Arthropoda

1. Arthropoda Zoology 2011-2012 Wakefield

2. General Characteristics • Largest and most diverse phylum with approximately 1 millionspecies classified and possible 100 millionmore to classify • All representatives of the Arthropod phylum possess an exoskeleton containing proteins and chitin which is a complex polysaccharide. This structure supports and protects internal structures. Arthropods show metamerism (segmentation) but most metameres are arranged into functional groups called tagmata. The exoskeleton is molted periodically to allow growth to occur, this is called ecdysis. This shedding of the cuticle occurs between 2 and 10 times before reaching adulthood

3. General Characteristics • Arthropods have an open circulatory system with a dorsal heart that pumps blood and lymph to a hemocoel body cavity

4. General Characteristics • Most arthropods are dioecious with internal fertilization. Many arthropods undergo various types of metamorphosis that convert juvenile forms to adult forms, this limits interspecies competition because juveniles usually occupy a different niche than adults Complete Metamorphosis

5. General Characteristics • Arthropod appendages are jointed with hinge-like connections that make complex limb movements possible. Some appendages are modified for special functions: • Examples: Swimmerets of Crayfish Chelicerae of Spiders

6. General Characteristics • Respiration is conducted by gills, book gills, book lungs, or trachea (air tubes) Respiratory System of Grasshopper Comparative Diagram of Aquatic vs. Terrestrial Reparatory System of Arthropods

7. General Characteristics • Excretion is by antennal glands or malphighian tubules Antennal Glands in Crustacea Malpighian Tubules in Grasshopper

8. General Characteristics • Nervous system is a dorsal brain connected to ventral ganglia. Well developed sense organs for sight, smell, touch, taste, chemoreceptors and direction. Some species have a compound mosaic eye Compound mosaic eye of arthropod

9. General Characteristics • Complete digestive system with special mouthparts modified for different methods of feeding Comparative Diagram Insecta Mouth Parts

10. General Characteristics • Complex behavior in organization and activity. Innate behavior controls much of their lives but learning also plays in important role in the lives of many

11. Representative Arthropoda Subphyla & Classes • Subphylum Trilobita – 4000 species identified, all are now extinct for 200 million years. Left a rich fossil record. Trilobite Fossils

12. Representative Arthropoda Subphyla & Classes • Subphylum Chelicerata • Class Merostomata – (horseshoe crabs – 6 species) • Horseshoe shaped carapace (exoskeleton or shell) • Tail spine called a telson • Respiration by book gills on abdomen • Five pairs of walking legs and one pair of chelicerae (mouth parts) • Widely used in research over circulation Horseshoe Crab

13. Representative Arthropoda Subphyla & Classes • Subphylum Chelicerata • Class Arachnida – (four orders including spiders, ticks, scorpions and daddy long legs) – 82, 000 species • Mostly free-living and found mainly in dry, sunny areas • Body parts made of two tagamata (body sections), the cephalothorax and abdomen. The cephalothorax usually bears one pair of chelicerae, four pair of walking legs, and a pair of pedipalps • Most arachnids are predators and have fangs, claws, poisonglands or stingers

14. Representative Arthropoda Subphyla & Classes • Subphylum Chelicerata • Class Arachnida

15. Orders of Arachnida • Order Araneae (spiders) 35,000 species • Body made of two tagmata: prosoma and opisthosoma; both un-segmented and joined by a narrow waist joined by a pedicel. Anterior appendage called chelicerae hold the fangs. Pedicel

16. Orders of Arachnida • Order Araneae – • After a spider seizes a prey with its pedipalps and injects poison with its fangs, it liquefies the tissues with a digestive fluid and sucks the broth. Some spiders have teeth that crush or chew prey mixing the venom. Spider eating wasp

17. Orders of Arachnida • Order Araneae – • Spiders have 8 simple eyes and sensory setae which are sensitive hairs that cover its body surface and act as triggers to signal the location of its prey

18. Orders of Arachnida • Order Araneae – • Spiders and insects have unique excretory systems of malphighiantubules which collect urinary waste and drain into the intestine

