Zoology Lab Annelids
Zoology Lab Annelids Bio 106-016
Kutztown University of Pennsylvania
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This 6 page Class Notes was uploaded by Dallas Bowe on Thursday March 3, 2016. The Class Notes belongs to Bio 106-016 at Kutztown University of Pennsylvania taught by Dr. Nancy Butler in Spring 2016. Since its upload, it has received 27 views. For similar materials see Zoology Lab in Biology at Kutztown University of Pennsylvania.
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Date Created: 03/03/16
Zoology Lab Chapter 11 - Annelids Kingdom: Animalia Phylum: Annelida (“segmented worm”) Habitat: o Marine, freshwater, or moist terrestrial locations Level of organization: o organ system Symmetry: o Bilateral Size: o <1 mm to > 3 m Body : o Segmented body wall/coelom o Segmented repetition with organs and body parts o Fluid within segments creates a hydrostatic skeleton Skeleton provides a rigid structure against muscle contraction Complete digestive system Closed circulatory system o Includes: multiple pumping blood vessels, arteries, veins, and capillaries Simple nervous system o Dorsal brain with 2 lobes o Ventral nervous cord No respiratory system o Diffusion across epidermal surface Coelomates triploblastic Protostomes Hermaphroditic o Do not selffertilize o 2 worms exchange sperm through crossfertilization of each other’s eggs Advantages of segmentation: facilitates locomotion Provides repeated elements that may be modified in different ways to perform specialized functions relating to reproduction, feeding, locomotion, respiration or excretion Setae small hairlike bristles used for locomotion Class and Representative Characteristics Animals Polychaeta Paired, external parapodia with multiple setae present on (~ 10,00 species) segments; welldifferentiated head with specialized sense Sandworms, clamworms, organs; no clitellum; mostly dioecious; marine tubeworms, fanworms, scaleworms, lugworms Oligochaeta Lack parapodia and a distinct head; few setae per segment; (~3,000 species) clitellum present; monoecious; mostly freshwater and Earthworms, angleworms, terrestrial blackworms Hirudinea Flattened body with 3334 segments; clitellum present (during (~ 500 species) breeding season); lack setae; lack parapodia; anterior and Leeches posterior suckers present; monoecious; marine, freshwater and terrestrial Sandworms Kingdom: Animalia Phylum: Annelida Class: Polychaeta Marine segmented worms o Includes: sandworms, fanworms, scalworms, lugworms, and tubeworms Have parapodia (setae project from side flaps) o Can be modified to adapt to different habitats and lifestyles Species in rocky environments leglike parapodia for walking Burrowing species digging paddle parapodia Other species short parapodia combine with peristaltic contractions to move the worm body through mud Parapodia also are filled with blood vessels which allow gas exchange by increasing the surface area for diffusion of oxygen and carbon dioxide Welldeveloped head with specialized sense organs Feeding: o Suspension feeding: the process of stationary polychaetes using feathery feeding tentacles to filter plankton and other suspended food particles from the water. Polychaetes build temporary burrows or permanent tubes of mud and mucous secretions to lead this feeding lifestyle. o Detritus feeding: the process of eating organic material that settles on the surface of muddy substrates o Freeliving predators swim and scurry about in search of prey Kingdom: Animalia Phylum: Annelida Class: Polychaeta Genus: Nereis (sandworm) Hide under rocks or in burrows during the day and emerge at night to search for food Locomotion: o Slow crawling achieved by parapodia o Rapid crawling and swimming achieved by undulation Feeding: o Predator Thrusts out its proboscis from the mouth with its piercing jaws and grabs a hold of the prey Earthworms Kingdom: Animalia Phylum: Annelida Class: Oligochaeta Habitat: freshwater or damp soil Lack parapodia Rely on epithelial surface for gas exchange (diffusion) Possess short, bristly setae on each segment Burrowing lifestyle Kingdom: Animalia Phylum: Annelida Class: Oligochaeta Genus: Lumbricus Reproduction: o Each vas deferens releases sperm and seminal receptacles simultaneously receive sperm from another earthworm during copulation Complete digestive system advantages o Food moves in one direction Soil is pulled into mouth by pharynx Soil goes through the esophagus and empties into the crop for temporary storage Crop empties into gizzard to breakdown soil and separate organic matter Passes through intestine for extracellular digestion and absorption of particles in bloodstream The efficiency of the intestine is improved by increased absorptive surface area created by typhlosole (inward fold of the intestinal wall) Undigested particles are released through the anus Closed circulatory system o Blood contains hemoglobin that is directly