Invertebrates II:Invertebrates II:

Mollusca, Arthropoda, Mollusca, Arthropoda, Echinodermata, Chordata Echinodermata, Chordata (non-vertebrate chordates)(non-vertebrate chordates)

More species (200,000+) than any other More species (200,000+) than any other animal phylum except Arthropodaanimal phylum except Arthropoda

Soft body – often protected by CaCO3 shell Unsegmented, typically bilaterally

symmetrical

I. Phylum MolluscaI. Phylum Mollusca©2004 Amanda Demopoulos

Fig. 7.19

BODY PLAN:Head (eyes/sensory), visceral mass (organs), muscular footMantle – covers visceral mass, secretes shellRadula – Ribbon of small chitin teeth used in feedingGills (ctenidia-comb like) for gas exchange in mantle cavity

Radula – Ribbon of small chitin teeth used in feeding

I. Phylum MolluscaI. Phylum Mollusca• Exceptions to basic planExceptions to basic plan

• Bivalves Bivalves lacklack radulas radulas• Squids have internal shellsSquids have internal shells• Octopuses have no shellsOctopuses have no shells

• Reproduction (for some gastropods and bivalves)Reproduction (for some gastropods and bivalves)• 2 larval forms2 larval forms

• Trocophore – looks similar to annelid larvaTrocophore – looks similar to annelid larva• Veliger – ciliated, wing-like, with shellVeliger – ciliated, wing-like, with shell

Trocophore Veliger

A. A. Class GastropodaClass Gastropoda (=stomach foot) (=stomach foot) • Largest, most common, most diverse Largest, most common, most diverse

group (40K-75K sp)group (40K-75K sp)• Coiled mass of vital organs=visceral mass Coiled mass of vital organs=visceral mass

enclosed by a shellenclosed by a shell• SnailsSnails

• LimpetsLimpets

• AbalonesAbalones

• Nudibranchs – lose shell in larval stageNudibranchs – lose shell in larval stage

• Ventral creeping footVentral creeping foot• DietDiet

• Many vegetarian (scrape algae off rocks Many vegetarian (scrape algae off rocks with radula)with radula)

• Some predatorySome predatory• Prey on bivalves, worms, fishes, spongesPrey on bivalves, worms, fishes, sponges

I.I. Phylum MolluscaPhylum Mollusca

4 classes4 classes

©2004 Amanda Demopoulos

I. Phylum MolluscaI. Phylum Mollusca

A. A. Class GastropodaClass Gastropoda– TorsionTorsion : : during late veliger stage, twisting of visceral

mass 180º, counter-clockwise, resulting in coiled shell

– OperculumOperculum : leathery, trap door : leathery, trap door

– *Drawing: radula slide, live lettuce slugs-order *Drawing: radula slide, live lettuce slugs-order Sacoglossa, marine snails*Sacoglossa, marine snails*

AbalonesAbalones

SnailsSnails

SnailsSnails

SnailsSnails

NNudibranchsudibranchs

• Laterally compressedLaterally compressed• Hinged, 2-valved shell – (oysters, clams, mussels, Hinged, 2-valved shell – (oysters, clams, mussels,

scallops) muscles keep closedscallops) muscles keep closed• No head , No head , no radulano radula• Sedentary lifestyleSedentary lifestyle• Some have muscular foot for burrowing (e.g., Some have muscular foot for burrowing (e.g.,

clams)clams)• Gills Gills used for suspension feeding (active) & used for suspension feeding (active) &

respirationrespiration• Water enters and leaves through Water enters and leaves through siphons siphons (incurrent (incurrent

and excurrent)and excurrent)• Some anchor to substrate with Some anchor to substrate with byssal threads byssal threads (e.g., (e.g.,

mussels)mussels)• Scallops – Scallops – Swim! (repeated clapping of valves)! (repeated clapping of valves)

• *Drawing-Scallop shell, live flame scallop*Drawing-Scallop shell, live flame scallop

I. Phylum MolluscaI. Phylum Mollusca

Anterior adductor muscle

Posterior

adductor muscle

Valves

Foot

Mantle

Giant clam

B. B. Class BivalviaClass Bivalvia (=2 valved) (=2 valved)

1.1. OctopusesOctopuses (5 cm – 9 m)– no shell; Cryptic, bite prey with beak-like jaw (5 cm – 9 m)– no shell; Cryptic, bite prey with beak-like jaw2.2. Squid Squid (giant ~ 1000 kg, 18 m) – Shell reduced to (giant ~ 1000 kg, 18 m) – Shell reduced to penpen made of made of chitinchitin3.3. CuttlefishCuttlefish – Carbonate shell=cuttlebone, aid in buoyancy – Carbonate shell=cuttlebone, aid in buoyancy4.4. NautilusNautilus – Shell with chambers (septa) filled with gas, buoyancy organ – Shell with chambers (septa) filled with gas, buoyancy organ

