Phylum Annelida

Phylum annelida

UNIQUE CHARACTERISTIC OF ANNELIDA

-         The phylum Annelida contains segmented worms

-         Bilaterally symmetrical and tiploblastic

-         Body cavity is a true coelom,often divided by internal septa

MERISTEM

-         Have an anterior prostonium and posterior pygidium both nonsegmented

-         Each segmen usually bears one or more chitinous bristles called setae; help anchor segments

NERVOUS SYSTEM

-         Consists of  brain which is connected to a pair of ventralnlongitudinal nerve cord with a ganglion in each segmented

CIRCULATORY SYSTEM

-         Closed circulatory system in which the blood is always enclosed within blood vessel that run the length of the body and branch to every segmented

EXCRETORY SYSTEM

-         With ciliated funnels that remove waste from the coelomic fluid open to the outside via excretory pores

REPRODUCTIVE SYSTEM

-         Most annelids are hermaphoroditic but their usually cross fertilizers

THERE ARE THREE MAJOR CLASSES WITHIN THE PHYLUM ANNELIDE

CLASS POLYCHAETA

-         Mostly marine worms such as Nereis

-         Each segment is equipped with a pair of fleshy paddle-like structures-parapodia used in locomotion

-         Most are marine

CLASS HIRUDINEA

-         The leeches such as hirudo

-         Prostomium is well equipped with sensory and fedding structure

-         Body is dorso-ventrally flattened

CLASS OLIGOCHAETA

-         Many of the morphological structures are reduse when compared to the polychaetes

-         Prostomium lacks sensory structure

-         Parapodia are absent each segmented usually contains one or more pairs of setae used in locomotion