CHAPTER 7

CHAPTER 7MARINE INVERTEBRATES

Marine Invertebrates Vertebrates: animals with a backboneInvertebrates: animals without a backboneAt least 97% of all species of animals are invertebrates

Sponges

SpongesSponges belong to the phylum Porifera or pore bearersaggregations of specialized cellsdo not form true tissues or organsnearly all marine

Spongessessile: living permanently attached to the bottom or some other surface

Sponges ostia: numerous tiny pores on the surface of the spongeallows water to enter and circulate through a series of canals where plankton and other organic matter are filtered out and eatensponge cells are very plasticif separated, the cells can even regroup and form a new sponge

Spongeswater is pumped into a larger feeding chamber lined with collar cells or choanocytes

water leaves through osculum: large opening on the top of the sponge

each choanocyte has a flagellum that creates currents and a thin collar that traps food, and then ingested by the body of the cellmost have many oscula

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Sponges

Spongesmost have spicules: transparent siliceous or calcareous supporting structures of different shapes and sizesmany have a skeleton of spongin: tough elastic fibers made of protein

these two are found mainly between the outer and inner layers of cells9

Spongesamoebocytes: wandering cells, that secrete spicules and spongin

also serve other uses such as food transport, food storage, cell repair and reproduction

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Spongessuspension feeders: animals that eat food particles suspended in waterfilter feeders: actively filter the food particles in the suspensiondeposit feeders: eat detritus that settles on the bottom

Sponges

SpongesMost produce asexuallybudding of new spongeSome use gemmules: survivor pods

SpongesFound almost everywhere in the worldlargest number are found in tropical watersencrusting sponges: form thin sometimes brightly colored growths on rocks or dead coral

Sponges Economic Importancebath spongesstill harvested in a few locations of the Gulf of Mexico and the eastern Mediterraneansome produce potentially useful chemicals

Cnidarians

CnidariansPhylum CnidariaAlso called coenlenteratesover 9,000 species including sea anemones, jellyfish, corals

Cnidariansdisplay radial symmetry: similar parts of the body are arranged and repeated around a central axislook the same from all sidesno head, front, or back

Cnidarianscnidocytes: specialized cells used mainly for capturing prey

Cnidariansoral surface: where the mouth is locatedaboral surface: located in the opposite site of the mouth

Cnidarians

Cnidarianscentrally located mouth surrounded by tentacles: slender finger-like extensions used to capture and handle foodmouth opens into a gut where food is digested

Cnidarianscapture food (small prey) by discharging nematocysts (or cnidae): unique stinging structures found within cells in the tentacles

CnidariansOccur in two basic forms - polyp or medusa

CnidariansPolyp: a sac-like attached stage with the mouth and tentacles oriented upwardsessileEx. sea anemone

CnidariansMedusa: Bell-like structure that resembles an upside-down polyp and is adapted for swimmingmotile, swimmingEx. jellyfish

Types of CnidariansHydrozoansScyphozoansAnthozoans

Hydrozoans (polyps)Feathery bushy colonies of tiny polypsdrifting colonies of hydrozoans are called siphonophores example: portuguese man-of-war (blue bubble or blue bottle) (Physalia physalis)

Portuguese Man-of-War

ScyphozoansTrue jellies with medusa shapes that can reach up to 6 feet in diameterTrue Nematocysts are only found in Hydrozoans and Scyphozoans

Anthozoanslack medusa stageconsists of solitary colonial polypsanemonescoralsseapenssea pansies

Bilaterally Symmetric Worms

Wormsbilateral symmetry: the arrangement of the body parts in such a way that there is only one way to cut the body and create two identical halvesex. humans

FlatwormsPhylum: Platyhelminthesdorsoventrally flattened (flat bellies and backs)20,000 species of flatworms

FlatwormsTurbellariansmost common marine flatwormsmainly live in or around the surface of other invertebrates (mollusks, crabs, etc)

FlatwormsFlukes (trematodes)largest group of flatworms6,000+ speciesall are parasites adults always live in a vertebratelarvae may inhabit invertebrates or smaller vertebrates such as fish

FlatwormsTapeworms (cestodes)parasiticlong body made of repeating unitslive in the intestines of vertebrates

Ribbon Worms (Nemertean Worms)Phylum: Nemerteaoutwardly resemble flatworms, slightly more complexmore advanced intestinal systemcirculatory systemproboscis: long fleshy tube used to entangle prey

can extend proboscis up to 1m beyond their bodyone species reaches 30m (100ft) making it the longest invertebrate on earth

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Nematodes (roundworms)Phylum: Nematodamost are parastic a layer of muscles in the body wall pushes and squeezes against the fluid creating a hydrostatic skeletonHydrostatic Skeleton: A system that uses water pressure against the body wall to maintain body shape and aid in locomotionprovide support and aids in locomotion

