2. Phylum Mollusca
Classification
• Phylum Mollusca
• Class Polyplacophora
• Class Bivalvia - Mercenaria
• Class Gastropoda
• Class Cephalopoda - Loligo
3. Phylum Mollusca
• Mollusca
• 3 Main Body Regions
• Head-Foot
• Visceral Mass
• Mantle
• Bilateral Symmetry
• Coelomate
• Separate Sexes
• Terrestrial Forms
4. Phylum Mollusca
• Class Polyplacophora
• Shell composed of 8 plates
• Nearly sessile
• Moves with using a foot (slowly)
• Feeds by scraping with radula
• Chitons
5. Phylum Mollusca
• Class Gastropoda
• Coiled shell (shell may be reduced or absent)
• Large foot used for movement
• Head with 2 pairs of tentacles
• Active Herbivores (grazers); snails, nudibranchs,
slugs
7. Phylum Mollusca
• Class Bivalvia (Mercenaria)
• Living organism
• Chowder clams
• Two Valves that make up exterior of clam
• Sides / Lateral aspects of the clam
• Valves are attached on Dorsal side by knob-like
structure called the Hinge
• Not in the center of the clam’s Dorsal side (offset to one
side)
• Ventral aspect is smooth part of curve opposite the
hinge
• Left is Anterior and right is Posterior
8. Phylum Mollusca
• Clam opens and closes its Valves using Anterior &
Posterior Addutcor Muscles
• Mantle is found as a lining right along intact Valve
• Covers surface of the clam
• Secretes substances that harden to become the
shell/valves
• Mantle Cavity is the space between the right and
left mantles
• Visceral Mass is underneath the Mantle
• Is a plump round mass that makes up the bulk of the
clam
• Tough beige Foot is along edge of Visceral Mass
• Clam extrudes this between Valves and drags itself
9. Phylum Mollusca
• Gills are between foot and hinge
• Two very thin striated membranes
• On surface of & underneath Visceral Mass
• Hang in Mantle Cavity outside Visceral Mass
• Ventral to Posterior Retractor Muscle along edge of
Mantle is a tough yellowish (or black) structure
• This is two separate structures: Incurrent & Excurrent
Siphon
• Incurrent is the larger and most Ventral of the two
• The clam extrudes both Siphons out between the Valves
• Takes in water through Incurrent Siphon, which then flows
across the Gills, then across Visceral Mass to Anterior side
10. Phylum Mollusca
• On the Visceral Mass near the Anterior Retracctor
Muscle are two pairs of Labial Palps
• Mouth is between these two Palps
• Water flows past the Mouth, whatever is edible sticks to
mucus there, and passes to the Digestive Tract to be
digested
• Indigestible food is excreted through the Excurrent
Siphon (and leftover water)
• Smaller than Incurrent Siphon, just Dorsal to Incurrent
Siphon
• Heart is found just inside Visceral Mass on Dorsal
surface
11. Phylum Mollusca
• Digestive Gland is inside Visceral Mass by mouth
• Dark green color
• Produces and secretes digestive enzymes into stomach
and intestine
• Gonad is brown to cream and takes up rest of
Visceral Mass
• May have loops of clear tubing (part of intestine that
wind through the clam)
12. Phylum Mollusca
• Class Cephalopoda (Loligo)
• Squid
• Head-Foot is part of body which has Arms,
Tentacles, & Eyes
• Mantle is all the rest of body’s exterior
• Great deal of flexibility between Head-Foot & Mantle
• Visceral Mass consists of mass of internal organs
found inside the Mantle
• Space between Mantle & Visceral Mass is the
Mantle Cavity
13. Phylum Mollusca
• Head-Foot is Ventral aspect
• Opposite this is pointed end of Mantle; Dorsal aspect
• Anterior aspect is side of Mantle where Fins originate
• Other side of Mantle (flip it over) is Posterior aspect
• Arms & Tentacles are the long appendages
• Four pairs of shorter Arms lined with Suckers
• Two longer appendages are Tentacles; have Suckers on tips
• Retractable
• Used to capture and manipulate food
• On either side of Head-Foot are large and complex Eyes
