Chapter_33_notes.docx

Chapter 33, Protosome animals Protostome animals Introduction Over 20 phyla protostomes Phyla: Kinorhyncha (mud dragons) 150 species Phyla: Gnathostomulida 80 species Gastrotricha 450 species 33.1 ? An Overview of protostome Evolution Two major groups of Bilateral symmetric, triploblastic coelomate animals Protostomes Deuterostomes When gastrulation occurs protostomes, initial pore is a mouth while during embryo stage Mouth forms second within blocks of mesodermal tissue Phylogenetic studies support protostomes are monophyletic group Protostome developmental sequence arose just once Two monophyletic groups: protostomes Lophotrochozoa Ecdysozoa ~What is a Lophotrochozoan?~ They grow continuously and incrementally 13 phyla of lophotrochozoan Morphological traits found in some Morphological traits are: Feeding structure: Lophophore (tuft-bearer); found in three phyla Larva called trochophore, common to many phyla lineages Lophophore ? Tuft-bearer, specialized structure that?s rings the mouth and functions in suspension feeding Lophophore found in: Bryozoans (moss animals) Brachiopods (lamp shells) Phoronoids (Horseshoe worms) Trochophores Type of larvae common to Marine mollusks Annelids that live in the ocean Several phyla in lophotrochozoa Cilia on trochophores are used for Swimming Some species; sweep food particles into mouth Trophophore originated early in evolution lophotrochozoans, Later different types larval types evolved in some groups Trochophore ? wheel-bearer, larva has ring of cilia around its middle Neither lophophores nor trochophores qualify as synapmorphy in lophotrochozoa Scientist still looking for morphological synapomorphy that distinguishes it from the other protostomes ~What is an Ecdysozoan?~ Defined by, or their synapomorphy, is their method of growth by molting Molting ? shedding exoskeleton or external covering (E.G. insectas, arachnids) 2 most common ecdysozoan out of 7 are the Nematoda (worms) Antropods (arthropoda) Cuticle ? individual outer layer Exoskeleton ? like a cuticle, but the outer layer is hard Molting required once ecdysozoans evolved tough outer cuticles or thick exoskeletons With the cuticle or exoskeleton, it was advantageous, since it gave the organism structure, and protection While organisms are molting they are at a disadvantage, since they soft after just molting 33.2 ? Themes in the Diversification of Protostomes Protostomes diverged into more than 22 phyla, distinguished by body plans, or specialized in feeding ~How Do body plans vary among Phyla?~ All Protostomes are Triploblastic Bilaterally symmetric Most protostome phyla have wormlike bodies (aka ? Tube within a tube design) (E.G.) Ectoderm ? skin Endoderm ? guts Mesoderm ? muscle Worm like phyla Coelom well developed and functions as hydrostatic skeleton, which is basis of movement Coelom absent in flatworms in most species rich and morphologically complex protostome phyla (E.G. Arthropoda and Mollusca) it is drastically reduced fully function coelom two roles: providing space for fluids to circulate among organs providing hydrostatic skeleton for movement different in arthropods and mollusks; structures are replaced by other structures ~The Arthropod Body Plan~ Arthropods have segmented bodies; organized into prominent regions called tagmata Arthropods distinguished by Jointed limbs, exoskeleton (which is made primarily of polysaccharide chitin) Crustaceans exoskeleton strengthened by Calcium carbonate Instead of being based on muscle contraction against hydroskeleton, arthropod locomotion based on muscles that apply force against the exoskeleton to move legs or wings Hemocoel? blood-hollow ? spacious body cavity that provides space for internal organs and circulation of fluids Hemocoel functions as hydrostatic skeleton in caterpillars and other types of arthropods larva ~The Molluscan Body Plan~ Body plan mollusks based on three major components Foot Visceral mass Mantle Foot ? large muscle located at the base of the animal usually used in movement Visceral Mass ? the region containing most of the main internal organs Mantle ? an outgrowth of the body wall that covers the visceral mass, forming an enclosure called the mantle cavity In all mollusks visceral mass provides space for organs and the circulation of fluids Some species the fluid enclosed by visceral mass also functions in movement as hydrostatic skeleton Many species the mantle secretes shell made of calcium carbonate Some mollusk species have different layers of shells ~Variation Among Body Plans of the Wormlike Phyla~ Most cases wormlike lineages are distinguished by specialized mouthparts or feeding structures Annelids (segmented worms) Echiurans, which are another type of worm Deposit feed using extended structure ? Proboscis Proboscis ? forms a gutter leading to the mouth Cells in the gutter secrete mucus, which is sticky enough to capture pieces of detritus Then the mucus and detritus swept into mouth by cilia Priapulids (penis worms) Burrow into substrate Sit and weight predators When feeding (E.G. polychaete which is annelid), when the prey approaches; it turns its? throat inside out, and grabs the prey item with teeth that is lined on the wall of the throat, then it retracts it back Nemerteans (ribbon worms) Active predators move around ocean flood searching for food Uses proboscis to capture prey To spear Wrap prey They can extend and retract the proboscis Once a specific body plan had evolved, subsequent diversification was largely driven by adaptations that allowed protostomes to Live on land or feed move or reproduce in novel ways Adaptation ? trait that increases the fitness (reproductive success) ~The Water to land transistion~ Protostomes most abundant animals in the surface water and substrates of many marine and fresh water environments Green plants move from freshwater to land just once ~Evidence for multiple transitions~ The evidence for multiple water-to-land transitions in protostomes based on phylogenetic analyses, which supports hypothesis that ancestors of terrestrial lineages in each major subgroup of protostomes were aquatic ~Adaptations to terrestrial environments~ Easier for animals to move onto land, than plants Plants evolved roots and vascular tissue to transport nutrients While, animals needed to support their own body weight on land, and move about Protostome groups made the transition already had one of the following, or even a few, for support and locomotion Hydrostatic skeletons Exoskeleton Appendages Or other adaptations To make the transition to land, new adaptations allowed protostomes to Exchange gases Avoid drying out Biggest challenge for these organisms was not to dry out How do terrestrial protostomes solve this problem? Roundworms and earthworms live in humid soils, or moist environments and exchange gases across their body surface. High surface-area-to-volume ratio; which in turn increases the efficiency of gas exchange Arthropods and many mollusks have gills or other respiratory structures located inside the body, this resulted in minimal water loss when certain groups moved onto land Mollusks, the mantle cavity encloses the gills of aquatic snails evolved into the lung found in terrestrial snails Insects evolved a waxy layer to minimize water loss from body surface, with openings to respiratory passages that can be closed if environment dries Unlike plants, land animals can move to moister habitats if area they are occupying gets too dry Water-to-land transitions are important because they open up entirely new habitats and new types of resources to exploit Key event in diversification ~Adaptations for Feeding~ Protostomes feeders Suspension Deposit Liquid Food-mass Protostomes have different mouths, which help them feed on a diversity of foods Diversity feeding of insects is more vast than anything else Arthropods use jointed limbs to control how they eat, and efficiently eat their food (E.G.) insects, crustaceans, spider, and mollusks use appendages capture prey or hold food while eating it Metamorphosis extremely common in protostomes and usually results in larvae and adults that live in different habitats and have different overall morphology and mouth parts ~Adaptations for Moving~ Aquatic larvae move with aid of cilia Wormlike protostomes that lack limbs move with aid of coelom that functions as hydrostatic skeleton Using their body?s? to sway back and forth Wormlike bodies have an enclosed, fluid-filled body cavity, aka hemocoel; also functions as hydrostatic skeleton Caterpillars Grubs Maggots Other types of insect larvae As arthropods diversified, however, number important evolutionary innovations allowed them to move in unique ways Jointed limbs in arthropods help (rapid movement of): Precise walking Running Jumping movements Insect wing One of the most important adaptations in history of life 2/3 of multicellular species living today are winged insects In many cases, only adult have wings Data in fossil record show insects were the first organisms to have wings and fly Earliest insects had two pairs Some today have four, but only function as if it were two Butterflies Moths Bees Wasps Beetles fly with only their hind wings Flies have single pair that power flight Also have halteres which provide stability during flight The mollusks foot Snails and chitons are mollusks that have muscular foot at base of body Waves of muscle contractions sweep up or down the length of the large, muscular foot, which allows them to crawl along surface Cells in foot secrete lay of mucus, this helps Reduce friction Efficiency