Chapter 23 Animals I: Major Invertebrate Groups (Sections 23. 11 - 23

23.11 Spiders and Their Relatives Chelicerates include horseshoe crabs and arachnids They are predators, parasites, or scavengers chelicerates Arthropod subgroup with specialized feeding structures (chelicerae) and no antennae arachnids Land-dwelling arthropods with four pairs of walking legs; spiders, scorpions, mites, and ticks

Tarantula, a Spider Chelicerates have a body with a cephalothorax (fused head and thorax) and abdomen Pedipalps, lie between the chelicerae and the first legs

Tarantula, a Spider abdomen cephalothorax pedipalps Figure 23.26 Examples of chelicerates. A Tarantula, a spider. B Horseshoe crab (Limulus). The long spine helps it steer as it swims. C Scorpion. Its last segment has a stinger and the pedipalps are claws that can seize prey. D A blood-engorged tick. E Dust mite, less than 0.5 millimeter in length. pedipalps four of eight walking legs Fig. 23.26a, p. 368

Horseshoe Crab Horseshoe crabs are an ancient chelicerate lineage and the only one that is marine Figure 23.26 Examples of chelicerates. A Tarantula, a spider. B Horseshoe crab (Limulus). The long spine helps it steer as it swims. C Scorpion. Its last segment has a stinger and the pedipalps are claws that can seize prey. D A blood-engorged tick. E Dust mite, less than 0.5 millimeter in length.

Scorpions Scorpions dispense venom through a stinger on their telson; their pedipalps evolved into large claws Figure 23.26 Examples of chelicerates. A Tarantula, a spider. B Horseshoe crab (Limulus). The long spine helps it steer as it swims. C Scorpion. Its last segment has a stinger and the pedipalps are claws that can seize prey. D A blood-engorged tick. E Dust mite, less than 0.5 millimeter in length.

Ticks and Mites All ticks are parasites Mites include parasites, predators, scavengers Figure 23.26 Examples of chelicerates. A Tarantula, a spider. B Horseshoe crab (Limulus). The long spine helps it steer as it swims. C Scorpion. Its last segment has a stinger and the pedipalps are claws that can seize prey. D A blood-engorged tick. E Dust mite, less than 0.5 millimeter in length.

23.12 Crustaceans Small crustaceans reach great numbers in the seas and are an important food source for larger animals Marine crustaceans include crabs, lobsters, barnacles, krill, and copepods crustaceans Mostly marine arthropod group with two pairs of antennae

Crustacean Diversity Figure 23.27 Examples of crustaceans. A Antarctic krill no more than 6 centimeters long. B Free-living female copepod from the Great Lakes, about 1 millimeter long. Note the eggs. C Goose barnacles capturing food with their jointed legs.

Decapod Crustaceans Lobsters, crayfish, crabs, and shrimps all belong to the same crustacean subgroup (decapods) All are bottom feeders with five pairs of walking legs – the first pair are often modified as claws Like all arthropods, they molt as they grow

Lobster Body Plan

Lobster Body Plan abdomen segments cephalothorax (fused segments) eyes (two) antennae (two pairs) food-handling appendages (three pairs) Figure 23.28 Body plan of a clawed lobster (Homarus americanus). tail fan swimmerets first leg walking legs (five pairs) Fig. 23.28, p. 369

Crab Life Cycle

Crab Life Cycle egg adult female juvenile larva Figure 23.29 Crab life cycle. Larval and juvenile stages molt repeatedly and grow in size before they are mature adults. larva Fig. 23.29, p. 369

ANIMATION: Crab life cycle To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

23.13 Insect Traits and Diversity Insects are the most diverse arthropods, and include the only winged invertebrates insects Most diverse arthropod group Members have six legs, two antennae and, in some groups, wings

Characteristic Features Insects have a three-part body plan, with a head, thorax, and abdomen Insects are mostly terrestrial; tracheal tubes carry air from surface openings to tissues deep inside the body Some insects undergo metamorphosis in which tissues of a juvenile are reorganized Some insects undergo incomplete metamorphosis, in which nymphs change a little with each molt

