Characterization of a new species in the genus Didymosphenia and of Cymbella janischii (Bacillariophyta) from Connecticut,USA

Two non-native stalk-forming diatoms that were recently observed in the West Branch of the Farmington River, a tributary of the Connecticut River in Connecticut (USA), are characterized morphologically and barcode marker sequences were obtained for each of them. Cymbella janischii, the dominant stalk-forming species during the summer of 2012, previously had not been found in the northeastern USA. Samples of C. janischii were examined microscopically and used to obtain four sequences of the barcode marker, the V4 region of the 18S rDNA gene. Phylogenetic analysis indicated that the four independent sequences of C. janischii were distinct from, but most closely related to, published sequences of C. janischii from Idaho and C. mexicana from Texas, USA. A second non-native stalk-producing diatom, resembling Didymosphenia geminata, was found in November 2012 – June 2013 and first reported as Didymosphenia sp. Over this period, the observed cells had a compressed morphology and were consistently small compared with D. geminata. Sequences of the V4 region, obtained from three independent direct polymerase chain reactions (PCR) of single cells isolated from the Connecticut samples, indicated a close relationship to three published sequences of D. geminata from Italy, New Zealand and the USA, and to D. siberica and D. dentata from Russia. Frustules of the cells used in the PCR reactions were recovered and examined using scanning electron microscopy, providing a direct link between the observed morphology and sequence data. The morphology of the novel Connecticut Didymosphenia taxon was compared with that of other Didymosphenia taxa, being most similar to D. pumila, D. laticollis, D. grunowii and smaller cells of D. geminata. Didymosphenia sp. had a triundulate morphology with a consistent length of 40–60 µm. Given the unique morphological features of this diatom, it is proposed as a new species, Didymosphenia hullii Khan-Bureau, sp. nov.     

Didymosphenia geminata (Lyngbye) M. Schmidt (Bacillariophyta) in the Danube basin: New data from the Drava river (northern Italy)

Abstract

The presence of Didymosphenia geminata (Lyngbye) M. Schmidt (Bacillariophyta) was revealed in the Drava river and in its affluent Rio Sesto, both flowing in the Alto Adige/Südtirol region of Italy and belonging to the Danube basin. New data are given on the distribution of the species in the Danube basin.     

A polyphasic approach to the delimitation of diatom species: a case study for the genus Pinnularia (Bacillariophyta)

Diatoms are one of the most abundant and arguably the most species‐rich group of protists. Diatom species delimitation has often been based exclusively on the recognition of morphological discontinuities without investigation of other lines of evidence. Even though DNA sequences and reproductive experiments have revealed several examples of (pseudo)cryptic diversity, our understanding of diatom species boundaries and diversity remains limited. The cosmopolitan pennate raphid diatom genus Pinnularia represents one of the most taxon‐rich diatom genera. In this study, we focused on the delimitation of species in one of the major clades of the genus, the Pinnularia subgibba group, based on 105 strains from a worldwide origin. We compared genetic distances between the sequences of seven molecular markers and selected the most variable pair, the mitochondrial cox1 and nuclear encoded LSU rDNA, to formulate a primary hypothesis on the species limits using three single‐locus automated species delimitation methods. We compared the DNA‐based primary hypotheses with morphology and with other available lines of evidence. The results indicate that our data set comprised 15 species of the P. subgibba group. The vast majority of these taxa have an uncertain taxonomic identity, suggesting that several may be unknown to science and/or members of (pseudo)cryptic species complexes within the P. subgibba group.     

