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In this article we will discuss about the structure of Arenicola with the help of a diagram.
1. It is a brownish green burrowing and tubiciolous marine polychaete.
2. Commonly called ‘lug worm’ and is found in muddy regions along Mediterranean and turopean shores.
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3. It forms “U” shaped burrows which are lined internally with mucous.
4. Body cylindrical, vermiform, metamerically segmented and measures about 15 cm. The segments are annulate and without appendages.
5. Head not distinct and peristomium and prostomium are distinct and without appendages.
6. Body is divisible into three distinct regions i.e., the anterior, middle & posterior. The anterior region comprises of trilobed prostomum, triannulate prostomium and 6 segments which are chaetigerous. The prostomium is without eyes and tentacles. Each segment bears rudimentary, parapodia which comprises a notopodium and a neuropodium. The neuropodial setae are modified into cirri.
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7. Segments are annulate, peristomium without appendages and pharynx is protruslble and papillate.
8. The middle region comprises of 13 segments. Each segment bears a pair of neuropodium and branched gills.
9. Posterior region bears indefinite number of segments which are all devoid of parapodia and gills.
10. Anus terminal and parapodium comprises of a notopodium and a neuropodium. The neuropodial setae are modified into uncini.
11. Nephndia six pairs and the worm’ is commonly used as fish bait.