Basic Insect Body Plan Structures of a bedbug head, thorax, and abdomen

Basic Insect Body Plan abdomen thorax with six legs Figure 23.30 A bedbug illustrates the basic insect body plan: a head, thorax, and abdomen. The bug is 7 millimeters long. thorax with six legs head with two eyes, and two antennae Fig. 23.30, p. 370

Metamorphosis

Metamorphosis A Incomplete metamorphosis egg nymphs adult Figure 23.31 Insect development. A Incomplete metamorphosis of a bug. Small changes occur with each molt. B Complete metamorphosis of a fruit fly. A larva develops into a pupa that undergoes a dramatic remodeling into the adult form. egg nymphs adult Fig. 23.31a, p. 370

Metamorphosis B Complete metamorphosis egg larvae pupa adult Figure 23.31 Insect development. A Incomplete metamorphosis of a bug. Small changes occur with each molt. B Complete metamorphosis of a fruit fly. A larva develops into a pupa that undergoes a dramatic remodeling into the adult form. egg larvae pupa adult Fig. 23.31b, p. 370

Diversity and Abundance The four most successful insect lineages all have wings and undergo complete metamorphosis: Flies: ~150,00 species Beetles: ~ 150,000 species Hymenopterans (wasps, bees, ants): ~ 130,000 species Moths and butterflies: ~ 120,000 species

Insect Diversity

Insect Diversity Figure 23.32 A sampling of insect diversity. A Silverfish, an ancient lineage that does not undergo metamorphosis. Insects that undergo incomplete metamorphosis: B European earwig, a common household pest. C Duck louse. It eats bits of feathers and skin. D Cicada. Male cicadas are among the loudest of all insects. E Damselfly, one of the insects that has aquatic larvae. F Termites. These sterile soldiers can shoot a gluelike substance from their head to protect their colony. G Grasshopper. Members of the four most diverse insect orders. All are winged and undergo complete metamorphosis: H A fly, dusted with pollen. I Ladybird beetles with a distinctive red and black spotted wing cover. J Staghorn beetle from New Guinea. K Bald-faced hornet, a type of wasp. This is a fertile female, or queen. She lives in a papery nest with her many offspring. L Swallowtail butterfly, a lovely lepidopteran, shown acting as pollinator. Fig. 23.32a, p. 371

Insect Diversity Figure 23.32 A sampling of insect diversity. A Silverfish, an ancient lineage that does not undergo metamorphosis. Insects that undergo incomplete metamorphosis: B European earwig, a common household pest. C Duck louse. It eats bits of feathers and skin. D Cicada. Male cicadas are among the loudest of all insects. E Damselfly, one of the insects that has aquatic larvae. F Termites. These sterile soldiers can shoot a gluelike substance from their head to protect their colony. G Grasshopper. Members of the four most diverse insect orders. All are winged and undergo complete metamorphosis: H A fly, dusted with pollen. I Ladybird beetles with a distinctive red and black spotted wing cover. J Staghorn beetle from New Guinea. K Bald-faced hornet, a type of wasp. This is a fertile female, or queen. She lives in a papery nest with her many offspring. L Swallowtail butterfly, a lovely lepidopteran, shown acting as pollinator. Fig. 23.32b, p. 371

Insect Diversity Figure 23.32 A sampling of insect diversity. A Silverfish, an ancient lineage that does not undergo metamorphosis. Insects that undergo incomplete metamorphosis: B European earwig, a common household pest. C Duck louse. It eats bits of feathers and skin. D Cicada. Male cicadas are among the loudest of all insects. E Damselfly, one of the insects that has aquatic larvae. F Termites. These sterile soldiers can shoot a gluelike substance from their head to protect their colony. G Grasshopper. Members of the four most diverse insect orders. All are winged and undergo complete metamorphosis: H A fly, dusted with pollen. I Ladybird beetles with a distinctive red and black spotted wing cover. J Staghorn beetle from New Guinea. K Bald-faced hornet, a type of wasp. This is a fertile female, or queen. She lives in a papery nest with her many offspring. L Swallowtail butterfly, a lovely lepidopteran, shown acting as pollinator. Fig. 23.32c, p. 371

