Marine Invertebrates• Overview: Life Without a Backbone• Invertebrates – Are animals that lack a backbone – Account for 95% of known animal species
Porifera Cnidariachoanoflagellate Other bilaterians (includingAncestral colonial Nematoda, Arthropoda, Mollusca, and Annelida) Eumetazoa • A review of animal phylogeny Echinodermata Bilateria Chordata Deuterostomia
• Exploring invertebrate diversity PORIFERA (5,500 species) CNIDARIA (10,000 species) A sponge A jelly PLACOZOA (1 species) KINORHYNCHA (150 species) 0.5 mm 250 µm A placozoan (LM) A kinorhynch (LM) PLATYHELMINTHES (20,000 species) ROTIFERA (1,800 species) A marine flatworm A rotifer (LM) ECTOPROCTA (4,500 species) PHORONIDA (20 species) Ectoprocts Phoronids
• Exploring invertebrate diversity BRACHIOPODA (335 species) NEMERTEA (900 species) A brachiopod A ribbon worm ACANTHOCEPHALA (1,100 species) CTENOPHORA (100 species) 5 mm An acanthocephalan A ctenophore, or comb jelly MOLLUSCA (93,000 species) ANNELIDA (16,500 species) An octopus A marine annelid LORICIFERA (10 species) PRIAPULA (16 species) 50 µm A loriciferan (LM) A priapulan
• Exploring invertebrate diversity NEMATODA (25,000 species) ARTHROPODA (1,000,000 + species) A roundworm A scorpion (an arachnid) CYCLIOPHORA (1 species) TARDIGRADA (800 species) 100 µm 100 µm A cycliophoran (colorized SEM) Tardigrades (colorized SEM) ONYCHOPHORA (110 species) HEMICHORDATA (85 species) An onychophoran An acorn worm ECHINODERMATA (7,000 species) CHORDATA (52,000 species) A sea urchin A tunicate
• Sponges are sessile and have a porous body and choanocytes• Sponges, phylum Porifera – Live in both fresh and marine waters – Lack true tissues and organs• Phylum- Poriferia “pore bearers”• Aggregation of specialized cells• Cells are independent from each other & do not form true tissues & organs• Simplest multicellular animals
• Nearly all are marine• Sessile• Variety of color, shape, and sizes• Ostia (tiny pores) allow water to enter and circulate through series of canals where plankton and organic particles are filtered & eaten• Flexible skeletal frame gives the spongy texture• If cells separated can even regroup and form new sponge• Outer surface covered with flat cells called pinacocytes & pore cells (porocytes) which allows water to enter• Water pumped into larger feeding chamber lined with collar cells (choanocytes)• Each choanocytes has flagellum the creates currents and a thin collar that traps food particles, which is ingested by body of cell
• Water leaves through osculum, large opening at top of sponge• Type of suspension feeders that actively filter food particles (filter feeders)• Marine sponges show more complex arrangement with collar cells are restricted to chambers connected to outer pores by a network of channels• Marine sponges have single osculum but have several oscula which serves as exit from many canals
• Helps meet higher demands for water flow for larger sponges• Large sponges have spicules that are transparent made of siliceous or calcareous supporting structures of different shapes and sizes• Skeleton made of protein spongin• Some may spicules, spongin, or both• Wandering cells, amebocytes, secret spicules and sponging, transport and store food particles, and transform into other types if cells to quickly repair damage to the sponge
• Reproduce asexually• If piece breaks off, it can form new sponge• Reproduce sexually• Specialized collar cells or amebocytes can turn into gametes• Large nutrient rich egg and smaller sperm cell with flagellum• Most are hermaphrodites• Some have separate male and female organisms• Typically broadcast spawning• Egg retained inside of body until fertilization• Early development takes place inside• Flagellated sphere of cells (larva) is called parenchymula larva is planktonic & drifts with currents• Settles & metamorphosis into juvenile
• Sponges are suspension feeders – Capturing food particles suspended in the water that passes through their body 5 Choanocytes. The spongocoel is lined with feeding cells called choanocytes. By beating flagella, Flagellum the choanocytes create a current that Food particles Choanocyte draws water in through the porocytes. Collar in mucus Azure vase sponge (Callyspongia Osculum plicifera) 4 Spongocoel. Water passing through porocytes enters a cavity called the Phagocytosis of spongocoel. food particles Amoebocyte 3 Porocytes. Water enters the epidermis through 6 The movement of the choanocyte channels formed by flagella also draws water through its porocytes, doughnut-shaped Spicules collar of fingerlike projections. Food cells that span the body wall. particles are trapped in the mucus coating the projections, engulfed by 2 Epidermis. The outer phagocytosis, and either digested or layer consists of tightly transferred to amoebocytes. packed epidermal cells. Water flow 7 Amoebocyte. Amoebocytes 1 Mesohyl. The wall of this transport nutrients to other cells of simple sponge consists of the sponge body and also produce two layers of cells separated materials for skeletal fibers (spicules). by a gelatinous matrix, the mesohyl (“middle matter”).
