Phylum Arthropoda

1. Subphylum Crustacea: Aquatic Mandibulates Phylum Arthropoda

2. Diversity • Over 67,000 species worldwide • Live in aquatic environments (both ocean and freshwater) • Can burrow, creep on bottom of ocean floor • Some are sessile/permanently fixed (barnacles) • Examples include: crabs, crayfish, lobster, shrimp, water fleas, brine shrimp, barnacle, daphnia, fish louse (parasite), krill, pill bugs (rolliepollies) • Called crustaceans

3. Diversity • Some are edible (lobster, shrimp, crayfish, crabs) • Others are parasites to other ocean-going organisms • Fill a wide range of ecological roles and have enormous variation • Food, bioindicators, etc • Called Mandibulates • Why? Because of the many pairs of sensory, chewing, food-handling appendages

4. Characteristics of Aquatic Mandibulates • Most have two body regions: • 1) Abdomen • Long narrow • Tail region • Includes the telsonand uropod

5. Characteristics of Aquatic Mandibulates • Most have two body regions: • 2) Cephalothorax • fused head and thorax—chest region, • appendages attached to this segment • covered by a carapace • Def: a cuticle composed of chitin, protein and calcareous material • Used for protection but is very flexible • Carapace covers most of the cephalothorax

7. Characteristics of Aquatic Mandibulates • Appendages • All appendages are biramous (two main branches) • First two pair: • Antennae (2 pair – this distinguishes them from all other arthropods) • Next pair: • Jaw-like mandibles • Used to chew and crush food • Next pair: • Maxillae • Used to hold food

8. Characteristics of Aquatic Mandibulates • Appendages, cont. • Three pairs of jaw feet called maxillipeds • Used to touch, taste and handle food • Claws for catching food • One pair of walking legs for each segment (four pairs total) • Swimmerets on the abdomen • Used for swimming and to catch sperm

10. Characteristics of Aquatic Mandibulates • Respiration • Gills (if present) • Some use diffusion for respiration • Segments • Most have 16-20 segments (some have more) • Nervous System • Nerve cord on ventral side that swells to ganglia • Digestive system • Digestive gland mixes food with digestive enzyme • Stomach, intestines, anus

11. Characteristics of Aquatic Mandibulates • Excretory system • Green gland—regulates amount of salt in body • Reproduction • Gonopores—pores that release reproductive cells • The position of these varies according to sex • Location: at the base of a pair of swimmerets or on segments without legs

12. Classification • Subphylum Crustacea • Class Remipedia • Class Cephalocarida • Class Branchiopoda • Orders: Anostraca (Fairy Shrimp, Brine Shrimp), Notostraca (tadpole shrimp), Diplostraca (water fleas, clam shrimp) Fairy shrimp Brine shrimp Water flea Tadpole shrimp

13. Classification • Subphylum Crustacea, cont. • Class Ostracoda • Class Maxillopoda • Subclasses: Copepoda, Tantulocarida, Branchiura (fish lice), Cerripedia (barnacles) • Class Malocostraca • Orders: Isopoda (pill bug), Amphipoda, Euphasiacea (krill), Decapoda (shrimps, crabs, lobsters) Fish lice Copepods

14. Classification • Decapods (Order Decapoda) • Crayfish, lobsters, shrimp, crabs • 10 walking legs • Carnivores • Eyes on stalks • first three pairs of appendages modified for eating

15. Classification • Isopods (Order Isopoda) • Pill bugs, sow bugs • Feed on dead, decaying matter • Obtain oxygen from air/moist soil • no carapace • eyes are not stalked • gills on appendages

16. Classification • Cerripeds (Subclass Cerripedia) • Barnacles • Shelled, sessile • No eyes, gills, heart or blood vessels Giant Barnacles

17. Classification • Copepods • Smallest in size • Plankton, Krill • Feed on algae • No gills or abdominal appendages

18. Crayfish External Dissection

19. Crayfish Characteristics • General Characteristics • freshwater aquatic invertebrate • typically 6 to 8 cm in length, may be as long as 12 cm • jointed exoskeleton • body consists of cephalothorax and abdomen

20. Crayfish Characteristics • General Characteristics, cont. • paired, jointed appendages • head has 2 pairs of antennae, 1 pair of mandibles, and 2 pairs of maxillae • undergoes ecdysis (shedding of the exoskeleton to accomplish an increase in body size)

21. Crayfish Characteristics • Digestive System • The digestive tract consists of: • 1) the foregut, • includes an enlarged stomach (grinding) • 2) the midgut • 3) the hindgut (functions in water and salt) regulation. • 4) anus • 5) digestive gland • secretes digestive enzymes and aids in the absorption of the products of digestion.

23. Crayfish Characteristics • Excretory System • Excretory organs are called the antennal glands • They excrete the waste products of blood filtration; • Ammonia is the primary waste product. • Ammonia is also excreted across the gill surfaces and by diffusion across thin parts of the exoskeleton.

25. Crayfish Characteristics • Respiratory System • Use gills • The gills are located in between the carapace (the exoskeleton of the cephalothorax) and the body wall. • Circulatory System • The circulatory system of the crayfish is centered around a muscular heart

27. Crayfish Characteristics • Nervous System • The crayfish nervous system is composed of a ventral nerve cord • Concentrated ganglia (anterior end) • Giant neurons in the ventral nerve cord function in escape responses.

