Chapter 9-Worms (Platyhelminthes, Nematoda, and Annelida) Flashcards
What does it mean to be a bilateral organism?
only one plane of bisection produces left and right mirror-image halves; body is polarized along 2 perpendicular axes: anterior-posterior (head-tail) axis and dorsal-ventral (back-belly) axis
What are the 3 phyla of worms studied in lab and their common names?
Platyhelminthes (flatworms), Nematoda (roundworms), Annelida (segmented worms)
What does it mean to be triploblastic?
have 3 embryonic layers: 1. ectoderm 2. mesoderm 3. endoderm
What does the ectoderm give rise to?
covering of animal
What does the mesoderm give rise to?
forms muscles and most other organs between gut and outer covering
What does the endoderm give rise to?
lining of digestive tract
What does it mean to be acoelomate and what kind of worm exhibits this?
lack internal body cavity, apart from incomplete digestive trace; flatworms
What does it mean to be pseudocoelomate and what kind of worm exhibits this?
body cavity located between mesoderm and endoderm; roundworms
What doe it mean to have a true coelom and what kind of worm exhibits this?
body cavity that develops entirely within the mesodermal layer; annelids
What are animals with a true coelom called?
coelomates or eucoelomates
T/F The presence and configuration of a body cavity was a key innovation in animal body design.
True
T/F A body cavity serves as a hydrostatic skeleton.
True
How is a hydrostatic cavity useful?
muscular contractions to displace fluid within a cavity, therefore exerting force and changing the shape of the cavity
What are some general characteristics of flatworms?
mostly small, dorsoventrally flattened, soft-bodied worms that live in aquatic environments; considered simplest of Bilateria; acoelomate, lack a circulatory system, most are monoecious and exert hermaphroditism, exhibit regeneration
Do flatworms exhibit some form of cephalization?
yes
Are many flatworms parasitic?
yes
What types of flatworms are parasitic?
flukes and tapeworms
Where do Turbellarians live?
marine environments, some inhabit fresh water or moist soils, some prefer sand, mud, or under stones and shells where they scavenge and hunt for small animals
T/F Turbellarians are free-living worms.
True
T/F Turbellarians are not hermaphroditic.
False-most are hermaphroditic
How does reproduction occur in Turbellarians?
copopulation and cross fertilization
What are some characteristics of Dugesia?
acoelomates, found in freshwater habitats, known as planaria, uses a pharynx to eat, head has lateral lobes and light-sensitive eyespots
What is the pharynx?
food sucked up through tube to mouth and leads to a blind gastrovascular cavity with 3 lobes, one anterior and two posterior; muscular organ usually retracted in body but can be everted through mid ventral opening
How do flatworms move?
use cilia on outside surface for movement
What clade/class do Turbellarians belong to?
Turbellaria
What are trematodes also called?
flukes
What are flukes known for doing?
parasitize vertebrates including humans
What are endoparasites?
live inside host
What are ectoparasites?
parasitize surface of host
What important adaptation do endoparasites have?
metabolically active epicuticle resists host’s digestive enzymes and immune defenses
How does a fluke attach to its host?
suckers that are located along midline; the anterior sucker surrounds the mouth
Explain the life cycle of a trematode.
Involves 2 or more hosts: first intermediate host typically a gastropod mollusk (snail), second intermediate host an arthropod or fish, vertebrate is always the final or definitive host
What is the life cycle of a fluke?
zygote > miracidium > sporocyst > redia > cercaria > metacercaria (absent in blood flukes such as Schistosoma) > adult; produce a large amount of eggs
What is the Fasciola hepatic commonly known as?
sheep liver fluke
What does the sheep liver fluke do?
sucks blood, mucus, and cells from infected sheep and cattle, and may infect humans; adult fluke found in bile duct of host, eggs produced and leave host through feces, eggs reach water and hatch and release free swimming ciliated larva (miracidium), finds intermediate host (snail) and penetrated tissues and metamorphoses into saclike sporocyst, inside sporocyst non-ciliated larvae called redia develop asexually, redia grows in snail developing into tadpole cercaria, cercaria emerges and encysts itself as metacercaria on nearby vegetation, encysted metacercaria now infective to definitive host, once ingested, metacercaria will leave its “cyst” in small intestine, migrate to liver, and move to bile duct where it produces eggs and completing life cycle
What is the Opisthorchis (Clonorchis) sinensis called?