• Free edge of Mantle is called Collar
• Extending out from under Collar is a short wide tubular
Siphon
14. Phylum Mollusca
• After dissecting, you can see of Dorsal surface all of the
following:
• Along sides of Visceral Mass connecting Siphon to mantle
is pair of Siphon Retractor Muscles
• Long, same color as Mantle, control movement of Siphon
• Head Retractor Muscles are Anterior to these the Siphon
Retractor Muscles
• Responsible for movement of Head (DON’T NEED TO
KNOW LOCATION OF THESE)
• Ink Sac is a long silvery or dark oval on top of Visceral
Mass
• Used for escape method (expels dense dark ink)
• Gills are the two long feathery structures in the Mantle
Cavity (not the Visceral Mass)
15. Phylum Mollusca
• Water enters the Mantle Cavity at the collar and
circulates within the Mantle Cavity and exits via the
Siphon
• Visceral Mass is covered by a transparent layer or
tissue
• A female will have two large white oval structures
called Nidamental Glands
• Virtually covers the organs of the visceral mass
• Dorsal to Nidamental Glands is the Ovary
• Need to be removed to see organs underneath
• This may contain Eggs
• Can range in color from white to translucent yellow
• Small, round, Very numerous
16. Phylum Mollusca
• On top of Visceral Mass are two white bubbly and
foamy Kidneys
• Not obvious or substantial
• At base of each Gill is a small round Branchial
Heart
• Basically pump blood through the Gills
• Between Branchial Hearts and Anterior (under) the
kidneys is a triangular Systemic Heart
• Has a tube leading from each point
• Is the third heart of the squid
• Pumps blood throughout the body of the squid
17. Phylum Mollusca
• Mouth is located between Arms and Tentacles
• The Mouth is inside a structure called the Buccal
Bulb
• Feels and looks like a large marble
• Esophagus is a tube that leads from the Dorsal end
• Goes towards a pale mushy mass
• At Ventral end of Bulb are chitinous Jaws
• Squid uses to tear apart prey
• Between the jaws is a structure that resembles a
cat’s tongue because of it’s bristles; this is the
Radula
• Moves food from the Mouth to the Esophagus to further
tear up pieces of food
18. Phylum Mollusca
• Esophagus leads toward Visceral Mass through pale
mushy Liver
• Takes up most of the space at the Ventral end of the
Visceral Mass
• Just Dorsal to the Systemic Heart the Esophagus
emerges from the liver to enter the hard muscular
Stomach
• About half as long and big around as our little fingers
• Further grinds up the squid’s food
• At Ventral end of Stomach (where Esophagus
enters) the Caecum & Intestine connect to the
Stomach
19. Phylum Mollusca
• Caecum is a thin walled bag which allows the digestive
enzymes to act on the food
• Stretches from the Stomach Dorsally to the tip of the
Mantle
• Will be small if the Ovary has a lot of Eggs
• If full it looks like a thin walled bag of yellow slime
• Pen is the long hard reddish brown plastic-looking
structure
• Under Caecum along inner anterior surface of mantle
• Functions as skeletal system of squid
• Intestine is very hard to find but connects Stomach to to
Rectum & Anus
• Rectum – Tube found running along the Ink Sac
• Anus – Opening at end of Rectum where waste is
excreted
20. Phylum Mollusca
• If female, Ventral to the Nidamental Glands there are
Accessory Nidamental Glands
• Two round red and white speckled organs
• The function of these and Nidamental Glands is to
secrete a capsule around each egg
• At base of Ovary near left Branchial Heart is the
Oviduct (leading away from the Ovary)
• Enlarges into Oviductal Gland
• Secretes the shell around each egg
• Then narrows, becoming a tube with a flared ending
called the Ostium
21. Phylum Mollusca
• If Male, lying alongside the Caecum is the long beige Testis
