What are Mollusks?What are Mollusks? The name Mollusca (from the Latin The name Mollusca (from the Latin mollismollis meaning soft), was first used by the meaning soft), was first used by the

French zoologist Cuvier in 1798 to describe squids.French zoologist Cuvier in 1798 to describe squids. All mollusks have a muscular foot (used for moving) and a mantle (an All mollusks have a muscular foot (used for moving) and a mantle (an

outgrowth that covers the animal). outgrowth that covers the animal). Most mollusks have an external calcium carbonate shell that is produced by the Most mollusks have an external calcium carbonate shell that is produced by the

mantle. mantle. All All body systems body systems are present. are present. Many also have a radula (a unique organ that is mostly composed of a hard Many also have a radula (a unique organ that is mostly composed of a hard

material called chitin) in the mouth that allows the animal to scrape food from material called chitin) in the mouth that allows the animal to scrape food from surfaces by sliding back and forth. Like a rasping tongue.surfaces by sliding back and forth. Like a rasping tongue.

Mollusks have a coelom (a body cavity), but the coelom is made from cell Mollusks have a coelom (a body cavity), but the coelom is made from cell masses, making all species in this phylum protosomes. All organs are masses, making all species in this phylum protosomes. All organs are suspended in this coelom, between the outer covering and the digestive tube of suspended in this coelom, between the outer covering and the digestive tube of the animal. However, animals in this phylum are unique to coelomates in that the animal. However, animals in this phylum are unique to coelomates in that they lack body segmentation.they lack body segmentation.

TaxonomyTaxonomy

Body Systems of MollusksBody Systems of Mollusks RespiratoryRespiratory- diffusion still occurs (through mantle) but specialized gills, lungs - diffusion still occurs (through mantle) but specialized gills, lungs

present  (derived from mantle).present  (derived from mantle).

CirculatoryCirculatory- pumping heart, vessels and sinuses; open system in all but cephalopods; - pumping heart, vessels and sinuses; open system in all but cephalopods; – HemocyaninHemocyanin- oxygen combining pigment or “blood” that contains copper and is bluish  when - oxygen combining pigment or “blood” that contains copper and is bluish  when

combined with oxygen. combined with oxygen.

Digestive-Digestive- complete and complex; mouth to anus. complete and complex; mouth to anus.

ExcretoryExcretory- 2 nephridia (kidneys) empty into mantle cavity. - 2 nephridia (kidneys) empty into mantle cavity.

NervousNervous- ganglia and connecting nerve cord; specialized eye in cephalopods.- ganglia and connecting nerve cord; specialized eye in cephalopods. ReproductiveReproductive- most are dioecious (unisexual), but some gastropods are monoecious - most are dioecious (unisexual), but some gastropods are monoecious

(heterosexual).(heterosexual).

(Go Back)(Go Back)

Phylum: MolluskaPhylum: Molluska

The 7 major classes belonging to Mulluska.The 7 major classes belonging to Mulluska. AplacophoraAplacophora - Mollusks without shells - Mollusks without shells BivalviaBivalvia – Clams and their relatives – Clams and their relatives CephalopodaCephalopoda – Squids and their relatives – Squids and their relatives GastropodaGastropoda - Snails and their relatives - Snails and their relatives MonoplascophoraMonoplascophora - Mollusks with one plate - Mollusks with one plate PolyplacophoraPolyplacophora – Chitons – Chitons SchapodaSchapoda - Mollusks with a tubular shell - Mollusks with a tubular shell

(Go Back)(Go Back)

Class: AplacophoraClass: Aplacophora(belongs to Phylum: (belongs to Phylum: MolluskaMolluska))

This class includes two subclasses called Caudofoveata and Solenogastres.This class includes two subclasses called Caudofoveata and Solenogastres.

Both classes contain relatively few species. The Caudofoveata are aberrant Both classes contain relatively few species. The Caudofoveata are aberrant molluscs which lack shells. They normally burrow in soft sediments and are molluscs which lack shells. They normally burrow in soft sediments and are quite common in the deep sea. The class Solenogastres is also very small. quite common in the deep sea. The class Solenogastres is also very small. These animals also lack shells and generally live epibenthically (on the surface These animals also lack shells and generally live epibenthically (on the surface of the substratum). of the substratum).

They usually They usually resemble wormsresemble worms, and are found in deep water, often more than , and are found in deep water, often more than 3,000 m. There are only about 300 species in this class, and besides lacking 3,000 m. There are only about 300 species in this class, and besides lacking shells, they are all marine and generally very small.shells, they are all marine and generally very small.

NONE OF OUR SAMPLES BELONG TO NONE OF OUR SAMPLES BELONG TO APLACOPHORAAPLACOPHORA..

(Go Back)(Go Back)

Chaetoderma canadenseChaetoderma canadense(an Aplascophoran)(an Aplascophoran)

(Go Back)

Class: BivalviaClass: Bivalvia(belongs to Phylum: (belongs to Phylum: MolluskaMolluska))

The bivalves are bilaterally symmetrical (can be divided along their length into two The bivalves are bilaterally symmetrical (can be divided along their length into two mirrored - right and left halves) with extensive mantle lobes which secrete a single shell mirrored - right and left halves) with extensive mantle lobes which secrete a single shell composed of two valves. The two valves of the shell are hinged dorsally where they are composed of two valves. The two valves of the shell are hinged dorsally where they are held together by a new structure, the ligament, and completely enclose the rest of the held together by a new structure, the ligament, and completely enclose the rest of the body. The valves are closed by two large muscles. Bivalve body. The valves are closed by two large muscles. Bivalve respirationrespiration and and locamotionlocamotion reflect the morphology described. reflect the morphology described.

