Chapter33 Invertebrates

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint Lectures for Biology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero

Chapter 33Chapter 33

Invertebrates

MATERIALS FOR BIOLOGY OLYMPIAD PREPARATION

DWIWARNA HIGH BOARDING SCHOOL, BOGOR

INSTRUCTOR: WIDIATI and SUGANDA KUSMANA

CORRESPONDENCE: [email protected]


• Overview: Life Without a Backbone

• Invertebrates

– Are animals that lack a backbone

– Account for 95% of known animal species

Figure 33.1


• A review of animal phylogeny

Ancestral colonialchoanoflagellate

Eumetazoa

Bilateria

Deuterostomia

Po

rife

ra

Cn

ida

ria

Oth

er

bila

teria

ns

(incl

ud

ing

Ne

ma

tod

a, A

rth

rop

od

a,

Mo

llusc

a,

an

d A

nn

elid

a)

Ech

ino

de

rma

ta

Ch

ord

ata

Figure 33.2


• Exploring invertebrate diversity

PORIFERA (5,500 species)

A sponge

CNIDARIA (10,000 species)

A jelly

PLACOZOA (1 species) KINORHYNCHA (150 species)0.5 mm

A placozoan (LM) A kinorhynch (LM)250 µm

PLATYHELMINTHES (20,000 species) ROTIFERA (1,800 species)

A marine flatworm A rotifer (LM)

ECTOPROCTA (4,500 species) PHORONIDA (20 species)

Ectoprocts PhoronidsFigure 33.3


• Exploring invertebrate diversityBRACHIOPODA (335 species) NEMERTEA (900 species)

A brachiopod A ribbon wormACANTHOCEPHALA (1,100 species) CTENOPHORA (100 species)

An acanthocephalan A ctenophore, or comb jelly

MOLLUSCA (93,000 species) ANNELIDA (16,500 species)

An octopus A marine annelidLORICIFERA (10 species) PRIAPULA (16 species)

5 mm

50 µm

A loriciferan (LM) A priapulanFigure 33.3


• Exploring invertebrate diversityNEMATODA (25,000 species) ARTHROPODA (1,000,000 + species)

A roundworm A scorpion (an arachnid)

CYCLIOPHORA (1 species) TARDIGRADA (800 species)100 µm

100 µm

A cycliophoran (colorized SEM) Tardigrades (colorized SEM)

ONYCHOPHORA (110 species) HEMICHORDATA (85 species)

An onychophoran An acorn worm

ECHINODERMATA (7,000 species) CHORDATA (52,000 species)

A sea urchin A tunicateFigure 33.3


• Sponges are sessile and have a porous body and choanocytes

• Sponges, phylum Porifera

– Live in both fresh and marine waters

– Lack true tissues and organs


• Sponges are suspension feeders

– Capturing food particles suspended in the water that passes through their body

Azure vase sponge (Callyspongia plicifera)

Osculum

Spicules

Waterflow

Flagellum

CollarFood 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

Figure 33.4


• Choanocytes, flagellated collar cells

– Generate a water current through the sponge and ingest suspended food

• Most sponges are hermaphrodites

– Meaning that each individual functions as both male and female


• Concept 33.2: Cnidarians have radial symmetry, a gastrovascular cavity, and cnidocytes

• All animals except sponges

– Belong to the clade Eumetazoa, the animals with true tissues

• Phylum Cnidaria

– Is one of the oldest groups in this clade


• Cnidarians

– Have diversified into a wide range of both sessile and floating forms including jellies, corals, and hydras

– But still exhibit a relatively simple diploblastic, radial body plan


• The basic body plan of a cnidarian

– Is a sac with a central digestive compartment, the gastrovascular cavity

• A single opening

– Functions as both mouth and anus


• There are two variations on this body plan

– The sessile polyp and the floating medusa

Mouth/anus

TentacleGastrovascularcavity

Gastrodermis

Mesoglea

Epidermis

Tentacle

Bodystalk

Mouth/anus

MedusaPolyp

Figure 33.5


Tentacle

“Trigger”

Nematocyst

Coiled thread

DischargeOf thread

Cnidocyte

Prey

Figure 33.6

• Cnidarians are carnivores

– That use tentacles to capture prey

• The tentacles are armed with cnidocytes

– Unique cells that function in defense and the capture of prey


• The phylum Cnidaria is divided into four major classes

Table 33.1


– Hydrozoa, Scyphozoa, Cubozoa, and Anthozoa

(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.

