3.

4.

5.

6.

1.

2.

Versatile exoskeleton Segmentation and appendages for more efficient locomotion Air piped directly to cells Highly developed sensory organs Complex behavior patterns Reduced competition through metamorphosis

  Highly protective, yet highly mobile Exoskeleton: several layers of cuticle   covering secreted by underlying epidermis Procuticle  Inner, thicker cuticle  Composed of chitin bound with protein     Crustaceans procuticle impregnated with calcium salts (hardness) Divided into two parts:  Tough, resistant, nitrogenous polysaccharide that is insoluble in water, alkalies, and weak acids Exocuticle (secreted before a molt)  Endocuticle (secreted after molting) Epicuticle   Thin Composed of protein and lipids

 Ecdysis (molting)

 Each segment has a pair of jointed appendages  can be modified:  Segments and appendages can be specialized for adaptive functions  Limb segments- hollow levers moved by striated muscles (good for rapid actions)  Jointed appendages- equipped with sensory hairs  Modified for sensory functions, food handling, and swift/efficient walking or swimming

 Land arthropods   Highly efficient tracheal system of air tubes Tubes deliver oxygen directly to tissues and cells for high metabolic rate  Aquatic arthropods  Breath mainly from some form of gill

 Arthropods are very alert to environmental stimuli  Compound (mosaic) eyes  Other senses of:      Touch (what organ system?) Smell (what organ system?) Hearing (what organ system?) Balance (what organ system?) Chemical reception (what organ system?)

 Innate behavior  Unlearned behavior controls much of what arthropods do      Learned behavior Habituation (ignore repeated harmless stimuli) Imprinting (colony scents) Classical conditioning (food scents) Waggle dance (bees)

 Larval forms  Quite different from adults = less competition within species  Larval forms adapted for fulfilling a different niche than adults  Different foods  Different habitats

 Subphylum Trilobita  Subphylum Chelicerata  Subphylum Crustacea  Subphylum Myriapoda  Subphylum Hexapoda

 Extinct for over 200 million years  Abundant during the Cambrian & Ordovican periods  Named for tri-lobed shape of body caused by a pair of longitudinal grooves  Bottom dwellers, probably scavengers  Could roll up like rollie-pollies

 Horseshoe crabs, spiders, ticks, mites, scorpions, sea spiders, etc  Characterized by:      Two tagmata Six pairs of appendages    Pair of chelicerae Pair of pedipalps Four pairs of walking legs (exception: horseshoe crabs) No mandibles No antennae Most suck liquid food from their prey

 Subclass Xiphosurida  Class Pycnogonida  Class Arachnida   Order Araneae Order Scorpionida   Order Opiliones Oder Acari

 Dates from Cambrian period  Practically unchanged back to Triassic Period  Lives in shallow water along North American Atlantic coast  Swims (awkwardly) with abdominal plates; walks with walking legs  Feed at night – worms & small mollusks

 Physical Features:      Carapace: Unsegmented, horseshoe-shaped, and hard dorsal shield Broad abdomen Telson: long spine-like tailpiece Book gills: flat leaf-like gills  Exposed on some abdominal appendages One pair chelicerae and 5 pairs of walking legs

 Physical Features:   4 pairs of thin, walking legs Pair of ovigers (ovigerous legs)  Males carry egg masses on these legs    Reduced abdomen Elongated cephalothorax Large suctorial proboscis: suck juices from hydroids and soft-bodied animals  Ocean-dwellers  Few mm in length

 uber diverse: > 50,000 species described  Includes: spiders, scorpions, pesudoscorpions, whip scorpions, ticks, mites, harvestmen (daddy longlegs), etc…  Arachnid tagmata: cephalothorax & abdomen

 >35,000 species worldwide  Predacious    Feed mainly on insects Chase prey, ambush prey, or trap them in silk net Feeding:  Chelicerae function as fangs with ducts from venom glands   Digestive enzymes liquefy tissue so broth can be sucked up Some have teeth at base of chelicerae to crush or chew in addition to use of enzymes  Physical Features  Tagmata joined by pedicel  Narrow, waist-like structure connecting cephalothorax & abdomen

 2 or 3 spinnerets contain hundreds of microscopic tubules connect to abdominal silk glands  Silk thread created when liquid protein secretions hardens on contact with air  Fun facts:    silk threads stronger than steel threads of same diameter 2 nd in torsional strength (fused quartz fiber is 1 st ) Threads will stretch 1/5 of their length before breaking   webs used for: Trap insects, line nests, form sperm webs or egg sacs, build draglines, make bride lines, warning threads, molting threads, attachment discs, nursery webs, or to securely wrap prey

Drag Lines Orb Webs Orb Webs Egg Cases

 Most spiders are harmless to humans  Australia has some of the deadliest spiders (they have some of the deadliest organisms actually) 

Atrax robustis

 South America has a few dangerous spiders too 

Phoneutria fera

 In the U.S.

