Laboratory 7
Zoology 1121
Phylum Annelida
Quiz
I. Phylum Annelida
1. first time to see segmentation in organism
2. radiated (i.e., spread out) into all habitats
3. external segmentation mirrored in internal segmentation
4. segmentation: serial repetition of body units
5. coelom segmented as well
6. in annelid’s, each external segmentation represents an entire unit
7. Eucoelomate – the body cavity is completely lines with mesoderm,
think conceptually as splits in mesoderm
instead of mesoderm surrounding an endoderm as in pseudocoelomates.
8. First time we see other new systems in this phylum as well
a. Closed circulatory system – specialized body
fluid organs to move it around
- blood is special because it contains respiratory pigments
- r.p.’s are proteins that bind reversibly with oxygen
- r.p.’s increase both
1. the amount of oxygen that can be carried in the blood
2. the efficiency with which gas exchange can occur in the tissues
- wide variety of r.p.’s based in iron carrier complex
1. hemoglobin
2. chlorocruorin
3. hemerythrin
4. mix of 1, 2, or 3
9. Protostomes
- First time this distinction becomes important: based upon order in which
digestive system develops
- In embryonic development, the organisms can either
1. have the mouth develop first, then an anus second
2. have anus develop first, then mouth develops second
II. Annelid Evolution
1. earliest are Class Polychaetes
2. diverged into either terrestrial phylum or “semi-parasitic” phylum
3. more likely we think that there were split between the mollusks
and annelid-arthropods, then a later split
between the annelids and
the arthropods (see 1-4)
III. Phylum Characteristics
1. eucoelomates
2. elongated & segmented body with internal organs also serially
repeated
3. closed circulatory system (i.e., blood flows in vessels)
IV. Class Characteristics
Based on bristles (called setae) on the body
1. Numerous segments with parapodia . . . . . . . . . . . . . .
Class Polychaeta
a. bearing many setae
b. distinct head with eyes and tentacles
c. mostly marine
d. mostly dioecios
2. lack parapodia and a distinct head . . . . . . . . . . . . . . .
. . . . Class Oligochaeta
a. only few setae on each segment
b. clitellum present
c. monoecious
3. Dorsoventral flattening, always composed of 34 segments . . . .
.Class Hirudinea
V. Class Polychaeta
1. common name for clamworn (Nereis), found in mudflats and ocean floor
2. have parapodia that are tipped with setae used for locomotion and
gas exchange
3. mouth tip known as prostomium
with (feeding) tentacles, eyes, and palps followed by a
peristomium
that has 4 tentacle pairs
4. no clitellum
VI. Class Hirudinea
1. common name for semi-parasitic leeches
2. has anterior and posterior sucker – remember flukes just have one
3. find a clitellum
4. monoecious, since rarely encounter mates when attached to a host
VII. Class Oligochaeta
1. Common name earthworms.
2. Hydrostatic skeleton
3. Swollen segment known as a clitellum and functions in reproduction.
4. Head of earthworm has a 1st segment known as the peristomium
that has a slit-like mouth. Has a quasi-lip
called a prostomium
on the peristomium
5. Tube-within-a-tube digestive system runs the entire length. [hence,
complete]
6. Has setae bristle on each segment like the clamworm, but setae are
not on any parapodia.
7. Secreted cuticle on top of the epidermis, no external structures
for gas exchange as well then. (remember,
parapodia involved in gas exchange in clamworm)
8. Gas exchange just across cuticle, must be moist but would drown
in saturated water
9. Lots of pores across cuticle
a. male genital pore
b. female genital pore
c. nephridia pore – for
excretion of waste
d. coelomic pores – keep
it moist [only from seg. 10 on]
10. has septa – divisors between the segments
11. Digestive system
a. Has digestive tract that
begins with mouth then a pumping pharynx, esophagus, crop, gizzard, intestine,
anus
b. pharynx opens up into
the esophagus
c. esophagus
d. crop – storage organ
e. gizzard – has stones
to grind up material
f. intestine – extracellular
digestion occurs here, absorption as well
g. typhlosole – runs along
the intestines to increase the surface area…think of a string
h. anus – undigested and
unabsorbed wastes are egested
12. Nervous system
a. brain – dorsally located
in anterior end (cephalization)
b. 2 large nerves leave
brain to join at subpharyngeal gang
c. subpharyngeal ganglion
–joiner
d. one ventral nerve cord
- leaves the subpharyngeal ganglion and travels entire length
e. there are bulbous areas
of the ventral nerve cord at each segment…this bulbous area is called a
ganglion
13. Reproductive System
a. monoecious – both testes
and ovaries but NO self-fertilization
b. clitellum – secretes
a mucus cocoon and ova towards donated sperm
c. then cocoon matures and
then shed from worm
d. know pathways, page 81
14. Excretory System
a. nephridia – two per segment
b. nephrostome – basically
a ciliated funnel which pulls coelomic fluid into tubule and excrete through
nephridia pore
c. each tubule traverses
two segments
d. Nephrostome and nephridia
pore is separated by septa. Thus, coelomic fluid into nephrostome then
into
next segment where it passes out the pore
e. Highly vascularized for
fluid retention
15. Circulatory system
a. continuous closed system
of tubules containing blood fluid (1st time)
b. dorsal vessels branch
posteriorly on either side of esophagus into 5 hearts
c. hearts – for moving blood
around
d. closed = increased efficiency
of cellular respiration
e. Products directly to
the cells for cell resp.
f. Vessels branch even smaller
to capillaries, which is the direct site of exchange
g. Blood fluid has blood
protein complexes and other cellular elements
h. Three proteins to carry
oxygen…called respiratory pigments
1. Hemoglobin –conserved evolution – annelids and vertebrates
2. Hemocyanin – molluscs and arthropods
3. Chlorocruorin – also found in annelid
16. Longitudinal and circular muscles – for movement
a. P. Platyhelminthes –
both longitudinal and circular (latitudinal)
b. P. Nematoda – only longitudinal
17. Adaptive use of segmentation
-Locomotion is improved
in earthworms compared to nematodes by dividing the hydrostatic skeleton
into
compartments, facilitating peristaltic contractions. Segmentation also
permits the development of segments
into parts that also perform specific functions for the animal.
VIII. Blood Experiment – write paper on this
1. anesthetize live one in 70% ethanol
2. cut up from clitellum
3. blot up coelomic fluid
4. snip heart and use cap tube to draw in blood to measure hemoglobin
5. allosteric changes in respiratory protein
- allosteric – means when
a protein changes it shape, like from a c-shape to a completely round shape
6. different positions confer different absorption of light
7. use spectrophotometer to note changes in how much light was absorbed
by measuring how much light was
transmitted through the
sample
8. the oxygen will cause the allosteric changes
9. we compare to mouse blood (since also contains hemoglobin)
10. add sodium hydrosulphite to de-oxygenate blood
11. graph results
12. must write out answers to questions at bottom on p. 85…use this
in lab report paper you write
IMPORTANT TERMS:
Class Poylchaeta
Class Hirudinea
Class Oligochaeta
parapodium
setae
anterior
sucker
posterior sucker
clitelllum
mouth
anus
setae
cuticle/skin
mouth pharynx
esophagus
crop
gizzard
intestine grain
ventral nerve cord
seminal vesicle, sperm receptacle
testis
ovary
egg funnell
vas deferens
nephridium
dorsal blood vessel
ventral blood vessel
closed circulatory system
hearts
blood
hemoglobin
oxyhemoglobin
red blood cell
spectrophotometer
absorbance spectrum
respiratory pigments
allosteric changes in molecular shape