Cnidaria/Coelenterata• Cnidarians have radial symmetry, a gastrovascular cavity, and cnidocytes• All animals except sponges – Belong to the clade Eumetazoa, the animals with true tissues• Phylum Cnidaria – Is one of the oldest groups in this clade
• Next evolutionary jump• Have tissues that perform specific functions• Sometimes called coelenterates include sea anemones, jellyfishes, and• corals• Radial symmetry• If cut like pizza all resulting slices would be similar• Look the same from all sides• No head, front, or back• Oral surface and aboral surface• Central mouth with tentacles• Mouth open into a gut (only one opening)
• Capture prey with nematocycts (stinging structures) found within tentacles• Two basic forms: Polyp and medusa• Some life history includes both others are either polyp or medusa• Larva is called planula, ciliated stage with two cell layers• Settles and metamorphoses into a polyp or develops into medusa• Two layer of cells form body wall-one the epidermis and other gastrodermis• Gelatinous middle layer is mesoglea- does not contain cells• In medusae this layer expands to form gelatinous domed bell
• There are two variations on this body plan – The sessile polyp and the floating medusa Polyp Mouth/anus Medusa Tentacle Gastrovascular cavity Gastrodermis Mesoglea Epidermis Body stalk Tentacle Mouth/anus
• Cnidarians are carnivores – That use tentacles to capture prey• The tentacles are armed with cnidocytes – Unique cells that function in defense and the capture of prey Prey Tentacle “Trigger” Discharge Of thread Nematocyst Coiled thread Cnidocyte
• The phylum Cnidaria is divided into four major classes
– Hydrozoa, Scyphozoa, Cubozoa, and Anthozoa (b) Many species of jellies (class (c) The sea wasp (Chironex (d) Sea anemones and other Scyphozoa), including the fleckeri) is a member of members of class Anthozoa species pictured here, are class Cubozoa. Its poison, exist only as polyps. bioluminescent. The largest which can subdue fish and scyphozoans have tentacles other large prey, is more more than 100 m long potent than cobra venom. dangling from a bell-shaped body up to 2 m in diameter.(a) These colonial polyps are members of class Hydrozoa.
Hydrozoans• Most hydrozoans – Alternate between polyp and medusa forms 3Other polyps, specialized 2 Some of the colony’s for reproduction, lack 4The medusae polyps, equipped with tentacles, tentacles and produce tiny swim off, grow, and are specialized for feeding. medusae by asexual budding. reproduce sexually. Reproductive polyp Feeding 1 A colony of polyp interconnected polyps (inset, Medusa LM) results MEIOSIS bud from asexual Gonad Medusa reproduction by budding. SEXUAL Egg Sperm REPRODUCTION ASEXUAL REPRODUCTION Portion of (BUDDING) a colony of polyps FERTILIZATION Zygote Developing polyp Mature polyp Planula (larva) Key Haploid (n) 1 mm 6The planula eventually settles 5 The zygote develops into a Diploid (2n) and develops into a new polyp. solid ciliated larva called a planula.
