Chapter 33: Invertebrates33 of the 34 phyla of animals are invertebrates

Figure 33.2 Review of animal phylogeny

Ancestral colonialchoanoflagellate

Eumetazoa

Bilateria

Deuterostomia

Por

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Invertebrate taxa to know for BIO 111 2007

Total # of phyla: 34# presented in textbook: 24# discussed here: 9(# classes you need to know: 24)

Invertebrate taxa to know for BIO 111 2007

Porifera – spongesCnidaria

Hydrozoa - HydraScyphozoa - jellyfishCubozoa – sea waspsAnthozoa – sea anemones & corals

Platyhelminthes – flatwormsTurbellariaTrematodaCestoda

NematodaRotiferaMollusca

Polyplacophora – chitonsGastropoda – snailsBivalvia – clams & musselsCephalopodia – squids & octopi

Annelida Polychaeta – more wormsOligochaeta – earthwormsHirudinea - leeches

ArthropodaHexapoda - insectsCrustacea – crabs. shrimp, barnaclesMyriapods – centipedes, millipedesCheliceriforms – spiders, mites, ticks

EchinodermataAsteroidea – sea starsOpiuroidea – brittle starsEchinoidea – sea urchins, sand $’sCrinoidea – sea liliesHolothuroidea – sea cucumbersConcentricycloidea – sea daisies

Phylum Porifera - sponges

Adam Laverty

Azure vase sponge (Callyspongia plicifera)

Osculum

Spicules

Waterflow

Flagellum

Collar

Food particlesin mucus

Choanocyte

Phagocytosis offood particles Amoebocyte

Choanocytes. The spongocoel is lined with feeding cells called choanocytes. By beating flagella, the choanocytes create a current that draws water in through the porocytes.

Spongocoel. Water passing through porocytes

enters a cavity called the spongocoel.

Porocytes. Water enters the epidermis through

channels formed by porocytes, doughnut-shaped cells that span the body wall.

Epidermis. The outer layer consists of tightly

packed epidermal cells.

Mesohyl. The wall of this simple sponge consists of

two layers of cells separatedby a gelatinous matrix, themesohyl (“middle matter”).

The movement of the choanocyte flagella also draws water through its collar of fingerlike projections. Food particles are trapped in the mucus coating the projections, engulfed by phagocytosis, and either digested or transferred to amoebocytes.

Amoebocyte. Amoebocytes transport nutrients to other cells ofthe sponge body and also produce materials for skeletal fibers (spicules).

5

6

7

4

3

2

1

Phylum Cnidaria

Phylum Cnidaria (basal metazoan)

Mouth/anus

TentacleGastrovascularcavity

Gastrodermis

Mesoglea

Epidermis

Tentacle

Bodystalk

Mouth/anus

MedusaPolyp

A cnidocyte with a nematocyst

Tentacle

“Trigger”

Nematocyst

Coiled thread

DischargeOf thread

Cnidocyte

Prey

Cnidarians

(a) These colonial polyps are members of class Hydrozoa.

(b) Many species of jellies (classScyphozoa), including thespecies pictured here, are bioluminescent. The largest scyphozoans have tentaclesmore than 100 m long dangling from a bell-shaped body up to 2 m in diameter.

(c) The sea wasp (Chironex fleckeri) is a member of class Cubozoa. Its poison,which can subdue fish andother large prey, is more potent than cobra venom.

(d) Sea anemones and othermembers of class Anthozoaexist only as polyps.

33.7 Jelly Swimming

corals of Class Anthozoa

Phylum Platyhelminthes

A Turbellarian

Pharynx. The mouth is at thetip of a muscular pharynx thatextends from the animal’sventral side. Digestive juicesare spilled onto prey, and thepharynx sucks small pieces offood into the gastrovascularcavity, where digestion continues.

Digestion is completed withinthe cells lining the gastro-vascular cavity, which hasthree branches, each withfine subbranches that pro-vide an extensive surface area.

Undigested wastesare egestedthrough the mouth.

Ganglia. Located at the anterior endof the worm, near the main sourcesof sensory input, is a pair of ganglia,dense clusters of nerve cells.

Ventral nerve cords. Fromthe ganglia, a pair ofventral nerve cords runsthe length of the body.

Gastrovascularcavity

Eyespots

These larvae penetratethe skin and blood vessels of humans working in irrigated fields contaminated with infected human feces.

Asexual reproduction within a snail results in another type of motilelarva, which escapes from the snail host.

Blood flukes reproduce sexually in the human host. The fertilized eggs exit the host in feces.

