![Page 1: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/1.jpg)
- Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head)
- Each body segment has a pair of jointed appendages
- Cuticle forms well-developed exoskeleton, made up of plates called sclerites
- Growth by ecdysis (hormone-induced molting)- no cilia on larvae or adults
- Main body cavity = hemocoel, with open circulatory system; coelom reduced to region around gonads
- exoskeleton used as attachment point for muscles
Phylum Arthropoda >1,000,000 species!
![Page 2: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/2.jpg)
Arthropod Phylogeny
5 Sub-phyla:
(1) Trilobites (extinct since Paleozoic)
(2) Chelicerates (spiders, horseshoe crabs, pycnogonids)
(3) Hexapoda (Insects)
(4) Crustacea (crabs, lobsters, shrimp)
(5) Myriapoda (centipedes, millipedes)
![Page 3: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/3.jpg)
Arthropod Success 1: Exoskeleton
Modification of segmented body plan, by growth of a hard external covering = cuticle, or exoskeleton
protection, osmoregulation - a major pre-adaptation for the transition to life on land
Loss of circular muscles, rigid body coelom not needed for hydrostatic skeleton replaced w/ open circulatory system + hemocoel (like in molluscs, but independently evolved)
Growth must proceed through a series of molts, controlled by the hormone ecdysone (where clade Ecdysozoa gets name)
![Page 4: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/4.jpg)
Arthropod Cuticle
hemocoel
Sensorychetae
cuticle
cuticle divided into outer layers for water retention, inner for rigidity
![Page 5: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/5.jpg)
Arthropod Cuticle
Chitin: high mol. weight nitrogenous polysaccharide
hemocoel
Sensorycheta
gland cell pore
procuticle
epicuticle
epicuticle has water-retaining layers of oily lipoproteins, wax
procuticle of chitin, cross-linked proteins and CaCO3
![Page 6: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/6.jpg)
Body WallEpidermis is a single layer of epithelial cells that secrete the cuticle in layers
Outer layer is epicuticle, with water-repellant hydrophobic layers - outermost layer: lipoproteins (fat + protein) - middle layer: waxy layer of fats, wax esters - inner layer: protein
Inner layer is the procuticle, of protein + chitin; hardened by:
(1) sclerotization = cross-linking of proteins into a 3D matrix (2) mineralization = depositing calcium carbonate in procuticle of crustaceans (i.e., crab shell)
![Page 7: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/7.jpg)
Molting
Stages between molts are termed instars
- this is when actual tissue growth occurs, although there’s no size increase until after the molt
Cuticle is weakened enzymatically, then animal crawls out
After molting, animal sucks in air/water to inflate new cuticle, which then hardens
![Page 8: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/8.jpg)
Molting
![Page 9: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/9.jpg)
Arthropod Cross Section
Muscles anchor on inside of cuticle, connect into the jointed appendages on each segment
![Page 10: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/10.jpg)
Heart arteries hemocoel collecting vessels
pericardium ostia heart
Open Circulatory System
![Page 11: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/11.jpg)
Arthropod Success 2: Tagmosis
Success as a group is due largely to diversity of body form, possible because of specialization of segments, regions, + appendages
Tagmosis = segments are grouped together + specialized for particular functions greater efficiency
- head, thorax and abdomen are tagmata, regions specialized for performing different tasks
- arise from spatially restricted expression of Hox genes and other developmental regulatory genes
![Page 12: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/12.jpg)
Segmentation + Tagmosis
Head Thorax Abdomen
![Page 13: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/13.jpg)
Arthropod Success 3: Jointed Appendages
How do you move without cilia? Jointed appendages (limbs) + specialized muscles to move the limb pieces, or podites
- extrinsic muscles connect to body wall- intrinsic muscles are contained entirely inside the limb
Ancestral condition, found in crustaceans, is to have biramous limbs: each limb has 2 branches
Uniramous (1 branch) - insects