Hydrozoans (class Hydrozoa)• Feathery or bushy colonies of tiny polyps attached to pilings, shells, seaweeds, and other surfaces• Polyps may be specialized for feeding, defense, or reproduction• Reproductive polyps produce minute, plantonic medusae• Medusae release gametes & fertilized eggs develop into free swimming planula larvae• Each planula larvae settles and develops into a polyp• The poylp divides repeatedly and develops into a colony• Some lack poylp stage and develop into a medusae• Few lack medusae stage and develop into gamete producing polyps
Scyphozoans• In the class Scyphozoa – Jellies (medusae) are the prevalent form of the life cycle
Scyphozoans (class Scyphozoa)• Larger jellyfish• Large medusae are dominate stage in life cycle• Polyps small & release juvenile medusae• Few lack polyp stage• Bell reach diameter of 2 m (6.6 ft)• Bell diameter in deep water is 3 m (10 ft)• Swim with rhythmic contractions of bell but easily carried by currents• Some species stings range from a rash to fatalities• Cubomedusae once classified as scyphozoa now own class Cubozoa• Sea wasp (box jelly)
Cubozoans• In the class Cubozoa, which includes box jellies and sea wasps – The medusa is box-shaped and has complex eyes
Anthozoans• Class Anthozoa includes the corals and sea anemones – Which occur only as polyps
Anthozoans (class Anthozoa)• Solitary or colonial polyps that lack medusae stage• Largest number of species• Polyps more complex• Gut contain septa increasing surface area for digestion of large prey• Septa provide support for larger species• Sea anemones have large polyps
• Most animals have bilateral symmetry• The vast majority of animal species belong to the clade Bilateria – Which consists of animals with bilateral symmetry and triploblastic development
Feeding and digestion• Carnivores• Use nematocysts to capture prey• Each nematocyst contains fluid-filled capsule containing thread that is ejected• Thread my be spines or long tube that wrap around prey• Toxic• Extracellular digestion-out side the cells• Intracellular digestion within cells lining gut
Behavior• Lack brain & true nerves• Nerve cells interconnect forming nerve net that transmits impulses in all directions• Sea anemones can tell if other member is from same clone• Known to attack even kill anemones from other clones• Some medusae have primitive eyes• Medusae have statocysts to help with balance
Comb Jellies: Radial Symmetry Revisited• Comb jellies, ctenophores (phylum Ctenophora)• All marine about 100 species• Gelatinous body with 8 rows of ciliary combs that beat in waves• Beating of combs refracts light creating multicolor effect• Body length few millimeters to 2 m• Found in warm and cold waters• Carnivores• Swarms consume large numbers of fish larvae and other plankton• Capture prey with long tentacles with colloblasts (sticky cells)• Few have nematocysts
Flatworms• Members of phylum Platyhelminthes – Live in marine, freshwater, and damp terrestrial habitats – Are flattened dorsoventrally and have a gastrovascular cavity• Although flatworms undergo triploblastic development – They are acoelomates
• Simplest flatworms• Have central nervous system• Simple brain- aggregation of nerve cells• Have several nerve cord running from brain through the length of body• Nervous system coordinates movement of well-developed muscular system• Gut has one opening
• Have middle layer of tissues, in developing embryos it is called mesoderm• Mesoderm gives rise to muscles, reproductive system and other organs• 20,000 known species• Turbellarians most common have striking color patters• Live in or on oysters, crabs, & other invertebrates
• Turbellarians Turbellarian – Are nearly all free-living and mostly marine
Monogeneans and Trematode• Monogeneans and trematodes – Live as parasites in or on other animals – Parasitize a wide range of hosts• Flukes (trematodes)• Largest group 6,000 species• All parasites• Feed on tissues, blood, or intestinal contents• Adult flukes live in vertebrates
• Larvae may inhabit like snails and clams or vertebrates like fish• Larva must be eaten by a vertebrate• Common in fish, seabirds, and whales• Most monogeneans – Are parasites of fish
