Explain the circulatory system of Mollusks Bell Ringer Explain the circulatory system of Mollusks

Annelida

Annelida Segmented worms True coelomates ~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 Sometimes called “bristle worms” 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 predators Indirect 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 Series of Segments Pygidium Prostomium Peristomium Series of Segments Pygidium Posterior portion – bearing the anus

Prostomium

Body Plan Coelom serves as a hydrostatic skeleton Except in leeches Annelid 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 Oligochaeta (earthworms) Poly=many; chaite=long hair/bristles Oligochaeta (earthworms) Oligos=few; chait-long hair/bristles Hirudinea (leeches)

Class Polychaeta Largest class Mostly marine Most between 5 to 10 cm more than 10,000 species Mostly marine Most between 5 to 10 cm some less than 1 mm, others greater than 3 m Live 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 Possess many setae Have a well-differentiated head with specialized sense organs and paddle-like parapodia on most segments Possess many setae Do 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 coelom Some free-living, active burrowers; some sedentary living in tubes or burrows

Class Oligochaeta Over 3,000 species in a variety of habitats Setae Most terrestrial or freshwater forms, some parasitic , few marine or brackish water Setae 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 Peristaltic movement 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.asf

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 Clitellum Cocoon 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-fertilize Clitellum 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.

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http://videos. howstuffworks 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."