Biramous - crustaceans
![Page 14: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/14.jpg)
SUB-PHYLA:
Trilobitomorpha: Trilobites (extinct)
Cheliceriformes: Chelicerates Pycnogonids
Crustacea: Crustaceans
Hexapoda: Insects
Myriapoda: Centipedes, Millipedes
Phylum Arthropoda
![Page 15: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/15.jpg)
Most common group of fossil arthropods- once abundant in oceans- disappeared by Paleozoic (345 million yr ago)
SubPhylum Trilobitomorpha (Extinct)
Cephalon
Thorax
Pygidium
![Page 16: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/16.jpg)
SUB-PHYLA:
Trilobitomorpha: Trilobites (extinct)
Cheliceriformes: Chelicerates (spiders, scorpions, and horseshoe crabs)
Pycnogonids
Crustacea: Crustaceans
Hexapoda: Insects
Myriapoda: Centipedes, Millipedes
Phylum Arthropoda
![Page 17: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/17.jpg)
~ 65,000 spp.Cheliceriformes spiders, scorpions, and horseshoe crabs
- Body of 2 tagmata: cephalothorax + abdomen
- 1st pair of appendages = chelicerae (look like fangs)
- no antennae
- Gas exchange by book gills, book lungs or tracheae
- Separate sexes
![Page 18: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/18.jpg)
Phylum Arthropoda SubPhylum Cheliceriformes
Class Pycnogonida – “Sea Spiders”
Class Chelicerata SubClass Merostomata
Order Eurypterida – extinct giant sea scorpions Order Xiphosura – Horseshoe crabs
SubClass Arachnida- scorpions, spiders, ticks, mites
SubPhylum Cheliceriformes
2 groups are marine
![Page 19: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/19.jpg)
~1,000 spp.
- marine, intertidal to abyssal depths; worldwide distribution
- benthic, live on seaweeds or other invertebrates
- sucking proboscis on 1st head segment used to feed on soft- bodied invertebrates
- males: brood eggs on ovigers, special leg appendages
- females: hollow legs filled with eggs
Pycnogonida: Sea spiders
![Page 20: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/20.jpg)
1st segment Ovigerous leg, used by males for brooding eggs
chelicera
![Page 21: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/21.jpg)
Phylum Arthropoda SubPhylum Cheliceriformes
Class Pycnogonida – “Sea Spiders”
Class Chelicerata SubClass Merostomata
Order Eurypterida – extinct giant sea scorpions Order Xiphosura – Horseshoe crabs
SubClass Arachnida- scorpions, spiders, ticks, mites
SubPhylum Cheliceriformes
2 groups are marine
![Page 22: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/22.jpg)
SubClass MerostomataOrder Xiphosura – Horseshoe crabs
5 living species (all others extinct)
- inhabit shallow marine waters
- burrow just under sand surface, prey on buried animals like bivalves
- small chelicerae
- limited distribution: Limulus polyphemus restricted to east coast of North America
- distinctive telson, or tail spine
![Page 23: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/23.jpg)
Horseshoe crab: Limulus
prosoma
opisthosomabook gills
telson
anus
cheliceraepedipalp:1st walking leg
4 pairs ofwalking legs
![Page 24: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/24.jpg)
- once very abundant on beaches in the Atlantic
- heavily harvested to make feed for farm animals
![Page 25: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/25.jpg)
>60,000 spp.
- opisthosomal (abdominal) appendages absent, or modified as spinnerets for spinning silk proteins into webs
- no compound eyes
- gas exchange by tracheae or book lungs
…Scorpions, spiders, mites, ticks
SubClass Arachnida
![Page 26: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/26.jpg)
SUB-PHYLA:
Trilobitomorpha: Trilobites (extinct)
Cheliceriformes: Chelicerates (spiders, scorpions, and horseshoe crabs)
Pycnogonids
Crustacea: Crustaceans (crab, lobster, shrimp)
Hexapoda: Insects
Myriapoda: Centipedes, Millipedes
Phylum Arthropoda
![Page 27: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/27.jpg)
SubPhylum Crustacea- body of 3 tagmata: 5-segmented head, thorax, abdomen
- cephalic shield or carapace present to protected dorsum
- mandibles, modified limbs, act as jaws; 2 pairs of antennae
- biramous limbs (2 forks)
- “gills” actually legs modified for gas exchange
- excretion by nephridia (glands near antennae)
- simple ocelli + compound eyes (often stalked)
- nauplius larva, which molts and goes through several instars
~75,000 spp.
