Deep-sea Tardigrada from South Shetland Islands (Antarctica) with description of Angursa antarctica sp. nov. (Arthrotardigrada, Halechiniscidae)

A new species of marine tardigrade is described coming from the muddy sediment of the Antarctic deep sea. Angursa antarctica sp. nov. is characterized by the presence of balloon-shaped primary clavae, long lateral cirri, long cephalic cirri, spines on legs I, hemispherical capsule-shaped papillae on legs IV, and short external peduncles. Geographical distribution of the genus Angursa extends to Antarctic waters, suggesting a cosmopolitan distribution for this bathyal and abyssal genus. A table comparing the main differentiating characteristics of the species of Angursa is presented. Received: 25 July 1997 / Accepted: 9 November 1997     

Penguins, fur seals, and fishing: prey requirements and potential competition in the South Shetland Islands, Antarctica

Antarctic and sub-Antarctic seabirds, marine mammals, and human fisheries concentrate their foraging efforts on a single species, Antarctic krill (Euphausiasuperba). Because these predators may have a significant effect on krill abundance, we estimated the energy and prey requirements of Adelie (Pygoscelisadeliae), chinstrap (Pygoscelisantarctica), and gentoo (Pygoscelispapua) penguins and female Antarctic fur seals (Arctocephalusgazella) breeding on the South Shetland Islands, Antarctica and compared these estimates with catch statistics from the Antarctic krill fishery. Published data on field metabolic rate, population size, diet, prey energy content, and metabolic efficiency were used to estimate prey requirements of these breeding, adult, land-based predators and their dependent offspring. Due to their large population size, chinstrap penguins were the most significant krill predators during the period examined, consuming an estimated 7.8 × 10⁸ kg krill, followed by Adelie penguins (3.1 × 10⁷ kg), gentoo penguins (1.2 × 10⁷ kg), and Antarctic fur seals (3.6 × 10⁶ kg). Total consumption of all land-based predators on the South Shetland Islands was estimated at 8.3 × 10⁸ kg krill. The commercial krill fishery harvest in the South Shetland Island region (1.0 × 10⁸ kg) was approximately 12% of this. Commercial harvest coincides seasonally and spatially with peak penguin and fur seal prey demands, and may affect prey availability to penguins and fur seals. This differs from the conclusions of Ichii et al. who asserted that the potential for competition between South Shetland predators and the commercial krill fishery is low. Received: 26 August 1997 / Accepted: 16 December 1997     

On two new species of Oswaldella Stechow, 1919 (Cnidaria, Hydrozoa) from Bransfield Strait (Antarctica)

Two species of the genus Oswaldella Stechow, 1919 new to science (Oswaldella crassa sp. nov. and O.␣curiosa sp. nov.) were studied. Both species are described and figured; their systematic position amongst the remaining species of the genus is discussed. The material originates from the Bransfield Strait area (Antarctica) and was collected during the United States Antarctic Research Program with R.V. Eltanin. A comparative table listing the main features of the known species of Oswaldella is presented. Finally, a general survey of geographical and bathymetrical distribution of the known species of Oswaldella is given. Received: 8 October 1997 / Accepted: 2 February 1998     

The diet of the Antarctic fur seal Arctocephalus gazella at Harmony Point, Nelson Island, South Shetland Islands

The diet of non-breeding male Antarctic fur seals (Arctocephalus gazella) was investigated at Harmony Point, Nelson Island, South Shetland Islands, by the analysis of 18 and 33 scats collected during February 1996 and 1997 respectively. Overall, fish were the most frequent prey (74.5%) and predominated by mass (54.4%), whereas krill predominated by number (94.2%). This coincides well with the pattern observed in 1997, but in 1996 krill was the most important prey by number and mass (50.2%). The importance of the remaining taxa represented in the samples (octopods, hyperiids and bivalves) was negligible. Among fish, myctophids represented 85.2% of the fish mass, with Gymnoscopelus nicholsi and Electrona antarctica being the main prey. These two species predominated in 1997, whereas the channichthyid Cryodraco antarcticus and the nototheniid Gobionotothen gibberifrons were dominant in 1996. The importance of the myctophids as prey of the Antarctic fur seal is discussed. Received: 7 October 1997 / Accepted: 24 May 1998     

