Arthropoda

Characteristics of Arthropoda Segmented body (tagma & tagmatization) Hard exoskeleton (cuticle)of chiton + protein Paired, Jointed appendages – Legs, antennae, feeding parts

Exoskeleton Can be thick/rigid or thin/flexible Functions: – Structural support – Muscle attachment – Protection – Prevents/reduces desiccation Facilitated colonization of land Must be molted Energetically costly

Arthropod Systems Well developed sensory systems Eyes that produce visual images (compound & simple) Chemo (olfactory receptors) Inc. antennae which function as both chemo and tactile receptors Open circulatory system Hemocoel is main body cavity Respriatory system Aquatic  typically gills Terrestrial  internalized tubes – Tracheal system – Book lungs

Diversity 3 lineages, 4 main sub-phyla Chelicerata Myriapodia Pancrustaceans – crustaceans – Hexapoda (inc. insects)

Chelicerates (spiders, horseshoe crabs, scorpions, ticks, mites): Chelicerae – Feeding appendages (fangs or “claws”) pedipalps – sensing, reproduction, defense, manipulating food 2 body segments – cephalothorax & abdomen Simple eyes (single lens) (often multiple No antennae uniramous

Figure Scorpion Dust mite Web-building spider 50 µm

Arachnids (chelicerates) Appendages 4 pairs of walking legs chelicerae—fangs which posses poison glands Toxin contains digestive enzymes that soften & semi digest the tissues of prey and then they are slurped up the slurry. Pair of pedipalps Book lungs Internalized, highly branched from lots of gas exchange. Stacked plates with spaces between, hemolymph flows next to spaces Silk and webs: protein produced by glands in the abdomen spun by spinerette Each species produces a unique web and the spiders innately know how to create it –genetically determined behavior

Myriapods — millipedes and centipedes All living examples are terrestrial Uniramous legs Head segment: 1 pair of antanae, 3 pairs of appendages that are modified into mouthparts which includes the jawlike mandible Millipedes: Two pairs of legs/segment They are detrivores and/or herbivores Rounded in cross section Centipedes One pair of legs/segment Dorsoventrally flattened Carnivores – Poison claws (maxillaped) on the 1 st trunk segment that paralyze prey and help in defense

Crustaceans (crabs, lobsters, shrimp, krill, barnacles, isopods, copepods) exp. decapod Freshwater, marine, and some terrestrial Appendages Biramous appendages Two pairs of antennae Walking legs on thorax Swimmerets on abdomen (marine versions only) Segments: Cephalothorax – Carapace w/ calcium carbonate abdoman

Crustaceans (crabs, lobsters, shrimp, krill, barnacles, isopods, copepods) exp. decapod Gas exchange Small ones  cuticle Larger  gills Reproduction: aquatic crustanceans have larval stages Crustacean larvae help form a large part of the zooplankton Some adults (copepods) are also part of plankton Barnacles—cuticle with calcium carbonate (refered to as a shell) Filter feeders filter with feeding appendages Glue themselves to substrate

Cephalothorax Abdomen Thorax Head Eye Swimming appendages (one pair per abdominal segment) Walking legs Mouthparts (feeding) Pincer (defense) Antennae (sensory reception)

Figure 33.36

Hexapoda (6 legged arthropods – includes insects) Appendages Antennae 3 pairs of walking legs uniraous Segments 3 parts – Head – Thorax Many with two pairs of wings Extensions of exoskeleton, not limbs Adaptive advantage of flight Abdomen Reproduction: Dioecious Internal fertilization Sperm in spermatheca, fertilize egg at later time Incomplete v.complete metamorphosis

Figure AbdomenThorax Head Compound eye Antennae Anus Vagina Malpighian tubules Heart Dorsal artery Crop Cerebral ganglion Mouthparts Nerve cords Tracheal tubes Ovary

Tracheal system Pores on surface  trachea  tracheoles  tissues (perfuses all tissues) Air sacs Both gas exchange and gas transport No hemolymph involved

Malphigian Tubules Terrestrial arthropods Closed tubes in hemoceol Actively transport waste and ions (no filtration) Water follows osmotically Connects to rectum Rectum reabsorbs water and ions Nitrogenous waste (uric acid) released as solid w/ feces

Video: Butterfly Emerging

Figure (a) Larva (caterpillar) (b)Pupa (c)Later stage pupa (d)Emerging adult (e)Adult

Figure Archaeognatha (bristletails; 350 species) Zygentoma (silverfish; 450 species) Winged insects (many orders; six are shown below) Complete metamorphosisIncomplete metamorphosis Coleoptera (beetles; 350,000 species) Diptera (151,000 species) Hymenoptera (125,000 species) Lepidoptera (120,000 species) Orthoptera (13,000 species) Hemiptera (85,000 species) Proboscis

Consult your lab guide for selected details about specific insect orders