• Exclusively marineExclusively marine• Fast moving, highly mobile predatorsFast moving, highly mobile predators

• Large eyesLarge eyes• Shell reduced or absent Shell reduced or absent • Foot modified as arms and tentacles bearing suckersFoot modified as arms and tentacles bearing suckers• SiphonSiphon – Directs water released from mantle cavity – Directs water released from mantle cavity• Move by Move by jet propulsionjet propulsion-move in any direction-move in any direction

• Ink sac for defense-distractionInk sac for defense-distraction• http://www.pbs.org/wnet/nature/octopus/

I. Phylum MolluscaI. Phylum Mollusca

C. C. Class Cephalopoda Class Cephalopoda (=head footed)(=head footed)

I.I.Phylum MolluscaPhylum MolluscaClass CephalopodaClass Cephalopoda- Octopus and squid have beak-like jaws- Octopus and squid have beak-like jaws- Mouth is central among tentacles- Mouth is central among tentacles

Octopus8 arms, non-retractable w/ 2 rows of suckers

Nautilus60-90 suckerless tentacles

Squid8 arms + 2 tentacles non-retractable

w/suckers and hooks

Cuttlefish8 arms + 2 tentacles, retractable w/

suckers, no hooks

**Drawing-squid and nautilus**

fin

mantle

funnel

eye 2 –extensible tentacle stalks

armtentacle clubs

C. C. Class PolyplacophoraClass Polyplacophora (Many-plate- (Many-plate-bearing=Chitons, 800 species)bearing=Chitons, 800 species)• Mostly graze algae on rocky shorelinesMostly graze algae on rocky shorelines• Exclusively marineExclusively marine• 8 overlapping plates8 overlapping plates• *drawing-chiton**drawing-chiton*

D. D. Class ScaphopodaClass Scaphopoda (=spade foot, Tusk shells) (=spade foot, Tusk shells)• Predators on foraminifera and juvenile bivalvesPredators on foraminifera and juvenile bivalves• Most common in deep water, buried in sedimentMost common in deep water, buried in sediment

I. Phylum MolluscaI. Phylum Mollusca

© Charlotte M. Lloyd

• Most species of any phylum (1 million+), Most species of any phylum (1 million+), 75% of all animals species described75% of all animals species described

• Insects, spiders, centipedes, crabs, Insects, spiders, centipedes, crabs, lobsters, shrimp, barnacles, etc.lobsters, shrimp, barnacles, etc.

• Segmented, bilaterally symmetrical bodySegmented, bilaterally symmetrical body• Jointed appendagesJointed appendages• ExoskeletonExoskeleton made of chitin made of chitin• Growth requires Growth requires moltingmolting - defenseless - defenseless

• Body segmentsBody segments• Head, thorax, abdomenHead, thorax, abdomen

• Some groups have head and thorax fused Some groups have head and thorax fused = cephalothorax= cephalothorax

• Discuss 3 subphyla and representative Discuss 3 subphyla and representative classesclasses

II. Phylum ArthropodaII. Phylum Arthropoda

Subphylum TrilobitomorphaSubphylum Trilobitomorpha

Class TrilobitaClass Trilobita• MarineMarine• Extinct since 250 myaExtinct since 250 mya• Rich fossil history because of Rich fossil history because of

exoskeletonexoskeleton• Dorso-ventrally flattenedDorso-ventrally flattened• *drawing-trilobite fossil**drawing-trilobite fossil*

A. A. Class MerostomataClass Merostomata (=legs attached to mouth, Horseshoe crabs) (=legs attached to mouth, Horseshoe crabs)• Not true crabsNot true crabs

• Named for feeding appendages – Named for feeding appendages – cheliceraechelicerae• Distinctive, horseshoe-shaped carapaceDistinctive, horseshoe-shaped carapace• No antennaeNo antennae• Benthic predators/scavengers on clams and small invertebratesBenthic predators/scavengers on clams and small invertebrates• No jaws - Grind food with bristles on walking legs (must be walking to No jaws - Grind food with bristles on walking legs (must be walking to

“chew”)“chew”)• Much of what we know understand about vision based on horseshoe crab Much of what we know understand about vision based on horseshoe crab

eyeseyes• Blood is used to test injectable pharmaceutical solutions for bacterial Blood is used to test injectable pharmaceutical solutions for bacterial

contamination contamination

Subphylum ChelicerataSubphylum Chelicerata

B. B. Class PycnogonidaClass Pycnogonida (= thick knees, (= thick knees, Sea spiders)Sea spiders)

• All marineAll marine• Superficially resemble spidersSuperficially resemble spiders• Mouth at end of large proboscisMouth at end of large proboscis• CarnivoresCarnivores

