They develop by spiral mosaic cleavage
make a coelom by schizocoely
share a trochophore as the ancestral larval form.
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.
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
Body bilaterally symmetical
often with distinct head.
metameric which means they have multiple speciallized segments.
Annelid Cell Type
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.
Epithelium secretes outer transparent moist cuticle.
Body wall with outer circular and inner longitudinal muscle.
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.
Asexual reproduction by fission and fragmentation
Capable of complete regeneration.
Hermaphroditic or separate sexes
larvae are trochophore type
asexual reproduction by budding in some.
spiral cleavage and mosaic development
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.