ArthropodsArthropods

Phylum ArthropodaPhylum Arthropoda Greek for jointed feetGreek for jointed feet Crabs, shrimp, barnacles, Crabs, shrimp, barnacles,

Insects, spiders etc.Insects, spiders etc. Largest phylum of animals Largest phylum of animals

with ~ 1 million known with ~ 1 million known speciesspecies Of all the animals on earth, Of all the animals on earth,

3 out of 4 are arthropods3 out of 4 are arthropods Have a tremendous ability Have a tremendous ability

to take advantage of just to take advantage of just about every habitat.about every habitat.

Phylum ArthropodaPhylum Arthropoda Evolution of exoskeletonEvolution of exoskeleton

Composed of chitinComposed of chitin• Tough, rigid material allows for Tough, rigid material allows for

great protection and supportgreat protection and support

Causes limitation in sizeCauses limitation in size• In order to grow the arthropod In order to grow the arthropod

must molt its exoskeletonmust molt its exoskeleton

• You wont see an arthropod as You wont see an arthropod as big as a squid or a whalebig as a squid or a whale

• Right after molting arthropods Right after molting arthropods are at their most vulnerable are at their most vulnerable statestate

Phylum ArthropodaPhylum Arthropoda Bilaterally symmetricalBilaterally symmetrical CoelomateCoelomate Segmented BodySegmented Body

Divided into 3 segments: Divided into 3 segments: head, thorax and abdomenhead, thorax and abdomen

Evolution of jointed Evolution of jointed appendagesappendages Increased mobility / flexibility Increased mobility / flexibility

(legs)(legs) Modified for feeding and Modified for feeding and

senses (mouthparts)senses (mouthparts) Used for protectionUsed for protection

Arthropod BiologyArthropod Biology DigestionDigestion

Filter feeding, scavengers, predatorsFilter feeding, scavengers, predators Appendages closest to the mouth, such as the Appendages closest to the mouth, such as the

maxillipeds, are specialized to sort out food and maxillipeds, are specialized to sort out food and push it toward the mouth.push it toward the mouth.

2 chambered stomach that has chitinous teeth or 2 chambered stomach that has chitinous teeth or ridges for grinding and bristles for sifting.ridges for grinding and bristles for sifting.

Open Circulatory SystemOpen Circulatory System Respiratory SystemRespiratory System

Arthropods have developed 3 types of respiratory Arthropods have developed 3 types of respiratory structures depending on their environment structures depending on their environment gillsgills, , tracheaetracheae, or , or book lungsbook lungs

Arthropod BiologyArthropod Biology Acute SensesAcute Senses

Many produce pheromones (a chemical odor) in Many produce pheromones (a chemical odor) in order to communicate and have highly developed order to communicate and have highly developed sensessenses

Most have one pair of large compound eyes and 3 Most have one pair of large compound eyes and 3 to 8 simple eyesto 8 simple eyes

• A simple eye – is a visual structure with only one lens A simple eye – is a visual structure with only one lens that is used for detecting lightthat is used for detecting light

• A compound eye – is a visual structure with many A compound eye – is a visual structure with many lenses. Each lens registers light from a tiny portion of lenses. Each lens registers light from a tiny portion of the field of viewthe field of view

ReproductionReproduction Separate sexes with internal fertilizationSeparate sexes with internal fertilization

Arthropod BiologyArthropod Biology Niche (What they do / their role):Niche (What they do / their role):

Arthropods are of great direct and indirect importance to Arthropods are of great direct and indirect importance to humans humans

The larger crustaceans--shrimps, lobsters, and crabs--are The larger crustaceans--shrimps, lobsters, and crabs--are used as food throughout the world used as food throughout the world

• Small planktonic crustaceans, such Small planktonic crustaceans, such as copepods, water fleas, and krill, as copepods, water fleas, and krill, are a major link in the food chain are a major link in the food chain • Approximately two-thirds of all Approximately two-thirds of all flowering plants (angiosperm) are flowering plants (angiosperm) are pollinated by insects pollinated by insects • They function as decomposersThey function as decomposers

Arthropods are major carriers of Arthropods are major carriers of diseasedisease

Phylum ArthropodaPhylum Arthropoda

3 Subphylums3 Subphylums

1.1. CheliceratesChelicerates

2.2. CrustaceansCrustaceans

3.3. UniramiaUniramia

Subphylum CheliceratesSubphylum Chelicerates

General Characteristics:General Characteristics: Chelicerates have six pairs of Chelicerates have six pairs of

appendages, which are uniramous appendages, which are uniramous (unbranched) (unbranched) include a pair of chelicerae, a pair of include a pair of chelicerae, a pair of

pedipalps, and four pairs of walking legs pedipalps, and four pairs of walking legs Lack mandibles and antennae Lack mandibles and antennae Respiration is by means of book gills, book Respiration is by means of book gills, book

lungs, or tracheae. lungs, or tracheae.