• Sperm travel from Testis to a series of organs near the left Branchial
Heart
• Circular Spermatophoric Organ collects sperm into long thin
packages called Spermatophores
• Often see linear Spermatophores through thin walls of Spermatophoric
Sac
• While mating Spermatohores are released from the Spermatophoric
Sac through tubular Penis
• Penis is Ventra to left Branchial Heart
• Males reach up in their Mantle Cavity with a specialized arm to gather
the Spermatophores
• Male then places the Spermatophores in the female’s Mantle Cavity
• The Female reaches up into the Mantle Cavity with an arm, grabs eggs from
the Ostium, fertilizes them with sperm from the Spermatophores
• Finally it places the fertilized eggs into the ocean
22. Phylum Mollusca
• Anatomy of the squid’s eye
• White ball inside called the Lens
• Back of the eye is a layer of tissue called the Retina
• Black on the inside and silvery on the outside
• Dark exterior absorbs light and prevents it from bouncing
around the inside of the eye
• The silvery exterior is reflective and prevents light from
entering the eye except from the front opening (pupil)
23. Phylum Mollusca
• These squids mate off the coast of Cali when 3
• Mate in a frenzy
• Males turn bright red when sexually stimulated
• When they distribute all Spermatophores they die
• When Females fertilize their eggs and lay them they
die
• The ocean floor becomes covered with dead squid
24. Phylum Arthropoda
Classification
• Subphylum Trilobita – Trilobite
• Subphylum Chelicerata
• Class Merostomata - Limulus
• Class Arachnida – Ixodes Dammini (deer tick)
• Subphylum Crustacea
• Class Malacostraca – Cambarus
• Subphylum Uniramia
• Class Chilopoda
• Class Diplopoda
• Class Insecta
25. Phylum Arthropoda
• Bilateral symmetry
• Jointed appendages
• Exoskeleton
• Separate sexes
• No nephridial system
• Metamerically segmented
• Open circulatory system
• Coelomate
26. Phylum Arthropoda
• Subphylum Trilobita
• Extinct
• Trilobite
• Subphylum Chelicerata
• 2 main body regions
• Cephalothorax, Abdomen
• 6 Pairs of jointed appendages
• 1st pair – chelicerae, no mandibles or antennae
27. Phylum Arthropoda
• Class Merostomata
• Marine
• Class Arachnida
• 4 pairs of walking legs on cephalothorax
• Terrestrial
• Spiders, ticks, mites, scorpions
• Subphylum Crustacea
• 2 main body regions
• Cephalothorax, abdomen
• 1-2 pairs of antennae
• 3+ pairs of legs
• Mandibles, 1-2 pairs of maxillae
28. Phylum Arthropoda
• Class Malacostraca
• 2 pairs of antennae
• 1 pair of mandibles
• 2 pairs of maxillae
• Barnacles, crabs, shrimp, hermit crabs, lobster
• Subphylum Uniramia
• Class Chilopoda
• One pair of legs per segment; Centipedes
• Class Diplopoda
• 2 pairs of legs for segments; Millipedes
29. Phylum Arthropoda
• Class Insecta
• 3 main body regions
• Head, thorax, abdomen
• 3 pairs of legs
• 1 pair of antennae
• 2 pairs of wings
• Bugs, beetles, moths, butterflies, flies, ants, bees,
Lubber grasshopper
31. Phylum Arthropoda
• Class Merstomata
• Limulus
• Horseshoe crab
• Changed very little since age of dinosaurs
• Two main body parts are Cephalothorax & Abdomen
• Cephalothorax is the done and Abdomen is the spined sides and“tail”
• On dorsal surface of Cephalothorax are two Compound Eyes
• On ventral surface of Cephalothorax are jointed appendages
• Chelicerae are the first pair
• Chelate Walking Legs are the rest
• At base of walking legs is the Mouth
• Book Gills (used for breathing) are on the Abdomen
• Animal terminates with long sharp spine called the Telson
32. Phylum Arthropoda
• Telson is used to turn crab over if on its back
• Live out in ocean
• Only come on land to lay eggs (a lot at one time)
• Females drag themselves up the beach, dig a hole, lay
