What are Chrysophytes?
Chrysophytes are plant-like protists that can be found in marine and freshwater environments which are often low in calcium.
- There are three main types of chrysophytes: Diatoms (Bacillariophyta), Golden-brown algae (Chrysophyceae), and Yellow-green algae (Xanthophyceae).
- Although many are unicellular and free swimming, some chrysophytes, like the dinobryon above, join together and form colonies.
- There are over 1000 described species of Chrysophytes, and, because there are so many species, there is no common cell structure shared by them.
- Some species have cell walls made of cellulose strengthened by silica compounds, while others are amoeboid without any cell walls.
Some Members of Chrysophytes
Methods of Feeding, Movement, and Reproduction
- Since chrysophytes are plant-like and have chloroplasts, they are mainly autotrophic.
- If there is inadequate lighting, they can become heterotrophic, especially in areas with high dissolved foods concentrations.
- Chrysophytes are mainly non-motile, but they do have two flagella for movement in harsh conditions.
- Most chrysophytes reproduce asexually through meiosis, but diatoms reproduce sexually, dividing and exchanging parts under certain conditions.
Chrysophyta: Relatives, Affect on Humans, and Role in Food Chain
- Chrysophyta is algae, so their closest relatives are the six other divisions of algae: Euglenophyta, Pyrrophyta, Chlorophyta, Rhodophyta, Phaeophyta, and Xanthophyta.
- Being the main components of plankton and nanoplankton, diatoms and Chrysophyceae are the foundation of the marine food chain, functioning as the producers.
- Chrysophyta can be considered helpful to humans. We use them in toothpaste, scouring products, and filters.
- As autotrophs, they provide a substantial amount of oxygen in the atmosphere, as well.
- Also, because chrysophytes store their food as oils, they can be used for biofuel.
- Diatoms are especially effective in biobutanol production because of their small size.
Additional Information: ChrysophytesDiatoms - Golden Algae or Jewels of the SeaStructure
The members of Division - Bacillariophyta are known as Diatoms. Diatoms mean-"Cut into two". This name is based on the cell wall of diatoms, which is divided into two parts. They have Holophytic mode of nutrition because they possess chloroplast.
Examples: Navicula, Cyclotella, Pinnularia.
- They are found in different shapes such as circular, rectangular, triangular, elongated and boat-shaped.
- The cell wall of diatoms is made up of cellulose in which silica particles are embedded in many places, due to which the cell wall appears to be made up of silica. This silicate cell wall is called "shell" or "frustule".
- Their cell wall is made up of two halves, which are arranged like the lids of a soapbox. These half parts are collectively known as theca. The part which is present on the upper side acts as the lid and known as the epitheca, and the other basal part is known as the hypotheca. The place where the two parts overlap each other is called a girdle.
Note: Their cell wall has silica in very large quantity. Due to this reason, their cell wall is hard. The cell wall does not get destroyed after their death so, at the bottom of the sea, very huge rocks of dead diatoms are formed which are known as "diatomite" or "diatomaceous earth" or "kieselguhr".
Try yourself:Diatom frustule/shell is made of
The shell of diatoms is called frustule and is made of silica, cellulose, and pectic compounds.
- The diploid nucleus is present in Diatom.
- Their cells have chloroplasts, in which pigments are present, Chlorophyll 'a', Chlorophyll 'c', and xanthophyll (fucoxanthin). Due to these pigments, it appears golden coloured.
- Stored food: Leucosin (Chrysolaminarian) & fats (Oil).
- Movement: They are immotile because flagella are absent. They float on the surface of the water with the help of low molecular weight stored fats.
Mainly asexual: Binary fission.
Sexual reproduction: Very rare - by gametic meiosis.
The zygote formed during sexual reproduction is called as "Auxospore". Auxospore is an asexual structure.
Use of Diatoms
Try yourself:Leucosin (Chrysolaminarin) is a carbohydrate which is stored as reserve food in case of
Organism - Reserve food
Diatom – Leucosin (Chrysolaminarin)
Euglena – Paramylon
Dinoflagellates – Carbohydrate and oil
Paramecium – Glycogen granules
- Filtration of oils and syrups.
- Stone polishing.
- As "Heat insulator" in steam boilers, i.e. they are used as thermostat because the kieselguhr is a bad conductor of heat.
Dinoflagellates: Protists With Two Flagella
Note: It is also classified in protozoa due to its holozoic mode of nutrition and colourless body.
Try yourself:Which is not a feature of dinoflagellates?
Features of dinoflagellates.
- Cell wall has stiff cellulose plates on the outer surface
- Release toxins
- Causes red tides
- Mostly marine and photosynthetic
Parts of Dinoflagellates
- Dinoflagellates are haploid. Histone proteins are absent. Due to this reason Dinoflagellates are called as Mesokaryote.
- They have an osmoregulatory structure called 'Pusule'.
- Dinoflagellates are yellow-brown or golden brown in colour. These colour of Dinoflagellates are due to the pigments present in them - Chlorophyll 'a', Chlorophyll 'c' and Xanthophylls (Dinoxanthin & Didinoxanthin).
- They have starch as stored food.
- Mainly Asexual – Binary fission.
- Sexual reproduction is very rare. Dinoflagellates are haploid, so they reproduce by Zygotic meiosis. Therefore, their life cycle is haplontic type.
Note: Exceptionally Noctiluca is diploid so it reproduce by gametic meiosis, therefore its life cycle is Diplontic type.
Additional Information: Dinoflagellates
Maximum Dinoflagellates (Example: Noctiluca, Gonyaulax, Pyrocystis) show 'bioluminescence'. Their protoplasm has photogenic granules. These granules are made up of luciferin protein.
Energy is released by the oxidation of luciferin. This energy is liberated in the form of light during the night. This is known as "bioluminescence. So these dinoflagellates are also known as 'night light'.
Gonyaulax spreads on the surface of seawater, through rapid multiplication due to which the seawater appears red. It is called red tide. It is also responsible for water bloom.
Both Gymnodinium & Gonyaulax are toxic. They secrete toxins, which are known as "saxitoxin". These toxins can cause paralysis in human beings. Humans acquire these toxins through the food chain. These algae also affect marine animals.
Noctiluca is known as 'sea - ghost' because it glows at night.
Dinoflagellates are also called "fire algae" because they appear as glowing light due to bioluminescence. Division - Chrysophyta/Bacillariophyta - DIATOMS.
Try yourself:Sea water glows during night mainly due to occurrence of
- Sea water glows during night mainly due to occurrence of Noctiluca.
- An organism which exhibit light in the night which is due to chemical luciferin. This process is called as bioluminiscence.
- An protistan group which exhibits bioluminiscence is Dinoflagellates. An example for Dinoflagellates is Noctiluca