Adaptations for the maintenance of water balance by three species of Antarctic mites

Three species of Antarctic mites, Alaskozetes antarcticus, Hydrogamasellus antarcticus and Rhagidia gerlachei, are abundant in the vicinity of Palmer Station, Antarctica. No single mechanism for reducing water stress was shared by all three species. A. antarcticus and R. gerlachei (both ca. 200 μg) are over twice as large as H. antarcticus (ca. 90 μg), but all had similar body water content (67%) and tolerated a loss of up to 35% of their body water before succumbing to dehydration. All imbibed free water and had the capacity to reduce water loss behaviorally by forming clusters. Alaskozetes antarcticus was distinct in that it relied heavily on water conservation (xerophilic classification) that was largely achieved by its thick cuticular armor, a feature shared by all members of this suborder (Oribatida), and abundant cuticular hydrocarbons. In comparison to the other two species, A. antarcticus was coated with 2–3× the amount of cuticular hydrocarbons, had a 20-fold reduction in net transpiration rate, and had a critical transition temperature (CTT) that indicates a pronounced suppression in activation energy (E _a) at temperatures below 25°C. In contrast, H. antarcticus and R. gerlachei lack a CTT, have lower amounts of cuticular hydrocarbons and have low E _as and high net transpiration rates, classifying them as hydrophilic. Only H. antarcticus was capable of utilizing water vapor to replenish its water stores, but it could do so only at relative humidities close to saturation (95–98 %RH). Thus, H. antarcticus and R. gerlachei require wet habitats and low temperature to counter water loss, and replace lost water behaviorally through predation. Compared to mites from the temperate zone, all three Antarctic species had a lower water content, a feature that commonly enhances cold tolerance.     

Continuous benthic community change along a depth gradient in Antarctic shallows: evidence of patchiness but not zonation

Many shallow water polar communities demonstrate considerable change along a bathymetric gradient. However, it is currently unclear whether community change is generally continuous or discrete. To determine the nature of community change with depth, extensive photographic surveys at three sites at Adelaide Island, West Antarctic Peninsula, were conducted along a bathymetric gradient of 5–35 m depth. Macroalgae were largely absent at the sites, so only distinguishable macrofauna were counted and analysed. Faunal abundance was greatest at the shallowest stations of the depth transects, whilst richness at both species and phylum level increased with depth. Variability in community structure between replicate transects decreased with depth, so that assemblages at >25 m depth were more homogenous. Depth had a highly significant effect on total abundance, species richness and community structure, and it is likely that the frequency of ice disturbance, which also decreases with depth, drives this pattern. Overall, high variability between transects at each site was recorded, which suggested considerable patchiness at the scale of tens of meters. Community change along the bathymetric gradient was continuous and no evidence of discrete zones of assemblages was recorded.     

Cutaneous and diphtheritic avian poxvirus infection in a nestling Southern Giant Petrel (Macronectes giganteus) from Antarctica

The Southern giant petrel (Macronectes giganteus) is declining over much of its range and currently is listed as vulnerable to extinction by the International Union for the Conservation of Nature (IUCN). Island-specific breeding colonies near Palmer Station, Antarctica, have been monitored for over 30 years, and because this population continues to increase, it is critically important to conservation. In austral summer 2004, six diseased giant petrel chicks were observed in four of these colonies. Diseased chicks were 6–9 weeks old and had multiple proliferative nodules on their bills and skin. One severely affected chick was found dead on the nest and was salvaged for necropsy. Histopathological examination of nodules from the dead chick revealed epithelial cell hyperplasia and hypertrophy with numerous eosinophilic intracytoplasmic inclusions (Böllinger bodies). A poxvirus was isolated from multiple nodules. Poxviral infection has not been reported in this species, and the reason for its emergence and its potential impact on the population are not yet known.     