Class Bivalvia includes all of the bivalves. These are marine animals with a hinged shell Class Bivalvia includes all of the bivalves. These are marine animals with a hinged shell divided into two halves. The hinge is head together by a ligament and one or two divided into two halves. The hinge is head together by a ligament and one or two adductor muscles. Most live in sand or mud, and use their foot for digging and anchoring adductor muscles. Most live in sand or mud, and use their foot for digging and anchoring to surfaces. These bivalves use the hinges to take in food, and are also able to jet some to surfaces. These bivalves use the hinges to take in food, and are also able to jet some distance away by closing the hinged shell and squirting the water taken in out of the distance away by closing the hinged shell and squirting the water taken in out of the mantle cavity. Bivalves lack a head and have a spacious mantle cavity as well. Some mantle cavity. Bivalves lack a head and have a spacious mantle cavity as well. Some examples include clams, oysters, scallops, and mussels. examples include clams, oysters, scallops, and mussels.

The bivalves are mainly marine, but a few species are found in freshwater habitats, The bivalves are mainly marine, but a few species are found in freshwater habitats, although none have invaded the land. Many species of bivalve are of commercial although none have invaded the land. Many species of bivalve are of commercial importance.importance.

NEXTNEXT

Respiration in BivalvesRespiration in Bivalves

The mantle cavity of bivalves is greatly expanded and now surrounds the rest The mantle cavity of bivalves is greatly expanded and now surrounds the rest of the body. Inside the mantle cavity are the large leaf-like ctenidia (feathery or of the body. Inside the mantle cavity are the large leaf-like ctenidia (feathery or comb-like structures), each of which consists of a dorsal (the back of an organ comb-like structures), each of which consists of a dorsal (the back of an organ or body) vascular axis from which hang an inner and outer gill plate, or or body) vascular axis from which hang an inner and outer gill plate, or demibranch, made up of numerous parallel gill filaments. demibranch, made up of numerous parallel gill filaments.

Each plate is not single, but is folded back on itself in a V-shape and thus has Each plate is not single, but is folded back on itself in a V-shape and thus has an ascending and a descending lamella. The two plates, when seen in cross an ascending and a descending lamella. The two plates, when seen in cross section have a section have a W-shapeW-shape. .

Usually the lamellae are held together by junctions of different types; Usually the lamellae are held together by junctions of different types; interlamellar junctions join the lamellae together and interfilamentar junctions interlamellar junctions join the lamellae together and interfilamentar junctions join the adjacent filaments together. The more primitive bivalves, e.g. the join the adjacent filaments together. The more primitive bivalves, e.g. the mussel family, possess filibranch gills in which the interfilamentar junctions are mussel family, possess filibranch gills in which the interfilamentar junctions are only patches of interlocking cilia. only patches of interlocking cilia.

(Go Back)

Shape of lamellar platesShape of lamellar plates

(Go Back)

Bivalve LocomotionBivalve Locomotion

Most bivalves are sedentary and many are adapted for Most bivalves are sedentary and many are adapted for burrowing into soft sediments using the laterally burrowing into soft sediments using the laterally compressed foot. A few are capable of boring into wood, compressed foot. A few are capable of boring into wood, and some are even able to bore into rockand some are even able to bore into rock..

Although most bivalves are sedentary, some, especially Although most bivalves are sedentary, some, especially members of the scallop family, are able to swim actively members of the scallop family, are able to swim actively over short distances, usually to escape potential predators. over short distances, usually to escape potential predators.

The scallops swim by rapidly ejecting water from the The scallops swim by rapidly ejecting water from the mantle cavity by rapid clapping together (adduction) of the mantle cavity by rapid clapping together (adduction) of the shell valves, which forces water out on either side of the shell valves, which forces water out on either side of the hinge. Scallops usually swim in short bursts, but may cover hinge. Scallops usually swim in short bursts, but may cover several metres at a time.several metres at a time.

(Go Back)

Orders belonging to Orders belonging to Class: BivalviaClass: Bivalvia

Major orders belonging to Mollusca/Bivalvia.Major orders belonging to Mollusca/Bivalvia. ArcoidaArcoida MyoidaMyoida MytiloidaMytiloida PterioidaPterioida UnionoidaUnionoida VeneroidaVeneroida

(Go Back)

Order: ArcoidaOrder: Arcoida(belongs to Class: (belongs to Class: BivalviaBivalvia))

Major families belonging to Major families belonging to Molluska/Bivalvia/ArcoidaMolluska/Bivalvia/Arcoida

ArcidaeArcidae (Ark shells) (Ark shells) GlycymerididaeGlycymerididae (Bittersweet clams) (Bittersweet clams)

(Go Back)

Family: ArcidaeFamily: Arcidae(belongs to Order: (belongs to Order: ArcoidaArcoida))

These shells almost always have straight These shells almost always have straight hinge lines and strong umbones. Most are hinge lines and strong umbones. Most are ovate.ovate.

Major Genera and speciesMajor Genera and species Anadara Anadara

– brasiliana (Incongruous Ark)brasiliana (Incongruous Ark)– transversa (Transverse Ark)transversa (Transverse Ark)

Noetia Noetia – ponderosa (Ponderous Ark)ponderosa (Ponderous Ark)

(Go Back)

Family: GlycymerididaeFamily: Glycymerididae(belongs to Order: (belongs to Order: ArcoidaArcoida))

These shells have V-shaped ligaments and These shells have V-shaped ligaments and many teeth. They are usually round or many teeth. They are usually round or broadly ovate.broadly ovate.

