β-Oxidation capacity in liver increases during parr-smolt transformation of Atlantic salmon fed vegetable oil and fish oil

Atlantic salmon Salmo salar were fed diets containing 100% fish oil (FO; capelin oil) or 100% vegetable oil (VO) from start of feeding until the fish reached the size of 2·5 kg. Samples were taken during the period of the parr-smolt transformation (October 2002 to February 2003). The VO diet consisted of a blend of 55% rapeseed oil, 30% palm oil and 15% linseed oil to maintain the sum of saturated, monounsaturated and polyunsaturated fatty acids between the two diets, although with differences in the individual chain length of fatty acids. Na⁺/K⁺-ATPase activity in the gills, total β-oxidation capacity in muscles and liver and total lipid, glycogen and dry matter content in the muscles were measured during the parr-smolt transformation and after seawater transfer. Na⁺/K⁺-ATPase activity in gills increased prior to seawater transfer, showing an adaptation for seawater survival. Major changes in the lipid and glycogen content in the fillet and in β-oxidation capacity were found in the tissues measured. β-oxidation capacity increased significantly in liver and decreased in red muscle, prior to seawater transfer, giving liver an important role in energy production during this period. Results also indicated that feeding Atlantic salmon a diet where 100% of FO was replaced with VO did not have any negative effects on lipid metabolism during parr-smolt transformation.     

Tests of hypotheses on predation as a factor maintaining polymorphic melanism in coastalplain fox squirrels (Sciurus niger L.)

Fox squirrels ( Sciurus niger ) in the south-eastern U.S. coastal plain differ from those in the rest of the species' range by having black heads with white nose and ears. Postcranially on the dorsum, they also show interindividual colour variation, ranging from all-light agouti to all-black non-agouti. I present results of experiments undertaken to test whether the evolution of these pigmentary features can be attributed to interactions with predators. Comparative static crypsis (when the squirrels are still) was tested by determining how well specimens of the squirrel morphs matched their backgrounds in terms of intensity (brightness) distributions and patch size. Comparative dynamic effects (when the squirrels are moving) were tested using captive red-tailed hawks ( Buteo jamaicensis ) and models of the fox squirrel morphs. Results indicated that morphs of coastal-plain fox squirrels with all-light backs are better static matches to unburned backgrounds than are the darker morphs with which they coexist. Against fire-blackened backgrounds, fox squirrel morphs with intermediate and all-black backs are better intensity matches than those with all-light backs, but the dark morphs are not better patch-length matches than light morphs. The superiority of dark morphs in intensity matching for a short time after a fire does not seem sufficient to account for their long-term maintenance. Hawks responded more slowly to moving fox squirrel models with intermediate amounts of black on the back than to all-light or all-dark morphs; this result suggests a possible factor that would favour retention of genes for dorsal blackness in the coastal-plain population. Patchy black and white heads appear to promote static crypsis of south-eastern fox squirrels, and hawks reacted more slowly to moving squirrel models with such colouration than to those with plain heads.     

Comparative analysis of sulfated galactans from red algae by reductive hydrolysis and mild methanolysis coupled to two different HPLC techniques

The sugar determination of the sulfated galactans, agars and carrageenans of various red algae was performed using two different techniques of depolymerisation with subsequent HPLC analysis: 1) reductive hydrolysis/ HPAEC-PAD; 2) mild methanolysis/ RPLC-DR. Both techniques were optimized to release quantitatively the composite sugars (galactose, 6-O-methyl-galactose, the labile 3,6-anhydrogalactose and 2-O-methyl-3,6-anhydrogalactose residues) and precise relative response factors of authentic 3,6-anhydrogalactose were determined. The methanolysate neutralisation step, performed subsequently to methanolysis depolymerisation, was demonstrated as a key step for the quantitative recovery of the anhydrogalactose residues. The yield of the main sugars released by the two techniques were in good agreement for the commercial agarose and iota and kappa carrageenans studied. This revised version was published online in June 2006 with corrections to the Cover Date.     