Response of Antarctic benthic communities to disturbance: first results from the artificial Benthic Disturbance Experiment on the eastern Weddell Sea Shelf, Antarctica

The long-term benthic disturbance experiment (BENDEX) was started on the eastern Weddell Sea shelf off Austasen (Antarctica) during ‘Polarstern’ cruise ANT XXI/2 in December 2003 to simulate the impact of grounding icebergs on the seabed and follow the steps and timescales of recovery of disturbed benthos and demersal fish communities. Here, we report the basic approach and first results for this experimental field study. By means of 11 densely-placed hauls with a modified bottom trawl, a seabed area of approximately 100 × 1000 m was artificially scoured to inflict a similar damage to the benthic habitats as a grounding iceberg. Before the disturbance event and 11 days after it, the seafloor communities were sampled (invertebrate assemblages by multibox corers, the fish fauna by trawl hauls) and comparatively analyzed. Sediment texture and chemistry was not significantly altered by the heavy disturbance inflicted by repeated trawling, whereas the fauna was negatively affected. Invertebrate benthic biomass was drastically reduced by a factor of 10, while mean abundances were only slightly reduced. Demersal fish biomass and abundance were slightly but not significantly smaller after the disturbance. Effects of disturbance became more evident in the composition of the fish fauna, with Trematomus pennelli and T. hansoni being dominant at disturbed sites, whereas Chionodraco myersi was the dominant species in trawl catches from undisturbed stations.     

Breeding strategies of Antarctic Petrels Thalassoica antarctica and Southern Fulmars Fulmarus glacialoides in the high Antarctic and implications for reproductive success

Breeding strategies of two closely related fulmarine petrels were studied on Ardery Island, on the continental coast of East Antarctica, where short summers are expected to narrow the time-window for reproduction. Both species had a similar breeding period (97 days from laying to fledging) but Antarctic Petrels Thalassoica antarctica bred up to 16 days earlier than Southern Fulmars. During the pre-laying exodus, all Antarctic Petrels deserted the colony, whereas some Southern Fulmars Fulmarus glacialoides remained. Antarctic Petrels exhibited stronger synchronization in breeding, made longer foraging trips and spent less time guarding their chicks than Southern Fulmars. Overall breeding success of both species was similar but failures of Antarctic Petrels were concentrated in the early egg-phase and after hatching, when parents ceased guarding. Southern Fulmars lost eggs and chicks later in the breeding cycle and so wasted more parental investment in failed breeding attempts. Different breeding strategies may be imposed by flight characteristics; Southern Fulmars are less capable of crossing large expanses of pack ice and need to delay breeding until the sea ice retreats and breaks up. However, due to the short summer they risk chick failure when weather conditions deteriorate late in the season.     

Towards a generalized biogeography of the Southern Ocean benthos

Aim To investigate whether the biogeographical regions proposed by J. W. Hedgpeth and widely adopted by other authors hold true, are an oversimplification or with further data might show a unified Antarctic province. Location Southern Hemisphere. Methods The distributions of 1318 species of bivalves, 4656 species of gastropods, 1465 species of cheilostome and 167 species of cyclostome bryozoans were analysed for 29 regions in the Southern Hemisphere, including South American, South African, Tasmanian, New Zealand, sub‐Antarctic and Antarctic regions. We present data on species richness, rates of endemism, patterns of radiation, faunal similarities and multivariate biogeographical analyses. Results The most striking pattern to emerge from our data set of species counts per region was a strong east–west hemispheric asymmetry, with high species numbers in New Zealand, Tasmania and South Africa and low numbers in South America. In contrast, no difference was found in richness between the east and west parts of the Southern Ocean. We compared findings in our model taxa with published data on ascidians, cephalopods and pycnogonids. Further evidence of strong faunal links between the Antarctic and South America is reported in this study, although we found little evidence for a biogeographical relationship between the Antarctic or South America and New Zealand/Tasmania. Strong evidence exists for a long‐term influence of the Antarctic Circumpolar Current upon the distribution of Southern Ocean benthos. This is demonstrated by the reduced prevalence of South American species in the Antarctic and sub‐Antarctic with increasing distance from South America in the direction of the current. Three of our four study taxa (bivalves, cheilostomes and cyclostomes) show the Southern Ocean as a ‘single functional unit’ with no evidence for a biogeographical split between east and west. Main conclusions Unlike the biogeographical schemes previously proposed, we show that biogeographical regions in the Southern Ocean differ depending upon the class of animals being considered. Despite this we suggest that some general rules are viable, including species endemism rates of around 50%, a single Antarctic province and a definite distinction between the sub‐Antarctic islands influenced by South America and those of New Zealand.     

