Ocean Invertebrates Phylum Mollusca

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Ocean InvertebratesPhylum Mollusca
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Phylum- Mollusca

• Some EQs to think about
• How do they survive with their soft bodies?
• Why are they so successful?
• There are more species of molluscs than of any
  other animal group!
• 200,000 different species!
• Examples
• Clams and mussels
• snails, chitons and nudibranchs
• squid, cuttle fish and octopus

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Major Characteristics

• Soft Bodied
• with a shell made of calcium carbonate
• Mantle
• a thin layer of tissue that secretes the shell
• Bilateral symmetry
• Foot
• Ventral, muscular, used for locomotion
• Head
• Most have a head, with eyes and other sensory
  organs
• Radula
• Ribbon of small teeth that are used to feed
• Made of chiton
• Siphon
• Gas exchange through gills
• Habitat
• Fresh and salt water

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Classification of Mollusca

• Class Bivalvia
• Mussels, clams, oysters
• Class Gastropoda
• Snails, limpets, nudibranchs
• Class Cephalopoda
• Octopus, squid and cuttlefish

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Bivalves

• Body is laterally compressed
• Two shells, hinged together
• No head, no radula
• Gills used to obtain oxygen and to filter out
  small food particles from the water
• Inner surface of the shell is lined by the
  mantle, so the whole body lies in the mantle
  cavity.
• Adductor muscles keep shells closed
• As bivalve grows, it adds a layer to its shell

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Its Like a Straw

• Siphon tube that sticks out of shell
• Incurrent siphon takes in water carrying food and
  oxygen
• Excurrent siphon carries water containing wastes
  and CO2 out

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The Blue Mussel

• Uses byssal threads to attach to the substrate
• Threads are secreted by the mussels foot
• Anchors mussel in place on rocks to make filter
  feeding easier

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Heres Lookin at You, Kid.

• Dont attach to a substrate
• Scallops are the fastest moving bivalve
• Contraction of the adductor muscles forces water
  out from between the shells
• Scallop goes flying in the opposite direction

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A Shave and A Hair Cut

• The razor clam gets its name because it looks
  like the old fashioned razors
• It uses its muscular foot as a digging tool
• It can escape predators quickly by digging into
  the sand

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Gastropoda

• Gastropod means Stomach-footed
• A single shell-instead of two like bivalves
• A typical example is the snail, but dont be
  fooled this class makes up 2/3 of all mollusk
  species.
• Most use their radula to scrape alage from
  rockslike periwinkles and limpets
• But some are carnivoreslike whelks that feed on
  clams, mussels, worms or even small fish.

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http//www.personal.dundee.ac.uk/amjones/radula.j
pg
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http//www.armofthesea.info/images/animalimgs/cper
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Batton the Hatches!

• Snails have a trap door called the operculum
• They can close it to prevent water loss or to
  avoid being eaten!

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Im a sensitive guy

• Anterior tentacles sense by touch
• Posterior tentacles sense light
• Impulses travel along nerve to the tiny brain
  when danger is sensed, the animal can retract
  into its shell

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Juliannes Favorites!

• Nudibranchs
• Gastropods that have lost their shell
• Breathe through their cerata (colorful branches
  on their dorsal side)
• Often produce toxic chemicals for protection
• Or steal undischarged nematocysts taken from
  their prey.

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Cephalopoda

• Active lifestyle (compared to the other mollusks
• Name means head-foot
• Head
• Tentacles with suckers (like the foot of other
  mollusks)
• Swim by jet propulsion
• Shell is reduced or absent
• Complex nervous system
• Large eyes
• 650 speciesall marine

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Who Wants a Snack?

• Catches prey with tentacles
• Suction disks on tentacles used to grasp and hold
  prey
• Bite from beak kills prey
• Poisonous venom in some cases

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Giant Squid

A live giant squid (Architeuthis) measuring
roughly 25 feet long attacks a baited fishing
line off the Ogasawara Islands. Japanese
scientists recently released the first-ever
images of a live giant squid in the wild. Many
giant squid have washed up on beaches or have
been found dead or dying in fishing nets. This
specimen was found in New Zealand in 1996.
http//news.nationalgeographic.com/news/2005/09/09
27_050927_giant_squid.html
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http//news.nationalgeographic.com/news/2006/12/06
1222-giant-squid.html
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But They Dont Have Shells! How do they protect
themselves?

• Fast swimmers (jet propulsion)
• Force water out the mantle cavity through the
  siphon. The siphon can move and point the animal
  in any direction
• Camouflage Chromatophores
• Ink Cloud
• Intelligence
• Vision

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Please answer the following questions for
homework

• How do these soft bodied animals survive in the
  big, hungry ocean?
• Describe at least three different ways that
  mollusks feed.
• What type of symmetry do the mollusks have? How
  does this help with their survival?