electrophoresis, across 10 enzyme loci, was carried out on 427 specimens. Genetic variability was calculated for both populations using a number of parameters. F-statistics were used to estimate genetic variance within ( F IS) and between ( F ST) populations. Significant deviations from Hardy-Weinberg expectations were detected at one locus ( Gotb). Analyses of F IS revealed significant differences from zero at Gotb and Pgm, as a result of heterozygote deficiency. No relationship was observed between size of individuals and genotype. The number of genetically effective migrants per deme per generation ( N e m) was calculated using both F ST and private alleles methods. N e m values were theoretically sufficient to offset the effects of genetic drift. Additional morphometric analyses were carried out on Munidopsis scobina from the two populations. Individuals were sexed ( n=2476 individuals) and ten parameters measured ( n=1238). All specimens were examined for parasites (either bopyrid isopod or rhizocephalan). Significant male-biased sex ratios were observed in both populations ( p<0.01). In addition, significant differences in size-frequency distributions ( p<0.01) were recorded both within sites between sexes, and within sexes between sites; possibly related to a size-dependent response to hypoxia. Significant differences also were observed in mean cheliped length between sexes ( p<0.01), potentially indicating that male M. scobina exhibit agonistic behaviour. The genetic relationships of Munidopsis scobina to four other species of Munidopsis ( M. crassa, M. parfaiti, M. spinihirsuta and M. subsquamosa) and the confamilial Galathea squamifera were also examined using allozyme loci. Within the genus Munidopsis, pairwise comparisons of genetic identity were within the normal range expected for congeneric species. Comparisons between G. squamifera and Munidopsis spp. were within the range expected for confamilial genera.

Dolichiscus spinosetosus n. sp., a new arcturid isopod from the Weddell Sea, Antarctica

Two specimens of Dolichiscus spinosetosus were collected by means of an Agassiz trawl and a small dredge in the Weddell Sea, Antarctica. This species is characterized by a large number of strong spines on the dorsal side, some of these possessing tubercular tips. The dorsum is characterized by many smaller and shorter blunt spines and numerous long simple setae all over the body (on spines, pereonites and pleotelson). Dolichiscus acanthaspidus Schultz, 1981 is the taxon most closely related to this new species, but the new species has more setae and tubercular spines on all parts of the body and two caudolateral spines instead of one behind the supraocular ones.

Body size, sex ratio and diet composition of Arctogadus glacialis (Peters, 1874) (Pisces: Gadidae) in the Northeast Water Polynya (Greenland)

Little is known about the biology and feeding ecology of Arctogadus glacialis (Peters, 1874), an endemic gadid fish species occurring circumpolarly in both ice-free and ice-covered Arctic seas. In this study we analysed specimens sampled from bottom trawl and Agassiz trawl catches conducted at eight stations in water depths from 115 to 490 m in the Northeast Water Polynya off Greenland in August 1990. Size composition and sex ratios were assessed for 585 fish with standard lengths ranging from 7.8 to 34.5 cm. Median fish sizes at the stations ranged between 8.6 and 18.8 cm. Quantitative stomach content analyses of a subsample of 175 specimens revealed that in the Northeast Water A. glacialis fed almost exclusively on pelagic prey. Truly benthic organisms were not found in the stomachs, and sympagic species were rarely recorded. Overall, calanoid copepods were the major prey in terms of numbers. However, stomach contents varied considerably between fish size groups. In terms of prey biomass, copepods dominated the diet of small fish ( 16 cm), which dominated the catches at deep stations (360–480 m). The broad variety of diet composition indicated an opportunistic pelagic feeding pattern.