Ch. 33 Introduction to Invertebrates (Mollusca)

about_of all living species of molluscs are gastropods

-3/4

How many known species of mollusc are? what is the place of the mollusca phylum of most diverse?

-93,000 -The second

ammonites

-A member of a group of shelled cephalopods that were important marine predators for hundreds of millions of years until their extinction at the end of the Cretaceous period (65.5 million years ago)

mantle cavity

-A water-filled chamber that houses the gills, anus, and excretory pores of molluscs

How the snails are capable of living on earth?

-lack gills -the lining of their mantle cavity functions as lungs, exchanging respiratory gases with the air

pearls

-made by shells to trap the sand to make it less irritated

The_covers the visceral mass of cephalopods, but the shell is generally_

-mantle -reduced and internal (in most species) or missing altogether (some culttlefishes and octopuses)

Many molluscs also have a water-filled_ and feed using a rasplike _

-mantle cavity -radula

why did the ammniotes got extinct?

-meteor hit the earth (mass extinction period)

how the water flows in a bivalve?

Enters through the incurrent siphon, passes over the gills, and then exists the mantle cavity through and excurrent siphon

feeding bivalvia

Gills - filter feeder

locomotion (all have swimming larvae) gastropoda

Glide on foot (swim)

what animal group has the largest number of recent extinctions?

Molluscs are the animal group with the largest number of recent extinctions

what are the habitats that mollusc live?

Most molluscs are marine, though some inhabit fresh water and some snails and slugs are terrestrial

sinuses

body cavities where hemolymph arrives

how does the trochopore moves?

ciliated movement

what is the name of the largest squid known?

giant squid Architeuthis dux (mantle 2.25 cm long and total length of 18 m) -it had large suckers and small teeth on its tentacles

gas exchange bivalvia

gills

gas exchange cephalopoda

gills

gas exchange gastropoda

gills

The mantle cavity of a bivalve contains _

gills that are used for feeding as well as gas exchange

where is the siphon located? (ventral or dorsal)

ventral side

Bivalves

-Bivalves are aquatic -include many species of clams, oysters, mussels, and scallops -They have a shell divided into two halves drawn together by adductor muscles (to protection) -Some bivalves have eyes and sensory tentacles along the edge of their mantle -No distinct head -radula lost -Suspension feeders -The mantle cavity contains gills that are used for gas exchange and feeding

Cephalopods

-Cephalopods - head -foot -Carnivores with beak-like jaws surrounded by tentacles with suckers (modified foot) -Saliva contains poisons -Modified foot forms a siphon -Shell is internal or lost -Closed circulatory system (only mollusc) -Well developed brain and nervous system -Well developed eyes (compound)

Torsion

-Characteristic feature of gastropods -The molluscs visceral mass rotates up to 180 degree -which causes the animal's anus and mantle to end up above its head -torsion is different from the coiling of a shell -Happens during embryonic development

Polyplacophora

-Chitons -oval-shaped marine animals -encased in an armor of eight dorsal plates -They use their foot like a suction cup to grip rock -their radula to scrape algae off the rock surface

venous snails

-Cone snail -Venon is a cocktail of peptides. -Have painkilling properties -the teeth of the radula act as a poison darts that are used to subdue prey -Injects venom

what is the nerve system of mollusks?

-Consists of a nerve ring around the esophagus, from which nerve cords extend

Blue ring octopus

-Contains one of the most potent toxins known - tetrodotoxin -Neurotoxin that blocks nerve impulses -Produced by symbiotic bacteria -Released through the saliva

Blood clamps

-Deadly because the following sickness: -hepatitis A, E, thyphoid, and dysentery

Does the larvae stage is the same, similar, or has not resemblance to the adults stage?

-Does not resemble adult stage (sometimes it does)

Zebra mussels

-From Ukraine -Came to US 1988 -Huge problem: Filter feeders, block and clog (everything they attach to)

Gills

-Gas exchange -Feeding (filter particles and trap them in mucus) -Big surface area -Vascular

who is the number one killer? (10#)

-McDonald's - United States -the result of fast food: high cholesterol, diabetes, heart disease, hyperobesity... -cheap burgers and fries, as deadly as tetrodotoxin or cyanid

what is the sexual orientation of molluscs?

-Most are dioecious (have separate sexes with gonads located in the visceral mass) -but many snails are hermaphrodites

Gastropods

-Most gastropods are marine, but many are freshwater and terrestrial species -The most distinctive characteristic of gastropods is torsion -Most have a single, spiraled shell, where they can retract to protect themselves -Slugs lack a shell or have a reduced shell

Heart (in molluscs)

-Most molluscs have an open circulatory system -The dorsally located heart pumps circulatory fluid called hemolymph through arteries into sinuses (body spaces) -The organs of the mollusc are bathed in hemolymph

All mollusks have a similar body plans which is:

-Muscular foot -Visceral mass -Mantle

Celocant

-No torsion and no foot -Chambered

nautiluses

-One small group of shelled cephalopods (the most primitive), the nautiluses, survives today - the only shelled cephalopods -Fossil evidence - 500 million years -Living fossils -Some extinct species were straight (2.5m) -Two genera survive today Shelled cephalopods called ammonites were common but went extinct at the end of the Cretaceous 65.5 million years ago

what are the major classes of molluscs?

