Transcript A- Subclass Oligochaeta General Characteristics

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1- Annelids are segmented worms
2- Annelids are diploblastic
3- Annelids have radial symmetry
4- Annelids just marine animals
5- Annelids use gills in respiration
6- Skin is highly vascularized and must stay moist
7- Segmentation is the subdivision of the body into segments
8- Embryonic segmentation have harmful affect on Annelids
9- Each segment may develop a more or less complete set of young organ
systems
10- Segmentation is benefit for locomotion
11- In radial symmetry the parts of the body are arranged around a lateral
axis
12- In bilateral symmetry the body has a right and left half that are mirror
images of each other
13- Symmetry allows different organs to be located in one part of the body 1
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14- Special muscles attached to setae to move setae
15- In polychaetes, oblique muscle groups run into the parapodia for
movement
16- Cellular epidermis secretes a cells
17- Cellular epidermis are thickened, non-living transparent cuticle
18- Coelom is not fluid-filled space
19- All organ systems are metameric
20- Nervous System consists of a brain at just .
21- leeches have an anterior brain of two pairs of fused ganglia and a
posterior brain of seven pairs of fused ganglia .
22- Circulatory System closed system
23- Blood contains respiratory pigments including oxygen
24- Blood with red cells as O2-carrying molecule
25- Gas exchange by simple diffusion
26- Parapodia in polychaetes act as gills
27- Specialized gills seen in arthropods
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28- Complete digestive system
29- Crop for digest, Gizzard for grinding
30- Typhlosole with increase surface area for digestion in oligochaetes
31- In tube worm polychaetes, specialized capillary arms or radioles use
ciliary action
32- Mucus to trap food particles of a digestible size
33- leeches are parasitic
34- Terrestrial leeches feed on arthropods
35- Ameobocytes found in crop
36- Aquatic annelids secrete urea .
37- Terrestrial oligochaetes secrete high toxic urea .
38- Osmoregulation occurs via the body surface and the nephridia .
39- Monoecious in polychaetes and leeches with internal fertilization and
direct development
40- Dioecious (in polychaetes with external fertilization and formation of a
trochophore larva .
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41- Asexual = most less organized animals capable of complete
regeneration.
42- Annelids are hermaphrodites - with fertilization
43- Clitellum is a special region at the anterior of the worm
44- Clitellum secretes a mucus cocoon,
45- Clitellum makes protective coat around eggs
46- Diochophore is typical larval stage
47- Annelida have Hirudinea Oligochaetes Uniychaeta
48-Segmented inside and out
49- Parapodia used in feeding with many large number of chitinous
bristles setae
50- Polychaetes have distinct head with eyes palps, and tentacles have
clitellum separate sexes trochophore larva usually absent mostly fresh
water.
51- Polychaetes have prostomium is well equipped with sensory and
feeding structures
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Answer in 30 minutes
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52- Polychaetes are bristle worms mostly marine
53- Many are active predators, while others are filter feeders
54- Many crawl on or burrow in the seafloor.
55- A few drift and swim in the plankton.
56- Polychaetes include carnivores, scavengers, and planktivores.
57- Esophagus is located just below the prostomium, but in front of the
modified segments – peristomium
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Syllabus
•Introduction
•Phylum: Annelida (General charactes)
•Nereis
•Allolobophra caliginosa
•Hirudo medicinalis
•Phylum: Arthropoda (General charactes)
•Astacus fluviatulis & Neptunus pelagious
•Daphnia, Cyclops, Balanus
•Scolopendra morsitans, Lycosa ferox
•Phylum: Mollusca (General characters)
•Acanthochiton spinigira, Helix pomatia
•Loligo peadlii, Anodonta sp.
•Phylum: Echinodermata (General characters)
•Astropecten sp.
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Aims

What do you know about

What do you know about Oligochaeta ?

