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Terrestrial Mandibulates. Chapter 20. Uniramia. Uniramians are mostly terrestrial arthropods. A few live in freshwater. Only one pair of antennae. Appendages uniramous as adults. Tracheae carry respiratory gases directly to/from all body cells. Uniramia.
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Terrestrial Mandibulates Chapter 20
Uniramia • Uniramians are mostly terrestrial arthropods. • A few live in freshwater. • Only one pair of antennae. • Appendages uniramous as adults. • Tracheae carry respiratory gases directly to/from all body cells.
Uniramia • Myriapods (many footed) include ClassChilopoda, Diplopoda, Pauropoda & Symphyla. • Two tagmata: head & trunk. • Paired appendages on most trunk segments.
Uniramians • Class Insecta • Three tagmata: head, thorax & abdomen. • Appendages on head & thorax, reduced or absent on abdomen.
Class Chilopoda • Centipedes – class chilopoda – contain a few or many segments each (except the first behind the head and the last two) with a pair of jointed legs. • Last pair of legs has a sensory function.
Class Chilopoda • Head appendages: • One pair antennae • One pair mandibles • One or two pairs of maxillae. • Dorsoventrally flattened.
Class Chilopoda • Sexes are separate. • Some lay eggs (oviparous). • Some have live young (viviparous). • Young like little adults – no metamorphosis.
Class Chilopoda • Centipedes live in moist environments. • They are carnivores, feeding on insects & worms. • Prey is killed with poison claws on the first segment.
Class Diplopoda • Millipedes (Class Diplopoda) have two pairs of legs on each segment. • Head has one pair each of antennae, mandibles, & maxillae. • Body is more cylindrical.
Class Diplopoda • Millipedes live in dark, moist places – under rocks or logs. • Most are herbivores, feeding on decayed plant matter or occasionally living plants. • Slow moving, coil up when disturbed. • Toxic or repellent fluids secreted when disturbed.
Class Insecta • Insects are the most diverse and abundant of all arthropods. • 26 orders • Most are terrestrial or inhabit freshwater. • Few are marine.
Class Insecta • Insects have: • 3 Tagmata: head, thorax, abdomen. • 3 pairs of legs and usually 2 pairs of wings on their thorax.
Class Insecta • Insects show a diverse array of morphological variation. • They consistently have 3 tagmata. • Head – compound eyes, one pair antennae, 3 ocelli, mouthparts (including mandibles & maxillae) • Thorax – 3 segments each with a pair of legs, the last 2 segments usually have wings as well. • Abdomen – 9-11 segments
Class Insecta • Antennae can act as tactile organs, olfactory organs, and sometimes auditory organs.
Class Insecta • Legs have also become highly specialized for walking, grasping, skating over water, and specialized jobs like gathering pollen.
Class Insecta • Flight is one key to the great success of insects. • An animal that can fly can escape predators, find food, and disperse to new habitats much faster than organisms that can only crawl.
Class Insecta • Insects are the only invertebrates that can fly. • Most have two pairs of wings. • Some are ancestrally wingless – silverfish. • Some are secondarily wingless – fleas.
Class Insecta • The internal anatomy of an insect includes several complex organ systems.
Insects - Nutrition • Most insects are herbivorous, feeding on plant juices and/or tissues. • Some are specialized, others will eat almost any plant.
Insects - Nutrition • Some insects are predaceous, catching & eating other animals.
Insects - Nutrition • Other insects are scavengers or parasites.
Insects - Nutrition • Some insect parasites are parasitized by other insects – hyperparasitism. • Parasitoids are a lethal type of parasite. • A tiny wasp lays eggs on the tomato hornworm. The wasp larvae will consume the hornworm.
Insects - Nutrition • Insects have mouthparts specialized for the many different foods they eat. • Sucking mouthparts (mosquitoes) – form a tube, can pierce animal or plant tissues.
Insects - Nutrition • Sponging mouthparts (house flies) – liquid food is lapped up, food may be liquefied first.
Insects - Nutrition • Chewing mouthparts (grasshoppers) – strong plates can tear food.
Insects – Circulation & Gas Exchange • Insects have an open circulatory system. • Gas exchange is accomplished with a tracheal system – an extensive network of thin-walled tubes that branch into every part of the body. • Tracheal trunks open to the outside by spiracles.
