IB-202-5

3-17-06

Cephalopods• Class Cephalopoda includes squids and octopuses

– Carnivores with beak-like jaws surrounded by tentacles. Foot modified to form siphon, tentacles and head.

– Closed circulatory system– Well developed eye similar to vertebrate eye (lens,

retina etc)– Very active life style. Squid can feed on herring by

zipping through a school. Herring capable of rapid swimming.

– Elaborate sex where male inserts packets of sperm into mantle cavity of female.

– Ink gland for escape.– Can teach octopus simple tasks. Can crawl out of

their tanks into another eat the crabs and return to their own

• Most octopuses– Creep along the sea floor in search of prey. Some

have toxin associated with their bite. Very good at changing color so they are camouflaged in nature.

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.

Wednesday, 15 Jan., 2003, 16:50 GMT Giant squid Architeutis dux

'attacks French boat'

….De Kersauson says his squid was three times as big

…..two of the tentacles were blocking the rudder.

…. the squid must have been seven or eight metres (22 to 26 feet) long.

…. we weren't going to attack it with our penknives.

Live giant squid caught on camera Wednesday, 28 September 2005, 05:42 GMT     

Japan's Ogasawara Islands8m-long Architeuthis

`• One small group of shelled cephalopods– The chambered nautiluses, survives today– Huge nautilus fossils in northern Africa

Figure 33.22c

(c) Chambered nautiluses are the only living cephalopods with an external shell. Have rudimentary eye without lens like a pin hole camera. Shell is chambered and put less dense ammonium chloride in chamber for flotation. Less dense than seawater.

General Characteristics of Phylum Arthropoda

• The diversity and success of arthropods.• Find them in fresh water, the ocean and

the land and air.– Are largely related to their segmentation,

hard chitinous exoskeleton, and the specialization jointed appendages for specific functions.

Common fossil trilobite• Early arthropods, such as trilobites

– Showed little variation from segment to segment and no specialized appendages

Figure 33.28

Specialization of appendages in modern forms

• As arthropods evolved– The segments fused, and the appendages became more specialized

• The appendages of some living arthropods– Are modified for many different functions as seen in the lobster

below (describe specialization)

Antennae(sensoryreception)

Head Thorax

Swimmingappendages

Walking legs

Mouthparts (feeding)Pincer (defense)

AbdomenCephalothorax

Figure 33.29

Thick exoskeleton

• The body of an arthropod– is completely covered by the cuticle, an exoskeleton made of chitin

(polyglucoseamine). Hardened claws of skeletons composed of protein, chitin and calcium carbonate

• When an arthropod grows its soft body becomes too large for its exoskeleton– Thus it sheds or molts its exoskeleton in a process called ecdysis.

Then it grows a new one. Its exoskeleton is very soft until the chitinous polymers become cross linked which hardens the cuticle.

Physiological Systems

• Arthropods have an open circulatory system– in which fluid called hemolymph is circulated

into the spaces surrounding the tissues and organs. Tube like heart. Presence of oxygen binding pigments (hemocyanin-blue)

• 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 (divided into subphyla)

Table 33.5

Cheliceriforms

• Subphylum Cheliceriformes

– Are named for clawlike feeding appendages called chelicerae

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

Horseshoe Crab• Most of the marine cheliceriforms are extinct

– But some species survive today, including the horseshoe crabs (laboratory experimental animal for demonstrating osmotic conformity)

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

Scorpions, mites and spiders

• Most modern cheliceriforms are arachnids– A group that includes spiders, scorpions,

ticks, and mites

Anatomy of a spider• Arachnids have an abdomen and a cephalothorax

– Which has six pairs of appendages, the most anterior of which are the chelicerae (special structures)

Digestivegland

Intestine

HeartStomach

Brain

Eyes

Poisongland

PedipalpChelicera

Book lung

Spermreceptacle

Gonopore(exit for eggs)Silk gland

Spinnerets

Anus

Ovary

Figure 33.32

Spiders digest there food outside of their body

They stab prey with their fangs, inject toxins and enzymes that digest tissues. Then they suck up the partially digested material as a fluid. Some of the enzymes are phospholipases that destroy cell membranes.Thus spider bites can develop into lesions and tissue can become necrotic. Not sure why these enzymes can have such a long half life (in case of snakes give antivenom injections).

Subphylum MyriapodaIncludes millipedes and centipedes

• Millipedes, class Diplopoda– have a large number of legs

• Each trunk segment– has two pairs of legs-eats plant material and detritus

Figure 33.33

• Centipedes, class Chilopoda– Are carnivores with jaw-like mandibles– Have one pair of legs per trunk segment– Poison claws on foremost 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,in

fresh water and a few on the surface of the ocean.

– A few found in Antarctica where there are only mosses to feed on.

Insect Anatomy– 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

Insects very successful as a group• 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 (example hords of grasshoppers that strip vegetation in African lands from time to time. Also in US, but we stop them with insect sprays.

Insect Reproduction

• Insects have internal fertilization. Lay eggs. Development of many involve juvenile stages that are very different from the adult

• 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

Complete metamorphosis• 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

Class Crustacea

• 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 (10 walking legs) 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. Note stalked eyes.

(a)

Figure 33.38a

• Planktonic crustaceans include many species of copepods. Plankton found in surface waters of ocean either drifting or weakly swimming. Moved along by the oceanic currents. Euphausids (krill) fed on my baleen whales (filter out 5 cm long krill). Baleen is composed of horny strips in the mouth of whales with fibers projecting from it to act as a filter. No teeth in these whales although the fetus does have teeth but looses them during maturation.

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 composed

mostly of calcium carbonate.– (Ships and whales-rocky intertidal full of barnacles)

The jointed appendages (modified legs)projecting from the shells of these barnacles capture organisms and organic particles suspended inthe water. Stand on their heads and gluethemselves to rocks with their antennae. Some formStalks like in picture, others not (example).

(c)

Figure 33.38c

Phylum Echinodermata (star fish, sea urchins and sea

cucumbers)

• Echinoderms and chordates are deuterostomes

• At first glance, sea stars and other echinoderms 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 (enterocoelus)– 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– Most have a water vascular system used for

movement

Anatomy of a Starfish• 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

Why are echinoderms placed near the chordates in view of their

radial anatomy???

• The radial anatomy of many echinoderms (not symmetry) evolved secondarily from the bilateral symmetry of ancestors (madreporite off center).

• 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 (laboratory sea urchin reproduction)

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

Crinoides (Feather stars)

– Move about slowly using their roots on the disc. Use feathery arms to swim. Alternately pump them up and down. Fossil forms were stalked crinoides.

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

Sea Cucumbers• Sea cucumbers

– Upon first inspection do not look much like other echinoderms– Have tube feet, but lack spines, and their endoskeleton is

much reduced. – Served as an expensive dinner food at Chinese banquets-

gelatinous. Dried, rehydrated then braised in abolone sauce.

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

Sea Daisies• Sea daisies were discovered in 1986

– And only two species are known live on water soaked wood

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

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