Figure 33.7a–d


Hydrozoans

• Most hydrozoans

– Alternate between polyp and medusa forms

Feeding polyp

Reproductivepolyp

Medusabud

ASEXUALREPRODUCTION(BUDDING)

GonadMedusa

MEIOSIS

FERTILIZATION

SEXUALREPRODUCTION Egg Sperm

Developingpolyp

Portion ofa colonyof polyps

Maturepolyp

Planula(larva) Key

Haploid (n)Diploid (2n)1 mm

Zygote

Figure 33.8

A colony ofinterconnected

polyps (inset,LM) results

from asexualreproductionby budding.

1

Some of the colony’s polyps, equipped with tentacles, are specialized for feeding.

2 Other polyps, specialized for reproduction, lack tentacles and produce tiny medusae by asexual budding.

3

The medusae swim off, grow, and reproduce sexually.

4

The zygote develops into a solid ciliated larva called a planula.5 The planula eventually settles

and develops into a new polyp.6


Scyphozoans

• In the class Scyphozoa

– Jellies (medusae) are the prevalent form of the life cycle


Cubozoans

• In the class Cubozoa, which includes box jellies and sea wasps

– The medusa is box-shaped and has complex eyes


Anthozoans

• Class Anthozoa includes the corals and sea anemones

– Which occur only as polyps


• Concept 33.3: Most animals have bilateral symmetry

• The vast majority of animal species belong to the clade Bilateria

– Which consists of animals with bilateral symmetry and triploblastic development


Flatworms

• Members of phylum Platyhelminthes

– Live in marine, freshwater, and damp terrestrial habitats

– Are flattened dorsoventrally and have a gastrovascular cavity

• Although flatworms undergo triploblastic development

– They are acoelomates


• Flatworms are divided into four classes

Table 33.2


Turbellarian

• Turbellarians

– Are nearly all free-living and mostly marine

Figure 33.9


• The best-known turbellarians, commonly called planarians

– Have light-sensitive eyespots and centralized nerve nets

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

Figure 33.10


Monogeneans and Trematode

• Monogeneans and trematodes

– Live as parasites in or on other animals

– Parasitize a wide range of hosts


• Trematodes that parasitize humans

– Spend part of their lives in snail hosts

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

Figure 33.11

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


• Most monogeneans

– Are parasites of fish


Tapeworm

• Tapeworms

– Are also parasitic and lack a digestive system

Proglottids withreproductive structures

200 µm

HooksSucker

Scolex

Figure 33.12


Rotifers

• Rotifers, phylum Rotifera

– Are tiny animals that inhabit fresh water, the ocean, and damp soil


• Rotifers are smaller than many protists

– But are truly multicellular and have specialized organ systems

0.1 mmFigure 33.13


• Rotifers have an alimentary canal

– A digestive tube with a separate mouth and anus that lies within a fluid-filled pseudocoelom

• Rotifers reproduce by parthenogenesis

– In which females produce more females from unfertilized eggs


• Concept 33.4: Molluscs have a muscular foot, a visceral mass, and a mantle

• Phylum Mollusca

– Includes snails and slugs, oysters and clams, and octopuses and squids

• Most molluscs are marine

– Though some inhabit fresh water and some are terrestrial

• Molluscs are soft-bodied animals

– But most are protected by a hard shell


• All molluscs have a similar body plan with three main parts

– A muscular foot

– A visceral mass

– A mantle


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.

Figure 33.16


• Most molluscs have separate sexes

– With gonads located in the visceral mass

• The life cycle of many molluscs

– Includes a ciliated larval stage called a trochophore


• There are four major classes of molluscs

Table 33.3


Chitons

• Class Polyplacophora is composed of the chitons

– Oval-shaped marine animals encased in an armor of eight dorsal plates

Figure 33.17


Gastropods

• About three-quarters of all living species of molluscs

– Belong to class Gastropoda

A land snail (a)

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

(b)Figure 33.18a, b


• Most gastropods

– Are marine, but there are also many freshwater and terrestrial species

– Possess a single, spiraled shell

• Slugs lack a shell

– Or have a reduced shell


• The most distinctive characteristic of this class

– Is a developmental process known as torsion, which causes the animal’s anus and mantle to end up above its head

Anus

Mantlecavity

StomachIntestine

Mouth

Figure 33.19


Bivalves

• Molluscs of class Bivalvia

– Include many species of clams, oysters, mussels, and scallops

– Have a shell divided into two halves

Figure 33.20


• The mantle cavity of a bivalve

– Contains gills that are used for feeding as well as gas exchange

Hinge areaGut Coelom

Heart

Adductormuscle

AnusExcurrentsiphon

Waterflow

IncurrentsiphonGill

Mantlecavity

Foot

Palp

Mouth

Shell

Mantle

Figure 33.21


Cephalopods

• Class Cephalopoda includes squids and octopuses

– Carnivores with beak-like jaws surrounded by tentacles of their modified foot


• Most octopuses

– Creep along the sea floor in search of prey

Figure 33.22a(a) Octopuses are considered among the

most intelligent invertebrates.


