Invertebrates PDF

D. melanogaster C. elegans Invertebrates Introduction Sea star (Astropecten articulates) common to the eastern and southern coast...

D. melanogaster C. elegans Invertebrates Introduction Sea star (Astropecten articulates) common to the eastern and southern coasts of the US (credit: modification of work by Mark Walz) To most people, vertebrates, especially mammals and birds are the animals that attract our attention. Concentrating on vertebrates, however, gives us a rather biased and limited view of animal diversity, because it ignores nearly 97 percent of the animal kingdom! Invertebrates are animals that lack a cranium and a defined vertebral column or spine. Does this mean they don’t have skeletons? Of course not! Skeletons don’t have to be made of bones! Exoskeletons Hydrostatic skeletons Endoskeletons  Animal Phylogenetic Tree The phylogenetic tree of animals is based on morphological, fossil, and genetic evidence. All animals share a common ancestor Metazoa They are a monophyletic clade. (animals) Animal Phylogenetic Tree Domain: Eukarya Kingdom: Animalia Remember, because the choanocyte cells found in sponges are similar in morphology to Choanoflagellates, it is hypothesized that sponges and choanoflagellates share a common ancestor. Other animals have similar cells, but these cells are not seen in other protists, fungi or plants. Porifer a (spong Animal Phylogenetic Tree Domain: Eukarya Kingdom: Animalia Porifera = sponges Considered base of animal tree (least derived) No tissues asymmetrical Porifer a (spong Animal Phylogenetic Tree Eumetazoa are animals that have Eumetaz have true tissues. oa (speciali zed tissues) Diploblasts have two Cnidari tissue layers. a Some Eumetazoans are diploblastic and have radial symmetry Ctenoph Animal Phylogenetic Tree Bilateria (bilateral symmetry , Eumetazoa are animals that have triploblas tic) have true tissues. Most animal phyla have bilateral symmetry, are triploblastic and belong to the clade Bilateria Bilateral symmetry is when a central longitudinal plane divides the body into 2 Triploblasts have 3 equal but tissue layers. opposite halves Animal Development – Coelom Formation Protostomes Deuterostomes VS Coelom forms from splits in mesoderm; Coelom forms from mesodermal out- Mouth develops from blastopore pocketings; Anus develops from blastopore Animal Phylogenetic Tree Protostomes The clade Bilateria is subdivided Subdivided into 2 groups of into 2 smaller clades: phyla: Lophotrochozoa Ecdysozoa Deuterostomes Two phyla Echinoderms Chordates Animal Phylogenetic Tree Protostomes Subdivided into 2 groups: Lophotrochozoa Have particular feeding and larval features that unite them as a clade Animal Phylogenetic Tree Protostomes Subdivided into 2 groups: Ecdysozoa Secrete external skeletons (exoskeletons) and grow by molting (ecdysis) We will cover the following: Phylum Porifera (sponges) Phylum Cnidaria (anemones, jellies, etc.) Lophotrochozoa Phylum Platyhelminthes (flatworms) Phylum Mollusca (snails, clams, octopuses, etc.) Phylum Annelida (earthworms, leeches, etc.) Ecdysozoa Phylum Nematoda (roundworms) Phylum Arthropoda (insects, crabs, spiders, etc.) Deuterostomia Phylum Echinodermata (sea stars, sea urchins, etc.) Phylum Chordata (sea squirts, lancelets, vertebrates too, but we will cover later). Classifying organisms To keep sense of animal diversity and the many different groups that you will be learning about as we cover invertebrates and vertebrates, you will need to keep track of the taxonomical and evolutionary relationships. Below are the taxonomical groups in order from most broad to most specific. Domain Kingdom Phylum You’ll need to know for sure Class. You’ll need to know only for some phyla Order Family Genus Species Species is given as genus + species, for example (Homo sapiens), so the specific epithet is what the species is called. Animal Phylogenetic Tree Domain: Eukarya Kingdom: Animalia Phylum: Porifera Porifer a (spong Phylum Porifera Pronounced ‘pore-if-er-a’ Sponge biodiversity and morphotypes at the lip of a wall site in 60 feet of water. Included are the yellow tube sponge, Aplysina fistularis, the purple vase sponge, Niphates digitalis, the red encrusting sponge, Spirastrella coccinea [nl], and the gray rope sponge, Callyspongia sp. The phylum Porifera, or sponges, are among the simplest animals. They are generally considered to be the base of the animal phylogenetic tree. Sponges are aquatic and most live in a marine environment. There are at least 5,000 named species of sponges, and likely thousands more yet to be classified! Sponges do not have true tissues. They do not have nervous, digestive, circulatory systems or other organ systems. Phylum Porifera: Global Diversity of the Porifera Numbers of sponge species recorded in each of 232 marine ecoregions of the world extracted from the World Porifera Database (available: www.marinespecies.org/porifera, accessed 2011 Aug 31).  Phylum Porifera Sponge larvae can swim; however, adults are sessile and spend their life attached to a substrate (coral, rock, other sponges, etc.). Since water is vital to sponges for feeding, excretion, and gas exchange, their body structure facilitates the movement of water through the sponge. Sponges are asymmetrical in form, although some may appear to have radial symmetry. Most sponges ingest bacteria or organic matter dissolved in the water for food. Morphology of Sponges The morphology of the simplest sponges takes the shape of an irregular cylinder with a large central cavity (called the spongocoel). Water enters into the spongocoel through numerous pores, that create openings in the body wall. The pores are why the phylum is called Porifera. Water entering the spongocoel is expelled via a large opening at the top. This involves active pumping. Watch this video: Video from “Shape of Life” series (2:17 min) Between the outer layer and the feeding chambers of the sponge is a jelly-like substance (called the mesohyl) which contains collagenous fibers. The mesohyl acts like an endoskeleton. Morphology of Sponges Sponges have several cell types that have different jobs but can transform into other cell types and can migrate to new locations! The defining cell for sponges is the choanocyte, a flagellated feeding cell. Remember that the choanocytes are are similar in appearance to unicellular choanoflagellates (Protista) and are thought to share common ancestry. Amoebocytes engulf food that enter the choanocyte The silica spicules secreted by the sclerocytes provide structure and deter predation. Phylum Porifera: Reproduction Sponges reproduce by sexual as well as asexual methods. Asexual reproduction: fragmentation (during this process, a piece of the sponge breaks off, settles on a new substrate, and develops into a new individual) budding (a genetically identical outgrowth grows from the parent and eventually detaches or remains attached to form a colony). Sexual reproduction: oocytes arise by the differentiation of amoebocytes. sperm come from the differentiation of choanocytes. Sponges are monoecious (hermaphroditic), which means that one individual can produce both gametes (eggs and sperm) and self fertilization. Since the gametes are released into the water, fertilization can also occur between two different sponges, which would produce more genetic diversity. Animal Phylogenetic Tree Domain: Eukarya Kingdom: Animalia Phylum: Cnidaria Cnidari a Phylum Cnidaria Pronounced ‘Ni-dair-ee-uh’, (Ni has a long i – rhymes with ‘eye’) The name Cnidaria comes from the Greek word "cnidos," which means stinging nettle. Cnidarians are found in aquatic, mostly marine, environments. There are over 11,000 species! Four examples of Cnidaria : A jellyfish Chrysaora melanaster , A gorgonian Annella mollis, A rocky coral Acropora cervicornis, A sea anemone Nemanthus annamensis Phylum Cnidaria Cnidarians have three key features Diploblastic – two tissues layers, the endoderm and ectoderm (so have ‘true tissues’) Radial symmetry – any way you slice it vertically, you end up with mirror images pieces. Specialized cells called cnidocytes that contain nematocysts. These are used to sting and capture prey, and can sting humans too! Animals from the phylum Cnidaria have stinging cells called cnidocytes. Cnidocytes contain large organelles called (a) nematocysts that store a coiled thread and barb. When hair-like projections on the cell surface are touched, (b) the thread, barb, and a toxin are fired from the organelle. Phylum Cnidaria: Morphology Cnidarians have two distinct body plans, the medusa (a) and the polyp (b). Blue = endoderm Red = exoderm Two distinct body plans are found in Cnidarians: the sessile, or non moving polyp form and the motile (moving) medusa. Notice how one body form is basically the upside down version of the other. All cnidarians have two membrane layers, shown in red and blue, with a jelly-like mesoglea between them. Species can have one body form, or the other, and some have both, depending on the stage in the life cycle. Phylum Cnidaria: Morphology An example of the polyp form is found in the sea Four examples of Cnidaria : A jellyfish Chrysaora melanaster , A gorgonian Annella mollis, A rocky anemones. coral Acropora cervicornis, A sea anemone Nemanthus The typical form of medusa is found in the group annamensis called the “sea jellies” (jellyfish). Coral and gorgonians have polyps that produce the large, calcified structures around them. Phylum Cnidaria: Anatomy An important step is evolution is that Cnidaria have a rudimentary nervous system, called a nerve net that has nerve cells organized in a network scattered across the body. Despite the simplicity of the nervous system, it coordinates the complicated movement of the tentacles, the drawing of captured prey to the mouth, the digestion of food, and the expulsion of waste. Watch this video that shows a box jelly (class Cubozoa) capturing and digesting a fish. You can turn the music off if you would like. https://youtu.be/AQJG4HWdZIs Phylum Cnidaria: Anatomy For digestion, food is brought into a central digesting sac called gastrovascular cavity that is shown in blue on the diagram. The gastrovascular cavity has only one opening that serves as both a mouth and an anus. Yeah, I know. This is an incomplete digestive system. Phylum Cnidaria: Anatomy There is no circulatory, respiratory or excretory system. Cnidarian cells exchange oxygen and carbon dioxide by diffusion between cells in the epidermis and water in the environment, and between cells in the gastrodermis and water in the gastrovascular cavity. Nitrogenous wastes simply diffuse from the cells into the water outside the animal or into the gastrovascular cavity. Phylum Cnidaria: Anatomy Reproduction Asexual – budding Sexual – release of gametes into the water Hydrostatic skeleton Made of mesoglea, a non-living jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick. Locomotion Medusae swim by jet propulsion: muscles squeeze water out of the cavity inside the bell. The tissue layers are very thin so they provide too little power to swim against currents and just enough to control movement within currents Some polyps are able to move by hopping. Phylum Cnidaria: Diversity The Cnidaria are divided into two monophyletic clades: the Anthozoa and the Medusozoa. The class Anthozoa includes the corals, sea fans, sea whips, and the sea anemones. only sessile polyp forms The Medusozoa include include species with both polyp and medusa forms in their life cycle, and have three classes. Scyphozoa Cubozoa Hydrozoa Phylum Cnidaria: Diversity Coral outcrop on the Great Barrier Reef. Brain Starburst sea coral anemone Class Anthozoa Corals, sea anemones Polyp body plan In corals, there is a calcium carbonate house build around the coral polyp. Usually sessile, but watch this video: https:// www.youtube.com/watch?v=ysOmq71fcMk Phylum Cnidaria: Diversity Class Scyphozoa Medusa is prominent “true jellies” Download for free at http://cnx.org/contents/[email protected] Animal Phylogenetic Tree Protostomes Subdivided into 2 groups: Lophotrochozoa Have particular feeding and larval features that unite them as a clade Superphylum Lophotrochozoa Pronounced ‘Lo-fo-tro-ko-zoa’ Lophophor e feeding Trochophore larva apparatus The superphylum Lophotrochozoa is a grouping of phyla that came about due to a reorganization of invertebrate phyla following analysis of ribosomal RNA sequences. The name was given because most of the animals have either a lophophore or a trochophore larva. Lophophore feeding apparatus, which is a ring of cilia around the mouth. Trochophore larva have two bands of cilia around the body. The phyla of animals in this superphylum include flatworms, rotifers, ribbon worms, mollusks and annelids. Superphylum Lophotrochozoa Animals belonging to superphylum Lophotrochozoa have the following characteristics: triploblastic (have three germ layers) bilaterally symmetrical a longitudinal section will divide them into right and left sides that are superficially symmetrical. the beginning of cephalization the evolution of a concentration of nervous tissues and sensory organs in the head of the organism—exactly where a mobile bilaterally symmetrical organism first encounters its environment. Are protostomes the blastopore, or the point of invagination of the ectoderm (outer germ layer), becomes the mouth opening into the alimentary canal. include acoelomate, pseudocoelomate, and eucoelomates. Animal Phylogenetic Tree Domain: Eukarya Platyhelmin Kingdom: Animalia thes Super phylum: (flatworms) Lophotrochozoa Phylum: Platyhelminthes Phylum Platyhelminthes