• Feed on sea anemones, hydrozoans, Feed on sea anemones, hydrozoans, • other soft invertsother soft inverts

• Legs much longer than body, more than 8Legs much longer than body, more than 8• *Drawing-sea spider**Drawing-sea spider*

Subphylum ChelicerataSubphylum Chelicerata

PHOTO: Bill Rudman

Subphylum CrustaceaSubphylum Crustacea (40K species) (40K species)• Contains majority of marine arthropod speciesContains majority of marine arthropod species• Gills + two pairs of antennae (sensory)Gills + two pairs of antennae (sensory)• Larval forms – nauplius and zoeaLarval forms – nauplius and zoea

A. Class CopepodaA. Class Copepoda (=oar foot, Copepods) (=oar foot, Copepods)• Extremely abundant holoplankton (always plankton)Extremely abundant holoplankton (always plankton)• Some live on/in substrates (benthos)Some live on/in substrates (benthos)• **Among most abundant animals on earth****Among most abundant animals on earth**• Important primary consumers of phytoplanktonImportant primary consumers of phytoplankton• Small << 1-2 mmSmall << 1-2 mm• Some parasitic formsSome parasitic forms

B. CirripediaB. Cirripedia(= hairy foot, Barnacles)(= hairy foot, Barnacles)• Active suspension feeders (filter feeders)Active suspension feeders (filter feeders)

• Use feathery Use feathery cirricirri (modified swimming (modified swimming appendages)appendages)

• Sessile (attached to surfaces-whales, piers)Sessile (attached to surfaces-whales, piers)

• Fouling organisms (boats, whales)Fouling organisms (boats, whales)

• Resemble mollusks superficially – Resemble mollusks superficially – calcareous platescalcareous plates

Subphylum CrustaceaSubphylum Crustacea

C. Class MalacostracaC. Class Malacostraca (=soft shell, 75% crustacean (=soft shell, 75% crustacean species)species)

1. 1. Order AmphipodaOrder Amphipoda (Amphipods) beach (Amphipods) beach hoppers, sand fleas, whale licehoppers, sand fleas, whale lice

• Laterally compressedLaterally compressed• Generally small (< 2 cm), but larger in deep oceanGenerally small (< 2 cm), but larger in deep ocean• Head and tail downwardHead and tail downward

• Widespread distributionWidespread distribution• Generally free livingGenerally free living• Important scavengersImportant scavengers

• *drawing-*drawing-GammarusGammarus slide, Daphnia slide* slide, Daphnia slide*

Subphylum CrustaceaSubphylum Crustacea

©2004 Amanda Demopoulos

C. C. Class MalacostracaClass Malacostraca2. 2. Order IsopodaOrder Isopoda (Isopods-rock lice, fish lice) (Isopods-rock lice, fish lice)

• Dorsoventrally compressedDorsoventrally compressed• Generally small (< 2 cm), but larger in deep oceanGenerally small (< 2 cm), but larger in deep ocean

• Related to terrestrial pill bugsRelated to terrestrial pill bugs

• Widespread distributionWidespread distribution• Generally free livingGenerally free living• Important scavengersImportant scavengers• Some parasitesSome parasites

Subphylum CrustaceaSubphylum Crustacea

C. C. Class MalacostracaClass Malacostraca3. 3. Order EuphausiaceaOrder Euphausiacea (Krill) - holoplankton (Krill) - holoplankton• Laterally compressedLaterally compressed

• Up to 10 cm long (usually smaller)Up to 10 cm long (usually smaller)

• Head and anterior segments fused to form Head and anterior segments fused to form distinct distinct carapacecarapace

• Widespread distributionWidespread distribution• Important primary consumers and predatorsImportant primary consumers and predators• Important prey for larger consumers (whales, Important prey for larger consumers (whales,

penguins, fish)penguins, fish)• Keystone speciesKeystone species in some ecosystems (Polar, in some ecosystems (Polar,

Southern Ocean)Southern Ocean)

• Aggregate in schools (billions of individuals)Aggregate in schools (billions of individuals)

Subphylum CrustaceaSubphylum Crustacea

C. Class Malacostraca4. Order Decapoda (=10 legs, Crabs, Lobsters,

Shrimps)• Most species in Crustacea (~10,000)

• Scavengers/Predators/Both

• Largest crustaceans• Five pairs of walking legs (deca=10)

• First pair usually modified as claws for feeding/defense

• Well-developed carapace = cephalothorax• Rest of body = abdomen, tail• Laterally compressed, except crabs –

abdomen under cephalothorax

• *drawing-crab zoea slide, lobster

Subphylum CrustaceaSubphylum Crustacea

Fig. 7.30

Phylum ArthropodaPhylum ArthropodaSubphylum-Subphylum-UniramiaUniramia

Class Insecta=Hexapoda (6 footed)Class Insecta=Hexapoda (6 footed)• 1 million species described to date1 million species described to date• Found in every known terrestrial + freshwater habitat, Found in every known terrestrial + freshwater habitat,

some marine except deep seasome marine except deep sea• Diversity attributable to Diversity attributable to