Insect Diversity Figure 23.32 A sampling of insect diversity. A Silverfish, an ancient lineage that does not undergo metamorphosis. Insects that undergo incomplete metamorphosis: B European earwig, a common household pest. C Duck louse. It eats bits of feathers and skin. D Cicada. Male cicadas are among the loudest of all insects. E Damselfly, one of the insects that has aquatic larvae. F Termites. These sterile soldiers can shoot a gluelike substance from their head to protect their colony. G Grasshopper. Members of the four most diverse insect orders. All are winged and undergo complete metamorphosis: H A fly, dusted with pollen. I Ladybird beetles with a distinctive red and black spotted wing cover. J Staghorn beetle from New Guinea. K Bald-faced hornet, a type of wasp. This is a fertile female, or queen. She lives in a papery nest with her many offspring. L Swallowtail butterfly, a lovely lepidopteran, shown acting as pollinator. Fig. 23.32d, p. 371

Insect Diversity Figure 23.32 A sampling of insect diversity. A Silverfish, an ancient lineage that does not undergo metamorphosis. Insects that undergo incomplete metamorphosis: B European earwig, a common household pest. C Duck louse. It eats bits of feathers and skin. D Cicada. Male cicadas are among the loudest of all insects. E Damselfly, one of the insects that has aquatic larvae. F Termites. These sterile soldiers can shoot a gluelike substance from their head to protect their colony. G Grasshopper. Members of the four most diverse insect orders. All are winged and undergo complete metamorphosis: H A fly, dusted with pollen. I Ladybird beetles with a distinctive red and black spotted wing cover. J Staghorn beetle from New Guinea. K Bald-faced hornet, a type of wasp. This is a fertile female, or queen. She lives in a papery nest with her many offspring. L Swallowtail butterfly, a lovely lepidopteran, shown acting as pollinator. Fig. 23.32e, p. 371

Insect Diversity Figure 23.32 A sampling of insect diversity. A Silverfish, an ancient lineage that does not undergo metamorphosis. Insects that undergo incomplete metamorphosis: B European earwig, a common household pest. C Duck louse. It eats bits of feathers and skin. D Cicada. Male cicadas are among the loudest of all insects. E Damselfly, one of the insects that has aquatic larvae. F Termites. These sterile soldiers can shoot a gluelike substance from their head to protect their colony. G Grasshopper. Members of the four most diverse insect orders. All are winged and undergo complete metamorphosis: H A fly, dusted with pollen. I Ladybird beetles with a distinctive red and black spotted wing cover. J Staghorn beetle from New Guinea. K Bald-faced hornet, a type of wasp. This is a fertile female, or queen. She lives in a papery nest with her many offspring. L Swallowtail butterfly, a lovely lepidopteran, shown acting as pollinator. Fig. 23.32f, p. 371

Insect Diversity Figure 23.32 A sampling of insect diversity. A Silverfish, an ancient lineage that does not undergo metamorphosis. Insects that undergo incomplete metamorphosis: B European earwig, a common household pest. C Duck louse. It eats bits of feathers and skin. D Cicada. Male cicadas are among the loudest of all insects. E Damselfly, one of the insects that has aquatic larvae. F Termites. These sterile soldiers can shoot a gluelike substance from their head to protect their colony. G Grasshopper. Members of the four most diverse insect orders. All are winged and undergo complete metamorphosis: H A fly, dusted with pollen. I Ladybird beetles with a distinctive red and black spotted wing cover. J Staghorn beetle from New Guinea. K Bald-faced hornet, a type of wasp. This is a fertile female, or queen. She lives in a papery nest with her many offspring. L Swallowtail butterfly, a lovely lepidopteran, shown acting as pollinator. Fig. 23.32g, p. 371

