Phylum Arthropoda

Phylum Arthropoda

Several million species.Hard exoskeleton.Coelomate protostomes.

Phylum ArthropodaSubphylum Trilobitomorpha

Phylum ArthropodaSubphylum TrilobitomorphaSubphylum Cheliceriformes Class Chelicerata Subclass Merostomata (horseshoe crabs)

Phylum ArthropodaSubphylum TrilobitomorphaSubphylum Cheliceriformes Class Chelicerata Subclass Merostomata (horseshoe crabs) Subclass Arachnida (spiders, scorpions, mites, ticks)

Phylum ArthropodaSubphylum TrilobitomorphaSubphylum Cheliceriformes Class Chelicerata Subclass Merostomata (horseshoe crabs) Subclass Arachnida (spiders, scorpions, mites, ticks) Class Pycnogonida (sea spiders)

Phylum ArthropodaSubphylum TrilobitomorphaSubphylum CheliceriformesSubphylum Myriapoda Class Chilapoda (centipedes)

Phylum ArthropodaSubphylum TrilobitomorphaSubphylum CheliceriformesSubphylum Myriapoda Class Chilapoda (centipedes) Class Diplopoda (millipedes)

Phylum ArthropodaSubphylum TrilobitomorphaSubphylum CheliceriformesSubphylum MyriapodaSubphylum Hexapoda Class Insecta

Phylum ArthropodaSubphylum TrilobitomorphaSubphylum CheliceriformesSubphylum MyriapodaSubphylum HexapodaSubphylum Crustacea Class Branchipoda (brine shrimp)

Phylum ArthropodaSubphylum TrilobitomorphaSubphylum CheliceriformesSubphylum MyriapodaSubphylum HexapodaSubphylum Crustacea Class Branchipoda Class Maxillopoda Subclass Copepoda (copepod)

Phylum ArthropodaSubphylum TrilobitomorphaSubphylum CheliceriformesSubphylum MyriapodaSubphylum HexapodaSubphylum Crustacea Class Branchipoda Class Maxillopoda Subclass Copepoda (copepod) Subclass Thecostraca (barnacles)

Phylum ArthropodaSubphylum TrilobitomorphaSubphylum CheliceriformesSubphylum MyriapodaSubphylum HexapodaSubphylum Crustacea Class Branchipoda Class Maxillopoda Class Malacostraca Order Decapoda (crabs, lobsters, shrimp)

Phylum ArthropodaSubphylum TrilobitomorphaSubphylum CheliceriformesSubphylum MyriapodaSubphylum HexapodaSubphylum Crustacea Class Branchipoda Class Maxillopoda Class Malacostraca Order Decapoda Order Isopoda (isopods)

What do Arthropods look like?Triploblastic, bilateral protostomesHard exoskeletonSpecialization of appendagesJointed appendagesCoelom that acts as an open

circulatory system (heomcoel)Excretory and gas exchange organsSense organs that extend out of

cuticleGrowth through molting (ecdysis)

Fig. 15.15

How do Arthropods support themselves and move?

Cuticle

Secreted by epidermisWaxes, lipoproteins, proteins.Sclerotized - tanning process that hardens

Fig. 15.16

How do Arthropods support themselves and move?

Each segment bound by four plates - dorsal tergite, ventral sternite, and two lateral pleurites.Muscle bands attach to apodemes.Appendages segmented with extrinsic or intrinsic muscles.

Fig. 15.15

How do Arthropods support themselves and move?

Appendages:Uniramous or

biramous.Parts are specialized

for different tasks.

Fig. 15.17

How do Arthropods support themselves and move?

Joints have thin flexible membrane.Antagonistic muscles: flexors and

extensors.Joints in one plane or ball-and-socket.Exoskeleton has condyles that act as

fulcrums.

Fig. 15.18

How do Arthropods support themselves and move?

Walking involves the coordinated movement of uniramous appendages in different planes.