• Tapeworms Tapeworm – Are also parasitic and lack a digestive system Proglottids with reproductive structures 200 µm Scolex Hooks Sucker
Tapeworms (cestodes)• Parasitic• Have long body with repeating units• Live in intestine of most species of vertebrates• Head attaches to walls of gut by suckers and hooks• Lack gut or mouth• Absorb nutrients from host across body wall• Found in invertebrates and vertebrates• Longest recorded in sperm whale was 50 ft
Ribbon Worms (phylum Nemertea)• Ribbon or nemertean worms• More complex than flatworms• Complete digestive tract (mouth, gut, anus)• Have circulatory system• Proboscis-long flesh tube to capture prey• Inverted in cavity above mouth
Nemerteans• Members of phylum Nemertea – Are commonly called proboscis worms or ribbon worms
• Feed of worms and crustaceans• 900 species mostly marine• Found in all oceans most common in shallow temperate waters• Some nocturnal, some brightly colored found under rocks at low tides• Elastic, and proboscis may extend to a meter or more beyond body length• Longest invertebrate reaches 100 ft
• The nemerteans unique proboscis – Is used for defense and prey capture – Is extended by a fluid-filled sac• Nemerteans also have a closed circulatory system – In which the blood is contained in vessels distinct from fluid in the body cavity
• Molluscs have a muscular foot, a visceral mass, and a mantle• Phylum Mollusca – Includes snails and slugs, oysters and clams, and octopuses and squids• Most molluscs are marine – Though some inhabit fresh water and some are terrestrial• Molluscs are soft-bodied animals – But most are protected by a hard shell
• All molluscs have a similar body plan with three main parts – A muscular foot – A visceral mass – A mantle
Heart. Most molluscs have an open circulatory system. The dorsally located heart pumps Nephridium. Excretory organs circulatory fluid called hemolymph through arteries called nephridia remove metabolic into sinuses (body spaces). The organs of the wastes from the hemolymph. mollusc are thus continually bathed in hemolymph. Visceral mass The long digestive tract is coiled in the visceral mass. Coelom Intestine Gonads Mantle Stomach Radula. The mouth Mantle region in many Shell cavity Mouth mollusc species Radula Anus contains a rasp-like feeding organ The nervous Gill called a radula. This system consists belt of backward- of a nerve ring curved teeth slides around the back and forth,esophagus, from Foot Nerve Mouth cords Esophagus scraping and which nerve scooping like a cords extend. backhoe.
• Most molluscs have separate sexes – With gonads located in the visceral mass• The life cycle of many molluscs – Includes a ciliated larval stage called a trochophore
Chitons• Class Polyplacophora is composed of the chitons – Oval-shaped marine animals encased in an armor of eight dorsal plates
Gastropods• About three-quarters of all living species of molluscs – Belong to class Gastropoda (a) A land snail (b) A sea slug. Nudibranchs, or sea slugs, lost their shell during their evolution.
• Most gastropods – Are marine, but there are also many freshwater and terrestrial species – Possess a single, spiraled shell• Slugs lack a shell – Or have a reduced shell
• The most distinctive characteristic of this class – Is a developmental process known as torsion, which causes the animal’s anus and mantle to end up above its head Stomach Mantle Intestine cavity Anus Mouth
Bivalves• Molluscs of class Bivalvia – Include many species of clams, oysters, mussels, and scallops – Have a shell divided into two halves
• The mantle cavity of a bivalve – Contains gills that are used for feeding as well as gas exchange Hinge area Coelom Mantle Gut Heart Shell Adductor muscle Mouth Anus Excurrent siphon Palp Water Foot flow Mantle Incurrent cavity Gill siphon
Cephalopods• Class Cephalopoda includes squids and octopuses – Carnivores with beak-like jaws surrounded by tentacles of their modified foot
• Most octopuses – Creep along the sea floor in search of prey (a) Octopuses are considered among the most intelligent invertebrates.
• Squids use their siphon – To fire a jet of water, which allows them to swim very quickly (b) Squids are speedy carnivores with beaklike jaws and well-developed eyes.
