The biology of Dendropoma corallinaceum and Serpulorbis natalensis, two South African vermetid gastropods

D. corallinacewn forms sheet-like colonies at Mean Low Water (MLW) on exposed rocky shores: S. natalensis forms loose aggregations under stones below MLW in more sheltered situations. Both species released young from July— December. D. corallinaceun has single embryos in capsules brooded free in the mantle cavity; S. natalensis has 20–40 embryos per capsule, the latter being attached to the roof of the shell and hanging through a dorsal slit in the mantle. The morphology of the crawling young is similar in both species, resembling adult errant prosobranchs. D. corallinaceum has a stouter, more streamlined protoconch than S. natalensis correlated with the more turbulent water of its habitat. The crawling young secrete a sticky mucous trail for adhesion to the substratum. They are strongly photopositive until settlement. D. corallinaceum can settle within 24 hours but may delay settlement to 4–5 days if suitable substrata are absent. Metamorphosis is complete 2 days after settlement. D. corallinaceum prefer to settle on Lithothamnion which is easily eroded by the radula to provide a groove for rapid, firm attachments to the substratum. Both species feed from mucous nets, S. natalensis having a slower feeding rhythm commensurate with its larger size. Contiguous pairs of S. natalensis have synchronised feeding rhythms, probably to reduce mutual net robbing. Particles are also filtered out of suspension; many particles are rejected in the pseudofaeces but some are ingested. D. corallinaceum and S. natalensis have many similar ecologically equivalent species throughout the warm temperate and tropical seas of the world.     

Larger foraminifera as a substratum for encrusting bryozoans (Late Oligocene,Tethyan Seaway,Iran)

Considering the diversity and abundance of larger foraminifera examined from a wide range of Late Oligocene to Early Miocene palaeoenvironments in the Tethyan Seaway, encrusting bryozoans make extremely little use of their tests as substratum. Significant encrustations by bryozoans were exclusively found on large (ø c. 6 cm), undulating tests of Lepidocyclina spp., on which, however, a remarkable 34 taxa of encrusting bryozoans were recorded. This shallow-water fauna of Chattian age was analyzed in respect of the bryozoan taxa present, colony growth type, and mode of budding, colony size, as well as onset of reproduction. Taxic and morphological similarities between the fossil assemblage and modern faunas encrusting mobile substrata indicate a long history of bryozoans as part of the interstitial habitat, while the tests of certain larger foraminifera may have played a significant role in the evolution of shallow-water bryozoans by providing substrata for encrusting species in otherwise unfavorable environments.     

Divergence and species discrimination in freshwater bryozoans (Bryozoa: Phylactolaemata)

We explored the suitability of nuclear and mitochondrial ribosomal markers [small subunit nuclear ribosomal RNA gene, large subunit nuclear ribosomal RNA gene, and a region spanning partial small mitochondrial ribosomal RNA subunit, four transfer RNA genes, and partial large mitochondrial ribosomal RNA subunit (referred to as rrnS‐rrnL)] for resolving patterns of diversification of 27 freshwater bryozoan species (class: Phylactolaemata) and evaluated the utility of statoblast ultrastructural features and molecular phylogenies for species discrimination in the Fredericellidae and Plumatellidae. Molecular data identified Plumatella fruticosa as distinct from the rest of the plumatellids, rendering the latter polyphyletic. rrnS‐rrnL was the most suitable marker for species discrimination and identified two undescribed species of Plumatella and at least two undescribed species of Fredericella. Lack of wide dispersal by fredericellid statoblasts may underlie the observed propensity for cryptic speciation and phylogeographical structure in Fredericella. Conversely, the strong dispersal potential of plumatellid statoblasts may mediate efficient gene flow between distant populations and explain the relatively low intraspecific divergence and lack of evidence for cryptic speciation. We show that species identification based on external features of statoblasts can be problematic in both genera, including for a putatively highly invasive, biofouling species, Plumatella vaihiriae, thereby highlighting the utility of rrnS‐rrnL sequences for species barcoding. © 2013 The Linnean Society of London     