oriental liver fluke
How does the oriental liver fluke infect organisms?
live of humans, cats, dogs, and pigs
How do humans become infected from oriental liver fluke?
consumption of raw or undercooked fish that contains encysted metacercariae, cysts dissolve in intestine and young flukes migrate to the liver where they may live for 15-20 years; may cause cirrhosis of liver or death
What is Schistosome commonly called?
human blood fluke
How is schistosomiasis passed?
malaria
Where does the human blood fluke inhabit a human?
intestinal veins and other organs of their host, causing enlargement of the spleen, liver, and bladder, bleeding ulcers and overall nutrient deficiency
What does it mean when a human is the definitive host for a fluke?
contains sexually mature, egg-laying blood flukes
Are the human blood flukes monoecious or dioecious?
dioecious
What is the intermediate host in the human blood fluke cycle?
snail
How do humans get infected?
wading in irrigation ditches, infected from free swimming cercaria that penetrates and burrows in skin
What are some characteristics of Class Cercomeromorpha?
most evolutionarily derived, endoparasites in gut of vertebrates, hang onto inner walls of host’s intestinal tract and absorb nutrients directly through epithelium, lack digestive cavity and digestive enzymes and instead invest heavily in reproductive structures
How are tapeworms bodies divided?
anterior scolex which has hooks and suckers for attachment, narrow neck where growth initiates and a chain of serially repeating segments called proglottids
What do proglottids contain?
contains male and female reproductive organs, when fertilized, break away from worm and leave via host’s feces
Which phylum do roundworms belong to?
Nematoda
What are some characteristics of Phylum Nematoda?
most abundant and diverse animal taxa, most widespread of metazoans, abundant in marine and freshwater benthic habitats, in soil, as parasites in many plant and animal hosts
What are characteristics of the nematode body plan?
elongate, cylindrical and tapered at both ends, body cavity known as pseudocoel which occupies space between body wall musculature and the gut, reproductive organs are suspended within the cavity, “a tube within a tube”, do not have specialized gas exchange surface or a circulatory system; move forward and backward using sinuous, eel-like undulations produced by alternating contractions of dorsal and ventral longitudinal muscles, lack circular muscles and longitudinal muscles are antagonized by the elastic properties of the cuticle
What are characteristics of Turbatrix?
vinegar eel, free-living nematode feeds on bacteria and yeasts in dead organic material, live in acidic environments like unpasteurized vinegar and fermented fruit juices
What are characteristics of Ascaris lumbricoides?
intestinal roundworm that infects humans, spread through feces, can survive and remain infectious for many years, moderate infections can lead to malnutrition while heavy infections may result in intestinal blockages which can be fatal or cause psychological trauma because overcrowded worms start wandering the body, female worms much longer than male worms
What are characteristics of Trichinella spirals?
smallest nematode parasites of humans, rodents and other carnivorous animals, causes trichinosis and lives in host’s intestinal wall is viviparous, and juveniles carried to blood to skeletal muscles where they encyst, cysts can cause pain and stiffness in host, transmission occurs if flesh containing encysted juveniles is ingested
What does viviparous?
live birth; females do not lay eggs
Why is hookworm economically important?
causes anemia in livestock
Where are pinworms found?
intestines of up to 30% of children in US, female pinworms migrate to host’s anus at night to lay eggs and irritate skin around anus
What do filarial worms do?
inhabit lymph glands and other tissues of vertebrates, usually birds and mammals
What is elephantiasis?
intense swelling of connective tissue that result in swelling of legs, arms, breasts, and scrotum
What does heart worm (Dirofilaria) do?
infects heart and pulmonary tissues of dogs, bloodsucking insects like mosquitoes and fleas typically serve as intermediate hosts for filarial worms
What are characteristics of Phylum Annelida?
earthworms and leeches and polychaetes, include parasitic and free-living species, occur in variety of environments ranging from marine to freshwater as well as terrestrial, exhibits segmentation
What is segmentation?
