Antarctic Silverfish Pleuragramma Antarcticum Research Articles

Life strategy of Antarctic silverfish promote large carbon export in Terra Nova Bay, Ross Sea

Antarctic silverfish Pleuragramma antarcticum is the most abundant pelagic fish in the High Antarctic shelf waters of the Southern Ocean, where it plays a pivotal role in the trophic web as the major link between lower and higher trophic levels. Despite the ecological importance of this species, knowledge about its role in the biogeochemical cycle is poor. We determine the seasonal contribution of Antarctic silverfish to carbon flux in terms of faeces and eggs, from samples collected in the Ross Sea. We find that eggs and faeces production generate a flux accounting for 41% of annual POC flux and that the variability of this flux is modulated by spawning strategy. This study shows the important role of this organism as a vector for carbon flux. Since Antarctic silverfish are strongly dependent on sea-ice, they might be especially sensitive to climatic changes. Our results suggest that a potential decrease in the biomass of this organism is likely to impact marine biogeochemical cycles, and this should be factored in when assessing Southern Ocean carbon budget.

Larval fish community in the Bay of Whales (eastern Ross sea): Species composition, relative abundance and spatial distribution

Early life stages of fish represent a key component in the food chain of the pelagic ecosystem of the Southern Ocean, connecting producer trophic levels to those of higher predators. Pelagic larvae and early juveniles of notothenioid fishes overwhelmingly dominate the ichthyoplankton community living on the continental shelf. Scientific research surveys targeting early life stages of fish in the pelagic realm have been mainly carried out in the western Ross Sea, whereas the eastern side can be considered unexplored. As source of high primary production, the presence and timing of formation of wide ice-free areas throughout the year in the Ross Sea play a fundamental role in structuring larval fish community. The Ross Ice Shelf Polynya (RISP) is a large coastal polynya, which is driven and maintained by local prevailing winds and oceanic currents. In the present study, we report the first data on species composition, relative abundance and spatial distribution of larval fish community found off the Bay of Whales in the eastern Ross Sea. As reported for other areas of the Ross Sea, the Antarctic silverfish Pleuragramma antarcticum was by far the most abundant species, followed by other nototheniids and channichthyids in smaller amounts. The huge abundance of P. antarcticum early larvae supports the hypothesis of a potential nursery area near the Bay of Whales. Present results strongly advocate for future investigations in these poorly known and remote areas.

Biological responses to change in Antarctic sea ice habitats

Sea ice is a key habitat in the high latitude Southern Ocean and is predicted to change in its extent, thickness and duration in coming decades. The sea-ice cover is instrumental in mediating ocean–atmosphere exchanges and provides an important substrate for organisms from microbes and algae to predators. Antarctic krill,Euphausia superba,is reliant on sea ice during key phases of its life cycle, particularly during the larval stages, for food and refuge from their predators, while other small grazers, including copepods and amphipods, either live in the brine channel system or find food and shelter at the ice-water interface and in gaps between rafted ice blocks. Fish, such as the Antarctic silverfishPleuragramma antarcticum, use platelet ice (loosely-formed frazil crystals) as an essential hatching and nursery ground. In this paper, we apply the framework of the Marine Ecosystem Assessment for the Southern Ocean (MEASO) to review current knowledge about relationships between sea ice and associated primary production and secondary consumers, their status and the drivers of sea-ice change in this ocean. We then use qualitative network modelling to explore possible responses of lower trophic level sea-ice biota to different perturbations, including warming air and ocean temperatures, increased storminess and reduced annual sea-ice duration. This modelling shows that pelagic algae, copepods, krill and fish are likely to decrease in response to warming temperatures and reduced sea-ice duration, while salp populations will likely increase under conditions of reduced sea-ice duration and increased number of days of >0°C. Differences in responses to these pressures between the five MEASO sectors were also explored. Greater impacts of environmental pressures on ice-related biota occurring presently were found for the West and East Pacific sectors (notably the Ross Sea and western Antarctic Peninsula), with likely flow-on effects to the wider ecosystem. All sectors are expected to be impacted over coming decades. Finally, we highlight priorities for future sea ice biological research to address knowledge gaps in this field.