Molecular population genetics of the red kangaroo (Macropus rufus): mtDNA variation

The genetic population structure of a large, wide-ranging marsupial, the red kangaroo ( Macropus rufus ) was assessed using sequence and haplotype frequency data of mitochondrial DNA (mtDNA) from locations across the species range in Australia. Results from sequence data revealed extensive haplotype diversity within the red kangaroo (32/34 sequences were unique). Sequence diversity was distributed within rather than between geographical regions across the species range. Genetic connectivity across the range of the species has therefore been maintained over the long term. On a smaller within-region scale, significant genetic structuring was evident from heterogeneity of haplotype frequencies amongst sampling sites. The geographical scale of panmictic populations differed across the continent with more restricted genetic populations occurring in areas with greater topographic and habitat complexity. We propose that these differences in area of genetic populations are the result of population responses to limiting ecological factors during drought.     

An evaluation of RAPD fragment reproducibility and nature

Random amplified polymorphic DNA (RAPD) fragment reproducibility was assayed in three animal species: red deer ( Cervus elaphus ), wild boar ( Sus scrofa ) and fruit fly ( Drosophila melanogaster ). Ten 10-mer primers (Operon) were tested in two replicate reactions per individual under different stringency conditions (annealing temperatures of 35 °C or 45 °C). Two estimates were generated from the data: autosimilarity, which tests the reproducibility of overall banding patterns, and band repeatability, which tests the reproducibility of specific bands. Autosimilarity (the similarity of individuals with themselves) was lower than 1 for all three species ranging between values of 0.66 for Drosophila at 45 °C and 0.88 for wild boar at 35 °C. Band repeatability was estimated as the proportion of individuals showing homologous bands in both replicates. The fraction of repeatable bands was 23% for deer, 36% for boar and 26% for fruit fly, all at an annealing temperature of 35 °C. Raising the annealing temperature did not improve repeatability. Phage lambda DNA was subjected to amplification and the pattern of bands compared with theoretical expectations based on nucleotide sequence. Observed fragments could not be related to expected ones, even if a 2bp mismatch is allowed. Therefore, the nature of genetic variation uncovered by the RAPD method is unclear. These data demonstrate that prudence should guide inferences about population structure and nucleotide divergence based on RAPD markers.     

The interplay of ontogeny and scaling in the interactions of fish larvae and their predators

In this review and synthesis, new data from field and laboratory experiments on red drum, Sciaenops ocellatus , larvae as prey to larger fishes are presented to illustrate two approaches to the study of developmental effects on predation. Various sizes and species of predatory fishes imposed very different levels of mortality on experimental populations of red drum larvae. Differences in predator size explained little of the overall variation in mortality rates. In the laboratory, responsiveness of red drum to a single size and species of predatory fish was relatively low through much of the developmental period but increased steadily. Response effectiveness improved and the predator's capture success decreased once the prey exceeded 20 mm in length. General ontogenetic trends in the behavioural interaction of various larvae and their piscine predators are described by combining 22 data sets on a scale of roughly comparable ontogenetic state. This scale, together with absolute and relative measures of predator and prey size, are used to assess the roles of ontogeny and scaling in the predation interaction. Ontogeny is shown to be a significant contributor to changes in responsiveness, response effectiveness, and capture success. The influence of scaling always took the form of an interaction with ontogeny and not a main effect.     