29. Crayfish Characteristics • Endocrine System • The endocrine glands • Release hormones into the blood • The hormones control functions, such as ecdysis, sex determination, color change and regulation of heart rate

30. Crayfish Characteristics • Sensory Structures • Chemoreceptors • Tactile receptors • function in equilibrium, balance, and position senses • Statocysts • functions in movement and orientation • Ocelli (simple eye) • allows larvae to go toward or away from light • does not form images • Compound eyes • mounted on moveable eyestalks • lens system made of 14,000 individual receptors

31. Crayfish Characteristics • Sexual Characteristics and Reproduction • Crayfish have separate sexes. • Mating occurs just after the female has molted (usually in the spring). • Once they leave their mother, they begin an adult life and reach maturity in anywhere from a few months to a year. • The average life span for a crayfish is two to three years.

32. Crayfish Internal Dissection Another dissection

33. Crayfish Characteristics • Predator / Prey Relationships • Feed on living animals and plants, • Also consume a fair amount of dead plants, dead or dying animals, and detritus. • Crayfish are omnivores. • Crayfish do not prey on larger animals, such as fish

34. Terrestrial Mandibulates: Spiders and Insects Phylum Arthropoda

35. Characteristics • Segmented bodies • Jointed appendages • Specialized for eating, sensing, reproduction, defense and movement • Exoskeleton • Hard covering on the outside of the animal • Limits the growth of the organism (must shed) • Muscles are attached to this layer • Secreted by underlying epidermis • Shed (molted) at intervals

36. Characteristics • Bilateral symmetry • Muscular system • Complex • Contains two types of muscles • Body cavity • Coelom is smaller in size   • Most of body cavity consists of hemocoel (sinuses, or spaces, in the tissues) • Filled with blood

37. Characteristics • Digestion • Complete digestive system  • Esophagus, crop, gizzard, midgut, hindgut and anus • Mouthparts modified from appendages and adapted for different methods of feeding • Circulatory System • Open system • Dorsal contractile heart, arteries

38. Characteristics • Respiration • Obtain oxygen through: • 1) body surface (diffusion), • 2) gills, • 3) tracheal (air tubes) – carry oxygen to muscles • 4) book lungs • Spiracles—small openings in the exoskeleton through which air opens

39. Characteristics • Water retention—3 structures • 1) Malpighian tubules— • excretory structures that remove metabolic wastes from blood and return water to the cells • 2) Exoskeleton— • prevents water evaporation • 3) Book Lungs— • gas exchange without water loss (also used in respiration)

40. Characteristics • Excretory system • Paired excretory glands in some • Same as the nephridial system of annelids  • Some with other excretory organs, called Malpighian tubules

41. Characteristics • Nervous system • Contains same system of annelid (with dorsal brain connected by a double nerve chain) • Fusion of ganglia in some species   • Well-developed sensory organs • Compounds eyes with many lenses (can see motion and color)

42. Characteristics • Reproduction • Sexes usually separate, • Paired reproductive organs and ducts;   • Usually internal fertilization; • often go through metamorphosis (change in body form  larva to adult)

43. Classification • Phylum Arthropoda(most diverse phylum) • Subgroups of Terrestrial Arthropods: • Subphylum Chelicerata – • Characteristics of all: • six pairs of appendages that include • a pair of chelicerae, • a pair of pedipalps, and • 4 pairs of walking legs • No mandibles and no antennae.   • Suck up liquid food from their prey. • Two body segments (abdomen and cephalothorax)

44. Classification • Class Merostomata– • Horseshoe crabs are practically unchanged • Have an unsegmented, horseshoe-shaped carapace, and a broad abdomen, which has a long spine like telson. • Book gills are exposed.   • They feed at night on worms and small mollusks and are harmless to humans. • Include horseshoe crabs

45. Classification • Class Arachnida– • over 50,000 species • Body organization: cephalothorax, abdomen • Examples: Spiders (35,000 species), scorpions, ticks, mites

46. Classification • Spiders: • hunt using strong legs and good eyes; weave silk for web (hunt and reproduction); fangs are modified chelicerae (liquefy prey with venom) • Scorpions: • long, segmented abdomen with a stinger; • Mites and Ticks: • mites have one body segment, eat bacteria or skin cells of humans; ticks are mostly parasitic, require blood before molting and can cause Rocky Mtn spotted fever

47. Classification • Subphylum Uniramia– • Characteristics: • Appendages are unbranched.   • Includes the insects and the myriapods (centipedes and millipedes). • Heads resemble the crustacean head but have only one pair of antennae, instead of two. • Also have a tympanic membrane for sound  • Have mandibles and two pairs of maxillae • Respiration is by body surface and tracheal systems, • Although juveniles, if aquatic, may have gills.

48. Classification • Class Chilopoda- • They are active predators with a preference for moist places such as under logs or stones, where they feed on earthworms, insects, etc.   • Each segment (they have between 10 and 70), except the one behind the head and the last two, bears one pair of appendages. • Include: centipedes

49. Classification • Class Diplopoda– • Include Millipedes • Have cylindrical bodies made up of 25 to 100 segments. • Abdominal segments each have two pairs. • Millipedes are less active than centipedes • Generally herbivorous, living on decayed plant and animal matter

50. Classification • Class Insecta– • Most numerous and diverse of all arthropods. • (There are more species of insects than species in all the other classes of animals combined!!) • Have three pairs of legs • Usually have two pairs of wings (although some have one pair of wings, or none)   • Body organization: head, thorax, and abdomen. • The head usually bears a pair of large compound eyes, a pair of antennae, and usually three ocelli.