Otolith chemical composition suggests local populations of Antarctic silverfish Pleuragramma antarctica (Boulenger, 1902) around Antarctica are exposed to similar environmental conditions at early life stages

Otolith chemical composition suggests local populations of Antarctic silverfish Pleuragramma antarctica (Boulenger, 1902) around Antarctica are exposed to similar environmental conditions at early life stages

Habitat-based density models of pack-ice seal distribution in the southern Weddell Sea, Antarctica

Climate variability and changes in sea ice dynamics have caused several ice-obligate or krill-dependent populations of marine predators to decline, eliciting concern about their demographic persistence and the indirect ecological consequences that predator depletions may have on marine ecosystems. Pack-ice seals are dominant ice-obligate predators in the Antarctic marine ecosystem, but there is considerable uncertainty about their abundance and population trends. We modelled the density and distribution of pack-ice seals as a function of environmental covariates in the southern Weddell Sea, Antarctica. Our density surface modelling approach used data from aerial surveys of pack-ice seals collected in the 2013/14 austral summer. Crabeater seals Lobodon carcinophaga, the most numerous pack-ice seal we observed, occurred at the highest densities in areas with extensive sea ice near the continental shelf break, but were almost absent in areas of similar sea ice concentration in the southern extent of the Weddell Sea. The highest densities of Weddell seals Leptonychotes weddelli, which were less abundant than crabeater seals within the pack-ice habitat, were predicted to occur over the continental shelf, near the shelf break. The distribution of both seal species broadly corresponded with the distribution and relative abundance of their main prey (Antarctic krill Euphausia superba and Antarctic silverfish Pleuragramma antarctica) obtained from concurrent ecosystem surveys. Ross seals Ommatophoca rossii and leopard seals Hydrurga leptonyx were not detected at all and are apparently rare within the southern Weddell Sea. These results can contribute to biodiversity assessments in the context of marine protected area planning in this region of the Southern Ocean.

Cytogenetic characterization of the Antarctic silverfish Pleuragramma antarctica (Boulenger 1902) through analysis of mitotic chromosomes from early larvae

This paper describes the cytogenetic features of the Antarctic silverfish Pleuragramma antarctica (Boulenger 1902), a keystone species of the Antarctic coastal marine ecosystem. Conventional cytogenetic analyses and physical mapping of repetitive DNA sequences were performed on metaphase plates obtained through direct chromosome preparation from P. antarctica early larvae.The Antarctic silverfish have a diploid number (2n) = 48, and a karyotype made up of a majority of two-armed chromosomes (karyotype formula36m/sm + 10st + 2a, fundamental number = 94). Major ribosomal gene repeats were detected on three chromosome pairs (20, 21, and 23), in correspondence of dim DAPI stained regions. Long Interspersed Nuclear Elements (LINEs) were abundant and wide spread over all chromosomes.Overall, the cytogenetic data presented herein are consistent with a long independent cytogenetic and evolutionary history for the species. The large number of two-armed chromosomes, indicative of highly-rearranged karyotype, coupled with a diploid number of 48, a presumed primitive character for this fish group, and the spread of the major ribosomal genes on three chromosome pairs, make the Antarctic silverfish distinct from all other notothenioid species.

Diversified feeding strategies of Pleuragramma antarctica (Nototheniidae) in the Southern Ocean

The Antarctic silverfish Pleuragramma antarctica is a plankton feeder playing an important role at midtrophic level in High Antarctic ecosystems. Over years, a reasonable bulk of information has been collected on the trophic ecology of the species, nevertheless there are several aspects that still deserve full elucidation. Here, we explore the trophic plasticity of the Antarctic silverfish, its ability to change and optimize the diet according to the prey availability. A comparative analysis of stomach contents, fish condition, and feeding selectivity was performed on specimens from three different locations in the Southern Ocean: Ross Sea, Adelie Land, and Antarctic Peninsula. While confirming copepods and euphausiids as the most important items in the diet of the Antarctic silverfish, present study revealed significant local differences in diet composition and fish condition. The specimens from the Antarctic Peninsula showed the highest body condition and euphausiids were the preferential prey. Conversely, specimens from the Ross Sea and Adelie Land, where euphausiids are not as abundant as in those of the Antarctic Peninsula waters, showed a flexible and opportunistic trophic habit strategy, profiting of being able to rely on the great variety of planktonic prey. Being P. antarctica a key component of the pelagic ecosystem, improved knowledge of the trophic ecology of this fish would contribute to a throughout understanding of its response to environmental change.