Nematodes (roundworms)live in the flesh or muscle tissue which used to make sashimi, sushi, and cervicheif the fish is served raw or undercooked, human infection is possible

most people immediately vomit the infected matter back up there are exceptions in which the larvae make it to the stomach or intestinecause symptoms similar to ulcerssevere pain, nausea, muscle tearing and sometimes bleeding

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Segmented Worms (annelids)Phylum: Annelidaearthworms and many marine wormsDisplay segmentationsegments act as a hydrostatic skeletonefficient crawlers and burrowers

can be contracted in sequence by body wall musclesthis and flexibility also given by segmentation makes annelids 41

Polychaetes (Bristle worms)Phylum: Annelida Class: Polychaetaeach body segment has a pair of flattened extensions called parapodia beyond/beside feetwhich have stiff, often sharp bristles called setaeUsed for movement and breathing through gills on parapodia

true circulatory systemmainly carnivorousseveral pairs of eyesa proboscis, often jawedmany polychaetes live in temporary or permanent tubes made of mucus, protein, seaweed, mud, sand or shell fragments

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Polychaetes (Bristle worms)

OligochaetesOligochaetessmall worms found in mud and sandfeed on detrituslack parapodia

OligochaetesLeechesClass: Hirudinealive mainly in fresh watermarine species can be found attached to marine fishes and invertebrateshighly specialized annelida with a sucker at each end and no parapodiaEchiuransall marinesimilar to peanut worms in size and shapehave a non-retractable, spoon-like (forked) proboscisdeposit feeders

Peanut Wormssipunculans1 to 35 cm long (.4 to 14 inches)soft unsegmented bodiesburrow in the bottom or move into empty shellswhen it becomes compact it resembles a large peanut

MolluscsClams, Octopuses, and Snails

MolluscsPhylum: Molluscamore species of mollusca than any other animal grouparound 200,000 living species

Molluscsmost have soft bodies encased in a calcium carbonate shelllive in marine, freshwater and terrestrial environments

Molluscscephalopods (squid, cuttlefish, octopus) most neurologically-advanced of all invertebratesgastropods (snails and slugs) are the most numerous divisiongiant or colossal squid are the largest known invertebrate species

MolluscsThe body is covered by a mantle: a thin layer of tissue that secretes the shellusually bilaterally symmetricventral, muscular foot usually used for locomotion

Molluscsmost have a head with eyes and additional sensory organsRadula: a ribbon of small teeth (unique to molluscs) or rasping tonguemade mainly of chitin

Molluscsgas exchange occurs through paired gillsshell is modified (internal for squid, octopod; external for gastropods)

Gastropods

Gastropodsclass - Gastropodalargest, most common, and most varied groupincludes snails, periwinkles, limpets, abalones

previously called univalvesgastropod literally means stomach footed

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Gastropodsa coiled collection of organs enclosed by a dorsal shellshell rests on a ventral footvaried shell structure and size

Gastropodscarnivorous gastropods prey on clams, oysters worms and even small fishesother gastropods are detritivores

GastropodsNudibranchs or sea slugs - gastropods that have lost their shell entirely

nudibranchs

Bivalves

Bivalvesclass - Bivalviaincludes clams, mussels, oysters, scallops

Bivalveshave two-part shells each part is called a valvesymmetric along the hinge lineno head no radulainner surface of the shell is lined by the mantle

Bivalvesgills are used for gas exchange and filter feedingstrong muscles in the mantle cavity are used to open and close the valves

OystersMost commercially valuable for pearlsForm when the oysters secrete layers of calcium carbonate coat an irritant or parasite lodges between the mantle and the inner surface of the shell

ClamsUse foot to bury in sand or mudDraw water in and out of mantle through siphonsFeed and maintain oxygen while still buried

MusselsLive mainly in the intertidal zoneAttach to surface using strong, byssal threads (beard)

ScallopsHighly prized food source100 simple blue eyes around the valves

Cephalopods

Cephalopodsclass-cephalopodaspecialized for locomotionadapted mollusc body plan for an active way of life (nearly all agile swimmers)include octopuses, squids, cuttlefish, nautilus

Cephalopodscomplex nervous systemreduced inner shell or no shell at allall are marine or brackishno radula, but do have a two part beak

Cephalopodsfoot is modified into arms and tentacleslarge eyes usually set on sides of the headthick, muscular mantle

Cephalopods2 to 4 gillswater enters through the free edge of the mantle and leaves through the siphon or funnel a muscular tube formed by what remains of the foot

Nautilus

Nautilus the chambered nautilus is considered the most primitive living cephalopod, because of its shelldates back 450 million years