Insects – Circulation & Gas Exchange • Insects & spiders have independently evolved an excretory system of Malpighian tubules – blind tubules opening into the hindgut. • Potassium is secreted into the tubules and water diffuses in after it. Other solutes and wastes are secreted or diffuse into the tubules as well.
Insects – Circulation & Gas Exchange • Insects that feed on dry grains must conserve water and excrete salts. • Leaf-feeders ingest & excrete lots of fluid. • Aphids pass fluid as honeydew that is consumed by other insects.
Insects – Sensory Organs • Mechanoreception – Mechanical stimuli are received by sensilla (simple or complex) distributed over the antennae, legs, and body.
Insects – Sensory Organs • Auditory Reception – Very sensitive setae or tympanal organs detect vibrations that come through the substrate or the air. • Some moths detect ultrasonic pulses emitted by bats. They drop toward the ground in response to avoid the bats.
Insects – Sensory Organs • Chemoreception – Chemoreceptors for taste and smell are located in sensory pits on the mouthparts, antennae or sometimes the legs.
Insects – Sensory Organs • Visual Reception – Simple eyes (ocelli) are used to monitor light intensity, they do not form images. • Compound eyes in insects, similar to those of crustaceans, consist of thousands of ommatidia, each having its own pigment cells and lens.
Insects – Sensory Organs • Different insects have different capability to see color. • Bees can distinguish most colors (they don’t see red) beginning in the ultraviolet range. • To us a flower may look uniformly colored, but to the bee there are lines that appear in the UV range that act as nectar guides. • Other insects, like butterflies, can see red.
Insects - Reproduction • Sexes are separate, some are parthenogenetic. • Fertilization is internal. • In some, like butterflies, nutrients are passed to the female as well as sperm.
Insects - Reproduction • Insects have a variety of methods for attracting mates. • Pheremones play an important role in many species. • Fireflies communicate using light flashes. • Crickets communicate using sound.
Insects - Reproduction • Female insects deposit eggs on a specific habitat that will provide food for larvae. • Monarch butterflies lay eggs on milkweed plants. • Parasitoid wasp species lay eggs on tomato hornworms. • Mosquitoes lay eggs in standing water where the larvae will live as filter feeders.
Insects - Metamorphosis • Many insects undergo metamorphosis during their development. • Each stage between molts is called an instar.
Insects - Metamorphosis • Insects with complete metamorphosis have larval stages specialized for eating and growing that are known by such names as maggot, grub, or caterpillar. • The larval stage looks entirely different from the adult stage.
Insects - Metamorphosis • Female butterflies lay eggs on the plant that the caterpillars will feed on. • After the eggs hatch, the larvae (caterpillars) eat and grow, molting many times. • When it reaches a certain size, the larva will molt one more time, becoming a pupa (chrysalis in butterflies).
Insects - Metamorphosis • Metamorphosis from the larval stage to the adult stage occurs during a pupal stage.
Insects - Metamorphosis • In incomplete metamorphosis, the young, called nymphs resemble adults but are smaller and go through a series of molts until they reach full size.
Diapause • Insects are able to undergo dormancy during harsh conditions. • Hibernation – winter dormancy • Estivation – summer dormancy • Diapause – arrested growth that occurs regardless of conditions.
Defense • Aposematic coloration – many insects utilize bright colors as a warning that they are toxic.
Defense • Batesian mimicry – when a palatable species mimics the bright colors of an unpalatable species. • Müllerian mimicry – when two unpalatable species have come to resemble each other.
Defense • Cryptic coloration – often insects are colored and patterned very much like the plants they are found on, making them very difficult to see.
Defense • Other defensive features include the exoskeleton, offensive odor (as with the stink bug), bites and stings.
Insect Behavior • Insects exhibit a wide range of behaviors involving innate behaviors, pheromones, and learning.
Insect Behavior • Fireflies use bioluminescence to signal each other. The female firefly attracts males by using a particular flash pattern. • Another firefly species mimics the call of the female and then eats the males that arrive.
Social Insects • Honey bees, ants and termites have complex social groups. • In honeybees: • The queen is the reproductive female. • Workers are non-reproductive females. • Drones are haploid males.
Social Insects • Ants have fascinating societies where they “farm” fungi, herd “ant cows” (aphids which they keep for the honeydew that they secrete), sew their nests with silk, and even use tools.