Post-fledging survival of Adélie penguins at multiple colonies: chicks raised on fish do well

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 601:239-251 (2018) - DOI: https://doi.org/10.3354/meps12687 Post-fledging survival of Adélie penguins at multiple colonies: chicks raised on fish do well David G. Ainley1,*, Katie M. Dugger2, Mario La Mesa3, Grant Ballard4, Kerry J. Barton5, Scott Jennings2,4,6, Brian J. Karl5, Amelie Lescroël4, Phil O’B. Lyver5, Annie Schmidt4, Peter Wilson5 1H. T. Harvey & Associates Ecological Consultants, Los Gatos, CA 95032, USA 2US Geological Survey, Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR 97331, USA 3ISMAR-CNR, Istituto di Scienze Marine, UOS di Ancona, 60125 Ancona, Italy 4Point Blue Conservation Science, Petaluma, CA 94954, USA 5Landcare Research, Lincoln 7640, New Zealand 6Present address: ACR, Cypress Grove Research Center, Marshall, CA 94940, USA *Corresponding author: dainley@penguinscience.com ABSTRACT: We assessed whether the mass of Adélie penguin Pygoscelis adeliae fledglings at 3 colonies of markedly disparate size on Ross Island, Ross Sea, correlated with their eventual return as subadults. We compared our results with those from Anvers Island, Bellingshausen Sea. Colony sizes at Ross Island have been increasing, contrary to decreasing size at Anvers Island. At Ross Island, during the month prior to fledging, chick diet consisted equally of energy-dense Antarctic silverfish Pleuragramma antarctica and less-caloric crystal krill Euphausia crystallorophias, while at Anvers Island the diet was principally Antarctic krill E. superba. At Ross Island, the mass of fledglings who subsequently returned (mean ± SE: 3.4 ± 0.0411 kg) exceeded that of those not seen again (3.2 ± 0.0251 kg), compared to Anvers Island (3.2 vs. 3.0 kg, respectively). At Ross Island, fledging mass was inversely related to colony size and, at the largest colony, fledging mass decreased as the colony grew. Average mass of returnees at the largest colony was less than the mass at Anvers Island for those fledglings that did not return. The mean proportion of fish in the chicks’ diet decreased at the largest Ross Island colony over time, as did fledging mass. We hypothesize that intraspecific competition increased along with colony size, decreasing the availability of fish. We further hypothesize that at the large Ross Island colony, post-fledging penguins must be finding adequate prey, and more energy-dense fish, just outside the colony’s foraging area to explain opposing trends in colony trajectories. KEY WORDS: Adélie penguin · Antarctic silverfish · Anvers Island · Central-place foraging · Ross Island · Intraspecific trophic competition Full text in pdf format PreviousNextCite this article as: Ainley DG, Dugger KM, La Mesa M, Ballard G and others (2018) Post-fledging survival of Adélie penguins at multiple colonies: chicks raised on fish do well. Mar Ecol Prog Ser 601:239-251. https://doi.org/10.3354/meps12687 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 601. Online publication date: August 09, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Diversification of feeding structures in three adult Antarctic nototheniid fish

During their evolution and speciation in the Antarctic waters, notothenioid fish occupied a variety of habitats and ecological niches. The diversification led to important variations in several morphological features related to particular aspects of their ecologies. We investigated the feeding structures and biomechanics of three phylogenetically related species (family Nototheniidae) with different ecologies: the bentho-pelagic Antarctic toothfish Dissostichus mawsoni, the pelagic Antarctic silverfish Pleuragramma antarctica, and the benthic emerald rockcod Trematomus bernacchii. The suction index (SI), the mechanical advantage in jaw closing (MA), and 14 morphological traits related to their feeding activity were analyzed. Significant differences among the species were found for all the parameters considered, supporting a high level of specialization.