of movement Jet propulsion Cephalopods (squid and octopus) are mollusks that have a mantle lined with muscle Siphon ? when the cavity surrounded by the mantle fills with water and the mantle muscles contract a stream of water is force out of a tube Force of the water propels the squid ~Adaptations in Reproduction~ Protostome have many variation of reproduction and life cycles Asexual reproduction ? splitting one?s body, or fragmenting Common in many wormlike phyla Many crustacean and insect species reproduce asexually via parthenogenesis Parthenogensis ? virgin-origin ? production of unfertilized eggs, by mitosis, that devlop into offspring Sexual reproduction often based on external fertilization, happens in Clams Bryozoans Brachiopods And other groups Sexual reproduction begins with copulation (aka sexual intercourse) and internal fertilization in groups that are able to move around Because males can meet females, so it is convenient Females of ovoviviparous (bear live young; eggs are internal and hatch internally, but then come out) insects and snails Retaining fully formed eggs, inside their bodies and then they are nourished by nutrient rich yolk inside the egg Sexual reproduction predominant mode of reproduction in protostomes groups Metamorphosis is important aspect of reproduction in protostome groups, as well Marine species Hypothesized ? metamorphosis is an adaptation, because larvae can disperse into new habitats by floating or swimming in the plankton, where they can feed on these food sources until they are an adult This helps reduce competition for food between larvae and adults Pupal stage in insects ? when larval body is remodeled into adult ? does not occur in marine species Most critical adaption transition from aquatic to land life is retaining moisture in the egg (or desiccation-resistant eggs) Insects eggs Thick membrane keeps moisture in Slug eggs Thin calcium carbonate shell helps retain water 33.3 ? Key Lineages: Lophotrochozoans Lineages within lophotrochozoa united by shared mechanisms of early development and growth Highly diverse in terms of morphology Lophotrochozoan: four key phyla Rotifer Platyhelminthes Annelid Mollusca Bivalves (clams and mussels) Suspension feeder (the other three sub-phyla are either herbivores or predators) Gastropods (slugs and snails) Chitons, or Polyplacophora Cephalopods (squid and octopuses) coelom much reduced, and functions only in reproduction excretion of wastes Lophotrochozoans > Rotifera (Rotifers) Intro Have coelom Most are >1 mm long Do not have Lophophore (structure only) Trochophore (larval stage only) Extensive similarities DNA put them into lophotrochozoans Feedings Corona ? cluster of cilia at rotifers anterior end Beating of cilia helps sweep food into mouth to feed Corona is the signature morphological feature in this group (Synapomorphy??) Movement Few sessile Most beat cilia in the corona to move around Reproduction Females produce unfertilized eggs by mitosis Eggs then hatch into new asexually produced individuals Parthenogenesis ? production of offspring via unfertilized eggs In a group of rotifers called bdelloids, only females been found and all reproduction appears to be by parthenogenesis Sexual and asexual Development is direct, no metamorphosis taking place at any point in its life Lophotrochozoans > Platyhelminthes (flatworms) Intro More than 400,000 species in four major lineages within phylum Free-living species called Turbellaria Endoparasitic tapeworms called cestoda Endoparasitic or ectoparasitic flukes called trematoda Ectoparasites called monogenea Few turbellarian species are terrestrial, most live on substrates of freshwater of marine environments Tapeworms, and cestodes parasitize Fish Mammals Other vertebrates Flukes parasitize Vertebrates Mollusks In humans, they are responsible for schistosomiasis (serious public health issue in many developing nations Monogeneans parasitize Fish Flatworms, or Platyhelminth Unsegmented bodies Lack coelom Lack structures that specialized for gas exchange Instead happens through body wall Lack blood vessels for circulating oxygen and nutrients to cells Flattened body is adaptation High surface to volume ratio Need moist areas in order to survive, and for gas to be exchanged Feeding Lack lophophore Blind digestive tract Only one opening for ingestion of food and elimination of waste (?only one way in, and one way out?) Most turbellarians are hunters that prey on protists or small animal Other scavenge dead animals Tapeworms Strictly parasitic Feed on nutrients provided by hosts Do not have a mouth or digestive tract Obtain nutrients through their body wall Flukes Parasites Feed by gulping host tissues and fluids through mouth Blind digestive tract Movement Most don?t move much Turbellarians swim