Biology lab practical #1 part 2

Phylum Nematoda

• Ascaris– Either male or female

• Female – Longer, fatter, straight• Male – Shorter, thinner, sharp curve at posterior end

– Mouth – At anterior end; three lips– The Anus is at the posterior end– Outer Cuticle– Intestine – Flat, ribbon like-tube that extends straight

from mouth to anus• Food enters through Mouth, goes through Intestine (while

nutrients are absorbed) and leave out Anus

Phylum Nematoda

• One-way; no mix of food and waste

– On inside of Cuticle are opposite each other are two Lateral Lines• Can be hard to see• Join together and terminate at end of excretory pore• Function as osmoregulatory devices

– All other tubes are reproductive structures– Female – Have Y shaped structure at anterior end• Uterus (arms of Y), leading to Vagina (base of Y), and

finally to Genital Pore

Phylum Nematoda– Uterus gradually changes into thin Oviducts and finally into

very fine Ovaries (no destinctions between them)» Eggs are formed in Ovaries

• Travel through Oviducts to Uterus• Leave Uterus through Vagina and exit through

Genital Pore

– Male – Tubes start out thickest near posterior end• Largest tube is Seminal Vesicle attached to Ejaculatory

Duct (where sperm exits)• Following tube away from Seminal Vesicle leads to thin

Ductus Deferens, and tiny Testis

Phylum Nematoda– No surface distinction (besides size) between them– Sperm are formed in Testis, travel through Ductus Deferens to

Seminal Vesicle and leave worm’s body by Ejaculatory Duct

• Curve at posterior end of male serves to grasp female in mating• Two hair-like Spicules near Ejaculatory Duct

– Aid in transferring sperm into Genital Pore of Female

Atlas Ascaris 7.97

Atlas Ascaris 7.98

Atlas Ascaris 7.99

Atlas Ascaris 7.100 & .101

Atlas Ascaris 7.102

Atlas Ascaris 7.103

Ascaris

Ascaris Male

Ascaris Female

Necator 1

Necator 2

Thrichinella Eggs

Atlas Trichinella 7.105

2 is muscle

Phylum Annelida

• Class Polychaeta– Neanthes• Sandworm• Segmentated body• Parapodia – Little flipper-like structures along side of

sandworm– Appendages used in swimming and crawling

• Anterior end has first segment called the Prostomium– Contains its Mouth and small tentacles, eyes, and palps (lip-

like structures)

Phylum Annelida

• Anus - At posterior end of sandworm; end of digestive tract

– The tubeworms secrete a protective outer covering (tube) and live within it• Often only part of tubeworm ever seen is tentacles on

Prostomium that are extruded from tube– Tentacles serve as net to catch food

Phylum Annelida

• Class Oligochaeta– Earthworms

• Inhabitants of underground• Eat dirt (food and plant debris)• Till soil (mixing it and aerating it)

– Clitellum – Wide rather smooth band found towards anterior end• During reproduction Clitellum secretes mucus layer over

Eggs– This mucus layer (with Eggs underneath) slides up and off anterior

end » This creates a Coccoon that shelters the Eggs

Phylum Annelida

– Earthworm’s body is is divided into series of segments • Can be seen externally and internally

– First segment found at anterior end is the Prostomium

– Mouth is found at upper end of Prostomium– Anus is at the posterior end– Cuticle – Non-living layer; composes worm’s surface• Covers body wall that consists of Circular and Longitudinal

Muscles – Allow worm to wiggle its way through soil

• Lighter in color on ventral surface

Phylum Annelida

– Ventral surface is covered with series of bristle-like Setae that aid the worm in motion

– Septae divide segments internally– Each segment has its own Nephridia (excretory system)

• Responsible for maintaining osmoreguation in worm – Too small and delicate to see

• Closely resemble nephron in human kidney

– Coelom – Space between body wall and internal organs– At anterior end of worm are reproductive organs– Three pairs of large white ovals in segments 9-13 are six

Seminal Vesicles• Enclose Testes that produce sperm

Phylum Annelida

• Ductus Deferens carries sperm from Testes to segment 15 where it exits the body• Ovaries are on segment sides of segment 13; tiny,

white, round• Posterior to Ovaries are Egg Funnels

– Narrow down into Oviduct in segment 14» Carries eggs outside worm’s body

• When worms mate their ventral surfaces are contact – Sperm travels through Ductus Deferens and travel in minute

external grooves that lead anteriorly to Seminal Vesicles of other worm

Phylum Annelida» Seminal Vesicles are in segments 9-10» Hold sperm from other worm

• When ready to reproduce, earthworm releases worms from segment 15– Eggs are within Mucus Layer secreted by Clitellum– Will pass seminal receptacles when released and pick up

sperm– Mucus Layer with now fertilized eggs continues to move up

the worm where it eventually reaches the Prostomium– Released from worm as the egg coccoon

Phylum Annelida

– Just posterior to mouth will be very hard and muscular Pharynx• Sucks food into digestive tract

– Beyond Pharynx is long, thin-walled Esophagus• Partially covered by Seminal Vesicles

– Next digestive organ is Crop• Usually dark in color; functions as soft roundish storage bag

for food

– Posterior to crop is a lighter colored round Gizzard• Hard and muscular• Functions to grind up material that the worm ingested

