Bell Ringer

Explain the circulatory system of Mollusks

Annelida

Annelida

Segmented worms ~15,000 species

Including earthworms, freshwater worms, leeches 2/3 of the phylum are marine worms

Clam worms, plumed worms, parchment worms, scaleworms, lugworms, etc

True coelomates

Annelida

Highly developed group Nervous system is more centralized Circulatory system more complex

Sometimes called “bristle worms” Setae – tiny chitinous bristles

help anchor segments during locomotion Aid aquatic forms in swimming Stiff setae prevent worm from being pulled or washed out

of its home

Ecological Relationship/Economic Importance

Distributed worldwide Sea, fresh water, terrestrial soil

Many are predatorsIndirect economic

importance Prey to other organisms Fish bait Earthworms increase drainage

& aeration of soils Help mix the soil & distribute

organic matter Medical uses for leeches

Body Plan

Two-part head Prostomium Peristomium

Series of SegmentsPygidium

Posterior portion – bearing the anus

Prostomium

Body Plan

Coelom serves as a hydrostatic skeleton

Except in leechesAnnelid body has a thin nonchitinous cuticle

surrounding the epidermis epidermis surrounds circular muscles circular muscles surround longitudinal muscles longitudinal muscles surround the coelom

digestive system runs the length of body, perforating each septum longitudinal dorsal and ventral blood vessels and ventral

nerve cord follow the same path

Annelida

Three Classes Polychaeta

Poly=many; chaite=long hair/bristles Oligochaeta (earthworms)

Oligos=few; chait-long hair/bristles Hirudinea (leeches)

Class PolychaetaLargest class

more than 10,000 speciesMostly marineMost between 5 to 10 cm

some less than 1 mm, others greater than 3 mLive under rocks, in coral crevices, in abandon

shells, burrow into sand or mud, or build their own tubes on submerged objects

Class Polychaeta

Differ from other annelids Have a well-differentiated head with specialized sense

organs and paddle-like parapodia on most segmentsPossess many setaeDo not have permanent sex organs, possess

no ducts for their sex cells, and usually have separate sexes Gonads appear as temporary swellings in the

peritoneum & shed their gametes into the coelomSome free-living, active burrowers; some

sedentary living in tubes or burrows

Class Oligochaeta

Over 3,000 species in a variety of habitats Most terrestrial or freshwater forms, some parasitic ,

few marine or brackish waterSetae

Long or short Straight or curved Blunt or needlelike Arranged singly or in bundles

Aquatic forms have longer setae than earthworms

Earthworms

“night crawlers”Burrow in moist, rich soil

Emerge at night to feed on surface vegetation & to breed

Rainy weather – stay near the surface Dry weather may burrow several feet underground

Tropical earthworms 150-250+ segments Grow 3-4 meters in length

Earthworms

Double transport system Coelomic fluid & circulatory system

Food, waste, respiratory gases are carried by both Closed circulatory system

Peristaltic movement contraction of circular muscles lengthen body contraction of longitudinal muscles shorten body http://www.ncsu.edu/scivis/lessons/earthworm/Worm7.

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Digestive System consists of the pharynx, the

esophagus, the crop, the intestine and the gizzard. Food is swallowed by the pharynx passes through the esophagus moves into the crop where it is stored eventually moves into the gizzard

gizzard uses stones that the earthworm eats to grind the food completely

moves into the intestines releasing fluids to aid in the digestion

Earthworms

Circulatory System closed circulatory system circulates blood exclusively through vessels

three main vessels: aortic arches, dorsal blood vessels, and ventral blood vessels. aortic arches function like a human heart. dorsal blood vessels carry blood to the front of the

earthworm’s body. ventral blood vessels carry blood to the back of the

earthworm’s body.

Earthworms

Respiratory System do not have lungs

breathe through their skin by diffusion For diffusion to occur, skin must be kept moist Body fluid and mucous is released to keep its skin

moist. Earthworms therefore, need to be in damp or moist soil.

They have tissue located at the head that is sensitive to light.• tissues enable an earthworm to detect light and not surface

during the daytime where they could be affected by the sun.

Earthworms

Reproduction Earthworms are

hermaphrodites contain both male and

female sex organs Although earthworms

are hermaphrodites, most need a mate to reproduce

Clitellum Secretes mucus to hold

worms together Cocoon

Class Hirudinea

Leeches Over 500 species; predominantly freshwater habitats 2-6 cm in length

Some reach 20 cm Usually flattened dorsoventrally

Class Hirudinea

Form & Function Fixed number of segments

usually 35 Typically have both anterior &

posterior sucker No parapodia, no setae Many live as carnivores,

temporary parasites, permanent parasites

Muscular, protrusible proboscis Tubeluar extension of the oral

region Three jaws armed with teeth

Class Hirudinea

Hermaphroditic but cross-fertilizeClitellum only evident during breeding

season

Medicinal Leeches

used as tools in tissue grafts and reattachment surgery

they secrete anticoagulants to prevent blood clots and relieve pressure due to pooling blood

leech saliva has other therapeutic properties saliva helps reestablish blood flow to reattached body parts

by means of a vasodilator, provides a numbing anesthetic, and lessens the risk of infection due to an antibiotic.

Treating Diabetes

http://videos.howstuffworks.com/discovery/28332-discover-magazine-leech-therapy-video.htm

"I was in Austria doing a cleanse and part of the treatment was leech therapy. These aren't just swamp leeches though - we are talking about highly trained medical leeches."These are not some low-level scavengers - we're talking high-level blood suckers."