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Context

• Researchers at the Pune-based Agharkar Research Institute (ARI) have discovered a new species of single-cell algae, known as diatoms, from the northern Western Ghats — and named it after a veteran geo-archaeologist from the city, the late Professor S N Rajaguru.

S N Rajaguru was a former faculty member of Deccan College and known for his attempts to link biological and archaeological remains during excavations. It was through Rajaguru’s extensive studies that researchers today have a clear time-frame of India’s paleo-environment. He retired in 1994 as Joint Director of Deccan College, and passed away in December 2022.

About the new species

• The new species named Gomphonema rajaguruii was found in a semi-aquatic environment along the wet walls in Maharashtra's popular hill station Mahabaleshwar in Satara district.
• Gomphonema rajaguruii is unique because it shows the characteristics of two genus — Gomphonema and Gomphoneis.
• This is a freshwater diatom species.
• Diatoms showcasing such dual characteristics are very rare.
• Diatoms can be found in freshwater and brackish water, and are commonly traced in lakes, rivers, streams, rivulets and the sea.
• Similar to plants and trees that produce oxygen during the process called photosynthesis, diatoms, too, supply oxygen to the atmosphere.

About Diatom

• A diatom is a unicellular eukaryotic alga characterized by having a siliceous covering and a symmetrical body.
• Diatoms are mostly aquatic, being found in fresh, brackish, and saltwater. Some are found in moist places, such as soil.
• Diatoms comprise the taxonomic phylum Bacillariophyta.
• They may be solitary or in colonies. When in colonies, they form various shapes, e.g. ribbons, zigzags, stars, or fans.

Classification of Diatoms

• The phylum Bacillariophyta includes the diatoms. The taxonomic classes of diatoms under Bacillariophyta are as follows:

• • Coscinodiscophyceae (centric diatoms)
  • Fragilariophyceae (araphids, i.e. pennate diatoms without a raphe)
  • Bacillariophyceae (raphids, pennate diatoms with a raphe)

General Characteristics

Unicellularity

• Diatoms are a major group of microscopic algae and are among the most common types of phytoplankton.
• Diatoms are unicellular.
• The cell size may range from 2 to 200 micrometers. They may live singly or in colonies.

Frustule

• A characteristic feature of diatom cells is that they are encased within a unique cell wall made of silica (i.e. hydrated silicon dioxide).
• The siliceous cell wall is called a frustule. 

Thecae

• Diatom cell has two distinct halves: the hypotheca (the slightly smaller theca) and the epitheca (the slightly larger theca.

Pigments

• Diatoms have yellowish-brown to olive-brown chloroplasts due to the predominance of carotenoids (fucoxanthin), and xanthophylls. Their chloroplasts are four-membraned.

Nutrition

• Most diatoms are photosynthetic whereas a few of them are heterotrophs.

Food reserve

• Their carbohydrate reserve is chrysolaminarin. They also store lipids.

Lacking flagella

• Diatoms do not have flagella except for the male gametes of centric diatoms that have smooth flagella.

Reproduction

• Diatoms reproduce asexually by binary fission.

Buoyancy

• Diatoms are able to stay suspended through various mechanisms. 

Ecology

• Diatoms are referred to as the jewels of the sea because of their structural coloration. They are major oxygen producers on Earth. They generate about 20% oxygen annually.

PRACTICE QUESTION Q) Which of the following statements with reference to Diatoms is/are correct? 1. All diatoms are photosynthetic. 2. Diatoms are referred to as the jewels of the sea. 3. A diatom is a unicellular eukaryotic alga. 1 and 2 2 and 3 1 and 3 1, 2 and 3 Correct Answer: b

https://indianexpress.com/article/cities/pune/new-algae-species-mahabaleshwar-named-pune-scientist-8632972/