Phylum Annelida

– The Intestine connects the Gizzard to the Anus• Enzymes convert large pieces of food into usable

molecules that can be absorbed by the worm• A fold that hangs down into the lumen (space) of

intestine increases surface area of intestine (called the Typhlosole) • Undigested food waste is eliminated from worm’s body

through Anus

Phylum Annelida

– Ventral Nerve Cord & Ventral Blood Vessel are visible on ventral side of intestine• V.N.C. leads anteriorly to “Brain”

– Small bit of shapeless tissue wrapped around anterior end of Pharynx

– Ventral and Dorsal Blood Vessels lead to anterior end of worm• Here they connect to 5 tubular Hearts (dark in color)

that are wrapped around the Esophagus and function to pump the blood throughout the worm’s body

Phylum Annelida

• Class Hirudinea– Leeches

• Flattened worm-like animals that have an anterior and posterior sucker– Used to attach the leech to their host

• Have a mouth containing chitinous teeth that scrape the skin of their hosts allowing the leech to feed on the host’s blood– Inject anesthetic (numbing agent) and anticoagulant (stops blood

clotting) to feed unnoticed

– Have been used for bloodletting (rid people of bad blood)

Atlas Earthworm 7.87



Atlas Earthworm 7.90 & 7.91

Atlas Earthworm 7.92 & 7.93


Lumbricus (1)

Lumbricus (2)

Earthworm (Segmented Worm) Lumbricus

Earthworm Model (1)

Earthworm Model (2)

Atlas Leech 7.95

Atlas Leech 7.96

Leech

Atlas Nereis 7.83

Atlas Nereis 7.84

Nereis

Selected Human Parasites

• Parasite – Organism that feeds on its living host, sometimes rendering harm but usually not causing the host’s death

• Definitive Host – Where the sexually mature (adult) parasite lives

• Alternate Host – Where the larval stages of the parasite live


• Phylum Platyhelminthes– Clonorchis/Opisthorchis


• Adult liver fluke attaches to human bile ducts and feeds on lining• Eggs shed into bile, transport through digestive tract

(DT), exit through fecal matter• Fecal matter travels into bodies of fresh water• Snails (A.H.) eat eggs

– Eggs develop and swimming life stage is released into water where it burrows into muscles of fish (encysts)

• Humans eat improperly cooked fish and liberate the encysted parasite


• Parasite migrates through DT until it finds bile duct– Here it attaches, feeds, and reproduces

• Avg human infested with 20-200 flukes per person– Can cause liver damage


– Fasciola


• Sheep liver fluke • Life cycle similar to Chlonorchis• Snails release swimming life stage into water where it

encysts on aquatic vegetation– Can also encyst in open water without burrowing into

something

• Humans ingest infested vegetation or water – Acquire parasite


– Schistosoma Mansoni


• Blood fluke Adults live in portal veins of large intestines• Eggs released into large intestine; shed in feces

– Hatch in water and swimming larvae penetrate tissue of fresh water snails

• Snails release other stage of swimming larvae into water• Humans in infested water are targeted by the larvae

– They burrow through skin into a vessel– They then circulate into the blood stream until reach veins in

large intestine» There they settle and begin feeding

• Damage caused predominantly by eggs that don’t make it from the vein into the large intestine


• These eggs circulate in vessels – Eventually become lodged in organs

» Treated as foreign bodies and isolated by scar tissue» This scar tissue inhibits proper organ function


• Taenia


• Tapeworms• Adults live attached to intestinal wall

– Absorb nutrients rom food across their surface

• Mature Proglottid shed with feces• Cows, pigs, or fish eat Proglottids

– Eggs then are released into animal’s DT– There eggs develop into mature larvae and encyst in animal’s

muscles


• Humans acquire by eating poorly cooked meat– Cooking meat to temperature of 56 C or more OR freezing to -

5 C for at least 1 week kills encysted larvae

• Damage to humans from adult parasite includes loss of energy, cramps, and diarrhea• Severe medical conditions ensue when humans ingest

Proglottids (usually from pigs)– Eggs then encyst in human tissues

» Results in scarring that hinders proper organ function» Scarring is permanent and untreatable


• Ascaris– Pig roundworm– Adults live in intestine

• Absorb food that passes through the intestines

– Eggs are passed out of body with feces• Can be ingested by eating dirty object• Hatch in intestine and larvae migrate through intestinal wall

to vein• Vein will carry larvae to lungs• Larvae burrow out of burrow and climb up bronchi to

trachae to epiglottis where swallowed


• Larvae reaches intestine and becomes adult and feeds– Can cross placenta and infect fetus

• Damage from heavy build up of worms in intestine, also migration of larvae (lung infections & bleeding)


• Enterobius– Pinworm– Adults live in colon; migrate to anus to mate & lay

eggs• Males die after mating; females after egg laying

– Eggs cause anus to itch

• Scratching gets them on hands; high chance of reinfection

– Damage is sleeping problems; intestinal discomfort


• Necator– Hookworm– Adults live in intestines feeding blood– Eggs shed in fetus– Larvae survive in soil for several weeks• Infect human by burrowing into human skin (feet)

– Migrate to blood vessel, carried to lungs, crawl up trachae and swallowed into digestive tract


• Trichinella– Circumboreal; humans are a dead road for this

parasite– Adults live in intestines• Males die after mating; females after egg laying

– Eggs give rise to larvae that migrate through circulatory system; settle and encyst in skeletal muscle

– Humans acquire from uncooked meat

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Biology lab practical #1 part 2