phylum mollusca - paramorina · •soft-bodied invertebrate covered with protective mantle that may...
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Phylum Mollusca
Characteristics
• Soft-bodied invertebrate covered with protective mantle that may or may not form a hard, calcium carbonate shell
• Second largest animal phylum
• Have a muscular foot for movement which is modified into tentacles for squid & octopus
• Complete, one-way digestive tract with a mouth & anus
Characteristics
• Cephalization - have a distinct head with sense organs & brain
• Have a scraping, mouth-like structure called the radula
• Go through free-swimming larval stage called trochophore
• Body organs called visceral mass lie below mantle
Characteristics
• Bilaterally symmetrical
• Most have separate sexes that cross-fertilize eggs
• Use jet propulsion to move by forcing water out siphon
• Includes 4 classes --- Polyplacophora (chitons), Gastropoda (snails, slugs, nudibranchs, conchs & abalone), Bivalvia (clams, oysters, & mussels), & Cephalopoda (squid, octopus, & nautilus)
Class Polyplacophora
• Have a shell divided into 8 over-lapping plates and live on rocks along seashore feeding on algae
• ex: Chiton
Chiton
Plates
Girdle
Class Gastropoda
• Head has a pair of retractable tentacles with eyes located at the ends
• Have a single shell or valve (snails) or none (slugs)
• ex: Moon Snail, Abalone, Cowry, Nudibranch (sea slug), Sea Hare
Moon Snail
Abalone
Cowry
Nudibranch (sea slug)
Sea Hare
f – Foot g – Siphon h – Tentacle i – Eye j – Mouth l - Mantle
a – Mantle b – Foot f/g– Tentacle
Class Bilvalvia
• Sessile Filter feeders
• Have two-part, hinged shell (2 valves)
• Have muscular foot that extends from shell for movement
• Scallops clap valves together to move
http://youtu.be/xsh41CG3Pc8
Class Bilvalvia
• Mantle secretes substance called "mother of pearl" to surround irritants like grains of sand
• Oldest, raised part of shell called umbo
• Powerful anterior & posterior adductor muscles open & close shell Lack a distinct head
Class Bilvalvia
• Have a siphon that circulate water over the gills to remove food & oxygen
• Have heart & circulatory system
• Separate sexes with external fertilization of eggs
• ex: clams, oysters, scallops, mussels
Clams
Oysters
Scallops
Mussels
c – Foot d – Shell f – Mantle g – Eye
Adductor
Class Cephalapoda
• Most intelligent mollusk
• Well developed head
• Active, free swimming predators
• Foot divided into tentacles with suckers
Class Cephalapoda
• Use their radula & beak to feed
Class Cephalapoda
• Circulatory system
• Lack an external shell
• Highly developed nervous system with vertebrate-like eyes
• Separate sexes with internal fertilization
Class Cephalapoda
• Chromatophores in the skin can help change color for camouflage
http://youtu.be/IAGxTsEmGek
Squid
• Largest invertebrate is the Giant Squid
(~40 feet with an eye ball the size of a beach ball)
Squid
• 8 arms and 2 long tentacles to catch prey
• Can squirt an inky substance into water to temporarily blind predators
Squid
• Have internal shell called pen
• Female lays eggs in jellylike material & protects them until hatching
Vampire Squid
Bobtail Squid
a – Mantle c – Fin d – Head e – Arm g – Tentacle h – Sucker i – Beak
Octopus
• Eight arms
• Crawls along bottom looking for prey
Octopus
• Blue Ringed Octopus – live in coral reefs in the Pacific and Indian Oceans from Japan to Australia; recognized as one of the world’s most venomous marine animals.
Octopus
• Dumbo Octopus – live at extreme depths (10,000-20,000 feet)
a – Mantle c – Fin d – Head e – Arm g – Tentacle h – Sucker i – Beak
Cuttlefish
• Eight arms and two tentacles
• masters of camoflauge
Chambered Nautilus
• Most primitive living cephalopod dating back 450 million years
• 38 outer tentacles and inner (male = 24 / female = 48-52)
Chambered Nautilus
• Has an exterior shell with 38 chambers
• Lives in the outer chamber of the shell
• Secretes gas into the other chambers to adjust buoyancy
a – Shell b – chamber c – Siphuncle d – Eye e – Tentacle