`• One small group of shelled cephalopods – The nautiluses, survives today (c) Chambered nautiluses are the only living cephalopods with an external shell.
• Annelids are segmented worms• Annelids – Have bodies composed of a series of fused rings• 20,000 species• Series of similar compartments• (segmented)• Gut through all segments and lies in cavity known as coelom• Coelom fluid filled & divided by partitions• Segments acts as hydrostatic skeleton contracting in sequence by muscles in body wall• Efficient crawlers & burrowers
• The phylum Annelida is divided into three classes
Polychaetes• Members of class Polychaeta – Possess paddlelike parapodia that function as gills and aid in locomotion Parapodia
Polychaetes (class Polychaeta)• Body segments of most have a pair of flattened extensions or parapodia• Parapoda have stiff sharp bristles (setae)• Have closed circulatory system• Muscular contractions help circulation of blood• Small organisms oxygen in water can easily move across body wall to all tissues• Large organisms have gills on parapodia• Gills thin wall extensions of body that have capillaries where gas exchange takes place
• Have plantonic larval stage-trochophore• Biologist compare larvae stage of polychaetes with other invertebrates to examine evolutionary relationships• Typical length is 5 to 10 cm• Many crawl hiding under rocks• Nereis (sandworms) carnivores• Have several pairs of eyes & other sensory organs• Use proboscis with jaws to capture prey• Others are deposit feeder• Many live in temporary or permanent tubes made from mucus, proteins, bits of seaweed, cemented mud particles, sand grains, or tiny fragments of shells
Oligochaetes• Oligochaetes (class Oligochaeta) – Are named for their relatively sparse chaetae, or bristles made of chitin – Include the earthworms and a variety of aquatic species
Leeches• Members of class Hirudinea – Are blood-sucking parasites, such as leeches
• Nematodes are nonsegmented pseudocoelomates covered by a tough cuticle• Among the most widespread of all animals, nematodes, or roundworms – Are found in most aquatic habitats, in the soil, in moist tissues of plants, and in the body fluids and tissues of animals• Round worms, hardly ever seen• Found in large numbers in rich organic sediments• Many are parasitic found in most marine organisms• Adapted to live in sediment or tissues of other organisms• Typically pointed at both ends• Feed mostly on bacteria and organic matter• Anus lies within body cavity filled with fluid that transports nutrients
• The cylindrical bodies of nematodes (phylum Nematoda) – Are covered by a tough coat called a cuticle 25 µm
• Concept 33.7: Arthropods are segmented coelomates that have an exoskeleton and jointed appendages• Two out of every three known species of animals are arthropods• Members of the phylum Arthropoda – Are found in nearly all habitats of the biosphere
• Layer of muscle in the tough but flexible body pushes and squeezes against the fluid which acts as hydrostatic skeleton that provides support and aids in locomotion• 10,000 to 25,000 species and estimates that half a million still undiscovered• Anisakis and few related inhabit seals and dolphins• Larvae found on flesh of many types of fish and may infect humans who eat raw or poorly cooked fish• Often larvae are vomited or coughed up without further complications• Sometimes penetrate into walls of stomach or intestine causing symptoms similar to ulcers• A risk all sashimi and cerviche lovers take
• General Characteristicsarthropods The diversity and success of of Arthropods – Are largely related to their segmentation, hard exoskeleton, and jointed appendages
• Early arthropods, such as trilobites – Showed little variation from segment to segment Figure 33.28
