PHYLUM ANNELIDA
SEGMENTED WORMS
TRIPLOBLASTIC
COELOMATE
BILATERAL SYMMETRY
gut
muscle
coelom
Each segment has:
- its own coelom
- its own muscles (longitudinal and circular)
circular
muscle
longitudinal
muscle
coelom
(hydrostatic skeleton)
contract
longitudinal
contract
circular
Setae for anchorage
CLASS POLYCHAETA
BRISTLEWORMS
CLASS OLIGOCHAETA
EARTHWORMS
CLASS HIRUDINEA
LEECHES
CLASS OLIGOCHAETA
- reduced head
- reduced parapodia
Very beneficial:
- aerate soil
- break down detritus
(nutrient cycling)
eg earthworms
CLASS OLIGOCHAETA
- simultaneously hermaphroditic
- ventral surfaces together, opposite directions
- mutual sperm transfer
- clitellum secretes mucous sheath around both worms (holds
them together)
- transfer sperm into other worm’s spermatheca
Later:
- worm secretes cocoon from clitellum
- cocoon moves forwards
- as it passes female gonopore: releases 10-20 eggs (own eggs)
- as it passes spermatheca opening, releases sperm (from other worm)
- carries on forward to head
- front pinches closed as it leaves head
- back pinches closed as it leaves head
- cocoon laid in soil (many cocoons from each mating)
DON’T PANIC!
NERVOUS SYSTEM
CIRCULATION
EXCRETION
SETAE/CHAETAE:
- 8 per segment
- grip on ground & burrow
- grip when mating
CLITELLUM:
- mating
COELOM:
- muscles push against it
- partitioned by septa
NERVOUS SYSTEM
CEREBRAL GANGLION: AROUND PHARYNX
ONE GANGLION PER SEGMENT
VENTRAL NERVE CORD
CIRCULATORY SYSTEM
DORSAL VESSEL (BLOOD MOVES FORWARD)
VENTRAL VESSEL (BLOOD MOVES BACKWARDS)
WRAPPING VESSELS IN EACH SEGMENT
FIVE WRAPPING VESSELS (AROUND OESOPHAGUS) ARE ENLARGED:
HEARTS
DORSAL VESSEL IS MUSCULAR: PUMPS BLOOD FORWARD
HEARTS ARE MUSCULAR: PUMPS BLOOD INTO VENTRAL VESSEL
SMALL BLOOD VESSELS
IN SKIN: RESPIRATION
ACROSS SURFACE
HAEMOGLOBIN:
RED BLOOD
DIGESTIVE SYSTEM
MOUTH – ANUS: GO THROUGH SEPTA
GUT HAS ITS OWN SET OF MUSCLES: PERISTALSIS
TYPHLOSOLE: INDENTATION OF GUT TO INCREASE SURFACE AREA
EXCRETORY SYSTEM
METANEPHRIDIUM
A PAIR IN EACH SEGMENT
FUNNEL (opens to coelom)
CILIATED TUBE (blood vessels reabsorb)
EXTERNAL PORE
CILIATED
TUBE
(cilia move fluid
along tube)
FUNNEL
(opens in segment in front)
EXTERNAL PORE
(waste expelled here)
DON’T PANIC!
CLASS POLYCHAETA
BRISTLEWORMS
CLASS OLIGOCHAETA
EARTHWORMS
CLASS HIRUDINEA
LEECHES
CLASS POLYCHAETA
bristleworms , tube worms, christmas tree worms (mostly marine)
head
parapodia (paddles on each segment)
lots chaetae on parapodia
feathers = respiratory structures
CLASS POLYCHAETA
FIREWORM
Osedax
genus of deep-sea polychaete, called
boneworms, zombie worms, or
bone-eating worms.
CLASS POLYCHAETA
BRISTLEWORMS
CLASS OLIGOCHAETA
EARTHWORMS
CLASS HIRUDINEA
LEECHES
CLASS HIRUDINEA
LEECHES
PARASITIC (suck blood) or PREDATORS (hunt & eat
invertebrates) – most are predators
NO CHAETAE
MOSTLY FRESH WATER
Terrestrial in Oz and New Guinea
Most have ~ 32
segments but looks
like more – annular
rings
PARASITIC SPECIES:
- attach to host, feed, drop off when full
- anterior and posterior suckers
- bladelike jaws to slice skin
- secrete anesthetic & anti-coagulant (“hirudin”)
- sensitisation
Excretory system very efficient at removing
water from blood meal while sucking –
maximises food intake.
