 Blueprint for Success Chapter 14 and 15

 Modified segmentation – body regions specialized for specific functions (tagmatization).  Chitinous exoskeleton used for support and protection  Paired, jointed appendages  Growth accompanied by molting (ecdysis)

 Ventral nervous system  Reduced coelom  Open circulatory system where blood is released into tissue spaces (hemocoel)  Complete digestive tract  Metamorphosis often present

 Successful in almost all habitats on the earth.  Most abundant animals – Several million species identified o 30 to 50 million species may yet be undescribed  Triploblastic, protostome development  Exhibit bilateral symmetry  Four aspects contribute to arthropod success. o 1. Metamerism o 2. Exoskeleton o 3. The Hemocoel o 4. Metamorphosis

 Segmentation, most evident externally  Each external segment bears a pair of appendages  Body cavity not divided internally  Permits the specialization of regions of the body for specific functions  Regional specialization = Tagmatization o Body regions (tagmata) specialized for: feeding, sensory perception, locomotion, visceral functions.

 External, jointed skeleton which encloses arthropods  Provides support, protection, and prevents water loss  System of levers for muscle attachment and movement  Secreted by epidermal cells o Epidermis covered by exoskeleton on outside  Consists of two layers: o 1. Epicuticle = outermost, waxy lipoprotein layer o 2. Procuticle/Endocuticle = bulky inner layer made of chitin

 Hardening of the procuticle provides armor-like protection  Modifications of the exoskeleton o Formation of joints o Sensory receptors (bristles, lenses, etc) o Gas exchange  Must be periodically shed for growth (ecdysis)

 Epicuticle and Procuticle: epicuticle exocuticle endocuticle epidermis procuticle

 Provides an internal cavity for the open circulatory system of arthropods  Allows for the exchange of nutrients, wastes, and (sometimes) gases

 Indirect development, a significant change in physiology as the immature form becomes an adult  Reduces competition between adults and immature stages

 Evolution of arthropods has resulted in an increasing divergence of body forms, behaviors, and habitats between immature and adult stages. o Ex: Larval crabs feed on plankton, adult crabs prowl sandy bottoms for live prey. o Ex: Caterpillar feeds on leafy vegetables, adult butterfly feeds on nectar from flowers.

 Examples: o Crayfish, crabs, lobster, shrimp, barnacles and copepods.  Two unique characteristics: o 1. Two pairs of antennae o 2. Biramous appendages  Five classes of crustaceans and numerous orders o Class Malacostraca** o Class Maxillopoda** o Class Branchiopoda o Class Remipedia o Class Cephalocarida

 “Soft Shell”  Largest class of crustaceans: o crabs, lobsters, crayfish, shrimp, krill, isopods  Body divided into two regions o 1. Cephalothorax (fusion of sensory/feeding and locomotion tagmata) o 2. Abdomen (a muscular tail)

 Paired, biramous appendages in both body regions  Appendages on Cephalothorax: o Pairs 1 and 2 – Antennae (TWO pairs!) o Pairs 3 through 5 – Mouth appendages Mandible Pair (Chewing) Maxillae (Food handling) o Pairs 6 through 8 – Maxillipeds Accessory sensory and food handling appendages o Pairs 9 through 13 – Pereopods (Walking legs) Cheliped (Pincher-like)  Appendages on Abdomen o Pleopods (Swimmerets) o Telson used

Reproduction  All crustaceans are dioecious  Mating occurs after molting of the female  In females, developing eggs attach to pleopods and are brooded until hatached  In males, pleopods are modified into claspers and used for sperm transfer  Crayfish have direct development

Feeding  Predators, herbivores, scavengers  Foregut includes an enlarged stomach, specialized for grinding  Midgut = “intestine”  Short hindgut ends in anus and used for water and salt regulation

Gas Exchange & Circulation  Gills in gill chamber o Between the carapace and body wall  Muscular Heart  Dorsal, anterior, and posterior arteries empty into sinuses of hemocoel Sensory & Regulation  Ventral nervous system  Compound eyes  Crayfish: Excretion organs are called “green glands”  Other crustaceans: maxillary glands

 Includes Barnacles and Copepods  Copepods are most abundant crustacean o Marine and Freshwater  Barnacles are sessile o Marine only o Most monoecious o Attach to various substrates o Some are parasitic

 Most successful land animals in terms of numbers of species and individuals  Bodies divided into three tagmata  Five pairs of head appendages  Three pairs of legs on thorax

 30 Orders within Class Insecta!  Adult Generalized Insect Characterized by: o Body divided into head, thorax, abdomen o Three pairs of legs o Two pairs of wings

 Head o Single pair of antennae o Mouthparts o Compound eyes o 0 to 3 ocelli (simple eyes)  Thorax o Three segments: prothorax, mesothorax, metathorax o One pair of legs attaches to each thoracic segment o Pair of wings attach at margin between mesothorax and metathorax  Abdomen o 10 to 11 abdominal segments

 Insects utilize many forms of locomotion: walk, run, jump, swim, but flight is perhaps the most important  Insects were the first animals to fly o Important from an evolutionary perspective!  Wings most likely evolved from outgrowths of the thorax which protects the legs  Required thermoregulation  Some insects use a synchronous (direct) flight mechanism which others use an asynchronous (indirect) flight mechanism.

 Synchronous (Direct) Flight o Used by butterflies, dragonflies, and grasshoppers. o Flight muscles act on wing bases o A single nerve impulse in flight muscles results in a single wing cycle  Asynchronous (Indirect) Flight: o Used by flies and wasps o Flight muscles act on body wall o Changes in shape of the thorax cause wing movements. o A single nerve impulse results in many cycles of the wings

 Variations in mouthparts include specializations for sucking or siphoning plant or animal fluids  Mouthparts: o Labrum- upper liplike structure, sensory and not derived from paired appendages o Mandibles- chewing mouthparts o Maxillae- have cutting surfaces and a sensory palp o Labium- sensory lower lip o All aid in food handling

 Long and straight and consists of the foregut, midgut, and a hindgut.  Foregut o Behind pharynx is a crop that is used for storage o Proventriuculus or gizzard moves food to midgut helps grind  Midgut o Aids in digestion and absorption o Gastric cecae increase surface area  Hindgut o Primarily involved with reabsorption of water

 Gas exchange with air requires a large surface area for the diffusion of gases o Accomplished through highly branched systems of chitin-lined tubes called tracheae  Tracheae open to outside of body through spiracles o Spiracles can close to prevent water loss  Most insects have ventilating mechanisms o Moves air into and out of tracheal system o Contracting flight muscles o Passive suction (vacuum) draws air in o Abdominal muscle contraction (pump)

 Open circulatory system similar to other arthropods but blood vessels less well developed  Blood carries nutrients, hormones, wastes  Blood is not important in gas exchange  Most insects are ectotherms, but some generate heat using flight muscles

 Ganglion in head region  Sense organs specialized for functioning on land  Insects are capable of some learning have a memory o Bees recognize flowerlike objects o When bees are rewarded with nectar, they will choose flowers with that same odor in subsequent trials  Capable of detecting light o Used in orientation, navigation, feeding, etc  Compound eyes are well developed in adults