Plantlike Protists:Diatoms

HUFALARNARISMATONGCO

CharacteristicsDiatoms are one of the most beautiful organisms, though microscopic.They are unicellular eukaryotes, under class Bacillariophyceae.All diatoms are enclosed by a frustule, which is like a cell wall specially for diatoms.

CharacteristicsDiatoms divide through mitotic cell division, but some use auxospores, a kind of sexual reproduction.They may be simple or branched, filamentous, and even enveloped in a gelatinous envelope or tube.

StructureDiatoms have cell walls shaped like tiny pill boxes, with many different sizes, shapes, and orientations. They are usually symmetrical.These cell walls, along with other parts like the frustule, valves, and girdles, are made up of silica (SiO2) and pectin.

StructureDiatoms do not have strong, visible colors on their own. In colonies, they have a yellowish tinge due to their plastids.With regards to shape, diatoms are classified as either centric (with concentric markings on halves) or pennate (markings separated by a median)

HabitatDiatoms live in cold waters with low salinity. In freshwater, they can also be found on rocks, mud, or plants in the area.In marine biomes, diatoms can live in the intestinal tracts of organisms, in their shells, and even on macroalgae.

They are found in the littoral zone of the ocean.The habitats of diatoms could depend on currents, and other animals. They could become attached to birds, or fish scales, and become widely scattered.

NutritionDiatoms are mostly photosynthetic, but some are heterotrophic.Because of this, they normally live in an area where there is sufficient light and nutrients.Diatoms are non-motile, so their shape and orientation help them with nutrition.

ReproductionEven if diatoms are non-motile, some of them have sperm with flagella, though restricted to gliding. Their division is mainly asexual through binary fission.With this, however, the diatom’s size decreases.

For diatoms that undergo sexual reproduction with auxospores, meiosis takes place.This happens when the vegetative diploid cells produce male and female gametes and the zygote forms an auxospore.

EcologyDiatoms compromise a large amount of primary productivity because of their photosynthesis.In almost any lighted water biome, there are diatoms.Diatoms are important in the marine food chain to zooplankton and other filter feeders.

EcologyWhen diatoms die, they sink to the bottom of the seabed. Eventually, the build up of trillions of shells forms a crumbly white sediment called diatomite.This is used for pool filters and abrasives, including toothpaste.

ExamplesThalassiosira pseudonana

The Thalassiosira pseudonana is a centric diatom. It is the first eukaryotic phytoplankton to be used for genome sequencing.

ExamplesPhaeodactylum tricornutum

The Phaeodactylum tricornutum is a pennate diatom, and has also been used for genetic sequencing.

ExamplesAchnanthes felinophila

The Achnanthes felinophila is a species of diatom with valves that undulate and have rounded ends.

Sourceshttp://en.wikipedia.org/wiki/Diatomshttp://www.daviddarling.info/encyclopedia/D/diatom.htmlhttp://westerndiatoms.colorado.edu/taxa/species/achnanthes_felinophilahttp://www.mbari.org/staff/conn/botany/diatoms/john/basics/eco.htm