Recent morphometric and breeding studies of diatoms show that the present species classification is too coarse and hides significant diversity. Many species are subdivided into phenodemes, which often differ in cell size, shape, stria density and pattern, but may also have different ultrastructural features. In raphid diatoms these can include the form of the raphe endings, details of the pore occlusions, and the structure of the girdle, while chloroplast structure can also vary. The phenodemes can be sympatric or allopatric. In Sellaphora pupula and other species, sympatric phenodemes are reproductively isolated. It is recommended that such demes are recognized as separate species; the total number of diatom species worldwide may thus be at least 2 × 105. Use of a fine-grained classification reveals that many diatom species may be endemics, some restricted to a single lake or catchment, others to wider areas. Environmental impact assessments and conservation strategies must begin to take account of endemism and rarity among microscopic algae and protists.

Biodiversity, biogeography and conservation of diatoms

Catalogue of the diatom genera

Nature’s silicon marvel, the diatoms have lately astounded the scientific community with its intricate designs and lasting durability. Diatoms are a major group of phytoplanktons involved in the biogeochemical cycling of silica and are virtually inherent in every environment ranging from water to ice to soil. The usage of diatoms has proved prudently cost effective and its handling neither requires costly materials nor sophisticated instruments. Diatoms can easily be acquired from the environment, their culture requires ambient condition and does not involve any costly media or expensive instruments, besides, and they can be transported in small quantities and proliferated to a desirable confluence from that scratch, thus are excellent cost effective industrial raw material. Naturally occurring diatom frustules are a source of nanomaterials. Their silica bio-shells have raised curiosity among nanotechnologists who hope that diatoms will facilitate tailoring minuscule structures which are beyond the capabilities of material scientists. Additionally, there is a colossal diversity in the dimensions of diatoms as the frustule shape differs from species to species; this provides a scope for the choice of a particular species of diatom to be tailored to an exacting requisite, thus paving the way to create desired three dimensional nanocomposites. The present article explores the use of diatoms in various arenas of science, may it be in nanotechnology, biotechnology, environmental science, biophysics or biochemistry and summarizes facets of diatom biology under one umbrella. Special emphasis has been given to biosilicification, biomineralization and use of diatoms as nanomaterial’s, drug delivery vehicles, optical and immune-biosensors, filters, immunodiagnostics, aquaculture feeds, lab-on-a-chip, metabolites, and biofuels.

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All New Faces of Diatoms: Potential Source of Nanomaterials and Beyond.

Freshwater and Littoral Diatoms from Cuba

1. Lough Neagh is a large eutrophic lake with a high dissolved silica (SiO 2 ) concentration arising from the basaltic rock in parts of the catchment and the normal winter maximum concentration is over 8 mg L -1 . Based on frequent observations between 1974 and 1997, the annual cycles of SiO 2 input, uptake and release are explored. 2. Large spring blooms of the planktonic diatoms Aulacoseira subarctica and Stephanodiscus astraea occur every year and are terminated by SiO 2 depletion. Although there are periods when one diatom species has dominated the other, over the period as a whole, the two diatoms appear to be in a stable coexistence. 3. A model of the effect of river inputs on lake concentration shows that without SiO 2 release from the sediment, the maximum spring dissolved SiO 2 concentration (and hence diatom crop) would be only about one-third of that actually observed. 4. It is concluded that within-lake processes play a large role and are potentially more variable than catchment processes in determining the available SiO 2 in Lough Neagh. 5. The role of benthic animals, especially Chironomus anthracinus, in the sediment SiO 2 release process is discussed. Field data suggest the SiO 2 release rate is highly sensitive to temperature, but this could be partly caused by an interaction between temperature and animal activity.