The eggs develop in water into ciliated larvae. These larvaeinfect snails, the intermediate hosts.

Snail host

1 mm

Female

Male

5

2

3

4

Schistosomiasis (bilharzia) is caused by a trematode

Mature flukes live in the blood vessels of the human intestine. A female fluke fits into a groove running the length of the larger male’s body, as shown in the light micrograph at right.

1

Class Cestoda: tapeworms

Proglottids withreproductive structures

200 µm

Hooks

SuckerScolex

red meatfish

Phylum Rotifera

0.1 mm

Lophophorates (several phyla)

Lophophore

Lophophore

Lophophore

Ectoprocts, such as this sea mat (Membraniporamembranacea), are colonial lophophorates.

In phoronids such as Phoronis hippocrepia, the lophophore and mouth are at one end of an elongated trunk.

Brachiopods have a hinged shell. The two parts of the shell are dorsal and ventral.

(a) (b) (c)

A ribbon worm, phylum Nemertea, is a lophophorate

Phylum Mollusca

Visceral mass

Mantle

Foot

Coelom Intestine

Gonads

Mantlecavity

Anus

Gill

Nervecords Esophagus

Stomach

ShellRadula

Mouth

Mouth

Nephridium. Excretory organs called nephridia remove metabolic wastes from the hemolymph.

Heart. 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 thus continually bathed in hemolymph.

The long digestive tract is coiled in the visceral mass.

Radula. The mouth region in many mollusc species contains a rasp-like feeding organ called a radula. This belt of backward-curved teeth slides back and forth, scraping and scooping like a backhoe.

The nervous system consists

of a nerve ring around the

esophagus, from which nerve

cords extend.

A chiton, class Polyplacophora

Class Gastropoda

A land snail (a)

A sea slug. Nudibranchs, or sea slugs, lost their shell during their evolution.

(b)

(limpets, too)

The results of torsion in a gastropod

Anus

Mantlecavity

Stomach

Intestine

Mouth

Class Bivalvia

Figure 33.21 Anatomy of a clamHinge area

Gut Coelom

Heart

Adductormuscle

AnusExcurrentsiphon

Waterflow

IncurrentsiphonGill

Mantlecavity

Foot

Palp

Mouth

Shell

Mantle pearls

glochidia of a bivalve

Class Cephalopoda

Octopuses are considered among the most intelligent invertebrates.

Squids are speedy carnivoreswith beaklike jaws and well-developed eyes.

Chambered nautiluses are the only living cephalopods with an external shell.

(a)

(b)(c)

“head-foot”shell is internal (beak)

reproductioncamouflage & ink

brains

show the movies

Phylum Annelida – the segmented worms

MouthSubpharyngealganglion

Pharynx EsophagusCrop

Gizzard

Intestine

Metanephridium

Ventralvessel

Nervecords

Nephrostome

Intestine

Dorsalvessel

Longitudinalmuscle

Circularmuscle

Epidermis Cuticle

Septum(partitionbetweensegments)

Anus

Each segment is surrounded by longitudinal muscle, which in turn is surrounded by circular muscle. Earthworms coordinate the contraction of these two sets of muscles to move (see Figure 49.25). These muscles work against the noncompressible coelomic fluid, which acts as a hydrostatic skeleton.

Coelom. The coelom of the earthworm is partitioned by septa.

Metanephridium. Each segment of the worm contains a pair of excretory tubes, called metanephridia, with ciliated funnels, called nephrostomes. The metanephridia remove wastes from the blood and coelomic fluid through exterior pores.

Tiny blood vessels are abundant in the earthworm’s skin, which functions as its respiratory organ. The blood contains oxygen-carrying hemoglobin.

Ventral nerve cords with segmental ganglia. The nerve cords penetrate the septa and run the length of the animal, as do the digestive tract and longitudinal blood vessels.

The circulatory system, a network of vessels, is closed. The dorsal and ventral vessels are linked by segmental pairs of vessels. The dorsal vessel and five pairs of vessels that circle the esophagus of an earthworm are muscular and pump blood through the circulatory system.

Cerebral ganglia. The earthworm nervous system features a brain-like pair of cerebral ganglia above and

in front of the pharynx. A ring of nerves around the pharynx connects to a subpharyngeal ganglion, from which a fused

pair of nerve cords runs posteriorly.

Chaetae. Each segment has four pairs of

chaetae, bristles that provide traction for

burrowing.

Many of the internal structures are repeated within each segment of

the earthworm.

Giant Australian earthworm

Clitellum

Darwin again: “1 acre of British farmland contained about 50,000 earthworms that produced 18 tons of castings per year” (Campbell & Reese)

Invasive species?

