Chapter 33 Invertebrates

Fig. 33-1 Figure 33.1 What function do the red whorls of this organism have?

Overview: Life Without a Backbone Invertebrates are animals that lack a backbone They account for 95% of known animal species

Sponges/ “Porifera” Calcarea and Silicea ANCESTRAL PROTIST Cnidaria Fig. 33-2 Calcarea and Silicea Sponges/ “Porifera” ANCESTRAL PROTIST Cnidaria Common ancestor of all animals Mollusca/ Annelida Eumetazoa Nematoda/ Arthropoda Figure 33.2 Review of animal phylogeny Bilateria Chordata/ Echinodermata

Phylum Choanocytes Phylum Cnidaria (“Porifera”) Fig. 33-3a A jelly A sponge Figure 33.3 Invertebrate diversity Phylum Choanocytes Phylum Cnidaria (“Porifera”)

Phylum Platyhelminthes Phylum Rotifera Fig. 33-3a A marine flatworm A rotifer (LM) Figure 33.3 Invertebrate diversity Phylum Platyhelminthes Phylum Rotifera

Phylum Mollusca Phylum Annelida Fig. 33-3m An octopus A marine annelid Figure 33.3 Invertebrate diversity Phylum Mollusca Phylum Annelida

Phylum Nematoda Phylum Arthropoda Fig. 33-3s Figure 33.3 Invertebrate diversity A scorpion (an arachnid) A roundworm Phylum Nematoda Phylum Arthropoda

Phylum Echinodermata Phylum Chordata Fig. 33-3v A sea urchin Figure 33.3 Invertebrate diversity A tunicate Phylum Echinodermata Phylum Chordata

Concept 33.1: Sponges are basal animals that lack true tissues Sponges are sedentary, filter feeding animals from the phyla Calcarea and Silicea “Porifera” They live in both fresh and marine waters Sponges lack true tissues and organs Possess collar cells to propel water through the body and strain food particles. Food digested intracellularly by amebocytes Most asymmetrical http://www.youtube.com/watch?v=RmPTM965-1c&feature=related (sponge feeding)

Azure vase sponge (Callyspongia plicifera) Fig. 33-4 Food particles in mucus Flagellum Choanocyte Choanocyte Collar Osculum Azure vase sponge (Callyspongia plicifera) Spongocoel Phagocytosis of food particles Amoebocyte Pore Spicules Figure 33.4 Anatomy of a sponge Epidermis Water flow Amoebocytes Mesohyl

Concept 33.2: Cnidarians are an ancient phylum of eumetazoans All animals except sponges and a few other groups are animals with true tissues (Eumetazoa) Phylum Cnidaria: jellies, corals, sea anemones Radial symmetrical carnivores Diplobastic - Two body layers: ectoderm & endoderm Possess gastrovascular cavity (not a complete tube) and nematocysts There are two variations on the body plan: the sessile polyp and motile medusa

Mouth/anus Tentacle Polyp Medusa Gastrovascular cavity Gastrodermis Fig. 33-5 Mouth/anus Tentacle Polyp Medusa Gastrovascular cavity Gastrodermis Mesoglea Body stalk Epidermis Figure 33.5 Polyp and medusa forms of cnidarians Tentacle Mouth/anus

Tentacle Cuticle of prey Thread Nematocyst “Trigger” Thread discharges Fig. 33-6 Tentacle Cuticle of prey Thread Nematocyst “Trigger” Figure 33.6 A cnidocyte of a hydra Thread discharges Thread (coiled) Cnidocyte

(a) Colonial polyps (class Hydrozoa) Fig. 33-7 (b) Jellies (class Scyphozoa) (c) Sea wasp (class Cubozoa) (d) Sea anemone (class Anthozoa) Figure 33.7 Cnidarians (a) Colonial polyps (class Hydrozoa)

Conceptual Summary Sponges and cnidarians are almost entirely marine and are considered primitive because they do not possess three body layers nor true organs http://www.youtube.com/watch?v=zkF_1r6ll54&feature=related (hydra eating) http://www.youtube.com/watch?v=a5oHMjGqjyo (budding in hydra)

