Characterization of the selenite uptake mechanism in the coccolithophore Emiliania huxleyi (Haptophyta)

The marine coccolithophore Emiliania huxleyi (Haptophyta) requires selenium as an essential element for growth, and the active species absorbed is selenite, not selenate. This study characterized the selenite uptake mechanism using ??Se as a tracer. Kinetic analysis of selenite uptake showed the involvement of both active and passive transport processes. The active transport was suppressed by 0.5 mM vanadate, a membrane-permeable inhibitor of H?-ATPase, at pH 8.3. When the pH was lowered from 8.3 to 5.3, the selenite uptake activity greatly increased, even in the presence of vanadate, suggesting that the H? concentration gradient may be a motive force for selenite transport. [??Se]Selenite uptake at selenite-limiting concentrations was hardly affected by selenate, sulfate and sulfite, even at 100 μM. In contrast, 3 μM orthophosphate increased the K(m) 5-fold. These data showed that HSeO??, a dominant selenite species at acidic pH, is the active species for transport through the plasma membrane and transport is driven by ΔpH energized by H?-ATPase. Kinetic analysis showed that the selenite uptake activity was competitively inhibited by orthophosphate. Furthermore, the active selenite transport mechanism was shown to be induced de novo under Se-deficient conditions and induction was suppressed by the addition of either sufficient selenite or cycloheximide, an inhibitor of de novo protein synthesis. These results indicate that E. huxleyi cells developed an active selenite uptake mechanism to overcome the disadvantages of Se limitation in ecosystems, maintaining selenium metabolism and selenoproteins for high viability.     

The long-term culture of the coccolithophore Pleurochrysis carterae (Haptophyta) in outdoor raceway ponds

The calcareous marine haptophyte algae, the coccolithophorids, are of global environmental significance because of the impact of their blooms on the carbon cycle. The coccolithophorid, Pleurochrysis carterae was grown semi-continuously in paddlewheel-driven outdoor raceway ponds over a period of 13 months in Perth, Western Australia. The mean total dry weight productivity of P. carterae was 0.19 g.L⁻¹.d⁻¹ with cell lipid and CaCO₃ contents of up to 33% and 10% of dry weight respectively, equivalent to an annual total biomass productivity of about 60 t.ha⁻¹.y⁻¹ and 21.9 t.ha⁻¹.y⁻¹ total lipid and 5.5 t.ha⁻¹.y⁻¹ total calcium carbonate production. Throughout the culture period there was little protozoan contamination or contamination by other algae. The pH of the growth medium increased to pH 11 during the day and was found to be a useful variable for monitoring the state of the culture. A comparison of the growth of P. carterae and Dunaliella salina in the raceway ponds showed no significant differences between these two species with regard to areal total dry weight productivity and lipid content.     

Spatial dynamics of coccolithophore assemblages in the Equatorial Western-Central Pacific Ocean

