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Characteristics of Phylum Annelida

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Lophotrochozoa
They develop by spiral mosaic cleavage
mesoderm
make a coelom by schizocoely
share a trochophore as the ancestral larval form.

Phyla include:
Annelida
Echiura
Sipuncula
Members of phylum Annelida
Segmented worms living in marine, freshwater, and moist terrestrial habitats.

Marine bristle worms, leeches, and the familiar earthworms belong to this group.

15000 Species
Class Polychaeta
mostlly marine segmented worms; parapodia
Annelida Nervous System
Nervous system with a double ventral nerve cord and a pair of ganglia with lateral nerves in each segment

Brain a pair of dorsal cerebral ganglia with connectives to ventral nerve cord.
Where do Annelids Live
Marine, freshwater and terrestrial
Annelid Symmetry
Body bilaterally symmetical
often with distinct head.
metameric which means they have multiple speciallized segments.
Annelid Cell Type
Triploblastic
Annelid Coelom
Coelom (Schizocoel) well developed and divided by septa, except in leeches; coelomic fluid functions as hydrostatic skeleton.
Annelid Digestive System
Digestive system is complete and not segmentally arranged.
Annelid Body
Epithelium secretes outer transparent moist cuticle.

Body wall with outer circular and inner longitudinal muscle.
Annelid Senses
Sensory system of tactile organs, taste buds, statocysts, photoreceptors cells, and eyes with lenses

specialization of head region into differentiated organs, such as tentacles, palps, and eyespots of polycaetes.
Annelid Reproduction
Asexual reproduction by fission and fragmentation

Capable of complete regeneration.
Annelid Sexs
Hermaphroditic or separate sexes

larvae are trochophore type

asexual reproduction by budding in some.

spiral cleavage and mosaic development
Annelid Excretory
Excretory system typically a pair of nephridia for each segment

Nephridia remove waste from blood as well as from coelom.
Annelid Gas Exchange
Respritory gas exchange through skin, gills, or parapodia.
Annelid Circulatory System
Circulatory system closed with muscular blood vessels and aortic arches for pumping blood, segmentally arranged

respiratory pigments often present

amebocytes in blood plasma.