Major Mollusk Classes

A Survey of Marine Animal
Kingdoms
Gastropods
They make up over 2/3 of all the Mollusk
species.
Gastropod means “stomach foot”.
Snails and Nudibranchs are the most
common Gastropods.
Class Gastropoda
• Many snails
can withdraw
into the shell
and close it
off with a
horny
operculum.
Gastropod Feeding Habits
• Most gastropods are
herbivores and feed
by scraping off algae
using the radula.
• Some are scavengers
of dead organisms
• Others are carnivores
that drill into other
mollusks
COLORFUL MOON SNAIL
NORTHERN ABALONE
CONE SNAILS
HORSE CONCH
• Florida state shell
• Voracious carnivore
QUEEN CONCH
Ocular
notch
Busycon
Gastropod egg
cases
Naticidae
SHELL-LESS GASTROPODS
SEA SLUGS & NUDIBRANCHS
NUDIBRANCH MEANS “NAKED GILL”
SHELL-LESS ANIMALS MUST PROTECT
THEMSELVES WITH POISON/TOXIN,
KEPT IN CERATA OR MUCUS
BRIGHTLY COLORED TO “ADVERTISE”
POISON
ELEGANT NUDIBRANCH
Florida Sea Goddess
SPOTTED SEA HARE
Parapodia
Bi-Valves
Class Bivalvia
• Bivalve mollusks
have two shells
(valves) that are
hinged.
• clams, oysters,
scallops, cockles,
mussels, shipworms
Bi-Valves
Sessile. Filter feeders
NO radula
They take in, and release, water
through a Siphon Tube.
They breathe underwater using Gill
Membranes.
Some Bi-Valves are swimmers, such
as scallops.
They have separate sexes with
sperm and eggs being released into
the water (external fertilization).
Clam Anatomy
Soft-bottom burrowers
• Rely on blade-like foot
for burrowing
• Rely upon long siphons
Cockle
Surface dwellers attached via
byssus: threadlike anchors
Pen Shell
Arcidae
Pinnidae
Oysters
Winged
oysters
Tridacnidae
Giant Clam
Mussels
Pteriidae
Cemented surface dwellers: No bysuss
Several unrelated groups of “oysters” independently evolved ability to
cement on one side.
True oysters (Ostreidae), jewel boxes (Chamidae), thorny oysters
(Spondylidae).
Oyster
Oyster
Oyster reef
Jewel box
Thorny oyster
CEPHALOPODS
HI KIDS, MY
NAME IS
SQUIDWARD.
WANNA MEET
SOME OF MY
RELATIVES?
CHARACTERISTICS
• MOST ADVANCED OF THE MOLLUSKS
• ACTIVE SWIMMERS – …
• EYES ARE HIGHLY DEVELOPED
• ARMS & TENTACLES HAVE SUCTION
CUPS TO HOLD PREY
• BEAK-LIKE MOUTH TO BITE PREY
• VENOM IN SALIVA PARALYZES PREY
• CAN CHANGE COLOR RAPIDLY
Class Cephalopoda
• Most cephalopods
have complex eyes
with cornea, lens,
chambers, and
retina.
• Largest
invertebrate brain
• Closed circulation
Class Cephalopoda - Locomotion
• Cephalopods
swim by expelling
water from the
mantle cavity
through a
ventral funnel.
Protection
• Color changes effected by chromatophores
(pigment cells)
• Allows them to blend into their background
• Squirting out water by jet propulsion helps
escape predators
• Squids also release an inky substance into the
water
Class Cephalopoda - Reproduction
• Sexes are separate
in cephalopods.
• Juveniles hatch
directly from eggs –
no free-swimming
larvae.
• One arm of male
removes a
spermatophore from
mantle cavity and
inserts it into
female.
SQUID
VERY ACTIVE SWIMMERS
COMMONLY FOUND IN SCHOOLS
VERY AGGRESSIVE PREDATORS
8 ARMS
2 TENTACLES
SIPHON
BEAK
OF
SQUID
SQUID SUCKERS
GIANT SQUID
GIANT
SQUID
SQUID EGGS
RMJA
OCTOPUS
RARELY SWIMS, CRAWLS WITH 8 ARMS
LIVES IN HOLES/CREVICES/BURROWS
FEEDS AT NIGHT – NOCTURNAL PREDATOR
SQUIRT INK AS A DEFENSE TO ESCAPE
VISCERAL
MASS
8 ARMS
SIPHON
CEPHALOPODA
Octopus joubini
Caribbean
reef octopus
Atlantic pygmy
octopus
Octopus briareus
http://www.eumed.net/malakos/Imahispa/Argonauta%20nouryi.jpg
Octopus vulgaris
Octopus vulgaris
Common octopus
Caribbean reef Sepioteuthis
sepioidea
squid
GIANT PACIFIC OCTOPUS
CHAMBERED NAUTILUS
Trapped gas
bubbles keep
the nautilus
buoyant