Pronounced ‘plat-ee-hell-minth-ees Flatworms exhibit significant diversity. (a) A blue Pseudoceros flatworm (Pseudoceros bifurcus); (b) gold speckled flatworm (Thysanozoon nigropapillosum). (credit a: modification of work by Stephen Childs; b: modification of work by Pril Fish.) The flatworms are acoelomates. the mesodermal layer forms a solid mass between the outer epidermal surface and the cavity of the digestive system. There are over 20,000 different species catalogued! Phylum Platyhelminthes: Physiological Processes Diagram a planarian, a representative flatworm that has a gastrovascular cavity (orange) with one opening that serves as both mouth and anus. Do not have a complete gut. Most have a branching gastrovascular cavity and a single mouth/anus. Tapeworms, which are parasitic, do not even have a gut! Phylum Platyhelminthes: Physiological Processes The nervous system (gold) is composed of two interconnected nerve cords running the length of the body, with cerebral ganglia and eyespots at the anterior end. This is a primitive development of cephalization! Phylum Platyhelminthes: Physiological Processes There is neither a circulatory nor a respiratory system, with gas and nutrient exchange dependent on diffusion. This necessarily limits the thickness of the body in these organisms, constraining them to be “flat” worms. Phylum Platyhelminthes: Physiological Processes Reproduction Most flatworm species are monoecious (hermaphrodites). Asexual reproduction by fission occurs in some species. Regeneration Some free-living flatworms are capable of remarkable feats of regeneration in which an individual may regrow its head or tail after being severed, or even several heads if it is cut lengthwise. Watch this video – it shows regeneration, and also how planaria swim, eat and poop! https://youtu.be/m12xsf5g3Bo Phylum Platyhelminthes: Physiological Processes Some free-living flatworms are capable of remarkable feats of regeneration in which an individual may regrow its head or tail after being severed, or even several heads if it is cut lengthwise. Watch this video – it shows regeneration, and also how planaria swim, eat and poop! https://youtu.be/m12xsf5g3Bo Phylum Platyhelminthes: Diversity of Flatworms Platyhelminthes are traditionally divided into four classes Class Turbellaria – Planaria Class Monogenaea Class Trematoda – flukes Class Cestoda – tapeworms Download for free at http://cnx.org/contents/[email protected] Phylum Platyhelminthes: Diversity of Flatworms Most free-living flatworms are marine but some species are found in freshwater or moist terrestrial environments. There are free-living and parasitic flatworms. The free-living species are predators or scavengers. The turbellaria (planaria) are free living predators and scavengers. Parasitic forms feed by absorbing nutrients provided by their hosts. The monogeneans, trematodes (flukes), and cestodes (tapeworms), are parasites. Tapeworm (Taenia spp.) infections occur when humans consume raw or undercooked infected meat. (credit: modification of work by CDC) Animal Phylogenetic Tree Domain: Eukarya Kingdom: Animalia Super phylum: Lophotrochozoa Phylum: Mollusca Mollusca (Mollusk s) Phylum Mollusca This enormous phylum includes chitons, tusk shells, snails, slugs, nudibranchs, sea butterflies, clams, mussels, oysters, squids, octopuses, and nautiluses. There have been over 85,000 species described and there are many more undiscovered! This phylum is highly diverse in form, size, behavior and habitat. Mollusks are predominantly a marine group of animals; however, they are also known to inhabit freshwater as well as moist terrestrial habitats. Underside of an octopus, featuring the suckers along its arms attached to the aquarium glass Phylum Mollusca Mollusks are coelomates that display a wide range of morphologies in each class and subclass, but mostly share these key characteristics shown in this diagram of an aquatic gastropod. Phylum Mollusca The large muscular foot is used for movement. Most internal organs are contained in a region called the visceral mass. Above the visceral mass is a fold of tissue called the mantle; the cavity formed by the mantle is filled with water, contains gills, anus and excretory pores The mantle secretes a calcium-carbonate-hardened shell in most mollusks. This protects the visceral mass. The radula is an abrasive tongue like structure. Phylum Mollusca: Reproduction Helix pomatia copulating. Most mollusks are dioecious. There is typically a larval stage. Most cephalopods develop directly into small versions of their adult form. Some octopi care for their young – this is generally not seen in invertebrates. Classification of Phylum Mollusca The phylum Mollusca is a very diverse group of organisms with a dramatic variety of forms. This variability is a consequence of modification of the basic body regions, especially the foot and mantle. The phylum is organized into eight classes. Each molluscan class appears to be monophyletic, and we are still learning about how they are related to each other. We will be looking at four of the classes: Class Polyplacophora Class Gastropoda Class Bivalvia Class Cephalopoda Phylum Mollusca: Class Polyplacophora This is a Lined Chiton, Tonicella lineata. This picture was taken at about 50 feet depth on the west side of Whidbey Island, Washington. These are marine mollusks that have a shell made of eight plates. Polyplacophora means ‘many plates’. Found worldwide, from cold waters through to the tropics. They live on hard surfaces, such as on or under rocks, or in rock crevices mostly intertidal or subtidal zones Have a radula to scrap algae off rocks Chiton teeth have been shown to exhibit the greatest hardness and stiffness of any biomineral material reported to date, being as much as three- times harder than human enamel and the calcium carbonate- based shells of mollusks. Phylum Mollusca: Class Bivalvia These mussels, found in the intertidal zone in Zebra mussels encrusting Cornwall, England, are bivalves. (credit: Mark A. Wilson) marine equipment. Giant clam with divers Includes clams, oysters, mussels, scallops, geoducks, and shipworms. Some are almost microscopic, while others (giant clam), may be one meter in length and weigh 225 kilograms. Found in marine and freshwater habitats. As the name suggests, bivalves are enclosed in two-part valves or shells. Download for free at http://cnx.org/contents/[email protected] Phylum Mollusca: Class Bivalvia Enlarged photo of a scallop showing some of its bright blue eyes The head region is poorly developed with no radula or obvious mouth. Sessile Filter-feeders. During water intake, food particles are captured by the gills and then carried by the movement of cilia forward to the mouth. Watch this video: Filter feeding clam Eyespots and other