Classification of phylum annelids 

Classification and Diversity of the Phylum Annelida by focussing on the class Polychaeta, class Oligochaeta and the class Hirudinea.

 

Character	Polychaeta	Oligochaeta	Hirudinea
Clitellum	Absent	Present	Present
Setae	Present	Present	Lack setae
Parapodia	Present	Lack parapodia	Lack parapodia
Body shape	Perfect segmented body	long, segmented, tubular bodies	Dorso-ventrally flattened. Tapers at the anterior end.
Cephalization	Present	Absent	Absent
External segmentation	present	present	32 -34 segments
Internal segmentation	present	present	Not clear
Coelom	Present.	Filled with coelomic fluid	Reduced to a system of canals.
Method of locomotion	Free living & sedentary forms	Peristaltic contraction	Looping movements
Muscle layers	Well-developed longitudinal muscle, thin circular muscle	Circular & longitudinal muscle layers	Circular & longitudinal muscle  layers
Respiratory surface	Possess gills. By Parapodia  & epidermis.	Lack gills Vascular network	By network of capillaries beneath the epidermis.
Arrangement of gonads	Gonads have many body segment.	Paired gonads . Limited only anterior segments.	Locate within canals
Sexes	Usually separate Asexual reproduction is present	Hermaphrodites Asexual reproduction is present	Hermaphrodites Asexual reproduction is absent
Larvae stage	Present	Absent	Absent

More articles about,

•  Diversity of class Polychaeta.
•  Diversity of class Oligochaeta.
•  Diversity of class Hirudinea.