• marine worms
Segmentation (metameric body plan)
Closed circulatory system, but no heart
Excretion- protonephridia, metanephridia, diffusion or
Respiration- diffusion or gills
Central nervous system- brain and nerve cord
Reproduction- asexual or sexual (many gonochoric)
Sensory system of tactile organs, taste buds,
statocysts, photoreceptor cells, and eyes with lenses.
• Lack parapodia and have few setae
• Lack the distinctive head region of polychaetes
and have no eyes.
• Scavengers that consume soil that contains
• The ingested soil moves into a storage chamber
called the crop, then to an area called the
gizzard, where grinding action breaks down the
soil particles. Undigested material passes out
the anus in a form called castings, which are
prized as soil fertilizer.
• Each segment is also known as a metamere
• Each metamere has a parapodia with
• A mass of ganglia (neural masses) forms an anterior
brain that is usually dorsal to the pharynx.
• They have either a pair of ventral nerve cords
(primitive) or a single ventral nerve cord that runs
the length of the body.
• Each segment has a swelling of the nerve cord
called a segmental ganglion.
• Sensory receptors include: chemoreceptors, touch
receptors, photoreceptors, statocysts and vibration
• Behaviors vary depending on class/life style.
• Most live in fresh bodies of water, but some live
among moist vegetation.
• Suckers found on both ends
• Unlike other annelids, its segments are not
• Leeches lack both setae and parapodia
• Most are predators or scavengers. Very few are
• They secrete anticoagulants, hirudin, to keep
blood from clotting and anesthetic that prevents
the host from feeling their presence.
• Largest group of annelids
• Primarily marine
• Most segments include a pair of
• Well-developed head with eyes
and other sensory structures
• Sand worms,
• Scale worms
• Fire worms
• palolo worms
Hawaii has 11 species
5 are endemic