construction of body from series of modular sections
What are advantage of segmentation?
development and function of individual units can be more precisely controlled, creating an opportunity for specialization; different segments possess different combinations of organs or perform different functions relating to reproduction, feeding, locomotion, respiration, and excretion; allows for more improved hydrostatic skeleton because of coelomic cavity which is divided into fluid-filled compartments that can be controlled individually
How do annelids move?
use hydrostatic skeleton, contract circular muscles that lines segment, action squeezes the segment, forcing fluid to squirt outward and extend body, contraction of longitudinal muscles return worm to original form
How are annelids more complex than flatworms or roundworms?
closed circulatory system carries blood form one segment to another, ventral nerve cord connects ganglia in each segment with one another and with the brain allowing for coordination of activities, digestive tract has several regions that are specialized for different functions
What are some characteristics in Class Polychaeta?
polychaetes, marine environments, burrowers, some craw on substrate, many can swim;
What do tubeworms do?
secrete tubes within which they live, thrive adjacent to eep sea hydrothermal sea vents, relying on symbiotic chemoautotrophic bacteria to convert toxic sulfides into useable energy
What is parapodia?
fleshy lateral outgrowths of body wall typically used for locomotion, important for gas exchange
What are setae?
small bristles that project form parapodia which serve to anchor animal during locomotion; used in filter feeding, others filled with poison as defense against predators
T/F Polychaetes exhibit the greatest amount of cephalization.
True
What kinds of annelids are in Class Clitellata?
earthworms and leeches
What subclasses do earthworms and leeches belong to?
Class Oligochaete and Clitellata
What is clitellum?
mucus-secreting structure involved in reproduction; polychaete lack this
What are some characteristics of earthworms?
freshwater worms and some marine species, found worldwide, mainly in moist rich soil which are not too dry or sandy, ingest soil, grind up and digest organic matter and pass remaining in feces, contribute to decomposition of organic matter, aeration and enrichment of soil; oligochaetes have fewer setae than polychaete, lack parapodia, and lack a well differentiated head region
Describe the head region of the Lubmricus worm?
first four segments: mouth found on first segment behind fleshy lobe called prostium
How is food passed in an earthworm?
passes along pharynx to esophagus in segments 6-13 partially hidden by aortic arches and seminal vesicles; crop used for food storage, muscular gizzard for food grinding, intestines for digestion and absorption, anus located on last segment
Describe the closed circulatory system in earthworms.
aortic arches and dorsal blood vessel are contractile with dorsal vessel being chief pumping organ and aortic arches maintaining steady flow of blood into ventral vessel below esophagus
Describe the reproductive structures in earthworms.
hermaphroditic (monoecious), clitellum (series of swollen segments) used in reproduction, sperm produced in seminal vesicles and exits body through male gonopores located on segment 15 on ventral surface, female gonopores fond on segment 14
An earthworm possesses 2 seminal vesicles. which segments are they located on?
9 and 10
How do earthworms mate?
align with heads in opposite directions in a way that seminal receptacle opening faces clitellum of mate, sperm released from male gonopores and travels toward head through seminal grooves in body slime, toward seminal receptacles; worms separate and clitellum produces secretion that hardens around worm, worm draws backwards, forcing tubular secretion towards head, tube picks up eggs from oviducts, sperm from sperm receptacles and finally a nutritious fluid produced by skin glands, tube slides off head and deposited on ground where closes up into a cocoon, fertilization takes place within cocoon, young worms hatch in 2-3 weeks
What are characteristics of Hirudinea?
freshwater and marine, leeches, blood suckers, others feed on invertebrates like insect larvae, snails, and worms, has blade like, chitinous jaws rasp through skin of victim, anticoagulants secrete into wound prevent blood from clotting and powerful muscles suck blood from wound quickly,
What were medicinal leeches used for and why?
blood-letting patients, used in plastic surgery because extract fluid more efficiently and less damage than hypodermic suction
How is segmentation in leeches?
not as obvious, lack internal septa, lack parapodia and setae
How are a leeches body?
dorsoventrally flattened and contain anterior and posterior sucker for capturing and holding prey
How do leeches reproduce?
monoecious and have a clitellum and not obvious except for in reproduction