their eggs, cover the hole, and go back to the ocean
(great parenting)
• Adapted to live in the ocean, not on land
• Many females die when on land
• Flipped upside down by wave and bake in sun
• Some are eaten by gulls
• Other get tossed into rocks and get stuck and die
(fucking dreadful isn’t it)
33. Phylum Arthropoda
• Class Malacostraca
• Cambarus
• Crayfish
• Similar body plan to shrimp and lobsters
• Two distinct body parts: Cephalothorax (anterior) & Abdomen
(posterior)
• On Cephalothorax are two short Antennules and two long Antennas
• Rostrum is the pointed part of the exoskeleton jutting out between two
stalked Eyes (on dorsal surface)
• On ventral surface are short Maxillipeds (feeding appendages)
• Funtion to manipulate food towards the Mouth
• Clustered around the oval hard Mandibles surrounding the Mouth
• Mandibles cut the food small enough to fit in the Mouth
34. Phylum Arthropoda
• Posterior to Maxillipeds are Walking Legs
• First pair have large pincers called Chelipeds
• Cheliped on first Walking Legs is used to capture, hold
and tear apart food
• Other Walking Legs allow the crayfish to “walk”
• Posterior to Walking Legs are short feathery Swimmerets
• At posterior end of crayfish the Abdomen spreads into a fan-
like structure
• The middle of the fan is the Telson
• On each side of the Telson are two Uropods
• Swimmerets, Telson, & Uropods assist the crayfish in
swimming
35. Phylum Arthropoda
• Dorsal exoskeleton of Cephalothorax is attached to the body by
two large interior Mandibular Muscles
• Under Cephalothorax exoskeleton are feathery Gills
• On top of all the organs is a rectangular beige Heart
• Heart is connected to the Aorta
• Dorsal abdominal artery
• Often too thin to be seen running along top of muscle mass
that comprises most of the Abdomen
• Blood is pumped by heart into Aorta and a few other short
major vessels
• Blood spills out of the vessels and bathes the organs in
blood
• Blood then flows down to the ventral side where the ventral
abdominal vein collects the blood and carries it up back to
the Heart
36. Phylum Arthropoda
• Below Heart are reproductive organs, Gonads
• Often same color as heart
• Different texture than surrounding tissues
• Tiny and difficult to see in immature crayfish
• In mature crayfish they are large and differently colored
• Ventral to reproductive organs & all along the sides of the
crayfish is the largest organ, the Digestive Gland
• Yellowish-beige in color
• Anterior to Digestive Gland in center of animal’s dorsum are
the two stomachs
• Cardiac Stomach is the large bag-like stomach, attached
to the Mouth by the Esophagus
37. Phylum Arthropoda
• Food passes through the Cardiac Stomach leading into the
smaller Pyloric Stomach
• Food then passes down the long, dark, tubular Intestine
• Can be seen running down the dorsal surface of the
Abdomen
• The Intestine exits the body at the Anus
• Nearly invisible pore on ventral surface of the Telson
• The Gastric Mill is a hard three-part device in the Pyloric
Stomach
• Used to grind up food
• Green Glands are found inside the crayfish just posterior to the
Eyes
• Perfect tiny ovals that fit into pockets down along the the
interior ventral surface of the exoskeleton
• Excretory organ of the crayfish
38. Phylum Arthropoda
• Between the Green Glands are thin cords reaching
anteriorly to a small mass of tissue, the Brain
• The thin cords are the anterior ends of the Ventral Nerve
Cord
• Runs the length of the crayfish on the ventral side of the
abdominal muscles
39. Phylum Arthropoda
• Class Insecta
• Lubber Grasshopper
• Three major body regions: Head, Thorax, & Abdomen
• Covered with and Exoskeleton
• On the Head are large Compound Eyes, the Mouth (with
numerous Mouthparts), and the Antennae
