ARTHROPODS Phylum Arthropoda 08 Sept. 2014 Arthropoda.ppt 1
Phylum Arthropoda Phylum Arthropoda Greek: arthro = jointed, + pod = foot Huge group, > 1,000,000 species. estimate: 1,000,000 spp. arthropods 1,190,000 spp. animals ~ 84% of all animal species are arthropods!! 08 Sept. 2014 Arthropoda.ppt 2
Body pla n Phylum Arthropoda Tube-in-tube, bilateral symmetry, protostomous, split coelom Marine, aquatic, terrestrial even Antarctica! Cell and tissue organization Triploblastic, complex organs ~ 30,000 genes in genome, (same as for mammals) 08 Sept. 2014 Arthropoda.ppt 3
Phylum Arthropoda Huge group, > 1,000,000 species. How can we explain the success of the arthropods? Exoskeleton! 08 Sept. 2014 Arthropoda.ppt 4
Phylum Arthropoda Exoskeleton of chitin and protein (= cuticle) structure: epicuticle (oily, waxy) exocuticle (chitin & protein) endocuticle (chitin only) epidermis secretes cuticle 08 Sept. 2014 Arthropoda.ppt 5
Problems associated with exoskeleton. Problem 1. MOVEMENT Solution: Joints in exoskeleton. arthro-, = joint -pod, = leg, foot Exocuticle absent from joints; may form hinges. Endocuticle alone allows flexibility. 08 Sept. 2014 Arthropoda.ppt 6
Problems associated with exoskeleton. Problem 2. GROWTH Solution: Molting 08 Sept. 2014 Arthropoda.ppt 7
Molting (1) Secretion of "molting fluid" to dissolve old endocuticle. 08 Sept. 2014 Arthropoda.ppt 8
Molting (2) New cuticle formed under old exocuticle. Break out of old cuticle Old cuticle breaks at line of weakness 08 Sept. 2014 Arthropoda.ppt 9
Molting (3) Inflate with water/air to increase size while skeleton soft, but soft skeleton & gravity limit size; arthropods are mostly small. Hardening of new exocuticle. 08 Sept. 2014 Arthropoda.ppt 10
Growth stages Arthropod passes thru 3-20+ growth stages in life cycle. Some stop molting as adults (insects, most spiders) Some continue to molt (crayfish, tarantulas) 08 Sept. 2014 Arthropoda.ppt 11
Problems associated with exoskeleton. Problem 3. SENSORY INPUT touch sensory setae connected to neurons smell & taste hollow sensory setae w/ chemosensitive nerve endings 08 Sept. 2014 Arthropoda.ppt 12
Problems associated with exoskeleton. Problem 3. SENSORY INPUT vision clear cuticle over compound or simple eyes 08 Sept. 2014 Arthropoda.ppt 13
Problems associated with exoskeleton. Problem 3. SENSORY INPUT hearing tympanum = endocuticle, vibrates like eardrum trichobothria (right ) 08 Sept. 2014 Arthropoda.ppt 14
Support Locomotion Benefits of Exoskeleton: lever system walk, swim, fly to individuals: Mechanical protection (armor) Retards evaporation (in air) and/or osmosis (in water) water balance. 08 Sept. 2014 Arthropoda.ppt 15
Benefits of Exoskeleton: to the phylum: Reduction of coelom & segmentation Abandoned hydrostatic system of annelid-like ancestor) Coelom reduced to pericardial cavity Segments fused = Tagmosis Specialization of body regions (= tagmata) Specialization of appendages 08 Sept. 2014 Arthropoda.ppt 16
Tagmosis Head (~ 4-6 segments) feeding, sensation Head appendages mandibles, maxillae, maxillipeds, chelicerae antennae 08 Sept. 2014 Arthropoda.ppt 17
Tagmosis Thorax (~ 3-6 segments) locomotion, grasping. Thoracic appendages walking legs, wings chelipeds 08 Sept. 2014 Arthropoda.ppt 18
Tagmosis Abdomen (~8-30+ segments) respiration, reproduction, etc. Abdominal appendages abdominal gills (aquatic insect larvae) swimmerets (crayfish) filtering legs (barnacles) gonopods (crayfish, etc.) spinnerets (spiders) 08 Sept. 2014 Arthropoda.ppt 19
Tagmosis Number of segments/legs in each tagma varies by subphylum, class. Cephalothorax of 6 segments in Chelicerata 1 pr. chelicerae 1 pr. pedipalps 4 pr. walking legs Cephalothorax of 13 segments in Crustacea (shrimps) 2 pr. antennae 1 pr. mandibles 2 pr. maxillae 3 pr. maxillipeds 5 pr. walking legs (1 st pair modified as chelipeds) 08 Sept. 2014 Arthropoda.ppt 20
