Immunochemical characterization for eukaryotic ultraplankton from the Atlantic and Pacific oceans

The eukaryotic algae are an important component of the ultraplankton(<5 µm diameter cells) and contribute substantiallyto the photosynthetic biomass of the oceans. Because of theirsmall size, individual species cannot be easily distinguishedby traditional or epifluorescence microscopy. To examine thecomposition of the eukaryotic ultraplankton assemblage, immunofluorescenceprobes produced to strains thought to be representative of theultraplankton (Emiliania huxleyi clone BT-6; Pycnococcus provasoliiclone     

Taste preferences and feeding behavior of three-spined stickleback Gasterosteus aculeatus of populations of basins of the Atlantic and Pacific oceans

The absence of population specificity of taste spectra in fish was confirmed. It was found that the three-spined stickleback Gasterosteus aculeatus of populations of the North (Norway), Baltic (Latvia), and Okhotsk (Kamchatka Peninsula) seas has similar taste preferences to classical taste substances (sodium chloride, calcium chloride, and sucrose—10%; citric acid—5%) and to 21 free amino acids (L-isomers, 0.1–0.001 M). For fish of all populations, glutamine, glutamic and aspartic acids, and alanine have the most attractive taste; cysteine, asparagine, and histidine have slightly less attractive taste. In Baltic Sea and Sea of Okhotsk sticklebacks, relatively not numerous amino acids that cause a significant decrease in pellet consumption—phenylalanine, tryptophane, leucine, and tyrosine—coincide (in the North Sea stickleback, substances with deterrent taste were not revealed). In sticklebacks of different populations, no differences in manifestation of feeding behavior were found, and correlations between different elements of fish response to pellets are similar or close the same. It was shown that intraoral sensory testing of food objects in three-spined stickleback can proceed along two alternative behavioral stereotypes similar in fish of the studied populations. The dependence of stereotypes of intraoral testing on taste qualities of the food object was revealed for the first time.     

Mitochondrial DNA variation in Drosophila pseudoobscura and related species in Pacific northwest populations

We have analysed mitochondrial DNA (mtDNA) from Pacific Northwest populations of Drosophila pseudoobscura, D. persimilis, and D. miranda using six restriction enzymes. We find that HpaII restriction sites are hypervariable compared to the other enzymes used. This hypervariability allows construction of a maximum parsimony map linking each mtDNA genotype. Small insertions, possibly tandem duplications, appear to have arisen concomitantly with, or subsequent to, speciation events, perhaps within the A + T rich region. Convergence of mtDNA genotypes is also evident. Unlike findings for other populations of these species, we find little evidence of mitochondrial introgression between D. pseudoobscura and D. persimilis, despite their ability to produce fertile hybrid females.     

Phylogenetic diversity of subsurface marine microbial communities from the Atlantic and Pacific Oceans.

The extent of the diversity of marine prokaryotes is not well known, primarily because of poor cultivability. However, new techniques permit the characterization of such organisms without culturing, via 16S rRNA sequences obtained directly from biomass. We performed such an analysis by polymerase chain reaction amplification with universal primers on five oligotrophic open-ocean samples: from 100-m (three samples) and 500-m depths in the western California Current (Pacific Ocean) and from a 10-m depth in the Atlantic Ocean near Bermuda. Of 61 clones, 90% were in clusters of two or more related marine clones obtained by ourselves or others. We report 15 clones related to clone SAR 11 found earlier near Bermuda (S. J. Giovannoni, T. B. Britschgi, C. L. Moyer, and K. G. Field, Nature [London] 345:60-63, 1990), 11 related to marine cyanobacteria, 9 clustered in a group affiliated with gram-positive bacteria, 9 in an archaeal cluster we recently described (mostly from the 500-m sample), 4 in a novel gamma-proteobacterial cluster, and 6 in three two-membered clusters (including other archaea). One clone was related to flavobacteria. Only the cyanobacteria plus one other clone, related to Roseobacter denitrificans (formerly Erythrobacter longus Och114), were within 10% sequence identity to any previously sequenced cultured organism in a major data base. We never found more than two occurrences of the same sequence in a sample, although four times we found identical sequences between samples, two of which were between oceans; one of these sequences was also identical to SAR 11.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sperm polymorphism within the sea urchin Strongylocentrotus droebachiensis: divergence between Pacific and Atlantic oceans

The rapid evolution of traits related to fertilization such as sperm morphology may be pivotal in the evolution of reproductive barriers and speciation. The sea urchin Strongylocentrotus droebachiensis has a circumarctic distribution and shows substantial genetic subdivision between northeastern Atlantic populations and northwestern Atlantic and Pacific populations. Using transmission electron microscopy, we show here that sperm shape, size, and ultrastructure differ markedly among populations of S. droebachiensis from different oceans and reflect patterns of genetic divergence. Sperm nuclei from northwestern Atlantic and Pacific populations were longer and narrower than those from the northeastern Atlantic. We additionally demonstrate population-level differences in the amount and location of filamentous actin (F-actin) prior to the occurrence of the acrosome reaction. Sperm from Pacific and northwest Atlantic populations differed from that of all other echinoids examined in that intact sperm contains a partly preformed acrosomal process, a structure more closely resembling the acrosomal rod seen in some molluscs. Immunofluorescent studies using anti-bindin antibodies and the F-actin-specific stain phalloidin confirmed these findings. Divergence of reproductive traits such as sperm morphology may be related to divergence in gamete compatibility and genetic divergence, and could represent the first stages of speciation in free-spawning marine invertebrates.     

