Arthropods

1. Arthropods

2. Arthropods: Most Successful Group Ever! • Insects cause huge economic losses (but a lot of benefits, as well) each year • Negatives • Compete for humans for food supplies • Spread serious _________ • Positives • _____________ flowers • Food, yield drugs and dyes, create silk, honey and beeswax • They are the dominant group of animals on the earth today • The diversity of insects is far greater than all other taxa combined • There are an estimated _____ million insects alive foreveryhuman today

3. Locust Outbreaks in Africa (still today) • Contain 40-80 million insects per sq. kilometer • Can cover up to 20% of earth’s surface at peak times

4. Phylum Arthropoda • Arthropods includes spiders, scorpions, ticks, mites, crustaceans, millipedes, centipedes, insects, and some smaller groups as well • There is a rich fossil record extending back to the mid-____________ period

5. Ecological Relationships • They are found in all environments and virtually all altitudes and latitudes • Species are adapted to land and to fresh, brackish, and marine water • Most species fly to their favored habitats • All modes of feeding occur among arthropods though the majority are ___________ • Nothing else matches their diversity

6. Arthropods are invertebrates that have jointed appendages. There are over a million known species making them the largest group of animals. Why so diverse and abundant??? jointed appendage - Jointed ______________** - _________ symmetry (cephalization**) - Exo__________** Exoskeleton (made of chitin) bilateral symmetry General Characteristics: Arthropods Characteristics: - Segmented bodies** - Coelom and _______blastic - Body Systems** - Complex behavior patterns** - ____________ sexes (most)

7. Evolutionary Milestone: _______________ Arthropods have various appendages. They are differentiated and specialized for walking swimming, flying, or eating. Typically each segment has a pair of jointed appendages (may be reduced though). They can also be equipped with sensory hairs for sensory functions.

8. - Some arthropod have many segments - Others have fused segments or somites that form body regions (tagma or tagmata) Segmented Bodies The bodies of arthropods are divided into segments similar to those of segmented worms. However, two things: Unlike annelids, arthropods have various patterns of segmentation. And segmentation in these two groups evolved independently!!!

9. Segmented Bodies

10. All arthropods have a hard, outer covering called an _________________. - The exoskeleton cannot grow as the animal grows, thus many species molt (or ecdysis) Exoskeleton - Covers, supports, and protects the arthropod, without sacrificing _______ - Made of ________ (tough polysaccharide) and the protein resilin - Many land-dwelling arthropods have a waxy layer to prevent water loss.

11. Exoskeleton • Cuticle (exoskeletion) consists of: • Epicuticle: outer, thin layer • Procuticle: inner, thicker layer that is flexible and prevents water loss • Divided into two parts: • Exocuticle-secreted before a molt • Endocuticle-secreted after molting • Cuticle may be soft or like a coat of armor. • Other functions: ingrowth for muscle attachment, support tracheae

12. www.emc.maricopa.edu www.teleological.org Dragonfly eyes • Respiration – marine • arthropods have ______; land arthropods have a series of tubes inside (trachea) and spiracles (pores) on body surface. Oxygen pumped directly to tissues. • Cephalization- have large heads, slender necks, intricate eyes and other sensory organs, important for arthropod success.

13. Other Body Systems…. • ___________ Digestive System: • With adapted mouthparts • Specialized gut • Complex Muscular System: • Exoskeleton for attachment • Striated muscles for rapid action • Smooth muscles for visceral organs

14. More Body Systems….. • Nervous system • Similar to annelids • Dorsal brain • Double nerve cord connecting ventral ganglia • Circulatory System • ________ system • Dorsal pumping heart • Reproduction • Sexes usually _________ • Usually ____________ fertilization

15. Phylum Arthropoda Subphylum Trilobita Subphylum Chelicerata Class Merisomata (horseshoe crabs) Class Pycnogonida (sea spiders) Class Arachnida (spiders, mites, ticks, scorpions) Mandibulata Subphylum Myriopoda (centipedes, millipedes) Class Diplopoda (millipedes) Class Chilopoda (centipedes) Subphylum Crustacea Class Branchiopoda (water fleas, sea-monkeys) Class Ostracoda (seed shrimps) Class Cirripedia (barnacles) Class Peracarida (Isopoda, slaters, woodlice) Class Malacostraca (shrimps, prawns, crabs, lobsters, crayfish, yabbies) Subphylum Insecta Class Apterygota (wingless insects e.g. earwigs) Class Pterygota (winged insects)