![Page 28: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/28.jpg)
Crustacean Head
23
54
15-segmented head, each segment with its own appendages
thorax limbs, “borrowed” by the head
![Page 29: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/29.jpg)
Crustacean Head
If 1st thoracic segment fuses with head, its appendages grow as maxillipeds
- next segment is thus 2nd thoracic
5 segments 1st antennae= antennules
2nd3rd
1st
thorax
head
![Page 30: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/30.jpg)
External Anatomy of a Crayfish
![Page 31: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/31.jpg)
Crustacean limbsBranches join at base, the protopod
Inner branch = endopod
Outer branch = exopodprotopod
endopod
exopod
body
![Page 32: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/32.jpg)
Crustacean limbsBranches join at base, the protopod
- extensions on outer side = epipods- often flattened; function as gills, gill cleaners
- extensions towards the body = endites- often form a spiny,
grinding surface
Inner branch = endopod
Outer branch = exopod
endopodexopod
body
epipodendites
![Page 33: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/33.jpg)
Arthropod limbs
Protopod
Epipod
Endopod
Exopod
Endites
![Page 34: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/34.jpg)
Class Malacostraca - crabs, shrimps, lobsters
Class Maxillopoda - ostracods, barnacles, copepods
Class Branchiopoda - brine shrimp, tadpole shrimp
Class Remipedia - small cave-dwellers; basal lineage
Class Cephalocarida - small benthic detritivores; basal
SubPhylum Crustacea
![Page 35: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/35.jpg)
Class Malacostraca
Pereopods, orwalking legs
Pleopods, orswimming legs
Thorax segmentsAbdomen
telson
Body of 19 segments: head, 5 thoraxthorax, 8
abdomen, 6 + telson (tail)
![Page 36: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/36.jpg)
Class Malacostraca – 19 body segments (5-8-6 body)
3 major Super-orders:
Hoplocarida - stomatopods (mantis shrimps)
Eucarida - krill, crabs, shrimps, lobsters
Peracarida - isopods, amphipods, mysids
Class Maxillopoda - ostracods, barnacles, copepodsClass Branchiopoda - brine shrimp, tadpole shrimpClass Remipedia - small cave-dwellers; basal lineageClass Cephalocarida - small benthic detritivores; basal
SubPhylum Crustacea
seen in today’s lab
![Page 37: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/37.jpg)
Vicious predators, snagging prey with raptorial limbs
Class Malacostraca (5-8-6 body) SuperOrder Hoplocarida Order Stomatopoda
= 2nd pereopod
![Page 38: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/38.jpg)
Class Malacostraca (5-8-6 body) SuperOrder Eucarida
Order Euphausiacea (krill)
Krill form feeding swarms, especially at poles - primary food source for many whales
![Page 39: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/39.jpg)
Class Malacostraca (5-8-6 body) SuperOrder Eucarida
Order Euphausiacea (krill)Order Decapoda (14,000 spp.)
InfraOrder: Caridea (shrimps) Astacidea (crayfish) Palinura (lobsters) Brachyura (true crabs)
Anomura (hermits, king crabs) Thalassinidea (ghost shrimp)
3 maxillipeds, leaving 5 pairs of pereopods (hence name) - at least one pair usually modified as chelae, or claws
Large carapace covering head, branchial chamber
decapod =“10 feet”
![Page 40: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/40.jpg)
Order Decapoda, Infraorder: Palinura Brachyura (lobsters) (true crabs)
Crab abdomen reduced, folded under thorax
- 5th walking legs modified for swimming
Abdomen
Carapace
5th walking leg
![Page 41: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/41.jpg)
Order DecapodaInfraorder Brachyura (true crabs)
![Page 42: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/42.jpg)
Order Decapoda Infraorder Anomura (hermit + king crabs)
- 3 to 4 pairs of walking legs
- 5th leg reduced, often gill cleaner
sand crab
hermit
King crab
![Page 43: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/43.jpg)
Both the 1st & 2ndantennae are betweenthe eyes in theanomurans
![Page 44: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/44.jpg)
Order DecapodaInfraorder Caridea (shrimp)
![Page 45: - Body divided into segments, or somites, regionally fused into specialized groups by tagmosis (i.e., 5 segments form head) - Each body segment has a pair](https://reader030.vdocuments.net/reader030/viewer/2022032702/56649ce15503460f949ac975/html5/thumbnails/45.jpg)
Development in Crabs
In decapods, the nauplius stage occurs inside the egg
Pelagic stages are zoea, then megalops (transparent juvenile)
Crab zoea larva