IDENTIFICATION OF GROUP- AND STRAIN-SPECIFIC GENETIC MARKERS FOR GLOBALLY DISTRIBUTED ALEXANDRIUM (DINOPHYCEAE). II. SEQUENCE ANALYSIS OF A FRAGMENT OF THE LSU rRNA GENE1

A fragment of the large-subunit (LSU) ribosomal RNA gene (rDNA) from the marine dinoflagellates Alexandrium tamarense (Lebour) Balech, A. catenella (Whedon et Kofoid) Balech, A. fundyense Balech, A. affine (Fukuyo et Inoue) Balech, A. minutum Halim, A. lusitanicum Balech, and A. andersoni Balech was cloned and sequenced to assess inter- and intraspecific relationships. Cultures examined were from North America, western Europe, Thailand, Japan, Australia, and the ballast water of several cargo vessels and included both toxic and nontoxic isolates. Parsimony analyses revealed eight major classes of sequences, or “ribotypes,” indicative of both species- and strain-specific genetic markers. Five ribotypes subdivided members of the A. tamarense/catenella/ fundyense species cluster (the “tamarensis complex”) but did not correlate with morphospecies designations. The three remaining ribotypes were associated with cultures that clearly differ morphologically from the tamarensis complex. These distinct sequences were typified by 1) A. affine, 2) A. minutum and A. lusitanicum, and 3) A. andersoni. LSU rDNA from A. minutum and A. lusitanicum was indistinguishable. An isolate's ability to produce toxin, or lack thereof, was consistent within phylogenetic terminal taxa. Results of this study are in complete agreement with conclusions from previous work using restriction fragment-length polymorphism analysis of small subunit rRNA genes, but the LSU rDNA sequences provided finer-scale species and population resolution. The five divergent lineages of the tamarensis complex appeared indicative of regional populations; representatives collected from the same geographic region were the most similar, regardless ofmorphotype, whereas those from geographically separated populations were more divergent even when the same morphospecies were compared. Contrary to this general pattern, A. tamarense and A. catenella from Japan were exceptionally heterogeneous, displaying sequences associated with Australian, North American, and western European isolates. This diversity may stem from introductions of A., tamarense to Japan from genetically divergent sources in North America and western Europe. Alexandrium catenella from Japan and Australia appeared identical, suggesting that these two regional populations share a recent, common ancestry. One explanation for this genetic continuity was suggested by A. catenella cysts transported from Japan to Australia via ships' ballast water: the cysts contained LSU rDNA sequences that were indistinguishable from those of known populations of A. catenella in both Japan and Australia. Ships ballasted in South Korea and Japan have also fostered a dispersal of viable A. tamarense cysts to Australia, but their LSU rDNA sequences indicated they are genetically distinct from A. tamarense/catenella previously found in Australia and genetically distinct from each other, as well. Human-assisted dispersal is a plausible mechanism for inoculating a region with diverse representatives of the tamarensis complex from geographically and genetically distinct source populations. The D1-D2 region of Alexandrium LSU rDNA is a valuable taxo-nomic and biogeographic marker and a useful genetic reference for addressing dispersal hypotheses.     

THE INABILITY OF THE TEXAS “BROWN TIDE” ALGA TO USE NITRATE AND THE ROLE OF NITROGEN IN THE INITIATION OF A PERSISTENT BLOOM OF THIS ORGANISM1

A planktonic alga similar in general morphology and pigments to Aureococcus anophagefferens Hargraves and Sieburth has caused persistent and ecologically damaging blooms along the south Texas coast. Experiments using 100 μM NO₃^?, NO₂^?, and NH₄⁺ demonstrated that the alga could not use NO₃^? for growth but could use NO₂^? and NH₄⁺. Doubling iron or trace metal concentrations did not permit growth on NO₃^?. Chemical composition data for cultures grown in excess NO₃^? or NH₄⁺, respectively, were as follows: N·cell^?1 (0.88 vs. 1.3 pg), C:N ratio (25:1 vs. 6.4:1), C:chlorophyll a (chl a) (560:1 vs. 44:1), and chl a·cell^?1 (0.033 vs. 0.16 pg). These data imply that cells supplied with NO₃^? were N-starved. Culture addition of 10 mM final concentration chlorate (a nitrate analog) did not affect the Texas isolate while NO₃^? utilizing A. anophagefferens was lysed, suggesting that the NO₃^? reductase of the Texas isolate is nonfunctional. Rates of primary productivity determined during a dense bloom indicated that light-saturated growth rates were ca. 0.45 d^?1, which is similar to maximum rates determined in laboratory experiments (0.58 d^?1± 0.16). However, chemical composition data were consistent with the growth rate of these cells being limited by N availability (C:N 28, C:chl a 176, chl a·cell^?1 0.019). Calculations based on a mass balance for nitrogen suggest that the bloom was triggered by an input of ca. 69 μM NH₄⁺ that resulted from an extensive die-off of benthos and fish.     