Major Genera and speciesMajor Genera and species Glycymeris Glycymeris

– pectinata (Comb Bittersweet)pectinata (Comb Bittersweet)

(Go Back)

Order: MyoidaOrder: Myoida(belongs to Class: (belongs to Class: BivalviaBivalvia))

Major families belonging to Major families belonging to Molluska/Bivalvia/MyoidaMolluska/Bivalvia/Myoida

PholadidaePholadidae (Piddocks) (Piddocks)

(Go Back)

Family: PholadidaeFamily: Pholadidae(belongs to Order: (belongs to Order: MyoidaMyoida))

Major Genera and speciesMajor Genera and species Cyrtopleura Cyrtopleura

– costada (Angel Wing)costada (Angel Wing)

(Go Back)

Order: MytiloidaOrder: Mytiloida(belongs to Class: (belongs to Class: BivalviaBivalvia))

Major families belonging to Major families belonging to Molluska/Bivalvia/MytiloidaMolluska/Bivalvia/Mytiloida

MytilidaeMytilidae (Mussels) (Mussels) PinnidaePinnidae (Pen shells) (Pen shells)

(Go Back)

Family: MytilidaeFamily: Mytilidae(belongs to Order: (belongs to Order: MytiloidaMytiloida))

Major Genera and speciesMajor Genera and species Geukensia Geukensia

– demissa (Atlantic Ribbed Mussel)demissa (Atlantic Ribbed Mussel)

Ischadium Ischadium – recurvum (Hooked Mussel)recurvum (Hooked Mussel)

Modiolus Modiolus – americanus (Tulip Mussel)americanus (Tulip Mussel)

(Go Back)

Family: PinnidaeFamily: Pinnidae(belongs to Order: (belongs to Order: MytiloidaMytiloida))

Major Genera and speciesMajor Genera and species Altrina Altrina

– rigida (Stiff Pen Shell)rigida (Stiff Pen Shell)

(Go Back)

Order: PterioidaOrder: Pterioida(belongs to Class: (belongs to Class: BivalviaBivalvia))

Major families belonging to Major families belonging to Molluska/Bivalvia/PterioidaMolluska/Bivalvia/Pterioida

AnomiidaeAnomiidae (Jingle shells) (Jingle shells) OstreidaeOstreidae (Oysters) (Oysters) PectinidaePectinidae (Scallops) (Scallops) PlicatulidaePlicatulidae (Kitten’s Paws) (Kitten’s Paws)

(Go Back)

Family: AnomiidaeFamily: Anomiidae(belongs to Order: (belongs to Order: PterioidaPterioida))

Major Genera and speciesMajor Genera and species Anomia Anomia

– simplex (Common Jingle Shell)simplex (Common Jingle Shell)

(Go Back)

Family: OstreidaeFamily: Ostreidae(belongs to Order: (belongs to Order: PterioidaPterioida))

Major Genera and speciesMajor Genera and species Crassostrea Crassostrea

– virginica (Eastern Oyster)virginica (Eastern Oyster)

Ostrea Ostrea – equestris (Crested Oyster)equestris (Crested Oyster)

(Go Back)

Family: PectinidaeFamily: Pectinidae(belongs to Order: (belongs to Order: PterioidaPterioida))

Major Genera and speciesMajor Genera and species Argopecten Argopecten

– gibbus (Calico Scallop)gibbus (Calico Scallop)

(Go Back)

Family: PlicatulidaeFamily: Plicatulidae(belongs to Order: (belongs to Order: PterioidaPterioida))

Major Genera and speciesMajor Genera and species Plicatula Plicatula

– gibbosa (Kitten’s Paw)gibbosa (Kitten’s Paw)

(Go Back)

Order: UnionoidaOrder: Unionoida(belongs to Class: (belongs to Class: BivalviaBivalvia))

Major families belonging to Major families belonging to Molluska/Bivalvia/UnionoidaMolluska/Bivalvia/Unionoida

NONE OF OUR SAMPLES BELONG TO NONE OF OUR SAMPLES BELONG TO UnionoidaUnionoida..

(Go Back)

Order: VeneroidaOrder: Veneroida(belongs to Class: (belongs to Class: BivalviaBivalvia))

Major families belonging to Molluska/Bivalvia/VeneroidaMajor families belonging to Molluska/Bivalvia/Veneroida CardiidaeCardiidae (Cockles) (Cockles) CarditidaeCarditidae (Carditas) (Carditas) CultellidaeCultellidae (Razor clams) (Razor clams) DonacidaeDonacidae (Donaxes) (Donaxes) LucinidaeLucinidae (Lucines) (Lucines) MactridaeMactridae (Surf clams) (Surf clams) PetricolidaePetricolidae (Petricolas) (Petricolas) SemelidaeSemelidae (Semeles) (Semeles) SolecurtidaeSolecurtidae (Razor clams) (Razor clams) SolenidaeSolenidae (Razor clams) (Razor clams) TellinidaeTellinidae (Tellins) (Tellins) VeneridaeVeneridae (Venus clams) (Venus clams)

(Go Back)

Family: CardiidaeFamily: Cardiidae(belongs to Order: (belongs to Order: VeneroidaVeneroida))

Major Genera and speciesMajor Genera and species Dinocardium Dinocardium

– robustum (Giant Atlantic Cockle)robustum (Giant Atlantic Cockle)

