Bell Ringer Explain the circulatory system of Mollusks
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 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 • Prostomium • Peristomium • Series of Segments • Pygidium • Posterior portion – bearing the anus
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 • Poly=many; chaite=long hair/bristles • Oligochaeta (earthworms) • Oligos=few; chait-long hair/bristles • Hirudinea (leeches)
Class Polychaeta • Largest class • 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 • 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 • 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 • 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 • 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.
"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."