Silica and diatom growth in Lough Neagh: the importance of internal recycling

A new marine diatom genus and species, Nephroneis macintirei Amspoker, has been identified from the epipsammon of Scripps Beach, La Jolla, California, U.S.A. This taxon is reniform in valve outline with a rimoportula at one or both poles. Poroid areolae are arranged in transapical striae over a broad mantle, but this organization is lost over the valve face, the areolae here being scattered. The valve lacks an axial area, raphe, apical pore fields, elevations, costae, pseudosepta, and a marginal ring of processes. Elements of the cingulum lack ligulae, antiligulae and septa. The genus is tentatively assigned to the heterogeneous araphid family, Diatomaceae sensu Simonsen 1979.

Nephroneis macintirei, gen. et sp. nov., a marine araphid diatom from california, u.s.a.

Dimerogramma (Dimeregramma) hyalinum Hustedt, a relatively common diatom of marine littoral benthic assemblages, was described from mud samples collected from Beaufort, North Carolina, U.S.A. in 1955. Hustedt and later workers noted that the frustule of this species was completely hyaline. Studies of D. hyalinum from the type sample and from material collected from Scripps Beach, California, U.S.A. in 1972 and Beaufort, North Carolina in 2006 with the light and scanning electron microscopes confirmed the hyaline nature of the valve face and cingulum, but revealed the presence of apical slit fields located on the mantle at both apices of the valve. The valves of D. hyalinum lack the uniseriate striae composed of round areolae, sternum, transapical ribs, and spines arising near the mantle of the valve characteristic of Dimeregramma Ralfs in Pritchard. Furthermore, the apical pore fields composed of loosely packed porelli found in Dimeregramma differ markedly from the apical slit fields observed in D. hyalin...

Transfer of the marine diatom dimerogramma hyalinum hustedt to the new araphid genus hyaloneis

Eunotogramma litorale sp. nov. is described from marine littoral epipsammic assemblages collected from San Diego County, Southern California, USA. The valves of this common species are semi-elliptical in outline with a curved dorsal margin and a more or less straight ventral margin. Each valve has 1–6 transapical costae. Areolae are absent on the valve face; a small rimoportula is usually present on the valve face or uppermost mantle near each pole. One or more rimoportulae are usually found in a row along the dorsal mantle between the costae. Small areolae, visible only with SEM, are typically found between costae on the ventral mantle and along the ventral portion of the pars exterior of the valvocopulae. E. litorale can be distinguished from three other Eunotogramma species with hyaline valve faces by the semi-elliptical shape of its valve outline. The similarity of the internal openings of the rimoportuale of E. litorale and some Aulacodiscus species suggests that E. litorale may be allied with Aulaco...

Eunotogramma litorale sp. nov., a marine epipsammic diatom from Southern California, USA

Grunow first proposed the epithet Eunotogramma laeve in 1879 for specimens collected from North Carolina, USA and mounted on strewn slide no. 257 in the Cleve and Moller (C&M) exsiccatae. In 1882, he again listed E. laeve from material collected from Florida, USA and mounted on slide no. 320 from the same exsiccatae. Examination of C&M slides no. 257 and 320 from the Farlow Herbarium and the Academy of Natural Sciences of Philadelphia with the light microscope (LM) reveals the presence of three Eunotogramma species on the two slides. Under the LM, the specimens on C&M slide no. 257 have areolate frustules, whereas the two species on C&M slide no. 320 have hyaline frustules. Given that there is no nomenclatural type for E. laeve, the areolate specimens found on the C&M slide no. 257 from the Farlow Herbarium are here designated as the lectotype for the species.

Lectotypification of Eunotogramma laeve

Artificial flower patches were used to test whether floral calcium oxalate crystals (which reflect UV light) affect honey bee (Apis mellifera) flower fidelity, and whether honey bees will use calci...

Michael C. Amspoker

Papers

Nephroneis macintirei, gen. et sp. nov., a marine araphid diatom from california, u.s.a.

Transfer of the marine diatom dimerogramma hyalinum hustedt to the new araphid genus hyaloneis

Eunotogramma litorale sp. nov., a marine epipsammic diatom from Southern California, USA

Lectotypification of Eunotogramma laeve

Floral calcium oxalate crystals as foraging cues for honey bees