Nrf2 and regulation of the antioxidant system in the Antarctic silverfish, Pleuragramma antarctica: Adaptation to environmental changes of pro-oxidant pressure

Despite the key importance of Nrf2-Keap1 in regulating antioxidant system in vertebrates, this system is still poorly investigated in marine species. The present study focused on the Antarctic silverfish Pleuragramma antarctica which, during the final phases of embryo development in platelet ice, is challenged by a sudden enhancement of environmental oxidative conditions associated to ice melting. Partial coding sequences were identified for Nrf2, its repressor Keap1 and for typical Nrf2-target antioxidant genes, like catalase, glutathione peroxidase isoform 1 and Cu/Zn-dependent superoxide dismutase. Compared to temperate homologues, the protein sequences showed an elevated conservation of amino acids essential for catalytic functions, while a few specific substitutions in non-essential regions may represent a molecular adaptation to improve flexibility and accessibility to active site at cold temperatures. The role of the Nrf2-Keap1 pathway in modulating the activation of antioxidant defences was demonstrated at both transcriptional and functional levels with a clear temporal increase of antioxidant protection in embryos before the hatching. Such findings confirm the importance of Nrf2 and highlight regulation of antioxidants as an adaptive strategy in P. antarctica to protect the early life stages toward the environmental changes of pro-oxidant pressure.

Reproductive features of the Antarctic silverfish (Pleuragramma antarctica) from the western Ross Sea

The Antarctic silverfish Pleuragramma antarctica is the most abundant pelagic fish inhabiting the Ross Sea. Given its ecological relevance in the local food web, it is considered a keystone species in the Antarctic coastal ecosystems. Many aspects of its biology have been elucidated, but knowledge of important parts of its life cycle, including reproduction, is still poor. Here we use macroscopic and histological approaches to describe the reproductive features of the Antarctic silverfish based on fish sampled in late summer in the Ross Sea. Both males and females were at an early developmental stage, consistent with what has been reported for the same species from other Antarctic sectors and with spawning occurring in late winter. Widespread follicular atresia has been detected in the fish examined. The analysis of its intensity and prevalence suggests that skipped spawning (not all adults spawn every year) is likely to be a reproductive strategy of the Antarctic silverfish.

Ontogenetic niche expansion influences mercury exposure in the Antarctic silverfish Pleuragramma antarcticum

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 504:253-263 (2014) - DOI: https://doi.org/10.3354/meps10738 Ontogenetic niche expansion influences mercury exposure in the Antarctic silverfish Pleuragramma antarcticum Rebecka L. Brasso1,*, Jennifer Lang1, Christopher D. Jones2, Michael J. Polito3 1University of North Carolina Wilmington, Department of Biology and Marine Biology, 601 South College Rd, Wilmington, North Carolina 28403, USA 2Antarctic Ecosystem Research Division, NOAA Southwest Fisheries Science Center, 8901 La Jolla Shores Drive, La Jolla, California 92037, USA 3Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, Massachusetts 02543, USA *Corresponding author: rlb1196@uncw.edu ABSTRACT: The effects of body size and age class on mercury concentrations were examined in the Antarctic silverfish Pleuragramma antarcticum, an ecologically important prey species in the Antarctic marine food web. Stable isotope analysis was used to investigate variation in mercury concentrations related to ontogenetic changes in diet and/or foraging habitat. Specimens of P. antarcticum were collected along the Ross Sea shelf in February 2008 and mercury concentrations in homogenized whole fish and muscle tissue were analyzed relative to standard length, age class (juvenile vs. adult) and isotopic measures of diet (δ15N) and foraging habitat (δ13C). While mercury concentration in muscle tended to be higher than whole-fish values, concentrations in these 2 matrices were highly correlated. A positive relationship was found between standard length and mercury concentration; further, adult P. antarcticum had significantly higher mercury concentrations than juveniles. Adult mercury concentrations were also more variable: the coefficient of variation in adult muscle (58.3%) was more than twice that found in juveniles (25.0%). Though no linear relationships were detected between standard length and δ15N or δ13C values when all individuals were combined, juvenile and adult size classes of fish differed in their isotopic niche position and width. In addition, δ13C values explained the greatest amount of variation in whole-fish mercury across all age classes and for adult fish alone. By expanding both the horizontal and vertical components of their foraging habitat, adult P. antarcticum may have a wider range of exposure to mercury compared with juvenile fish. KEY WORDS: Mercury · Ontogenetic shift · Trophic position · Stable isotope analysis · Foraging niche · Antarctic silverfish Full text in pdf format PreviousNextCite this article as: Brasso RL, Lang J, Jones CD, Polito MJ (2014) Ontogenetic niche expansion influences mercury exposure in the Antarctic silverfish Pleuragramma antarcticum. Mar Ecol Prog Ser 504:253-263. https://doi.org/10.3354/meps10738 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 504. Online publication date: May 14, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Diatom-Specific Highly Branched Isoprenoids as Biomarkers in Antarctic Consumers