Trachycardium Trachycardium – egmontianum (Prickly Cockle)egmontianum (Prickly Cockle)– muricatum (Yellow Cockle)muricatum (Yellow Cockle)

(Go Back)

Family: CarditidaeFamily: Carditidae(belongs to Order: (belongs to Order: VeneroidaVeneroida))

Major Genera and speciesMajor Genera and species Carditamera Carditamera

– floridana (Broad-ribbed Cardita)floridana (Broad-ribbed Cardita)

(Go Back)

Family: Cultellidae Family: Cultellidae (belongs to Order: (belongs to Order: VeneroidaVeneroida))

Major Genera and speciesMajor Genera and species Ensis Ensis

– directus (Common Razor Clam)directus (Common Razor Clam)

(Go Back)

Family: Donacidae Family: Donacidae (belongs to Order: (belongs to Order: VeneroidaVeneroida))

Major Genera and speciesMajor Genera and species Donax Donax

– variabilis (Florida Coquina)variabilis (Florida Coquina)

(Go Back)

Family: Lucinidae Family: Lucinidae (belongs to Order: (belongs to Order: VeneroidaVeneroida))

Major Genera and speciesMajor Genera and species Divaricella Divaricella

– quadrisulcata (Crosshatched Lucine)quadrisulcata (Crosshatched Lucine)

Parvilucina Parvilucina – multilineata (Multi-lined Lucine)multilineata (Multi-lined Lucine)

Phacoides Phacoides – pectinatus (Thick Lucine)pectinatus (Thick Lucine)

Pseudomiltha Pseudomiltha – floridana (Florida Lucine)floridana (Florida Lucine)

(Go Back)

Family: Mactridae Family: Mactridae (belongs to Order: (belongs to Order: VeneroidaVeneroida))

Major Genera and speciesMajor Genera and species Mactra Mactra

– fragilis (Fragile Atlantic Mactra)fragilis (Fragile Atlantic Mactra)

Mulinia Mulinia – lateralis (Dwarf Surf Clam)lateralis (Dwarf Surf Clam)

Raeta Raeta – plicatella (Channeled Duck Clam)plicatella (Channeled Duck Clam)

(Go Back)

Family: Petricolidae Family: Petricolidae (belongs to Order: (belongs to Order: VeneroidaVeneroida))

Major Genera and speciesMajor Genera and species Petricola Petricola

– pholadiformis (False Angel Wing)pholadiformis (False Angel Wing)

(Go Back)

Family: Semelidae Family: Semelidae (belongs to Order: (belongs to Order: VeneroidaVeneroida))

Major Genera and speciesMajor Genera and species Cumingia Cumingia

– tellinoides (Tellinlike Cumingia)tellinoides (Tellinlike Cumingia)

(Go Back)

Family: Solecurtidae Family: Solecurtidae (belongs to Order: (belongs to Order: VeneroidaVeneroida))

Major Genera and speciesMajor Genera and species Tagelus Tagelus

– plebeius (Stout Tagelus)plebeius (Stout Tagelus)

(Go Back)

Family: Solenidae Family: Solenidae (belongs to Order: (belongs to Order: VeneroidaVeneroida))

Major Genera and speciesMajor Genera and species Solen Solen

– viridis (Green Jackknife Clam)viridis (Green Jackknife Clam)

(Go Back)

Family: Tellinidae Family: Tellinidae (belongs to Order: (belongs to Order: VeneroidaVeneroida))

Major Genera and speciesMajor Genera and species Tellina Tellina

– alternata (Alternate Tellin)alternata (Alternate Tellin)– iris (Iris Tellin)iris (Iris Tellin)– sybaritica (Dall’s Dwarf Tellin)sybaritica (Dall’s Dwarf Tellin)– tampaensis (Tampa Tellin)tampaensis (Tampa Tellin)

(Go Back)

Family: Veneridae Family: Veneridae (belongs to Order: (belongs to Order: VeneroidaVeneroida))

Major Genera and speciesMajor Genera and species Chione Chione

– cancellata (Cross-barred Venus)cancellata (Cross-barred Venus)

Dosinia Dosinia – discus (Disk Dosinia)discus (Disk Dosinia)

Macrocallista Macrocallista – numbosa (Sunray Venus)numbosa (Sunray Venus)

Merceneria Merceneria – campechiensis (Southern Quahog)campechiensis (Southern Quahog)

(Go Back)

Class: CephalopodaClass: Cephalopoda(belongs to Phylum: (belongs to Phylum: MolluskaMolluska))

This class contains the squids, This class contains the squids, octopusesoctopuses and cuttlefish. and cuttlefish. Orientation of the body differs from most mollusks in that the ventral region Orientation of the body differs from most mollusks in that the ventral region

(belly-side) is now anterior (up front) and the visceral mass is now the (belly-side) is now anterior (up front) and the visceral mass is now the functional posterior (in back) end of the animal. This change in orientation has functional posterior (in back) end of the animal. This change in orientation has implications for sensory function and cephalopod implications for sensory function and cephalopod locomotionlocomotion..

Also differs from other mollusks in the alteration of much of the original foot into Also differs from other mollusks in the alteration of much of the original foot into a series of large prehensile a series of large prehensile tentaclestentacles or arms at the anterior end which now or arms at the anterior end which now surround the head.surround the head.