Niche-partitioning of Prochlorococcus populations in a stratified water column in the eastern North Atlantic Ocean.

The in situ community structure of Prochlorococcus populations in the eastern North Atlantic Ocean was examined by analysis of Prochlorococcus 16S rDNA sequences with three independent approaches: cloning and sequencing, hybridization to specific oligonucleotide probes, and denaturing gradient gel electrophoresis (DGGE). The hybridization of high-light (HL) and low-light (LL) Prochlorococcus genotype-specific probes to two depth profiles of PCR-amplified 16S rDNA sequences revealed that in these two stratified water columns, an obvious niche-partitioning of Prochlorococcus genotypes occurred. In each water column a shift from the HL to the LL genotype was observed, a transition correlating with the depth of the surface mixed layer (SML). Only the HL genotype was found in the SML in each water column, whereas the LL genotype was distributed below the SML. The range of in situ irradiance to which each genotype was subjected within these distinct niches was consistent with growth irradiance studies of cultured HL- and LL-adapted Prochlorococcus strains. DGGE analysis and the sequencing of Prochlorococcus 16S rDNA clones were in full agreement with the genotype-specific oligonucleotide probe hybridization data. These observations of a partitioning of Prochlorococcus genotypes in a stratified water column provide a genetic basis for the dim and bright Prochlorococcus populations observed in flow cytometric signatures in several oceanic provinces.     

Synonymy in peperomia berteroana (Piperaceae) results in biological disjunction between Pacific and Atlantic oceans

Placing Peperomia berteroana of the Juan Fernandez Islands in the Pacific Ocean in synonymy with P. tristanensis of Tristan da Cunha in the Atlantic Ocean results in a species with a wide geographical disjunction of more than 5000 km. Morphological data indicate that these taxa are best treated as subspecies (P. berteroana subsp. berteroana and P. berteroana subsp. tristanensis).     

Quantitative biochronology of Pliocene and early Pleistocene calcareous nannofossils from the Atlantic,Indian and Pacific oceans

Semi-quantitative methods have been used to refine the precision with which Pliocene and early Pleistocene nannofossil datums may be applied for biostratigraphic purposes. Using these methods, the datums may be applied with a precision of between 0.01 m.y. (e.g.Calcidiscus macintyrei andDiscoaster brouweri) and 0.2 m.y. (e.g.Discoaster asymmetricus). The age of each datum is estimated by interpolation between magnetic reversals, so that the uncertainty in each age estimate is a function of proximity to the nearest reversal as well as of uncertainties in the reversal chronology but is probably better than 0.1 m.y. for all the datums studied here.The following ages are estimated for biostratigraphically useful datums: LADHelicosphaera sellii, 1.37 Ma (diachronous; earlier outside the equatorial zone); LADCalcidiscus macintyrei, 1.45 Ma; LADDiscoaster brouweri, 1.88 Ma; LADDiscoaster asymmetricus, 2.2 Ma; LAD DisDiscoaster pentaradiatus, 2.35 Ma; LADDiscoaster surculus, 2.41 Ma; LADDiscoaster tamalis, 2.65 Ma; LADDiscoaster variabilis, 2.90 Ma; LADSphenolithus spp., 3.45 Ma; LADReticulofenestra pseudoumbilica, 3.56 Ma; LADAmaurolithus delicatus, 3.66 Ma; FADCeratolithus rugosus, 4.62 Ma.The final 0.15 m.y. of the range ofDiscoaster brouweri is characterised by a high (about 20%) proportion of the triradiate form, which is a useful pointer for the extinction of this species even in the presence of considerable reworking.     

Differences in species diversity of Monogenea between the Pacific and Atlantic Oceans

Data from five extensive surveys each in the Pacific and Atlantic Oceans show that relative species diversity (number of parasite species per host species) of gill Monogenea of coastal marine fishes is greater in the northern and southwestern Pacific than in the northeastern and central- and southwestern Atlantic. Relative species diversity is markedly lower in the cold northeastern Atlantic than in the warmer parts of the Atlantic examined, and in the northern Pacific than in the warm southwestern Pacific. The difference between the northern Pacific and Atlantic is entirely or almost entirely due to a much greater number of species of Gyrodactylidae in the northern Pacific. A species-area relationship cannot explain the difference, because the area of the northern Pacific is not larger than that of the northern Atlantic and because Gyrodactylidae are cold-water forms which cannot have immigrated from warmer seas. The difference is tentatively explained by an evolutionary time hypothesis: more species of Gyrodactylidae have accumulated in the much older Pacific than in the Atlantic Ocean. Alternatively, an ecological time hypothesis may explain the difference: ice sheets during the last glaciation covered much more of the continental shelf in the northern Atlantic than in the northern Pacific, possibly extinguishing more Monogenea in the former than in the latter Ocean.     

