Arthropods Blue print for Success Arthropod Characteristics Includes

Arthropods Blue print for Success

Arthropod Characteristics • Includes crayfish, lobsters, spiders, mites, scorpions, and insects • Metamerism modified by the specialization of body regions for specific functions (tagmatization) • Chitinous exoskeleton, support and protection • Paired jointed appendages, ventral nervous system • Growth accompanied by molting, metamorphosis • open circulatory system, complete digestive tract

Exoskeleton • Major reason for Arthropod success • Provides structural support, protection, impermeable surfaces to prevent water loss, and a system of levers for attachment of muscles and movement • Exoskeleton made of two layers • -outer of waxy lipoprotein, prevents dehydration and impermeable to microorganisms • -Inner of chitin, tough polysaccharide and protein • Hardens by deposition of calcium carbonate • Joints had to be incorporated with flexible membrane

Exoskeleton

Exoskeleton

Exoskeleton

Exoskeleton • Molting is necessary to permit growth, 4 steps • -Enzymes secreted to separate exoskeleton from procuticle • -New procuticle is secreted • -Animal swells by air or water intake, old exoskeleton is split along ecdysal lines • New exoskeleton hardens by addition on calcium carbonate, takes few hours to days and animal is vulnerable, remains hidden

Molting

molting

Exoskeleton

Arthropod Anatomy • Hemocoel serves as a cavity for the open circulatory system, the rigid exoskeleton means the coelom is no longer a hydrostatic skeleton • Internal organs are bathed in body fluids to exchange nutrients, wastes and sometimes gases • Metamorphosis- radical change in body form from larva to adult, eliminates competition between larval and adult stages for food

Subphylum Trilobitomorpha • Trilobite body has three longitudinal sections thus the name • Dominant life form in the cambrian period 600 million years ago to 345 million years ago • Body was oval, flattened and could roll into a ball for protection • Appendages had two lobes Biramous, inner for walking and outer had spikes for digging

Trilobite

Trilobite

Trilobites

Subphylum Chelicerata • Spiders, mites, ticks, horseshoe crabs and sea spiders • Two Tagmata: cephalothorax- contains sensory, feeding and locomotion structures Opisthosoma- contains digestive, reproductive, excretory and respiratory organs • First pair of appendages are pincerlike or chelate (claws) or specialized hollow fangs • Pedipalps- second pair appendages, sensory or feeding, locomotion • Third pair appendages walking legs

Class Arachnida • Majority of spiders mites ticks and scorpions are harmless or beneficial to humans • Sea scorpions dated to 425 million years ago and other arachnids date to 345 million years ago • Most are carnivores, either pour or inject enzymes over prey and digested tissue is eaten or sucked in • The front portion of the gut is modified into a pumping stomach, mid gut and hind gut complete digestion

Arachnid Anatomy • Nitrogenous wastes are collected with coxal glands or malpighian tubules, both collect nitrogenous wastes from blood • Coxal exit at bottom of posterior appendages • Malpighian tubles deposit excretory wastes into gut tract and exit with digestive wastes • Book lungs exchange gases thru lamella that air passes thru from ventral slit on abdomen • Trachea are tubules which deliver air directly to body tissues exit thru side of abdomen

Order Araneae Spiders- largest order of Arachnids Chelicerae with poison glands and fangs Six to eight eyes Spinnerets- conical projections associated with silk glands • Silk is a protein, different types produced for different sections of web • Stronger than Kevlar (steel) Elastic • Safety Line, Ballooning, wrap eggs • •

Spider Multiple Eyes, Setae

Spider

Order Acarina • Mites and Ticks, many are ectoparasites, some free living terrestrial and aquatic • Chelicerae and pedipalps are modified for piercing, biting, anchoring and sucking • 4 pairs of walking legs (adults) • Chiggers larva break down and suck host skin • Dust mites (allergen), scabies tunnel under human skin • Ticks transmit rocky mount. Spotted fever, lyme disease

Mite

Mite Infestations

Tick

Removing a tick

Ticks on wild Rabbit

Horseshoe Crab

Sea Spiders

Sea Spider

Sea Spiders

Order Scorpionida • Range tropical to warm temperate areas • Nocturnal and secretive Hide under logs, stones during day • Chelicera- Jaws • Chelate pedipalps- Claws • Stinger at base of postabdomen (tail) • Only a few toxic to humans in north Africa Mexico and southwest U. S. , most sting like a wasp

Scorpion

Scorpion with Babies

Subphylum Crustacea • Crayfish, shrimp, Lobster, crabs, copepods, cladocerans, fairy shrimp, isopods, amphipods and barnacles • Two pairs of antennae and Biramous appendages • Basal segment- endopodite medial ramus exopodite lateral ramus

Class Malacostraca • Crabs, Lobster, Crayfish, shrimp, mysids, Krill, isopods and amphipods • Class Decapoda crab, lobster shrimp • Shrimp muscular abdomen for swimming • Lobster, Crabs crawl on bottom • Abdomen of crabs greatly reduced • Cephalothorax- fusion of head and thorax, shield like Carapace

Maine Lobster

Florida Lobster

Ghost Crabs

King Crab

Crab Larva Zoea

Crayfish Anatomy

Crayfish Anatomy • Appendages – 1 first Antennae, shorter 2 second antennae, longer • Appendages 3 mandibles for chewing 4 maxillae food handling 5 maxillae food handling, small gill, blade called gill bailer for circulating water over gills • Appendages 6 -8 Maxillipeds sensory and food handling • Appendages 9 -13 peropods walking legs