What do you know about Hirudinae ?
8
9
Clitellata
General Characteristics
1.
Pronounced reproductive
structure (clitellum).
2.
Permanent gonads
3.
Hermaphrodites ... each individual
is male & female
10
A- Subclass Oligochaeta
General Characteristics

Earthworms, night crawlers and their
allies
 Most are terrestrial :
organisms that
extract nutrient material from soil
Important as organisms that
condition and aerate soil
 Biodiversity:
~6000 described
species
 Distribution:
freshwater >marine
 Life-style:
Free-living, burrowers
(few epibenthic or tube dwellers).
Detritivores.
 Ecological & economic significance:
Bioturbation, Prey, Bait
 Small (1 cm) to large (3 meters giant Australian earthworm) in size
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A- Subclass Oligochaeta
General Characteristics
•
•
•
Many of the morphological structures are reduced
when compared to the polychaetes
Prostomium :
lacks sensory structures
Parapodia are absent;
each segment usually
contains one or more pairs of setae;
used in locomotion
•
•
Aquatic forms :
usually have larger setae than
the terrestrial forms
•
Obvious metamerism (segmentation)
•
•Coelom :
separated by septa (but gut is
continuous)
•
•Segments:
fused to form clitellum
12
A- Subclass Oligochaeta
General Characteristics
Body wall:
It is covered by a thin
cuticle ,perforated by
minute pores of epidermal
glands.
 Below the cuticle is the
epidermis which is formed
of a single layer of
columnar cells and contains
unicellular glands .
 These are mucous
secreting goblet cells as
well as albumen cells.

13
A- Subclass Oligochaeta
General Characteristics
•
Body muscles:
Circular and longitudinal muscles
•
Setal muscles:
Protractor and retractor muscles
14
A- Subclass Oligochaeta
General Characteristics
15
A- Subclass Oligochaeta
General Characteristics
Locomotion
Peristaltic contractions of circular
muscles
•Longitudinal muscles shorten and
flatten segments
Protractor and retractor muscles
extend and withdraw
16
A- Subclass Oligochaeta
General Characteristics
The method of locomotion
In the posterior segments:
The contraction of the setal
muscles brings the seta outside
and pushes it into the soil.
In the anterior segments:
The contraction of the second
group of the muscles causes the
withdrawal of the setae into their
sacs.
In the posterior segments:
The setae are withdrawn
and the segments become free by
the contraction of the second
group of the setal muscles.
- In the meantime:
The contraction of the circular
muscles of the body tends
the body elongated and thus the
animal moves interiorly.
The setal muscles of the anterior
region:
Contract thus fixing the setae in
the coil to maintain the progress
of the animal
17
A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
1-Digestive
system
2-Respiratory
system
3-Circulatory
System
4-Nervous
System
5Reproduction
6-Excretory
System
18
A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
1-Digestive system
1)Mouth :
mouth cavity buccal pouch in segments 1 to 3
2)PHARYNX (sucking pump) :
a thick muscular pharynx lying in somites 4 to 5
3) OESOPHAGUS:
a narrow straight which extends through somites 6 to 14
4)Crop (food storage) :
a then walled enlargement in somites 15 to 16
5)GIZZARD (grinding) :
a thin muscular walled gizzard in somites 17 to 18
6)INTESTINE (absorption) :
a thin walled intestine extending from somite 19 to the
aperture its dorsal wall is infolded the typhlosole.
19
A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
1-Digestive system
Note
(important)
1- Chloragogen cells for glycogen
and fat synthesis
•3- Earthworms feed on vast quantities
of soil that contains living and decaying
organic material.
•4- An earthworm ingests its weight
in soil every 24-hr
•2- calciferous glands (accessory glands that
excrete excess calcium from the food) lie at the
sides of the esophagus in segments (10 to 12 )
they produce calcium carbonate which they
excrete into the digestive tract .
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A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
1-Digestive system
• 1-In the
pharynx:
It then
passes
through the
esophagus
to the crop
where it is
stopped
temporarily
• 4-The
food into
intestine
• 2-In the
mean
time
The food
receives a
secretion from
the pharyngeal
glands
The secretion
from calciferous
glands in the
esophageal
walls is added
neutralizing the
acids
The digestion
and absorption
takes place
The food is
broken up into
minute
fragments
3-The •
gizzard
21
A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
1-Digestive system
Note
Solid particles such as
grains of sand which are
frequently swallowed
probably aid in this grinding
process
22
A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
2- Respiratory system