Walking

Fig. 15.20

How do Arthropods support themselves and move?

Subphylum Myriapoda Millipedes (Class Diplopoda) have two legs per segment on each side. Slow but powerful.

Centipedes (Class Chilopoda) have one leg per segment on each side. Fast but not as powerful.

Walking

Fig. 18.3

How do Arthropods support themselves and move?Swimming

Flapping phyllopodia

Tail flexion

Fig. 15.19

How do Arthropods support themselves and move?Flying

Hemipterans (flies)

Fig. 17.16

Indirect flight muscles allow wings to beat faster than neural transmission. Dorsoventral and longitudinal muscles.Flexible thorax.

“Brain” is 2-3 ganglia with specific functions.Ganglionated ventral nerve cord.

How do Arthropods support themselves and move?

Fig. 15. 28

Sense organs (sensilla) protrude out of cuticle.

Can be slit in cuticle.Membranous drums.Chemoreceptors with thin cuticle.

How do Arthropods support themselves and move?

Simple ocelli.Complex lensed ocelli.Compound eyes made of ommatidia.

Fig. 15.29

Instars have tissue growth but no increase in external size.

Proecdysis - old endocuticle digested by enzymes from epidermis. Begin secreting new endocuticle.

Ecdysis - old cuticle splits and animal wiggles out. Body swells.

Postecdysis - cuticle hardens.

How do Arthropods grow?

How do Arthropods grow?Timing of molting.

Throughout life - crustaceans.Periodically until certain size - copepods.During metamorphosis - insects.

Hemimetabolous - insects hatch looking much like adults. Nymphs gradually attain adult form.

Fig. 17.35

Holometabolous - young very different from adults. Pupal stage metamorhosis into adult.

Fig. 17.36

How do Arthropods feed and digest?

Complete gut with regional specialization.Foregut - food intake, transport, storage, mechanical digestion (jaws, pharynx, gizzard).Midgut - extracellular digestion, nutrient uptake (cecae, digestive gland, hepatopancreas).Hindgut - excretion of undigested material, water reabsorption.

Fig. 15.24

How do Arthropods feed and digest?

Spider silk

Complex fibrous protein.Spinning apparatus in opithosome.

Fig. 19.5

Fig. 19.7

Liquid silk produced by glands, secreted into duct, pass to spinneret with tubes to outside.

How do Arthropods feed and digest?

Threads made of different thicknesses and combined in different ways for different functions.

How do Arthropods maintain homeostasis?

Circulation and respiration

Open hemocoel as a result of hard exoskeleton and lack of internal segmentation.

Muscular heart required since body movements can’t move blood.

Hemolymph has amebocytes, pigments, and some have clotting factors.

Fig. 15.25

How do Arthropods maintain homeostasis?

Circulation and respiration

Respiratory structures depend on habitat.

Gills in aquatic animals. Trachea in terrestrial insects.

Fig. 15.26

Arachnid book lung.

Fig. 19.18

How do Arthropods maintain homeostasis?

Osmoregulation and waste excretion

Closed structure required since open nephrostome wouldn’t with such a large hemocoel.

Material uptake depends on filtration pressure and active uptake.

Reuptake of salts and nutrients.

Malpighian tubules in arachnids and insects. Blind tubes extend into hemocoel and empty into gut. Produce uric acid.

Antennal and maxillary glands in crustaceans. Produce ammonia with some urea and uric acid.

Fig. 15.27

How do Arthropods reproduce and develop?

Most gonochoristic with formal mating and internal fertilization.

Fig. 16.32

How do Arthropods reproduce and develop?

Usually some brooding.Development often mixed with early brooding then larval stages.Eggs centrolecithal but amount of yolk varies (so does cleavage).

Nauplius larva

How do Arthropods reproduce and develop?Parasitic lifestyles

Rhizocephalan barnalces

Fig. 16.25

Fig. 16.16