• As arthropods evolved – The segments fused, and the appendages became more specialized• The appendages of some living arthropods – Are modified for many different functions Cephalothorax Abdomen Antennae Head Thorax (sensory reception) Swimming appendages Walking legs Figure 33.29 Pincer (defense) Mouthparts (feeding)
• The body of an arthropod – Is completely covered by the cuticle, an exoskeleton made of chitin• When an arthropod grows – It molts its exoskeleton in a process called ecdysis
• Arthropods have an open circulatory system – In which fluid called hemolymph is circulated into the spaces surrounding the tissues and organs• A variety of organs specialized for gas exchange – Have evolved in arthropods
• Molecular evidence now suggests – That living arthropods consist of four major lineages that diverged early in the evolution of the phylum Table 33.5
Cheliceriforms• Cheliceriforms, subphylum Cheliceriformes – Are named for clawlike feeding appendages called chelicerae – Include spiders, ticks, mites, scorpions, and horseshoe crabs
• Most of the marine cheliceriforms are extinct – But some species survive today, including the horseshoe crabs Figure 33.30
• Most modern cheliceriforms are arachnids – A group that includes spiders, scorpions, ticks, and mites 50 µm(a) Scorpions have pedipalps that are pincers (b) Dust mites are ubiquitous scavengers in (c) Web-building spiders are generally specialized for defense and the capture of human dwellings but are harmless except most active during the daytime. food. The tip of the tail bears a poisonous to those people who are allergic to them stinger. (colorized SEM).Figure 33.31a–c
• Arachnids have an abdomen and a cephalothorax – Which has six pairs of appendages, the most anterior of which are the chelicerae Intestine Stomach Digestive Brain gland Heart Eyes Ovary Poison gland Anus Book lung Spinnerets Gonopore Sperm Pedipalp Chelicera Figure 33.32 Silk gland (exit for eggs) receptacle
Myriapods• Subphylum Myriapoda – Includes millipedes and centipedes
• Millipedes, class Diplopoda – Have a large number of legs• Each trunk segment – Has two pairs of legs Figure 33.33
• Centipedes, class Chilopoda – Are carnivores with jaw-like mandibles – Have one pair of legs per trunk segment Figure 33.34
Insects• Subphylum Hexapoda, insects and their relatives – Are more species-rich than all other forms of life combined – Live in almost every terrestrial habitat and in fresh water
• The internal anatomy of an insect – Includes several complex organ systems The insect body has three regions: head, thorax, and abdomen. The segmentation Cerebral ganglion. The two nerve of the thorax and abdomen are obvious, Heart. The cords meet in the head, where the but the segments that form the head are fused. insect heart ganglia of several anterior segments drives hemolymph are fused into a cerebral ganglion Abdomen Thorax Head through an (brain). The antennae, eyes, and Compound eye open circulatory other sense organs are concentrated system. on the head. Antennae Ovary Dorsal artery Crop Malpighian tubules. Anus Metabolic wastes are removed from the Vagina hemolymph by excretory organs called Malpighian tubules, which are out- pocketings of the digestive tract. Tracheal tubes. Gas exchange in insects is Nerve cords. The insect Insect mouthparts are formed from accomplished by a tracheal system of branched, nervous system several pairs of modified appendages. chitin-lined tubes that infiltrate the body and consists of a pair of The mouthparts include mandibles, carry oxygen directly to cells. The tracheal ventral nerve cords which grasshoppers use for chewing. system opens to the outside of the body with several In other insects, mouthparts are through spiracles, pores that can control air segmental ganglia. specialized for lapping, piercing, or Figure 33.35 flow and water loss by opening or closing. sucking.