Species- and site-specific bacterial communities associated with four encrusting bryozoans from the North Sea, Germany

Epi- and endozoic bacterial communities associated with four bryozoan species from the Jade (North Sea, Germany) were investigated by the combined application of molecular tools and electron microscopic visualisation of zooids. Denaturing gradient gel electrophoresis of PCR-amplified 16S rRNA gene fragments of associated bacteria displayed specific bacterial community profiles in the examined species Aspidelectra melolontha, Conopeum reticulum, Electra monostachys and Electra pilosa. Actual bacterial epibiosis was only observed on C. reticulum whilst the other bryozoans under investigation were largely free of microbial epibionts. These observations indicated that bryozoan-associated bacteria identified by molecular methods originated from internal cavities of bryozoan zooids. Cluster analysis of DGGE band patterns revealed species-specific bacterial communities in A. melolontha, E. monostachys and E. pilosa. Bacteria associated with C. reticulum were seemingly influenced by site-specific parameters. A comparison of bacterial community profiles between reference and invertebrate surfaces allowed for an interpretation of conspicuous group-specific differences. Operational taxonomic units (OTUs) obtained from a single set of bryozoan replicates that were absent on the inorganic reference samples (mussel shells) were hypothesized to be favourable endobionts. Contrary, OTUs present in the references but absent in bryozoan samples could be assumed to stem from bryozoan-specific defenses against ubiquitous bacterial colonizers. Although there was no experimental evidence for a mutual relationship between prokaryotes and their eukaryotic bryozoan hosts, this study demonstrated that in three out of four bryozoans under investigation associated bacterial communities were characteristically shaped by host attributes.     

New species of stenolaemate bryozoans from the Jurassic of the Moscow and Saratov Regions (Russia)

Three new species of the Middle Jurassic stenolaemate bryozoans of the genera Reptomultisparsa d’Orbigny and Microeciella Taylor et Sequeiros are described: R. saratovensis sp. nov. and M. seltseri sp. nov. from the Lower Bathonian and the Upper Callovian of the Saratov Region, respectively, and R. stupachenkoi sp. nov. from the Middle Callovian of the Moscow Region. Some specific features of their astogeny and colonial morphology are discussed.     

Competition within and between encrusting clonal invertebrates

Colonies of encrusting marine invertebrates are tractable models for the study of competition, because of the relative ease with which observations can be made on the frequency and outcome of overgrowth interactions. Studies of intraspecific competition have found that competition is predicated upon a genetically controlled recognition event, which results in either fusion or rejection. Data are rapidly accumulating in two model systems showing that fusion is associated with somatic cell parasitism and that rejection is associated with overgrowth. Thus, encounters between conspecifics define a choice: to compete at the level of the cell lineage or to compete at the level of the colony. Fusion-rejection genes act to control the units (or targets) of selection.     

Horizon of the oldest known bryozoans (Ordovician)

Among the six species of fossil bryozoans described by Xia et al. [Xia, F.S., Zhang, S.G., Wang, Z.Z., 2007. The oldest bryozoans: new evidence from the late Tremadocian (Early Ordovician) of East Yangtze Gorges. Journal of Paleontology 81 (6), 1308–1326] from the Fenghsiang Formation of the Chenjiahe section of Yichang and the Guanzhuangping section, Liujiachang Town of Songzi, the Yangtze Gorges, Nekhorosheviella nodulifera occurs in the pristinus Conodont Subzone (lower Subzone of deltifer Conodont Zone) and the five other species are associated with the conodont Paltodus deltifer deltifer and the graptolites Acanthograptus sinensis and A. erectoramus. Based on the conodonts and graptolites, this bryofauna stratigraphically corresponds to the A. sinensis Graptolite Zone or P. deltifer Conodont Zone. The bryofauna is of Tremadocian Age (Early Ordovician) and represents the oldest bryozoans so far as known.     