Haslea karadagensis (Bacillariophyta): a second blue diatom,recorded from the Black Sea and producing a novel blue pigment

A new species of raphid pennate diatom producing a blue pigment, Haslea karadagensis Davidovich, Gastineau & Mouget, sp. nov., was recently isolated from the Crimean coast of the Black Sea (Ukraine). This organism is very similar to the well-known Haslea ostrearia, the first described ‘blue’ diatom, which produces marennine, the pigment involved in the greening of oysters. The Ukrainian diatom, H. karadagensis, differs slightly from H. ostrearia in the structure of its frustule, and the two organisms are unable to interbreed. Two molecular markers, rbcL and the ITS1–5.8S–ITS2 sequences, showed 2% and >50% differences, respectively, between the two species. UV-visible spectrophotometry and in vivo confocal micro-Raman spectroscopy were used to compare the pigment of H. karadagensis with marennine. Both pigments showed absorption bands in the UV and red regions, but the positions of the maxima differ between the pigments. Significant differences were observed by micro-Raman spectroscopy in the 1000–1700?cm^?1 wavenumber range, revealing that the pigments are different molecules. Haslea karadagensis is the first example of a new ‘blue’ diatom and produces a novel blue pigment.     

Afrocymbella barkeri sp. nov. (Bacillariophyta), a common phytoplankton component of Lake Challa,a deep crater lake in East Africa

A new freshwater diatom, Afrocymbella barkeri Cocquyt & Ryken sp. nov., is described from Lake Challa, a deep and unproductive crater lake near Mt Kilimanjaro in equatorial East Africa, based on light and electron microscopic observations. This tropical diatom is a representative of the rather small genus Afrocymbella with only 12 known species and with a distribution restricted to the African Rift. Taxa belonging to this genus are heteropolar and characterized by dorsiventral valves curved along the pervalvar axis and the presence of small pseudosepta and septa on the open girdle bands. Afrocymbella barkeri was common only towards the end of the dry and windy season corresponding to northern hemisphere summer, when deep water-column mixing caused upwelling of nutrient-rich water from the hypolimnion. This taxon was observed free living in the water column during mixing, but the presence of a small apical pore field at the foot pole, along with some cells with mucilage stalks, suggests that its primary habitat probably involves attachment to a substrate.     

A comparison of phytoplankton assemblages in the Chesapeake and Delaware estuaries (USA), with emphasis on diatoms

The Delaware Bay is characterized as having greater nutrient and turbidity levels than the Chesapeake Bay. In reference to these differences, a one year study was conducted to identify any similarities and differences in the phytoplankton populations in these estuaries. The results indicated patterns of similarity in the diatom composition, with the total phytoplankton assemblage forming two site groups along a salinity gradient in each bay. These site groups were associated with stations located in the tidal fresh-oligohaline and meso-polyhaline regions of both estuaries. The seasonal concentrations of diatoms and total phytoplankton in both of these regions were higher in the Chesapeake Bay.Subtle differences between the two estuaries include a more diversified and abundant assemblage of neritic phytoplankters (including dinoflagellates) are present in the lower Chesapeake Bay. In contrast, a diatom dominated community is more characteristic of Delaware Bay. It is suggested the entry of neritic species into lower regions of the estuaries was enhanced by the reduced amount of rainfall and flow rates that occurred during the study period. The greater success of neritic species in the Chesapeake Bay is attributed to the lower turbidity of that estuary compared to Delaware Bay.     

Nobloedischia rasnitsyni, a new genus and species of Oedischiidae (Orthoptera) from the Lower Permian Wellington Formation of Oklahoma, USA

Nobloedischia rasnitsynigen. et sp. n. (Oedischiidae) is described from the Lower Permian Wellington Formation of Noble County, Oklahoma. The genus is similar to both Petrelcana (Oedischiidae: Mezenoedischiinae) and Oedischia (Oedischiidae: Oedischiinae) and is left unplaced at the subfamily level. The new species is the twelfth Orthoptera species and the fourth species of Oedischiidae from these deposits.     

Molecular phylogeny of the diatom genera Amphora and Halamphora (Bacillariophyta) with a focus on morphological and ecological evolution

The taxonomic history of the diatom genus Amphora is one of a broad early morphological concept resulting in the inclusion of a diversity of taxa, followed by an extended period of revision and refinement. The introduction of molecular systematics has increased the pace of revision and has largely resolved the relationships between the major lineages, indicating homoplasy in the evolution of amphoroid symmetry. Within the two largest monophyletic lineages, the genus Halamphora and the now taxonomically refined genus Amphora, the intrageneric morphological and ecological relationships have yet to be explored within a phylogenetic framework. Critical among this is whether the range of morphological features exhibited within these diverse genera are reflective of evolutionary groupings or, as with many previously studied amphoroid features, are nonhomologous when examined phylogenetically. Presented here is a four‐marker molecular phylogeny that includes 31 taxa from the genus Amphora and 77 taxa from the genus Halamphora collected from fresh, brackish, and salt waters from coastal and inland habitats of the United States and Japan. These phylogenies illustrate complex patterns in the evolution of frustule morphology and ecology within the genera and the implications of this on the taxonomy, classification, and organization of the genera are discussed.     

