Phylum Echinodermata, Introduction to Phylum ... - Biosciweb.net

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.1Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006NAME:LAB SCORE:Phylum EchinodermataThe phylum Echinodermata is comprised of sea lilies, sea stars, brittle stars, sea urchins,sand dollars, and sea cucumbers. All echinoderms live in the marine environment. They arean odd group, strikingly different from any other animal phylum, a group that abandoned theadaptive advantages of bilateral symmetry to become radial.The echinoderms, with their calcareous endoskeletons have left an extensive fossil record.The first members, the crinoids, appeared and flourished in the Paleozoic seas and numerousforms evolved and have gone extinct over the intervening hundreds of millions of years. Todaythe echinoderms are represented by six classes, five of which we will review in lab.Echinoderms are deuterostomes, thus sharing with Hemichordata and Chordata severalembryological features that set them apart from the rest of the animal kingdom:‣ anus developing from or near the blastopore‣ mouth developing from a structure that is not the blastophore‣ enterocoelous coelom‣ radial and regulative cleavage‣ mesoderm derived from enterocoelous pouches.Thus, all three phyla (Echinocdermata, Hemichordata and Chordata) are presumably derivedfrom a common ancestor.It is an echinoderm's dermal endoskeleton of calcareous plates and spines, often fused intoan investing armor, that provides the group with its name (1. echinatus, prickly, + derma,skin).Body Plan Features Characteristic of Members of the Phylum Echinodermata:There are other characteristics, unique to echinoderms, that both define the group andlimit its evolutionary potential including:1. a water-vascular system that powers a multitude of tiny tube feet used forlocomotion and food gathering2. many have pincer-like pedicellariae that snap at creatures that would settle on them3. for respiration, many echinoderms rely on numerous dermal branchiae (skin gills)that project delicately through spaces in their skeletal armor4. no cephalization5. possess relatively primitive nervous systems and sense organs6. locomotion is slow7. no segmentation8. pentaradial symmetry: body parts always arranged radially in five or multiples of five,no matter how the body plan has become adapted to different feeding strategiesThis radial symmetry is, however, secondarily acquired because their larvae are bilaterallysymmetrical.

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.2Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006ClassificationPhylum EchinodermataClass Crinoidea (cry-noy'de-a) (Gr. krinon, lily, + eidos, form, + ea, characterized by). About620 species. Sea lilies and feather stars. Aboral attachment stalk of dermal ossicles. Anus onoral surface; five branching arms with pinnules; ciliated ambulacral groove on oral surface withtentacle-like tube feet for food collecting; spines, madreporite, and pedicellariae absent.Examples: Antedon, Florometra.Class Asteroidea (as'ter-oy'de-a) (Gr. aster, star, + eidos, form, + ea, characterized by). About1600 species. Sea stars. Starshaped, with arms not sharply marked off from centraldisc; ambulacral grooves open, with tube feet on oral side; tube feet often with suckers; anusand madreporite aboral; pedicellariae present. Examples: Asterias, Pisaster.Class Ophiuroidea (o'fe-u-roy'de-a) (Gr. ophi::,~ snake, + oura, tail, + eidos, form). About 2100species. Brittle stars and basket stars. Star-shaped, with arms sharply marked off fromcentral disc; ambulacral grooves closed, covered by ossicles; tube feet without suckers and notused for locomotion; pedicellariae absent. Examples: Ophiura, Gorgonocephalus, Ophioderma.Class Echinoidea (ek'i-noy'de-a) (Gr. echinos, sea urchin, hedgehog, + eidos, form). About 950species. Sea urchins, heart urchins, and sand dollars. More or less globular or disc-shaped,with no arms; compact skeleton, or test, with closely fitting plates; movable spines; ambulacralgrooves closed and covered by ossicles; tube feet with suckers; pedicellariae present.Examples: Arbacia, Strongylocentrotus, Lytechinus, Mellita.Class Holothuroidea (hol' o-thu-roy' de-a) (Gr. holothourion, sea cucumber, + eidos, form).About 1100 species. Sea cucpmbers. Cucumber-shaped; with no arms; spines absent;microscopic ossicles embedded in thick, muscular wall; anus present; ambulacral groovesclosed; tube feet with suckers; circumoral tentacles (modified tube feet); pedicellariae absent;madreporite plate internal. Examples: Tbyone, parastichopus, Cucumaria.