Reproductive polyp Feeding polyp Medusa bud Medusa ASEXUAL Fig. 33-8-1 Reproductive polyp Feeding polyp Medusa bud Medusa ASEXUAL REPRODUCTION (BUDDING) Portion of a colony of polyps Figure 33.8 The life cycle of the hydrozoan Obelia 1 mm Key Haploid (n) Diploid (2n)

Reproductive polyp Feeding polyp Medusa bud Gonad Medusa Egg Sperm Fig. 33-8-2 Reproductive polyp Feeding polyp Medusa bud MEIOSIS Gonad Medusa Egg Sperm SEXUAL REPRODUCTION ASEXUAL REPRODUCTION (BUDDING) Portion of a colony of polyps FERTILIZATION Figure 33.8 The life cycle of the hydrozoan Obelia Zygote 1 mm Key Haploid (n) Diploid (2n)

Medusa produced by asexual budding Reproductive polyp Feeding polyp Fig. 33-8-3 Medusa produced by asexual budding Reproductive polyp Feeding polyp Medusa bud MEIOSIS Gonad Medusa Egg Sperm SEXUAL REPRODUCTION ASEXUAL REPRODUCTION (BUDDING) Portion of a colony of polyps FERTILIZATION Figure 33.8 The life cycle of the hydrozoan Obelia Zygote 1 mm Developing polyp Planula (larva) Key Mature polyp Haploid (n) Diploid (2n)

Platyhelminthes: Flatworms Acoelomates – solid body, without a body cavity Bilateral symmetry and beginnings of cephalization Development of true organs, tripbloblastic (three body layers); ectoderm, endoderm, mesoderm No coelom (body cavity) Digestibe tract incomplete – only one opening that braches throughout the body to distribute food http://www.youtube.com/watch?v=5fx-YgcP8Gg (flatworm mating behavior – Rated R)

Fig. 33-9 Figure 33.9 A marine flatworm (class Turbellaria)

Pharynx Gastrovascular cavity Mouth Eyespots Ganglia Fig. 33-10 Pharynx Gastrovascular cavity Mouth Figure 33.10 Anatomy of a planarian, a turbellarian Eyespots Ganglia Ventral nerve cords

Tapeworms are parasites of vertebrates and lack a digestive system Fig. 33-12 Tapeworms are parasites of vertebrates and lack a digestive system Tapeworms absorb nutrients from the host’s intestine Fertilized eggs, produced by sexual reproduction, leave the host’s body in feces 200 µm Proglottids with reproductive structures Hooks Sucker Figure 33.12 Anatomy of a tapeworm Scolex

Rotifera Pseudocoelomates – body cavity between digestibe tract and body wall is not completely lined by mesoderm Rotifers have an alimentary canal, a digestive tube with a separate mouth and anus (complete digestive tract) that lies within a fluid-filled pseudocoelom http://www.youtube.com/watch?v=PALgTXQOqQo&feature=related (rotifer feeding)

Jaws Crown of cilia Anus Stomach 0.1 mm Fig. 33-13 Figure 33.13 A rotifer Anus Stomach 0.1 mm

Nematoda: Roundworms Nematodes, or roundworms, are found in most aquatic habitats, in the soil, in moist tissues of plants, and in body fluids and tissues of animals Pseudocoelomates They have an alimentary canal, but lack a circulatory system Reproduction in nematodes is usually sexual, by internal fertilization http://video.google.com/videoplay?docid=-2019570087567872766# (C. elegans crawling)

Fig. 33-25 Figure 33.25 A free-living nematode (colorized SEM) 25 µm

Conceptual Summary Flatworms and roundworms have bilateral symmetry, the beginnings of cephalization, and three body layers with well developed tissues and organs. Phyla include many important parasites of humans.