A polychaete Annelid

Parapodia

A leech, class Hirudinea

mostly freshwater, but watch out for those terrestrial forms.predators, parasites, scavengersreduced anatomySome parasites highly specialized

hirudinanaesthesiavasodilators

HOWARD LIPIN / Union-Tribune

Phylum Nematoda

25 µm

Trichinosis is caused by parasitic nematodes

50 µmEncysted juveniles Muscle tissue

Trilobites were early arthropods, >250 mya

Antennae(sensoryreception)

HeadThorax

Swimmingappendages

Walking legs

Mouthparts (feeding)Pincer (defense)

AbdomenCephalothorax

Horseshoe crabs are Cheliceriforms

Arachnids are cheliceriforms

Scorpions have pedipalps that are pincers specialized for defense and the capture of food. The tip of the tail bears a poisonous stinger.

(a) Dust mites are ubiquitous scavengers in human dwellings but are harmless except to those people who are allergic to them (colorized SEM).

(b) Web-building spiders are generally most active during the daytime.

(c)

50 µm

Digestivegland

Intestine

Heart

StomachBrain

Eyes

Poisongland

PedipalpChelicera

Book lung

Spermreceptacle

Gonopore(exit for eggs)

Silk gland

Spinnerets

Anus

Ovary

millipedes are myriapods

Centipedes are myriapods

Compound eye

Antennae

Anus

Vagina

OvaryDorsalartery Crop

Abdomen Thorax Head

The insect body has three regions: head, thorax, and abdomen. The segmentation of the thorax and abdomen are obvious, but the segments that form the head are fused.

Heart. The insect heart drives hemolymph through an open circulatory system.

Cerebral ganglion. The two nerve cords meet in the head, where the ganglia of several anterior segments are fused into a cerebral ganglion (brain). The antennae, eyes, and other sense organs are concentrated on the head.

Tracheal tubes. Gas exchange in insects is accomplished by a tracheal system of branched, chitin-lined tubes that infiltrate the body and carry oxygen directly to cells. The tracheal system opens to the outside of the body through spiracles, pores that can control air flow and water loss by opening or closing.

Nerve cords. The insect nervous system consists of a pair of ventral nerve cords with several segmental ganglia.

Insect mouthparts are formed from several pairs of modified appendages. The mouthparts include mandibles, which grasshoppers use for chewing. In other insects, mouthparts are specialized for lapping, piercing, or sucking.

Malpighian tubules. Metabolic wastes are

removed from the hemolymph by excretory organs called Malpighian

tubules, which are out-pocketings of the

digestive tract.

Metamorphosis (ecydsis)

Larva (caterpillar)(a)(b) Pupa

(c) Pupa(d) Emerging adult

(e) Adult

ORDER

Blattodea 4,000 Cockroaches have a dorsoventrally flattened body, with legs modified for rapid running. Forewings, when present, are leathery, whereas hind wings are fanlike. Fewer than 40 cock-roach species live in houses; the rest exploit habitats ranging from tropical forest floors to caves and deserts.

Beetles comprise the most species-rich order of insects. They have two pairs of wings, one of which is thick and leathery, theother membranous. They have an armored exoskeleton andmouthparts adapted for biting and chewing. Beetles undergocomplete metamorphosis.

Earwigs are generally nocturnal scavengers. While some species are wingless, others have two pairs of wings, one of which is thick and leathery, the other membranous. Earwigshave biting mouthparts and large posterior pincers. They un-dergo incomplete metamorphosis.

Dipterans have one pair of wings; the second pair has become modified into balancing organs called halteres. Their head islarge and mobile; their mouthparts are adapted for sucking,piercing, or lapping. Dipterans undergo complete metamorpho-sis. Flies and mosquitoes are among the best-known dipterans, which live as scavengers, predators, and parasites.

Hemipterans are so-called “true bugs,” including bed bugs, assassin bugs, and chinch bugs. (Insects in other orders aresometimes erroneously called bugs.) Hemipterans have two pairs of wings, one pair partly leathery, the other membranous.They have piercing or sucking mouthparts and undergoincomplete metamorphosis.

Ants, bees, and wasps are generally highly social insects. Theyhave two pairs of membranous wings, a mobile head, and chewing or sucking mouthparts. The females of many species have a posterior stinging organ. Hymenopterans undergo com-plete metamorphosis.

Termites are widespread social insects that produce enormous colonies. It has been estimated that there are 700 kg oftermites for every person on Earth! Some termites have twopairs of membranous wings, while others are wingless. They feed on wood with the aid of microbial symbionts carried in specialized chambers in their hindgut.