dissolved into the blood plasma o Presence of oxygen increases circulatory efficiency and allows annelids to live in ocean floor and soil of terrestrial environments where there is an abundance of food and little oxygen o Blood is circulated through 5 pumping vessels o No heart o Blood passes anteriorly through the dorsal blood vessel into the 5 pumping vessels. It is then sent to the ventral blood vessel to the brain and other body parts. Excretion: o Carried out by nephridia At one end there is a nephrostome to pull metabolic waste into the bladder section of the tube Wastes passes through nephridiopores on the outer body wall Coelomic fluids is reabsorbed back into the body cavity Nervous system: o Dorsal brain with 2 small lobes at anterior end o Ventral nerve cord No respiratory structures o Carbon dioxide and oxygen diffuse across dermal surface into and out of the dorsal and ventral blood vessels Reproduction: o Monoecious (hermaphroditic) o Mating occurs outside their burrows at night in warm, moist weather. 2 worms align along their ventral surfaces, with heads positioned at opposite directions. Each clitellum secretes a slimy mucous, forming a cocoon. Cocoon slide forward on worm, collecting eggs from the egg sac Sperm discharges simultaneously and travels in the seminal receptacles Cocoon with fertilized eggs slip on the anterior end of the worm and is deposited by the entrance of the worm’s burrow Eggs develop for 23 weeks and then new worms emerge Internal Anatomy of Lumbricus (earthworms) Structure Function Mouth Ingests soil Pharynx Muscular region of digestive system specialized for pumping in soil Esophagus Passageway between pharynx and crop Crop Thinwalled chamber where food is temporarily stored Gizzard Thickwalled, muscular chamber where soil is mechanically ground and usable organic materials are separated from ingestible materials Intestine Long tube occupying the majority of the body in which nutrients are absorbed into the bloodstream Pumping vessels Specialized, muscular branches of the dorsal blood vessel that (“hearts”) rhythmically contract to circulate blood throughout the body Dorsal blood Longitudinal blood vessel that returns blood to the pumping vessels vessel Ventral blood Longitudinal blood vessel that distributes blood posteriorly to the body vessel Seminal vesicles Creamcolored, lobed organs fastened ventrally, but extending dorsally around each side of the esophagus that store maturing sperm Testes (not Site of sperm production visible) Seminal Ventrally located organs that receive sperm during copulation and store receptacles sperm until needed to fertilize eggs in cocoon Ovaries Site of egg production Nephridia Paired, excretory organs found along the lateral margins of all but the most anterior and posterior segments; they release waste fluids out of the worm through small pores in the body wall Septa Thin, fleshy partitions between segments Brain Small, bilobed structure lying dorsal to the pharynx in segments 3 and 4; houses the majority of neutral ganglia in the worm Ventral nerve Long, white “cord” located along the ventral surface of the body; contains cord large swellings of ganglia in each segment that handle the majority of coordination without intervention of the brain Prostomium An adaptation to keep dirt out of the mouth while burrowing Clitellum A large band covering several segments about ⅓ of the way down the body from the head Used during reproduction for transferring sperm between individuals and in secreting a cocoon that contains the fertilized egg Anus The opening through which indigestible products are released from the digestive tract Nephrostome A ciliated funnel that pulls coelomic fluid containing metabolic wastes into the bladder section of the tube (excretory feature) Nephridiopores Microscopic pores on the outer body wall (excretory feature) Leeches Kingdom: Animalia Phylum: Annelida Class: Hirudinea Genus: Hirudo Freshwater Scavengers or prey on small, aquatic animals Ectoparasites o Can consume 5 10x its original body weight in blood and body fluids o Able to extract fluid more efficiently and with less tissue damage than other methods of suctioning Locomotion: o Swimming or looping Lack setae and parapodia External rings do not correspond to the pattern of internal segmentation Hermaphroditic o Clitellum is only visible during breeding season Have suckers o For feeding and attaching to hosts Blackworm Kingdom: Animalia Phylum: Annelida Class: Oligochaeta Genus: Lumbricus Habitat: o shallow marine ponds, marshes, and lakes in North America Size: o >2 inches Small and free living Closed circulatory system o Dorsal blood vessel contractile and circulates blood o Ventral blood vessel not contractile Head is forages for vegetation and microorganisms while tail projects upward and bends at a right angle to break the surface tension of the water
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