sensory structures are located along the edge of the mantle in some species. Phylum Mollusca: Class Gastropoda snail Conch Nudibranc Banana slug shell h slug More than half of molluscan species are in the class Gastropoda (“stomach foot”), which includes well- known mollusks like snails, slugs, conchs, cowries, limpets, and whelks. Aquatic gastropods include both marine and freshwater species. All terrestrial mollusks are gastropods. Includes species with and without shells. The foot is modified for crawling, producing a trail of slime. Head with tentacles and eyes. Radula is used to scrape up food particles, watch this video (you only need to watch the first 10 seconds) Grazing snail Phylum Mollusca: Class Cephalopoda The (a) nautilus, (b) giant cuttlefish, (c) reef squid, and (d) blue-ring octopus are all members of the class Cephalopoda. (credit a: modification of work by J. Baecker; credit b: modification of work by Adrian Mohedano; credit c: modification of work by Silke Baron; credit d: modification of work by Angell Williams) The Cephalopoda, (“head foot” animals), includes octopuses, squids, cuttlefish, and nautiluses. Exclusively marine, characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot. Considered the most intelligent of the invertebrates - watch this video: https://youtu.be/abRPaXgJGQg Includes both animals with shells as well as animals in which the shell is reduced or absent. Move by propulsion Carnivorous, the radula is modified as a beak. Watch this video: Octopus feeding ~ 800 extant species, and new species continue to be found! Animal Phylogenetic Tree Domain: Eukarya Kingdom: Animalia Super phylum: Lophotrochozoa Phylum: Annelida (annelid Annelida s) Phylum Annelida Pronounced An-el-id=uh The (a) earthworm, (b) leech, and (c) featherduster are all annelids. (credit a: modification of work by S. Shepherd; credit b: modification of work by “Sarah G...”/Flickr; credit c: modification of work by Chris Gotschalk, NOAA) Phylum Annelida comprises the true, segmented worms. They are coelomates and display bilateral symmetry and have worm-like body. Found in marine, freshwater and moist terrestrial habitats. Approximately 22,000 species have been described. Phylum Annelida: Morphology v v Annelids have a body plan with segmentation, in which several internal and external morphological features are repeated in each body segment. The epidermis is protected by a collagenous, external cuticle. Circular and longitudinal muscles are located interior to the epidermis. The muscles push against the epidermis to great a wavelike motion (peristalsis) that moves the worm. Watch this video: https://youtu.be/0Texxu3p7I8 The effect is a hydrostatic skeleton. Phylum Annelida: Anatomy Most annelids possess a closed circulatory system of dorsal and ventral blood vessels and capillaries. In most, respiration occurs as gas exchange across the moist skin. Annelids have well-developed nervous systems with a ring of fused ganglia present around the pharynx - cephalization. The nerve cord is ventral in position. Phylum Annelida: Anatomy Earthworms may show simultaneous mutual fertilization when they are aligned for copulation. Reproduction Annelids may be either monoecious (as in earthworms and leeches) or dioecious (as in polychaetes). cross-fertilization with another individual is preferred even in hermaphroditic (monoecious) species. Many species can regenerate if cut into pieces and some polychaetes even reproduce asexually by budding or fragmentation. Classification of Phylum Annelida Phylum Annelida contains two classes: 1. Polychaeta (the polychaetes), pronounced ‘poly-keet’ 2. Oligochaeta (the earthworms, leeches, and their relatives), pronounced ‘oh-li-go-keet’. Classification of Phylum Annelida: Polychaeta More than half of the 22,000 species of annelids are marine polychaetes ("many bristles"). Some are sessile, living in tubes that they construct. Elaborate structures used in feeding and respiration may spread out from the tubes. Some polychaetes are filter-feeders that use feather-like appendages to collect small organisms. Others have tentacles, jaws, or to capture prey. Some polychaetes live near hydrothermal vents. These deep-water tubeworms have no digestive tract, but have a symbiotic relationship with bacteria living in their bodies. Spiral tube worm showing the feeding/respiratory structure protruding from the tube. The body of the worm is hidden. Polychaete worm from the genus Synelmis Christmas tree worms on a coral. Each of the colorful ‘trees’ are highly derived structures for feeding and respiration. They protrude from a tube that was build by the worm and hides its body. Classification of Phylum Annelida: Oligochaeta Earthworm with a clitellum, seen here as a protruding segment with different coloration than the rest of the body, is a structure that aids in annelid reproduction. (credit: Rob Hille) Earthworms are the most abundant members of the class Oligochaeta ("few bristles"), distinguished by the presence of a permanent clitellum as well as the small number of reduced chaetae on each segment. Earthworms collect small organisms from soil as they burrow through it. The digestive tract includes a mouth, muscular pharynx, esophagus, crop, muscular gizzard, intestine and anus. Note how this digest tract has specialized organs! Classification of Phylum Annelida: Oligochaeta Hirudo medicinalis Helobdella europaea The oligochaete subclass Hirudinea, are mostly parasitic with some predatory species. Most live in fresh water environments Most leeches are blood-feeders armed with teeth or a muscular proboscis. The best known Hirudinea is the medicinal leech, Hirudo medicinalis. It is effective at increasing blood circulation and breaking up blood clots, and thus can be used to treat some circulatory disorders and cardiovascular diseases. Animal Phylogenetic Tree Protostomes Subdivided into 2 groups: Ecdysozoa Secrete external skeletons (exoskeletons) and grow by molting (ecdysis) Superphylum Ecdysozoa C. Pronounced ‘eck-dis-oh-uh’ elegans D. melanogaster The superphylum Ecdysozoa contains an incredibly large number of species. This is because it contains two of the most diverse animal groups: phylum Nematoda (the roundworms) and phylum Arthropoda (the arthropods). The superphylum Ecdysozoa is believed to be monophyletic—a clade consisting of all evolutionary descendants from one common ancestor. based on phylogenetic trees constructed using 18S ribosomal RNA genes. Superphylum Ecdysozoa C. elegans D. melanogasteSr EM image of Milnesium tardigradum The most prominent distinguishing feature of ecdysozoans is the cuticle—a tough, but flexible exoskeleton that protects these animals from water loss, predators, and other dangers of the external environment. All members of this superphylum periodically go