Matt Ashworth

University of Texas at Austin | UT · Department of Molecular Biosciences

“Surf diatoms” can form high biomass in the surf zone of sandy beaches around the world, Asterionellopsis and Anaulus being the main genera of this group in Brazil. Asterionellopsis glacialis was considered a cosmopolitan species, and taxonomic studies using molecular and morphological tools showed that A. glacialis is a complex with cryptic and se...

Several automated molecular methods have emerged for distinguishing eukaryote species based on DNA sequence data. However, there are knowledge gaps around which of these single-locus methods is more accurate for the identification of microalgal species, such as the highly diverse and ecologically relevant diatoms. We applied genetic divergence, Aut...

The diatom genus Biddulphia Gray has hosted a tremendous amount of morphological diversity throughout its taxonomic history. SEM-assisted studies have significantly helped to sort this diversity into a classification based on specific valve characters, particularly the structure of pore fields on the valve apices, rather than gross morphology such...

Ardissonea was resurrected from Synedra in 1986 and was included as a genus by Round, Crawford and Mann (“The Diatoms”) in its own Family and Order. They commented that there might be several genera involved since the type species of the genus possesses a double-walled structure and other taxa placed in Ardissonea have only a single-walled structur...

Our understanding of the importance of microbiomes on large aquatic animals—such as whales, sea turtles and manatees—has advanced considerably in recent years. The latest observations indicate that epibiotic diatom communities constitute diverse, polyphyletic, and compositionally stable assemblages that include both putatively obligate epizoic and...

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. Search...

The current article focuses on the morphological and molecular characterization of the often inconspicuous genus Amicula. This recently erected genus from brackish and marine sediments was monotypic but here we describe two new tropical species: Amicula micronesica sp. nov. and Amicula vermiculata sp. nov. Once considered an incertae sedis genus re...

Pleurosira laevis is a salt tolerant diatom distributed around the world. The valve of P. laevis has distinct structures called ocelli, which are sharply‐defined areas with fine, densely‐packed pores. Two formae of this diatom, P. laevis f. laevis and P. laevis f. polymorpha, are distinguished from each other by their flat or dome‐shaped valve face...

Background: Our understanding of the importance of microbiomes on large aquatic animals—such as whales, sea turtles and manatees—has advanced considerably in recent years. Recent activity describing the epizoic diatoms growing on marine vertebrates suggests that these epibiotic diatom communities constitute diverse, polyphyletic, and compositionall...

Our understanding of the importance of microbiomes on large aquatic animals—such as whales, sea turtles and manatees—has advanced considerably in recent years. Recent activity describing epizoic diatoms suggests that epibiotic diatom communities constitute diverse, polyphyletic, and compositionally stable assemblages that include both putatively ob...

We provide for the first time the complete plastid and mitochondrial genomes of a monoraphid diatom: Schizostauron trachyderma. The mitogenome is 41,957 bp in size and displays two group II introns in the cox1 gene. The 187,029 bp plastid genome features the typical quadripartite architecture of diatom genomes. It contains a group II intron in the...

Corethron is the only diatom genus currently known to possess valves with articulated spines and sockets. In molecular phylogenetic trees extant Corethron is in a clade with no close living relatives and sister to almost all other diatoms. Yet Corethron sensu stricto first appeared in the early Oligocene. So where did it come from? To answer this q...

Natural microbial communities are extremely complex, with many more species coexisting in the same place than there are different resources to support them. Understanding the forces that allow this high level of diversity has been a central focus of ecological and evolutionary theory for many decades.

Presented here are new insights into the marine monoraphid diatom genera Schizostauron and Astartiella, based on molecular and morphological data, including descriptions of new species. Although no unambiguous morphological synapomorphies between the two genera are currently recognized, they are closely related by DNA sequence data. Heterovalvate f...

Hyalosira gene sequences are divided into two clades within different families. We examined authentic material of Hyalosira (isotype material of H. obtusangula, synonymous with H. delicatula) and voucher specimens of published sequences, and pooled our observations of Hyalosira-like taxa from benthic and epizoic habitats in several parts of the glo...

