Where are we?

1. Where are we? Nematoda Ecdysozoa Arthropoda Tardigrada Onychophora Deuterostomia Annelida Mollusca Lophotrochozoa Platyhelminthes

2. Phylum ArthropodaSubphylum Crustacea

3. Crustacea • Terrestrial and aquatic • All depths in marine, brackish, and freshwater • > 67,000 described species, likely 5-10x that number no yet described • Diverse form, size, and habitat • 5 classes, 34 orders

4. Characteristics • Head = 5 segments, trunk divided into thorax and abdomen • Carapace or cephalic shield • Appendages multi-articulate; either uniramous or biramous • Mandibles are modified limbs that function as jaws • Gas exchange by diffusion across specialized surfaces

5. Characteristics • Excretion by nephridia • Simple and compound eyes in at least one life cycle stage • Compound eyes on stalk • Gut with digestive cecae • Nauplius larvae, either mixed or direct development • 2 pairs of antennae

6. Crustacean Bauplan • Thorax • anterior segments fused = cephalon • Maxillipeds: additional mouthparts • Number of segments in thorax varies • Thorax appendages = pereopods • swimming, walking, gas exchange, feeding, defense • ultiarticulate and biramous

7. Basic Crustacean Bauplan • Abdomen • Segments • Number of segments used in ID • Appendages = pleopods • Biramous, flap-like • swimming • Culminate in telson • Anus • caudal rami • w/uropods (last pair of abdominal appendages) forms tail fan

8. Adult Crustacean

9. Crustacean Bauplan • Nauplius Larvae • Single, median, simple eye • 3 pairs of sectioned, functional limbs • Become antennules, antennae, and mandibles

10. Diagrams • adult Crustacean diagram: • http://www.enchantedlearning.com/subjects/invertebrates/crustacean/index.shtml

11. Circulation • Open circulatory system • Dorsal ostiate heart • Internal organs bathed in fluid • Simple heart and vessels in most • Sessile species no heart; pumping vessels • Blood • Variety of cell types • Dissolved hemoglobin or hemocyanin • Explosive cells release a clotting agent at injury sites

12. Heart Shape • Heart long and tubular; to postcephalic region • Or, globular, box shape, in thorax; association with thoracic gills

13. Gas Exchange • Aquatic • Small organisms = diffusion • Concealed gills for protection, prevent dessication • External gills • Modified thoracic limbs • Gills are thin; maximize gas exchange • Most species beat gills to maintain flow

15. Gas Exchange • Terrestrial • Cutaneous Respiration • Membranes on legs of some species • Gills • Concealed • Pseudotrachea • Internal blind sacs to outside through small pores • Air in sacs, gas exchange with blood • Internal gills moist

16. Watercurrents • Hydraulic vacuum • Filter feeding • Feeding basket • Passive • Twirling antennae • Direct manipulation • Sand grazers or Sand lickers • Predators • Parasitism

17. WaterCurrents Thoracic limbs for swimming and creating suspension feeding currents • Water drawn into space • Particles trapped by setae • moved to food groove and toward head

18. Hydraulic vacuum • Mouth appendages = paddles • Water containing food drawn into interlimb space • Food particles are not filtered, but captured in small parcels of water • Individual algal cells are captured this way

19. Filter feeding • Sessile crustaceans have feathery cirri to filter feed • food up to one mm • = detritus, bacteria, algae and various zooplankton • Some can coil cirrus around large prey in a tentacle fashion

20. Filter feeding in slow water • Extend pairs of cirri like a fan • Sweep rhythmically through water

21. Filter feeding in fast water • Allow water to run through filter • video

22. Passive feeding • Use cirri to passively strain • Burrow into sand with anterior facing upward • Extend cirri to capture bacteria, protists and phytoplankton • Antennae brush food towards mouth

23. Twirl antennae • Create spiraling currents that bring food toward mouth • Food entangled in setae near base of mouth, brushed in

