LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson © 2011 Pearson Education, Inc. Lectures by Erin Barley Kathleen Fitzpatrick An Introduction to Invertebrates Chapter 33

Overview: Life Without a Backbone Invertebrates are animals that lack a backbone They account for 95% of known animal species They are morphologically diverse –For example, the Christmas tree worm (Spirobranchus giganteus) has tentacles for gas exchange and feeding © 2011 Pearson Education, Inc.

Figure 33.1

Figure 33.2 ANCESTRAL PROTIST Common ancestor of all animals Porifera Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia Eumetazoa Bilateria

Figure 33.3a Porifera (5,500 species) A sponge Cnidaria (10,000 species) A jelly Acoela (400 species) Acoel flatworms (LM) 1.5 mm Placozoa (1 species) 0.5 mm A placozoan (LM) Ctenophora (100 species) A ctenophore, or comb jelly

Figure 33.3aa A sponge

Figure 33.3ab A jelly

Figure 33.3ac Acoel flatworms (LM) 1.5 mm

Figure 33.3ad A placozoan (LM) 0.5 mm

Figure 33.3ae A ctenophore, or comb jelly

Platyhelminthes (20,000 species) A marine flatworm Acanthocephala (1,100 species) Curved hooks An acanthocephalan (LM) Mollusca (93,000 species) An octopus A ribbon worm A cycliophoran (colorized SEM) A marine annelid 100  m Lophotrochozoa Nemertea (900 species) Cycliophora (1 species) Ectoprocts A rotifer (LM) A brachiopod 0.1 mm Annelida (16,500 species) Ectoprocta (4,500 species) Rotifera (1,800 species) Brachiopoda (335 species) Figure 33.3b

Figure 33.3ba A marine flatworm

Figure 33.3bb Ectoprocts

Figure 33.3bc A rotifer (LM) 0.1 mm

Figure 33.3bd A brachiopod

Figure 33.3be Curved hooks An acanthocephalan (LM)

Figure 33.3bf A ribbon worm

Figure 33.3bg A cycliophoran (colorized SEM) 100  m

Figure 33.3bh A marine annelid

Figure 33.3bi An octopus

Loricifera (10 species) 50  m Ecdysozoa A loriciferan (LM) Priapula (16 species) Onychophora (110 species) A priapulan Nematoda (25,000 species) Tardigrada (800 species) Arthropoda (1,000,000 species) An onychophoran A roundworm (colored SEM) Tardigrades (colorized SEM) A scorpion (an arachnid) 100  m Figure 33.3c

Figure 33.3ca 50  m A loriciferan (LM)

Figure 33.3cb A priapulan

Figure 33.3cc An onychophoran

Figure 33.3cd A roundworm (colored SEM)

Figure 33.3ce Tardigrades (colorized SEM) 100  m

Figure 33.3cf A scorpion (an arachnid)

Hemichordata (85 species) Chordata (52,000 species) A tunicate Echinodermata (7,000 species) An acorn worm A sea urchin Deuterostomia Figure 33.3d

Figure 33.3da An acorn worm

Figure 33.3db A tunicate

Figure 33.3dc A sea urchin

Concept 33.1: Sponges are basal animals that lack true tissues Animals in the phylum Porifera are known informally as sponges They are sedentary and live in marine waters or fresh water © 2011 Pearson Education, Inc.

Figure 33.UN01 Porifera Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia

Sponges are suspension feeders, capturing food particles suspended in the water that passes through their body Water is drawn through pores into a cavity called the spongocoel and out through an opening called the osculum Sponges lack true tissues and organs © 2011 Pearson Education, Inc.

Azure vase sponge (Callyspongia plicifera) Spongocoel Pore Epidermis Water flow Mesohyl Osculum Choanocyte Flagellum Collar Food particles in mucus Choanocyte Amoebocyte Phagocytosis of food particles Spicules Amoebocytes Figure 33.4

Figure 33.4a Azure vase sponge (Callyspongia plicifera)

Figure 33.4b Spongocoel Pore Epidermis Water flow Mesohyl Osculum Choanocyte Spicules Amoebocytes

Figure 33.4c Flagellum Collar Food particles in mucus Choanocyte Amoebocyte Phagocytosis of food particles

Choanocytes, flagellated collar cells, generate a water current through the sponge and ingest suspended food Sponges consist of a gelatinous noncellular mesohyl layer between two cell layers Amoebocytes are found in the mesohyl and play roles in digestion and structure Most sponges are hermaphrodites: Each individual functions as both male and female © 2011 Pearson Education, Inc.

Concept 33.2: Cnidarians are an ancient phylum of eumetazoans All animals except sponges and a few other groups belong to the clade Eumetazoa, animals with true tissues Phylum Cnidaria is one of the oldest groups in this clade © 2011 Pearson Education, Inc.