• Feeding specializationFeeding specialization• Dispersal capabilitiesDispersal capabilities• Predator-avoidance possibilities (flight)Predator-avoidance possibilities (flight)

• *Drawing-insect leg types*Drawing-insect leg typesa) walking legsa) walking legsb) swimming legsb) swimming legs

• 6000 species6000 species• Sea lilies, feather stars, brittle stars, sea stars, sand dollars, sea urchins, sea biscuits, sea cucumbersSea lilies, feather stars, brittle stars, sea stars, sand dollars, sea urchins, sea biscuits, sea cucumbers• Radial symmetryRadial symmetry

• Pentaradial symmetry in adultsPentaradial symmetry in adults• Oral/aboralOral/aboral

• Endoskeleton = hard plates, ~95% calcium carbonate, covered by skinEndoskeleton = hard plates, ~95% calcium carbonate, covered by skin• Complete digestive, nervous systems, and reproductive organsComplete digestive, nervous systems, and reproductive organs• RegenerationRegeneration• Water vascular system = internal hydraulic systemWater vascular system = internal hydraulic system

• Unique to echinodermsUnique to echinoderms• Tube feetTube feet (podia) extended by pressure from (podia) extended by pressure from ampullae ampullae (muscular sacs)(muscular sacs)• Tube feet used for locomotion, feeding, sensory functionsTube feet used for locomotion, feeding, sensory functions• Connected to exterior through Connected to exterior through madreporite (madreporite (porous plate)porous plate)

III.III. Phylum Echinodermata – Phylum Echinodermata – spiny skinspiny skin

A. A. Subclass AsteroideaSubclass Asteroidea (=star like, Sea stars) (=star like, Sea stars) • Most species have five arms (some more), Most species have five arms (some more), • Tube feet on oral surface in Tube feet on oral surface in ambulacral ambulacral

groovesgrooves• Endoskeleton composed of CaCOEndoskeleton composed of CaCO33 plates plates

• Flexible skeleton – permits movementFlexible skeleton – permits movement• Aboral surface often covered with Aboral surface often covered with

pedicellariaepedicellariae• Small claws used for grooming surfaceSmall claws used for grooming surface

• PredatorsPredators• Feed on bivalves, snails, barnaclesFeed on bivalves, snails, barnacles• Pry shells of bivalve apart and insert stomachPry shells of bivalve apart and insert stomach

III.III.Phylum EchinodermataPhylum EchinodermataClass Stelleroidea = a starClass Stelleroidea = a star

Crown of ThornsAcanthaster planci

B. B. Subclass OphiuroideaSubclass Ophiuroidea (Brittle stars, Serpent (Brittle stars, Serpent stars)stars)• Arms long and very flexibleArms long and very flexible

• May resemble writhing snakesMay resemble writhing snakes

• Tube feet lack suckers (used for feeding)Tube feet lack suckers (used for feeding)• Central disk distinct Central disk distinct • 1 Mouth, no anus1 Mouth, no anus• Cryptic – Usually not in open areasCryptic – Usually not in open areas• Scavengers/DetritivoresScavengers/Detritivores

• Particles collected by tube feet and passed to Particles collected by tube feet and passed to mouthmouth

III.III. Phylum EchinodermataPhylum EchinodermataClass StelleroideaClass Stelleroidea

C. C. Class EchinoideaClass Echinoidea (=spine like, Sea urchins, sea biscuits, sand (=spine like, Sea urchins, sea biscuits, sand dollars), (Echinus = Gr. Hedgehog)dollars), (Echinus = Gr. Hedgehog)

• Round, rigid test with movable spines and Round, rigid test with movable spines and pedicellariaepedicellariae• Spines and tube feet used for locomotionSpines and tube feet used for locomotion

• Tube feet in shallow Tube feet in shallow ambulacral groovesambulacral grooves (5 rows) along outside of (5 rows) along outside of testtest

• Complete digestive systemComplete digestive system• Mouth on bottom, anus on topMouth on bottom, anus on top

• HerbivoresHerbivores• Feed on seaweeds and seagrasses (especially drifting) plus attached Feed on seaweeds and seagrasses (especially drifting) plus attached

encrusting organismsencrusting organisms• Mouth includes Mouth includes Aristotle’s lantern Aristotle’s lantern (system of jaws and muscles used to bite (system of jaws and muscles used to bite

off algae, other food from bottom)off algae, other food from bottom)

III. Phylum EchinodermataIII. Phylum Echinodermata