The spatial distribution of living coccolithophores was studied in the Western-Central Equatorial Pacific Ocean during November–December, 1990 and September–October, 1992. The highest local concentration of coccolithophores occurred at the thermocline in well-stratified waters, but at sea-surface level in dynamic waters. In total, 111 coccolithophore taxa were recognized, some of which exhibited hydrographically controlled variation in their absolute abundance. Gephyrocapsa oceanica and Oolithotus antillarum were abundant in the upwelling front. Most of the lower photic dwellers were abundant in the tropical to subtropical stations regardless of the water stratification. The coccolithophore flora of well-stratified waters could be distinguished from the upwelling front flora by the higher abundance of Umbellosphaera irregularis and lower abundance of G. oceanica. The temperature mixed-water flora was characterized by a high abundance of Emiliania huxleyi. The vertical distribution of all coccolithophore taxa, except three placolith-bearing species, Gephyrocapsa ericsonii, G. oceanica and E. huxleyi, was controlled by upper photic-zone temperature and water stratification. The upper or lower vertical distribution limits of many coccolithophore taxa coincided with the top of the thermocline. The most common 27 taxa were grouped into four ecological groups, Upper Photic-zone Group (UPG), Middle Photic-zone Group (MPG), Lower Photic-zone Group (LPG) and Omnipresent Group (OPG), on the basis of their vertical distribution. By analyzing the hydrographic control on the vertical distribution of these four ecological groups, four ecological assemblages were recognized: High Temperature; Warm Oligotrophic; Warm Eutrophic; and Temperate Mixed-water Assemblages. In equatorial waters, the total coccolithophore assemblage across the photic-zone was controlled by the population in the upper photic-zone. The UPG monopolized the upper photic-zone flora in the High Temperature Assemblage. In the Warn Oligotrophic-water Assemblage, common OPG accompanied abundant UPG in the upper photic-zone. The upper photic-zone of the Warm Eutrophic Assemblage consisted of UPG, MPG and OPG.Emiliania huxleyi and Gephyrocapsa oceanica, the major component of OPG, displayed intra-specific morphological variations. G. oceanica Type 1 was restricted to the upper photic-zone of well-stratified oligotrophic waters. Conversely, in these waters E. huxleyi Type C and G. oceanica Type 2 only occurred below the thermocline. These two taxa also coexist with G. oceanica Type 3 and E. huxleyi Type A in the upper photic zone of dynamic waters.     

Genetic delineation between and within the widespread coccolithophore morpho‐species Emiliania huxleyi and Gephyrocapsa oceanica (Haptophyta)

Emiliania huxleyi and Gephyrocapsa oceanica are abundant coccolithophore morpho‐species that play key roles in ocean carbon cycling due to their importance as both primary producers and cal‐cifiers. Global change processes such as ocean acidification impact these key calcifying species. The physiology of E. huxleyi, a developing model species, has been widely studied, but its genetic delineation from G. oceanica remains unclear due to a lack of resolution in classical genetic markers. Using nuclear (18S rDNA and 28S rDNA), mitochondrial (cox1, cox2, cox3, rpl16, and dam), and plastidial (16S rDNA, rbcL, tufA, and petA) DNA markers from 99 E. huxleyi and 44 G. oceanica strains, we conducted a multigene/multistrain survey to compare the suitability of different markers for resolving phylogenetic patterns within and between these two morpho‐species. The nuclear genes tested did not provide sufficient resolution to discriminate between the two morpho‐species that diverged only 291Kya. Typical patterns of incomplete lineage sorting were generated in phylogenetic analyses using plastidial genes. In contrast, full morpho‐species delineation was achieved with mitochondrial markers and common intra‐morpho‐species phylogenetic patterns were observed despite differing rates of DNA substitution. Mitochondrial genes are thus promising barcodes for distinguishing these coccolithophore morpho‐species, in particular in the context of environmental monitoring.     

Vertical and lateral variations in coccolithophore community structure across the subtropical frontal zone in the South Atlantic Ocean

