phylum molluska 3 main classes of mollusks gastropoda : includes limpets, snails, slugs and whelks...
DESCRIPTION
3 Main Classes of Mollusks GASTROPODA : includes limpets, snails, slugs and whelks BIVALVIA: includes clams, oysters, muscles, scallops and shipworms CEPHALOPODA: includes octopi, squid, cuttlefish, nautilus and argonauts Above: Scallop showing off its eyes! Left: Cuttlefish and squid Above: LimpetTRANSCRIPT
Phylum MolluskaPhylum Molluska
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3 Main Classes of MollusksGASTROPODA : includes limpets, snails, slugs
and whelks
BIVALVIA: includes clams, oysters, muscles, scallops
and shipworms
CEPHALOPODA: includes octopi, squid, cuttlefish, nautilus and argonauts
Above: Scallop showing off its eyes!
Left: Cuttlefish and squid
Above: Limpet
All forms of Mollusks have a body composed of at All forms of Mollusks have a body composed of at least three distinct parts:least three distinct parts:
1.1. Visceral MassVisceral Mass- - A soft bodied portion that A soft bodied portion that
contains the internal organscontains the internal organs
2.2. FootFoot- - A strong, muscular portion A strong, muscular portion
used for locomotion (adapted used for locomotion (adapted as tentacles in cephalopods)as tentacles in cephalopods)
3.3. MantleMantle- A membranous, sometimes A membranous, sometimes
muscular covering that muscular covering that envelops but does not envelops but does not completely enclose the completely enclose the visceral massvisceral mass
- Can secrete a shellCan secrete a shell
Illustration of the general features of all mollusks
Identifying Characteristics of Mollusks• Have a Have a coelomcoelom which allows for which allows for specialization of organ specialization of organ
systemssystems• Most are Most are bilaterally symmetricalbilaterally symmetrical• All have a All have a visceral mass, foot and mantlevisceral mass, foot and mantle (see (see
previous slide)previous slide)• Possess a Possess a one-way one-way digestive systemdigestive system with specialized with specialized
organs and have feeding organs and have feeding mouthpartsmouthparts• Cephalopods have a closed Cephalopods have a closed circulatory systemcirculatory system, all , all
other classes possess other classes possess openopen circulatory systems circulatory systems• Many have highly developed Many have highly developed cephalizationcephalization with with sensory sensory
organsorgans• Many have calcium carbonate Many have calcium carbonate external shellsexternal shells• Respiratory systemRespiratory system includes the use of includes the use of gillsgills to extract to extract
OO22 and get rid of waste and get rid of waste• Many have a Many have a radularadula which is a which is a chitinous tonguechitinous tongue used for used for
feedingfeeding• Sexual ReproductionSexual Reproduction (have separate sexes: (have separate sexes: dioeciousdioecious))
The Gastropods : “belly” “foot”The Gastropods : “belly” “foot”• Usually are Usually are univalvesunivalves
(one shell)(one shell)• Large, Large, muscular muscular footfoot• Well definedWell defined headhead• MusclesMuscles move move in a in a
rippling motion for rippling motion for movementmovement
• Most possess Most possess gillsgills but but some have some have lungslungs
• Have a Have a radularadula to help to help obtain foodobtain food
• Most snails have a lid-like Most snails have a lid-like part called an part called an operculum operculum on the back of the foot on the back of the foot so so they can draw their they can draw their bodies into their shell and bodies into their shell and close off the openingclose off the openingUnderside of a Limpet
Gastropods in Love….Gastropods in Love….
.. and a lonely garden slug….
The Bivalves : “two” “shell”The Bivalves : “two” “shell”• Possess Possess 2 shells that 2 shells that
can be tightly closed can be tightly closed with strong muscleswith strong muscles
• Strong, Strong, muscular foot muscular foot and use it for and use it for locomotionlocomotion
• No No head or teethhead or teeth• Obtain food and oxygen Obtain food and oxygen
by by using a muscular using a muscular siphon that brings siphon that brings water to the gills water to the gills which which filter out Ofilter out O22 and plant and plant cell materialcell material
• Often Often attach attach themselves to surfacesthemselves to surfaces
• Possess Possess an open an open circulatory systemcirculatory systemGIANT CLAM
Above left: Elephant trunk clams, named for their large foot
Above right: an opened oyster commonly enjoyed raw or cooked as a delicacy
Lower right: Scallop showing off its many primitive eyes
The Cephalopods: “head” “foot”The Cephalopods: “head” “foot”• Bilaterally Bilaterally symmetricalsymmetrical• Prominent Prominent head, arms head, arms
and tentaclesand tentacles• Have Have developed braindeveloped brain, ,
“intelligent “ creatures“intelligent “ creatures• Arms that take in food Arms that take in food
surround surround hard, strong, hard, strong, beak-like jawsbeak-like jaws that tear that tear the prey and secrete a the prey and secrete a poison to paralyze itpoison to paralyze it
• Closed Closed circulatory system circulatory system with with hemocyanin hemocyanin (like (like hemoglobin)hemoglobin)
• Move Move by jet propulsionby jet propulsion• Can change color with Can change color with
the use the use of of chromatophoreschromatophores
• Possess Possess advanced visionadvanced vision• Secrete Secrete an ink cloud an ink cloud
when in dangerwhen in danger
SquidSquid
Caribbean Reef Squid Tentacles of a giant squid
Calamari: a deep fried squid dish Squid eye and gills
OctopusOctopus
Octopus beak Octopus on the beach
Swimming Octopus Octopus arm in detail
Octopi are extremely intelligent creatures Octopi are extremely intelligent creatures and have been known to learn to escape and have been known to learn to escape from their aquariums when in captivity from their aquariums when in captivity through very small cracks at the top.through very small cracks at the top.
Ecological Roles of MollusksEcological Roles of Mollusks• Mollusks are part of Mollusks are part of the the
aquatic food chainaquatic food chain (see (see picture to left)picture to left)
• Many mollusks are Many mollusks are keystone species: if their keystone species: if their numbers decrease the numbers decrease the decline of other marine decline of other marine species will followspecies will follow
• Filter feeders help to Filter feeders help to purify the waterpurify the water
• Many bivalves are Many bivalves are reef reef forming and provide an forming and provide an ecosystem for other ecosystem for other aquatic speciesaquatic species
• Reef builders Reef builders stabilize stabilize banks and bottom banks and bottom sedimentssediments
Starfish eating (digesting) a mussel
Squid FactSquid Fact
The largest squid ever caught was a 10 m long Colossal Squid off the coast of New Zealand and
weighed in at 495 kg. Colossal Squid are larger than the giant squid found off the Mexican coast and are
thought to grow in size to a whopping 13 meters!