IDENTIFICATION OF GROUP- AND STRAIN-SPECIFIC GENETIC MARKERS FOR GLOBALLY DISTRIBUTED ALEXANDRIUM (DINOPHYCEAE). I. RFLP ANALYSIS OF SSU rRNA GENES1

Two distinct small-subunit ribosomal RNA genes (SSU rDNAs), termed the “A gene” and “B gene,” were recently found in the toxic dinoflagellate Alexandrium fundyense Balech. A restriction fragment length polymorphism (RFLP) assay was developed to rapidly detect the A and B genetic markers. SSU rDNA from 58 cultures with species designations of A. tamarense (Lebour) Balech, A. catenella (Whedon et Kofoid) Balech, A. fundyense, A. affine (Fukuyo et Inoue)Balech, A. minutum Halim, A. lusitanicum Balech, and A. andersoni Balech were screened. These cultures represent toxic and non-toxic isolates from North America, western Europe, Thailand, Japan, Australia, and the ballast water of several cargo ships. The RFLP assay revealed five distinct groups. Three subdivided the A. tamarense/catenella/fundyense“species complex” into clusters defined by geographic origin, not by morphospecies designations. The fourth group consisted of A. affine, whereas the fifth group was represented by A. minutum, A. lusitanicum, and A. andersoni. The B gene was only found in A. tamarense, A. catenella, and A. fundyense, but not in all isolates. However, all North American isolates of this closely related group harbored this gene, and it also was found in some A. tamarense from scattered locations in Japan and in the ballast water of one ship that operated exclusively between Japan and Australia. Isolates without the B gene appeared to have only a single class of SSU rDNA. The B sequence was not essential for toxin production, but thus far those organisms harboring it were toxic. The A. tamarense/catenella/fundyense complex is composed of genetically distinct populations, within which may exist two or all three of the mophotypically defined species. The B gene is a promising taxonomic and biogeographic marker and may be useful for tracking the regional and/or global dispersal of particular populations.     

The role of sugar, vitrification and membrane phase transition in seed desiccation tolerance

In a search for the mechanism of desiccation tolerance, a comparison was made between orthodox (desiccation-tolerant) soybean ( Glycine max [L.] Merrill) and recalcitrant (desiccation-intolerant) red oak ( Quercus rubra L.) seeds. During the maturation of soybean seeds, desiccation tolerance of seed axes is correlated with increases in sucrose, raffinose and stachyose. In cotyledons of mature oak seeds, sucrose levels are equal to those in mature soybeans, but oligosaccharides are absent. By using the thermally stimulated current method, we observed the glassy state in dry soybean seeds during maturation. Oak cotyledons showed the same phase diagram for the glass transition as did mature soybeans. By using X-ray diffraction, we found the maturation of soybeans to be associated with an increased ability of membranes to retain the liquid crystalline phase upon drying, whereas the mature oak cotyledonary tissue existed in the gel phase under similar dry conditions. These findings lead to the conclusion that the glassy state is not sufficient for desiccation tolerance, whereas the ability of membranes to retain the liquid crystalline phase does correlate with desiccation tolerance. An important role for soluble sugars in desiccation tolerance is confirmed, as well as their relevance to membrane phase changes. However, the presence of soluble sugars does not adequately explain the nature of desiccation tolerance in these seeds.