through a molting process that culminates in ecdysis—the actual shedding of the old exoskeleton. The old cuticle is replaced by a new cuticle, which is secreted beneath it, and which will last until the next growth period. Superphylum Ecdysozoa C. elegans D. melanogasteSr EM image of Milnesium tardigradum The Ecdysozoans also have the following key characteristics Bilateral symmetry Triploblastic (endoderm, ectoderm, mesoderm) Protostomes with radial (not spiral) cleavage Spiral cleavage Radial cleavage Animal Phylogenetic Tree Nematoda (round worms Domain: Eukarya Kingdom: Animalia Super phylum: Ecdysozoa Phylum: Nematoda Phylum Nematoda Pronounced ‘knee-muh-toad-uh’ C. elegans The name Nematoda is derived from the Greek word “Nemos,” which means “thread,” and includes all true roundworms. There have been 25,000 species catalogued, and estimates for the total number of nematode species are between 40,000 to 100,000. It is challenging to catalogue them because they all look alike! Present in all habitats, typically in huge numbers. both free-living and parasitic forms. Play a critical role in soil ecosystems. Phylum Nematod: Morphology Scanning electron Scanning electron micrograph shows (a) micrographs of the the soybean cyst nematode nematode (Heterodera Neoterranova glycines) and a scoliodontis, A and nematode egg. (credit B are the head a: modification of work by region, and C, D USDA ARS) and E are the tail region. Nematodes are tiny slender worms: The smallest nematodes are microscopic but some parasitic species can be 1 m in length. The body may have ridges, rings, bristles, or other distinctive structures. The head of a nematode usually has sensory bristles and teeth around the mouth & at the tip of the tail. Nematodes are not segmented, like the Annelids. The epidermis is covered by cuticle which has chitin, the complex carbohydrate that is found in the exoskeleton of insects. Longitudinal muscle cells push against the cuticle to create a hydroskeleton. Nematodes move by thrashing back and forth Phylum Nematod: Anatomy A schematic representation shows the anatomy of a typical nematode. (credit Matt Russell) Nematodes have a complete digestive system with mouth and anus. Nematodes do not have respiratory or circulatory systems and rely on diffusion for exchange of oxygen and carbon dioxide, and for distribution of nutrients. Phylum Nematod: Anatomy A schematic representation shows the anatomy of a typical nematode. (credit Matt Russell) The nervous system is relatively more developed then in the lophotrochozoa, with the nervous system accounting for almost 1/3 of the total cell in the animal. The nervous system features a head ganglion that acts sort of like a brain, and another one in the tail. Phylum Nematod: Anatomy Most species are dioecious, with males and females, but some species, for example C. Elegans have hermaphrodites which produce sperm and eggs and can self fertilize. Hermaphrodites can also mate with males, which is their preference if males are available. Mating with males increases genetic diversity. The sperm are amoeboid, which means they creep like amoebae to the egg! M a l e a n d f Phylum Nematoda: Ecology Nematodes have successfully adapted to nearly every ecosystem: from marine (salt) to fresh water, soils, from the polar regions to the tropics, as well as the highest to the lowest of elevations (including mountains). Ubiquitous in freshwater, marine, and terrestrial environments, where they often outnumber other animals in both individual and species counts, and are found in locations as diverse as mountains, deserts, and oceanic trenches. The world is literally crawling with nematodes! The topsoil is loaded with nematodes. In total, 4.4 × 1020 nematodes inhabit the Earth's topsoil, or approximately 60 billion for each human, with the highest densities observed in tundra and boreal forests. Many nematode species play beneficial roles in ecosystems, but there are also parasitic species. Nematodes are often detritovores or predate on bacteria, protists and fungi. Approximately 1/3 of nematode species are parasitic. Most plant and animal species have potential nematode parasites. Phylum Nematoda: Parasites Some nematodes cause serious illnesses. Heartworm, Dirofilaria immitis, causes cardiac and respiratory failure in dogs. It is carried by mosquitos. Infection of heart of a dog with heartworm nematodes, Dirofilaria immitis, which are the long white strands. Phylum Nematoda: Parasites Female pinworms. The black Ascaris_lumbricoides graduations indicate preserved in a jar. one millimeter. Most nematode infections that infect humans can be prevented by good sanitation. These are the top nematode illness in humans. About 1 billion people, worldwide, suffer from chronic nematode infection. Ascaris lumbricoides which can grow up to 14 inches infects up to one billion world-wide and can affect multiple organ systems. They enter the digestive tract through contaminated water and food. Hook worms, Ancylostoma duodenale and Necator americanus infect the digestive system and can lead to severe anemia as the syphon off iron and nutrients. They enter the feet from fecal contaminated soil. Pin worms are small – 4-12 mm, and commonly infect children throughout the US. They reside in the colon, and the eggs are laid in the folds of the anus where they cause itching. Phylum Nematoda: C. Elegans, Model Organism C. elegans C. elegans is a free-living nematode found in soil that biologists world-wide use a model organism for studying many aspects of cell biology such as cell communication, genetics ,development, neurobiology & aging. Watch this video to see C. Elegans in action, and what biologists can learn from this simple organism. https://youtu.be/zjqLwPgLnV0 Only about a millimeter long, it can be readily grown and maintained in a laboratory. The greatest asset of this nematode is its transparency, which helps researchers to observe and monitor changes within the animal with ease. It is also a simple organism with about 1,000 cells and a genome of only 20,000 genes. It has determinate cleavage, so there is a specific pattern of cell division and development. It was the first multicellular organism that had its entire DNA sequenced! Animal Phylogenetic Tree Arthropo da Domain: Eukarya Kingdom: Animalia Super phylum: Ecdysozoa Phylum: Arthropoda Phylum Arthropoda Pronounced ‘ar-throw-poh-da’ The name “arthropoda” means “jointed feet.” The name aptly describes the invertebrates included in this phylum. Arthropods have probably always dominated the animal kingdom in terms of number of species and likely will continue to do so: An estimated 80 percent of all known animal species are included in this phylum! Arthropods have segmented bodies. Segments can be specialized into tagmata (singular tagma) which