• Flight is obviously 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
• Many insects – Undergo metamorphosis during their development• In incomplete metamorphosis, the young, called nymphs – Resemble adults but are smaller and go through a series of molts until they reach full size
• 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
• Metamorphosis from the larval stage to the adult stage – Occurs during a pupal stage (a) Larva (caterpillar) (b) Pupa (c) Pupa (d) Emerging adult Figure 33.6a–e (e) Adult
• Insects are classified into about 26 orders APPROXIMATE ORDER NUMBER OF MAIN CHARACTERISTICS EXAMPLES SPECIES Blattodea 4,000 Cockroaches have a dorsoventrally flattened body, with legs modified for rapid running. Forewings, when present, are leathery, whereas hind wings are fanlike. Fewer than 40 cock- German roach species live in houses; the rest exploit habitats ranging cockroach from tropical forest floors to caves and deserts. Coleoptera 350,000 Beetles comprise the most species-rich order of insects. They have two pairs of wings, one of which is thick and leathery, the Japanese other membranous. They have an armored exoskeleton and beetle mouthparts adapted for biting and chewing. Beetles undergo complete metamorphosis. Dermaptera 1,200 Earwigs are generally nocturnal scavengers. While some species are wingless, others have two pairs of wings, one of which is thick and leathery, the other membranous. Earwigs have biting mouthparts and large posterior pincers. They un- dergo incomplete metamorphosis. Earwig Diptera 151,000 Dipterans have one pair of wings; the second pair has become modified into balancing organs called halteres. Their head is large and mobile; their mouthparts are adapted for sucking, piercing, or lapping. Dipterans undergo complete metamorpho- Horsefly sis. Flies and mosquitoes are among the best-known dipterans, which live as scavengers, predators, and parasites. Hemiptera 85,000 Hemipterans are so-called “true bugs,” including bed bugs, assassin bugs, and chinch bugs. (Insects in other orders are Leaf- sometimes erroneously called bugs.) Hemipterans have two Footed pairs of wings, one pair partly leathery, the other membranous. bug They have piercing or sucking mouthparts and undergo incomplete metamorphosis. Hymenoptera 125,000 Ants, bees, and wasps are generally highly social insects. They have two pairs of membranous wings, a mobile head, and chewing or sucking mouthparts. The females of many species have a posterior stinging organ. Hymenopterans undergo com- plete metamorphosis. Cicada-killer wasp Isoptera 2,000 Termites are widespread social insects that produce enormous colonies. It has been estimated that there are 700 kg of termites for every person on Earth! Some termites have two pairs of membranous wings, while others are wingless. They feed on wood with the aid of microbial symbionts carried in specialized chambers in their hindgut. Termite Figure 33.37
• Insects are classified into about 26 orders APPROXIMATE ORDER NUMBER OF MAIN CHARACTERISTICS EXAMPLE SPECIES Lepidoptera 120,000 Butterflies and moths are among the best-known insects. They have two pairs of wings covered with tiny scales. To feed, they uncoil a long proboscis. Most feed on nectar, but some species feed on other substances, including animal blood or tears. Swallowtail butterfly 5,000 Dragonflies and damselflies have two pairs of large, membran- Odonata ous wings. They have an elongated abdomen, large, compound eyes, and chewing mouthparts. They undergo incomplete meta- morphosis and are active predators. Dragonfly Orthoptera 13,000 Grasshoppers, crickets, and their relatives are mostly herbi- vorous. They have large hind legs adapted for jumping, two pairs of wings (one leathery, one membranous), and biting or chewing mouthparts. Males commonly make courtship sounds by rubbing together body parts, such as a ridge on their hind leg. Orthopterans undergo incomplete metamorphosis. Katydid Phasmida 2,600 Stick insects and leaf insects are exquisite mimics of plants. The eggs of some species even mimic seeds of the plants on which the Insects live. Their body is cylindrical or flattened dorsoventrally. They lack forewings but have fanlike hind wings. Their Stick insect mouthparts are adapted for biting or chewing. Phthiraptera 2,400 Commonly called sucking lice, these insects spend their entire life as an ectoparasite feeding on the hair or feathers of a single Human host. Their legs, equipped with clawlike tarsi, are adapted for Body clinging to their hosts. They lack wings and have reduced eyes. louse Sucking lice undergo incomplete metamorphosis. Siphonaptera 2,400 Fleas are bloodsucking ectoparasites on birds and mammals. Their body is wingless and laterally compressed. Their legs are modified for clinging to their hosts and for long-distance jumping. They undergo complete metamorphosis. Flea Thysanura 450 Silverfish are small, wingless insects with a flattened body and reduced eyes. They live in leaf litter or under bark. They can also infest buildings, where they can become pests. Silverfish Trichoptera 7,100 The larvae of caddisflies live in streams, where they make houses from sand grains, wood fragments, or other material held to- gether by silk. Adults have two pairs of hairy wings and chewing or lapping mouthparts. They undergo complete metamorphosis. Caddisfly Figure 33.37
Crustaceans• While arachnids and insects thrive on land – Crustaceans, for the most part, have remained in marine and freshwater environments
• Crustaceans, subphylum Crustacea – Typically have biramous, branched, appendages that are extensively specialized for feeding and locomotion
• Decapods are all relatively large crustaceans – And include lobsters, crabs, crayfish, and shrimp (a) Ghost crabs (genus Ocypode) live on sandy ocean beaches worldwide. Primarily nocturnal, they take Figure 33.38a shelter in burrows during the day.