Most either have an internal shell, like a squid. Some lack a shell, like an Most either have an internal shell, like a squid. Some lack a shell, like an octopus. All cephalopods are predators, and use jaws and radula to crush and octopus. All cephalopods are predators, and use jaws and radula to crush and rip prey. Like bivalves, they are able to move by taking water into the mantle rip prey. Like bivalves, they are able to move by taking water into the mantle cavity and shooting it back out. cavity and shooting it back out.

They have large brains enclosed in cartilaginous brain cases. Because of a They have large brains enclosed in cartilaginous brain cases. Because of a developed brain, good developed brain, good eye sighteye sight, and good sense organs, they are considered , and good sense organs, they are considered to be one of the most advanced invertebrates.to be one of the most advanced invertebrates.

NONE OF OUR SAMPLES BELONG TO NONE OF OUR SAMPLES BELONG TO CEPHALOPODACEPHALOPODA..(Go Back)(Go Back)

OctopusOctopus(a Cephalopod)(a Cephalopod)

(Go Back)

Eye of an OctopusEye of an Octopus

(Go Back)

Cephalopod LocomotionCephalopod Locomotion Most cephalopods, except the more sedentary octopus, are active Most cephalopods, except the more sedentary octopus, are active

animals, which swim by means of jet propulsion, during which water is animals, which swim by means of jet propulsion, during which water is rapidly forced out of the mantle cavity through the siphon by the rapidly forced out of the mantle cavity through the siphon by the contraction of the muscles in the mantle wall. contraction of the muscles in the mantle wall.

Squids, besides being the fastest cephalopods, are also the fastest Squids, besides being the fastest cephalopods, are also the fastest swimmers of all aquatic invertebrates. Their long tapered bodies are swimmers of all aquatic invertebrates. Their long tapered bodies are ideally streamlined, and the lateral fins provide stability. The 'flying ideally streamlined, and the lateral fins provide stability. The 'flying squids' are particularly interesting. These have highly developed fin squids' are particularly interesting. These have highly developed fin vanes and may shoot out of the water and glide for some distance.vanes and may shoot out of the water and glide for some distance.

(Go Back)(Go Back)

Cephalopod TentaclesCephalopod Tentacles Squids and cuttlefish have ten appendages comprised of Squids and cuttlefish have ten appendages comprised of

eight arms and two long tentacles possessing numerous eight arms and two long tentacles possessing numerous cup-shaped, rimmed suckers. The tentacles are used to cup-shaped, rimmed suckers. The tentacles are used to capture prey, which is held by the tentacles and their capture prey, which is held by the tentacles and their suckers as it is pulled towards the mouth. suckers as it is pulled towards the mouth.

The mouth lies at the base of the tentacles and possesses The mouth lies at the base of the tentacles and possesses a parrot-like beak.a parrot-like beak.

The octopuses have eight long tentacles (sometimes called The octopuses have eight long tentacles (sometimes called arms) each with a row of suckers on the inner surface.arms) each with a row of suckers on the inner surface.

(Go Back)(Go Back)

Class: GastropodaClass: Gastropoda(belongs to Phylum: (belongs to Phylum: MolluskaMolluska))

Gastropods are the most successful group of molluscs not only in terms of the number of Gastropods are the most successful group of molluscs not only in terms of the number of species, but also in the wide range of habitat in which they may be found. Marine species species, but also in the wide range of habitat in which they may be found. Marine species have become adapted to living on all types of substratum and some have even adopted have become adapted to living on all types of substratum and some have even adopted a pelagic (living in open water either at the surface or at intermediate depths) existence. a pelagic (living in open water either at the surface or at intermediate depths) existence. Others have successfully invaded all types of freshwater habitat as well as the land.Others have successfully invaded all types of freshwater habitat as well as the land.

A univalve, generally spirally A univalve, generally spirally coiled shell coiled shell is present in the majority of gastropods. The is present in the majority of gastropods. The most significant change from the hypothetical ancestral mollusc that the gastropods have most significant change from the hypothetical ancestral mollusc that the gastropods have undergone during their phylogeny is the process of undergone during their phylogeny is the process of torsiontorsion.. The third important feature of The third important feature of gastropods is the greater degree of head development or cephalizationgastropods is the greater degree of head development or cephalization..

Class Gastropoda is the largest group of mollusks, with between 40,000 and 75,000 Class Gastropoda is the largest group of mollusks, with between 40,000 and 75,000 species. These are also the only mollusks that live on land. Gastropods, like species. These are also the only mollusks that live on land. Gastropods, like Class: Class: SchapodaSchapoda, lack gills, and use the mantle as a makeshift lung for extracting oxygen and , lack gills, and use the mantle as a makeshift lung for extracting oxygen and breathing. Most species have coiled shells, and this class has evolved tentacles and breathing. Most species have coiled shells, and this class has evolved tentacles and eyes. This class includes marine animals like the sea slug and terrestrial animals like the eyes. This class includes marine animals like the sea slug and terrestrial animals like the slug and snail. slug and snail.

NEXTNEXT

Gastropod Shell CoilingGastropod Shell Coiling One characteristic feature of the majority of gastropods is that the ancestral One characteristic feature of the majority of gastropods is that the ancestral

conical shell has now become coiled. This process was a separate evolutionary conical shell has now become coiled. This process was a separate evolutionary event and was not connected with torsion, indeed there is fossil evidence that it event and was not connected with torsion, indeed there is fossil evidence that it may have preceded it. In the most primitive gastropods, shell coiling was may have preceded it. In the most primitive gastropods, shell coiling was planospiral, whereas in the more advanced forms coiling is asymmetrical. planospiral, whereas in the more advanced forms coiling is asymmetrical.

