The role of prolactin during incubation: Comparative studies of three Diomedea albatrosses

first_imgThere is much recent evidence that prolactin is an important influence on parental and incubatory behaviour in birds. In this study prolactin was measured at various stages of the breeding cycle in three closely related albatrosses (the wandering albatross Diomedea exulans, the grey-headed albatross D. chrysostoma, and the black-browed albatross D. melanophris). Each species is monogamous, laying one egg, with the sexes sharing parental duties, including lengthy incubation shifts. In experiments where blood samples were taken daily throughout single incubation shifts (of both sexes) and every 3 hr for 36 hr, high prolactin levels were observed, but there was no indication of any changes that might suggest direct relationships between the hormone concentrations and incubatory behaviour. However, high prolactin levels were characteristic of the whole incubation period with a significant decline in concentrations towards the end of the brood-guard period. The timing of the decline in prolactin levels remained constant, even when the incubation period was artificially lengthened or shortened, as did the overall duration of the incubation-brood-guard period. Further experiments eliminated the possibility that the secretion of prolactin was a response to tactile stimulation of the brood patch by the egg. These results suggest that the incubation period is not endogenously timed but that prolactin may still affect the overall duration of the incubation-brood-guard period, although having little or no effect on the number or duration of incubation shifts.last_img read more

Some aspects of the small scale distribution of Euphausia crystallorophias

first_imgDiurnal variations in the vertical distribution and swarming behaviour of Euphausia crystallorophias at Deception Island (61 degrees South, 66 degrees West) are described. Swarms were present at all times of the day and night. By day swarms were compact and deep, they were dispersed and neared to the surface by night. Significant net avoidance was noted by day. A twenty-fold discrepancy was found between abundance estimated from net hauls and acoustics. This difference is almost certainly because currently used Target Strength (TS) to size relationships overestimate TS and consequently undersetimate euphausiid biomass.last_img read more

The terrestrial arthropod fauna of the Byers Peninsula, Livingston Island, South Shetland Islands

first_imgWe report the first detailed study of the terrestrial invertebrate fauna of the Byers Peninsula SSSI, Livingston Island, South Shetland Islands. Fourteen micro-arthropod taxa (10 Acari, four Collembola) and two Diptera are recorded, including the first record of the mite Edwardzetes dentifer from the maritime Antarctic. The first record of the midge Belgica antarctica from neighbouring Snow Island is also given. Population composition and density were described in samples from a wide range of terrestrial and freshwater habitats. There was no strong relationship between habitat and microarthropod species occurrence, although comparison of completely vegetated and more stony sites revealed greater population densities at the vegetated sites, and different species proportions at each. Some individual samples contained a wide range of species with none achieving numerical dominance, whilst others from superficially similar sites were dominated by one species. Dipterans were limited to a small number of lakes, streams and seepage areas, where they were sometimes abundant. Population density data and species occurrence are compared with previously published studies from the maritime Antarctic and elsewhere.last_img read more

Oribatid mites (Acari: Oribatida) of South Georgia, South Atlantic

first_imgTwenty-one species of oribatid mites (Acari: Oribatida), including three new species, are reported from samples collected on the sub-Antarctic island of South Georgia. Fossonothrus wallworki n.sp., Lanceoppia elegantula n.sp. and Edwardzetes australis n.sp. are described and figured. Ten additional species, recorded previously, provides a total of 31 species for the island.last_img

Salmonella in sub-Antarctica: low heterogeneity in salmonella serotypes in South Georgian seals and birds

first_imgThe number of human visitors to Antarctica is increasing rapidly, and with it a risk of introducing infectious organisms to native animals. To study the occurrence of salmonella serotypes in sub-Antarctic wildlife, faecal samples were collected from gentoo penguins, macaroni penguins, gray-headed albatrosses, black-browed albatrosses and Antarctic fur seals on Bird Island in the South Georgian archipelago during the austral summer of 1996 and 1998. In 1996, S. havana, S. typhimurium and S. enteritidis were isolated from 7% of gentoo penguins and 4% of fur seals. In 1998, however, 22% of fur seals were found to be infected with S. havana, S. enteritidis and S. newport. All isolates, except one, showed identical pulsed-field gel electrophoresis-patterns within each serotype, irrespective of sampling year and animal reservoir. No significant antibiotic resistance was found. The very low heterogeneity in the salmonella isolates found could either indicate a high genetic adaptation of the bacteria to the environment or a recent introduction of salmonella into the area.last_img read more

The impact of molecular data in fungal systematics

first_imgMolecular data has been used in fungal systematics since the 1970s, and its rate of incorporation has increased significantly in recent years. In phylogeny molecular data has already been used to clarify major evolutionary lines, and has aided in the delineation of higher taxonomic groups including the kingdom Fungi, and the main phyla within it. Molecular data has been used at all taxonomic levels and has allowed for a greater phylogenetic signal to be represented within systematic groups. At the higher levels this has led to the re-evaluation of some orders and families, and at lower taxonomic levels it has helped in the identification of species, particular populations and possibly individuals. There are however some limitations to the widespread use of molecular data. Some of these relate to the comparability and utility of methods between different fungal groups, some relate to the wide diversity of life cycles adopted by fungi, and others are due to the paucity of comparable definitive evolutionary markers. A significant limitation to the wider application of molecular data is the restricted range of data currently available, and the relation of this to the as yet unquantified numbers of undescribed species. Despite these limitations molecular data has had a very significant effect on our understanding of fungal systematics, and many further systematic aspects are likely to be elucidated in the future.last_img read more

Ciliate biogeography in Antarctic and Arctic freshwater ecosystems: endemism or global distribution of species?