Coleoptera 350,000

Dermaptera 1,200

Diptera 151,000

Hemiptera 85,000

Hymenoptera 125,000

Isoptera 2,000

APROXIMATENUMBER OF

SPECIESMAIN CHARACTERISTICS EXAMPLES

Germancockroach

Japanesebeetle

Earwig

Horsefly

Leaf-Footedbug

Cicada-killer wasp

Termite

Lepidoptera 120,000 Butterflies and moths are among the best-known insects. They have two pairs of wings covered with tiny scales. To feed, they uncoil a long proboscis. Most feed on nectar, but some species feed on other substances, including animal blood or tears.

Odonata5,000 Dragonflies and damselflies have two pairs of large, membran-

ous wings. They have an elongated abdomen, large, compound eyes, and chewing mouthparts. They undergo incomplete meta-morphosis and are active predators.

Orthoptera 13,000 Grasshoppers, crickets, and their relatives are mostly herbi-vorous. They have large hind legs adapted for jumping, two pairs of wings (one leathery, one membranous), and biting or chewing mouthparts. Males commonly make courtship sounds by rubbing together body parts, such as a ridge on their hind leg. Orthopterans undergo incomplete metamorphosis.

Phasmida 2,600 Stick insects and leaf insects are exquisite mimics of plants. The eggs of some species even mimic seeds of the plants on which the Insects live. Their body is cylindrical or flattened dorsoventrally. They lack forewings but have fanlike hind wings. Their mouthparts are adapted for biting or chewing.

Phthiraptera 2,400 Commonly called sucking lice, these insects spend their entire life as an ectoparasite feeding on the hair or feathers of a singlehost. Their legs, equipped with clawlike tarsi, are adapted forclinging to their hosts. They lack wings and have reduced eyes.Sucking lice undergo incomplete metamorphosis.

Siphonaptera 2,400 Fleas are bloodsucking ectoparasites on birds and mammals. Their body is wingless and laterally compressed. Their legs are modified for clinging to their hosts and for long-distance jumping. They undergo complete metamorphosis.

Thysanura 450 Silverfish are small, wingless insects with a flattened body and reduced eyes. They live in leaf litter or under bark. They can also infest buildings, where they can become pests.

Trichoptera 7,100 The larvae of caddisflies live in streams, where they make houses from sand grains, wood fragments, or other material held to-gether by silk. Adults have two pairs of hairy wings and chewing or lapping mouthparts. They undergo complete metamorphosis.

Swallowtailbutterfly

Dragonfly

Katydid

Stick insect

HumanBodylouse

Flea

Silverfish

Caddisfly

ORDERAPROXIMATENUMBER OF

SPECIES

MAIN CHARACTERISTICS EXAMPLE

Class Crustacea

Ghost crabs (genus Ocypode) live on sandy ocean beaches worldwide. Primarily nocturnal, they take shelter in burrows during the day.

(a)

Planktonic crustaceans known as krill are consumed in vast quantities by whales.

(b) The jointed appendages projecting from the shellsof these barnacles capture organisms and organic particles suspended inthe water.

(c)

Phylum Echinodermata

Stomach

Anus

Ringcanal

Gonads

Ampulla

Podium

Radialnerve

Tubefeet

Spine

Gills

A short digestive tract runs from the mouth on the bottom of the central disk to the anus on top of the disk.

The surface of a sea star is covered by spines that help defend against predators, as well as by small gills that provide gas exchange.

Madreporite. Water can flow in or out of the water vascular system into the surrounding water through the madreporite.

Branching from each radial canal are hundreds of hollow, muscular tube feet filled with fluid. Each tube foot consists of a bulb-like ampulla and suckered podium (foot portion). When the ampulla squeezes, it forces water into the podium and makes it expand. The podium then contacts the substrate. When the muscles in the wall of the podiumcontract, they force water back into the ampulla, making the podium shorten and bend.

Radial canal. The water vascular system consists of a ring canal in the central disk and five radial canals, each running in a groove down the entire length of an arm.

Digestive glands secrete digestive juices and aid in

the absorption and storage of nutrients.

Central disk. The central disk has a nerve ring and

nerve cords radiating from the ring into the arms.

(a) A sea star (class Asteroidea) (b) A brittle star (class Ophiuroidea)

(c) A sea urchin (class Echinoidea) (d) A feather star (class Crinoidea)

(e) A sea cucumber (class Holothuroidea) (f) A sea daisy (class Concentricycloidea)