All of the animals that we cover from this point on are coelomates – body cavity (coelom) is completely lined by mesoderm. Groups are divided as protostomes or deuterostomes

Mollusca Phylum Mollusca includes snails and slugs, oysters and clams, and octopuses and squids Basic body plan of muscular head-food, with body on top a loosely covered mantle which may secrete a shell Gastropods have a well defined head, tentacles and elongated flattened foot Marine and freshwater filter feeders have a body flattened between two valves of a hinged she. Bivalvia Cephalopods are on the the most advanced invertebrate groups (octopus, squid, nautilus) Protostomes

Nephridium Visceral mass Heart Coelom Intestine Gonads Mantle Stomach Fig. 33-15 Nephridium Visceral mass Heart Coelom Intestine Gonads Mantle Stomach Mantle cavity Shell Mouth Radula Anus Gill Figure 33.15 The basic body plan of a mollusc Radula Mouth Nerve cords Foot Esophagus

Fig. 33-16 Figure 33.16 A chiton

Fig. 33-17 (a) A land snail Figure 33.17 Gastropods (b) A sea slug

Fig. 33-19 Figure 33.19 A bivalve

Coelom Hinge area Mantle Gut Heart Adductor muscle Digestive gland Fig. 33-20 Coelom Hinge area Mantle Gut Heart Adductor muscle Digestive gland Anus Mouth Excurrent siphon Figure 33.20 Anatomy of a clam Shell Water flow Palp Foot Incurrent siphon Mantle cavity Gonad Gill

Fig. 33-21 Octopus Squid Figure 33.21 Cephalopods Chambered nautilus

http://www. youtube. com/watch http://www.youtube.com/watch?v=OBg0k9GbHiw&feature=fvwrel (squid inking) http://www.youtube.com/watch?v=QMFqV4SJLWg (nautilus)

Annelida: Segmented Worms Possess a coelom and closed circulatory system Body segmented - septa Protostomes

Giant Australian earthworm Pharynx Intestine Fig. 33-22 Cuticle Septum (partition between segments) Epidermis Coelom Circular muscle Metanephridium Longitudinal muscle Anus Dorsal vessel Chaetae Intestine Fused nerve cords Ventral vessel Nephrostome Metanephridium Clitellum Figure 33.22 Anatomy of an earthworm, an oligochaete Esophagus Crop Giant Australian earthworm Pharynx Intestine Cerebral ganglia Gizzard Mouth Ventral nerve cord with segmental ganglia Subpharyngeal ganglion Blood vessels

Fig. 33-23 Figure 33.23 A polychaete Parapodia

Fig. 33-24 Figure 33.24 A leech

Arthropoda: (jointed foot) Major evolutionary advances over other invertebrate groups include exoskeleton (chitin) and jointed appendages Open circulatory system in which fluid called hemolymph is circulated into the spaces surrounding the tissues and organs (fig. 42.3 pg. 900) Main groups are arachnids (spiders, ticks), crustaceans (lobsters, crabs, shrimp, krill), and insects Rotostomes

Cephalothorax Abdomen Antennae (sensory reception) Thorax Head Fig. 33-29 Cephalothorax Abdomen Antennae (sensory reception) Thorax Head Swimming appendages (one pair located under each abdominal segment) Figure 33.29 External anatomy of an arthropod Walking legs Pincer (defense) Mouthparts (feeding)

Fig. 33-30 Figure 33.30 Horseshoe crabs (Limulus polyphemus)

Scorpion Dust mite Web-building spider 50 µm Fig. 33-31 Figure 33.31 Arachnids Web-building spider

Arachnids have an abdomen and a cephalothorax, which has six pairs of appendages, the most anterior of which are the chelicerae Gas exchange in spiders occurs in respiratory organs called book lungs Many spiders produce silk, a liquid protein, from specialized abdominal glands

Stomach Intestine Heart Brain Digestive gland Eyes Ovary Poison gland Fig. 33-32 Stomach Intestine Heart Brain Digestive gland Eyes Ovary Poison gland Figure 33.32 Anatomy of a spider Book lung Anus Gonopore (exit for eggs) Chelicera Pedipalp Spinnerets Sperm receptacle Silk gland

Fig. 33-33 Figure 33.33 A millipede

Fig. 33-34 Figure 33.34 A centipede

Abdomen Thorax Head Compound eye Antennae Heart Cerebral ganglion Fig. 33-35 Abdomen Thorax Head Compound eye Antennae Heart Cerebral ganglion Dorsal artery Crop Anus Vagina Figure 33.35 Anatomy of a grasshopper, an insect Malpighian tubules Ovary Tracheal tubes Mouthparts Nerve cords

