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Characteristics of Annelida : (Nervous system (double ventral nerve cord…
Characteristics of Annelida :
Unique annelid head and paired epidermal setae (lost in leeches)
Aquatic and terrestrial. Most are free-living, some ectoparasitic and some symbiotic
Triploblastic and well-developed coelom divided by septa (except in leeches)
Nervous system
double ventral nerve cord and pair of ganglia with lateral nerves in each segment
pair of dorsal cerebral ganglia makes up the brain and is attached to ventral nerve cord :
Asexual reproduction – fission and fragmentation; capable of complete regeneration
Bilaterally symmetrical, metameric, often with a distinct head
Coelomic fluids function as hydrostatic skeleton
Outer transparent moist cuticle secreted by epithelium
Complete digestive system, not segmentally arranged
Outer circular and inner longitudinal muscles occur in body wall
Head specialised into differentiated organs: tentacles, palps, eyespots of polychaetes
Sensory system: tactile organs, taste buds, statocysts in some, photoreceptor cells,
eyes with lenses (in some)
Sexes separate or hermaphroditic
Larvae (if present) are of trochophore type
Closed circulatory system: blood vessels and aortic arches (hearts) for pumping
blood in segments
Respiration through skin, gills or parapodia
Pair of nephridia for each segment as excretory system