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.3Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006LAB PROCEDURERefer to Lab Exercise #16 in the Hickman lab manual for illustrations,diagrams, and additional information about echinoderms.Observation of Living SpecimensClass Crinoidea (sea lilies and feather stars)‣ If available, observe the crinoid specimens on display in the lab.‣ Record the descriptive information requested at the end of the lab.‣ If unavailable, go to the following website to view a crinoid:http://tolweb.org/tree?group=CrinoideaClass Asteroidea (sea stars)‣ Observe the asteroid specimens on display in the lab.‣ Record the descriptive information requested at the end of the lab forPisaster giganteus.Class Ophiuroidea (brittle stars and basket stars)‣ Observe the ophiuroid specimens on display in the lab.‣ Record the descriptive information requested at the end of the lab for one brittle starspecies.Class Echinoidea (sea urchins and sand dollars)‣ Observe the echinoid specimens on display in the lab.‣ Record the descriptive information requested at the end of the lab forStronglyocentrotus purpuratus.Class Holothuroidea (sea cucumbers)‣ Observe the holothuroid specimens on display in the lab.‣ Record the descriptive information requested at the end of the lab for one seacucumber species.

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.5Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006DISSECTIONClass AsteroideaPisaster giganteus (sea star)Use a dissecting scope for your investigation.Obtain one sea star specimen for each two students.‣ Examine the external anatomy of the sea star on both the dorsal and ventralsides and be able to identify the structures listed below. Note the pentaradialbody plan (symmetry) and with five arms or rays and the oral-aboral flatteningevident in this class.External Structures‣ central disc‣ five rays (arms)‣ tube feet (podia)‣ mouth‣ anus (at center of central disc)‣ bivium‣ trivium‣ madreporite‣ ambulachral grooves (in each arm; contains tube feet)‣ calcareous spines on ciliated epidermis‣ dermal branchiae (fingerlike bulges in epidermis for respiration)‣ pedicellariae (two-jawed modified spines that capture tiny prey and protect dermalbranchiae from collecting sediment and small parasites)‣ sensory tentacles (elongated tube feet at end of each arm)‣ pigmented eyespots (on end of each arm; small red spot)‣ Examine the internal anatomy of the sea star from the dorsal side and be ableto identify the structures listed below. Place the specimen aboral side up in adissecting pan and cover with water. Select the three arms of the trivium andsnip off their distal ends. Insert a scissors point under the body wall at the cutend of one of the arms. Carefully cut along the dorsolateral margins of each armto the central disc. Lift up the loosened wall and carefully free any clingingorgans. Uncover the central disc, but cut around the madreporite plate, leaving itin place. Be careful not to damage the delicate tissue underneath. The tissuearound the anal opening in the center of the disc will cling. Cut the very shortintestine close to the aboral wall before lifting off the body wall.Internal Structures‣ stone canal leads to madreporite‣ ring canal (as visible)‣ radial canals‣ ampullae of tube feet‣ gonads‣ pyloric stomach (more dorsal)‣ cardiac stomach (more ventral)‣ hepatic/pyloric cecae

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.6Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006Asteroidea Anatomy

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.7Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006For Asteroidea Internal Anatomy, see Figures 16-3 and 16-4 in labmanual.Asteroidea – Anatomy of the Water Vascular System

