Unit 9 - Annelids

Exhibits metamerism, prostomium, trunk segments, pygidium, peritoneum, chaetae.

Repeated units that contain components of several organ systems, function together as whole animal

Prostomium, segmented trunk, pygidium

Is subdivided by septa, lined by a mesothelium called the peritoneum.

chitinous bristles called chaetae, A cuticle of collagen fibers.

Allows for better localized control of hydrostatic pressures created by the body wall muscles.

Flap like appendages on trunk segments that function in locomotion and respiration.

Deposit feeders, direct and indirect, Filter feeders, use a fan of cilliated tentacles, Predatory, use small grasping jaws.

Chloragogen cells surround the gut tube, function like a liver by regulating nutrient levels, eliminating toxins and forming urea.

Some have gills, some exchange across body wall only, some exchange at parapodia.

Closed circulatory system with large dorsal and ventral blood vessels, Larger vessels are contractile in some.

Metanephridia in each segment, Nephrostome in septum drains preceding septum coelom, Blood capillaries surround nephric tubule and alter urine composition.

Both gonochoristic and hermaphroditic, temporary sex organs result from swelling of peritoneum.

Long chains of gamete filled segments break off as a single individual (epitoke) and swim to ocean surface and rupture. The atoke is nonreproductive and remains on the ocean floor.

Brain composed of cephalic ganglia, paired ventral nerve cords connect to paired ganglia in each segment. Unicellular chemo and light receptors most common.

Errantia and Sedentaria

Fairly active, Multicellular eyes, Antennae, large parapodia, pygidial cirri.

Large parapodia with internal supporting chaetae (acicula)

Less active/mobile, Bicellular eyes, no antennae, no pygidial cirri, no or small parapodia

Clam worms, Bristle worms, Fire worms

Leeches, Earthworms, Feather duster worms.