The structure, functioning and dynamics of polar marine ecosystems are strongly influenced by the extent of sea ice. Ice algae and pelagic phytoplankton represent the primary sources of nutrition for higher trophic-level organisms in seasonally ice-covered areas, but their relative contributions to polar marine consumers remain largely unexplored. Here, we investigated the potential of diatom-specific lipid markers and highly branched isoprenoids (HBIs) for estimating the importance of these two carbon pools in an Antarctic pelagic ecosystem. Using GC-MS analysis, we studied HBI biomarkers in key marine species over three years in Adélie Land, Antarctica: euphausiids (ice krill Euphausia crystallorophias and Antarctic krill E. superba), fish (bald notothens Pagothenia borchgrevinki and Antarctic silverfish Pleuragramma antarcticum) and seabirds (Adélie penguins Pygoscelis adeliae, snow petrels Pagodroma nivea and cape petrels Daption capense). This study provides the first evidence of the incorporation of HBI lipids in Antarctic pelagic consumers. Specifically, a di-unsaturated HBI (diene) of sea ice origin was more abundant in ice-associated species than in pelagic species, whereas a tri-unsaturated HBI (triene) of phytoplanktonic origin was more abundant in pelagic species than in ice-associated species. Moreover, the relative abundances of diene and triene in seabird tissues and eggs were higher during a year of good sea ice conditions than in a year of poor ice conditions. In turn, the higher contribution of ice algal derived organic matter to the diet of seabirds was related to earlier breeding and higher breeding success. HBI biomarkers are a promising tool for estimating the contribution of organic matter derived from ice algae in pelagic consumers from Antarctica.

Diet and trophic niche of Antarctic silverfish Pleuragramma antarcticum in the Ross Sea, Antarctica

The diet of Antarctic silverfish Pleuragramma antarcticum was evaluated by examining stomach contents of specimens collected in the Ross Sea (71°-77° S; 165°-180° E) in January to March 2008. Pleuragramma antarcticum (50-236 mm standard length, L(S)) and prey items were analysed for stable-isotopic composition of carbon and nitrogen. According to index of relative importance (I(RI) ), which incorporates frequency of occurrence, mass and number of prey items, the most important prey items were copepods (81%I(RI) over all specimens), predominantly Metridia gerlachei and Paraeuchaeta sp., with krill and fishes having low I(RI) (2·2 and 5·6%I(RI) overall). According to mass of prey (M) in stomachs, however, fishes (P. antarcticum and myctophids) and krill dominated overall diet (48 and 22%M, respectively), with copepods being a relatively minor constituent of overall diet by mass (9·9%M). Piscivory by P. antarcticum occurred mainly in the extreme south-west of the region and near the continental slope. Krill identified to species level in P. antarcticum stomachs were predominantly Euphausia superba (14·1%M) with some Euphausia crystallophorias (4·8%M). Both DistLM modelling (PRIMER-permanova+) on stomach contents (by I(RI)) and stepwise generalized linear modelling on stable isotopes showed that L(S) and location were significant predictors of P. antarcticum diet. Postlarval P. antarcticum (50-89 mm L(S)) consumed exclusively copepods. Juvenile P. antarcticum (90-151 mm L(S)) consumed predominantly krill and copepods by mass (46 and 30%M, respectively). Small adult P. antarcticum (152-178 mm L(S)) consumed krill, fishes and copepods (37, 36 and 15%M, respectively). Large adult P. antarcticum (179-236 mm L(S)) consumed predominantly fishes and krill (55 and 17%M, respectively), especially in the north (near the Ross Sea slope) and in the SW Ross Sea. Amphipods were occasionally important prey items for P. antarcticum (western Ross Sea, 39%M). General concordance between stomach contents and trophic level of P. antarcticum and prey based on δ(15) N was demonstrated. Pleuragramma antarcticum trophic level was estimated as 3·7 (postlarval fish) and 4·1 (fish aged 3+ years).