In this type of shell, the shell axis has now become shifted slightly to improve In this type of shell, the shell axis has now become shifted slightly to improve weight distribution and in modern forms it is carried obliquely to the long axis of weight distribution and in modern forms it is carried obliquely to the long axis of the body, and its weight is now borne by the widest part of the foot, near the the body, and its weight is now borne by the widest part of the foot, near the middle of the body. middle of the body.

The symmetrical shell and the angle at which it is carried has caused some The symmetrical shell and the angle at which it is carried has caused some occlusion of the mantle cavity on the right side, which in turn has resulted in the occlusion of the mantle cavity on the right side, which in turn has resulted in the reduction or loss of the right ctenidium and the associated auricle. The shape reduction or loss of the right ctenidium and the associated auricle. The shape of a gastropod's shell depends greatly on its habitat and its mode of life. of a gastropod's shell depends greatly on its habitat and its mode of life.

(Go Back)(Go Back)

Gastropod TorsionGastropod Torsion The most significant change from the hypothetical ancestral mollusc The most significant change from the hypothetical ancestral mollusc

that the gastropods have undergone during their phylogeny is the that the gastropods have undergone during their phylogeny is the process of torsion. During torsion, most of the body behind the head, process of torsion. During torsion, most of the body behind the head, including the mantle, mantle cavity and visceral mass are twisted anti-including the mantle, mantle cavity and visceral mass are twisted anti-clockwise through 180 degrees. clockwise through 180 degrees.

Not all living gastropods are torted, however. Some groups have Not all living gastropods are torted, however. Some groups have undergone undergone detorsiondetorsion during which the mantle cavity has moved to during which the mantle cavity has moved to within 90 degrees of its original position, occasionally even 120 within 90 degrees of its original position, occasionally even 120 degrees in some species, and has resulted in some rearrangement of degrees in some species, and has resulted in some rearrangement of the internal anatomy.the internal anatomy.

(GO BACK)(GO BACK)

Orders belonging toOrders belonging toClass: GastropodaClass: Gastropoda

5 major orders belonging to 5 major orders belonging to Molluska/GastropodaMolluska/Gastropoda

ArchaeogastropodaArchaeogastropoda CaenogastropodaCaenogastropoda HeterogastropodaHeterogastropoda NudibranchiaNudibranchia SigmurethraSigmurethra

(Go Back)(Go Back)

Order: Archaeogastropoda Order: Archaeogastropoda (belongs to Class: (belongs to Class: GastropodaGastropoda))

Major families belonging to Major families belonging to Molluska/Gastropoda/ArchaeogastropodaMolluska/Gastropoda/Archaeogastropoda

TurbinidaeTurbinidae (Turban shells) (Turban shells)

(Go Back)

Family: Turbinidae Family: Turbinidae (belongs to Order: (belongs to Order: ArchaeogastropodaArchaeogastropoda))

These shells are turban- or top-shaped, or These shells are turban- or top-shaped, or occasionally flattened. They are thick, occasionally flattened. They are thick, sculptured or smooth, with a rounded sculptured or smooth, with a rounded aperture that is pearly within.aperture that is pearly within.

Major Genera and speciesMajor Genera and species TurboTurbo

– castanea (Chestnut Turban)castanea (Chestnut Turban)

(Go Back)

Order: Caenogastropoda Order: Caenogastropoda (belongs to Class: (belongs to Class: GastropodaGastropoda))

Major families belonging to Major families belonging to Molluska/Gastropoda/CaenogastropodaMolluska/Gastropoda/Caenogastropoda

Conidae (Cone shells)Conidae (Cone shells) Crepidulidae (Cup-and-saucer shells or slipper shells)Crepidulidae (Cup-and-saucer shells or slipper shells) Fasciolariidae (Spindle shells)Fasciolariidae (Spindle shells) Ficidae (Fig shells)Ficidae (Fig shells) Melongenidae (Crown conch shells)Melongenidae (Crown conch shells) Muricidae (Murex shells)Muricidae (Murex shells) Nassariidae (Dog whelk or Basket whelk shells)Nassariidae (Dog whelk or Basket whelk shells) Naticidae (Moon shells)Naticidae (Moon shells) Olividae (Olive shells)Olividae (Olive shells) Terebridae (Auger shells)Terebridae (Auger shells)

(Go Back)

Family: Conidae Family: Conidae (belongs to Order: (belongs to Order: CaenogastropodaCaenogastropoda))

These shells are cone-shaped (narrow at These shells are cone-shaped (narrow at bottom, wide at shoulder) with a low spire.bottom, wide at shoulder) with a low spire.

Major Genera and speciesMajor Genera and species ConusConus

– floridanus (Florida Cone)floridanus (Florida Cone)

(Go Back)

Family: Crepidulidae Family: Crepidulidae (belongs to Order: (belongs to Order: CaenogastropodaCaenogastropoda))

These shells are either cap-shaped or These shells are either cap-shaped or slipper-shaped with a shelf underneath.slipper-shaped with a shelf underneath.

Major Genera and speciesMajor Genera and species CrepidulaCrepidula

– convexa (Convex Slipper Shell)convexa (Convex Slipper Shell)– fornicata (Atlantic Slipper Shell)fornicata (Atlantic Slipper Shell)– plana (Eastern White Slipper Shell)plana (Eastern White Slipper Shell)

(Go Back)

Family: Fasciolariidae Family: Fasciolariidae (belongs to Order: (belongs to Order: CaenogastropodaCaenogastropoda))

These shells are usually large and are These shells are usually large and are generally spindle-shaped.generally spindle-shaped.