by undulating bodies Most can creep along substrates with the aid of cilia on their ventral surface Adult cestodes have hooked attachment structures at their anterior end that permanently attach them to the interior of their host Flukes move very little Reproduction Turbellarians reproduce asexually By splitting themselves in half If attacked by a predator and a limb is torn off the body part can regenerate Hermaphrodite Body parts line up within, and they DO IT! In Flukes and tapeworms reproduction is similar to turbellarians Individuals reproduce sexually, either Cross-fertilize Self-fertilize Life cycles are complex Involves two or even three distinct hosts species, with sexual reproduction happening in the definitive host Humans are definitive host for the blood fluke ? Schistosoma Mansoni Fertilized eggs are passed along with hosts feces, and enters a aquatic environment if sanitation systems are poor Eggs develop into larvae that infect snails, which they then start to asexually reproduce Then it emerges and goes back into the waters If humans are wading in infested waters, chances of being infected are high And asexual reproduction occurring in one or more intermediate hosts Lophotrochozoans > Annelida (segmented worms) Intro Segmented bodies with a coelom that function as hydrostatic skeleton 16,500 species, put into two groups Polychaeta paraphyletic Clitellata The following is consistent with annelid phylogeny Common ancestor of annelids had key synapomorphy in addition to segmentation called chaetae Chaetae ? numerous, bristle like extensions, which extend from appendages called parapodia Lineages that retained many chaetae are mostly marine Size can range from less than 1 mm long to 3.5 m Large number of burrowers in mud or sand Chaetae reduced or lost in a lineage called clitellata Clitellata include monophyletic groups called the Oligochaetes and leeches or oligochaeta and hirudinea Oligochaetes (Oligo ? few, chaetes ? bristles) include: Earthworms are included in this category Burrows into moise soils Array of freshwater species Few marine forms Fewer chaetae than polychaetes Leeches Coelom much smaller than other annelids Consists o series of connected chabers Live in fresh water as well as marine Lineage called sipunculida (peanut worms) and Echiura (spoon worms) Segmentation and chaetae were lost in these species Thought to be its own phyla, but belongs to annelids Feeding Wide variety of methods Burrowing, which involves mucous-lined nets Deposit feeding Suspension feed Capture food by Using dense crown of tentacles Everting their throats Most oligochaetes make their living by deposit feeding in soils Tunnels made are critically important in aerating soil Feces contribute large amounts of organic matter Leeches Ectoparasites; attach themselves to another organism and live off of them Saliva typically contains anesthetic Has anti-coagulant Used by physicians to reduce swelling Predators or scavengers Movement Polychaetes and oligochaetes crawl or burrow with help from hydrostatic skeleton Parapodia of polychaetes act as paddles or tiny feed aid in movement Any polychaetes are great swimmers Reproduction Asexual reproduction occurs in polychaetes and oligochaetes by transverse fission or fragmentation Body parts can regenerate a complete individual Sexual reproduction in polychaetes may begin internal or external fertilization, depending on the species Most lineages off of polychaetes have seperate sexes Usually release eggs directly into water some species produce eggs that hatch into trochophore larvae, then develop into more complex forms in oligochaetes and leeches individuals produce both sperm and eggs engage in mutual internal cross-fertilization eggs enclosed in mucus-rich cocoon-like structure after fertilization, offspring develop into a mini-adult Lophotrochozoans > Mollusca > Bivalvia (clams, mussels, scallops, oysters) Intro Named bivalves because two separate shells made of calcium carbonate secreted by mantle Shells hinged, and open and close with help of muscle When shell is closed it helps protect the mantle, visceral mass, and foot Bivalve shell is adaptation to reduce predators Most bivalves live in oceans, but some live in fresh water too Clams burrow into mud, sand, or other soft substrates and are sedentary as adults oysters and mussels largely sessile as adults most live above the substrate attached to rocks or other solid surfaces scallops are mobile have eyes live on surface of soft substrates All bivalves can sense gravity, touch, and sense certain chemicals Most bivalves live under a substrate, so when they die, they are buried Since they can do this, this allows them to be fossilized Bivalve lineages has most extensive fossil record of any animal, plant, or fungal group Feeding