 Black widows 

Latrodectus mactans

  Venom is neurotoxic (acts on the nervous system) Shiny black, red hourglass on ventral side of abdomen  Brown recluse 

Loxosceles reclusa

  Venom is hemolytic (destroys tissues and skin surrounding bite) Brown, violin-shaped dorsal stripe on cephalothorax

 Book lungs or tracheae (or both)   Book lungs- many parallel air pockets extending into a blood-filled chamber  Air enters chamber by a slit in body wall Tracheae- system of air tubes that carry air directly to tissues from opening called

spiracles

    

Malpighian tubules

K, other solutes & wastes secrete into tubules Tubules drain urine-like fluid into intestines Rectal gland reabsorb K & H20   Wastes like uric acid Nearly dry mixture of urine & feces left Great adaptation (especially for arid conditions)- conserve fluids 

Coxal glands

 Modified nephridia open @ base (coxa) of first & third walking legs

 8 simple eyes     Lens, optic rods, retina Perception of moving objects May form images for hunting/jumping spiders Generally poor vision    Sensory setae Hair-like structures that sense surroundings  i.e. air currents, changing tensions in the spider’s web Web vibrations allow spider to sense size/activity of its prey, mate, or predator

     Courtship rituals before mating Indirect mating    Male deposits sperm on a web he has spun prior to mating Sperm package picked up/stored in cavities of pedipalps Pedipalps = second pair of appendages that males use to transfer sperm into a female’s genital opening Females can store sperm packets in seminal receptacle until eggs are ready (weeks or months) Females lay fertilized eggs in silken cocoon  Carries around or attaches to web or plant Cocoon may contain hundreds of eggs  Eggs hatch and young remain in egg sac for a few weeks feeding and growing for several molts

 Range: tropical, subtropical, some temperate zones  Secretive: hiding in burrows or under objects by day; feeding @ night  Predacious: insects & spiders  Reproduction   Bear live young Mother carries on her back until after their first molt  Venom can be fatal in a few species from Africa, Mexico, Arizona, New Mexico, Australia, etc…  

Androctonus Centruroides

 Physical features     Claw-like pedipalps Jaw-like chelicerae Short cephalothorax  1 – 6 pairs of eyes  appendages   segmented abdomen Preabdomen- broad Postabdomen- tail-like; ends in a stinging apparatus that injects venom

 Physical Features    Broad joining of abdomen with cephalothorax without pedicel Presence of external segmentation of abdomen 4 pairs of long, spindly legs  Legs can regenerate  Ends of chelicerae are pincer-like  Scavenger feeders  Fun Fact: NOT the most poisonous spider.

They do not even have venom glands!

 Habitat: fresh/saltwater, vegetation, ground, parasitic on vertebrates/invertebrates  >25,000 species  Many of which are important to humans  Physical Features   Fused cephalothorax & abdomen (no external tagmatization) Capitulum- little anterior projections carrying mouthparts

 Many free living  Dermatophoides farinae live in house dust and cause allergies & dermatoses  Aquatic species (mostly fresh, some marine)   Long, hair-like setae on legs for swimming Larvae may be parasitic on aquatic inverts   Spider mites (Family Tetranychidae) Agricultural pests on fruit trees, cotton, clover, etc…

 Genus Trombicula   Larvae are called chiggers or redbugs Feed on dermal tissues of terrestrial vertebrates  Process:   Cause irritating dermatitis Some species transmit Asiatic scrub typhus  Genus Demodex  Hair-follicle mites



Feeding

 Pierce skin; suck blood until distended; drop off; digest meal  Molts; feeds again 

Disease vectors

 Carry protozoans, rickettsial, viral, bacterial, and fungal organisms 

Genus Ixodes



Lyme’s Disease



Genus

Dermacentor

  Rocky Mountain spotted fever tularemia 

Boophilus annulatus

(cattle tick)

 Texas cattle fever (red-water fever)

Lobsters, crayfishes, shrimp, crabs, water fleas, copepods, and barnacles

 >67,000 species  Primarily aquatic (mainly marine), few terrestrial  Free living; can be sessile, commensal, parasitic  Important to aquatic ecosystems and economy

 2 pairs of antennae  Mandible and two pairs of maxillae  Typically pair o’ biramous appendages on each segment (except first antennae)  Gills (no malpighian tubules)  16-20 segments (> 60 segments)  Major tagmata: head, thorax, abdomen  Varying degrees of fusion  Carapace- dorsal cuticle of head covers/fuses with some/all thoracic & abdominal segments; clamshell-like vales that cover most/all body; covers entire cephalothorax not abdomen