In this study the coccolithophore compositions of 11 plankton depth stations along a N–S transect from the South Atlantic Subtropical Gyre to the Subantarctic Zone were examined qualitatively and quantitatively. The lateral and vertical distribution patterns of not only the most abundant taxa but also of the morphotypes of distinct species complexes, such as Calcidiscus leptoporus, Emiliania huxleyi, and Umbellosphaera tenuis were the focus. Geographic variation among morphotypes mirrors different ecological affinities of the members of a species complex. Multivariate statistics were used to infer the relationship between a set of known environmental data and species concentrations. The results of the detrended Canonical Correspondence Analysis (CCA) revealed the presence of distinct species assemblages. The Subtropical Gyre assemblage within the upper 50 m of the photic zone is mainly composed of Umbellosphaera irregularis, U. tenuis types III and IV, Discosphaera tubifera, Rhabdosphaera clavigera, S. pulchra and E. huxleyi var. corona, adapted to warm and oligotrophic conditions. In the deeper photic zone abundant Florisphaera profunda, Gephyrocapsa ericsonii and Oolithotus spp. are encountered, benefiting from higher nutrient concentrations in the vicinity of the nutricline. A well-defined Subtropical Frontal Zone (STFZ) association is clearly dominated by E. huxleyi types A and C throughout the upper 100 m of the water column. Secondary contributors in the upper photic zone are Syracosphaera spp. (mainly S. histrica, S. molischii), Michaelsarsia elegans, Ophiaster spp. and U. tenuis type II. This assemblage is associated with cooler, nutrient-rich waters. E. huxleyi type B is found deeper in the water column. Here it is accompanied by Algirosphaera robusta, G. muellerae, and S. anthos indicating a tolerance of lower light availability in environments with elevated productivity. C. leptoporus spp. leptoporus shows relatively high cell numbers in all sampled water levels throughout the STFZ. Interestingly, its coccoliths are often smaller 5 μm in lith diameter. The mean coccolithophore assemblages of a station were compared to the underlying surface sediment assemblages. For the most part, the distribution of the morphotypes is reflected in the sedimentary archive, thus proving their potential as paleoecological proxies.     

Lack of spermatogenic variation in a polymorphic lizard,Sceloporus aeneus (Squamata: Phrynosomatidae)

Although different mechanisms exist to explain the presence of polymorphism in lizards, one model suggests that multiple morphotypes display the same level of fitness. Three male morphs (grey, yellow and orange) coexist in Sceloporus aeneus, a Mexican endemic oviparous lizard. Using a histological perspective, we test the hypothesis that spermatogenic output does not vary across morphotypes of S. aeneus during its maximum testicular activity. Males of S. aeneus (five grey, five yellow and five orange) were collected in Calimaya, Estado de México, Mexico. Snout-vent length (SVL), testis mass, diameter and epithelial heights for the seminiferous tubules and epididymis, and the number of layers of germ cells did not vary among morphs; moreover, according to principal component analysis, a high overlap among lateral colour morphs exists. Our results suggest strongly that the lateral colour morphs in S. aeneus have the same spermatogenic output, and natural selection may be a stronger driving force than sexual selection within this species. Further studies into other lizard species with multiple morphotypes are required to determine whether the lack of variation in spermatogenic output observed in this endemic lizard is consistent across polymorphic species which will provide a greater understanding of the selective mechanisms acting on an individual’s fitness.     

Cryopreservation of the coccolithophore, <Emphasis Type="Italic">Emiliania huxleyi</Emphasis> (Haptophyta,Prymnesiophyceae)

We studied the cryopreservation of the most common coccolithophore, Emiliania huxleyi which is considered as one of the main global carbon cycle participants. Both stages of this complex life cycle species were submitted to gradual addition of three distinct cryoprotectants: dimethylsulfoxide (7.5% v/v), methanol (5% v/v) and proline (0.5 M). They were then control-rate cooled (−5 °C min⁻¹) to −50 °C before plunging into liquid nitrogen. Free radical oxygen species have been proposed to occur in cells subjected to pre-freezing manipulation or to cooling. Therefore, catalase (preventing accumulation of hydroxyl radicals) was evaluated for its ability to improve cell viability before and after freezing-thawing challenge. With the exception of proline which induced a decrease in diploid cell proliferation, cryoprotectants had no deleterious effects. On the contrary, growth of the haploid stage was enhanced by each CPA treatment, suggesting mixotrophic growth. Cryopreservation succeeded when dimethylsulfoxide was used, and the late exponential phase was obtained as soon as the 15th post-thawing day. Cell densities were then similar to the unfrozen controls. Catalase had no beneficial effect on the ability of cells to grow, neither prior freezing nor after thawing. In comparison with former attempts to cryopreserve E. huxleyi in other culture collection centers, our protocols allowed faster recovery.     