16. Taxonomy • Subphylum Uniramia used to exist • Recently divided into two subphyla • Myriapoda • Hexapoda Arthropods are classified based on types of appendages present and number of tagmata (body regions)

17. Evolutionary Relationships • Relationships controversial • Clade Mandibulata- has mandibles • Myriapods, Hexapods, Crustaceans • Hypothesis highly debated • Excludes Spider with Chelicerae (fangs) Subphylum Trilobita is the sister taxon to all other arthropods • Now extinct

18. Debated Clades

19. Subphylum Trilobita • Trilobita arose before the Cambrian, flourished, and then becameextinct250 million years ago • They have a trilobed body shape due to a pair of longitudinal grooves • They were bottom dwellers and probably were scavengers • They ranged from an inch to 20 inches or more and could roll up like pill bugs

20. Subphylum Chelicerata • Include the horseshoe crabs, spiders, ticks, mites, scorpions, and sea spiders • Chelicerates have _______pairs of appendages including chelicerae, pedipalps and _______pairs of legs (how classified!) • They lack mandibles and antennae • Most suck liquid food from prey

21. Chelicerata: Class Merostomata • Includes the modern horeshoe crab; Limulus polyphemus • This species is nearly unchanged from its Cambrian ancestor (Eurypterids; lived 200-500 mya) • Five species survive today

22. Class Merostomata: The Horseshoe Crab • Most live in shallow water (North American Atlantic coast) • They have an unsegmented carapace that covers the body in front of a broad abdomen • A ______________ or spinelike tail • Book gills are exposed on some of the abdominal appendages • They walk with their walking legs and swim with abdominal plates • They feed at __________ on worms and small molluscs

23. Horseshoe Crabs

24. Chelicerata: Class Pycnogonid- Sea Spiders • They vary from a few millimeters to centimeters; all have small, thin bodies • Some males use legs to carry developing eggs • The mouth at the tip of a proboscis, drinks juices from cnidarians (hydroids) and soft-bodied animals • They have a greatly reduced abdomen attached to an elongated cephalothorax (tagmata)

25. Chelicerata: Class Arachnida-Spiders, etc. • Consists of a great diversity among scorpions, mites, ticks, daddy longlegs and others • Of 80,000 species, most are free living and more common in warm, dry regions • Arachnids are divided into a cephalothorax and abdomen (tagmata)

26. Order Araneae: JUST Spiders • About ________ species of spiders are known • The body consists of an unsegmented cephalothorax and abdomen joined by a slender pedicel (waistline!)

27. Order Araneae: The Spiders • The anterior appendages are a pair of chelicerae with terminal fangs • All spiders are ____________, mostly on insects, which are killed by poison • The injected __________ liquefies and digests the tissues which are then sucked into the spider’s stomach • Spiders breath by book lungs and/or trachae

28. Characteristics of the spiders • Book lungs are found only in the spiders; parallel air pockets extend into a blood-filled chamber • Air enters the chamber through a slit in the body wall • The tracheae system is less extensive than in insects; it carries air directly to tissues • Spiracles are openings to the trachea • Most spiders have ______ simple eyes, each with a lens, optic rods and a retina • They detect movement and may for images • Sensory _________ detect air currents, web vibrations, and other stimuli

30. Web-spinning Habits • __________________is a critical ability for spiders and some other arachnids • Two or three pairs ________________ contain microscopic tubes that run to silk glands • A liquid protein secretion hardens as it is extruded from the spinnerets • Silk threads are very strong and will stretch considerably before breaking • Spiders are often camouflaged or cryptic

31. Web-spinning Habits • Jumping spiders (Salticidae) have excellent vision and stalk their prey • Silk is used for orb webs, lining burrows, forming egg sacs, and wrapping prey • Wolf spiders, jumping spiders, and fisher spiders chase and catch their prey