Lack respiratory organs; gas exchanges occurs
across the body wall
23
A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
3- Circulatory System



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
1- The blood is bright red due to the
presence of haemoglobin in plasma
.
2- The main blood vessels extend
adjacent to the alimentary canal.
3- Dorsal to it runs adorsl blood
vessel witch Is wide and contractile.
4- It contains valves in each
segment and the blood passes
through it from backward forwards .
5- An other main blood vessel, but
narrower and no valves although
contractile, runs ventral to the
alimentary canal.
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A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
3- Circulatory System




6- Both the dorsal and ventral
blood vessels are connected to
the alimentary canal by
mesenteries
7- In addition to these vessels ,
Other transverse commissures
run round from the dorsal
vessel to the ventral .
8- subneural vessels giving off
branches in their course.
8- There is asubneural blood
vessel extending below the
nerve cord.
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A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
3- Circulatory System
Note
Pseudo hearts :
Six dorso-ventera commissures
lying in segment from (6 to 11)
are dilated and pulsate
rhithmically driving the blood
through a system of vessels
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A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
3- Circulatory System
1- The blood is oxygmated in peripheral
vessels running through the body wall
 2- The blood passes from body wall to
A - the transverse commissures,
B - the dorsal vessel and
C - the pseudo hearts .
 3 - These pump the blood to the ventral
and subneural vessels and then to the
different organs of the body.

4- Removal of the excretory substance
occurs in the nephridial vessels
supplying the nephridia from the ventral
blood vessel.

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A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
3- Circulatory System
 The
answer :
1.
Anus
2.
Dorso-subneural
vessel
3.
Intestine
4.
Dorsal vessel
5.
Hearts (aortic
arches)
6.
Mouth
7.
Ventral vessel
8.
Subneural vessel
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A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
4 - Nervous System
1- the brain consists of bilobed suprapharyngeal ganglia and bilobed sub
pharyngeal .
 2- Each of them jointed with another
by circum pharyngeal commissure
which pass around the pharynx.
 3- Nervous system much like
Polychaetes
 4- BUT ... sensory organs less
developed

3. Cerebral ganglion
6. Nerve collar
7. Segmental ganglion
10. Segmental nerve
13. Ventral nerve cord
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A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
4 - Nervous System
comparison
Place
Function
suprapharyngeal sub pharyngeal
Over the pharynx
Below the pharynx
1- gives nerves to the
sensitive anterior
segments .
2- considered to be
centers for touch ,light
and smell
1- extends backward a
double ventral nerve cord
to the posterior one of
the body .
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A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
4 - Nervous System
Note
In each segment there is a slight
swelling of the cord which may be
referred to as a nerve ganglion from
the fifth segment to the end of the
body each of these ganglia has pairs
of segmental nerves ( two of them
branching posteriorly and the last
pair interiorly .
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A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
5- Excretory system
Figure 17.14
32
A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
5- Excretory system
These consists of:
1- The nephridia :
which arises as ectodermal
invaginations and arranged
metamerically, a pair in each
segment except for the
anterior three segments and last
one.
2- The nephridium:
is covered with a peritoneal
layer ( the nephridial
peritoneum).
33
A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
5- Excretory system
Description
*It starts with a ciliated funnel known as the
nephrostome which lies at the posterior
aspect of the segment.
*From the nephrostome extends a narrow
short tube which penetrates through the
intersegmental septum and passes to the
succeeding segment where it winds on
itself about three times and eventually
runs ventrally where it opens by the
nephridiopore near the ventral pair of
setae .
34
A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
5- Excretory system
*Thus each nephridium actually extends
•
in two segments where the nephrostome
projects in the coelomic cavity of the
segment in front of the segment which
contains the main part of the nephridium
and the nephridiopore.
*The uriniferous tubule is surrounded •
with a network of blood capillaries from
which it extracts the waste products and
these are eliminated outside the body
under the ciliary action of uriniferous
tubule.
*Just before its opening, the uriniferous •
tubule dilates into a bladder or reservoir
which is not ciliated internally.
35
A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
5- Excretory system
Note
The nitrogenous wastes contain
urea and ammonia.
Chlorogogen cells, which belong to the coelomic
epithelium of the intestines are important in
removing excretory material from blood. They
break off from the alimentary canal and discharge
into the coelomic fluid as vacuoles. They either
removed through the nephridiopore or taken up
by Ameobocytes which are then deposited in the
body wall in the form of cuticle.
36
A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
6- Reproduction
Figure 17.17
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A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
6- Reproduction