Figure 33.UN02 Porifera Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia Eumetazoa

Cnidarians have diversified into a wide range of both sessile and motile forms including jellies, corals, and hydras They exhibit a relatively simple diploblastic, radial body plan The basic body plan of a cnidarian is a sac with a central digestive compartment, the gastrovascular cavity A single opening functions as mouth and anus © 2011 Pearson Education, Inc.

There are two variations on the body plan: the sessile polyp and motile medusa A polyp adheres to the substrate by the aboral end of its body A medusa has a bell-shaped body with its mouth on the underside Medusae do not attach to the substate but move freely © 2011 Pearson Education, Inc.

Figure 33.5 Mouth/anus Tentacle Gastrovascular cavity Gastrodermis Mesoglea Epidermis Tentacle Mouth/anus MedusaPolyp Body stalk

Cnidarians are carnivores that use tentacles to capture prey The tentacles are armed with cnidocytes, unique cells that function in defense and capture of prey Nematocysts are specialized organelles within cnidocytes that eject a stinging thread © 2011 Pearson Education, Inc.

Figure 33.6 Tentacle Cuticle of prey Nematocyst “Trigger” Thread (coiled) Cnidocyte Thread discharges Thread

Phylum Cnidaria is divided into four major classes –Hydrozoa –Scyphozoa –Cubozoa –Anthozoa © 2011 Pearson Education, Inc.

Figure 33.7 (a) Hydrozoa (b) Scyphozoa(c) Cubozoa(d) Anthozoa

Figure 33.7a (a) Hydrozoa

Figure 33.7b (b) Scyphozoa

Figure 33.7c (c) Cubozoa

Figure 33.7d (d) Anthozoa

Hydrozoans Most hydrozoans alternate between polyp and medusa forms Hydra, a freshwater cnidarian, exists only in polyp form and reproduces asexually by budding © 2011 Pearson Education, Inc.

Figure Feeding polyp Reproductive polyp Portion of a colony of polyps Medusa bud Medusa Gonad 1 mm Key Haploid (n) Diploid (2n)

Figure Feeding polyp Reproductive polyp Portion of a colony of polyps Medusa bud Medusa Gonad 1 mm Key Haploid (n) Diploid (2n) MEIOSIS Sperm Egg FERTILIZATION SEXUAL REPRODUCTION Zygote

Figure Feeding polyp Reproductive polyp Portion of a colony of polyps Medusa bud Medusa Gonad 1 mm Key Haploid (n) Diploid (2n) MEIOSIS Sperm Egg FERTILIZATION SEXUAL REPRODUCTION ASEXUAL REPRODUCTION (BUDDING) Developing polyp Planula (larva) Mature polyp Zygote

Figure 33.8a 1 mm

Scyphozoans In the class Scyphozoa, jellies (medusae) are the prevalent form of the life cycle © 2011 Pearson Education, Inc.

Cubozoans In the class Cubozoa, which includes box jellies and sea wasps, the medusa is box-shaped and has complex eyes Cubozoans often have highly toxic cnidocytes © 2011 Pearson Education, Inc.

Anthozoans Class Anthozoa includes the corals and sea anemones, and these cnidarians occur only as polyps Corals often form symbioses with algae and secrete a hard external skeleton © 2011 Pearson Education, Inc.

Concept 33.3: Lophotrochozoans, a clade identified by molecular data, have the widest range of animal body forms Bilaterian animals have bilateral symmetry and triploblastic development Most have a coelom and a digestive tract with two openings The clade Bilateria contains Lophotrochozoa, Ecdysozoa, and Deuterostomia © 2011 Pearson Education, Inc.

Figure 33.UN03 Porifera Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia Bilateria

The clade Lophotrochozoa was identified by molecular data Some develop a lophophore for feeding, others pass through a trochophore larval stage, and a few have neither feature Lophotrochozoa includes the flatworms, rotifers, ectoprocts, brachiopods, molluscs, and annelids © 2011 Pearson Education, Inc.

Flatworms Members of phylum Platyhelminthes live in marine, freshwater, and damp terrestrial habitats Although flatworms undergo triploblastic development, they are acoelomates They are flattened dorsoventrally and have a gastrovascular cavity with one opening Gas exchange takes place across the surface, and protonephridia regulate the osmotic balance © 2011 Pearson Education, Inc.

Flatworms are divided into two lineages –Catenulida, or “chain worms,” reproduce asexually by budding –Rhabditophora are more diverse and include both free-living and parasitic species © 2011 Pearson Education, Inc.

Figure mm

The best-known rhabditophorans are planarians Planarians live in fresh water and prey on smaller animals Planarians have light-sensitive eyespots and centralized nerve nets © 2011 Pearson Education, Inc. Free-Living Species

The planarian nervous system is more complex and centralized than the nerve nets of cnidarians Planarians are hermaphrodites and can reproduce sexually, or asexually through fission © 2011 Pearson Education, Inc.