Freshwater bryozoans (Bryozoa) of Norway II: distribution and ecology of two species of Fredericella

Freshwater bryozoans were investigated during field studies of 601 lakes and other surface water bodies throughout Norway from 1960 to 1978. The frequency of occurrence of the two Fredericella species was evaluated in relation to 12 environmental variables. Statistically significant deviations from the frequencies expected on the basis of random distribution were described using the categories preference, avoidance and absence. The typical European Fredericella sultana (with glossy statoblasts) occurred at 72 localities, north to 70° 25 N (the northernmost record on a global scale). Its frequency dropped towards the north. Maximum elevation above sea level was 1097 m (maximum recorded for Northern Europe). Another species with pitted statoblasts, tentatively considered to be Fredericella indica, occurred at 50 localities, north to 71° 09 N (the northernmost record reported to date). The geographical distribution reflected a typical northern cold-water species. One third of the 50 records were from lakes situated north of the Arctic Circle, and rich colonies were found on the North Cape plateau, as far north as possible on the European mainland. The few records from southeastern Norway were from high mountain lakes, up to 1397 m above sea level (highest record for Europe). This species was not found in any of the numerous lowland lakes investigated in southeastern Norway where F. sultana was common. Both species tolerated a cold climate, especially Fredericella indica, and they occurred in a wide range of environments. F. sultana preferred lakes with rather low elevation above sea level, rich vegetation with plant species typical for eutrophic environments, gyttja sediments and stony "hard" shores, some wave action, high content of calcium, and slightly coloured water. This species avoided ponds and was absent from ditches and mires, avoided dystrophic lakes surrounded by Sphagnum bog, with dy sediments and strongly coloured water, avoided sites with small wave action, was indifferent to magnesium and low concentrations of calcium, and was absent from lakes with pH below 5.4. F. indica was only recorded from lakes. It preferred rather low temperatures, oligotrophic conditions with poor aquatic vegetation and stony shores, some wave action, pH above 7.0, and low water colour (below 11 mg Pt l^–1). This species avoided lakes with high temperatures and was absent above 20 °C, was absent where aquatic vegetation was rich or consisted of Sphagnum bog, avoided lakes with soft sediments of dygyttja and dy, places with small wave action, acid lakes, was absent at pH below 5.9, tended to avoid water with colour above 10 mg Pt l^–1 and was absent in lakes with colour above 40 mg Pt l^–1. F. sultana and F. indica occurred together in only six lakes, four in the north, and two in the southern mountain areas. The opposite sensitivity and reactions of the two species towards several environmental variables were supported by a logistic regression analysis. The main ecological difference between the two species is that F. indica appears to be more strongly dependent on climatic factors.     

Megasporogenesis and megagametogenesis in several Tripsacum species (Poaceae)

The Tripsacum agamic complex (x = 18) will provide valuable characters for maize breeding, provided that apomixis can be manipulated. Apomixis in Tripsacum was first reported 40 years ago, but its prevalence in the genus has not been established. Reproductive development was determined for eight Mexican and two South American Tripsacum species by microscopic analysis of ovaries cleared in a benzyl benzoate-dibutyl phthalate solution using interference contrast optics. The occurrence and distribution of callose deposition during megasporogenesis were determined by fluorescence microscopy of ovaries optically cleared in an aqueous sucrose solution containing aniline blue. Diploid genotypes were sexual. Polyploid forms reproduced apomictically following the Antennaria type (complete meiosis abortion) of diplospory. The Taraxacum type (unreduced megaspore production through meiotic restitution nuclei) of diplospory also occurred but rarely. The walls of diplosporic megasporocytes lacked callose whereas the walls of sexual megasporocytes contained a normal complement of callose. The absence of callose suggests that the diplosporic forms of reproduction result from mutations affecting the normal meiotic process. Apomixis in the Tripsacum genus is facultative, and the production of new polyploid genotypes through genetic exchanges involving both apomictic and sexual genotypes is possible.     