Insect Diversity Figure 23.32 A sampling of insect diversity. A Silverfish, an ancient lineage that does not undergo metamorphosis. Insects that undergo incomplete metamorphosis: B European earwig, a common household pest. C Duck louse. It eats bits of feathers and skin. D Cicada. Male cicadas are among the loudest of all insects. E Damselfly, one of the insects that has aquatic larvae. F Termites. These sterile soldiers can shoot a gluelike substance from their head to protect their colony. G Grasshopper. Members of the four most diverse insect orders. All are winged and undergo complete metamorphosis: H A fly, dusted with pollen. I Ladybird beetles with a distinctive red and black spotted wing cover. J Staghorn beetle from New Guinea. K Bald-faced hornet, a type of wasp. This is a fertile female, or queen. She lives in a papery nest with her many offspring. L Swallowtail butterfly, a lovely lepidopteran, shown acting as pollinator. Fig. 23.32h, p. 371

Insect Diversity Figure 23.32 A sampling of insect diversity. A Silverfish, an ancient lineage that does not undergo metamorphosis. Insects that undergo incomplete metamorphosis: B European earwig, a common household pest. C Duck louse. It eats bits of feathers and skin. D Cicada. Male cicadas are among the loudest of all insects. E Damselfly, one of the insects that has aquatic larvae. F Termites. These sterile soldiers can shoot a gluelike substance from their head to protect their colony. G Grasshopper. Members of the four most diverse insect orders. All are winged and undergo complete metamorphosis: H A fly, dusted with pollen. I Ladybird beetles with a distinctive red and black spotted wing cover. J Staghorn beetle from New Guinea. K Bald-faced hornet, a type of wasp. This is a fertile female, or queen. She lives in a papery nest with her many offspring. L Swallowtail butterfly, a lovely lepidopteran, shown acting as pollinator. Fig. 23.32i, p. 371

Insect Diversity Figure 23.32 A sampling of insect diversity. A Silverfish, an ancient lineage that does not undergo metamorphosis. Insects that undergo incomplete metamorphosis: B European earwig, a common household pest. C Duck louse. It eats bits of feathers and skin. D Cicada. Male cicadas are among the loudest of all insects. E Damselfly, one of the insects that has aquatic larvae. F Termites. These sterile soldiers can shoot a gluelike substance from their head to protect their colony. G Grasshopper. Members of the four most diverse insect orders. All are winged and undergo complete metamorphosis: H A fly, dusted with pollen. I Ladybird beetles with a distinctive red and black spotted wing cover. J Staghorn beetle from New Guinea. K Bald-faced hornet, a type of wasp. This is a fertile female, or queen. She lives in a papery nest with her many offspring. L Swallowtail butterfly, a lovely lepidopteran, shown acting as pollinator. Fig. 23.32j, p. 371

Insect Diversity Figure 23.32 A sampling of insect diversity. A Silverfish, an ancient lineage that does not undergo metamorphosis. Insects that undergo incomplete metamorphosis: B European earwig, a common household pest. C Duck louse. It eats bits of feathers and skin. D Cicada. Male cicadas are among the loudest of all insects. E Damselfly, one of the insects that has aquatic larvae. F Termites. These sterile soldiers can shoot a gluelike substance from their head to protect their colony. G Grasshopper. Members of the four most diverse insect orders. All are winged and undergo complete metamorphosis: H A fly, dusted with pollen. I Ladybird beetles with a distinctive red and black spotted wing cover. J Staghorn beetle from New Guinea. K Bald-faced hornet, a type of wasp. This is a fertile female, or queen. She lives in a papery nest with her many offspring. L Swallowtail butterfly, a lovely lepidopteran, shown acting as pollinator. Fig. 23.32k, p. 371