are functional groups, such as the head, body and thorax of an insect. Segments or tagma can be modified to have mouth parts, antennae, legs and tail parts, and can vary in number between species to give great diversity in body types. Arthropods have an exoskeleton made principally of chitin—a waterproof, tough polysaccharide composed of N-acetylglucosamine. Phylum Arthropoda Phylum Arthropoda has 80% of animal species! For comparison, refer to the approximate numbers of species in the phyla listed on the table to the right. I highlighted the mollusks, arthropods and chordates (the phyla that humans are in) because these three phyla have the most species, but note that there are more than ten times more arthropod species than chordate species. You will see later that more than ½ of all eukaryotes are insects! Phylum Arthropoda Insects, with 900,000 species, form the single largest class within the Arthropoda. Phylum Arthropoda: Morphology Characteristic features of the arthropods include jointed appendages body segmentation chitinized exoskeleton. Fruit fly larva and amphipod showing The exoskeleton of a cicada, The two types of segmentation after molting. segmented legs seen in Phylum Arthropoda: Morphology The arthropod body The central cavity is called the hemocoel. The analogue of blood is called hemolymph and it is moved by contraction of regions of the tubular dorsal blood vessel called "hearts." They have an open circulatory system, which means there are no blood vessels and the hemolymph bathes the cells. There is a simple brain of two to three fused ganglia and there are ganglia in each segment. There are various excretory systems that get rid of nitrogenous waste and regulate salt concentration, including Malpighian tubules in insects. Phylum Arthropoda: Morphology Arthropods have respiratory systems for exchanging oxygen and carbon dioxide. Insects and myriapods use a series of tubes (tracheae) that branch through the body, ending in minute tracheoles. Aquatic crustaceans utilize gills. Terrestrial chelicerates (ex. spiders) employ book lungs. Arthropod respiratory structures. The book lungs of (a) arachnids are made up of alternating air pockets and hemocoel tissue shaped like a stack of books. The book gills of (b) crustaceans are similar to book lungs but are external so that gas exchange can occur with the surrounding water. (credit a: modification of work by Ryan Wilson based on original work by John Henry Comstock; credit b: modification of work by Angel Schatz) Phylum Arthropoda: Morphology The cuticle is the hard “covering” of an arthropod. The exoskeleton is very protective (it is sometimes difficult to squish a big beetle!), but does not sacrifice flexibility or mobility. It is primarily made of chitin but marine arthropods, such as lobster, add calcium salts to their exoskeleton to increase the strength. In order to grow, the arthropod must “shed” the exoskeleton during the physiological process called molting, following by the actual stripping of the outer cuticle, called ecdysis (“to strip off”). Larval, juvenile and adult forms molt, depending on the species. A dragon fly Carpenter’s coming out of its bee Exoskeleton – some pros and cons Pros Protects vulnerable body Place for muscles to attach Allowed these organisms to move on land without drying out Cons Organisms can only grow as big as their exoskeleton Molting is very “expensive” Recently molted arthropods are vulnerable until their new shell hardens. Phylum Arthropoda: Subphyla Phylum Arthropoda includes animals that have been successful in colonizing terrestrial, aquatic, and aerial habitats. This phylum is further classified into five subphyla: Trilobita (trilobites, all extinct) Hexapoda (insects and their six-legged relatives). Myriapoda (millipedes, centipedes, and their relatives) Crustacea (crabs, lobsters, crayfish, isopods, barnacles, and some zooplankton) Chelicerata (horseshoe crabs, spiders, scorpions, ticks, mites, and daddy longlegs or harvestmen) Subphylum Hexapoda The name Hexapoda describes the presence of six legs (three pairs) in these animals, which differentiates them from other groups of arthropods that have different numbers of legs (for example, spiders have eight). Hexapod bodies are organized into a head, thorax, and abdomen. This group includes the class Insecta, and a few smaller classes of wingless six legged arthropods. The insects comprise the largest class of arthropods in terms of species diversity as well as in terms of biomass— at least in terrestrial habitats, and we will focus on them. Individual segments of the head have mouthparts, and the thorax has three pairs of jointed appendages, and most insects have wings. Subphylum Hexapoda Many of the common ‘bugs’ we encounter on a daily basis— including ants, beetles, cockroaches, butterflies, crickets and flies—are examples of insects. Subphylum Hexapoda We have already discussed how 80% of all animals are arthropods and the insects are the largest class of arthropods. In fact, over 50% of all eukaryotic species are insects! Subphylum Hexapoda: Anatomy In this basic anatomy of a hexapod insect, note that insects have a developed digestive system (yellow), a respiratory system (blue), a circulatory system (red), and a nervous system (red). Subphylum Hexapoda Male dragonfly, Potamarcha congener White-lined sphinx moth The evolution of wings is an unsolved mystery. Unlike vertebrates, whose “wings” are simply adaptations of “arms” that served as the structural foundations for the evolution of functional wings (this has occurred independently in pterosaurs, dinosaurs [birds], and bats), the evolution of wings in insects is a what we call a de novo (new) development that has given them domination over the Earth. Winged insects existed over 425 million years ago, and by the Carboniferous, several orders of winged insects, most of which are now extinct, had evolved. In addition to flight, wings are used for thermoregulation, camouflage and communication. Signal to predators that they are poisonous, or at least look like a species that is poisonous. Attract mates. Subphylum Hexapoda An example of incomplete metamorphosis An example of complete metamorphosis Nearly all insects hatch from eggs. Insect growth is constrained by the exoskeleton and development involves a series of molts. Insects hatch as an immature form that goes through metamorphosis to produced the adult. Ants, beetles, flies, and butterflies develop by complete metamorphosis Egg>larva>pupae>adult Cockroaches and crickets develop through a gradual or incomplete metamorphosis from wingless immatures called nymphs. Egg>nymph>adult Growth occurs during the juvenile stages. Subphylum Hexapoda Some insects, especially termites, ants, bees, and wasps, are social, meaning that they live in large