Most bivalves are suspension feeders Take in any type of Small animal Protists Detritus Suspension feeding is based on flow of water across gas-exchange structures Gills ? Gas exchange structure Gills lie in mantle cavity, between mantle and visceral mass Consist of a series of thin membranes where particles are trapped Many cases, water current flows through siphons, which are tubes formed by edges of the mantle Siphons water into the gills and then back out of the body, powered by beating cilia on the gills Bivalves are the only major group of mollusks that lack the feeding structure called radula Filter feeding is important for all bivalves, and the ecosystem they live in, they can either Kill off a population Or let the water quality over time reduce itself from all the debris that the filter feeders to be feeding on Movement Clams Burrow with aid of muscular foot, otherwise sedentary Scallops Swim by clapping their shell together and forcing water to jet out Locomotion similar to the swimming of cnidarians medusa Which move when muscular contractions force water out of their bell Bivalves produce a swimming trochophore larva that is responsible for dispersing individuals to new locations Reproduction Most bivalves reproduce sexually Eggs and sperm thrown into the water Which develop into trochophore larvae That develops by metamorphosis into a veliger Continues to feed and swim before settling to the substrate and metamorphosing into an adult form that secretes a shell Lophotrochozoans > Mollusca > Gastropoda (snails, slugs, nudibranchs) about 70,000 known Intro Gastropods ? ?belly feet? Large muscular foot on their ventral side Snails Retract into shell when in danger When their tissues start to dry out Land slugs and nudibranchs lack shells Lack of shell was lost individually Other ways of defending themselves Poison The bright colors nudibranchs exhibit are a sign that they are poisonous Gross tasting Feeding Gastropods and other mollusks have radula Radula ? functions like a rasp to scrape away algae, plant cells, or other types of food. Usually covered with teeth that are made of chitin and wary in size and shape among species Most gastropods are herbivores or detritivores Specialized teeth help them act as predators (some) Species called drills Use radula to bore hole in shell of oyster or other mollusks and expose visceral mass, which they eat Cone snails have highly modified, harpoon like ?teeth? mounted at tip of extensible proboscis and armed with poison Movement Waves of contractions down the length of the foot allow gastropods to move by creeping Sea butterflies Gastropod With reduced or absent shell but large wing like foot that helps them swim Reproduction Females of some gastropods can asexually reproduce by producing eggs parthenogenetically Most reproduce sexually Sexual reproduction in some gastropods begins with internal fertilization Marine gastropods produce veliger larva that may disperse up to several hundred km away from parent Some marine, but all terrestrial forms ? larvae are not free living They are in egg form for several stages, until they hatch as miniature adults Lophotrochozoans > Mollusca > Polyplacophora (chitons) Intro Polyplacophora ? ?many-plate-bearing? Name is apt, chitons have eight calcium carbonate plates along their dorsal side Form a protective shell Approximately 1000 species of chitons are marine Found usually where rocks are exposed to air at low tide Feeding Have radula and use to scrape algae and other organic matter off rocs Movement Same as gastropods Reproduction Most are separated by sex External fertilization Sperm shed in water enter female?s mantle cavity and fertilize eggs inside the body Depending on species involved, eggs may be enclosed in membrane and released or retained until hatching and early development are complete Most species have trochophore larvae Lophotrochozoans > Mollusca > Cephalopoda (Nautilus, cuttlefish, squid, octopuses Intro Cephalopods ? head-foot Well-developed head consisting of visceral mass and foot that is modified to form tentacles Tentacles ? long, think muscular extensions that aid in movement and prey capture Except nautilus Extant, have either highly reduced shells or none at all Most have large brains and image-forming eyes with sophisticated lenses Feeding Highly intelligent creatures, hunt with Sight, and tentacles Have radula, and a beak Some octopuses and cuttlefish inject poisons to subdue victims Movement Cephalopods swim by moving fins to ?fly? through water Jet propulsion Drawing water in, and forcing it out Squid Build for speed, and hunts small fish by chasing them down Octopuses Crawl along substrate using tentacles Chase down crabs or other crustaceans Pry open mussels or clams from the substrate Use beaks to crush