Detection of novel Fibrobacter populations in landfill sites and determination of their relative abundance via quantitative PCR

Members of the bacterial genus Fibrobacter have long been considered important components of the anaerobic cellulolytic community in the herbivore gut, but their presence and activity in other environments is largely unknown. In this study, a specific polymerase chain reaction (PCR) primer set, targeting the 16S rRNA gene of Fibrobacter spp., was applied to community DNA from five landfill sites followed by temporal thermal gel electrophoresis (TTGE) analysis of cloned amplification products. Phylogenetic analysis of clone sequences indicated the presence of novel clusters closely related to the genus Fibrobacter . There are two named species, Fibrobacter succinogenes and F. intestinalis , and only two of the 58 sequenced clones were identified with them, and both were F. succin ogenes. The clone sequences from landfill were recovered in five distinct clusters within the Fibrobacter lineage, and four of these were novel. Quantitative PCR (qPCR) assays of reverse-transcribed community RNA from landfill leachates and rumen fluid samples indicated that the abundance of Fibrobacter spp. relative to total bacteria varied from 0.2% to 40% in landfill, and 21% to 32% in the rumen, and these data demonstrate that fibrobacters can be a significant component of the microbial community in landfill ecosystems. This is the first evidence for Fibrobacter spp. outside the gut ecosystem, and as the only cultivated representatives of this group are actively cellulolytic, their diversity and abundance points to a possible role in cellulose hydrolysis in landfill, and perhaps other anaerobic environments also.     

New findings of rare fish species in Indian and Pacific oceans with the description of two new species from the families Gobiidae and Platycephalidae

We provide information about the morphology and new findings of 15 rare fish species from the families Bathyclupeidae, Callionymidae, Champsodontidae, Cottidae, Gobiidae, Lophichthyidae, Melanostomiidae, Moridae, Oneirodidae, Paralepididae, Pegasidae, Platycephalidae, and Uranoscopidae. Two new species are described: Thysanophrys haploblepharis sp. n. (Platycephalidae) from the Western Indian Ocean and Vanderhorstia stegauchenia sp. n. (Gobiidae) from the South China Sea. The new synonymy is established: Cottus dybowskii Hilgendorf, 1879 = Myoxocephalus brandtii.     

Taxon-specific probes for the cellulolytic genus Fibrobacter reveal abundant and novel equine-associated populations.

A total of six 16S rRNA targeted oligonucleotide probes were used to quantify Fibrobacter abundance and diversity in the gastrointestinal contents of a pony. Approximately 12% of the total 16S rRNA extracted from cecal contents hybridized with a Fibrobacter genus-specific probe and a Fibrobacter succinogenes species-specific probe. However, no significant hybridization was observed with a probe for the species. Fibrobacter intestinalis or with three probes for F. succinogenes subspecies. This suggested the presence of a previously undescribed population of F. succinogenes-like organisms. Novel lineages of F. succinogenes were subsequently identified by using PCR primers specific for the genus to amplify sequences coding for 16S rRNA from DNA extracted from cecal contents. Sequences of the cloned amplification products were shown to be affiliated with F. succinogenes but represented two distinct, and novel, lines of descent within the species.     

Variations of antioxidant enzymes in Daphnia species and populations as related to ambient UV exposure

To assess their role in photoprotection in the crustacean zooplankton Daphnia spp., activities of the antioxidants catalase (CAT), superoxide dismutase (SOD), glutathione transferase (GST) and content of carotenoids (CAR) were studied in 4 Daphniaspecies from a total of 50 populations. Included in the survey were alpine and lowland populations of both pigmented and non-pigmented D. longispina, rock-pool and laboratory clones of D. magna and Arctic populations of the D. pulex/D. middendorffianacomplex. Most of the surveyed populations inhabit shallow ponds, and are thus highly exposed to UV-radiation during the summer. The results are primarily discussed in relation to antioxidants as possible protection against UV-radiation. D. pulex, D. middendorffianaand D. longispinaoccurred both as hyaline and pigmented (carapace melanization) morphs. The most notable inter-species differences were the high activity of CAT in the D. magnalab-clone, the low activity of GST in melanic animals from the D. pulexgroup and the high activity of SOD in D. longispinafrom a lowland humic pond. Contrary to expectations, we found no differences in antioxidant capacity between melanic and non-pigmented alpine D. longispina. Intraspecies variation in antioxidant activities was studied in relation to pond characteristics. Among the alpine populations of D. longispina there was a significant positive correlation between absorbance (300 nm) of the pond water and CAT activity, which could be related to ambient levels of photoinduced hydrogen peroxide production in these small water bodies. The data from this comparative study provide insight in photo-protective mechanisms in cladocera, and constitute a valuable basis for future research on pro-oxidant and antioxidant processes in alpine and arctic freshwater zooplankton.