Hermaphroditic, but exchange sperm during copulation
During copulation, worms join their anterior ends; held together by
mucous secretions from a clitellum
After reciprocal copulation, sperm is stored in seminal receptacles

Clitellum then secretes a mucous tube that serves as a cocoon

The cocoon moves interiorly and eggs from the oviduct and sperm
from the seminal receptacles are poured into it; fertilization occurs in
the cocoon



Cocoon eventually slips off the anterior end of the worm

In time, young worms emerge from the cocoon
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A- Subclass Oligochaeta
General Characteristics
Systems of Oligochaeta
6- Reproduction
39
B - Subclass Hirudinae
General Characteristics

Segments obscured by annulations

•No setae

•Fixed number of segments (33)

•Anterior and posterior segments
fused to form suckers

•Dorso-ventrally flattened

•No obvious parapodia
40
B - Subclass Hirudinae
General Characteristics
•
Anterior segments are
modified as a small sucker
which surrounds the mouth;
posterior segments form a
larger sucker
•
Evidence of segmentation
externally, but no internal
septa
•
There is serial repetition of
many of the organs (e.g.,
nephridia and testes
41
B - Subclass Hirudinae
General Characteristics
•
•
•
•
Most leeches are active
predators; however, some are
the parasitic , bloodsucking
forms.
Blood suckers have blade
like jaws that they use to
penetrate the skin of a host.
Blood is prevented from
clotting because they secrete
a powerful anticoagulant;
anesthetics are also released
A muscular pharynx
subsequently pumps blood
into the gut.
42
B - Subclass Hirudinae
General Characteristics
•
Leeches are hermaphroditic but
engage in cross-fertilization;
some use hypodermic
impregnation
•
Leeches have a clitellum and
are capable of generating a
cocoon
43
B - Subclass Hirudinae
General Characteristics
The body wall:



1- The body is covered
externally by a thin
cuticle.
2- Beneath it is the
epidermis, separated
externally by spaces in
which blood capillaries
run.
3- The spaces between
epidermis and enteric
canal is filled with
botryoidal tissue
consisting of large cells
loaded with pigment.
44
B - Subclass Hirudinae
General Characteristics
The coelom



1- it is usually small because of
the development of the
botryoidal tissue.
2- Botryoidal tissue is
homologous to the chloragogen
tissue of the oligochaetes.
3- sinuses are is the spaces in
the body which are not filled up
by this tissue.
Note:
In many
species
contain a fluid
very much like
true blood,
reduction of
the blood
circulatory
system with
the
assumption of
such of its
function by
the coelomic
spaces has
been a general
trend of leech
specialization.
45
B - Subclass Hirudinae
General Characteristics
Locomotion:




1- Hirudo swims freely by dorsoventral undulation of its body .
2- Walks by looping .
3- Alternatively attaching and
releasing the anterior and
posterior suckers .
4- Bending the body like the
Hydra.
46
B - Subclass Hirudinae
General Characteristics
Systems of Hirudinae
1-Digestive
system
2- Respiration
system
6- Nervous
system
3-Circulatory
system
5Reproductive
system
47
B - Subclass Hirudinae
General Characteristics
Systems of Hirudinae
1-Digestive system
1- It is fitted for the digestion of the blood of
vertebrates (principal food of some
leeches ).
2- the mouth lies in the anterior sucker
provided with :
A- three jaws armed .
B- chitinous teeth for biting.
C- salivary glands

3-main feeding anatomies

–Jaws

–Pharyngeal proboscis
448
B - Subclass Hirudinae
General Characteristics
Systems of Hirudinae
1-Digestive system
Method