• Planktonic crustaceans include many species of copepods – Which are among the most numerous of all animals (b) Planktonic crustaceans known as krill are consumed in vast Figure 33.38b quantities by whales.
• Barnacles are a group of mostly sessile crustaceans – Whose cuticle is hardened into a shell (c) The jointed appendages projecting from the shells of these barnacles capture organisms and organic particles suspended in Figure 33.38c the water.
• Concept 33.8: Echinoderms and chordates are deuterostomes• At first glance, sea stars and other echinoderms, phylum Echinodermata – May seem to have little in common with phylum Chordata, which includes the vertebrates
• Chordates and echinoderms share characteristics of deuterostomes – Radial cleavage – Development of the coelom from the archenteron – Formation of the mouth at the end of the embryo opposite the blastopore
Echinoderms• Sea stars and most other echinoderms – Are slow-moving or sessile marine animals• A thin, bumpy or spiny skin – Covers an endoskeleton of hard calcareous plates
• Unique to echinoderms is a water vascular system – A network of hydraulic canals branching into tube feet that function in locomotion, feeding, and gas exchange A short digestive tract runs from the mouth on the bottom of the central disk to the anus on top of the disk. The surface of a sea star is Central disk. The central Spine covered by spines that help Stomach disk has a nerve ring and defend against predators, as Anus nerve cords radiating from well as by small gills that the ring into the arms. Gills provide gas exchange. Madreporite. Water can flow in or out of the water vascular Radial Digestive glands secrete system into the surrounding Gonads nerve digestive juices and aid in Ring water through the madreporite. the absorption and storage canal Ampulla of nutrients. Podium Tube feet Radial canal. The water vascular Branching from each radial canal are hundreds of hollow, muscular tube system consists of a ring canal in the feet filled with fluid. Each tube foot consists of a bulb-like ampulla and central disk and five radial canals, suckered podium (foot portion). When the ampulla squeezes, it forces each running in a groove down the water into the podium and makes it expand. The podium then entire length of an arm. contacts the substrate. When the muscles in the wall of the podium Figure 33.39 contract, they force water back into the ampulla, making the podium shorten and bend.
• The radial anatomy of many echinoderms – Evolved secondarily from the bilateral symmetry of ancestors
• Living echinoderms are divided into six classes Table 33.6
Sea Stars• Sea stars, class Asteroidea – Have multiple arms radiating from a central disk• The undersurfaces of the arms – Bear tube feet, each of which can act like a suction disk Figure 33.40a (a) A sea star (class Asteroidea)
Brittle Stars• Brittle stars have a distinct central disk – And long, flexible arms Figure 33.40b (b) A brittle star (class Ophiuroidea)
• SeaSea Urchins and Sand Dollars urchins and sand dollars have no arms – But they do have five rows of tube feet that function in movement Figure 33.40c (c) A sea urchin (class Echinoidea)
Sea• Sea lilies Lilies and Feather Stars – Live attached to the substrate by a stalk
• Feather starsSea Cucumbers – Crawl about using their long, flexible arms Figure 33.40d (d) A feather star (class Crinoidea)
Sea• Sea cucumbers Cucumbers – Upon first inspection do not look much like other echinoderms – Lack spines, and their endoskeleton is much reduced Figure 33.40e (e) A sea cucumber (class Holothuroidea)
Sea Daisies• Sea daisies were discovered in 1986 – And only two species are known Figure 33.40f (f) A sea daisy (class Concentricycloidea)
• Chordates Chordates – Phylum Chordata – Consists of two subphyla of invertebrates as well as the hagfishes and the vertebrates – Shares many features of embryonic development with echinoderms