• Squids use their siphon

– To fire a jet of water, which allows them to swim very quickly

Figure 33.22b(b) Squids are speedy carnivores with

beaklike jaws and well-developed eyes.


`

• One small group of shelled cephalopods

– The nautiluses, survives today

Figure 33.22c(c) Chambered nautiluses are the only living

cephalopods with an external shell.


• Concept 33.5: Annelids are segmented worms

• Annelids

– Have bodies composed of a series of fused rings


• The phylum Annelida is divided into three classes

Table 33.4


Oligochaetes

• Oligochaetes (class Oligochaeta)

– Are named for their relatively sparse chaetae, or bristles made of chitin

– Include the earthworms and a variety of aquatic species


• Earthworms eat their way through the soil, extracting nutrients as the soil moves through the alimentary canal

– Which helps till the earth, making earthworms valuable to farmers


• Anatomy of an earthworm

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-carryinghemoglobin.

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

Table 33.23


Polychaetes

• Members of class Polychaeta

– Possess paddlelike parapodia that function as gills and aid in locomotion

Parapodia

Figure 33.24


Leeches

• Members of class Hirudinea

– Are blood-sucking parasites, such as leeches

Figure 33.25


• Concept 33.6: Nematodes are nonsegmented pseudocoelomates covered by a tough cuticle

• Among the most widespread of all animals, nematodes, or roundworms

– Are found in most aquatic habitats, in the soil, in moist tissues of plants, and in the body fluids and tissues of animals


• The cylindrical bodies of nematodes (phylum Nematoda)

– Are covered by a tough coat called a cuticle

25 µmFigure 33.26


• Some species of nematodes

– Are important parasites of plants and animals

50 µmEncysted juveniles Muscle tissue

Figure 33.27


• Concept 33.7: Arthropods are segmented coelomates that have an exoskeleton and jointed appendages

• Two out of every three known species of animals are arthropods

• Members of the phylum Arthropoda

– Are found in nearly all habitats of the biosphere


General Characteristics of Arthropods

• The diversity and success of arthropods

– Are largely related to their segmentation, hard exoskeleton, and jointed appendages


• Early arthropods, such as trilobites

– Showed little variation from segment to segment

Figure 33.28


• As arthropods evolved

– The segments fused, and the appendages became more specialized

• The appendages of some living arthropods

– Are modified for many different functions

Antennae(sensoryreception)

Head Thorax

Swimmingappendages

Walking legs

Mouthparts (feeding)Pincer (defense)

AbdomenCephalothorax

Figure 33.29


• The body of an arthropod

– Is completely covered by the cuticle, an exoskeleton made of chitin

• When an arthropod grows

– It molts its exoskeleton in a process called ecdysis


• Arthropods have an open circulatory system

– In which fluid called hemolymph is circulated into the spaces surrounding the tissues and organs

• A variety of organs specialized for gas exchange

– Have evolved in arthropods


• Molecular evidence now suggests

– That living arthropods consist of four major lineages that diverged early in the evolution of the phylum

Table 33.5


Cheliceriforms

• Cheliceriforms, subphylum Cheliceriformes

– Are named for clawlike feeding appendages called chelicerae

– Include spiders, ticks, mites, scorpions, and horseshoe crabs


• Most of the marine cheliceriforms are extinct

– But some species survive today, including the horseshoe crabs

Figure 33.30


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

Figure 33.31a–c

• Most modern cheliceriforms are arachnids

– A group that includes spiders, scorpions, ticks, and mites


• Arachnids have an abdomen and a cephalothorax

– Which has six pairs of appendages, the most anterior of which are the chelicerae

Digestivegland

Intestine

HeartStomach

Brain

Eyes

Poisongland

PedipalpChelicera

Book lung

Spermreceptacle

Gonopore(exit for eggs)Silk gland

Spinnerets

Anus

Ovary

Figure 33.32


Myriapods

• Subphylum Myriapoda

– Includes millipedes and centipedes


• Millipedes, class Diplopoda

– Have a large number of legs

• Each trunk segment

– Has two pairs of legs

Figure 33.33


• Centipedes, class Chilopoda

– Are carnivores with jaw-like mandibles

– Have one pair of legs per trunk segment

Figure 33.34


Insects

• Subphylum Hexapoda, insects and their relatives

– Are more species-rich than all other forms of life combined

– Live in almost every terrestrial habitat and in fresh water


• The internal anatomy of an insect

– Includes several complex organ systems

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.