groups with individuals assigned to specific roles or castes, like queen, drone, and worker. Social insects use pheromones—external chemical signals—to communicate and maintain group structure as well as a cohesive colony. Subphylum Hexapoda: Ecology Humans often think of insects as pests, largely because some are agricultural pests or help themselves to our food supplies, but insects play critical ecological roles, such as soil turning and aeration, dung burial, pest control, pollination and wildlife nutrition. Without insects.... who would decompose our dead organisms? Without insects.... We would be buried in dung Without insects.... We would be without insect-produced products like silk, honey, and wax wa Silk x hone dress Without insects.... who could pollinate our crops? About one third of all food is produced as a result of insect pollination, and the European honeybee, Apis mellifera, is responsible for about 80% of this. Without insects.... The food chain would collapse, and people would probably disappear Subphylum Hexapoda: Fruit flies are a Model Organism Drosophila melanogaster, a fruit fly species is an important model organism for understanding genetics and cell biology in animals. They are easy to grow in the lab, have large numbers of offspring, have just four pairs of D. Melanogaster chromosomes, and easily identifiable traits. The Nobel Prize in Physiology or Medicine for 1995 was awarded for discoveries made using concerning “the genetic control of early embryonic development” that applies to all animals, including humans! These discoveries included the Hox genes! Subphylum Myriapoda (a) The Scutigera coleoptrata centipede has up to 15 pairs of legs. (b) This North American millipede (Narceus americanus) bears many legs, although not a thousand, as its name might suggest. (credit a: modification of work by Bruce Marlin; credit b: modification of work by Cory Zanker) Subphylum Myriapoda members have numerous legs. typically varies from 10 to 750. 16,000 species Four classes, the two most familiar are Chilopods – centipedes (1 set of legs per segment) are carnivores Diplopoda – millipedes (2 sets of legs per segment) are herbivores Virtually all are terrestrial. found in moist soils, decaying biological material, and leaf litter. Ancient myriapods (or myriapod-like arthropods) from the Silurian to the Devonian grew up to 10 feet in length (three meters). Unfortunately, they are all extinct! Subphylum Crustacea The (a) crab and (b) shrimp krill are both crustaceans. (credit a: modification of work by William Warby; credit b: modification of work by Jon Sullivan) Crustaceans are the most common aquatic (both freshwater and marine) arthropods. Krill, shrimp, lobsters, crabs, barnacles and crayfish are examples of crustaceans. about 70,000 species. More than 7.9 million tons of crustaceans per year are produced by fishery or farming for human consumption, mainly shrimp and prawns. There are a few terrestrial species One example is pill bugs (also known as roly-polies) Subphylum Crustacea: Anatomy Crustaceans are segmented, and each segment is differentiated to have a different morphology and appendages which results in the great diversity of crustaceans. Segments may have antennae, mandibles, compound eyes, claws, legs etc. Subphylum Crustacea: Anatomy Two branches Arthropods may have (a) biramous (two- branched) appendages or (b) uniramous (one-branched) appendages. (credit b: modification of work by Nicholas W. Beeson) Crustaceans have biramous (“two branched”) appendages Since biramous appendages are also seen in the trilobites, biramous appendages are thought to be the ancestral condition in the arthropods. Subphylum Crustacea: Anatomy The crayfish is an example of a crustacean. It has a carapace around the cephalothorax and the heart in the dorsal thorax area. (credit: Jane Whitney) The head and thorax is fused to form a tagma called a cephalothorax covered by a plate called the carapace, thus producing a body plan comprising the cephalothorax and abdomen (see the figure above). The chitinous exoskeleton is shed by molting and ecdysis whenever the animal requires an increase in size or next stage of development. The exoskeletons of aquatic species may also infused with calcium carbonate, which makes them even stronger than those of other arthropods. Subphylum Crustacea: Anatomy The crayfish is an example of a crustacean. It has a carapace around the cephalothorax and the heart in the dorsal thorax area. (credit: Jane Whitney) Crustaceans shave an open circulatory system where hemolymph (arthropod blood) is pumped into the hemocoel (body cavity) by the dorsally located heart (see above). In most species, hemocyanin is the protein that carries oxygen to the cells. Unlike hemoglobin, it is blue, not red when oxygenated! So crustaceans have ”blue blood”! Subphylum Crustacea: Ecology Crustacea live in marine, freshwater or moist terrestrial environments. Most crustaceans are carnivores some species are herbivores, filter feeders detrivores or parasites. Crustaceans may also be cannibalistic when overpopulated! Copepods and krill play a critical role in marine food chains and biogeochemical cycles. Copepods are tiny, about 1- 2 millimeters (mm) long and are found in nearly every fresh and marine habitat. They eat phytoplankton (marine algae) and are themselves planktonic (drifting in water) species are a critical food source for small fish and krill and A copepod are a fundamental step in the food chain. Krill are small – 1 -2 centimeters long, and are found in all the world’s oceans. They feed on phytoplankton and copepods and convert the energy in their prey into a form suitable for consumption by larger animals. Krill are the main food source of baleen whales, for example the blue whale. A Northern krill (Meganyctiphanes norvegica).  