exoskeletons of their prey Reproduction Separate sexes, some species have elaborate courtship rituals that involve color changes and interaction of tentacles Male sperm deposits called spermatophore Fertilization is internal Females lay eggs When hatched, they look like mini-adults 33.4 ? Key Lineages: Ecdysozoans First recognized as monophyletic when investigators began using DNA sequence data to estimate the phylogeny of protostomes Seven phyla recognized, including Nematode Onychophora Tardigrada Onychophora and Tardigrada not species rich phyla, but closely related to arthropods No jointed limbs No exoskeleton Onychophorans, aka velvet worms, are small, caterpillar like organisms that live in moist leaf litter and prey on small invertebrates Lope shaped appendages and segmented bodies with hemocoel Tardigrades, aka water bears Microscopic animals that live in benthic (bottom) habitats of marine or freshwater environments Can be found in film of water that covers moss or other land plants in moist habitats Have reduced coelom but have hemocoel Walk on clawed, lobe-shaped legs Most feed on sucking fluids from plants or animals Others are detritivores Notable for ability to withstand extreme drying and pressure Some can reduce metabolism to near zero for a decade or more, and resume when conditions are right Arthropods are most important phylum within Ecdysozoa Appeared in fossil records 520 mil years ago Most successful lineage of eukaryotes Distinguished by Segmented bodies Complex jointed exoskeleton Highly reduced coelom Extensive body cavity called hemocoel Body organized by Head Trunk tagmata (sometimes) thorax, or abdomen Metamorphosis common in anthropods Larvae have segmented bodies Lack hardened exoskeleton Larval and adult forms grow by molting Arthropod appendages used for Sensing aspects of environment Most have antennas Their sense of tough and smell Exchanging gases Feeding Locomotion via swimming Walking Running Jumping Flying Arthropods have sophisticated compound eye Compound Eye ? contains many lenses, each associated with a light sensing, columnar structure (humans have simple eyes, which is just one lens) Ecdysozoans > Neatoda (roundworms) Intro Roundworms or nematodes Unsegmented Coelom Tube-within-atube- No appendages Move by contracting, and relaxing opposite side to create a swaying motion Vary in size Lack specialized systems for exchanging gases and for circulating nutrients Gas exchange occurs across the body wall, and nutrients move by simple diffusion Not species rich, but most abundant Feeding Roundworms Feed wide variety materials including Bacteria Fungi Plant roots Small protest Small animals Detritus Feeding habits correlate to mouth part Different mouth parts correlate to different things they eat Movement Move with aid of hydrostatic skeleton Live in soil or host Push off of substrate in order to move (E.G. A worm wriggles around to move, but in order to move forward it has to push itself off a substrate to propel forward) Reproduction Sexual reproduction Internal fertilization and culminate in egg laying, with direct development of offspring Go through about 4 molts over course of life time Ecdysozoans > Anthropoda > Myriapods (Millipedes, Centipedes) Intro Has head region and long trunk Segmented body with one or two legs on each If eyes are present, it is clustered Feeding Mouth that can bite and chew Live in rotting logs, and other dead plant material that litters ground in forest or grassland Millipedes ? Detritivore Centipedes ? use pair of poison-containing fang just behind mouth to hunt array of insects Large centipedes can inject enough poison to weaken a person Movement Walk or run on many legs Some millipedes Over 190 trunk sections Two legs on each = ~750 legs Centipedes Fewer than 30 segments Pair of legs on each sement Reproduction Separate sexes Fertilization is internal Males make deposit sperm in packets that are picked up by female or transferred over. Ecdysozoans > Arthropoda > Insecta (insects) Intro Insects dominate terrestrial environments Larvae of some species are common in freshwater streams, ponds and lakes Legs found lateral surface of thorax Wings mounted on dorsal side of thorax Head contains Four mouthpart structures Pair of antennae Touch and smell pair of compound eyes Feeding Four mouthpart structure ? diversified in structure and function in response to natural selection Labrum Paird mandibles Paired maxillae Labium Feed on just about every imaginable food type on the planet Species with holometabolous metamorphosis Larvae have wormlike bodies Most tunnel their way through food sources Some feed by bitin leaves Adult insects are either Predators Parasites Feed on plant or animal tissue Diversification of insects is correlated to the diversity of plants Insect