Congruence of electrical properties in two Antarctic and two middle-latitude marine species of Euplotes (Ciliata, Hypotrichida)

Electric membrane properties and motor behaviour of two Antarctic and two middle-latitude species of Euplotes were compared. Membrane potential fluctuations and whole-cell currents were measured using the whole cell clamp. The electrical properties of both of the Antarctic species between themselves and of both of the middle-latitude species are nearly identical. Furthermore, after warming up to 22°C, the Antarctic species grown at 4°C show the same pattern of spontaneous potential fluctuations, induced potential oscillations and membrane currents as the middle-latitude species grown and measured at 22°C. After cooling down to 4°C, the middle-latitude species grown at 22°C show the same electrical properties as the Antarctic species grown and measured at 4°C. The congruence of the temperature-dependent electrical properties in Euplotes species from completely different habitats is presumably based on a universal mechanism of temperature dependence of ionic conductances, indicating the close physiological relationship among the species. Received: 29 October 1997 / Accepted: 20 April 1998     

The contrasting diet of Harpagifer antarcticus (Notothenioidei, Harpagiferidae) at two localities of the South Shetland Islands, Antarctica

The diet of Harpagifer antarcticus was studied at two localities of the South Shetland Islands, Antarctica. The analysis of the stomach contents of specimens collected in tide pools at Potter Cove, King George Island, indicated that gammarid amphipods (mainly Gondogeneia sp.) were the main prey of this fish, followed by polychaetes, gastropods and isopods. By contrast, the specimens from Harmony Point, Nelson Island, which were recovered from stomach contents of Antarctic shags Phalacrocorax bransfieldensis feeding at depths of 46–110 m, preyed almost exclusively on the Antarctic krill Euphausia superba. These results are discussed and compared with previous studies. Received: 27 August 1997 / Accepted: 17 November 1997     

Occurrence of the flea Glaciopsyllus antarcticus and avian lice in central Dronning Maud Land

The flea Glaciopsyllus antarcticus is endemic to the Antarctic continent, where it is known to parasitise a number of seabird species. This paper reports the occurrence of the flea and two species of lice from snow petrel (Pagodroma nivea) colonies in central Dronning Maud Land, Antarctica, and extends considerably the recorded distribution of the flea. Flea adults, pupae and larvae were recovered from 10 of 11 samples of organic material collected from snow petrel nests at Svarthamaren (71°53^′S, 05°10^′E) in the Mühlig-Hofmannfjella. Specimens of two philopterid lice species, Saemundssonia antarctica and Pseudonirmus charcoti, were recovered from three of these samples. Specimens of the Antarctic flea and of the louse S. antarctica were recovered from carcasses of snow petrel chicks collected both at Svarthamaren and Robertskollen (71°28^′S, 03°15^′W) in the northern Ahlmannryggen; the louse Pseudonirmus charcoti was recovered from Robertskollen only. Received: 30 January 1996 / Accepted: 28 April 1997     

The role of the rock cod Notothenia coriiceps Richardson, 1844 in the life-cycle of Antarctic parasites

Fifty specimens of Notothenia coriiceps caught in Potter Cove, King George Island, were examined for ecto- and endoparasites. Of the 22 parasite species found, 18 were helminths, 2 were hirudineans and 2 were crustaceans. The isopod Aega antarctica and an unidentified hirudinean are reported for the first time from this fish host. Dominant parasites were the adults of Aspersentis megarhynchus, the invasive stage of Corynosoma spp. (cystacanth) and the adults of Macvicaria pennelli, with respective prevalences of infestation of 94, 76 and 74%. The preferred sites of infestation were the pylorus and intestine, where five different larval (nematodes and cestodes) and eight adult (digeneans and acanthocephalans) parasite species were found. No adult nematodes and cestodes were found and no parasites could be isolated from the musculature. The results of the present study are related to previous findings on the parasite fauna of N. coriiceps. The comparison implies a high parasite diversity in this benthic Antarctic fish species. Most parasites found appear to have a wide range of distribution within Antarctic waters together with a low host specificity. Besides its role as final host for several species of trematodes and acanthocephalans, N. coriiceps serves as transmitter of parasite larvae to piscivorous birds and seals. It is concluded that the parasite fauna in Antarctic fish species provides important insights into the different habitat use and trophic relationship of their fish hosts. Received: 11 September 1997 / Accepted: 12 January 1998     