 Foliaceous   Flat & leaf-like maxillae  Biramous   2 branches Swimmerets, maxillipeds, uropods, antennae  Uniramous   1 branch Walking legs

 Swimmerets- abdominal appendages, biramous  Endopod- inner branch of swimmerets  Exopod- outer branch of swimmerets  Protopod- basal segments, endo/exopods attached to  Maxillipeds- 1 st  Chelipeds- 1 st chela 3 pairs of thoracic appendages pair of walking legs enlarged with

 Gonopods- 1 st pair of abdominal swimmerets used for copulation for males, nursery for eggs/young for females  Uropods- last pair of appendages; paddles for backward movement  Telson- uropods & telson protect young/eggs

 Epidermis-endocuticle-exocuticle-epicuticle  Exoskeleton must be molted during maturation and growth  Molting occurs in steps 1.

2.

3.

4.

Old procuticle separates from epidermis, which secretes a new epicuticle As a new exocuticle is secreted, mottling fluid dissolves old endocuticle, and solution products are reabsorbed @ ecdysis, the old epicuticle and exocuticle are discarded In postecdysis, new cuticle is stretched and unfolded and endocuticle is secreted



Chromatophores

  Pigments in specialized branched cells Change color by:  Concentrating pigment granules in center of cells, which causes lightening  Dispersing pigment throughout each cell, which causes darkening 

Neurosecretory hormones

 

Neurosecretory cells in eyestalk control pigment behavior Hormones control:



Pigment in eyes for light & dark adaptation



Control rate and amplitude of heartbeat



Androgenic glands



Secretions stimulate expression of male sexual characteristics

 Controls molting 

Molt-inhibiting hormone

  created by neurosecretory cells in the X-organ of the eyestalk released through sinus glands in the eyestalk  Level of hormone decreased 

Molting hormone

  produced by Y-organs near mandible Initiates premolt

 Mandibles/maxillae involved in ingestion  Maxillipeds hold/crushes food  Suspension feeders   Plankton, detritus, bacteria Use legs to create water currents that sweep food particles through fringe of setae  Scavengers  Larvae, worms, crustaceans, snails, fishes  Predatory   Lygiosquilla- a walking leg has specialized digit that can be drawn into a groove and released to pierce passing prey Alpheus- enlarged chela that forms bubble that implodes to stun prey (like cocking a gun)

 Crayfish  2-part stomach  Gastric mill in 1 st  stomach Food shredded by mandibles ground by 3 calcareous teeth into fine particles that will pass to 2 nd stomach  Particles pass into intestines for chemical digestion

 Some small crustaceans breath through body surface  Gills    Vary in shape: tree-like, leaf-like, filamentous Associated blood vessels or sinuses Attached to appendages usually  Movement through H 2 O keeps gills ventilated 

Branchial chambers



Protected by overlapping carapace

 Open circulatory system    Heart (compact or tubular) Arteries transport blood to different areas of hemocoel Movement of organs and limbs circulates blood more effectively in open sinuses than heartbeats and capillaries  Blood   May contain respiratory pigments  Hemocyanin (decapods)  hemoglobin   Property of clotting to prevent loss of blood in injuries

 Excretory & osmoregulatory organs are paired glands in head 

Antennal glands/Maxillary glands/green

glands (decapods)- Excretory pores opening @ base of antennae or maxillae  Some wastes diffuse through gills as well as excretory glands  Waste products: ammonia with some urea and uric acid

 Cerebral ganglion    Located above esophagus sends nerves to anterior sense organs Connect to a subesophageal ganglion by a pair of connectives around esophagus  Double ventral nerve cord has a ganglion in each segment that sends nerves to viscera, appendages, & muscles  Giant fiber systems  Sensory organs     Eyes Statocysts- balance organs Tactile setae (on cuticle) Chemosensitive setae (on antennae, antennules, & mouthparts)



Median (nauplius) eyes

   2-3 pigment cups containing retinal cells may have lens Found in nauplius larvae and in some adults 

Compound eyes

    can be on moveable eyestalks (i.e. crabs/crayfish) Detect motion, analyze polarized light Wide visual field due to convex corneal surface Composed of ommatidia

 Mainly dioecious   Barnacles monecious (cross-fertilization) Parthenogenic in some ostracods  Most brood their eggs    Branchiopods/barnacles- special brood chamber Copepods- attached egg sacs to abdominal sides Malacostracans- carry eggs and young attached to appendages    Life Cycles Crayfish juvenile small version of adult Most produce larvae that must go through series of changes as it molts  Nauplius- unsegmented body, frontal eye, three pairs of appendages (2 pairs of antennae & mandibles)  Post-larval forms vary among subphyla