Biodiversity of peracarid crustaceans(Malacostraca) from the shelf downto the deep Arctic Ocean

During three expeditions with the RVs Meteor and Polarstern more than sixty thousand peracarids were sampled from the deep Arctic Ocean (northern North Atlantic) by means of an epibenthic sledge. Sampling areas were the Kolbeinsey Ridge north of Iceland (800–1100 m), the Northeast Water Polynya, off Greenland (45–517m), and 75°N east of Greenland (197–2681m). Until now 288 species of Peracarida have been identified to species level. These 288 species comprise 152 genera and 59 families of Amphipoda, Cumacea, Isopoda, Mysidacea and Tanaidacea. Thirty-eight genera were very frequent and were sampled at each expedition (these were 22 species of Isopoda, seven species of Cumacea, three species of Amphipoda and Mysidacea, each, and two species of Tanaidacea). Sixty genera are eurybathic, occurring at least over a depth range of 1000m, some even from the shelf up to 2681m depth. Only 10 genera are stenobathic, occurring only in the deep sea. No significant decrease in species number with depth or latitude could be observed. The influencing factors probably causing different community structures are diverse, ranging from food availability over substrate or hydrographical qualities to interspecific competition.     

Integrative taxonomy of the Pavlovophyceae (Haptophyta): a reassessment

The Pavlovophyceae (Haptophyta) contains four genera (Pavlova, Diacronema, Exanthemachrysis and Rebecca) and only thirteen characterised species, several of which are important in ecological and economic contexts. We have constructed molecular phylogenies inferred from sequencing of ribosomal gene markers with comprehensive coverage of the described diversity, using type strains when available, together with additional cultured strains. The morphology and ultrastructure of 12 of the described species was also re-examined and the pigment signatures of many culture strains were determined. The molecular analysis revealed that sequences of all described species differed, although those of Pavlova gyrans and P. pinguis were nearly identical, these potentially forming a single cryptic species complex. Four well-delineated genetic clades were identified, one of which included species of both Pavlova and Diacronema. Unique combinations of morphological/ultrastructural characters were identified for each of these clades. The ancestral pigment signature of the Pavlovophyceae consisted of a basic set of pigments plus MV chl cPAV, the latter being entirely absent in the Pavlova + Diacronema clade and supplemented by DV chl cPAV in part of the Exanthemachrysis clade. Based on this combination of characters, we propose a taxonomic revision of the class, with transfer of several Pavlova species to an emended Diacronema genus. The evolution of the class is discussed in the context of the phylogenetic reconstruction presented.     

Morphological variation in the palaeonemertean Tubulanus annulatus (Montagu, 1804)

Previous studies on the palaeonemertean Tubulanus annulatus have hinted on possible geographic variation, or even a species complex. This study describes the variation in morphology, focusing on the characters that have been supposed to vary geographically. Specimens from the Swedish west coast (Tjärnö and Kristineberg), Scottish west coast (Millport), and the Mediterranean (Naples and Split) were included in the study. It is concluded that the pattern of variation in the studied characters do not correspond to geography and most of the character states previously thought to vary geographically are in fact found within one and the same population.     

DIVERSITY, TAPHONOMY and PALAEOECOLOGY OF AN ANGIOSPERM FLORA FROM THE CRETACEOUS (CENOMANIAN–CONIACIAN) IN SOUTHERN PATAGONIA, ARGENTINA

Abstract:  This paper describes the diversity, taphonomy and palaeoecology of angiosperm leaves that dominate a palaeoflora of Cretaceous (Cenomanian–Coniacian) age from the Mata Amarilla Formation in the Austral Basin, south-west Patagonia, Argentina. Twelve morphotypes of angiosperm leaves are recognized based on foliar morphotype analysis of more than 500 specimens. These were divided into six morphological groups based on major architectural patterns. The relative dominance of these morphotypes, mode of preservation and relationship with sedimentary facies were evaluated from two levels within the formation. This analysis identified two different plant palaeocommunities. The lower, María Elena, level (MEL) was deposited in a marine coastal area on a subaerial delta plain; the dominant angiosperm morphotypes preserved in it are group 1 (MA100) and group 2 (MA101, 102); morphotypes MA109 and 110 are scarce but exclusive to this level. The upper, Mata Amarilla, level (MAL), accumulated inland in flood-plain environments; the most abundant angiosperm morphotypes are groups 3 (MA103–105), 4 (MA106) and 1 (MA100); morphotypes MA103–105 and 108 are exclusive to this level. Comparisons with other floras of similar age from Antarctica, Australia and New Zealand indicate that the Mata Amarilla flora has a slightly higher morphological diversity of angiosperm leaves, providing the first evidence for an angiosperm-dominated early Late Cretaceous macroflora in south-west Gondwana.     

