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In this classifica­tion no Linnaean categories of above relatives this kind of as superfamily, buy, and subclass are made use of. Again, Westheide (1997) divided Polychaeta into 25 orders which include things like all the de­scribed species.

Pechenik (2000) classified Annelida into four courses:rn(iii) Pogonophora and. He contains oligochaetes (Oligochaeta) and leeches (Hirudinea) beneath the class Clitellata and areas all the species into two sub­classes:rn(i) Oligochaeta (earthworms) and.

rn(ii) Hirudinea (leeches). Brusca and Brusca (2003) documented that the new phylogenetic reasearch signifies the unification of two courses, Oligochaeta and Hirudinea into a solitary class Clitellata. The scheme of classification has adopted in this e-book ( ) from «Invertebrate Zoology» prepared by Ruppert and Barnes (1994).

Classification with Characters:Class one. Polychaeta (Gk. poly – several chaeta = setae):1.

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Physique elongated, segmented with iden­tical, cylindrical physique segments. 2. Anterior finish modified into a head. 3.

A distrinct head bears sensory ap­pendages, these types of as eyes, antennae, cirri and palps. 4. Many setae on the trunk seg­ments, consequently called polychaeta.

5. Every single human body section bears a pair of fleshy, lateral, paddle-like outgrowths, known as parapodia, bearing many long setae in setigerous sacs. The parapodia act as locomotory and res­piratory organs.

6. Parapodia essentially biramous and supported by acicula. 7. Clitellum absent. 8. Alimentary canal is furnished with an eversible buccal location and protrusible pharynx.

9. Highly vascularised gills are current in most large-sized polychaetes made use of for fuel trade.

10. Brain elaborate is same than oligochaeta and divided into 3 areas:rn(ii) Mid-brain and. 11. Protonephridia present in a range of families. Segmental metanephridial units in most conditions.

12. Sexes independent (gonochoristic) in most. 13. Epitoky, a reproductive phenomenon found in some polychaetes (e. g. , nereids, syllids and eunicids). 14. Fertilization external. 15. A trochophore larval phase in the lifetime cycle. 16. Solely marine, and largely car­nivorous but some are herbivorous. Scheme of Classification:Distribution:Fauvel (1953) described that quite a few of the polychaetes are definitely cosmopolitan and most of the species are frequent in the Indo-Pacific coasts. Numerous species have a throughout the world dis­tribution and the inter-tropical are the exact same in all the oceans. As a result the distribution of polychaeta is mostly constrained by temperature. Trend in polychaete classification:The class polychaeta is not divided into subclasses or orders. Some authors, this kind of as Knox (1972) divided into subclass rank:rn(i) Subclass Errantia and. rn(ii) Subclass Sedentaria. But this subdivision is an artifi­cial, not a pure a single. So most of the re­searchers divide polychaeta into two teams. rn(A) Group I. Polychaeta errantia (Wan­dering polychaetes) [L. mantis = wandering]:rn(i) Many and commonly identical segments.