Classification:

• Phylum : Annelida
• Class : Polychaeta
• Order : Errantia
• Genus : Heteronereis

Comments:

1. 1. Heteronereis is the sexual phase of Nereis in which marked modifications occur in the posterior part segment of the body which contain gonads.
2. 2. During breeding season, calm worm leaves its tube and becomes free-swimming.
3. 3. Body is differentiated into asexual anterior atoke and a popsterior sexual epitoke which contains gametes.
4. 4. Epitoke or posterior part becomes morphologically modified as the parapodia swimming function swimming.
5. 5. Parapodia of Heteronereis contain additional foliaceous lobs and setae becomes oar-like. The notopodium and neuropodium.
6. 6. Peristomial cirri becomes large, Special sensory papillae develop on anal segment.
7. 7. Prostomium contains peristomial tentacle, prostomial ocelli and prostomial palp.
8. Peristomium contains peristomial palp. Peristomium contains peristomial tentacles.
9. 8. Muscles and alimentary canal are reduced or become degenerated due to large development of gonads.
10. 9. There is no marked sexual dimorphism in both sex but the females tend to become orange or reddish.

Source:

1. Practical Zoology Invertebrates by S.S.Lal. 2. A Manual of Practical Zoology Chordates by Dr. P.S. Verma.