A creature which self generates it’s food requirement through photosynthesis

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A creature which self generates it’s food requirement through photosynthesis

Elysia chlorotica is a sea slug which is about 5 cm long. It’s a marine gastropod. It’s habitat is the shallow waters of the east coast of North america. This slug looks like a green leaf. When the sun shines it spreads out as if it’s sunbathing. The creature feeds on filamentous algae such as Vaucheria littorea. During digestion the photosynthetic cells from the algae only destroy partially. Their chloroplasts remain as it is and allow Elysia to feed itself from the products of photosynthesis. Scientists call this scenario Chloroplastic symbiosis or kleptoplasty. This is also known as Chloroplast robbery. Chlorophyll a pigment which is in chloroplasts capture light during photosynthesis. It’s this pigment that gives the slug its green color. These creatures have a highly branched digestive system. When the chlorophyll is present in this system it makes the creature look like a green leaf. Several related species of the same family have these abilities and behavior.

Usually many marine species retain chlorophyll cells absorbed from their food, mostly the algae. The creatures integrate them into their digestive system and use them for their own benefit. Normally after a short period, this has to be renewed by taking more food intake.

But in the case of Elysia Chlorotica, things are a bit different. It has acquired chloroplasts during its development (transforming from larval to adult). Chloroplasts then remain functional throughout the entire life of this creature. So Elysia Chlorotica only feeds on algae at the beginning of its life. Afterwards it exclusively generates energy for itself through photosynthesis. However it’s controversial if chloroplast is essential to the life of this creature.

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Anatomy of the sacoglossan mollusc Elysia chlorotica.(A) Sea slug consuming its obligate algal food Vaucheria litorea. Small, punctate green circles are the plastids located within the extensive digestive diverticula of the animal. (B) A defined tubule of the digestive diverticula extending into the parapodial region of the animal (arrow). The digestive system consists of densely packed tubules that branch throughout the animal's body. Each tubule is made up of a layer of single cells containing animal organelles and numerous algal plastids. This cell layer surrounds the lumen. (C) Magnified image of the epidermis of E. chlorotica showing densely packed plastids. The animals are light grey in color without their resident plastids, which contribute chlorophyll to render the sea slugs bright green.

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