Sea Butterflies -UPSC Current Affairs

Description

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Context:

It has been observed that Ocean acidification is not only more dangerous for shelled, smaller sea butterflies but can impact entire ocean food web.

Background

The sea butterflies, a suborder of sea snails, are tiny creatures that play a big role in the marine ecosystem.
But the smallest species in this group found in the Southern Ocean are extremely vulnerable to climate change and their population is shrinking in a warming world.
The shelled pteropods (group of free-swimming sea snails) live at or very close to the ocean surface.
Like snails, they have muscular feet that they use as flappers to swim around in water, instead of glide on solid surface.
As the sea absorbs an increasing quantity of carbon dioxide (CO2) that turns the water more acidic, the thin outer casing, or the ‘homes’ of these small sea butterflies, dissolve.
This leaves them exposed, making it difficult for these delicate species to survive.

IN A NUTSHELL

Pteropods are among the marine creatures most vulnerable to ocean acidification.
Ocean acidification lowers the availability of the mineral aragonite that pteropods use to form their shell, hindering this snail from building its protective armor.
The decline of these key organisms would result in dramatic impacts for the entire marine food web.

About Sea butterflies

Scientific name: Thecosomata
They are a taxonomic suborder of small pelagic swimming sea snails.
They have some form of calcified shell, although it is often very light and / or transparent.
The sea butterflies include some of the world's most abundant gastropod species, and because of their large numbers are an essential part of the food chain, and a significant contributor to the oceanic carbon cycle.
The sea butterflies are included in the Pteropoda order, and are also included in the informal group Opisthobranchia.

Morphology

Sea butterflies float and swim freely in the water, and are carried along with the currents.
This has led to a number of adaptations in their bodies.

Importance in the food chain

These creatures, which range from lentil- to orange-sized, are eaten by various marine species, including a wide variety of fish that are, in turn, consumed by penguins and polar bears.
The sea butterflies form the sole food source of their relatives, the Gymnosomata.
They are also consumed by sea birds, whales, and commercially important fish.
However, if sea butterflies are consumed in large quantities fish can get "black gut", which makes them unsellable.