PARASITIC SPECIES:
Medicinal: drain blood from injuries or surgery,
dissolve blood clots
Followup to plastic
surgery
Finger reattachment
Annelid Summary
- annelids are SEGMENTED worms
- tribloblastic, coelomate, bilateral symmetry
- longitudinal and circular muscle
- earthworms have a reduced head, setae
- polychetes have parapodia and lots of setae
- gas exchange via diffusion through skin
- excretion via nephridia
PLATYHELMINTHES
ANNELIDA
MOLLUSCA
CNIDARIA
PORIFERA
NEMATODA
ARTHROPODA
ECHINODERMATA
CHORDATA
protostomes
deuterostomes
bilateral
PHYLUM NEMATODA
ROUNDWORMS
VERY Common
Virtually all habitats (even in ice and in hot springs)
PARASITES and FREE LIVING
2% OF HUMANS DON’T HAVE A NEMATODE PARASITE
Rest of world dissolves…. still see structures
(Mountains, rivers, shapes of animals, trees etc)
PHYLUM NEMATODA
Some species very widespread, some very specialised (felt
beermats in two german beerhalls)
90 000 individuals in one rotting apple
1m3 BEACH SAND = 4 MILLION INDIVIDUALS
gut
gastrodermis
DIPLOBLASTIC
ACOELOMATE
no body cavity
PORIFERA
CNIDARIA
epidermis
mesodermis
gut
TRIPLOBLASTIC
ACOELOMATE
no body cavity
gastrodermis
epidermis
mesodermis
pseudocoelom TRIPLOBLASTIC
PSEUDOCOELOMATE
gut
gastrodermis
epidermis
body cavity
btw
gastroderm
& mesoderm
mesodermis
coelom
gut
gastrodermis
body cavity
within
mesoderm
epidermis
TRIPLOBLASTIC
COELOMATE
PLATYHELMINTHES
NEMATODA
ANNELIDA
MOLLUSCA
ARTHROPODA
ECHINODERMATA
CHORDATA
Used to think a pseudocoelom was an
Intermediate between no coelom and a true coelom
Now we think it’s just another way of making a coelom
BILATERAL SYMMETRY
**NON-SEGMENTED**
CUTICLE
- thick, multi-layered, tough
- elastic, flexible
- permeable to gases & water
no respiratory system:
- diffusion through cuticle
HIGH HYDROSTATIC PRESSURE:
HYDROSTATIC SKELETON
ROUND CROSS SECTION (HENCE “ROUNDWORMS”)
LONGITUDINAL MUSCLES ONLY
ANTAGONISM = CUTICLE AND HYDROSTATIC SKELETON
SNAKING, THRASHING MOTION
GUT
PSEUDOCOELOM
CUTICLE
MUSCLE
Nematode muscles are weird
Usually nerve extends to muscle:
Nematode muscles extend to nerves
REPRODUCTION
OVARY
GUT
UTERUS
DIOECIOUS (SEPARATE SEXES)
PARASITIC SPECIES = REPRODUCTIVE
MACHINES
100 000 EGGS A DAY
EUTELY
TWO STRANGE THINGS:
hatches from egg with
finite number of cells
no mitosis in adult
growth = cells enlarge
± 500 cells
excretory system = 2 cells
no regeneration
CRYPTOBIOSIS
adults can suspend life processes
and return to life when
conditions better
in eggs:
can be viable after 10 years
(even when kept in alcohol)
Caenorhabditis elegans
959 cells in female
1031 cells in male
302 neurones
PARASITIC SPECIES:
ascaris
elephantiasis
guinea worm
hook worm
trichinella
plant pathogens
others
Ascaris spp.
- rare in Oz
- no intermediate host
- no free-living larval stage
- gut parasite
- 1.27 billion infected
- adult = 20cm long
- only a problem if lots
(block gut)
PIG
HUMAN
10 YEAR OLD BOY
EGGS VOIDED IN HUMAN FAECES
INGESTED BY NEW HUMAN HOST
HATCH INTO JUVENILE WORMS IN GUT
1
5
THROUGH GUT WALL INTO BLOOD VESSELS
4
MOVE IN BLOOD TO LUNGS
BURROW INTO LUNG ALVIOLI
CRAWL UP TRACHEA INTO MOUTH
SWALLOWED BACK INTO GUT
6
3
STAY IN GUT AND GROW INTO ADULTS
EGGS VOIDED IN FAECES
7
8
9
2
ELEPHANTIASIS
Wuchereria bancrofti
FILARIAL WORM
TRANSMITTED BY MOSQUITOES
LIVE IN LYMPH NODES
CLOG UP NODES & BLOOD VESSELS
TREATMENT:
CHEMICALS TO KILL WORMS
SURGERY TO REMOVE DEAD WORMS
FAILURE OF LYMPHATIC SYSTEM =
SUSCEPTIBLE TO DISEASES
GUINEA WORM – 2 hosts
AFRICA
DRINK WATER
COPEPODS IN WATER
CYST
WASH IT IN RIVER
NEMATODES IN
COPEPODS
IF LEFT UNTREATED:
TREATMENT:
REMOVE WORM VERY SLOWLY
DO NOT BREAK IT
(can’t regenerate: dies: rots)
TWIST OUT SLOWLY OVER WEEKS
BILL FOLEY HAD ONE
Human Hookworm:
Ancylostoma duodenale and Necator americanus
Egg expelled in faeces, hatch and enter new host through skin
Travel through tissues (as per A. lumbricoides) ending up in
small intestine.
Live on blood in small intestine (produce anticoagulant)
Heavy infections cause serious anaemia in 3rd world
Human hookworms infect and harm gorillas.
DOG HOOKWORM - Ancylostoma caninum
DOG ROUNDWORM – Toxocara canis
- gut parasites of dogs
- go through the same circuitous route as Ascaris
In humans, larvae get lost and migrate under the skin leaving
painful red trail
Trichinella spiralis in humans
Not in Oz
- commonly in pigs, but many potential hosts (bear,
wild cats, fox, dog, seal, wolf, walrus)
- infect humans from undercooked pork
- ingested cysts release larvae that mature in small
intestine. Adults lay eggs which hatch and encyst in many
tissues
CAUSE PROBLEMS IF
CYSTS FORM IN HEART OR
BRAIN
PLANT PATHOGENS
KILLS SOYBEAN ROOTS
KILLS LEAVES
ROOT MATS & NODULES
MANY AREN’T eg Loa loa
- transmitted by deerfly
- move under skin, esp cornea
- Produce tiny worms (microfilariae)
which are ingested by deerfly snd
transmitted.
SOME ARE USEFUL TO US
Nematode Summary
-“ROUNDWORMS”
-nematodes are NOT segmented
-VERY common
-tribloblastic, PSEUDOCOLOEMATE, bilateral
symmetry
-tough, flexible cuticle
-longitudinal muscle only – muscles with unusual
structure
-high internal pressure
-gas exchange via diffusion through skin
-carnivores, detritivores, herbivores, parasites……