-Polyplacophora (chitons) -Gastropoda (snails and slugs) -Bivalvia (clams, oysters, and other bivalves) -Cephalopoda (squids, octopuses, cuttlefish, and chambered nautiluses)

The life cycle of many molluscs have_(think about the first stage of life)

-The life cycle of many molluscs includes a ciliated larval stage called a trochophore

what are the most threaten groups of molluscs?

-The most threatened groups are: -Freshwater bivalves, including pearl mussels -Terrestrial gastropods, including Pacific island land snails

close circulatory system

-blood flows through vessels and heart -blood remains separate from fluid in the body cavity

how clams can bury themselves?

-clams can pull themselves into the sand or mud, using their muscular food for an anchor,

Cephalopods have

-close circulatory system -sense organs -brain (nerve ganglia in head region)

diagnostic characteristics of molluscs

-foot -mantle (mantle cavity and visceral mass)

what are the uses of radula?

-graze on algae or plants -the predators' radula is modified to boring holes in the shells of other molluscs or for tearing apart prey

cromatic ford

-hability of some cephalopods to change color

_small group of ammniotes survived, which have_shell

-one -spiral

How and who produces pearls?

-pearl mussels and oysters -secretes layers of a lustrous coating around a grain of sand or other small irritant

Mesonychoteuthis hamiltoni

-rare specie of squid that was found in antartica -juvenile age -2.5 m mantle -Had two rows of sharp hooks at the end of its tentacles that can inflict deadly lacerations

are the bivalves sedentary or motile?

-sedentary

what was the ancestor of octopuses and squids?

-shelled molluscs that took up predator lifestyle -the shell was loss in their evolution -ammonites

the cephalopds are the_of all molluscs because_

-smartest -they are predators and move

What species does the phylum mollusca includes?

-snails -slugs -oysters -clams -octopuses -squids

Bionemecry

-solution for nature and for extinction

radula

-strap-like organ -many molluscs feed using it -to scrape up food -Belt of backward-curved teeth repeatedly trusts outward and then retracts into the mouth, scraping and scooping like a backhoe

The muscular foot of cephalopods transformed into

-tentacles -muscular excurrent siphon

How the radula works in the cone snail?

-the teeth of the radula act as a poison darts that are used to subdue prey

what is the distinguish characteristic of gastropods?

-the torsion

In many molluscs the mantle extends beyond_, producing a_

-visceral mass -water-filled chamber (mantle cavity)

Squids dart about drawing_into their mantle cavity and then_. _use this mechanism too to escape from predators

-water -firing a jet of water through the excurrent siphon; they steer by pointing the siphon in different directions -octopuses

how many tentacles does the octopus has?

8

named examples gastropoda

Banana slug

Bivalvia examples

Clams & muscles

characteristics cepahlopoda

Closed circ system, tentacles

nephridium

Excretory organs called nephridia remove metabolic wastes from hemolymph

named examples cephalopoda

Humboldt squid

locomotion (all have swimming larvae) cephalopoda

Propulsion with syphon & fins

feeding gastropoda

Radula

Locomotion (all have swimming larvae) bivalvia

Sessile or swim

characteristics gastropoda

Spiral shell, torsion, foot

Cephalopoda examples

Squid, octopus, nautilus

Feeding cephalopoda

Tentacles & beak

How these molluscs are threaten?

These molluscs are threatened by habitat loss, pollution, and non-native species (human activity)

characterisitcs bivavlvia

Two shells, aductor muscles,

named examples bivalvia

Zebra muscle

mantle

a fold of tissue that drapes over the visceral mass and secretes a shell

what is a living fossil?

an specie that has fossil records but still exists in our time (extend)

what phylum is the most diverse?

arthopods

how does gastropods move?

at a snail's pace by a rippling motion of their foot of by means of cilia -Often leaving a trail of slime in their wake

The molluscs that does not have radula have a

beak

what does the radula is made of?

calcium carbonate

who is the only mollusc who has close circulatory system?

cephalopods

what is the key characteristic of the cephalopods?

close circulatory system

Mollusks are acelomates, coelomates, or pseudocoelomates?

coelomates

Most molluscs secrete a_

hard protective shell made of calcium carbonate

what does slugs, squids, and octopuses have?

have a reduced internal shell made of calcium carbonate or have lost their shell completely during their evolution

what is the fluid that is pump throughout the body (like blood in humans)?

hemolymph

pen

internal shell that is found within cephalopods (squid)

visceral mass contains

most of the internal organs

muscular foot is usually used for

movement

Does mollusc have open or close circulatory system? (most of them)

open

what is the function of the siphon?

propulsion

All molluscs are_

soft body

what is the meaning of mollusc?

soft body

Scallops can_(movement)

skitter along the seafloor by flapping their shells, rather than the mechanical false teeth sold in novelty shops

Gastropoda examples

snails & slugs

Mussels secrete

strong threads that tether (attach) them rocks, docks, boats, and shells of other animals

Trochopore

the ciliated larval stage of many molluscs

what does make the water to be propulsed through the siphon?

the mantle

Suspension feeders

trap small food particles in mucus that coats the gills, and cilia then convey those particles to the mouth

Cephalopods are carnivorous, which_(describe way to hunt)

use their tentacles to grasp prey, which then they bite with beak-like jaws and immobilize with a poison present in their saliva

who is the only natural predator of the two large squids known?

whale