Insect Diversity Figure 23.32 A sampling of insect diversity. A Silverfish, an ancient lineage that does not undergo metamorphosis. Insects that undergo incomplete metamorphosis: B European earwig, a common household pest. C Duck louse. It eats bits of feathers and skin. D Cicada. Male cicadas are among the loudest of all insects. E Damselfly, one of the insects that has aquatic larvae. F Termites. These sterile soldiers can shoot a gluelike substance from their head to protect their colony. G Grasshopper. Members of the four most diverse insect orders. All are winged and undergo complete metamorphosis: H A fly, dusted with pollen. I Ladybird beetles with a distinctive red and black spotted wing cover. J Staghorn beetle from New Guinea. K Bald-faced hornet, a type of wasp. This is a fertile female, or queen. She lives in a papery nest with her many offspring. L Swallowtail butterfly, a lovely lepidopteran, shown acting as pollinator. Fig. 23.32l, p. 371

ANIMATION: Insect Development To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

23.14 The Importance of Insects It would be hard to overestimate the importance of insects, for either good or ill Some perform ecological services as decomposers and pollinators; others harm crops and transmit diseases

Ecological Services Most flowering plants are pollinated by members of the four most successful insect groups Insects serve as food for a variety of wildlife (birds, fish, amphibians, reptiles, and even humans) Insects dispose of wastes (feces) and remains (animal corpses)

Cleanup Crew A dung beetle gathers a ball of dung (feces) The beetle will lay its eggs in the dung and the larval beetles will feed on it as they grow Figure 23.33 Cleanup crew. A dung beetle gathers a ball of dung (feces). The beetle will lay its eggs in the dung and the larval beetles will feed on it as they grow.

Competitors for Crops Insects devour 1/4 to 1/3 of all crops grown in the United States Mediterranean fruit fly (Med fly) lays eggs in fruits and vegetables Figure 23.34 Mediterranean fruit fly (Med fly), a major threat to fruit crops.

Vectors for Disease Mosquito-borne diseases such as malaria kill more than 1 million people each year Other disease vectors include flies, fleas, ticks and lice The deadliest animal Figure 23.35 The deadliest animal. When it comes to bites, no animal is more dangerous than the mosquito. Mosquito-borne diseases kill more than 1 million people each year.

Key Concepts The Most Successful Animals In terms of diversity, arthropods are the most successful animals Crustaceans abound in the seas and insects are the most diverse animal group on land Insects play essential roles in ecosystems They also have economic and health effects

23.15 Echinoderms Echinoderms belong to the deuterostome lineage – adults are radial, but larvae are bilateral, implying bilateral ancestry echinoderms Invertebrates with a water–vascular system Spines and other hard parts embedded in the skin support the body Includes sea stars, sea urchins, sea cucumbers, brittle stars, and sand dollars

Echinoderms Figure 23.36 Echinoderms. A,B Sea star. C Sea urchin. D Sea cucumber. Other members of this group include brittle stars and sand dollars.

Sea Star Characteristics Sea stars have no central nervous system; eyespots at the tips of the arms detect light and movement Sea stars usually prey on bivalve mollusks; using a water-vascular system with tube feet water–vascular system Of echinoderms, a system of fluid-filled tubes and tube feet that function in locomotion

Sea Star Body Plan

ossicle (tiny skeletal structure) Sea Star Body Plan upper stomach gonad spine anus lower stomach coelom digestive gland eyespot Figure 23.36 Echinoderms. A,B Sea star. C Sea urchin. D Sea cucumber. Other members of this group include brittle stars and sand dollars. spine ossicle (tiny skeletal structure) ampullae tube feet Fig. 23.36b, p. 373

Key Concepts On the Road to Chordates Echinoderms are on the same branch of the animal family tree as the vertebrates (animals that have a backbone) Echinoderm adults have a spiny skin and a radially symmetrical body The larvae show bilateral symmetry, indicating descent from a bilateral ancestor

Old Genes, New Drugs (revisited) Marine invertebrates are a treasure trove of molecules with potential in industrial applications or as medicines Cone snails, sponges, corals, crabs, and sea cucumbers all make compounds that show promise as drugs However, species are disappearing as a result of habitat destruction and overharvesting