Morphological variation and phylogenetic relationships in the genus Anginon (Apiaceae)

The variation in habit and morphology of the twelve species of Anginon, a poorly known southern African genus of woody Apiaceae, is discussed and illustrated. The genus Glia is shown to be the obvious outgroup, sharing with Anginon two convincing synapomorphies: 1, the reduction or partial reduction of the laminar part of the leaves, and 2, the heavily cutinized outer walls of the fruit epidermis. Several characters of the internal structure of the fruit, together with other morphological characters, have been analysed by the cladistic method. Our interpretation of character evolution within the genus and a first hypothesis of phylogenetic relationships, showing three distinct infrageneric groups, is presented.     

Biodiversity and historical biogeography of stalked crinoids (Echinodermata) in the deep sea

About 95 species of stalked crinoids are now described from 60m to hadal depths, but our knowledge remains far from complete. Depending on which species concept is used, estimates of species richness can be dramatically different. It is necessary to have a homogeneous concept for taxonomic units. The abundance of the crinoid fossil record allows a discussion of the ancestry of deep sea crinoid fauna. Stalked crinoids have a horizontal diversity pattern with three regional centres of high diversity (i.e. western tropical Pacific, western tropical Atlantic and north-eastern Atlantic). Vertical patterns show two faunal strata which vary in importance among provinces. The epibathyal stratum has apparently remained relatively similar in intertropical areas since the Mesozoic. Despite environmental changes related to glaciation since the Middle Miocene, the deepest crinoid fauna (i.e. the deep sea fauna sensu stricto at depths more than 1000 ± 200 m) have a very ancient origin with a dispersion closely related to plate tectonics. The bathyal fauna on hard substrates includes a few living fossils and has a high historical interest.     

Morphological variation in Polydora ciliata complex (Polychaeta: Annelida)

Intraspecific variation in Polydora ciliata (Johnston) was assessed on the basis of evidence from morphological characters, which were studied by scanning electron microscopy. Differences were observed between populations of P. ciliata with respect to the setae of the fifth modified segment and in the caruncle. Two other species, namely P. ligni Webster and P. limicola (Annenkova), were also studied in order to assess interspecific variation. The two forms of P. ciliata , that is boring and non-boring, were found to be different morphologically.     

Morphological variation in Puya (Bromeliaceae): an allometric study

A group of representative species of the genus Puya was studied to determine if there are allometric relationships between vegetative and floral parts, whether these relationships correlate with their pollination system and if plant size is correlated with elevation and latitude. Fifty-three species representing the morphological variation and distribution of the genus were studied. Total plant height, as well as leaf, inflorescence, petal and sepal length were measured and these data subjected to univariate and multivariate analyses. To test for correlation between plant size and altitudinal and latitudinal distribution, ANOVAs were performed. When the pollination system of a species is known, additional multivariate and univariate analyses were also performed. The results indicate that the characters studied are correlated with a size component, exhibiting positive allometry for sepal and petal length and negative allometry for leaf length. Inflorescence length is an isometric character. There was no significant correlation between plant size and altitudinal or latitudinal distribution. The ANOVAs show that the only character correlated to pollinator type was petal length. Small plants with small flowers are correlated to pollinators such as insects, while medium to large plants with medium to large-sized flowers are correlated with pollinators such as birds and bats. Large plants have small flowers, that are more evident and attract more pollinators.