Distribution of diatom surface sediment assemblages within Effingham Inlet, a temperate fjord on the west coast of Vancouver Island (Canada)

Twenty-nine surface sediment samples from Effingham Inlet, a small fjord on the west coast of Vancouver Island, British Columbia, were analyzed for diatoms. This fjord has been selected for paleoceanographic investigation due to the presence of laminated sediments resulting from the dysoxic to anoxic bottom water conditions in the inner and outer basins of the inlet. Distributional patterns of the diatom microflora reflected proximity to littoral regions, phytoplankton production, and marine influence from outside the fjord. Principal components and cluster analyses of the microflora established four diatom assemblages with a clear separation between the inner and outer basin diatom floras. Inner basin stations were characterized by elevated absolute abundance with assemblages dominated by spring–early summer bloom taxa including Skeletonema costatum, Thalassiosira nordenskioeldii, and Thalassiosira pacifica. Chaetoceros spp. resting spores were abundant throughout Effingham Inlet, with the exception of the stations closest to the fjord head. Stations located in the outer basin and towards the fjord mouth had relatively lower absolute abundance yet showed a higher relative and absolute abundance of Thalassionema nitzschioides, Rhizosolenia setigera, Coscinodiscus radiatus, Ditylum brightwellii, Odontella longicruris, and Paralia sulcata in relation to the inner basin. Many of these latter taxa are often associated with late summer and autumn conditions in fjords along coastal British Columbia. Oceanographic data for Effingham Inlet suggest that increased offshore penetration is more likely to occur from summer to early fall, with a more restricted offshore influence in the inner basin. Diatom surface sediment assemblages in Effingham Inlet appear to reflect incursions of offshore waters into the fjord. Absolute abundance estimates and the preservation of lightly silicified taxa suggest excellent preservation of fossil material in the sediments of the predominantly anoxic inner basin. Preservation in the outer basin is reduced, reflecting more frequent recharge by oxygenated waters spilling over the outer sill into the basin. Our findings suggest the inner basin should be an optimal site for reconstruction of diatom production, with records from the outer basin providing more consistent information about offshore influence and coastal upwelling conditions over the Holocene. Estimates of diatom abundance within the inner basin sediment may serve as a good proxy of production, although proxy tracers of bottom water conditions and sedimentological analyses must be coupled to the diatom record to ensure depositional conditions were not influencing valve preservation or abundance. Our results suggest that fjords can serve as good environments for paleoceanographic reconstructions of both inshore and offshore conditions although careful site selection and understanding of processes affecting the microfossil record are essential.     

The reproductive cycle in the population of Saccostrea cuccullatta (Born) from the coast of Karachi,Pakistan

Periphytic diatom communities on clay tile and sterilized rock substrates were compared with those on natural substrates. Clay tiles yielded diatom communities with the least variability between replicate samples, and the greatest similarity to the natural substrate assemblage. The advantages of utilizing introduced substrate communities and problems encountered with their simulation of the natural substrate community are discussed.     

Description of Conticribra tricircularis,a new genus and species of Thalassiosirales,with a discussion on its relationship to other continuous cribra species of Thalassiosira Cleve (Bacillariophyta) and its freshwater origin

A new diatom genus Conticribra is erected to accommodate C. tricircularis, described from a freshwater Pliocene deposit in Trout Creek, Oregon (USA). The genus accommodates species possessing: (i) loculate areolae with (semi-) continuous cribra; (ii) non-plicated valve face; (iii) rimoportula located on the valve mantle, replacing a fultoportula. Conticribra tricircularis has no valve face fultoportulae and can easily be distinguished by its marginal fultoportulae with four satellite pores arranged in three rings. Three species are transferred to the new genus from Thalassiosira sensu lato. Using evidence from the fossil record and recent molecular data, a hypothesis concerning the freshwater origin of Conticribra is discussed.     