Sea turtles harbour epizoic diatoms of which several taxa are considered exclusively epizoic and possible 'commensals'. The epizoic diatom communities were examined from 124 individuals representing four turtle species (Chelonia mydas, Eretmochelys imbricata, Lepidochelys olivacea and Dermochelys coriacea), from three well-defined areas: Eastern Ca...

The current study focuses on four species from the primarily marine diatom genus Craspedostauros that were observed growing attached to numerous sea turtles and sea turtle-associated barnacles from Croatia and South Africa. Three of the examined taxa, C. danayanus sp. nov., C. legouvelloanus sp. nov., and C. macewanii sp. nov. are described based o...

The Bacillariaceae is a very species-rich family of raphid diatoms and includes the large and taxonomically difficult genus Nitzschia, whose species are often small-celled and finely structured and have few discrete morphological characters visible in the light microscope. The classification of Nitzschia is still mostly based on one developed in th...

Photonics, the manipulation of light at nanoscale, is a key enabling technology with impact in health and energy applications, among others. In most cases photonics still relies on materials and fabrication methods inherited from other disciplines, usually requiring expensive, time consuming and environmentally-unfriendly processes. Recent experime...

In recent years the taxonomy of Haslea has been in flux. We describe several Haslea taxa from Guam, including four new species, in light of these recent findings. Four delicate, fusiform Haslea species are described from a variety of benthic habitats on coral reefs. These species, H. fusiformis comb. nov. and H. alexanderi, H. apoloniae and H. guah...

Detailed morphological documentation is provided for established Proschkinia taxa, including the generitype, P. bulnheimii, and P. complanata, P. complanatula, P. complanatoides and P. hyalosirella, and six new species. All established taxa are characterized from original material from historical collections. The new species described in this paper...

Although previous phylogenetic analyses suggested that the araphid diatom family Plagiogrammaceae is monophyletic, there is still not a clear understanding of relationships among the genera, and the taxonomy of several genera --Dimeregramma and Plagiogramma--remains questionable in light of paraphyly for both genera using molecular and morphologica...

In many marine littoral and sublittoral benthic habitats, we find small diatoms with few features resolvable with light microscopy (LM) other than internal costae across their valves. While classically those internal costae have defined their identification and classification, the use of electron microscopy and of molecular data have started to rev...

The diatom genus Proschkinia is a common element of biofilms covering diverse substrata in saline inland or shallow coastal environments. It can be distinguished from other naviculoid taxa by its lanceolate valves with a fistula located within the central area and numerous open girdle bands with a U-shaped cross-section and a single row of perforat...

The loggerhead sea turtle is the most common species of marine turtle in the Adriatic Sea. Here, the neritic habitats represent important feeding pasture for these omnivorous reptiles. Currently, despite of the extensive conservation effort, what can be called the anthropogenic disturbance remains the greatest threat to these animals. Due to variou...

The loggerhead sea turtle is widely distributed throughout the world's oceans with a now-thriving population in the Mediterranean Sea. Loggerhead sea turtles seem to harbor a diverse assemblage of macro- and micro-epibionts living on their shells and skin. Recent studies focused on sea turtle-associated diatoms indicate that some of them may be exc...

REVIEW Background and aims-Traditionally, extant rhizosolenioid diatom genera have been placed in a single family, the Rhizosoleniaceae. However, preliminary molecular data suggested that the family might be polyphyletic. Therefore, a literature review of the morphological, ultrastructural and molecular data of the rhizosolenioid genera was underta...

Background and aims – The diatom genus Simonsenia has been considered for some time a minor taxon, limited in its distribution to fresh and slightly brackish waters. Recently, knowledge of its diversity and geographic distribution has been enhanced with new species described from brackish-marine waters of the southern Iberian Peninsula and from inl...

A study was made of the ultrastructural variation in a group of conopeate Nitzschia species, primarily marine species from Guam but also including one freshwater species from Costa Rica. Fourteen new species are described: Nitzschia alcyoneae, Nitzschia asteropeae, Nitzschia carahii, Nitzschia celaenoae, Nitzschia dagmannii, Nitzschia electrae, Nit...