Nautilus shell is thin, double layered and pearly white inside with a dull white with reddish zebra stripe outsidethe shell is separated into chambers by the septa, made of shell materialas it grows it creates new larger chambers1 chamber every few weeks until it reaches 38 chambers

Nautilusoccupies one body chamberstrong, beak-shaped crushing jawseat algae , fish, crabs, shrimp and other invertebrates

Nautiluslarge collection of tentacles arranged into two circles, an inner and an outer.the female has twice as many tentacles in its inner circle than the male

Squid

Squidhas only a thin shell remnant (pen) within its mantlestrengthened outer collagen sheath to maintain the mantles shape and size

Squidto swim, the squid fills the mantle cavity with water and then forces it outward through the funnel in a jet-propulsion like manner normally swims backwards, can swim forward by bringing all 8 arms together

Humboldt Squid

Squidfins along the body help with stabilizationlarge squids can reach speeds of 15-20 mphmany species swim in schools

Squid8 arms, 2 long tentacles covered in suckers: adhesive discs used for suction between the squid an another objecttentacles only have suckers on the flattened end

Octopus

Octopushas lost shell entirelybag-like mantle located above the headalso has a strengthened collagen sheath surrounding the mantle

Octopusdoes not normally swimprefers to remain in contact with a solid surfaceuses suckers on its 8 legs to push and pull itself along the surfacemost have 240 suckers on each armCrawling

Octopususually a solitary animal that lives in a permanent den or cave under rocksinkchromatophores: specialized cells used to help an organism change colorChromatophores in action

Cephalopod Feeding and Digestion

Feeding and Digestion separate mouth and anusall cephalopods are carnivoresinvolves salivary and digestive glands to help break down foodvaried diets and complexity of digestive systems based on diet

Hungry octopus

Feeding and Digestioncrystalline style: an enzyme secreting rod found in the stomach of bivalves continually rotates food and helps in digestion

Feeding and Digestion most molluscs have an open circulatory systemcephalopods have a closed circulatory system

Nervous System and Behaviors

Nervous Systemgastropods and bivalves do not have a single brain but several sets of gangliacephalopods most complexallows for learning to occurand for rapid movement and color changing to avoid predation

clusters of local brainslarger brainlarge never fibers that extend the length of the body

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Reproduction

Reproductionmost reproduce sexually, some hermaphroditiccephalopods use a spermatophorecephalopods lack larva and have large yolk-filled eggsoctopus protect eggs and female usually dies protecting young because she does not leave to eat herself

Reproduction

Octopus mating

Arthropods

ArthropodsPhylum: Arthropodalargest phylum of animalsinsects are dominant terrestrial groupcrustaceans are more common in marine environments

Arthropodssegmented, bilaterally symmetricpossess an exoskeleton: large, non-living external skeletoncomposed of chitin and secreted by the underlying layer of tissue

Arthropodsprovides protection, support and increased surface area for muscle attachmentto grow, arthropods must molt

Crustaceans

Crustaceanschitinous skeleton hardened by calcium carbonateappendages specialized for swimmingpossess 2 pairs of antennae

Small Crustaceans - Copepodssmall, important to planktonuse enlarged pair of antennae for swimmingmany are parasitic

Small Crustaceans - Barnaclesfilter feederslive attached to surfaces, including other living organismscovered in calcareous plateshave feather-like filtering appendages called cirriactually legs used to sweep water

Small Crustaceans Amphipods small curved body and flattened sidewaysless than 2 cm in lengthsome live under larger organisms skin like lice, parasites

Small Crustaceans - Isopodsabout the same size amphipodsdorsoventrally flattenedex. terrestrial pill bugsmany are parasitic

Small Crustaceans - KrillAlso called euphausidsplanktonic, shrimp-likeup to 6 cm long (2.5 in)most are filter feedersswim in groups of billions of individuals

Decapodsfive pairs of legs or pereiopodsthe first is heavier - usually claws for feeding and defense

Decapodsthree pairs of maxillipeds near the mouthturned forward, and specialized to sort food and push it towards the mouth

Decapodswell developed carapaceencloses the part of the body called the cephalothoraxthe rest of the body is known as the body

Decapodsshrimp and lobsters have laterally compressed bodies with distinct and elongated abdomens (the tail)

DecapodsDecapods use their chelipeds for feeding and fightingTherefore they often lose a clawThey are able to regenerate lost chelipeds

DecapodsAlso most arthropods have two distinct clawsThe larger is called the crusher clawAnd the thinner, more serrated one, is called the pincer or tearing claw

DecapodsIn many arthropods, such as lobsters, there are major structural difference between males and females1. Claw size (larger in males)2. Tail width (wider in females)3. Texture of swimmerets (harder in males)

DecapodsReproduce sexually, using internal fertilization

DecapodsAlso in crabs, a male has a v shaped abdomen and a female has a u shaped abdomen

