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Daily News Analysis

SEA SLUGS

28th March, 2023 Environment

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Context: A citizen science project documents unique sea slugs from Visakhapatnam coast.

Details: 

What are slugs?

  • Sea slugs belong to Phylum Mollusca and Class Gastropoda.
  • They look like naked snails, i.e., without shells.
  • Sea slugs are of course those found in the sea. There are also slugs that live on land.

Types:

  • Sea slugs may be generally differentiated into two main groups.
  • Members of one group breathe with lungs. These include pulmonate sea slugs such as the Onch slugs of the Family Onchidiidae.
  • Members of another group breathe with gills. These include the Opisthobranchs or just plain sea slugs.

Where seen?

  • Onch slugs can be found among the rocks near the high water mark, while other slugs are found further down where it is almost always covered in water.
  • Some are burrowing and many are found on or near their food.
  • Some sea slugs are stunningly beautiful, among them, nudibranchs.

Features:

  • Sea slugs range from large sea hares of 10cm to tiny nudibranchs 1cm or less.
  • Sea slugs generally lack large external shells.
  • Some many have external shells but cannot fully retract their bodies into these shells like other 'regular' snails do. Other sea slugs may have internal shells.
  • Most sea slugs don't have any shells at all.
  • Although they lack shells, slugs are not helpless. Some taste bad, others release toxic or irritating substances.
  • Yet others incorporate stingers of sea anemones, hydroids and other cnidarians that they feed on and use these to protect themselves.

What do they eat?

  • As a group, sea slugs eat a wide variety of plants and animals.
  • But each species usually specialises in one kind of food.

Threats:

  • Some slugs may release highly toxic substances when stressed.
  • Like other creatures of the intertidal zone, they are affected by human activities such as reclamation and pollution.
  • Trampling by careless visitors and over-collection can also have an impact on local populations.

 

PRACTICE QUESTION

Q) Which of the following statements is/are correct with reference to Sea Slug?

a. They lack an external shell.

b. They are found in sea only.

  1. Only a
  2. Only b
  3. Both a and b
  4. Neither a nor b

Answer: Option 2

https://www.thehindu.com/sci-tech/energy-and-environment/a-citizen-science-project-documents-unique-sea-slugs-from-visakhapatnam-coast/article66652146.ece