1- the blood flow caused by the bite
2- In this time difficult to stop since a
secretion from glands opening near the
jaws prevents coagulations .
3- Blood is sucked up by the dilation of the
muscular pharynx.
4- The short esophagus leads from the
pharynx in to the crop (which has 11 pairs
of lateral branches).
5- Here the blood is stored until digestive .
49
B - Subclass Hirudinae
General Characteristics
Systems of Hirudinae
1-Digestive system


6-The intestine leads from the crop
and stomach to the rectum which the
anus on the dorsal surface of the
posterior sucker.
7- the absorbed food passes into the
blood vessel and the coelomic
cavities , and is carried to all parts of
the body.
50
B - Subclass Hirudinae
General Characteristics
Systems of Hirudinae
1-Digestive system
Note
1- A Leech is able to ingest
three times its own weight in
blood
2-It may take as long as 9
months to digest this
amount.
51
B - Subclass Hirudinae
General Characteristics
Systems of Hirudinae
2- Respiration system
1-It is carried on at the surface of the
body.
2-Oxygen being taken into and 
carbon dioxide given off by many
capillaries in the skin.
3-Waste products are extracted from
the blood and coelomic fluid by
seventeen pairs of nephridia which
resemble those of the earthworm but
lack the internal opening.


52
B - Subclass Hirudinae
General Characteristics
Systems of Hirudinae
3-Circulatory system
The blood containing spaces
are of two kinds: .
A- Blood vessels :
Blood vessels: proper
having muscular walls
B- Blood sinuses :
Blood sinuses: the walls
of which are not
muscular
1-The main blood vessels are
lateral in position and
unite with one another at
the anterior and posterior
ends of the body.
53
B - Subclass Hirudinae
General Characteristics
Systems of Hirudinae
3- Circulatory system
2-They send off branches both
dorsally and ventrally
which break up into
capillaries in the
integument and nephridia.
3-The two principal siruses are
respectively dorsal and
ventral.
4-The latter encloses the nerve
cord .The two sinuses are
connected posteriorly and
are also branching and
their branches reach the
skin
.
54
B - Subclass Hirudinae
General Characteristics
Systems of Hirudinae
4- Nervous system
1-There is a small brain above the pharynx.
2- It connected by two ciricum pharyngeal
commissures with the ventral nerve cord.
3-The ventral nerve cord consists of 23 ganglia,
situated in the middle of each segment.
4-The first or the sub pharyngeal ganglion is
larger than the other and made of 5 united
pairs of embryo ganglia.
5-The last ganglion is also made up of 6 united
pairs of ganglia distinct in the embryo.
55
B - Subclass Hirudinae
General Characteristics
Systems of Hirudinae
5- Reproductive system
1.-All hermaphrodite.
2-There are 10 pairs of tests situated in
.
segment from 12 to 21
3- Each gives off a narrow efferent duct
which opens into common vas
deferens.
4- In the tenth segment the vas
deferens widens to form the
coueled vesicular seminalis.
5- It leads to ejaculatory from each duct
a narrow tube passes to the penis.
6- Prostate gland surrounded the penis.
56
B - Subclass Hirudinae
General Characteristics
Systems of Hirudinae
5- Reproductive system
7- There are two ovaries situated in
segment 11.
8- From each ovarian sac a short oviduct
units with its follow
to form common oviduct opens into the
vagina which
opens on segment behind the male
aperture.
Note
Prostate gland:
Its secretion
causes the
aggregation of
the sperms
into masses
called
spermatophore
57
B - Subclass Hirudinae
General Characteristics
Systems of Hirudinae
5- Reproductive system
The eggs collected in the inner part
9- -of the vagina (uterus).
10- Fertilization of eggs some times
occur in the vagina.
Reproduction
method:
"Like it in the earth worm"
58
General view
Figure 17.20
59
Quiz





Clitellata
1- Pronounced reproductive structure ………………
………………. Gonads
Are clitellata unisexual or hermaphrodites illustrate and illustrate the
different between the two ?
What the meaning of terrestrial biodiversity and distribution ?
60
Quiz
What do you benefit in this lecture ?
(write in short point and we
will see it in the next lecture )
Prepare the next lecture please
61