Polyhydroxyalkanoates are essential for maintenance of redox state in the Antarctic bacterium Pseudomonas sp. 14-3 during low temperature adaptation

Polyhydroxyalkanoates (PHAs) are highly reduced bacterial storage compounds that increase fitness in changing environments. We have previously shown that phaRBAC genes from the Antarctic bacterium Pseudomonas sp. 14-3 are located in a genomic island containing other genes probably related with its adaptability to cold environments. In this paper, Pseudomonas sp. 14-3 and its PHA synthase-minus mutant (phaC) were used to asses the effect of PHA accumulation on the adaptability to cold conditions. The phaC mutant was unable to grow at 10°C and was more susceptible to freezing than its parent strain. PHA was necessary for the development of the oxidative stress response induced by cold treatment. Addition of reduced compounds cystine and gluthathione suppressed the cold sensitive phenotype of the phaC mutant. Cold shock produced very rapid degradation of PHA in the wild type strain. The NADH/NAD ratio and NADPH content, estimated by diamide sensitivity, decreased strongly in the mutant after cold shock while only minor changes were observed in the wild type. Accordingly, the level of lipid peroxidation in the mutant strain was 25-fold higher after temperature downshift. We propose that PHA metabolism modulates the availability of reducing equivalents, contributing to alleviate the oxidative stress produced by low temperature.     

A panel of microsatellite loci from two species of octopus, Pareledone turqueti (Joubin, 1905) and Pareledone charcoti (Joubin, 1905)

Eighteen dinucleotide microsatellite loci were isolated from two octopus species, Pareledone turqueti and Pareledone charcoti, which are endemic to the Southern Ocean. Genetic diversity was assessed in samples of P. charcoti and P. turqueti from Elephant Island and Shag Rocks respectively. All except one locus (which has proved to be polymorphic in other species) were variable in the focal species and amplified between six and 30 and between four and 28 alleles for P. charcoti and P. turqueti respectively; mean expected heterozygosities varied between 0.38 and 0.95 (P. charcoti) and between 0.34 and 0.97 (P. turqueti), with significant (P < 0.05) departures from Hardy–Weinberg equilibrium at seven loci; three of these loci provided significant (P < 0.05) evidence for null alleles. Two pairs of loci isolated from P. turqueti demonstrated significant (P < 0.05) linkage disequilibrium. We are presently using these genetic markers to quantify spatial genetic structure in the genus Pareledone.     

Serum levels of immunoglobulins (IgG, IgA, IgM) in Antarctic summer expeditioners and their relationship with seasickness

The Antarctic continent is full of environmental extremes like isolation, cold, UV exposure, and blizzards etc. The present study was conducted to analyze the effect of ship borne journey and the impact of Antarctic harsh environment on serum immunoglobulin (IgG, IgM, IgA) levels and their relationship with seasickness in Indian expeditioners. It was observed that one month onboard ship journey induced an increase in serum IgA levels and decrease in IgG levels while after being one month off board at the Indian research station Maitri, decreased levels of IgG and increased levels of IgA were found. IgM levels were not altered in comparison to the base line control. Moreover, serum IgG level showed a positive correlation while IgA level showed a negative correlation with seasickness. The stimulation of human peripheral blood mononuclear cells (PBMCs) with serum of expeditioner at different places showed that IgA at lower dose induces the release of pro-inflammatory IL-1β, and IL-6 cytokines from PBMCs while higher dose of IgA decreases proinflammatory cytokine production. The release of anti-inflammatory cytokines TGF-β1 and IL-10 was not significantly altered. Thus, the present study concluded that ship borne journey and Antarctic environment lead to increased serum IgA levels while decreased IgG levels. It also suggests that serum IgA level could be a possible biomarker for environmental stress.