19. Orders of Arachnida • Order Araneae – • Production of silk in silk glands produces the webs of spiders. The silk is formed from a schleroprotein which hardens when it hits the air. Spider silk is stronger than steel threads of the same diameter. They will stretch one-fifth (1/5) of its length before breaking

20. Orders of Arachnida • Order Araneae – • The most dangerous spiders in the US are the black widow which uses a neurotoxin and the brown recluse (fiddleback) which uses a hemotoxin Black Widow Spider Brown Recluse Spider Brown Recluse Spider Bite

21. Orders of Arachnida • Order Scorpionida • (Scorpions) • All the appendages are located on the short cephalothorax • The long slender abdomen ends in a tail with a barb. The stinger consists of a bulbous base that contains the poison and a curved spine that injects the venom.. Venom of most species is not fatal to humans but may be very painful, however the sting of one species in Africa and one in Mexico can be fatal unless antivenin is administered. Scorpions feed mainly on spiders and insects. They have from 1-100 offspring that the mother carries on her back • Scorpions can live for up to 15 years

23. Orders of Arachnida • Order Opiliones (Harvest Men) – 3000 species • Commonly known as Daddy Long-Legs • Different than spiders, cephalothorax and abdomen are one broad region without a pedicel • Can lose most of their long spindly legs without ill effects • They feed as scavengers • They have very poisonous venom but not a threat to humans because they have no fangs and their mouths are too small to bite

24. Orders of Arachnida • Order Acari (ticks and mites) 30,000 species identified • The most medically and economically important arachnid class • Adult ticks and mites possess 4 pair of legs and the larva possess 3 pair of legs • Chiggers are larval Trombicula mites, they feed on human dermal tissue and cause irritation of the skin • There are several tick species that carry serious illnesses, ex. Ixodes carries Lyme disease Tick Mite

25. Chigger Life Cycle And Chigger Infestation of Human Skin

26. Subphylum Crustacea(Shrimp, Lobster, Crab, Crayfish) Banded Coral Shrimp Lobster Crayfish Crab

27. Subphylum Crustacea(Shrimp, Lobster, Crab, Crayfish) • Only arthropods with 2 pair of antennae • One pair of appendages on each body segment • All appendages are biramous (have two main branches) Biramous appendage – two main branches

28. Subphylum Crustacea(Shrimp, Lobster, Crab, Crayfish) • Body sections are usually the cephalothorax and abdomen • Dorsal covering is called the carapace • Last part of the tail region bears the anus and is called the telson • (Sides of the tail are called the uropods)

29. Subphylum Crustacea(Shrimp, Lobster, Crab, Crayfish) • Have gills for respiration. Special maxillary appendages called gill rakers wave continuously to draw water over the gills. • Most crustaceans brood eggs in chambers or sacs attached to the abdomen or attached to abdominal appendages • Most crustaceans have a larvae unlike the adult form and is called the naupilus; it must undergo metamorphosis Fairy Shrimp Naupilus

30. Classes of Subphylum Crustacea • Class Branchiopoda (fairy shrimp and water fleas) – very small • Flattened leaf-like legs function in respiration • Mostly freshwater – swim with jerky flea-like motions Fairy Shrimp Water Flea

31. Classes of Subphylum Crustacea • Class Maxillopoda • Subclass Cirripedia (barnacles) • Originally classified as molluscs because of heavy shell which is really a highly modified carapace • Are filter feeders and remain attached to a substrate Barnacle

32. Classes of Subphylum Crustacea • Class Maxillopida • Subclass Copepoda (Plankton) • Most abundant organism is marine and freshwater plankton • Some free-living copepods are intermediate hosts of human parasitic tapeworms and nematodes Plankton Mostly Microscopic Organisms

33. Class Malacostraca • Large class – accounts for 70% of crustaceans • (only focus on a few of the most important Orders for study) • Order Isopoda – pill bugs, only truly terrestrial crustaceans Pill Bugs

34. Class Malacostraca • Order Amphipoda – similar to pill bugs, some marine and some freshwater of terrestrial, commonly called sand fleas or beach hoppers