A nursery area for the Antarctic silverfish Pleuragramma antarcticum at Terra Nova Bay (Ross Sea): first estimate of distribution and abundance of eggs and larvae under the seasonal sea-ice

Pleuragramma antarcticum is the dominant pelagic fish in the waters of the continental shelf in high Antarctic regions, where it plays a key role in the food web. A nursery ground for eggs of this species was first identified in 2002 in Terra Nova Bay (Ross Sea), where eggs were found trapped in ice platelets under the sea-ice during the spring. As part of a monitoring program aimed at understanding the geographic and temporal characteristics of this nursery ground, the present study reports on surveys carried out in the austral springs of 2005 and 2006 using a simple and effective method for sampling from the sea-ice. These surveys enabled the evaluation of the spatial range of the nursery area of the Antarctic silverfish in the sea-ice of the coastal area of Victoria Land between the Coulman Island and the Drygalski Glacier Tongue. P. antarcticum eggs were concentrated in an area of Terra Nova Bay of about 270 km2, encompassing two adjacent sites, Gerlache Inlet and Silverfish Bay. The present results add information on life cycle and hatching period of the Antarctic silverfish and confirm the importance of the Terra Nova Bay as a nursery area for this important species. Moreover, the survey points to the sea-ice cover and platelet ice as important environmental features of the nursery area.

Metabolic and behavioural adaptations during early development of the Antarctic silverfish, Pleuragramma antarcticum

The Antarctic silverfish Pleuragramma antarcticum is a keystone species in the Ross Sea ecosystem, providing one of the major links between lower and higher trophic levels. Despite the importance of this species, surprisingly little is known of its early development and behaviour. Here, we determine the metabolic capacity of Pleuragramma embryonated eggs and larvae and make comparisons with developing stages of another notothenioid, the naked dragonfish Gymnodraco acuticeps. We also show that although large numbers of embryonated eggs of Pleuragramma are found floating among the platelet ice of Terra Nova Bay, they are able to sink prior to hatching in late spring, likely reducing the risk of exposure to the potentially lethal, ice-laden surface environment. Applying Stoke’s law, we determine the change in density required for embryonated eggs to sink at the measured rate and then consider possible mechanisms by which this might occur. Significantly, newly hatched larvae are positively gravitactic and negatively phototactic, such that their swimming behaviour also directs them away from the risk of freezing in the icy surface waters. Measurement of the acute thermal tolerance shows that Pleuragramma larvae have, on average, a sustainable swimming performance breadth of about 17°C, which is significantly greater than that of other adult notothenioids. Although it lacks significant antifreeze capacity in its early developmental stages, Pleuragramma has other attributes that may ensure survival over a wider range of environmental temperatures than other more stenothermal Antarctic notothenioids. How it might adapt to prolonged environmental change arising from phenomena such as global warming, however, requires further investigation.

Presence and distribution of serotonin in the stomach of the Antarctic silverfish Pleuragramma antarcticum

Serotonin is a signal molecule with a wide range of functions in vertebrates. In Antarctic fishes, the serotonergic system has been studied in the brain, revealing differences from temperate fishes related to the long-term cold adaptation. To date, little is known regarding the peripheral nervous system, and no information is available for the stomach. In the present work, we contribute to fill the gaps by investigating the presence and the immunohistochemical distribution of serotonin in the stomach of the Antarctic silverfish Pleuragramma antarcticum, a cold-adapted key species of the Southern Ocean shelf food web. The main aim was to investigate the serotonergic system at the gastric level, in order to reveal possible peculiarities related to long-term cold adaptation, similar to the ones seen in the central nervous system of Antarctic fishes. Serotonin immunoreactivity was detected in the pyloric and cardiac mucosa of P. antarcticum stomach with immunopositive cells in the pyloric and cardiac surface epithelia and in the tubular glands. No immunopositive fibers and neuronal cell bodies were found. Our results highlight that the serotonin distribution pattern at the gastric level is similar to that described in temperate teleosts. This finding suggests that in P. antarcticum, long-term adaptations to the Antarctic condition do not affect the serotonergic system at the gastric level. In addition, our data constitute the baseline information for further investigations aimed at clarifying the effects of short-term temperature variations on the gastric serotonergic system of Antarctic species in the frame of the global climate change.