Figure Pharynx Gastrovascular cavity Gastrovascular cavity Mouth Eyespots Ventral nerve cords Ganglia

Parasitic Species Parasitic rhabditophorans live in or on other animals Two important groups of parasitic rhabditophorans are the trematodes and the tapeworms © 2011 Pearson Education, Inc.

Trematodes Trematodes parasitize a wide range of hosts, and most have complex life cycles with alternating sexual and asexual stages Trematodes that parasitize humans spend part of their lives in snail hosts They produce surface proteins that mimic their host and release molecules that manipulate the host’s immune system © 2011 Pearson Education, Inc.

Human host Motile larva Snail host Ciliated larva Mature flukes Female 1 mm Male Figure 33.11

Figure 33.11a Mature flukes Female 1 mm Male

Tapeworms Tapeworms are parasites of vertebrates and lack a digestive system Tapeworms absorb nutrients from the host’s intestine © 2011 Pearson Education, Inc.

The scolex contains suckers and hooks for attaching to the host Proglottids are units that contain sex organs and form a ribbon behind the scolex Fertilized eggs, produced by sexual reproduction, leave the host’s body in feces © 2011 Pearson Education, Inc.

Figure Proglottids with reproductive structures Hooks Sucker 100  m Scolex

Figure 33.12a Hooks Sucker 100  m

Rotifers Rotifers, phylum Rotifera, are tiny animals that inhabit fresh water, the ocean, and damp soil Rotifers are smaller than many protists but are truly multicellular and have specialized organ systems © 2011 Pearson Education, Inc.

Figure Jaws Crown of cilia 0.1 mm Stomach Anus

Rotifers have an alimentary canal, a digestive tube with a separate mouth and anus that lies within a fluid-filled pseudocoelom Rotifers reproduce by parthenogenesis, in which females produce offspring from unfertilized eggs Some species are unusual in that they lack males entirely © 2011 Pearson Education, Inc.

Lophophorates: Ectoprocts and Brachiopods Lophophorates have a lophophore, a crown of ciliated tentacles around their mouth Lophophorates have a true coelom Lophophorates include two phyla: Ectoprocta and Brachiopoda © 2011 Pearson Education, Inc.

Ectoprocts (also called bryozoans) are sessile colonial animals that superficially resemble plants A hard exoskeleton encases the colony, and some species are reef builders © 2011 Pearson Education, Inc.

Figure (a) Ectoprocts, colonial lophophorates Lophophore (b) Lampshell, a brachiopod

Figure 33.14a (a) Ectoprocts, colonial lophophorates Lophophore

Brachiopods superficially resemble clams and other hinge-shelled molluscs, but the two halves of the shell are dorsal and ventral rather than lateral as in clams Brachiopods are marine and attach to the seafloor by a stalk © 2011 Pearson Education, Inc.

Figure 33.14b Lophophore (b) Lampshell, a brachiopod

Molluscs Phylum Mollusca includes snails and slugs, oysters and clams, and octopuses and squids Most molluscs are marine, though some inhabit fresh water and some snails and slugs are terrestrial Molluscs are soft-bodied animals, but most are protected by a hard shell © 2011 Pearson Education, Inc.

All molluscs have a similar body plan with three main parts –Muscular foot –Visceral mass –Mantle Many molluscs also have a water-filled mantle cavity and feed using a rasplike radula © 2011 Pearson Education, Inc.

Figure Nephridium Visceral mass Heart Coelom Mantle cavity Anus Gill Gonads Heart Intestine Stomach Shell Radula Mouth Esophagus Nerve cords Foot Digestive tract Mouth Radula

Most molluscs have separate sexes with gonads located in the visceral mass, but many snails are hermaphrodites The life cycle of many molluscs includes a ciliated larval stage called a trochophore © 2011 Pearson Education, Inc.

Four of the major classes of molluscs are –Polyplacophora (chitons) –Gastropoda (snails and slugs) –Bivalvia (clams, oysters, and other bivalves) –Cephalopoda (squids, octopuses, cuttlefish, and chambered nautiluses) © 2011 Pearson Education, Inc.

Chitons Chitons are oval-shaped marine animals encased in an armor of eight dorsal plates They use their foot like a suction cup to grip rock, and their radula to scrape algae off the rock surface © 2011 Pearson Education, Inc.

Figure 33.16

Gastropods About three-quarters of all living species of molluscs are gastropods © 2011 Pearson Education, Inc.

Figure (a) A land snail (b) A sea slug (nudibranch)

Figure 33.17a (a) A land snail

Figure 33.17b (b) A sea slug (nudibranch)

Most gastropods are marine, but many are freshwater and terrestrial species The most distinctive characteristic of gastropods is torsion, which causes the animal’s anus and mantle to end up above its head; torsion is different from the coiling of a shell Most have a single, spiraled shell Slugs lack a shell or have a reduced shell © 2011 Pearson Education, Inc.