35. Class Malacostraca • Order Decapoda (10 legged) 10,000 species • (Lobster, Shrimp, Crab, Crayfish) • Most are marine; some freshwater, a few crabs can live on land • First three appendages are modified as maxillipeds– for food handling • One or more walking legs are chelate and may be very large (largest is the Japanese Crab with a chelae of over 10 feet (4 meters) Japanese Spider Crab

36. Class Malacostraca • Order Decapoda • The head and thorax is fused into a cephalothorax which is covered by a carapace that encloses gill chambers • Most are either predators or scavengers • This is a very important order both commercially and environmentally Japanese Spider Crab

37. Sub-Phylum UniramiamInsects, Millipedes and Centipedes • Terrestrial or aquatic animals with uniramous appendages . . . Divided into 2 small classes and 1 huge class of insects • Class Diplopoda (millipedes) means 1000 footed • Presence of diplosegments which is derived from the fusion of 2 body segments and has 2 pair of legs per segment • Has 25 to 100 segments depending on the species • Non-aggressive but may spray an irritating fluid that can blind predators Millipede

38. Sub-Phylum UniramiamInsects, Millipedes and Centipedes • Class Chilopoda (centipedes) means margin-foot • Flatter than millipedes • One pair of legs per body segment • Fast-moving carnivore that feeds on insects, earthworms, snails and even lizards and small toads • Poisonous claws on the first segment paralyze prey • May have up to as many as 177 segments Centipede

39. Class Insecta • Class Insecta (largest class in animal kingdom - # of species estimated @ 1 million • Fundamental features of all insects: • Have 3 tagmata • Body consists of head, thorax and abdomen • Adults insets have three pairs of legs and one or two pairs of wings • Insects are found in all environments except marine • Insects play a major medical and economic role and are critical to the environment

40. Class Insecta • They can feel, taste, and hear with antenna • They usually have one pair of compound eyes • The thorax is divided into the prothorax, mesothorax and metathorax , each with one pair of walking legs

41. Class Insecta • All insects except fleas, lice and termites have wings, most have two sets except for true flies which have one set of wings and one set of halteres – used for stability

42. Class Insecta • Divided into Orders on the basis of wings and mouth part structure • There are about 40 Orders in this class but we will study only 14

43. Class Insecta • Order Ephemeroptera (Mayfiles) • Adults only live one day • Adults have no gut and do not feed – only reproduce • Larvae live for a year or more underwater • Have four membranous wings Mayfly

44. Class Insecta • Order Odonata (dragonflies and damselflies) • Are found near water • Larvae are aquatic and carnivorous • As adults, are flying predators Dragonfly (Notice wing structure)

45. Class Insecta • Order Orthoptera (grasshoppers, crickets) • Most are herbivorous with mouthparts adapted for chewing • Wings are folded under leathery forewings, in some species wings are reduced or absent in adults • Praying mantis are carnivorous • Undergo incomplete metamorphosis Cricket Grasshopper

46. Class Insecta • Order Isoptera (termites) • Live on cellulose from wood and depend on microbes in their gut to digest this indigestible product • Are social insects living in damp tunnels • Shed their tiny membranous wings @ maturity Immature Termite with Wings Adult Termite

47. Class Insecta • Order Mallophaga (chewing lice) • Serious pests of birds and other livestock • Eat bits of skin scraped from the host Chewing Louse

48. Class Insecta • Order Anoplura (sucking lice) • All are blood-sucking ectoparasites of mammals • Two species attach humans; head and pubic lice (crabs) Sucking Louse

49. Class Insecta • Order Thysanoptera (thrips) • Primarily plant feeders that suck sap from leaves and flowers • Serious pest of cultivated plants and can transmit plant diseases Onion Thrip

50. Class Insecta • Order Hemiptera (true bugs such as stinkbugs, water striders, and bedbugs • Some, such as the bedbug, have piercing mouthparts to suck blood or ingest plant sap • Have leathery front half of wing and membranous back half • Wings are held flat over abdomen Stink Bug