Food preferences of larvae of Antarctic silverfish Pleuragramma antarcticum Boulenger, 1902 from Terre Adélie coastal waters during summer 2004

Ichthyoplankton samples were collected from 19 to 31 January 2004 in the Dumont d’Urville Sea (East Antarctic shelf). The Nototheniidae Pleuragramma antarcticum comprised more than 90% of the sampled larvae. Gut contents of 95 P antarcticum larvae were examined. Most larvae fed on phytoplankton, especially diatoms, whereas some other specimens had a mixed diet with phyto- and zooplankton prey. A single specimen fed exclusively on copepods. The stomach contents was dominated by three diatoms taxa, such as Thalassiothrix antarctica, Fragilariopsis spp. and Chaetoceros spp. Prey selection was apparently food density dependent, with an inverse relationship between food abundance and selection feeding. Larvae selected positively some diatoms, such as Coscinodiscus spp. and T. antarctica, presenting a low concentration in the water column compared to Fragilariopsis spp., which were strongly negatively selected. During summer, larvae were opportunistic feeders with a broad trophic niche, which allowed them to switch between different food types.

Marine and terrestrial factors affecting Adélie­penguin Pygoscelis adeliae chick growth and recruitment off the western Antarctic Peninsula

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 436:273-289 (2011) - DOI: https://doi.org/10.3354/meps09242 Marine and terrestrial factors affecting Adélie ­penguin Pygoscelis adeliae chick growth and recruitment off the western Antarctic Peninsula Erik W. Chapman1,4,*, Eileen E. Hofmann1, Donna L. Patterson2, Christine A. Ribic3, William R. Fraser2 1Center for Coastal Physical Oceanography, Old Dominion University, 4111 Monarch Way, Norfolk, Virginia 23529, USA 2Polar Oceans Research Group, PO Box 368, Sheridan, Montana 59749, USA 3US Geological Survey Wisconsin Cooperative Wildlife Research Unit, Dept. Forest and Wildlife Ecology, University of Wisconsin, Madison, Wisconsin 53706, USA 4Present address: New Hampshire Sea Grant, University of New Hampshire Cooperative Extension, 131 Main Street, Durham, New Hampshire 03824, USA *Email: erik.chapman@unh.edu ABSTRACT: An individual-based bioenergetics model that simulates the growth of an Adélie penguin Pygoscelis adeliae chick from hatching to fledging was used to assess marine and terrestrial factors that affect chick growth and fledging mass off the western Antarctic Peninsula. Simulations considered the effects on Adélie penguin fledging mass of (1) modification of chick diet through the addition of Antarctic silverfish Pleuragramma antarcticum to an all-Antarctic krill Euphausia superba diet, (2) reduction of provisioning rate which may occur as a result of an environmental stress such as reduced prey availability, and (3) increased thermoregulatory costs due to wetting of chicks which may result from increased precipitation or snow-melt in colonies. Addition of 17% Antarctic silverfish of Age-Class 3 yr (AC3) to a penguin chick diet composed of Antarctic krill increased chick fledging mass by 5%. Environmental stress that results in >4% reduction in provisioning rate or wetting of just 10% of the chick’s surface area decreased fledging mass enough to reduce the chick’s probability of successful recruitment. The negative effects of reduced provisioning and wetting on chick growth can be compensated for by inclusion of Antarctic silverfish of AC3 and older in the chick diet. Results provide insight into climate-driven processes that influence chick growth and highlight a need for field research designed to investigate factors that determine the availability of AC3 and older Antarctic silverfish to foraging Adélie penguins and the influence of snowfall on chick wetting, thermoregulation and adult provisioning rate. KEY WORDS: Adélie penguin · Climate change · Chick growth · Antarctic Peninsula Full text in pdf format PreviousNextCite this article as: Chapman EW, Hofmann EE, Patterson DL, Ribic CA, Fraser WR (2011) Marine and terrestrial factors affecting Adélie ­penguin Pygoscelis adeliae chick growth and recruitment off the western Antarctic Peninsula. Mar Ecol Prog Ser 436:273-289. https://doi.org/10.3354/meps09242 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 436. Online publication date: August 31, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Characterization of novel microsatellite markers in the Antarctic silverfish Pleuragramma antarcticum and cross species amplification in other Notothenioidei

We characterized nine polymorphic microsatellites by an enriched library from the Antarctic silverfish Pleuragramma antarcticum, a key species in the high Antarctic zone of the Southern Ocean. The number of alleles scored ranged from 7 to 39, whereas the observed and expected heterozygosity ranged from 0.4000 to 0.9750 and from 0.3943 to 0.9782, respectively. Cross-amplification was tested in the 3 species of the genus Chionodraco (Channichthyidae). These new microsatellites could potentially be useful in further investigations on P. antarcticum for which many questions on population structure and exposition to global environment change are still open to debate.