32. Spider Diversity

33. Reproduction in spiders • ______________ court ____________ before mating • The male spins a small web, deposits a drop of sperm on it, and then stores the package in his pedipalp • Mating involves inserting the pedipalps into the female genital openings and depositing the spermatophore • Sperm are stored in a seminal receptacle for weeks or months until the eggs are ready • Eggs may develop in a cocoon in the web or may be carried by the female • The young hatch in a few weeks and may molt before leaving the cocoon

34. Venomous spiders • Most are feared for no reason at all!! • Spiders help to control the populations of insects • American tarantulas rarely bite and the bite is not dangerous • The black widow (Lactrodectusmactans) however, can be fatal • The venom is neurotoxic (attacks nervous system) • The brown recluse spider, Loxosceles recluse, has hemolytic venom that destroys tissue around the bite • Some Australian and South American Spiders are the most dangerous and aggressive

35. Black Widow

36. Brown Recluse

37. Order Scorpionida: Scorpions • More common in tropical and subtropical (such as Florida!) zones but do occur in temperate areas • They are eat at ____________ and feed largely on insects and spiders • The short cephalothorax has the appendages and 1 to 6 pair of eyes • The postabdomen has the long slender tail of five segments that end in a _______________ • Scorpions bear live young carried on the mothers back

38. Scorpions

39. Order Opiliones: Harvestmen • Harvestmen or____________________ are common, especially in tropical areas • Unlike spiders, their abdomen and cephalothorax join broadly without a narrow pedicel • They can lose one or more ________ of their eight without ill effect • Their chelicerae are pincer-like and they feed more as scavengers than do spiders

40. Harvestmen

41. Order Acari: Ticks and Mites • They are medically and economically the most important arachnids • Their mouthparts are on the tip of the anterior capitulum • They are both aquatic and terrestrial; some parasitize vertebrates and invertebrates • About 40,000 species have been described; many more are estimated to exist

42. Diversity of mites and ticks • House mites are free-living and cause __________ • Spider mites are one of the many important agricultural pest mites that suck out plant nutrients • Chiggers are larval Trombicula mites; they feed on dermal tissues and cause ________________ • The hair follicle mite Demodex is harmless but related species cause mange in domestic animals • Ticks are usually larger than mites • Tick species of Ixodes carry _____________ disease • Tick species of Dermacentor transmit Rocky Mountain Spotted Fever • The cattle tick transmits Texas cattle fever

44. Subphylum Myriapoda • Includes the centipedes, millipedes, pauropods and symphylans • Several classes have _____tagmata – a head and trunk with paired appendages on the trunk • Myriapods only have one pair of antennae, mandibles, and maxillae • Legs are always uniramous(NOT __________) • Respiration occurs through the body surface, trachea, or gills in juveniles

45. Class Chilopoda: Centipedes • Centipedes are terrestrial carnivorous ________________ found under logs, bark and stones eating earthworms, cockroaches and other insects • Their flattened bodies have up to 177 segments

46. Class Chilopoda: Centipedes • Each segment, except the one behind the head and the last two, bears 1 pair of appendages • Appendages of the first body segment form venom claws • The head has a pair of eyes on either side of the head that consist of groups of ocelli • A pair of spiracles in each segment allows air to diffuse through branched air tubes of the trachae • The sexes ar separate; all are oviparous and the young resemble the adults • One genus of house centipede has 15 pairs of legs and another has 21 pairs • Most are harmless to humans but a few large, tropical centipedes are dangerous

47. Class Diplopoda • Millipedes have many legs, but not a thousand as they are sometimes called • Their cylindrical bodies have from 25 to 100 segments • Two pairs of legs are present per segment, probably from the fusion of two segments • Each abdominal segment has two pair of spiracles opening into air chambers and tracheal air tubes • Most eat decayed plants but a few eat living plant tissue so they are _______________ • After copulation, the female lays eggs in a nest and guards them • Larvae have only one pair of legs to each segment

48. Millipedes

49. Subpylum Crustacea • _________species include lobsters, crayfish, shrimp, crabs, and copepods • Most are aquatic, and free living, many are sessile, commensal, or parasitic • The main distinguishing characteristic of crustaceans is that they have _____ pairs of antennae • The head also has a pair of mandibles and two pair of maxillae

50. Typical Body Plan