Heteronereis

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Heteronereis



CLASSIFICATION

Phylum: Annelida

Class: Polychaeta

Genus: Heteronereis


COMMENTS:

• Heteronereis is the sexual form of Nereis.

•Some species of Nereis exhibit dimorphism and two distinct phases, Nereis phase & Heteronereis phase, occur in their life.

•In such forms, the sexual maturity accompanied by certain changes in structure.

•Heteronereis phase is the sexual phase exhibits the following characteristic features:

•Eyes become large & much more prominent, and highly sensitive to light.

•The body shows two distinct regions, an anterior atoke or non- sexual region and a posterior modified epitoke or sexual region which contains ova & sperms.

•Parapodia in the posterior sexual region of the body become enlarged, vascular & foliaceous and setae become oar - shaped which help in active swimming.

•Dorsal & ventral cirri of the parapodia appears to be highly enlarged.

•The notopodium & neuropodium become large & leaf-like & act as fins & gills.

•Peristomial cirri become large.

•Special sensory papillae develop on anal segment.

•Due to excessive development of gonads, the muscles & alimentary canal are reduced.







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