• Thorax sports multiple appendages
• Wings and all three pairs of the Legs
• Auditory Membrane is located just dorsal to the last (posterior)
pair of Legs
• Allows the grasshopper to “hear”
• Spiracles are a linear series of tiny holes on the sides of the
Abdomen that function is respiration
• At very end of the Abdomen waste exits through the Anus
40. Phylum Echinodermata
Classification
• Class Asterioda – Asterias
• Class Ophiuroidea
• Class Echinodiea
• Class Holothuroidea
41. Phylum Echinodermata
• Marine
• Pentaradial symmetry
• Dermal endoskeleton
• Nerve net
• Coelomate
• Reduced Circulatory and no excretory systems
• Deuterostomes
42. Phylum Echinodermata
• Class Asteroidea
• Asterias
• Starfish
• Flattened, star-like with arms grading into central disc
• Uses tube feet on oral surface for locomotion
• Feeds on gastropods, bivalves, and barnacles
• Class Ophiuroidea
• Brittle Star
• Flattened with flexible arms that are distinct from the
central disc
• Arms (not tube feet) used for locomotion
• Filter feeder with no anus
43. Phylum Echinodermata
• Class Echinoidea
• Sea Urchins & Sand Dollars
• Spherical or disc-like
• Movable spines
• Uses spines for locomotion
• No arms
• Herbivorous
44. Phylum Echinodermata
• Class Holothuroidea
• Sea Cucumbers
• Elongate
• Mouth surrounded by tentacles
• Endoskeleton reduced to spicules
• Uses worm-like motions and/or tube feet for locomotion
• Eats detritus or plankton
45. Phylum Echinodermata
Terms/Structures to Know
• Asterias
• Arm, Central Disc, Oral Surface, Mouth, Aboral
Surface, Madreporite, Ossicles, Spines,
Pedicellariae, Skin Gills, Ambulacral Groove, Tube
Feet, Eye Spot, Digestive Gland, Gonads,
Ambulacral Ridge, Radial Canal, Ampullae, Ring
Canal, Stone Canal, Water Vascular System, Anus
46. Phylum Echinodermata
• Class Asteroidea
• Asterias
• Starfish
• Consists of five Arms connected at the Central Disc
• Oral side has line of short protuberances
• Down center of each arm and the Mouth (in the center of
the central disc)
• Aboral side is fairly uniform with a round circular
structure on one side of the central disc (the
Madreporite)
• *No anterior or posterior because starfish has radial
symmetry
47. Phylum Echinodermata
• Skeleton of the starfish is considered dermal because
an epidermis covers the skeleton
• Composed of calcareous plates called Ossicles
• Not connected to each other, but imbedded into dermis
• Some Ossicles have long pointed projections – Spines
• Stick up above the surface of the Ossicles
• Movable and serve to protect the starfish
• Between Spines are tiny pincer-like projections of the
epidermis (Pedicellariae)
• Function to keep the surface of the starfish free of
debris
• Skin Gills – Only other dermal like projections; very tiny;
function as respiratory organs
48. Phylum Echinodermata
• Skin Gills and Pedicellariae only clearly visible under a
dissecting microscope
• Ambulacral Groove – Space on oral surface that runs
down the center of each arm & contains soft
protuberances
• The soft protuberances are Tube Feet
• Can be extended and retracted to move the starfish along
• At tip of each arm is a tiny Eye Spot
• Allows the starfish to see
• Anus exits body as a small nearly invisible pore on the
Aboral surface of Central Disc
49. Phylum Echinodermata
• Anus leads to rectum (invisible)
• Next to rectum are two little green or beige structures called the
Intestinal Ceacae
• On top of organs in central disc
• Function as storage organs for digestive waste
• Lie on top of thin, flat layer of tissue, the Pyloric Stomach
• Connects to digestive glands by thin Pyloric Ducts
• Under Pyloric Stomach is pleated beige Cardiac Stomach
• Esophagus connects the Pyloric Stomach to the Mouth
• Starfish is an effective carnivore of bivalves and gastropods