first_imgCiliate diversity was investigated in situ in freshwater ecosystems of the maritime (South Shetland Islands, mainly Livingston Island, 63°S) and continental Antarctic (Victoria Land, 75°S), and the High Arctic (Svalbard, 79°N). In total, 334 species from 117 genera were identified in both polar regions, i.e. 210 spp. (98 genera) in the Arctic, 120 spp. (73 genera) in the maritime and 59 spp. (41 genera) in the continental Antarctic. Forty-four species (13% of all species) were common to both Arctic and Antarctic freshwater bodies and 19 spp. to both Antarctic areas (12% of all species). Many taxa are cosmopolitans but some, e.g. Stentor and Metopus spp., are not, and over 20% of the taxa found in any one of the three areas are new to science. Cluster analysis revealed that species similarity between different biotopes (soil, moss) within a study area was higher than between similar biotopes in different regions. Distinct differences in the species composition of freshwater and terrestrial communities indicate that most limnetic ciliates are not ubiquitously distributed. These observations and the low congruence in species composition between both polar areas, within Antarctica and between high- and temperate-latitude water bodies, respectively, suggest that long-distance dispersal of limnetic ciliates is restricted and that some species have a limited geographical distribution.last_img read more

Ice disturbance intensity structures benthic communities in nearshore Antarctic waters

first_imgIce scouring is one of the 5 most significant natural forces acting on ecosystems, yet very few data exist linking the intensity of ice disturbance with parameters of benthic community structure. The benthos at 2 nearshore sites on Adelaide Island, Antarctica, was sampled at 3 resolutions to make novel links between biological data and empirical disturbance data from the literature. A total of 125 taxa and > 70 000 individuals were recorded. A total of 8 parameters of community structure were measured; all of them were negatively correlated to disturbance intensity at one site, whilst 6 significant relationships were found at the other site. At 2 of the 3 sampling resolutions, disturbance, rather than depth or the percentage cover of major substratum types, was the environmental variable most correlated with the patterns in community structure. Furthermore, biological samples were divided into 3 categories based on the disturbance data (low, moderate and high). Each group was statistically dissimilar and the relative abundance of sessile fauna decreased as disturbance intensity increased. The intensity of disturbance was broadly correlated with depth, but small-scale differences in topography and substratum type created small-scale refugia, which supported richer assemblages. Overall, both study sites were disturbed frequently and no evidence of a peak in richness at the moderately disturbed locations was recorded.last_img read more

An overview of Southern Ocean zooplankton data: abundance, biomass, feeding and functional relationships

first_imgThere is an enormous amount of data on Southern Ocean (SO) zooplankton, mostly on their distribution with a minority addressing rate processes. This review aims to summarise these data and show where it resides, to assist SO food-web modellers or those with limited specialist knowledge of SO zooplankton. First, a brief overview is provided of the diversity and basic biology of SO zooplankton, with an emphasis on abundance, distribution and feeding. Second, advice is provided on the uses, strengths and limitations of zooplankton data as inputs to SO data compilations or food-web models. Copepods overall comprise >75% of the SO zooplankton biomass (excluding Euphausia superba). Total mesozooplankton biomass density differs little between the Antarctic sectors, but latitudinally it is maximal in the Polar Frontal Zone and declines to the north and south. Those compiling data on numerical density (no. m–2 or no. m–3) need to allow for differences in the extent of identification of early larval stages. Likewise, the time of year, depth of sampling and mesh size of sampler greatly influence the recorded abundance, since the populations can make seasonal vertical migrations and their pulsed reproduction causes great seasonal changes in size structure and abundance. Other issues are specific to polar environments, for example, lipid storage which leads to significantly different length-mass and mass-rate relationships than are reported in global literature compilations. Likewise, stenothermy (narrow temperature tolerance) means that fixed (Q10-type) temperature relationships based on global literature compilations must be applied with great caution in SO-specific studies. Protozoa/micrometazoa (<200 μm) are the main grazers in the SO, since mesozooplankton typically remove <30% of primary production. This emphasises the dominant role of microbial food chains involving small metazoans, relative to the classic short diatom-krill-whale type food chains. Even within regions of abundant krill, copepod production in summer roughly triples that of postlarval E. superba. This fact reflects a large flow of energy through multiple trophic levels, via copepods and their major invertebrate predators such as other predatory copepods, chaetognaths, small omnivorous euphausiids, amphipods up to myctophid fish and birds.last_img read more

Global diversity and oceanic divergence of humpback whales (Megaptera novaeangliae)

first_imgHumpback whales (Megaptera novaeangliae) annually undertake the longest migrations between seasonal feeding and breeding grounds of any mammal. Despite this dispersal potential, discontinuous seasonal distributions and migratory patterns suggest that humpbacks form discrete regional populations within each ocean. To better understand the worldwide population history of humpbacks, and the interplay of this species with the oceanic environment through geological time, we assembled mitochondrial DNA control region sequences representing approximately 2700 individuals (465 bp, 219 haplotypes) and eight nuclear intronic sequences representing approximately 70 individuals (3700 bp, 140 alleles) from the North Pacific, North Atlantic and Southern Hemisphere. Bayesian divergence time reconstructions date the origin of humpback mtDNA lineages to the Pleistocene (880 ka, 95% posterior intervals 550–1320 ka) and estimate radiation of current Northern Hemisphere lineages between 50 and 200 ka, indicating colonization of the northern oceans prior to the Last Glacial Maximum. Coalescent analyses reveal restricted gene flow between ocean basins, with long-term migration rates (individual migrants per generation) of less than 3.3 for mtDNA and less than 2 for nuclear genomic DNA. Genetic evidence suggests that humpbacks in the North Pacific, North Atlantic and Southern Hemisphere are on independent evolutionary trajectories, supporting taxonomic revision of M. novaeangliae to three subspecies.last_img read more