A stable isotopic investigation into the causes of decline in a sub-Antarctic predator, the rockhopper penguin Eudyptes chrysocome

The rockhopper penguin (Eudyptes chrysocome) is a conspicuous apex marine predator that has experienced marked population declines throughout most of its circumpolar breeding distribution. The cause(s) for the declines remain elusive, but the relatively large spatio‐temporal scale over which population decreases have occurred implies that ecosystem‐scale, at‐sea factors are likely to be involved. We employ stable isotope analyses of carbon (¹³C/¹²C, expressed as δ¹³C) and nitrogen (¹⁵N/¹⁴N, δ¹⁵N) in time‐series of rockhopper penguin feather samples, dating back to 1861, in order to reconstruct the species' ecological history. Specifically, we examine whether rockhopper penguin population decline has been associated with a shift towards lower primary productivity in the ecosystem in which they feed, or with a shift to a diet of lower trophic status and lower quality, and we use long‐term temperature records to evaluate whether shifts in isotope ratios are associated with annual variations in sea surface temperature. Having controlled temporally for the Suess Effect and for increases in CO₂ concentrations in seawater, we found that overall, δ¹³C signatures decreased significantly over time in rockhopper penguins from seven breeding sites, supporting the hypothesis that decreases in primary productivity, and hence, carrying capacity, for which δ¹³C signature is a proxy, have been associated with the decline of penguin populations. There was some evidence of a long‐term decline in δ¹⁵N at some sites, and strong evidence that δ¹⁵N signatures were negatively related to sea surface temperatures across sites, indicative of a shift in diet to prey of lower trophic status over time and in warm years. However, a site‐by‐site analysis revealed divergent isotopic trends among sites: five of seven sites exhibited significant temporal or temperature‐related trends in isotope signatures. This study highlights the utility of stable isotope analyses when applied over relatively long timescales to apex predators.     

Polymorphic microsatellite loci isolated from the great scallop,Pecten maximus (Bivalvia: Pectinidae)

We isolated and characterized nine polymorphic microsatellite loci from the great scallop (Pecten maximus) as part of an attempt to better understand the population–genetic structure of this species. Levels of genetic diversity were assessed in 32 scallops collected from the coastal waters of Port Erin Bay, Isle of Man. The number of alleles ranged from two to 29 and observed and expected heterozygosities varied between 0.031 to 0.906 and 0.062 to 0.973, respectively. Two loci showed significant (P < 0.05) heterozygote deficits, likely because of null (nonamplifying) alleles; one pair of loci was in linkage disequilibrium.     

Distribution and feeding behaviour of field populations of the water cricket Velio, caprai (Hemiptera)

1. The distribution of individuals, prey capture success and prey choice were studied in a water cricket (Velia caprai) population in southern Ireland. Groups of different sizes were observed in the field during the summer and all potential prey animals entering the groups were counted. Surface drift samples were collected to assess the proportion of profitable prey items. 2. Two types of Velia groups were observed: mixed groups (adults and juvenile instars 4 and 5) and juvenile groups (instars 1–3), A greater proportion of the available prey was captured by the mixed groups. 3. Individuals in large groups had a lower capture rate than individuals in small groups. 4. No differences in capture rates could be found between males, females and juveniles, but differences in prey choice were apparent. Females captured more large prey than expected. 5. Water cricket distribution in the stream did not follow the ‘ideal free’ model; too few individuals were found at the most profitable sites. Food might not be the limiting factor during summer, and other factors such as intraspecific interference and predator avoidance could be more important.     