Phylum Arthropoda Ways the needs of cells are met Food Herbivores, predators, detritivores, parasites, filter feeders,... O 2 and CO 2 exchange Gills usu. modified legs, Book lungs, Tracheal systems Waste removal Diffusion from gills, Malphigian tubules 08 Sept. 2014 Arthropoda.ppt 21
Other arthropod characters Open circulatory system Dorsal heart pumps hemolymph over brain Hemolymph moves through hemocoel back toward heart Ostia (holes) in sides of heart let hemolymph in to go around again. 08 Sept. 2014 Arthropoda.ppt 22
Phylum Arthropoda Special concerns of a multicellular animal Circulation: Open circulatory system, (analogous to that in Mollusca) Dorsal aorta Hemocoel Pores (ostia) valved Text fig. 42.3 08 Sept. 2014 Arthropoda.ppt 23
Other arthropod characters Respiratory systems Gills in aquatic/marine arthropods Book lungs (modified gills) in spiders & scorpions Tracheal systems in most terrestrial arthropods 08 Sept. 2014 Arthropoda.ppt 24
Other arthropod characters Nervous system resembles that of annelid Dorsal brain with nerves around esophagus Paired ventral nerve cords Segmental ganglia Often fused into 1-2 ganglia in each tagma 08 Sept. 2014 Arthropoda.ppt 25
Phylum Arthropoda Special concerns of a multicellular animal Circulation: Open circulatory system, Coordination, Complex sensory organs, nervous system Structural support & Movement Exoskeleton & muscles Maintenance of homeostasis water balance. 08 Sept. 2014 Arthropoda.ppt 26
Phylum Arthropoda Reproduction Usually sexual, some parthenogenic 08 Sept. 2014 Arthropoda.ppt 27
Distinguishing Characters of Arthropoda Jointed exoskeleton Tagmosis Compound eyes 08 Sept. 2014 Arthropoda.ppt 28
Classification of Arthropoda Subphylum Trilobita Subphylum Chelicerata Subphylum Myriopoda Clade Pancrustacea Subphylum Crustacea (polyphyletic) Subphylum Hexapoda 08 Sept. 2014 Arthropoda.ppt 29
Classification of Arthropoda Subphylum Trilobita Class Trilobita Three-lobed head & body (left, middle, right) Diverse in Paleozoic ~540-240 MYA Extinct 08 Sept. 2014 Arthropoda.ppt 30
Classification of Arthropoda Subphylum Chelicerata Cephalothorax Jaws are chelicerae Pedipalps 4 pr. Walking legs Abdomen 08 Sept. 2014 Arthropoda.ppt 31
Classification of Arthropoda Subphylum Chelicerata Class Horseshoe crabs Horseshoe crabs Scorpions?? 08 Sept. 2014 Arthropoda.ppt 32
Classification of Arthropoda Subphylum Chelicerata Class Arachnids Lost compound eyes Spiders Daddy-long-legs vinegaroons mites & ticks more Scorpions?? 08 Sept. 2014 Arthropoda.ppt 33
Classification of Arthropoda Subphylum Myriapoda Legs unbranched Head & body Class Centipedes 1 st legs are fangs 08 Sept. 2014 Arthropoda.ppt 34
Classification of Arthropoda Subphylum Myriapoda Class Millipedes Double segments (2 pr. legs per segment) 08 Sept. 2014 Arthropoda.ppt 35
Classification of Arthropoda Clade Pancrustacea Subphylum Hexapoda Subphylum Crustacea 2 pr. Antennae (antennules, antennae) Cephalothorax 13 segments & appendage pairs Abdomen variable among Classes 08 Sept. 2014 Arthropoda.ppt 36
Classification of Arthropoda Subphylum Crustacea Class crabs Class barnacles 08 Sept. 2014 Arthropoda.ppt 37
Classification of Arthropoda Subphylum Hexapoda Class Insects Head, thorax, abdomen 2 pr. Wings ~800,000 species, majority of all arthropods 08 Sept. 2014 Arthropoda.ppt 38
Classification of Arthropoda Subphylum Hexapoda Class Insects Incomplete metamorphosis Dragonflies Orthoptera Hemiptera, Homoptera Complete metamorphosis Coleoptera (beetles) Hymenoptera (wasps, ants, bees) Diptera (flies) 08 Sept. 2014 Arthropoda.ppt 39
Why are Arthropods so successful? Exoskeleton tagmosis evolution of flight speciation 10 6 species of insects. 08 Sept. 2014 Arthropoda.ppt 40
Why are Arthropods so successful? Exoskeleton protection from water loss early colonization of land head start. Arthropods were diverse and widespread on land before vertebrates! 08 Sept. 2014 Arthropoda.ppt 41