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Presentation on theme: "Arthropods."— Presentation transcript:

1 Arthropods

2 Why have they achieved so much diversity and abundance?
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

3 Versatile exoskeleton
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 Tough, resistant, nitrogenous polysaccharide that is insoluble in water, alkalies, and weak acids Crustaceans procuticle impregnated with calcium salts (<flexibility, >hardness) Divided into two parts: Exocuticle (secreted before a molt) Endocuticle (secreted after molting) Epicuticle Thin Composed of protein and lipids

4 Ecdysis (molting)

5 Segmentation and appendages for more efficient locomotion
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

6 Air piped directly to cells
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

7 Highly developed sensory organs
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?)

8 Complex behavior patterns
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)

9 Reduced competition through metamorphosis
Larval forms Quite different from adults = less competition within species Larval forms adapted for fulfilling a different niche than adults Different foods Different habitats

10 Let’s explore the different subphyla
Subphylum Trilobita Subphylum Chelicerata Subphylum Crustacea Subphylum Myriapoda Subphylum Hexapoda

11 Subphylum Trilobita 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

12 Subphylum Chelicerata
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

13 Subphylum Chelicerata
Subclass Xiphosurida Class Pycnogonida Class Arachnida Order Araneae Order Scorpionida Order Opiliones Oder Acari

14 Subclass Xiphosurida: Horseshoe crabs
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

15 Subclass Xiphosurida: Horseshoe crabs
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

16 CLass Pycnogonida: Sea Spiders
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

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

18 Order Araneae: Spiders
>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

19 Spider Webs 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 2nd in torsional strength (fused quartz fiber is 1st) 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

20 Spider Webs Orb Webs Orb Webs Drag Lines Egg Cases

21 Dangerous?!? 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

22 Dangerous?!? In the U.S. Black widows Brown recluse
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

23 Body Systems

24 Respiratory System 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

25 Excretory System Malpighian tubules Coxal glands
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 base (coxa) of first & third walking legs

26 Nervous system 8 simple eyes Sensory setae 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

27 Reproductive system 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

28 Reproductive System

29 Order Scorpionida: Scorpions
Range: tropical, subtropical, some temperate zones Secretive: hiding in burrows or under objects by day; 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


31 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

32 Order Opiliones: Harvestment “Daddy longlegs”
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!

33 Order Acari: Ticks & Mites
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

34 MItes Many free living Aquatic species (mostly fresh, some marine)
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…

35 Mites Genus Trombicula Genus Demodex
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

36 Demodex

37 Ticks Genus Ixodes Genus Dermacentor Feeding
Lyme’s Disease Genus Dermacentor Rocky Mountain spotted fever tularemia Boophilus annulatus (cattle tick) Texas cattle fever (red-water fever) Feeding Pierce skin; suck blood until distended; drop off; digest meal Molts; feeds again Disease vectors Carry protozoans, rickettsial, viral, bacterial, and fungal organisms

38 Subphylum Crustacea Lobsters, crayfishes, shrimp, crabs, water fleas, copepods, and barnacles

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

40 Crustacea: Physical Features
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

41 Appendages: Form meets function
Foliaceous Flat & leaf-like maxillae Biramous 2 branches Swimmerets, maxillipeds, uropods, antennae Uniramous 1 branch Walking legs

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

43 Appendages: Form meets function
Gonopods- 1st 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

44 Body Systems

45 Integumentary Epidermis-endocuticle-exocuticle-epicuticle
Exoskeleton must be molted during maturation and growth Molting occurs in steps 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

46 Endocrine Chromatophores Neurosecretory hormones Androgenic glands
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

47 Endocrine 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

48 Digestive 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)

49 Digestive

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

51 Respiration 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 H2O keeps gills ventilated Branchial chambers Protected by overlapping carapace

52 Circulatory Open circulatory system Blood Heart (compact or tubular)
Arteries 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 transport blood to different areas of hemocoel

53 Excretory Excretory & osmoregulatory organs are paired glands in head
Antennal glands/Maxillary glands/green glands (decapods)- Excretory pores base of antennae or maxillae Some wastes diffuse through gills as well as excretory glands Waste products: ammonia with some urea and uric acid

54 Nervous 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)

55 Nervous- Two types of eyes
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

56 Nervous: Compound Eye

57 Reproductive Mainly dioecious Most brood their eggs Life Cycles
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

58 Life Cycles


60 Subphylum Crustacea Class Branchiopoda Class Maxillopoda
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

61 Class Branchiopoda Physics Features Reduced 1st antennae 2nd maxillae
Phyllopoda Flattened, leaf-like legs Main respiratory organs Suspension feeding Locomotion

62 Class Branchiopoda Order Anostraca Order Notostraca Order Conchostraca
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

63 Class Maxillopoda Physical features: Segmented Telson
5 cephalic, 6 thoracic, 4 abdominal Telson Maxillopodan eye in the nauplii

64 Class Maxillopoda 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

65 Class Maxillipoda Subclass Copepoda
Free-living in planktonic & benthic habitats (marine & fresh) 10 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 5th pair reduced No legs on abdomen

66 Class Maxillopoda 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 2nd maxillae modified as suction cups

67 Class Maxillopoda 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


69 Class Malacostraca Largest class of Crustacea & diverse
Marine & freshwater Physical features: 8 thoracic segments 6 abdominal segments Each segment has a pair of appendages

70 Class Malacostraca 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

71 Class Malacostraca Order Amphipoda Marine and freshwaters
Orchestria- beach fleas Physical features: No carapace Sessile compound eyes Compressed laterally gills on thoracic segments

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

73 Class malacostraca 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

74 Class Malacostraca Order Decapoda: Crabs
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

75 Centipedes, millipedes
Subphylum Myriapoda Centipedes, millipedes

76 Subphylum Myriapoda 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)

77 Subphylum Myriapoda Class chilopoda
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 each segment

78 Class Chilopoda Scutigera Scolopendra 15 pairs of legs

79 Subphylum Myriapoda Class Diplopoda
“double footed” Millipedes- “thousand feet” Herbivorous Females lay eggs in nest and guards it Physical features 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

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