Subphylum CheliceratesSubphylum Chelicerates

3 classes:3 classes:

1.1. Merostomata - horseshoe crabsMerostomata - horseshoe crabs

2.2. Pycnogonida - sea spidersPycnogonida - sea spiders

3.3. Arachnida - spiders, ticks, mitesArachnida - spiders, ticks, mites

Class MerostomataClass MerostomataHorseshoe Crabs Horseshoe Crabs

• Carapace covering bodyCarapace covering body

• Cephalothorax, abdomen, telsonCephalothorax, abdomen, telson

• 6 pairs of appendages6 pairs of appendages

• Research using bloodResearch using blood

1. Class1. Class MerostomataMerostomata two different groups of marine organisms two different groups of marine organisms

the eurypterids and the horseshoe crabs the eurypterids and the horseshoe crabs Eurypterids are now extinct (they lived 200 to 500 million years ago)Eurypterids are now extinct (they lived 200 to 500 million years ago) Horseshoe crabs feed on small invertebratesHorseshoe crabs feed on small invertebrates

Members of this class have a large shield that covers the Members of this class have a large shield that covers the cephalothorax. cephalothorax.

The compound eyes are reduced The compound eyes are reduced The second pair of appendages, the pedipalps, resemble The second pair of appendages, the pedipalps, resemble

walking legs.walking legs. They have a long, spike-like appendage called a telson that They have a long, spike-like appendage called a telson that

projects from the rear of their bodies. projects from the rear of their bodies. The horseshoe crab uses its telson to flip itself over if it got flipped The horseshoe crab uses its telson to flip itself over if it got flipped

on its back. It is not used for defense as one might suspect.on its back. It is not used for defense as one might suspect.

Respiration is via book gills.Respiration is via book gills.

1. Class1. Class MerostomataMerostomata

2. Class2. Class PycnogonidaPycnogonida An example is a sea spiderAn example is a sea spider Sea spiders appear to be a sort of marine "spider," Sea spiders appear to be a sort of marine "spider," approximately 1000 described species – all are marineapproximately 1000 described species – all are marine They feed by sucking juices from soft-bodied They feed by sucking juices from soft-bodied

invertebrates through a long proboscis. invertebrates through a long proboscis. The body itself is not divisible into neatly- organized The body itself is not divisible into neatly- organized

tagmata or regions as it is in most other arthropods. tagmata or regions as it is in most other arthropods. An anterior region bears, besides the proboscis, three or An anterior region bears, besides the proboscis, three or

four pairs of appendages, including the first pair of four pairs of appendages, including the first pair of walking legs. walking legs.

2. Class2. Class PycnogonidaPycnogonida

3.3. Class Arachnida Class Arachnida

Spiders, ticks, mites, scorpionsSpiders, ticks, mites, scorpions over 60,000 described species – spiders make over 60,000 described species – spiders make

up the majority of those known speciesup the majority of those known species They have 8 legs instead of 6 like insects haveThey have 8 legs instead of 6 like insects have Nearly all species are terrestrial Nearly all species are terrestrial Respiration is via tracheae or book lungs Respiration is via tracheae or book lungs They have a two-segment body, made up They have a two-segment body, made up

merely of the merely of the thorax and and abdomen. . The The pedipalpi (leg-like mouthparts) of some (leg-like mouthparts) of some

species has instead been adapted for species has instead been adapted for sensory, , prey capture or reproductive functions. prey capture or reproductive functions.

3.3. Class ArachnidaClass Arachnida

Arachnids are mostly carnivorous, feeding Arachnids are mostly carnivorous, feeding on the pre-digested bodies of insects and on the pre-digested bodies of insects and other small animals. other small animals.

Many are venomous - they secrete poison Many are venomous - they secrete poison from specialized glands to kill prey or from specialized glands to kill prey or enemies. enemies.

Others are parasites, some of which are Others are parasites, some of which are carriers of disease. carriers of disease.

ArachnidsArachnids

Subphylum CrustaceaSubphylum Crustacea

Barnacles, crabs, Barnacles, crabs, shrimp, etc.shrimp, etc.

Head, thorax, abdomenHead, thorax, abdomenSpecialized Specialized

appendages--antennae, appendages--antennae, mandibles, maxillaemandibles, maxillae

Class MalacostracaClass MalacostracaOrder DecapodaOrder Decapoda

5 Pairs of walking legs5 Pairs of walking legs Crabs, shrimp, lobstersCrabs, shrimp, lobsters Krill—importance to Krill—importance to

food chainfood chain Unique pattern of Unique pattern of

segmentation among segmentation among crabscrabs

Class CirripediaClass Cirripedia

BarnaclesBarnacles Filter feedersFilter feeders Sessile (including on other living Sessile (including on other living

organisms)organisms) Feathery appendages (legs) to filter foodFeathery appendages (legs) to filter food Larvae swim then attach for Larvae swim then attach for

metamorphosismetamorphosis

Class CopepodaClass Copepoda

CopepodsCopepods Important planktonImportant plankton Filter feedersFilter feeders Stay afloat by enlarged appendagesStay afloat by enlarged appendages Many parasiticMany parasitic