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 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 known by such names as maggot, grub, or caterpillar The larval stage looks entirely different from the adult stage http://www.youtube.com/watch?v=NnJA_BkPF_Y (butterfly metamorphosis)

(a) Larva (caterpillar) (b) Pupa (c) Later-stage pupa (d) Emerging Fig. 33-36 (a) Larva (caterpillar) (b) Pupa (c) Later-stage pupa Figure 33.36 Metamorphosis of a butterfly (d) Emerging adult (e) Adult

Most insects have separate males and females and reproduce sexually Individuals find and recognize members of their own species by bright colors, sound, or odors Some insects are beneficial as pollinators, while others are harmful as carriers of diseases, or pests of crops

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 branched appendages that are extensively specialized for feeding and locomotion Most crustaceans have separate males and females

(a) Ghost crab (b) Krill (c) Barnacles Fig. 33-38 Figure 33.38 Crustaceans (b) Krill (c) Barnacles

Conceptual Summary The chitinous exoskeleton of arthropods, with its many jointed appendages modified for a variety of jobs, proved so versatile that the arthropods have undergone impressive adaptive radiation with more species and individuals than any other phylum

Concept 33.5: Echinoderms and chordates are deuterostomes Sea stars and other echinoderms, phylum Echinodermata, may seem to have little in common with phylum Chordata, which includes the vertebrates Shared characteristics define deuterostomes (Chordates and Echinoderms) Radial cleavage Formation of the mouth at the end of the embryo opposite the blastopore

Echinodermata: Sea urchins, sea stars and sea cucumbers Sea stars and most other echinoderms are slow-moving or sessile marine animals Deuterostomes Vertebrates are more closely related to echinoderms than to annelids, mollusks or arthropods based on studies of embryonic development Echinoderms have a unique water vascular system, a network of hydraulic canals branching into tube feet that function in locomotion, feeding, and gas exchange Possess a skeleton of calcium carbonate just under the skin Immature have bilateral symmetry, however, most adults have pentaradial symmetry http://www.youtube.com/watch?v=A100m5EpfFI&feature=related (sea star feeding)

Stomach Anus Spine Gills Central disk Digestive glands Madreporite Fig. 33-39 Stomach Anus Spine Gills Central disk Digestive glands Madreporite Radial nerve Figure 33.39 Anatomy of a sea star, an echinoderm Gonads Ring canal Ampulla Podium Radial canal Tube feet

(a) A sea star (class Asteroidea) Fig. 33-40a Figure 33.40 Echinoderms (a) A sea star (class Asteroidea)

(b) A brittle star (class Ophiuroidea) Fig. 33-40b Figure 33.40 Echinoderms (b) A brittle star (class Ophiuroidea)

(c) A sea urchin (class Echinoidea) Fig. 33-40c Figure 33.40 Echinoderms (c) A sea urchin (class Echinoidea)

(d) A feather star (class Crinoidea) Fig. 33-40d Figure 33.40 Echinoderms (d) A feather star (class Crinoidea)

(e) A sea cucumber (class Holothuroidea) Fig. 33-40e Figure 33.40 Echinoderms (e) A sea cucumber (class Holothuroidea)

(f) A sea daisy (class Concentricycloidea) Fig. 33-40f Figure 33.40 Echinoderms (f) A sea daisy (class Concentricycloidea)

Chordates Phylum Chordata consists of two subphyla of invertebrates as well as hagfishes and vertebrates Chordates share many features of embryonic development with echinoderms, but have evolved separately for at least 500 million years

You should now be able to: List the characteristics of the phylum “Porifera” List the characteristics of the phylum Cnidaria that distinguish it from other animal phyla List the characteristics of Platyhelminthes List the characteristics of Mollusca List the characteristics of Annelida List the characteristics of Nematoda List three features that account for the success of Arthropods Describe the developmental similarities between echinoderms and chordates