Download Lab 4 - Molluscs-Annelids

Lab 4
Exam 1 Next Week!
MOLLUSCA
&
ANNELIDA
•! 60 questions (1 point each)
•! 30 stations
•! 3 extra credit questions
•! ~ 1 hour to complete
Open lab for review: Friday 10:30-12:30
Phylum Mollusca
Chapter 11
General Characteristics
–! Bilateral symmetry
–! Complete digestive system
–! Open circulatory system
–! True (complete) coelom
–! Primitive excretory/
osmoregulatory system
Phylum Mollusca
–!Most have
•!Mantle (secretes the shell)
•!Radula (chitinous ribbon with rows
of teeth)
•!Gills (except terrestrial snails/slugs)
•!Muscular foot (some have evolved
into a muscular head)
–!Class Cephalopoda – “head-foot”
The four classes of mollusks we’ll study are…
•! The body of a mollusk has three main parts:
a muscular foot, a visceral mass, and a
mantle
mass
•! The body ofVisceral
a mollusk
has three main
parts: a muscular
foot, a visceral
Reproductive
Coelom
organs
Mantle
mass,Kidney
and aHeart
mantle
Digestive
Class Polyplacophora, (chitons)
Protected by 8 overlapping calcareous plates
tract
Mantle
cavity
Shell
Radula
Radula
Anus
Gill
Foot
Mouth
Nerve cords
Mouth
Class Bivalvia, (clams, oysters, mussels, & scallops)
Protected by shells divided into two halves
Class Gastropoda, (snails and slugs)
Protected by a single, spiraled shell or have a
hydrostatic skeleton
Class Cephalopoda, (squids, octopuses, and
nautilus) Exoskeleton, Endoskeleton, or
Hydrostatic Skeleton
Dissecting the Clam
•! Cut through the adductor muscles to open the clam
–! Tip: don’t twist the scalpel
Clam external anatomy
Dissecting the Clam
–! Slowly open the valves, You may have difficulty seeing
the siphons if you rip the mantle.
•! Once you have the clam open explore the internal
anatomy
Incurrent siphon
Excurrent siphon
Structures
•! Basic parts:
–! Shell
•! Also called valve
–! Muscles
•! Adductor
–! Mantle
•! Lines the shell
–! Gills
•! What do they do?
–! Visceral mass / foot
•! Most of the remaining
functions!
Dissecting the Clam
“butterfly cut”
Continue Dissecting the Clam
•! Using your scalpel slowly cut into the
visceral mass
–! Do this in a few individual slices
–! You’re “butterflying” open the visceral mass
•! Take a look around inside once you cut it
open
•! Identify internal structures
Freshwater Clam/
Mussel life cycle
Glochidium larva
(parasitize fish)
Phylum Annelida
(segmented worms)
Characteristics
Chapter 12
–! Bilateral symmetry
–! True coelom
–! Longitudinal and Circular muscles
–! Paired nephridia in multiple segments
(osmoregulation/excretion)
–! Segmented
–! Well developed closed circulatory system
•! True coelom ( True body cavity )
Body covering
The two classes of annelids we’ll study are…
Class Polychaeta, (marine worms)
have parapodia
Tissue layer
lining coelom and
suspending
internal organs
Digestive tract
Mesentery
True coelom (e.g., annelid)
Figure 17.8
Parapodia
- Observe preserved specimens
Class Clitellata, lack parapodia
Subclass Hirudinea (Leeches)
the two subclasses within Clitellata we’ll study are…
all have 34 segments, suckers, and some are parasitic
Subclass Oligochaeta (Earthworms),
which eat their way through soil
Saliva contains a local
anesthetic and the anticoagulant hirudin
Giant
Australian
Earthworm
The earthworms
The live earthworm dissection
•! BEFORE you start
–! Have everything ready
–! Dissection tray, pins, dissection kit, moist paper towel etc.
•! Anaesthetize earthworms for ~30 seconds in
ethanol
•! To work on them
–! Pin them down at the front and back
Secretes material that forms the
cocoon in which fertilized eggs are
incubated
•! Dorsal (dark side) up
•! Put them on moist paper towel
–! Take scissors and cut from clitellum to anterior end
–! Spread and pin tissue apart
Live earthworm dissection
Live earthworm dissection
Use scissors – slowly lift and snip…lift and snip
Use dissecting scope to see blood move in and out of hearts
Anterior region from a freshly
dissected live earthworm
One last thing to look at
intestine
dorsal
blood
vessel
•! Look for the
typhlosole
crop
seminal
vesicles
gizzard
Hearts
(5 aortic
arches)
seminal receptacles
–! Make a longitudinal
incision in the
intestine to see this
•! Can see this well on
the cross section
slide
Dissection Safety / Clean-up
•! Wear gloves when touching preserved
specimens.
•! Use common sense with sharp tools.
–! Report any injuries to me immediately.
•! Rinse off (and dry) all tools, and the dissection
tray, to keep them from rusting.
•! Do not make unnecessary cuts.
•! Do not throw animal parts in the trash or sinks!
–! Bring finished specimens to me for disposal.
Don’t forget to look
at the side
benches.
There is more to see!