Qualitative and quantitative analysis of serum immunoglobulins of four Antarctic fish species

Immunoglobulins from the Antarctic fish species Trematomus bernacchii, Trematomus hansoni, Trematomus newnesi, and Chionodraco hamatus were analysed in whole serum and after purification by affinity chromatography on protein A-sepharose. Using SDS-PAGE, the apparent masses of the heavy and light chains were, respectively, 83.5 kDa and 27.5 kDa for T. bernacchii, 83.5 kDa and 27 kDa for T. hansoni, 81 kDa and 27.5 kDa for T. newnesi, and 74.5 kDa and 30 kDa for C. hamatus. It was not possible to purify immunoglobulins from T. newnesi due to their low concentration in serum. Heterogeneity in mass of both heavy and light chains was observed in all species. By using a polyclonal antibody raised against sea bass immunoglobulins, cross-reactivity was observed with heavy and light chains of all species. With this antibody, an indirect enzyme-linked immunosorbent assay (ELISA) was developed and results showed the relative immunoglobulin concentration in sera of the Antarctic fish species considered, using as standard sea bass immunoglobulins. Received: 25 November 1996 / Accepted: 3 February 1997     

Diet and prey consumption of Antarctic petrels Thalassoica antarctica at Svarthamaren, Dronning Maud Land, and at sea outside the colony

The diet of the Antarctic petrel Thalassoica antarctica was studied during two seasons at Svarthamaren, an inland colony in Dronning Maud Land, Antarctica, and in the pack ice off the coast of Svarthamaren. The most important food (wet mass) at Svarthamaren was crustaceans (67%), fish (29%) and squid (5%); however, individuals collected in the pack ice took mostly fish (87%). The prey composition and lengths of prey are comparable to what has been documented in other studies on this species. Estimates of food consumption by birds breeding at Svarthamaren (ca. 250,000 pairs) suggest that approximately 6500 tonnes of crustaceans, 2800 tonnes of fish and 435 tonnes of squid are consumed during the breeding season. The annual consumptions of these birds are estimated to be 34,100 tonnes of crustaceans, 14,700 tonnes of fish, and 2300 tonnes of squid. Satellite telemetry data indicate that Antarctic petrels from Svarthamaren may fly more than 3000 km during one foraging trip, and thus may cover a huge ocean area to obtain their prey. Received: 1 September 1997 / Accepted: 3 February 1998     

Feeding plasticity of the Antarctic fish Trematomus hansoni Boulenger, 1902 (Pisces: Nototheniidae): the influence of fishery waste on the diet

The consumption of fishery waste by the Antarctic bottom-dwelling fish, Trematomus hansoni, is described in the Cosmonaut Sea. The study indicates that T. hansoni is able to switch its feeding habits at the time of fishery operations by incorporating fishery waste into the diet. Received: 22 September 1997 / Accepted: 21 November 1997     

Composition and community structure of pelagic copepods in the Indian sector of the Antarctic Ocean during the end of the austral summer

The present paper describes latitudinal and vertical changes in the composition, abundance and diversity of copepods in the Indian sector of the Antarctic Ocean, during the end of austral summer along a transect on 66°30′E between 43 and 62°S, within three layers (600–0, 200–0, 100–0 m). Highest copepod densities were noted in the central part of the transect, between the Antarctic Divergence and the Antarctic Convergence, with a maximum in the Antarctic Divergence zone, particularly in the upper levels of the water column. A total number of 80 copepod species were identified over the entire survey area. The south end and the central part of the transect comprised a small number of species. North of the Antarctic Convergence, this number increased markedly with the progressive disappearence of those species characteristic of Antarctic waters and their replacement by temperate and subtropical species. Generally, small copepods, particularly Oithona similis, Oithona frigida and Ctenocalanus citer, dominated in numbers in both Antarctic and sub-Antarctic areas. The contribution of large species to total copepod numbers was much lower, with Calanus simillimus in the central part of the transect, Pleuromamma borealis in the subtropical zone and Calanus propinquus in the southern part. Correspondence analysis showed a marked latitudinal gradient in population structure with four groups of samples and species corresponding to four latitudinal zones. Community structure (species richness, relative dominance index, evenness, Shannon species diversity index) and species abundance patterns (as rank-frequency diagrams) suggested that the maturity and species richness increased gradually from south to north. A low diversity index and evenness were observed in the area of the Antarctic Divergence, whereas the convergence zone showed high diversity and evenness. Conversely, the frontal zone showed high diversity and evenness. Distribution appeared unrelated to chlorophyll concentrations and on the large scale was related to the hydrologic characteristics. Received: 8 May 1996 / Accepted: 27 August 1996     