predators usually eat other insects Insect parasites usually victimize other arthropods or mammals Movement When walking or running, at least three of the six legs stay on the ground Reproduction Sexes are separated Mating takes place through direct copulation How humans do it Most females lay eggs Few retain eggs until hatched Many species capable of reproducing asexually, through the production of unfertilized eggs via mitosis Vast majority of species either Incomplete metamorphosis Complete metamorphosis (more common) Ecdysozoans > Anthropoda > Chelicerata (spiders, ticks, mites, horsehoe crabs, daddy longlegs, scorpion) Intro Most prominent lineage within Chelicerata is Arachnida Spiders Scorpions Mites Ticks Chelicerate body consists Anterior regions Lacks antennae for sensing touch or odor, bu usuall continas eyes Posterior regions Chelicerae ? feeding appendages at anterior end Chelicerae used for Feeding Defense Copulation Movement Sensory reception Chelicerates have totoal of 6 pairs of appendages Feeding Most spiders are sit and wait predators Create a web, and patiently wait for prey to fall into their web Spiders know by vibrations in the web Other species are active hunters Mites and ticks are ectoparasitic Use piercing mouthparts to feed on host animals Dust mites feast on dead skin Horseshoe crabs eat variety of animals as well as algae and detritus Most scorpions feed on insects; some bigger ones feed on bigger prey Movement Move with aid of muscles attached to exoskeleton Walk or crawl on four pairs of legs Some are capable of jumping Horseshoe crabs and other marine forms can swim slowly Newly hatched spiders spin long, silken threads and serve as balloons and can be carried far away Reproduction Fertilization is internal in most groups Courtship displays are extensive in many arthropod groups, may include Visual displays Release of chemical odorants Male spiders use pedipalps to transfer sperm to females Like a ?lock and key? Differences in size and shape of male genitalia are often the only way to identify closely related species of spider Development is direct Metamorphosis does not occur Spiders may catch a prey and give it to the female spider as a gift as they mate In some species the male is eaten as sperm is being transferred Scorpions Females retain fertilized eggs After eggs hatch, the young climb on mothers back Stay there until they are big enough to hunt for themselves Ecdysozoans > Arthropoda > Crustaceans (shrimp, lobster, crabs, barnacles, isopods, copepods) Intro Crustaceans primarily live in marine and freshwater environments Some are terrestrial (crabs and isopods) Sowbugs Pillbugs Roly-polies Important grazers and predators in shallow-water benthic environments Segmented bodies, divided into two distinct regions Cephalothorax Combines head and thorax Abdomen many crustaceans have a carapace carapace ? platelike section of their exoskeleton that covers and protects the cephalothorax only type of anthropod with two pairs of antennae also sometimes have sophisticated compound eye usually mounted on stalks crustaceans and trilobites (trilobites ? major lineage that did not survive the end-permian mass extinction, 250 myag first arthropods to appear in fossil record Feeding Most have 4-6 pairs mouthparts that derived from jointed appendages Use every type of feeding strategy known Barnacles and many shrimp Are suspension feeders that use feathery structures located on head or body appendages capture passing prey Crabs and lobsters Active hungers Herbivores Scavengers Typically have mandibles Mandibles ? pair of mouthparts used to bite and chew Capture and hold their food source with claws or other feeding appendages near mouth then; Use mandibles to shred food into small bits to be ingested Herbivores or detritivores, which are many species of crustaceans, depend on algae for food Movement Common for species to have more than on type of limb Crustacean limbs are highly diverse Paddle shaped ? used for swimming Feathery ? used in capturing food that is suspended in water Slender legs that make sophisticated walking or running movements possible Barnacles are one of the few types of sessile crustaceans Adult barnacles cement their heads to a rock or other hard substrate Secrete protective shell: calcium carbonate Use their legs to capture food particles Also use legs to transfer food into the mouth Reproduction Most individual are either male or female, and sexually reproduce normally Fertilization is internal Retained in female until hatched Most crustaceans pass through several distinct larval stages Many species have larval stage called nauplius, kind of planktonic Nauplius ? sing eye and appendages that develop into the two pairs of antennae, the mouthparts, and swimming legs of the adult