Class Branchiopoda

    Order Anostraca Order Notostraca Order Conchostraca Order Cladocera 

Class Maxillopoda

    Subclass Ostracoda Subclass Copepoda Subclass Branchiura Subclass Cirripedia 

Class Malacostraca

    Order Isopoda Order Amphipoda Order Euphasiacea Order Decapoda

 Physics Features  Reduced 1 st antennae  2 nd maxillae 

Phyllopoda

    Flattened, leaf-like legs Main respiratory organs Suspension feeding Locomotion

 Order Anostraca   Fairy shrimp; brine shrimp Lack a carapace  Order Notostraca   Tadpole shrimp (i.e. Triops) Carapace forms large dorsal shield covering most trunk segments  Order Conchostraca   Clam shrimp (i.e. Lynceus) Bivalved carapace encloses entire body  Order Cladocera    Water fleas (i.e. Daphnia) Carapace covers body, but not head Large portion of freshwater zooplankton

 Physical features:  Segmented  5 cephalic, 6 thoracic, 4 abdominal   Telson Maxillopodan eye in the nauplii

 Subclass Ostracoda       Marine, fresh H2O habitats Clam-like….bivalved carapace Several trunk segments fused # of thoracic appendages reduced to 2 or 0 Burrow in sediments Scavenge food, feed on detritus, suspension feeding

 Subclass Copepoda        Free-living in planktonic & benthic habitats (marine & fresh) 1 0 consumer in many aquatic niches Many symbiotic, some parasitic Small, elongate, tapered toward posterior Lacks carapace Simple, median, nauplius eye Appendages  4 pairs of flat, biramous, thoracic swimming appendage   5 th pair reduced No legs on abdomen

 Subclass Branchiura    Parasitize marine or freshwater fish 5-10 mm long Physical features:  No gills      Broad, shield-like carapace Compound eyes 4 biramous thoracic appendages for swimming Short, unsegmented abdomen 2 nd maxillae modified as suction cups

 Subclass Cirripedia      Barnacles Burrowing or parasitic forms Enclosed shell of calcareous plates Sessile as adults  Some can attach to substrate by a stalk      Physical features: Carapace (mantle) surrounds body, secretes calcareous-plated shells Reduced head No abdomen Long thoracic legs Many-jointed cirri with hair-like setae  Cirri extend through small opening between the plates to filter feed



Largest class of Crustacea & diverse



Marine & freshwater



Physical features:

   8 thoracic segments 6 abdominal segments Each segment has a pair of appendages

 Order Isopoda      Asellus- freshwater Ligia- sea beaches, rocky shores Porcellio & Armadillidium- terrestrial under stones or damp places (rollie pollies) Some parasites of fish or other crustaceans Physical features:  Dorsoventrally flattened    No carapace Sessile compound yes Gills on abdominal appendages

 Order Amphipoda    Marine and freshwaters Orchestria- beach fleas Physical features:  No carapace    Sessile compound eyes Compressed laterally gills on thoracic segments

 Order Euphausiacea  Important as oceanic plankton- “krill”  Uber important in ocean ecosystems   3-6 cm long Eaten by baleen whales and many fishes

 Order Decopoda   Lobsters, crayfish, shrimps, crabs Physical features:  5 pairs of walking legs   First pair of legs modified to form chelae True crabs have broader carapace & reduced abdomen

 Ura (fiddler crabs) – burrow in sand just below high-tide  Decorator crabs- cover carapace with sponges and sea anemones as camouflage  Libinia (hermit crabs)- live in snail shell; abdomen not protected by exoskeleton

Centipedes, millipedes

 2 tagmata: head & trunk  One pair of antennae  Mandibles & 2 pairs of maxillae (1 pair in millipedes)  Uniramous legs  Respiratory system: respiratory exchange through body surface and tracheael systems (aquatic juveniles may have gills)

 Centipedes  Predators- earthworms, insects  Dioecious & oviparous  Physical features:    Somewhat flattened dorsoventrally Can have up to 177 segments Segments bear one pair of appendages  First body segment- modified- venom claws   Head with pair of eyes Respiration- tracheal tubes with pair of spiracles @ each segment



Scutigera

 15 pairs of legs 

Scolopendra

 21 pairs of legs

 “double footed”  Millipedes- “thousand feet”  Herbivorous  Females lay eggs in nest and guards it  Physical features    25-100 segments 4 thoracic segments- 1 pair of legs Abdominal segments  2 pairs of legs on each  2 pairs of spiracles on each  Larva have 1 pair of legs per segment