Egg hatching times of Antarctic copepods

Egg hatching times were determined at a range of temperatures for four species of commonly occurring Antarctic copepods. At a given temperature the eggs of Rhincalanus gigas took longest to hatch, up to 9 days at 0°C, followed by those of Calanoides acutus, Calanus propinquus and Calanus simillimus. A Bělehrádeks temperature function with the parameter b fixed at −2.05 accounted for >95% of the variance for each species. There was an approximate doubling in hatching times between 5°C and 0°C for R. gigas and for the other species the increase in embryonic duration was 40–50% at the lower temperature. Received: 27 March 1997 / Accepted: 17 August 1997     

Potential for biodegradation of hydrocarbons in soil from the Ross Dependency, Antarctica

Oil spills occur in the Antarctic when fuel oils such as JP8 jet fuel are moved or stored. Hydrocarbons, both n-alkanes and aromatic compounds, have been detected in oil-contaminated soils of the Ross Dependency. In such areas hydrocarbon-degrading microbes, if naturally occurring, could be used for clean-up. Soil samples from oil-impacted and control sites were analysed for hydrocarbon-degrading microbes and for a range of parameters known to limit biodegradative activity. Soils were analysed for water content, pH, concentrations of nutrients (N and P) and electrical conductivity. Numbers of culturable heterotrophic bacteria and hydrocarbon degraders were greater in some of the oil-contaminated samples. Mineralisation studies with ¹⁴C-radiolabelled hexadecane and naphthalene demonstrated that nitrogen amendments significantly enhanced hydrocarbon mineralisation rates in an oil-impacted soil. Received: 30 June 1997 / Received revision: 15 September 1997 / Accepted: 19 September 1997     

Activities of digestive enzymes of polar and subtropical echinoderms

Activities and characteristics of digestive enzymes of polar and subtropical echinoderms are similar. Specific adaptations to facilitate digestion at low temperature were not observed. Levels of chymotrypsin and β-glucosidase of digestive tissues of the Antarctic asteroids Odontaster validus and Odontaster meridionalis, and the Antarctic echinoid Sterechinus neumayeri, are comparable to levels of the asteroids Henricia downii and Astropecten articulatus from the Gulf of Mexico. α-Glucosidase activities are similar for S. neumayeri and A. articulatus. The pH of maximal activity is 7.5 for disaccharidases and 8.5–9.5 for chymotrypsin for both polar and subtropical species. Affinities for substrates were higher at 25°C than at 0°C for disaccharidases of all species. However, K_m values for chymotrypsin increased from 0 to 25°C. Lack of sufficient adaptation by polar echinoderms to facilitate digestion at low temperature may reduce their capacity to digest food. Received: 24 July 1996 / Accepted: 31 January 1997     

Steroid metabolism in Antarctic soft corals

Whole body tissue preparations of the Antarctic soft corals Alcyonium paessleri and Clavularia frankliniana were incubated in vitro with the radiolabelled precursors ³H-progesterone and ³H-androstenedione to determine steroidogenic capacity. Steroidal metabolites were identified using TLC, derivitization, and recrystallization techniques. The Antarctic soft corals converted labelled precursors (³H-progesterone and ³H-androstenedione) into a maximum of five metabolites, potentially indicating the activity of the following enzymes: 5α-reductase, 3β-hydroxysteroid dehydrogenase (HSD), 17β-HSD, and acyl transferase. Both species exhibited similar steroidogenic capacity. Radioimmunoassays verified the presence of relevant concentrations of progesterone, androstenedione, testosterone, and estradiol in whole body extracts from each species of soft coral. Alcyonium paessleri and Clavularia frankliniana actively converted precursors at temperatures up to 10°C above the ambient encountered by these species. Although similar steroidal compounds are produced in other phyla of benthic invertebrates, conversion rates for these soft corals are substantially lower. The role of these steroids is as yet unidentified; however they may be related to reproduction, and be important in chemical signaling or as defensive metabolites, or they may serve as transient intermediates to the production of other bioactive derivatives. Received: 2 September 1996 / Accepted: 10 January 1997     

