Arthropods and Echinoderms

Arthropods and Echinoderms Ms. Moore 11/2/12

Introduction to the Arthropods • Phylum: Arthropoda • What is an Arthropod? • Arthropods have a segmented body, a tough exoskeleton, and jointed appendages • Exoskeleton: tough external covering; like a suit of armor that supports and protects the body • Chitin: carbohydrate that makes up exoskeleton • Appendages: structures that extend from the body wall • Antennae or legs

Evolution of Arthropods 1st arthropods appeared in the sea more than 600 m.y.a. Natural selectionfewer body segments and highly specialized appendages for feeding, movement, etc. At least 75,000 species have been identified

Form and Function in Arthropods • Feeding • Include herbivores, carnivores, omnivores, bloodsuckers, filter feeders, scavengers, and parasites. • Mouth parts range depending on diet

Respiration of Terrestrial Arthropods • Tracheal tubes: network of tubes that extend throughout the body • Spiracles: small openings along the side of the body attached to tracheal tubes • Book lungs: organs that have layers of respiratory tissue stacked like the pages of a book • Respiration of Aquatic Arthropods • Featherlike gills

Circulation • Open circulatory system • Excretion • Malpighian tubules: saclike organs that extract wastes from blood and add to feces • Diffusion occurs in aquatic arthropods. • Response • Well developed nervous system, brain, ventral nerve cord, and sense organs (compound eyes).

Movement • Use well-developed groups of muscles that are coordinated and controlled by nervous system • Flex or extend muscles • Reproduction • Terrestrial: internal fertilization; males have reproductive organ or sperm packet • Aquatic: internal or external fertilization

Growth and Development in Arthropods Exoskeleton does not grow with the animal. When they outgrow their exoskeletons, arthropods undergo periods of molting Molting: arthropod sheds its entire exoskeleton and manufactures a larger one to take its place; controlled by the endocrine system (hormones)

Groups of Arthropods • Arthropods are classified based on the number and structure of their body segments and appendages—particularly their mouthparts. • 3 Groups: • Crustaceans • Spiders and relatives • Insects and relatives

Crustaceans Subphylum: Crustacea Primarily aquatic Crustaceans typically have two pairs of antennae, two or three body sections, and chewing mouthparts called mandibles.

Crustacean Body Plan Cephalothorax: formed by fusion of the head with thorax Thorax: lies just behind the head and houses internal organs Abdomen: posterior part of the body Carapace: part of exoskeleton that covers cephalothorax

Mandible: mouthpart adapted for biting and grinding food Gills are attached to appendages associated with cephalothorax Decapods have five pairs of legs. Chelipeds: first pair of legs; bear large claws Swimmerets: flipper like appendages used for swimming Final abdominal segment is fused = tail.

P. 721 drawing

Other examples • Crustaceans include: • Crabs • Shrimps • Lobsters • Crayfishes • Barnacles (sessile) How are these alike and different?

Spiders and relatives Subphylum: Chelicerata Chelicerates have mouthparts called chelicerae and two body sections, nearly all have four pair of walking legs. Lack antennae found on most arthropods. Cephalothorax: brain, eyes, mouth, legs Abdomen: internal organs

Chelicerates have two pairs of appendages attached near the mouth • Chelicerae: contain fangs used to stab and paralyze prey • Pedipalps: longer than chelicerae, modified to grab prey • Use book gills or book lungs • 2 classes: • Merostomata: horseshoe crabs • Arachnida: spiders, mites, ticks, scorpions

Horseshoe Crabs • among oldest living arthropods, appeared more than 500 m.y.a. • Heavily armored like crabs, but have anatomy closer to spiders • Spiders • Largest group of arachnids • No jaws—must liquefy food to swallow • Chelicerae inject venom paralyze prey inject digestive enzymes stomach breaks down • Spinnerets: organs that contain silk glands • P722 drawing

Mites and Ticks • Small arachnids • Often parasitic • Chelicerae and pedipalps specialized for digging into host’s tissues and sucking out blood/plant fluids • Cephalothorax may stay in skin if pulled out • Scorpions • Pedipalps enlarged into claws • Abdomen carries a venomous stinger that can kill or paralyze prey • Unlike spiders, scorpions chew prey using chelicerae

Insects and relatives • Subphylum: Uniramia • Uniramians have jaws, one pair of antennae, and unbranched appendages. • Centipedes: • Class: Chilopoida • Segmented; each segment = one pair of legs, up to 100 pairs • Carnivores: mouthparts with venomous claws • Millipedes: • Class: Diplopoda • Highly segmented; each segment = 2 pairs of legs • Feed on dead and decaying plant material • Timid and roll into ball for protection

Insects • What is an Insect? • Insects have a body divided into 3 parts—head, thorax, and abdomen. 3 pairs of legs are attached to thorax. • Typical insect also has: pair of antennae, pair of compound eyes, two pairs of wings on thorax, and tracheal tubes. • The class, Insecta, contains more species than any other groups of animals.

Greatest Impact on the World?

Responses to Stimuli Use sense organs to detect external stimuli Compound eyes: made of many lenses that detect changes in color and movement Chemical receptors for taste on mouth, legs, and antennae Sensory hairs on legs Ears can be found in odd places (behind legs)

Feeding Adaptations • Insects have 3 pair of appendages used as mouthparts: • Mandibles used to saw and grind food (ant) • Tubelike mouthpart use to suck nectar (moth) • Spongelike mouthpart used to lap up food (fly) • Some produce saliva containing digestive enzymes to help break down food (nectarhoney)

Movement and Flight 3 pairs of legs can be used for walking, jumping, or capturing and holding prey. Flight—two pairs of wings made of chitin (also makes up exoskeleton) Colonize a wide variety of habitats.

Growth and Development:Metamorphosis • Metamorphosis: process of changing shape and form • Incomplete Metamorphosis: immature forms that undergo gradual change, look very much like adults • Nymphs: immature forms; lack functional sex organs and other features like wings; molt several times and grow to acquire adult structures • Complete Metamorphosis: hatch into larvae that look and act nothing like parents; also feed completely different • Pupa: stage in which an insect changes from larva to adult; body completely remodeled inside and out • P729 stages and 3 examples of insects in each

Insects and Humans • Negative effects • Termites destroy wood structures • Moths eat clothing and carpets • Bees and wasps produce painful stings • Positive effects • Pollination: 1/3 food we eat is pollinated by insects • Products: silk, wax, honey

Insect Communication • Visual Cues • Fireflies: light producing organ produces series of flashes • Chemical Signals • Pheromones: specific chemical messengers that affect behavior or development of other individuals • Fx: to signal alarm or alert; mating

Insect Societies • Society: group of closely related animals of the same species that work together for the benefit of the whole group (more than 7 million individuals) • Castes: specialized individuals/body form to perform particular tasks • Reproductive females that lay eggs called queens • Reproductive males • Workers

Communication in Societies • Each species has its own “language” of visual, touch, sound, and chemical signals • Bees use a form of dance for communication • Round dance: food is nearby to hive • Waggle dance: food is farther away from hive • Also shows direction of food…

What have we learned? Recap Give an example of 5 different insects and a specialized function/body part of each.

Arthropods and Echinoderms