Sexual reproduction and auxospore development in the diatom Biddulphia biddulphiana.

Phylogenetic relationships among mediophycean diatoms with elliptical valve outline and elevated apices have long been a subject of interest and debate, particularly with respect to their relationship to pennates. However, results remain inconclusive, whether based on vegetative valve morphology, reproduction, or molecular phylogenetic data. Searching for phylogenetically informative features, we re-examined sexual reproduction, auxospore structure and development in the diatom Biddulphia biddulphiana.

, A Novel Cosmopolitan Species of Blue Diatoms.

Specimens of a new species of blue diatoms from the genus Simonsen were discovered in geographically distant sampling sites, first in the Canary Archipelago, then North Carolina, Gulf of Naples, the Croatian South Adriatic Sea, and Turkish coast of the Eastern Mediterranean Sea. An exhaustive characterization of these specimens, using a combined morphological and genomic approach led to the conclusion that they belong to a single new to science cosmopolitan species, sp. nov.

A consensus secondary structure of ITS2 for the diatom Order Cymatosirales (Mediophyceae, Bacillariophyta) and reappraisal of the order based on DNA, morphology, and reproduction.

In 1983, Hasle and colleagues removed cymatosiroid diatoms from the pennates, and erected a new centric diatom family, the Cymatosiraceae, mainly to accommodate for their newly discovered mode of sexual reproduction. The new family consisted of two subfamilies differing in frustule structure. The family was later elevated to the rank of Order Cymatosirales Round and Crawford.

Structure and Development of the Auxospore in Ardissonea crystallina (C. Agardh) Grunow Demonstrates Another Way for a Centric to Look Like a Pennate.

Reproductive development in Ardissonea crystallina revealed a unique mode of enlargement involving a combination of novel and known structures. In light microscopy, auxospores of this elongated polar centric diatom were superficially similar to the auxospores of pennates. With SEM we found three different components in the auxospore wall.

Ardissonea crystallina has a type of sexual reproduction that is unusual for centric diatoms.

Molecular phylogenetic analyses place Ardissonea crystallina (C. Agardh) Grunow and all Toxariids among the bi- and multipolar centric diatoms, almost always recovered as a derived lineage sister to Lampriscus. In all centrics where sexual reproduction has been documented, oogamy, with larger immobile eggs and smaller flagellated sperm has been observed.

Gametogenesis and Auxospore Development in the Bipolar Centric Diatom Brockmanniella brockmannii (Family Cymatosiraceae).

We examined gametogenesis and auxospore development in the cymatosiroid diatom Brockmanniella brockmannii. Our mating experiments demonstrated that the clones were homothallic, self-compatible, produced two eggs per oogonium and four hologenous uniflagellate male gametes per spermatogonium. Auxospores grew free in the culture medium and the most external layer of the auxospore wall was made up of spinescent scaly elements in their early globular stage of development.

Sexual reproduction in plagiogrammacean diatoms: First insights into the early pennates.

The genera Plagiogramma and Dimeregramma are members of a small, but evolutionarily important group of diatoms, the "basal" araphids. They are sister to all other pennates, both araphid and raphid taxa. Thus, their phylogenetic position carries the potential for providing insights into the earliest pennates.

Auxosporulation in Paralia guyana MacGillivary (Bacillariophyta) and Possible New Insights into the Habit of the Earliest Diatoms.

Background: Diatoms are one of the most ecologically important aquatic micro-eukaryotes. As a group unambiguously recognized as diatoms, they seem to have appeared relatively recently with a limited record of putative remains from oldest sediments. In contrast, molecular clock estimates for the earliest possible emergence of diatoms suggest a considerably older date.

Paralia (Bacillariophyta) stowaways in ship ballast: implications for biogeography and diversity of the genus.

Background: The genus Paralia Heiberg is one of the most recognizable, widely distributed and commonly reported diatoms from contemporary coastal marine environments and ship ballast. Species discovery has historically been made in diatoms through the recognition of morphological discontinuities between specimens, first using light and later electron microscopy. However, recently, morphologically semi-cryptic species of Paralia were delineated using genetic analyses, among mostly tropical and subtropical sites.

Motile male gametes of the araphid diatom Tabularia fasciculata search randomly for mates.