24. Direct manipulation • Manipulation by mouthparts, pereopods and subchelate anterior legs

25. Sand grazers or Sand lickers • Brush sand grains with setose mouthparts • Select individual sand grain, rotate and tumble against mouthparts to remove organic material

26. Predator • Grab prey with chelae pereopods • Tear, grind and shear with mouthparts • Hunters or ambushers use raptorial subchelae to stab, club or smash prey • Some hold prey in cage using endopods; others inject and suck out tissues

27. Snapping Shrimp • Use large cheliped to snap close: produces loud popping sound and “shock” wave • Pressure wave stuns prey, pull into burrow

28. Snapping Shrimp Video http://www.sciencemag.org/feature/data/1052273files/video.shl

29. Digestive system • Foregut • Lined with cuticle that is continuous with exoskeleton, molted • Short pharynx-esophagus, stomach • Stomach = chambers for storage, grinding and sorting

30. Midgut • intestine • Length varies with body shape and size, diet • digestive ceca • Hindgut • Short, to anus

31. Foregut functions • transport food to midgut and/or processing by chemical digestion • cardiac stomach = storage, bits are moved past gastric mill (sclerotized teeth for grinding) • pyloric stomach = filter large particles • midgut, hindgut and anus

32. Excretion and Osmoregulation • Ammonia by nephridia and gills • nephridial excretory organs as antennal glands (green glands) or maxillary glands • Inner blind end is coelomic remnant of nephridium = sacculus

33. Sacculus • Actively remove and secrete material from blood into excretory lumen • metabolic waste removal and water and ion balance

34. Other osmoregulation • Thin areas of cuticle • Gill surfaces • terrestrial isopods: ammonia diffuses from the body as gas

35. Nervous System and Sense Organs CNS • Brain: three fused ganglia Protocerebrum Deutocerebrum Tritocerebrum • Primitive nervous system = ladderlike

36. Nervous System and Sense Organs variety of sensory receptors • innervated setae or sensilla: contain mechanoreceptors and chemoreceptors • Propioceptors • Animals in Class Malacostraca: statocysts

37. Nervous System and Sense Organs • Two rhabdomeric photoreceptors: Median simple eyes Lateral compound eyes • Most possess both, either simultaneously or during development • Naupliar eye = primitive, secondarily lost

38. Nervous System and Sense Organs Lateral compound eyes • Lack visual acuity • Discern shapes, patterns and movement • Color vision in some • Lacking in many taxa

39. Nervous System and Sense Organs Underwater vision • Problems with angular distribution of light, lower intensity, and narrow range of wavelengths than in air • Solution: Mount eyes on stalks, increase information available to eyes. Increases field of view, and binocular range

40. Nervous System and Sense Organs Complex Endocrine and Neurosecretory Systems • Not well known • Molting, chromatophore activity, and reproduction under hormonal and neurosecretory control • Bioluminescence in several groups

41. Reproduction And Development Reproduction • Exploit virtually every life history scheme imaginable • Usually dioecious • Hermaphroditism in remipedes, cephalocarids, cirripedes, few decapods • Parthenogenesis common among branchiopods and certain ostracods

42. Reproduction And Development Reproduction Systems • Gonads paired structures in trunk • Pair of gonoducts from gonads to genital pores on trunk segment • Male pair of penes, or single fused median penis • Female include seminal receptacles

43. Reproduction And Development • Most crustacea copulate • courtship behavior • Pairing more or less permanent, or seasonal

44. Reproduction And Development Fiddler crab example Males use cheliped waving to attract females, repel competing males Males produce sounds by stridulation, substratum thumping to attract mates Mating when male entices female into burrow

45. Reproduction And Development Reproductive systems continued • Sperm transferred either loose in seminal fluid or packaged in spermatophores • Sperm deposited directly into oviduct or into seminal receptacle • Sperm can be stored for long periods