Major Genera and speciesMajor Genera and species FasciolariaFasciolaria

– tulipa (True Tulip)tulipa (True Tulip)

(Go Back)

Family: Ficidae Family: Ficidae (belongs to Order: (belongs to Order: CaenogastropodaCaenogastropoda))

These shells are thin and have the shape of These shells are thin and have the shape of a large fig or a slender pear.a large fig or a slender pear.

Major Genera and speciesMajor Genera and species FicusFicus

– communis (Common Fig Shell)communis (Common Fig Shell)

(Go Back)

Family: Melongenidae Family: Melongenidae (belongs to Order: (belongs to Order: CaenogastropodaCaenogastropoda))

These shells are usually large with a large These shells are usually large with a large body whorl and a low to elongately conical body whorl and a low to elongately conical spire.spire.

Major Genera and speciesMajor Genera and species BusyconBusycon

– canaliculatum (Channeled Whelk)canaliculatum (Channeled Whelk)– carica (Knobbed Whelk)carica (Knobbed Whelk)– contrarium (Lightning Whelk)contrarium (Lightning Whelk)

(Go Back)

Family: Muricidae Family: Muricidae (belongs to Order: (belongs to Order: CaenogastropodaCaenogastropoda))

These shells usually have spines, but some These shells usually have spines, but some have strong ribs instead.have strong ribs instead.

Major Genera and speciesMajor Genera and species EupleuraEupleura

– caudatacaudata (Thick-lipped Drill) (Thick-lipped Drill)

(Go Back)

Thick-lipped DrillThick-lipped Drill

(Go Back)

Family: Nassariidae Family: Nassariidae (belongs to Order: (belongs to Order: CaenogastropodaCaenogastropoda))

These are small snail shells that are usually These are small snail shells that are usually elongate and conical. elongate and conical.

Major Genera and speciesMajor Genera and species NassariusNassarius

– obsoletus (Eastern Mud Whelk)obsoletus (Eastern Mud Whelk)– trivittatus (New England Basket Whelk)trivittatus (New England Basket Whelk)

(Go Back)

Family: Naticidae Family: Naticidae (belongs to Order: (belongs to Order: CaenogastropodaCaenogastropoda))

These shells are round to broadly ovate. These shells are round to broadly ovate. They are usually smooth with short spires.They are usually smooth with short spires.

Major Genera and speciesMajor Genera and species NeveritaNeverita

– duplicata (Shark’s Eye)duplicata (Shark’s Eye)

SinumSinum– perspectivum (Common Atlantic Baby’s Ear)perspectivum (Common Atlantic Baby’s Ear)

(Go Back)

Family: Olividae Family: Olividae (belongs to Order: Caenogastropoda)(belongs to Order: Caenogastropoda)

These shells are elongate and cylindrical. These shells are elongate and cylindrical. They have a narrow aperture and a small They have a narrow aperture and a small conical spire.conical spire.

Major Genera and speciesMajor Genera and species OlivaOliva

– sayanasayana (Lettered Olive) (Lettered Olive)

(Go Back)

Lettered OliveLettered Olive

(Go Back)

Family: Terebridae Family: Terebridae (belongs to Order: Caenogastropoda)(belongs to Order: Caenogastropoda)

These shells are high, narrow, and elongate, These shells are high, narrow, and elongate, with numerous whorls. The surface may be with numerous whorls. The surface may be smooth or have spiral grooves.smooth or have spiral grooves.

Major Genera and speciesMajor Genera and species HastulaHastula

– cinerea (Gray Atlantic Auger)cinerea (Gray Atlantic Auger)

TerebraTerebra– dislocatadislocata (Common American Auger) (Common American Auger)

(Go Back)

Common American AugerCommon American Auger

(Go Back)

Order: Heterogastropoda Order: Heterogastropoda (belongs to Class: (belongs to Class: GastropodaGastropoda))

Major families belonging to Major families belonging to Molluska/Gastropoda/HeterogastropodaMolluska/Gastropoda/Heterogastropoda

EpitoniidaeEpitoniidae (Wentletrap shells) (Wentletrap shells)

(Go Back)

Family: Epitoniidae Family: Epitoniidae (belongs to Order: (belongs to Order: HeterogastropodaHeterogastropoda))

Almost all of these shells are white with Almost all of these shells are white with convex whorls and roundish apertures.convex whorls and roundish apertures.

Major Genera and speciesMajor Genera and species EpitoniumEpitonium

– angulatumangulatum (Angulate Wentletrap) (Angulate Wentletrap)

(Go Back)

Angulate WentletrapAngulate Wentletrap

(Go Back)

Order: Nudibranchia Order: Nudibranchia (belongs to Class: (belongs to Class: GastropodaGastropoda))

Major families belonging to Major families belonging to Molluska/Gastropoda/NudibranchiaMolluska/Gastropoda/Nudibranchia

NONE OF OUR SAMPLES BELONG TO NONE OF OUR SAMPLES BELONG TO NudibranchiaNudibranchia..

(Go Back)

Order: SigmurethraOrder: Sigmurethra(belongs to Class: (belongs to Class: GastropodaGastropoda))

Major families belonging to Major families belonging to Molluska/Gastropoda/SigmurethraMolluska/Gastropoda/Sigmurethra

NONE OF OUR SAMPLES BELONG TO NONE OF OUR SAMPLES BELONG TO SigmurethraSigmurethra..