Sexuality in the marine araphid diatom Tabularia involves an unusual type of gamete, not only among diatoms but possibly in all of nature. The non-flagellated male gamete is free and vigorously motile, propelled by pseudopodia. However, the cues (if any) in their search for compatible female gametes and the general search patterns to locate them are unknown.

Cryptic diversity in a cosmopolitan diatom known as Asterionellopsis glacialis (Fragilariaceae): Implications for ecology, biogeography, and taxonomy.

Premise Of The Study: Diatoms have long been known as the most species-rich of algal groups, with a wide range of estimates for species number (20-200 k) due to differing species concepts. The fine valve structure in Asterionellopsis glacialis, a diatom believed cosmopolitan and eurytopic, has never been systematically examined using modern microscopy and is an excellent candidate to genetically test morphology-based conspecificity among its geographically distant culture isolates.

Methods: Isolates from the Atlantic and Pacific Oceans that were morphologically delineated as A.

Silicification of auxospores in the araphid diatom Tabularia fasciculata (Bacillariophyta).

We report on auxospore wall structure and development in the araphid pennate diatom Tabularia fasciculata. Similar to most other pennates, these auxospores showed a typical bidirectional elongation, but unexpectedly bore no transverse perizonium, and with no detectable silicon during much of their expansion. Energy dispersive X-ray spectroscopy (EDS) analyses segregated auxospores into two types: (1) those containing no detectable silicon and (2) those with measureable amounts.

Inheritance of mitochondrial DNA in the Pennate diatom Haslea ostrearia (Naviculaceae) during auxosporulation suggests a uniparental transmission.

We present the first study examining mtDNA transmission in diatoms, using sexual progeny of the pennate species Haslea ostrearia (Naviculaceae). A fragment of the cytochrome oxidase subunit I gene (cox1) with 7 nucleic substitutions between parental clones was used as a parental tracer in 16 F1 clones obtained from two pairs of mating crosses. Each cross involved a parental clone isolated from France (Bay of Bourgneuf) and Sweden (Kattegat Bay).

Distance and character-based evaluation of the V4 region of the 18S rRNA gene for the identification of diatoms (Bacillariophyceae).

DNA barcoding is a molecular tool that exploits a unique DNA sequence of a standardized gene or non-coding region for the species identification of unknown individuals. The investigation into a suitable barcode for diatoms is ongoing and there are several promising candidates including mitochondrial, plastidial and nuclear markers. We analyzed 272 sequences from 76 diatoms species in the orders Thalassiosirales, Lithodesmiales and Cymatosirales, using distance and character based approaches, to assess the applicability of a DNA barcode based on the hypervariable V4 region of the nuclear 18S rRNA gene.

Relationship between propagule pressure and colonization pressure in invasion ecology: a test with ships' ballast.

Increasing empirical evidence indicates the number of released individuals (i.e. propagule pressure) and number of released species (i.

Mechanism of male gamete motility in araphid pennate diatoms from the genus Tabularia (Bacillariophyta).

During sexual reproduction, araphid pennate diatoms of the genus Tabularia (Kützing) D. M. Williams and Round released male gametes directly into the medium, sometimes at a considerable distance from the female gametes.

Survey of the efficacy of a short fragment of the rbcL gene as a supplemental DNA barcode for diatoms.

DNA barcoding is a tool that uses a short, standard segment of DNA to identify organisms. In diatoms, a consensus on an appropriate DNA barcode has not been reached, but several markers show promise. These include the 5.

Barcoding of diatoms: nuclear encoded ITS revisited.

DNA-barcoding is based on the premise that the divergence of a small DNA fragment coincides with biological separation of species. If true, it offers an additional tool for worldwide consistent species recognition even in cases of semi-cryptic species. Our study includes 618 sequences representing 114 diatom species belonging to the two most species-rich classes of diatoms (Mediophyceae and Bacillariophyceae).

Barcoding diatoms: Is there a good marker?

The promise of DNA barcoding is based on a small DNA fragment divergence coinciding with biological species separation. Here we evaluated the performance of three markers as diatom barcodes, the small ribosomal subunit (1600 bp), a 5' end fragment of cytochrome c oxidase subunit 1 (430 bp), and the second internal transcribed spacer region combined with the 5.8S gene (5.