Interactions between Fusarium species from sugarcane and the stalk borer, Eldana saccharina (Lepidoptera: Pyralidae)

In this study, beneficial relationships between Fusarium species in sugarcane and the stalk borer, Eldana saccharina (Lepidoptera: Pyralidae) were demonstrated in vitro . In addition, Fusarium species with antagonistic properties were found to inhabit sugarcane. Attenuated Fusarium isolates from sugarcane stalks collected across the South African sugar industry were incorporated into diet formulated to mass rear E. saccharina . Of the over 200 Fusarium isolates obtained, 10 that significantly improved the survival and development of E. saccharina larvae and considered to be beneficial were selected for further study, as were 10 that were detrimental or antagonistic to the stalk borer. Twelve of the selected isolates were identified as F. sacchari by direct sequencing of translation elongation factor-1α fragments, eight of which resulted in reduced numbers of surviving larvae and significantly lower larval masses. F. proliferatum isolates resulted in increased survival and mass of E. saccharina and three of the five isolates assigned to the F. pseudonygamai group enhanced E. saccharina development. Results from olfactory choice experiments suggested the production of attractive and repellent metabolites by certain isolates. Findings from this study may offer additional or alternative strategies for managing E. saccharina infestation of sugarcane.     

Interactions between species and environments from incomplete information

There are two contradictory aspects of the adaptive process in evolution. The first is that species must optimally increase their own fitness in a given environment. The second is that species must maintain their variation to be ready to respond to changing environments. In a strict sense, these two aspects might consider to be mutually exclusive. If species are optimally adapted, then the variation in the species that is suboptimal decreases and vice versa. To resolve this dilemma, species must find a balance between optimal adaptation and robust adaptation. Finding the balance between these processes requires both the local and global complete, static information. However, the balance between the processes must be dynamic. In this study, we propose a model that illustrates dynamic negotiation between the global and local information using lattice theory. The dynamic negotiation between these two levels results in an overestimate of fitness for each species. The overestimation of fitness in our model represents the multiplicity of fitness which is sometimes discussed as the exaptation. We show that species in our model demonstrate the power law of the lifespan distribution and 1/f fluctuation for the adaptive process. Our model allows for a balance between optimal adaptation and robust adaptation without any arbitrary parameters.     

Spermiogenesis in the vermetid gastropod Dendropoma petraeum (Gastropoda,Prosobranchia)

The structure and maturation of the male gonad of the Mediterranean vermetid gastropod Dendropoma petraeum are described. Histological sections of the gonads were made throughout development and gonad activity was monitored at regular monthly intervals. During the autumn months the gonad is very small and is surrounded by a large quantity of connective tissue; it becomes more voluminous from December to August, with the highest growth peak in springtime. The stages of spermatogenesis were also observed and described.     

New bryozoans from the Devonian of Gorny Altai (Russia)

New bryozoans Saffordotaxis altaicus sp. nov. from the Givetian Stage (Middle Devonian) and Cyphotrypa olgae sp. nov. and Crustopora aliena sp. nov. from the Famennian Stage (Upper Devonian) are described from the Devonian of Gorny Altai.     

Freshwater bryozoans (Bryozoa) of Norway V: review and comparative discussion of the distribution and ecology of the 10 species recorded