New molecular and morphological insights are presented on Campylosira africana and two new species, Extubocellulus cupola sp. nov. and Plagiogrammopsis castigatus sp. nov. Species descriptions were based on LM/SEM micrographs and a dataset with concatenated sequences of SSU, rbcL and psbC loci constructed from 56 cymatosiroid strains isolated from...

Using scanning electron microscopy, Ross and Sims (1971) clarified relationships in the Biddulphiaceae and Eupodiscaceae. They identified characters that could be used to separate biddulphioid genera finding that there were two types of valve structure, poroid and loculate (alveolate), and two types of structure at the summit of the valve elevation...

Several populations of a new Craspedostauros species were observed on museum specimens of juvenile green turtle and Kemp’s ridleys collected from Long Island Beach, New York, USA. The new taxon, Craspedostauros alatus Majewska & Ashworth sp. nov., exhibits a distinctive set of morphological features typical of the genus, including cribrate areolae,...

ABSTRACT: The animal/plant associated microbiota play a key role in the survival and fitness of their hosts. The microbial communities associated with the host’s body, both on the external surfaces and inside the guts, support their host's immune system and provide protection from pathogens. Although sea turtles have been studied by marine biologis...

The current study characterizes numerous populations of epizoic “gomphonemoid” diatoms found on five sea turtle species inhabiting all three oceans, highlighting both the remarkable morphological plasticity found within each of these populations and the lack of morphological discontinuity among them. As diatom epibiosis on sea turtles (and other ma...

Licmophora species are common epiphytes, with new species being discovered in under-sampled areas, and a need for a larger morphological character set for all species. In the rich flora of Guam, there are several distinctive new species, four of which we describe here, with a reconsideration and expansion of their useful taxonomic characters. Licmo...

Dozens of monoclonal cultures of small-celled araphid diatoms from brackish or marine habitats worldwide were analyzed using morphological observations (light and electron microscopy) and molecular data (nuclear-encoded small subunit ribosomal RNA and chloroplast encoded rbcL and psbC). As a result, we established one new genus Gedaniella, distingu...

Dozens of monoclonal cultures of small-celled araphid diatoms from brackish or marine habitats worldwide were analyzed using morphological observations (light and electron microscopy) and molecular data (nuclear-encoded small subunit ribosomal RNA and chloroplast encoded rbcL and psbC). As a result, we established one new genus Gedaniella, distingu...

The diatom Phaeodactylum tricornutum has been used as a model for cell biologists and ecologists for over a century. We have incorporated several new raphid pennates into a three gene phylogenetic dataset (SSU, rbcL, psbC), and recover Gomphonemopsis sp. as sister to P. tricornutum with 100% BS support. This is the first time a close relative has b...

Complete topology of ML phylogenetic tree of pennate diatoms in our three gene (nuclear SSU, rbcL, psbC) dataset. Terminal taxa are identified by name and strain number. Numbers associated with nodes are bootstrap support values. (TIF)

Strain identification and Genbank sequence numbers for newly accessioned material. (DOC)

Localities for diatom floristic survey to determine distribution of Gomphonemopsis cf. exigua. (XLSX)

Constraint trees used in hypothesis testing. All trees are in Newick format. (TXT)

Synedroid diatoms are morphologically characterized by a putative synapomorphic structure called an ocellulimbus, a terminal pore field whose surface is depressed relative to the rest of the valve surface. Among these diatoms is the genus Hyalosynedra Williams and Round. Characters associated with that genus are bilayered wall construction, densely...

Until now only one group of diatoms, the Bacillariaceae, was known to contain heterotrophic representatives. We show that a second group, represented by species in the genus Tursiocola, has undergone evolutionary loss of photosynthesis within the Bacillariophyta. Heterotrophy was evidenced by the presence of only apochlorotic cells in live and moti...

Diatoms are a monophyletic group of eukaryotic, single-celled heterokont algae. Despite years of phylogenetic research, relationships among major groups of diatoms remain uncertain. Here we assess diatom phylogenetic relationships using the plastid genome (plastome). The 22 previously published diatom plastomes showed variable genome size, gene con...