Figure 33.35


• Flight is obviously one key to the great success of insects

• An animal that can fly

– Can escape predators, find food, and disperse to new habitats much faster than organisms that can only crawl


• Many insects

– Undergo metamorphosis during their development

• In incomplete metamorphosis, the young, called nymphs

– Resemble adults but are smaller and go through a series of molts until they reach full size


• Insects with complete metamorphosis

– Have larval stages specialized for eating and growing that are known by such names as maggot, grub, or caterpillar

• The larval stage

– Looks entirely different from the adult stage


• Metamorphosis from the larval stage to the adult stage

– Occurs during a pupal stage

Larva (caterpillar)(a)(b) Pupa

(c) Pupa(d) Emerging adult

(e) AdultFigure 33.6a–e


• Insects are classified into about 26 ordersORDER

Blattodea 4,000 Cockroaches have a dorsoventrally flattened body, with legs modified for rapid running. Forewings, when present, areleathery, 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

APPROXIMATENUMBER OF

SPECIESMAIN CHARACTERISTICS EXAMPLES

Germancockroach

Japanesebeetle

Earwig

Horsefly

Leaf-Footedbug

Cicada-killer wasp

Termite

Figure 33.37


• Insects are classified into about 26 orders

Lepidoptera 120,000 Butterflies and moths are among the best-known insects. They have two pairs of wings covered with tiny scales. To feed, theyuncoil 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, twopairs 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 chewingor lapping mouthparts. They undergo complete metamorphosis.

Swallowtailbutterfly

Dragonfly

Katydid

Stick insect

HumanBodylouse

Flea

Silverfish

Caddisfly

ORDERAPPROXIMATE

NUMBER OFSPECIES

MAIN CHARACTERISTICS EXAMPLE

Figure 33.37


Crustaceans

• While arachnids and insects thrive on land

– Crustaceans, for the most part, have remained in marine and freshwater environments


• Crustaceans, subphylum Crustacea

– Typically have biramous, branched, appendages that are extensively specialized for feeding and locomotion


• Decapods are all relatively large crustaceans

– And include lobsters, crabs, crayfish, and shrimp

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

(a)

Figure 33.38a


• Planktonic crustaceans include many species of copepods

– Which are among the most numerous of all animals

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

(b)

Figure 33.38b


• Barnacles are a group of mostly sessile crustaceans

– Whose cuticle is hardened into a shell

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

(c)

Figure 33.38c


• Concept 33.8: Echinoderms and chordates are deuterostomes

• At first glance, sea stars and other echinoderms, phylum Echinodermata

– May seem to have little in common with phylum Chordata, which includes the vertebrates


• Chordates and echinoderms share characteristics of deuterostomes

– Radial cleavage

– Development of the coelom from the archenteron

– Formation of the mouth at the end of the embryo opposite the blastopore


Echinoderms

• Sea stars and most other echinoderms

– Are slow-moving or sessile marine animals

• A thin, bumpy or spiny skin

– Covers an endoskeleton of hard calcareous plates


• Unique to echinoderms is a water vascular system

– A network of hydraulic canals branching into tube feet that function in locomotion, feeding, and gas exchange

StomachAnus

Ringcanal

Gonads

AmpullaPodium

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.

Figure 33.39


• The radial anatomy of many echinoderms

– Evolved secondarily from the bilateral symmetry of ancestors


• Living echinoderms are divided into six classes

Table 33.6


Sea Stars

• Sea stars, class Asteroidea

– Have multiple arms radiating from a central disk

• The undersurfaces of the arms

– Bear tube feet, each of which can act like a suction disk

(a) A sea star (class Asteroidea)Figure 33.40a


Brittle Stars

• Brittle stars have a distinct central disk

– And long, flexible arms

(b) A brittle star (class Ophiuroidea)Figure 33.40b


Sea Urchins and Sand Dollars

• Sea urchins and sand dollars have no arms

– But they do have five rows of tube feet that function in movement

(c) A sea urchin (class Echinoidea)Figure 33.40c


Sea Lilies and Feather Stars

• Sea lilies

– Live attached to the substrate by a stalk


Sea Cucumbers

• Feather stars

– Crawl about using their long, flexible arms

(d) A feather star (class Crinoidea)Figure 33.40d


Sea Cucumbers

• Sea cucumbers

– Upon first inspection do not look much like other echinoderms

– Lack spines, and their endoskeleton is much reduced

(e) A sea cucumber (class Holothuroidea)Figure 33.40e


Sea Daisies

• Sea daisies were discovered in 1986

– And only two species are known

(f) A sea daisy (class Concentricycloidea)Figure 33.40f


Chordates

• Chordates

– Phylum Chordata

– Consists of two subphyla of invertebrates as well as the hagfishes and the vertebrates

– Shares many features of embryonic development with echinoderms


• A summary of animal phyla

Table 33.7

Chapter33 Invertebrates

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Transcript of Chapter33 Invertebrates