Characterization of polymorphic microsatellite loci in the marine isopod Sphaeroma terebrans (Crustacea, Isopoda)

Nine polymorphic microsatellites were characterized in the marine isopod Sphaeroma terebrans (Isopoda, Sphaeromatidae) for phylogeographic and parentage analyses. The number of alleles ranged from 3 to 10. Observed heterozygosity ranged from 0.428 to 0.950, while expected heterozygosity ranged from 0.532 to 0.889. Heterozygote deficiency was detected for one locus, possibly the result of null alleles.     

In situ detection of novel Acidobacteria in microbial mats from a chemolithoautotrophically based cave ecosystem (Lower Kane Cave, WY, USA)

Lower Kane Cave, Wyoming (USA), has hydrogen sulfide-bearing springs that discharge into the cave passage. The springs and cave stream harbour white filamentous microbial mats dominated by Epsilonproteobacteria. Recently, novel 16S rRNA gene sequences from the phylum Acidobacteria, subgroup 7, were found in these cave mats. Although Acidobacteria are ubiquitously distributed in many terrestrial and marine habitats, little is known about their ecophysiology. To investigate this group in Lower Kane Cave in more detail, a full-cycle rRNA approach was applied based on 16S and 23S rRNA gene clone libraries and the application of novel probes for fluorescence in situ hybridization. The 16S and 23S rRNA gene clone libraries yielded seven and six novel acidobacterial operational taxonomic units (OTUs) respectively. The majority of the OTUs were affiliated with subgroups 7 and 8. One OTU was affiliated with subgroup 6, and one OTU could not be assigned to any of the present acidobacterial subgroups. Fluorescence in situ hybridization distinguished two morphologically distinct, rod-shaped cells of the acidobacterial subgroups 7 and 8. Although the ecophysiology of Acidobacteria from Lower Kane Cave will not be fully resolved until cultures are obtained, acidobacterial cells were always associated with the potentially chemolithoautotrophic epsilon- or gammaproteobacterial filaments, suggesting perhaps a lifestyle based on heterotrophy or chemoorganotrophy.     

Diatom Communities and Water Quality Assessment in Mountain Rivers of the Upper Segre Basin (La Cerdanya,Oriental Pyrenees)

Epilithic diatoms of mountain rivers from the upper Segre catchment (Oriental Pyrenees) were studied in 1998, during three different seasons: March, July and September. Four rivers, the river Segre and its three most important tributaries, Duran, Molina and Querol, were sampled in upstream and downstream stretches. The diatom communities were comparable in all upstream stretches of these mountain rivers draining siliceous substrates. Dominant taxa were Achnanthidium subatomus, Diatoma mesodon, Encyonema cf. minutum, E. silesiacum, Fragilaria arcus, F. capucina, Gomphonema calcifugum, G. pumilum, Meridion circulare and Nitzschia pura. Changes in water quality in the downstream stretches lead to the appearance of pollution tolerant taxa, such as Eolimna minima, Gomphoneis minuta, Navicula gregaria, and Nitzschia inconspicua. As a result, the values obtained with the diatom water quality indices (IPS Specific Polluosensitivity Index, CEE and IBD Biological Diatom Index) decreased. The diatom community composition and the derived water quality values did not change in the upstream stretches over the year. In contrast, significant changes were observed in the downstream stretches with best water␣quality in July, during high flows due to melting snow, and worst values in September, during low␣discharge. The diatom indices, especially the IPS, showed a good performance in these mountain rivers.     

Occurrence of Phyllodistomum folium (Olfers) (Digenea) in the eel, Anguilla anguilla (Linnaeus), in a small river

The occurrence of Phyllodistomum folium in a population of eels was studied throughout one year. Abundance exhibited a summer peak. Gravid adults were found in all months, indicating that eels can serve as a definitive host for this parasite.