It has been known for a long time that marine mammals, such as whales and dolphins, host a very specific epizoic community on their skin. Whether or not a similar community exists on the carapaces of sea turtles is less studied. The present paper describes two new epizoic diatoms from the genus Achnanthes sensu stricto, Achnanthes elongata and Achn...

The family Cymatosiraceae, composed of two subfamilies (Cymatosiroideae and Extubocelluloideae), are elongate, non-pennate diatoms and are commonly reported in marine planktonic and benthic assemblages all over the world. The combination of the gross bilateral symmetry of the frustule and radial symmetry of the valve poration, distinct pore fields...

Several lineages of raphe-bearing diatoms possess a "stauros," which is a transverse, usually thickened area free of pores across the center of the valve. It has been suggested that this structure has evolved several times across the raphid diatoms, but we have noticed similarities beyond the stauros between two marine genera-Craspedostauros and St...

Medlinella amphoroidea gen. et sp. nov. is described from the dorsal neck skin of loggerhead sea turtles (Caretta caretta). The presence of girdle septa, multiple copulae, and the marine epizoic habitat of Medlinella amphoroidea are characteristic features shared with many species in the similar Tripterion, Chelonicola, and Poulinea genera. The sem...

Pennate diatoms are important contributors to primary production in freshwater and marine habitats. But the extent of their diversity, ecology and evolution is still largely unknown. This is particularly evident among the clades of pennate diatoms without raphe slits, whose diversity is likely underestimated due to their small size and features whi...

Diatoms are important contributors to the benthic microeukaryote flora. This manuscript lays the foundation for future metagenomic and environmental sequencing projects off coastal China by curating diatom DNA sequences from the Yantai region of the Bohai and Yellow Seas (Northeast China). These studies are based on cultures established from sample...

Diatoms are important contributors to the benthic microeukaryote flora. This manuscript lays the foundation for future metagenomic and environmental sequencing projects off coastal China by curating diatom DNA sequences from the Yantai region of the Bohai and Yellow Seas (Northeast China). These studies are based on cultures established from sample...

Plagiogrammaceae, a poorly described family of diatoms, are common inhabitants of the shallow marine littoral zone, occurring either in the sediments or as epiphytes. Previous molecular phylogenies of the Plagiogrammaceae were inferred but included only up to six genera: Plagiogramma, Dimeregramma, Neofragilaria, Talaroneis, Psammogramma and Psammo...

Diatoms are very efficient in their use of available nutrients. Changes in nutrient availability influence the metabolism and the composition of the cell constituents. Since diatoms are valuable candidates to search for oil producing algae, measurements of diatom-produced compounds can be very useful for biotechnology. In order to explore the diver...

Download free eprint from http://www.tandfonline.com/eprint/UNhPxeafE2JUPcICycDG/full. Licmosphenia Mereschkowsky (Licmophorales: Licmophoraceae) is distinguished from Licmophora C. Agardh almost entirely by the presence of an apical window in the septum of the valvocopula. Recently, SEM images of three new species, all with coarse striae, showed t...

Here we present a formal description of Biremis panamae Barka, Witkowski et Weisenborn sp. nov., which was isolated from the marine littoral environment of the Pacific Ocean coast of Panama. The description is based on morphology (light and electron microscopy) and the rbcL, psbC and SSU sequences of one clone of this species. The new species is in...

Diatoms are mostly photosynthetic eukaryotes within the heterokont lineage. Variable plastid genome sizes and extensive genome rearrangements have been observed across the diatom phylogeny, but little is known about plastid genome evolution within order- or family-level clades. The Thalassiosirales is one of the more comprehensively studied orders...

Lucanicum concatenatum is a chain-forming araphid pennate, assigned to Cyclophorales: Cyclophoraceae on the basis of morphological characters and DNA sequences, resembling Neosynedra, but with platelike plastids and striae mostly undiv- ided by vimines. So far it has only been found growing on blue coral, Heliopora coerulea, but we do not suggest t...