PROTOSTOMES IIPROTOSTOMES II

MOLLUSKSMOLLUSKS

ARTHROPODSARTHROPODS

MOLLUSKSMOLLUSKS

Clams, snails, slugs, chitons, octopusesClams, snails, slugs, chitons, octopuses

Probably evolved early—after evolution Probably evolved early—after evolution of coelom but before segmented bodyof coelom but before segmented body

22ndnd only to arthropods in # of species only to arthropods in # of species

Main characteristics of Main characteristics of MollusksMollusks

Soft body usu. covered by calcium Soft body usu. covered by calcium carbonate shellcarbonate shell

Broad, flat, muscular footBroad, flat, muscular foot

Body organs concentrated in visceral Body organs concentrated in visceral mass above footmass above foot

Mantle Mantle

Radula (except in filter feeders)Radula (except in filter feeders)

Reduced coelomReduced coelom

Main body cavity is hemocoelMain body cavity is hemocoel

Most have open circulatory systemMost have open circulatory system

– Blood bathes tissues directlyBlood bathes tissues directly– HeartHeart aorta aorta smaller bld vessels smaller bld vessels

sinuses (hemocoel) sinuses (hemocoel) blood vessels blood vessels gills gills heart heart

Development of mollusksDevelopment of mollusks

Pass through one or more larval Pass through one or more larval stages:stages:

Trocophore larva Trocophore larva

In many molusks, trocopohore larva In many molusks, trocopohore larva develops into veliger larva (**unique develops into veliger larva (**unique to mollusks)to mollusks)

Gastropods: “Stomach-footed” Gastropods: “Stomach-footed” mollusksmollusks

Marine gastropods have gills; in land Marine gastropods have gills; in land gastropods, mantle functions as lunggastropods, mantle functions as lung

TorsionTorsion Head with tentaclesHead with tentacles 2 simple eyes2 simple eyes

SNAILS

WHELK

CONCH

Class BivalviaClass Bivalvia

Clams, oysters, scallops, musselsClams, oysters, scallops, mussels

Have 2-part shellHave 2-part shell

Suspension feedersSuspension feeders– Incurrent siphon brings in waterIncurrent siphon brings in water– Mucus of gills catches food particlesMucus of gills catches food particles– Excurrent siphon brings waste water outExcurrent siphon brings waste water out

Class Cephalopoda: “Head-Class Cephalopoda: “Head-footed” Mollusksfooted” Mollusks

Fast-swimming predatory animalsFast-swimming predatory animals

Mouth surrounded by tentacles or Mouth surrounded by tentacles or armsarms

Mantle is thick and muscularMantle is thick and muscular Well-developed eye sees imagesWell-developed eye sees images IntelligentIntelligent Ink sacInk sac ChromatophoresChromatophores

..\..\Marine Biology\Invertebrates\..\..\Marine Biology\Invertebrates\Octopus.asfOctopus.asf

..\..\Marine Biology\Invertebrates\..\..\Marine Biology\Invertebrates\Giant_Squid.asfGiant_Squid.asf

ARTHROPODSARTHROPODS

Segmented bodiesSegmented bodies Exoskeleton of chitin and proteinExoskeleton of chitin and protein Paired, jointed appendagesPaired, jointed appendages

– SwimmingSwimming– WalkingWalking– Sensory structuresSensory structures– Manipulation of foodManipulation of food

Nervous systemNervous system– Cerebral ganglia (brain)Cerebral ganglia (brain)– Ventral nerve cordVentral nerve cord– AntennaeAntennae– Many have compound eyesMany have compound eyes

Open circulatory SystemOpen circulatory System

Specialized respiratory structuresSpecialized respiratory structures– GillsGills– TracheaeTracheae– Book lungsBook lungs

A survey of A survey of ArthropodsArthropods

Subphylum MyriapodaSubphylum Myriapoda Centipedes Centipedes

(Chilopoda) (Chilopoda)

1 pair legs/segment1 pair legs/segment CarnivorousCarnivorous Long legs – run Long legs – run

rapidlyrapidly Poison claws on 1Poison claws on 1stst

segment behind segment behind headhead

Millipedes Millipedes (Diplopoda)(Diplopoda)

2 pairs 2 pairs legs/segmentlegs/segment

HerbivoresHerbivores Crawl slowlyCrawl slowly

ArachnidsArachnids

Cephalothorax and abdomenCephalothorax and abdomen 6 pairs of jointed appendages6 pairs of jointed appendages Gas exchange by tracheae, book Gas exchange by tracheae, book

lungs, or bothlungs, or both

CrustaceansCrustaceans

Primarily aquatic – gillsPrimarily aquatic – gills Hard mandibles for biting and grindingHard mandibles for biting and grinding Maxillae- manipulate and hold foodMaxillae- manipulate and hold food Decapods – 5 pairs of walking legsDecapods – 5 pairs of walking legs Chelipeds – large clawsChelipeds – large claws

InsectsInsects

Most numerous and diverse group on Most numerous and diverse group on the planetthe planet

6 legs6 legs 3 distinct body regions: head, 3 distinct body regions: head,

thorax, and abdomenthorax, and abdomen 1 pair of antennae, simple and 1 pair of antennae, simple and

comound eyescomound eyes http://entochem.tamu.edu/http://entochem.tamu.edu/

insect_structure-function/index.htmlinsect_structure-function/index.html

RespirationRespiration– Air enters tracheal tubes through Air enters tracheal tubes through

spiracles in body wallspiracles in body wall– Allows for high metabolic rateAllows for high metabolic rate

Excretion through Malpighian tubulesExcretion through Malpighian tubules– Discharged into intestineDischarged into intestine

Separate sexesSeparate sexes– Fertilization is internalFertilization is internal

Several molts occur during Several molts occur during developmentdevelopment

MetamorphosisMetamorphosis

Incomplete or completeIncomplete or complete

Incomplete :Incomplete :

egg egg larva (w/o functional wings) larva (w/o functional wings) adultadult

Complete:Complete:

Egg Egg larva larva pupa pupa adult adult

http://video.google.ca/videoplay?http://video.google.ca/videoplay?docid=5867193301785656504docid=5867193301785656504

Some insects are social: bees, antsSome insects are social: bees, ants

PheromonesPheromones

Success of InsectsSuccess of Insects

Exoskeleton – protects from Exoskeleton – protects from predators and dessicationpredators and dessication

Segmentation – mobility, flexibilitySegmentation – mobility, flexibility Jointed appendages – adaptable for Jointed appendages – adaptable for

many different things – movement, many different things – movement, feedingfeeding

Flying – distribution, ability to move Flying – distribution, ability to move to more suitable environmentto more suitable environment

Reproductive capability – many eggs, Reproductive capability – many eggs, protected by thick membraneprotected by thick membrane

Defensive and offensive capabilityDefensive and offensive capability