Figure Mouth Anus Mantle cavity Stomach Intestine

Bivalves Bivalves are marine and include many species of clams, oysters, mussels, and scallops They have a shell divided into two halves drawn together by adductor muscles Some bivalves have eyes and sensory tentacles along the edge of their mantle © 2011 Pearson Education, Inc.

Figure 33.19

The mantle cavity of a bivalve contains gills that are used for feeding as well as gas exchange © 2011 Pearson Education, Inc.

Mantle Hinge area Digestive gland Mouth Shell Palp Foot Mantle cavity Gonad Gill Incurrent siphon Water flow Excurrent siphon Anus Adductor muscle (one or two) Gut Coelom Heart Figure 33.20

Cephalopods Cephalopods are carnivores with beak-like jaws surrounded by tentacles of their modified foot Most octopuses creep along the sea floor in search of prey © 2011 Pearson Education, Inc.

Figure Squid Octopus Chambered nautilus

Figure 33.21a Squid

Squids use their siphon to fire a jet of water, which allows them to swim very quickly © 2011 Pearson Education, Inc.

Octopus Figure 33.21b

One small group of shelled cephalopods, the nautiluses, survives today © 2011 Pearson Education, Inc.

Figure 33.21c Chambered nautilus

Cephalopods have a closed circulatory system, well-developed sense organs, and a complex brain Shelled cephalopods called ammonites were common but went extinct at the end of the Cretaceous 65.5 million years ago © 2011 Pearson Education, Inc.

Molluscs are the animal group with the largest number of recent extinctions The most threatened groups are –Freshwater bivalves, including pearl mussels –Terrestrial gastropods, including Pacific island land snails These molluscs are threatened by habitat loss, pollution, and non-native species © 2011 Pearson Education, Inc. Protecting Freshwater and Terrestrial Molluscs

Other invertebrates Insects Fishes Mammals An endangered Pacific island land snail, Partula suturalis Molluscs Recorded extinctions of animal species (Data: International Union for Conservation of Nature, 2008) Reptiles (excluding birds) Amphibians Birds Workers on a mound of pearl mussels killed to make buttons (ca. 1919) Figure 33.22

Figure 33.22a An endangered Pacific island land snail, Partula suturalis

Figure 33.22b Other invertebrates Insects Fishes Mammals Molluscs Recorded extinctions of animal species (Data: International Union for Conservation of Nature, 2008) Reptiles (excluding birds) Amphibians Birds

Figure 33.22c Workers on a mound of pearl mussels killed to make buttons (ca. 1919)

Annelids Annelids have bodies composed of a series of fused rings Annelids are coelomates The phylum Annelida is divided into two groups –Polychaeta (polychaetes) –Oligochaeta (earthworms and their relatives, and leeches) © 2011 Pearson Education, Inc.

Polychaetes Members of class Polychaetes have paddle-like parapodia that work as gills and aid in locomotion Most polychaetes are marine © 2011 Pearson Education, Inc.

Figure Parapodia

Oligochaetes Oligochaetes (class Oligochaeta) are named for relatively sparse chaetae, bristles made of chitin © 2011 Pearson Education, Inc.

Earthworms Earthworms eat through soil, extracting nutrients as the soil moves through the alimentary canal Earthworms are hermaphrodites but cross-fertilize Some reproduce asexually by fragmentation © 2011 Pearson Education, Inc.

Epidermis Circular muscle Cuticle Longitudinal muscle Dorsal vessel Chaetae Intestine Nephrostome Fused nerve cords Ventral vessel Clitellum Esophagus Pharynx Crop Metanephridium Coelom Septum (partition between segments) Anus Skin Metanephridium Intestine Gizzard Ventral nerve cords with segmental ganglia Circulatory system vessels Subpharyngeal ganglion Mouth Cerebral ganglia Giant Australian earthworm Figure 33.24

Figure 33.24a Giant Australian earthworm

Figure 33.24b Epidermis Circular muscle Cuticle Longitudinal muscle Dorsal vessel Chaetae Intestine Nephrostome Fused nerve cords Ventral vessel Metanephridium Coelom Septum (partition between segments) Anus

Clitellum Esophagus Pharynx Crop Skin Metanephridium Intestine Gizzard Ventral nerve cords with segmental ganglia Circulatory system vessels Subpharyngeal ganglion Mouth Cerebral ganglia Anus Figure 33.24c

Most species of leeches live in fresh water; some are marine or terrestrial Leeches include predators of invertebrates, and parasites that suck blood Leeches secrete a chemical called hirudin to prevent blood from coagulating © 2011 Pearson Education, Inc. Leeches