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 Telson- tail section modified into flipper

Crayfish Anatomy Gills contained in a brachial chamber attached at bottom Blood through open system into sinuses and then thru gills before returning to heart Nervous system is ventral and ladder like, giant nerves control tail muscles for escape Statocyst at base of first antennae, contains cemented sand grains Compound eyes mounted on movable eye stalks, lens has 14,000 receptors

More Malacostraca Krill (Euphausiacea)- make up a large portion of food chain in ocean, huge population collapse 1990’s, now regulated Isopoda (pill bugs)- live under rocks, roll up in ball when disturbed, some deepwater species grow quite large Amphipoda (beach Hopper)- live in seaweed at high tide line beach.

Krill (Euphausiacea)

Isopods

Amphipoda (beach Hopper)

Brachiopoda and Maxillopoda Brachiopoda- fairy shrimp, Brine shrimp- marine and short lived, eggs can withstand drying and hatch when wet again Water fleas (Daphnia)- fresh water ponds, swim with antennae Maxillopoda –Copepods, mostly planktonic filter feeders, basis of many food webs Barnacles- sessile, attach themselves to substrate, rocks, ships, whales, docks

Brine Shrimp