(Go Back)

Class: MonoplascophoraClass: Monoplascophora(belongs to Phylum: (belongs to Phylum: MolluskaMolluska))

This is a very small group of organisms that has been known for only a short time. This is a very small group of organisms that has been known for only a short time.

Originally thought to exist only in the fossil record, they were rediscovered in 1952, and Originally thought to exist only in the fossil record, they were rediscovered in 1952, and there are now about ten known species, all of which are deep ocean dwellers. This class there are now about ten known species, all of which are deep ocean dwellers. This class is characterized by having an unhinged shell. is characterized by having an unhinged shell.

The animals possess a large flattened foot surrounded by the pallial groove, in which are The animals possess a large flattened foot surrounded by the pallial groove, in which are situated 5 or 6 pairs of situated 5 or 6 pairs of gillsgills. Internally, the animals possess 8 pairs of dorso-ventral pedal . Internally, the animals possess 8 pairs of dorso-ventral pedal retractor muscles, a feature that is known to have existed in fossil forms. retractor muscles, a feature that is known to have existed in fossil forms.

They also show a number of distinct characteristics such as the possession of 6 pairs of They also show a number of distinct characteristics such as the possession of 6 pairs of nephridia (excretory organ having function of kidney in invertebrates) lying in the pallial nephridia (excretory organ having function of kidney in invertebrates) lying in the pallial groove. The coelom consists of the pericardial cavity and the cavity of the two pairs of groove. The coelom consists of the pericardial cavity and the cavity of the two pairs of gonads. gonads.

NONE OF OUR SAMPLES BELONG TO NONE OF OUR SAMPLES BELONG TO MONOPLASCOPHORAMONOPLASCOPHORA. .

(Go Back)(Go Back)

Structure of Structure of Neopolina Neopolina (a Monoplascophoran)(a Monoplascophoran)

(Go Back)

Class: PolyplacophoraClass: Polyplacophora(belongs to Phylum: (belongs to Phylum: MolluskaMolluska))

This class includes the This class includes the chitonschitons. .

The shells of chitons are characteristically divided into 8 transverse, overlapping shell The shells of chitons are characteristically divided into 8 transverse, overlapping shell plates or valves. The foot is greatly expanded, forming a large flattened sole which is plates or valves. The foot is greatly expanded, forming a large flattened sole which is used not only for locomotion but also for maintaining firm contact with the rock surface. used not only for locomotion but also for maintaining firm contact with the rock surface. Adhesion is effected mainly by the foot under normal conditions but, when the animal is Adhesion is effected mainly by the foot under normal conditions but, when the animal is disturbed, the girdle (the soft part surrounding the shell) is also clamped down tightly disturbed, the girdle (the soft part surrounding the shell) is also clamped down tightly onto the rock surface. onto the rock surface.

Chitons feed on small particles of algae on the rock surface which are scraped off using Chitons feed on small particles of algae on the rock surface which are scraped off using the radula. Feeding normally takes place when covered by the tide, and they tend to be the radula. Feeding normally takes place when covered by the tide, and they tend to be most active when immersed at night. They are normally inactive animals and move only most active when immersed at night. They are normally inactive animals and move only to feed, but often show 'homing behaviour', which enables them to return to the same to feed, but often show 'homing behaviour', which enables them to return to the same area of rock.area of rock.

NONE OF OUR SAMPLES BELONG TO NONE OF OUR SAMPLES BELONG TO POLYPLACOPHORAPOLYPLACOPHORA. .

(Go Back)(Go Back)

Chiton glaucusChiton glaucus (a Polyplacophoran)(a Polyplacophoran)

(Go Back)

Class: Schapoda Class: Schapoda (belongs to Phylum: (belongs to Phylum: MolluskaMolluska))

One of the smaller classes of molluscs, the scaphopods, or One of the smaller classes of molluscs, the scaphopods, or tusk shellstusk shells, are burrowing, , are burrowing, marine molluscs having a tubular tusk or tooth-shaped shell which is open at both ends. marine molluscs having a tubular tusk or tooth-shaped shell which is open at both ends. They are elongated along the anterior-posterior axis and live buried in the sand, head They are elongated along the anterior-posterior axis and live buried in the sand, head downwards, with the body steeply inclined. Water enters and leaves the mantle cavity via downwards, with the body steeply inclined. Water enters and leaves the mantle cavity via the posterior aperture.the posterior aperture.

The head is very reduced and lacks eyes, but is surrounded by numerous thread-like The head is very reduced and lacks eyes, but is surrounded by numerous thread-like tentacles or captacula. The captacula possess an adhesive knob at their tip and are used tentacles or captacula. The captacula possess an adhesive knob at their tip and are used to gather small particles of food present in the sand and pass them to the mouth. to gather small particles of food present in the sand and pass them to the mouth.

Scaphopods are found mainly in the deep sea, but a few species occur in shallow Scaphopods are found mainly in the deep sea, but a few species occur in shallow water.This class is unusual because it lacks both gills and heart. Therefore, gas water.This class is unusual because it lacks both gills and heart. Therefore, gas exchange occurs in the mantle and blood is circulated by contractions of the foot. exchange occurs in the mantle and blood is circulated by contractions of the foot.

NONE OF OUR SAMPLES BELONG TO NONE OF OUR SAMPLES BELONG TO SCHAPODASCHAPODA. .

(Go Back)(Go Back)

Graptacme eboreaGraptacme eborea (a Shapodan)(a Shapodan)

(Go Back)