The paper is based on material presented in five contributions [Hydrobiologia 421:1–24, 2000; 459: 103–123, 2001; 479: 11–22, 2002; 501: 179–198, 2003; Archives de lInstitut grand-ducal de Luxembourg. Section des Sciences naturelles, physiques et mathématiques, Nouvelle Série 44: 127–143, 2002]. Nine species of Bryozoa were collected during field studies of 601 lakes and other surface water types in Norway. Five of the species occur throughout Norway (Plumatella fruticosa, P. repens, Paludicella articulata, Cristatella mucedo and Fredericella sultana) and one has a northerly range (Fredericella indica). With the exception of Plumatella repens, the northernmost records of these species globally are in Norway. All six species have been found at elevations of more than 1000m in South Norway, which is also their maximum elevation above sea level in Northern Europe. Three species (Plumatella fungosa, P. emarginata and P. casmiana) are rare and present only in lowland areas in South Norway. Lacourt [A Monograph of the Freshwater Bryozoa–Phylactolaemata. Zoologische Verhandelingen, Leiden 93: 1–159, 1968] considered an old and now mislaid sample from the same area to be Hyalinella punctata. Up to six species and an average of two were found in lakes. The mean numbers of species in ponds, and slow-flowing and rapid-flowing rivers were 0.6, 0.8 and 1.0, respectively. Co-occurrence of pairs of species in lakes was investigated. For 10pairs, the number of cases of co-occurrence was significantly higher than expected on the basis of random distribution. This was ascribed to some shared ecological requirements. Only one pair (Paludicella articulata–Plumatella fungosa) showed fewer cases of co-occurrence than expected. This was explained by differences in their geographical distribution and tolerance to ecological factors. Tolerance and other ecological responses were described for the six frequent species using two statistical methods. Method 1: frequency deviations, is based on the null hypothesis of random distribution. Ten environmental variables were studied (type of surface water, elevation above sea level, water temperature, aquatic vegetation, sediment, wave action, Ca, Mg, pH and water colour).The concepts absence, avoidance (frequency lower than expected), preference (frequency higher than expected) and presence (no significant deviation from expected frequency) were used. The degree of response of a particular species to a specific environmental variable was measured by the sum of the numerical values of the significant frequency deviations divided by the number of categories with significant deviations. The results can be used as adaptability indices or tolerance indices: the lower the index, the better a species is adapted for surviving with respect to the environmental variable in question. Diagrams showed (1) the relative strength of the response of the six frequent species, (2) the average index for each species for all variables and (3) the effect of each of the 10 environmental variables on the Bryozoa (the species treated as a unit: an ecological guild). Method 2: logistic regression, treated the presence or absence of each of the six frequent species as dependent variables using nine independent environmental variables. Comparison of the results of method 1 and 2, indicated that method 1, which gives details of how a species responds to different categories of a variable, was particularly useful.     

Operculate cyclostome bryozoans (Eleidae) from the Bohemian Cretaceous

Eleidae (‘melicerititids’) are unusual cyclostome bryozoans possessing operculate zooids and mandibulate polymorphs (‘eleozooids’) resembling the avicularia of cheilostome bryozoans. Here we describe 13 eleid species from the Cenomanian-Turonian of the Bohemian Cretaceous basin in the Czech Republic. Three species of Meliceritites are new: Meliceritites kankensis, M. stillativa and M. upohlavyensis. Reptoforicula gen. nov. is introduced for free-walled eleids with multilamellar encrusting colonies, containing the type species Reptoforicula zbyslavensis sp. nov. and R. vodrazkai sp. nov. Type specimens of three species erroneously assigned to Eleidae are refigured and their true affinities discussed. This study underscores the value of eleozooids in distinguishing between otherwise closely similar eleid species. The Bohemian late Cenomanian-early Turonian eleid fauna is dominated by encrusting species, a pattern that is typical of nearshore localities and contrasts with offshore chalks where erect, vincularian species are more numerous.     

Interactions between tetrahydrofolate and palladium(II) complexes

Interactions between folate derivatives and palladium(II) complexes are monitored in 1 : 1 molar ratio mixtures by circular dichroic spectra. The results are consistent with the following conclusions, i.e., tetrahydrofolate forms a chelate complex with palladium(II) through nitrogens 5 and 10 which is characterized by a unique circular dichroic spectrum. Mixtures of pallodium (II) complexes and dihydrofolate on methylenetetrahydrofolate could not be expected to, nor do they, give rise to similar circualr dichroic spectra for the following reasons: (1) The N5, N10 chelation site of tetrahydrofolate is blocked in methylenetetrahydrofolate, so coordination of a palladium(II) species must occur at some secondary site. (2) The N5, N10 chelation site is available but carbon six of the pteridine ring system is no longer asymmetric in dihydrofolate. Mixtures of dihdrofolate and palladium(II) complexes have no measurable circular dichroic spectra under the experimental conditions used.