MolluscanSucces

Prepared by: Jerry D. Taay

Evolutionary PerspectiveOctopuses, squid and cuttlefish are some of the

invertebrate world’s most adept predators. Predatory lifestyle have result in the evolution of large brains( by invertebrates standards ), complex sensory structures( by any standards ), rapid locomotion, gasping tentacles, and tearing mouthparts.

Cephalopods now includes only about 550 speciesZoologist do not know why cephalopods have decline

so dramatically.Vertebrates may have outcompeted cephalopods

because the vertebrates (bony fish) acquired active, predatory lifestyle.

What is Molluscan/ Mollusc?Came from the Latin word molluscus mean

Soft.They are TriploblasticConsider second largest animal phylum.It includes herbivores, carnivores, filter

feeder and parasite.An invertebrates for a large phylum that

includes snail, slugs, mussels, and octopuses.They have soft, segmented body and live in

aquatic or damp habitat, and most kinds have an external Calcareous Shell.

Known as cone shells deliver a painful sting that can be a lethal to human.

Body Parts of Mollusc/Mollusk.

Characteristics of Phylum Mollusc.Body of two parts Head-Foot and Visceral mass.Mantle that secretes a calcareous shell that

covers the visceral mass.Mantle Cavity functions in Excretion, Gas

exchange, elimination of digestive waste and release of reproductive products.

Bilateral symmetry.Protostome characteristics, including

trochophore larvae, spiral cleavage, and schizocoelous coelom formation.

Coelom reduce to cavities surrounding the heart, nephridia, and gonads.

Open circulatory system in all but on class (Cephalopods).

Radula usually present and use in scraping food.

The Three main body region of a Mollusc/ Mollusk

Head-Foot Is the elongated w/ an anterior head containing the mouth and certain nervous and sensory structure, and an elongated foot, used for attachments and locomotion.

Visceral Mass Contains the organs of digestion, circulation, reproduction, and excretion and is positioned dorsal to the head-foot. It includes mantle that cover the visceral mass and may secrete a shell.

Mantle Usually attaches to the visceral mass, enfolds most of the body, and may secrete a shell that overlies the mantle.

Three layers of ShellOuter layer outer margin that secrete

protein called Periostracum( is a thin organic coating or “skin” w/c is the outermost layer of the shell of many shelled animals).

Middle Layer is the thickest of the three layer and consist of calcium carbonate mixed with organic materials called Prismatic Layer ( producing tissues and a screen and consisting of calcite or aragonite).

Inner Layer forms a thin sheets of calcium carbonate altering with organic matter called Nacreous Layer ( also known as Mother of Pearl, is an organic-inorgani ccomposite material produce by some mollusks as an inner shell layer; it is also what makes up the outer coating of the pearl).

Inner layer

Classification of MolluscaClass Gastropods ( G. gastro, stomach and podos,

foot).The large stand most divers of the mollusc classes and it includes the snails, limpers and slugs, conch, whelks and nudibrach.

Usually found on marine habitats and they are herbivores.

They have an elongated, flattened foot and a one-piece coiled shell that protects the visceral mass

Gastropods

Land snail

Land snailSuch as Helix aspersaThey are HermaphroditicThey have three obvious division of the

body: 1.Head a flat long 2. Muscular foot 3. Visceral mass surrounded by shell and provide protection from the predator and prevent desiccation (drying out).

Nudibranch Comes from the L. nudus, naked and

brankhia, gills.Aquatic Gastropods that have a gill in

their mantle cavity richly supplied with blood vessels, functions as a lungs when air is moved in and out through respiratory pores.

Group of soft bodied, marine gastropods mollusks w/c shed their shell after their larval stage

Nudibranch

LimpetsOften found living on hard surface in

the intertidal zone.Can found on in the places rich in

algae on most rocky shores.

They are very hardy species and are even found on the stormiest shore all year round

Limpet Structure

Whelks Is the common name that is applied

to a various kinds of sea snail many of which have historically been used, or are still used, by humans for food.

They also known as welkor evenwilks. The word originated from the from the Proto-Germanic root “weluka”, meaning toturn or revolve.

Whelks

Conch A tropical marine mollusks with a

spiral shell that may bear long projection and have a flared lip.

They also called ConchaIs a common name that is applied to

a number medium to a large-sized sea snail or other shells.

Conch

Torsion One of the most significant modifition of the

molluscan body forms in gastropods occurs early in development.

Is a 180, counter clockwise twisting of the visceral mass, mantle, and mantle cavity.

Torsion portions the gills, anus, and openings from the excretory and reproductive system just behind the head and nerve cords, and

twists the digestive tract into a U shape.It is the action of being twisting or the

state of being twisted, especially of one of an object relative to the another.

Torsion Before Torsion After Torsion

Than You for Your ListeningA GROUP REPORT IN

ZOOLOGY OF:Jerry Deleon Taay

Bachelor of Secondary Education major in Biological Science.

EMA EMITS COLLEGE PHILIPPINES

Ryan Florencondia(Zoology Instructor)