Download Chapter 7- Part 2

Chapter 7- Part 2
Marine Biology
Phylum Mollusca
Mollusks
• Greatest # of species
• Body covered by mantle made
of calcium carbonate
• Bilateral symmetry
• Foot used for locomotion
• Radula used to feed
Gastropods:
• Snails
• Mostly eat algae from rocks- ex.
Periwinkles
Continued……
• Some snails such as mud snails
are deposit feeders
Continued…….
• Snails such as whelks can be
carnivorous preying on clams,
worms, or small fish
Continued……
• Sea slugs are snails without
shells. Often have noxious
chemicals or nematocysts for
protection
Bivalves:
• Clams, mussels, oysters
• Body enclosed in shell
• Gills filter food and used for
breathing
• Mantle lines the inside of shell
Continued……
• Clams use foot to burrow in
sand- water enters and leaves
shell through siphon
Continued…….
• Mussels attach themselves by
using byssal threads
Continued……
• Oysters cement their left shell
to a hard surface- often other
oysters
• Pearl oysters are the source of
most valuable pearls.
How a pearl is made:
• Particles merge in between
mantle cavity and shell
• Oyster secretes shiny layers of
calcium carbonate to coat
irritating particle
• Oysters can be forced to make
pearls by inserting an irritant
in shell (cultured pearl)
Cephalopods:
• Octopus, squid, cuttlefish
• Good swimmer
• Complex nervous system
• No shell
• Arms with suckers to capture
prey
• Eyes on side of head
• Move by forcing water out of
their siphon, or funnel
Octopus
• 8 arms (2 in to 9 ft in size)
• bottom dwellers
• Efficient hunters- crabs,
lobsters, and shrimp
• Radula scrapes away flesh
• Some are toxic and their bite
can paralyze
• Live in crevices and even
discarded bottles
• Distract predators by spraying
ink
Squid
• Better adapted for swimming
• Ten arms
• Two of the arms are longer and
wider for catching prey
• Sizes range up to 66ft in the
giant squid
Cuttlefish
• Similar to squid except the body
is flattened
Biology of Mollusks
Digestion:
• Separate mouth and anus
• Radula can be modified from
scraping or drilling through flesh
• Amount and strength of digestive
enzymes range depending on
matter being digested
Circulatory system:
• Most mollusks have a open
circulatory system- blood flows out
of vessels into open space
• Cephalopods have a closed
circulatory system-blood always
remains in vessels
Nervous System:
• Most mollusks have a ganglia
• Cephalopods have a more
advanced brain, similar to humans
• Intelligent and remarkable
learners- some cuttlefish can even
change colors
Reproduction:
• Usually separate sexes
• Some hermaphrodites
• In bivalves and some snailsexternal fertilization
• Cephalopods and most snailsinternal fertilization
• Cephalopods do not have
larvae- young born from and
egg. Mother usually dies
after egg hatches due to lack
of food while guarding egg.
Phylum Arthropoda
Arthropods
• Barnacles, shrimp, lobster,
crab, etc.
• Segmented
• Bilateral symmetry
• Jointed appendages
• Exoskeleton
• Molt to grow-old
skeleton discarded,
animal takes in water
to expand itself, grows
a new skeleton
Crustaceans:
• Called the insects of the sea
• Gills
• Appendages used to swim,
crawl, feed, and mate
• Two pair of antennae (sensory
organs)
Small Crustaceans
• Copepods- planktonic, some
parasitic
• Barnacles-filter feeders; live
attached to surfaces
• Beach hoppers (amphipods)tail and head curve down,
strong jumpers
• Isopods- marine version of a
roly-poly
• Krill- shrimp-like, filter
feeders, main food source for
many whales, penguins, and
fish
Large Crustaceans
• Decapods- shrimp, lobster, crab
(10 legs)
• Commercial importance
• 5 pair of walking legs
• First pair larger for obtaining
food and in defense
• Shrimps typically scavengers
• Lobsters tend to be nocturnal
(hide during day)- scavenge and
catch prey
• Crabs are scavengers as well
• Female crab-U shaped abdomen
for carrying eggs
• Male- V shaped abdomen
Digestion:
• Small teeth or ridges are
found in stomach for
grinding
• Digestive glands help digest
and absorb nutrients
Nervous System:
• Small brain
• Compound eyes- In decapods at
the end of stalks
• Body posture used for
communication: mating,
disputes, hunting, etc.
Reproduction:
• Mostly separate sexes
• Males directly penetrate females
to reproduce
• Reproduction in decapods takes
place directly after molting
• Can store sperm
Phylum Echinodermata:
Echinoderms
• Sea stars, sea urchins, sea
cucumbers, etc.
• Larvae –bilateral symmetry
• Adults-radial symmetry
• Lack a head
• Oral surface/aboral surface
• Water vascular system
• Tube feet and ampullae’s are
part of this system
• Madreporite connects internal
to the external
*Sea Stars
• Tube feet (with suckers) found
in ambulacral groove
• Pedicellariae help keep surface
clean
• Eat bivalves, snails, barnacles,
etc.
*Brittle Star
• Long arms
• Tube feet lack suckersfeeding
• Organic matter, small
animals
*Sea Urchins
• Round, rigid, spines
• 5 ambulacral grooves with
spines
• grazers
• Flat version with short spinessand dollar
*Sea Cucumbers
• Worm-like
• No spines
• Oral/aboral surfaces at each end
• Tube feet modified and
resemble tentacles- used to pick
up food
• Interesting defense methods:
~ discharge sticky substance
through anus
~eviscerate internal organs
*Crinoids
• Better known as feather stars
or sea lilies
• Deep waters
• Attached to bottom
*Digestion:
• Most extend stomach
through mouth-digest foodand then pull stomach back
in
*Nervous System:
• No brain
• Complex behaviors for the
absence of a brain- camouflage,
reposition itself if moved
*Reproduction:
• Separates sexes
• Sperm/egg shed directly into water
• Spawn all at once to ensure
fertilization
• Asexual reproduction- if central
disks is separated it can form into
two new organisms (regeneration)