Chaetoceros resting spores in the Gerlache Strait, Antarctic Peninsula

The formation of resting spores in diatoms is a common phenomenon in neritic environments. Here we report on resting spores of the genus Chaetoceros associated with a layer of increased chlorophyll fluorescence, at a depth of more than 200 m, north of Brabant Island and in Wilhelmina Bay, southeast coast of the Gerlache Strait (64°41.0′S, 62°0.5′W). Six species of Chaetoceros were identified by the morphology and size of the resting spores. Given that Chaetoceros spp., both in vegetative cells and as resting spores, are commonly found in Antarctic coastal surface waters, their location at depth could represent the pelagic “waiting” or “seeding” populations mentioned for other environments. Received: 25 November 1996 / Accepted: 16 November 1997     

Temporal patterns of primary production in a large ultra-oligotrophic Antarctic freshwater lake

A large ultra-oligotrophic Antarctic freshwater lake, Crooked Lake, was investigated between January 1993 and November 1993. The water column supported a small phytoplankton community limited by temperature, nutrient availability and, seasonally, by low photosynthetically active radiation. Chlorophyll a concentrations were consistently low (<1 g l⁻¹) and showed no obvious seasonal patterns. Production rates were low, ranging from non-detectable to 0.56 g C l⁻¹ h⁻¹, with highest rates generally occurring towards the end of the austral winter and in spring. The pattern of carbon fixation indicated that the phytoplankton was adapted to low light levels. Chlorophyll a specific photosynthetic rates (assimilation numbers) ranged from non-detectable to 1.27 gC (g chlorophyll a)⁻¹ h⁻¹. Partitioning of photosynthetic products revealed carbon incorporation principally into storage products such as lipids at high light fluxes with increasing protein synthesis at depth. With little allochthonous input the data suggest that lake dynamics in this Antarctic system are driven by phytoplankton activity. Received: 21 February 1997 / Accepted: 18 May 1997     

High abundance of Myriochele fragilis Nilsen & Holthe, 1985 (Polychaeta: Oweniidae) in the deep sea of the Eastern Mediterranean

An exceptionally high abundance of Myriochele fragilis Nilsen & Holthe, 1985 (Polychaeta: Oweniidae) is reported for the Ierapetra Basin in the Eastern Mediterranean Sea from depths of 4159 and 4260 m, representing the first record outside the Norwegian and Arctic Sea and extending the depth range by more than 1600 m. Specimens are described and compared to closely related species.     

Thermoregulation in Antarctic fulmarine petrels

We measured resting metabolic rates at air temperatures between ca. −5 and 30 °C in snow petrels (Pagodroma nivea), cape petrels (Daption capense), Antarctic petrels (Thalassoica antarctica), and Antarctic fulmars (Fulmarus glacialoides). We measured seven age classes for each species: adults, and nestlings that were 3, 8, 15, 28, 35, and 42 days old. Basal metabolic rate (BMR) and thermal conductance (C) of adults averaged, respectively, 140% and 100% of values predicted allometrically for nonpasserine birds. Minimum metabolic rates of unfasted nestlings aged 15–42 days averaged, respectively, 97% and 98% of predicted adult BMR in Antarctic petrels and snow petrels, versus 119% and 126% of predicted in Antarctic fulmars and cape petrels. Nestlings of the southerly breeding snow petrel and Antarctic petrel were relatively well insulated compared with nestlings of other high-latitude seabirds. Adult lower critical temperature (T_lc) was inversely related to body mass and averaged 9 °C lower than predicted allometrically. As nestlings grew, their T_lc decreased with increasing body mass from ca. 14 to 22 °C (depending upon species) at 3 days of age, to −4 to 8 °C when nestlings attained peak mass. Nestling T_lc subsequently increased as body mass decreased during pre-fledging weight recession. Nestling T_lc was close to mean air temperature from the end of brooding until fledging in the three surface nesting species. Accepted: 12 July 2000