ShrimpTypically scavengersVaried life environmentsMutualistic relationships with other organisms

Shrimp 1Shrimp 2

American Lobster (Homarus americanus)also known as the northern lobster, Atlantic lobster or Maine lobsterfamily Nephropidae, commercial lobstersbottom dwellerfound in colder waters off the Atlantic coast of North AmericaNew England and Canada

Lobstersscavenger and predatorsolitary in rocks or caves, also nocturnalexoskeleton, which molts 2-3 times a year as a juvenile and once a year as an adult

Blue Lobster Molt

LobstersHeavy bodied with a large abdomen and huge chelipedsone is lost in an accident or a fight it will regeneratesold with one claw -cull Sold with no claws bullet

Lobsters4 pairs of walking legs (pereiopods)4 sets of swimmerets (pleopods), extend across the bodyharder in malessofter in females used to protect eggs

Lobstersfeathery gills located on either side of the cephalothorax

Hermit Crabs

hermit crabs are not true crabs scavengershide in empty gastropod shells

Crabsabdomen is small and tucked under a compact and broad cephalothoraxlargest and most diverse group of decapods

Crabshighly mobile - much faster than lobstersmove sideways when theyre in a hurrysideways movement can also be used to indicate matingex. fiddler crab

Horseshoe Crabsnot true crabsliving fossilseyes being researched to improve vision errors in humans

Sea spiders

Lophophorates

LophophoratesHave a lophophore - feeding structure made of a set of ciliated tentacles arranged in a horseshoe-like shape

LophophoratesThree main types:Bryozoans - lace-likePhoronids - worm-likeLamp Shells - clam-like

Echinoderms

EchinodermsPhylum: EchinodermataPentamerous Radial symmetry: Five-way symmetry

EchinodermsWater-vascular system: A network of water-filled canalssea stars sea urchins connect to a madreporite: a porous plate on the aboral surface

EchinodermsTube feet: muscular extensions of the water-vascular system that often end in a suckerampullae: muscular sacs that sometimes aid in the extension of tube feet

Echinodermssmall nerve net similar to cnidariansability to regenerateComet: a sea star with one large regenerated arm

Echinodermsmany spines and bumps - part of the endoskeletongive the nickname spiny-skinned

EchinodermsFour main types:Sea starsBrittle StarsSea CucumbersSea Urchins

Sea StarsClass: Asteroideafive arms that radiate around a central disk

Sea Starshundreds of tube feet extend from the oral surface along radiating channels on each arm call ambulacral grooves

Sea Starsthe aboral surface of most sea stars is covered with spines modified into pincer like organs called pedicellariaemost are predators of bivalves

Brittle StarsClass: Ophiuroideastar shaped bodyvery long flexible armslack an anusare detritivores

Sea CucumbersClass: Holothuroideasuperficially wormlikelack spinesno radial symmetry

Sea Cucumbersoral and aboral surfaces are located on the endsdeposit feedersmove using five rows of tube feetuse branched tentacles to gather food

Sea Cucumbersdefensesome secrete toxic substancessome discharge, sometimes toxic, filaments from the anus to discourage predatorssome eviscerate: discharge the gut and other organs through the anus

Sea Urchinsendoskeleton is round and rigid with movable spines and pedicellariaemovement is based on tube feet and the movable spines joined to sockets of the exoskeleton

Sea Urchinsgrazers - sea weeds and grassesmouth has an intricate system of jaws and muscles called aristotles lanternused to bite off pieces

Sea Urchinslive in rocky shoresalso includes sand dollars

Chordates Without a Backbone

Chordates without a backbonePhylum Chordatadivided into three major groups (subphyla)two lack a backbone, one does notProtochordates: the invertebrate chordates, chordates without a backbone

Chordates without a backbone4 characteristics needed to be a chordate:1. single, hollow nerve chord that runs along the dorsal side of the body

Chordates with a backbone2. pharyngeal gill slits - small openings along the anterior end of the gutpharynx in humans

Chordates without a backbone3. notochord - flexible rod for support that lies between the nerve chord and the gut

Chordates Without a Backbone4. post-anal tail - a tail that extends beyond the anus (coccyx in humans)

Chordates without a backbone

Chordates without a backbone

Chordates without a backbonealso have a ventral heartin vertebrates the notochord is replaced by the backbone (vertebral column)

Tunicates

TunicatesSubphylum: Unichordatabest known are sea squirtsthe notochord and tail are absorbed during metamorphosis

Tunicatesdifference between sponge is the protective tunictunic: leathery or gelatinous outer covering not found on spongesfilter feeders

Lancelets

LanceletsSubphylum Cephalochordataalmost 3 in longlaterally compressed and elongated body like a fishbottom dwellersfilter feeders