Satellite‐tracking of Northern Pintail Anas acuta during outbreaks of the H5N1 virus in Japan: implications for virus spread

We fitted Northern Pintail Anas acuta in Japan with satellite transmitters and monitored their spring migration movements relative to locations where the highly pathogenic H5N1 avian influenza virus was detected in Whooper Swans Cygnus cygnus in 2008. Pintails were assumed not to be infected with the H5N1 virus at the time they were marked because capture occurred between 2 and 5 months before reported outbreaks of the virus in Japan. We assessed spatial and temporal overlap between marked birds and occurrence of the virus and tracked Pintails after they departed outbreak locations. Eight of 66 (12.1%) Northern Pintails marked with satellite transmitters used wetlands in Japan where the H5N1 virus was detected in Whooper Swans. Apparent survival did not differ between Pintails that used H5N1 sites and those that did not. However, the proportion of Pintails that migrated from Japan was significantly lower among birds that used H5N1 sites compared with those that did not (0.50 vs. 0.79). Northern Pintails were present at the H5N1 sites from 1 to 88 days, with five birds present at the sites from 0 to 7 days prior to detection of the virus in Swans. The six Pintails observed to depart H5N1 sites did so within 2–77 days of the reported outbreaks and moved between 6 and 1200 km within 4 days of departure. Four Pintails migrated to eastern Russia. After their departure from outbreak sites, Northern Pintails made long‐distance migrations within the period when newly infected ducks would shed the H5N1 virus. This supports a hypothesized mechanism by which a highly pathogenic avian influenza virus could be spread by migratory birds.     

Sugar in the Intercellular Spaces of White Mustard Roots

A method is described by which it is possible to test directlyfor the presence of translocated radioactive sugar in the apicalmeristem of white mustard roots. Transverse sections of frozenroot tips, following treatment of living seedlings with radioactiveglucose are examined by radioautography. Radioactivity is concentratedin the conspicuous intercellular spaces and to a lesser degreein the intervening cell walls. These results are in harmonywith the theory of Priestley that the intercellular spaces andcell walls are the channels of transport of soluble nutrientsfrom the ends of differentiating vascular strands to the dividingcells in the root meristem.     

Biochemistry and Metabolism of Giardia

Giardia lamblia, an aerotolerant anaerobe, respires in the presence of oxygen by a flavin, iron-sulfur protein-mediated electron transport system. Glucose appears to be the only sugar catabolized by the Embden-Meyerhof-Pamas and hexose monophosphate pathways, and energy is produced by substrate level phosphorylation. Substrates are incompletely oxidized to CO₂, ethanol and acetate by nonsedimentable enzymes. The lack of incorporation of inosine, hypoxanthine, xanthine, formate or glycine into nucleotides indicates an absence of de novo purine synthesis. Only adenine, adenosine, guanine and guanosine are salvaged, and no interconversion of these purines was detected. Salvage of these purines and their nucleosides is accomplished by adenine phosphoribosyltransferase, adenosine hydrolase, guanosine phosphonbosyltransferase and guanine hydrolase. The absence of de novo pyrimidine synthesis was confirmed by the lack of incorporation of bicarbonate, orotate and aspartate into nucleotides, and by the lack of detectable levels of the enzymes of de novo pyrimidine synthesis. Salvage appears to be accomplished by the action of uracil phosphoribosyltransferase, uridine hydrolase, uridine phosphotransferase, cytidine deaminase, cytidine hydrolase, cytosine phosphoribosyltransferase and thymidine phosphotransferase. Nucleotides of uracil may be converted to nucleotides of cytosine by cytidine triphosphate synthetase, but thymidylate synthetase and dihydrofolate reductase activities were not detected. Uptake of pyrmidine nucleosides, and perhaps pyrimidines, appears to be accomplished by carrier-mediated transport, and the common site for uptake of uridine and cytidine is distinct from the site for thymidine. Thymine does not appear to be incorporated into nucleotide pools. Giardia trophozoites appear to rely on preformed lipids rather than synthesizing them de novo. Major lipids include phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, sphingomyelin, sterol (probably cholesterol) and mono-, di- and triacylglycer-ides. The lipid composition of the cysts of G. lamblia isolated from gerbils and G. muris isolated from mice are similar to those obtained from the trophozoites of G. lamblia grown in vitro. The activities of several hydrolases of G. lamblia have been shown to be confined to a single lysosome-like particle population with an equilibrium density of approximately 1.15 in sucrose. Contrary to the trophozoites of Entamoeba and the trichomonads, Giardia trophozoites appear to lack most carbohydrate splitting hydrolases. Calmodulin has been reported in G. lamblia trophozoites, and it appears to have properties similar to the calmodulin isolated from other eucaryotic cells.