Ocean acidification threatens crustaceans, which are indicator species for marine environments Crustaceans need calcium carbonate (CaCO3) in the ocean for their shells. CO 2 Humans are causing increasing carbon dioxide (CO2) + CaC = bad for CO2 reacts with the CaCO3 in the ocean O3 Sebastian 1. This makes CaCO3 unavailable for crustaceans 2. The CO2 in the ocean makes water acidic, which dissolves crustacean exoskeleton Anthropogenic ocean acidification over the 21st century and its impact on calcifying organisms. Nature (2005) Subphylum Chelicerata Pronounced ‘key-liss-er-ah-ta’ Atlantic horseshoe crab (Limulus polyphemus) Wall spider (Dictyna civica) Tick (Ixodes hexagonus) Black Scorpion (Androctonus crassicauda) The phylum derives its name from the first pair of appendages: the chelicerae, which serve as specialized claw like or fanglike pinching mouthparts. See the red arrows on the photos. Do not have antennae. Includes horseshoe crabs, spiders, mites, ticks, and scorpions. ~77,000 species! Found in almost all terrestrial habitats. Few aquatic species exist (one exception being horseshoe crabs). The body of chelicerates is divided into two tagmata, giving a head/thorax and an abdomen. Animal Phylogenetic Tree Deuterostomes Two phyla Echinoderms Chordates Superphylum Deuterostomia The Superphylum Deuterostomia has two phyla, the Echinodermata and Chordata (which includes humans). Deuterostomes differ from the Lophotrochozoans (which were protostomes) in their embryonic development. Protostomes (mouth first) develop the mouth from the blastopore, the opening that forms the primitive gut. Deuterostomes (mouth second) develop the anus from the blastopore. Whereas most protostomes have spiral cleavage in the embryo, deuterostomes exhibit radial regulative cleavage. The way the coelom forms in deuterostomes is different too. The endodermal lining of the archenteron forms buds called coelomic pouches that expand to form the coelom. Cleavage in most deuterostomes is also indeterminant, meaning that the developmental fates of early Animal Phylogenetic Tree Domain: Eukarya Kingdom: Animalia Super phylum: Deuterostomia Phylum: Echinodermata Echinodermata (echinoderms) Phylum Echinodermata Pronounced ‘ee-kine-oh-derm-ah-ta Different members of Echinodermata include the (a) sea star of class Asteroidea, (b) the brittle star of class Ophiuroidea, (c) the sea urchins of class Echinoidea, (d) the sea lilies belonging to class Crinoidea, and (e) sea cucumbers, representing class Holothuroidea. (credit a: modification of work by Adrian Pingstone; credit b: modification of work by Joshua Ganderson; credit c: modification of work by Samuel Chow; credit d: modification of work by Sarah Depper; credit e: modification of work by Ed Bierman) Echinodermata or echinoderms are named after their “prickly skin” (from the Greek “echinos” meaning “prickly” and “dermos” meaning “skin”). ~ 7,000 described living species exclusively marine, bottom-dwelling organisms. Sea stars, sea cucumbers, sea urchins, sand dollars, and brittle stars are all examples of echinoderms. Phylum Echinodermata: Morphology and Anatomy Endoskeleton The spines of a sea urchin showing of a sea pentamerous radial symmetry. urchin. Echinoderms evolved from animals that have bilateral symmetry, and their larva have bilateral symmetry, however adults have pentaradial symmetry (with “arms” typically arrayed in multiples of five around a central axis). Echinoderms have an endoskeleton made of small bony plates covered by the epidermis. For this reason, it is an endoskeleton like our own, not an exoskeleton like that of arthropods. The spines for which the echinoderms are named are connected to some of the plates. The spines may be moved by small muscles, but they can also be locked into place for defense. Phylum Echinodermata: Water Vascular System The underside of a sea star, showing the tube feet. The water vascular system moves the tube feet, which allow the sea star to move. Echinoderms possess a unique water vascular system. This is a network of fluid-filled canals derived from the coelom that is essentially an hydraulic system that controls the animals physiology and movement. Functions in gas exchange, feeding, sensory reception and locomotion. Movement uses ‘tube feet’. Watch this cool video: Sea star tube feet. And this one too! Starfish walks on the beach. Phylum Echinodermata: Morphology and Anatomy A sun starfish regenerating lost arms. The nervous system is simple. There is a nerve ring in the center and five radial nerves extending outward along the arms. In contrast to the greater degree of cephalization we have been seeing, there is no head or ganglia similar to a brain. Most echinoderms are diecious, and they can also reproduce asexually by fragmentation. A piece of an arm can grow to a new individual. Echinoderms also have a great ability to regenerate if damaged. (See the picture above). The stomach of some species of sea start can evert itself and digest its prey outside of their bodies! Sea star eating mussels. (time lapse video) Phylum Echinodermata: Ecology Crown of thorns Sea otter eating starfish preys a sea urchin. on coral polyps. Nutritional modes differ between the different classes and species. Many sea urchins are herbivores, eating sea weed from rocks. Sea stars are carnivores or detrivores Echinoderms are predated on by (and provide nutrition for) cephalopods, sea otters and other species. Echinoderms sometimes have large population swings which can cause marked consequences for ecosystems. On the Great Barrier Reef, an increase in the numbers of crown-of-thorns starfish (Acanthaster planci), which graze on living coral tissue, has had considerable impact on coral mortality and coral reef biodiversity. Sea urchins are among the main herbivores on reefs and there is usually a fine balance between the urchins and the kelp and other algae on which they graze. A loss of sea urchins can lead to algae choking off coral reefs. Decrease in predation of sea urchins can lead to overgrazing and creation of urchin barrens. Animal Phylogenetic Tree Domain: Eukarya Kingdom: Animalia Super phylum: Deuterostomia Phylum: Chordata Chordata (Chordat es) Phylum Chordata Pronounced ‘cord-ah-ta’. Includes humans and other vertebrates, and some rather humble invertebrate species. All chordates possess the following characteristics at some point during their life cycle. Dorsal hollow nerve cord Notochord Post anal tail Pharyngeal gill slits Some of these traits might only be present during embryological development. Animals are segmented internally. Download for free at http://cnx.org/contents/[email protected] Phylum Chordata There are three subphyla: Subphylum Urochordata – invertebrates Subphylum Cephalochordata – invertebrates Subphylum Vertebrata  Phylum Chordata: Urochordata or Tunicata Commonly called ‘sea squirts’. The subphylum is called either Urochordata or Tunicata Marine filter feeders with a sac-like body structure and two tubular openings, called siphons, through which they draw in and expel water. Larvae resembles tadpole Adults are sessile Clavelina moluccensis, Fluorescent-colored sea the bluebell tunicate. squirts, Rhopalaea crassa Phylum Chordata: Subphylum Cephalochordata Commonly called lancelets or amphioxus. Small marine filter feeders, often bury in the bottom of the ocean. They are unique among the chordates in that the adults have all four chordate characteristics and segmentation is visible on the outside of the body. Branchiostoma lanceolatum And this concludes this lengthy PowerPoint, which is actually just a superficial introduction to the diversity and characteristics of the invertebrates! Next time, you will learn about the Chordates Subphylum Vertebrata – vertebrates, which include us! The End