• Uses its arms to pry open an oyster then everts its Cardiac Stomach out
it’s mouth and down between the oyster’s shells onto the living oyster
• Digestive enzymes are secreted from the digestive glands onto the
oyster
• Oyster is digested while still in its shell and resulting molecules are
taken up into the Cardiac and then the Pyloric Stomachs for further
digestion
50. Phylum Echinodermata
• Digestive Gland – Down lengths of arms; greenish or
beige; many lobes
• Under Digestive Gland are smaller clearish Gonads
• Lay on either side of the Ambulacral Ridge
• Running through the Ridge is a tube, the Radial Canal
• Along the side of the ridge are a series of clear bubbles,
called the Ampullae
• Upper ends of the Tube Feet; connect the Tube Feet to
the Radial Canal
• Radial Canal runs up the arm and connects to the Ring
Canal (which circles the Central Disc)
51. Phylum Echinodermata
• Stone Canal connects the Ring Canal to the
Madreporite
• A hard covering of Ossicles these canals
• Water enters through the Madreporite, flows into the
Stone Canal, to the Ring Canal, down the Radial Canals
in the arms, and into the Ampullae
• When Ampullae contract, the water from them flows into the
Tube Feet
• Causes the Tube Feet to fill with water and elongate
• When Ampullae relax the water flows back into the
Ampullae and the Tube Foot is retracted
• Whole system is the Water Vascular System
52. Phylum Echinodermata
• Class Echinoidea
• Sea Urchins
• Have same basic body plan as a starfish
• Except that the urchin is fatter and the five arms are
contained within the round sphere
• Looking at the skeleton (Test), there are rows of holes
• Lines of holes are called the Ambulacra
• The holes are the spaces in the Test through which the
Tube Feet protrude
• Bumps on the Test are Tubercles
53. Phylum Echinodermata
• In preserved sea urchins a thin layer of Epidermis holds
a Spine on each Tubercle
• Allows the Spine to pivot on the Tubercle
• Sea urchins move along ocean floor using the pivoting
Spines
• Tube Feet are too short to be used in locomotion
• On Oral surface is the Mouth
• There are skeletal parts associated with the feeding
structures of the Mouth
• Collectively called Aristotle’s Lantern
• Can sometimes hear them rattling around inside Test
• Eventually breaks up into pieces small enough to fall
through the Oral hole in the Test; then the rattling stops
54. Phylum Echinodermata
• Sand Dollar
• Much the same external anatomy as the sea urchin
• FLATTENED
• Have same Tubercles and Spines
• Spines are so short that they make the preserved sand dollars
seem fuzzy instead of spiny
• Spines are used in locomotion like the sea urchin
• Ambulacra in the sand dollar curve around the Aboral
surface of Test
• Makes a petal-like pattern
• Tube Feet protrude though the holes in the Ambulacra
• On Oral surface is the Mouth & it’s associated Aristotle’s
Lantern
• Some sand dollars Tests will rattle because Aristotle’s Lantern
is intact inside of it
55. Phylum Echinodermata
• Class Holothuroidea
• Sea Cucumber
• Oral surface is at one end while the Aboral surface is at
the opposite end
• Oral surface is easy to identify because it’s where the
Tentacles surround the Mouth
• Tentacles are coated with a mucus layer
• Detritus and Planktonic organism get stuck here when
swimming
• Sea cucumber will scrape the organisms into its mouth into
its gut from the tentacle
56. Phylum Echinodermata
• Tentacle is removed from the Mouth to continue catching
food
• Down sides of the Sea Cucumbers body are rows of
Tube Feet (the rows are called Ambulacra)
• Tube Feet may assist the cucumber slightly in locomotion,
but most movement is from the cucumber wiggling its body
in a worm-like fashion along the ocean floor