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.8Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006Class EchinoideaStudy of a Living Stronglyocentrotus purpuratus (sea urchin)‣ Each table of students should look at one of the living sea urchin specimens(3 specimens per lab).‣ Obtain a sea urchin specimen and place it in a bowl of sea water.‣ Study the behavior and then examine it under the dissecting scope to reveal detail.‣ One group at each table will dissect the sea urchin and all students at each tableshould review its structure.Sea urchins are usually common on a rocky sea bottom, especially when there is a thickgrowth of algae. They occur most commonly from the low-tide mark to a depth of about 20fathoms, but they are also found at greater depths. They move slowly by means of ventralspines, and climb using their tube feet. The five large teeth in the jaw apparatus (Aristotle’slantern) are used for browsing on algae and on small encrusting animals. Breeding takes placemainly in winter. Fertilization is external and each zygote develops into a pelagicechinopluteus larva which feeds on other planktonic organisms before going throughmetamorphosis and settling in the benthic habitat.‣ Place the sea urchin on its back in an aquarium and time its righting response.‣ How long does it take?‣ Briefly describe the techniques used in righting itself.‣ Briefly describe the feeding response of the sea urchin to small bits of kelp.‣ Describe or sketch a couple of different types of pedicellaria of the sea urchinStronglyocentrotus purpuratus as observed under the dissecting scope.Generalized pedicellaria

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.9Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006DISSECTIONClass EchinoideaStronglyocentrotus purpuratus (sea urchin)Use a dissecting scope for your investigation.Obtain one sea urchin specimen for each entire table students (3 per lab).‣ Examine the external anatomy of the sea urchin on both the dorsal andventral sides and be able to identify the structures listed below. Note thepentaradial body plan (symmetry). Refer to Figure 16-8 in lab manual.External Structures‣ spines‣ five ambulacral regions (contain tube feet)‣ tube feet (podia)‣ mouth (with Aristotle’s lantern; teeth)‣ anus‣ madreporite‣ pedicellaria‣ periostomal gills (five pairs)‣ Examine the internal anatomy of the sea urchin and be able to identify thestructures listed below. Hold the sea urchin very gently when dissecting; the testis relatively fragile. Remove the thin “skin” around the mouth to get a better viewof the teeth. Remove some of the spines around the “top” of the test to see theanus. Remove the spines from the test’s equator before making the midlateralcut. To make the cut, force the sharp point of the scissors through the test wall(don’t cut too deeply; you could damage the gonads and intestines) and cutcompletely around the test’s equator. Gently separate the 2 halves of the test toexamine the internal structures. Try to keep all internal structures intact ifpossible. Refer to diagram on the following page.Internal Structures‣ Aristotle’s lantern‣ ampullae of tube feet‣ stomach‣ intestine‣ rectum‣ gonad

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.10Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006Echinoidea Internal Anatomy

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.11Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006Phylum ChordataChordates show a remarkable diversity of form and function, ranging from protochordatesto humans. Although all organ systems are well developed in this group, the nervoussystem has been chiefly responsible for giving the phylum its eminence among animals.Most chordates are vertebrates, but the phylum also includes a few invertebrate groups.All animals that belong to phylum Chordata must have at some time in their life cycle thefollowing characteristics.1. Notochord. The notochord (Gr. naton, back, + chorda, cord) is a slender rod of cartilagelikeconnective tissue lying near the dorsal side and extending most of the length of theanimal. It is regarded as an early endoskeleton and has the functions of such. In mostvertebrates, it is found only in the embryo.2. Pharyngeal pouches and slits. The pharyngeal pouches and slits (gill slits) are a series ofpaired slits in the pharynx, serving as passageways for water to the gills. In somevertebrates, they appear only in the embryonic stages.3. Dorsal tubular nerve cord. A dorsal tubular nerve cord, with its modification, the brain,forms the central nervous system. It lies dorsal to the alimentary tract and has a fluidfilledcavity, in contrast to the invertebrate nerve cord, which is ventral and solid.4. Endostyle or thyroid gland. The endostyle or its derivative, the thyroid gland, is found inall chordates, but in no other animals. The endostyle secretes mucus and traps small foodparticles for protochordates and lamprey larvae. Some cells in the endostyle arehomologous with cells of the thyroid gland found in the remainder of vertebrates.5. Postanal tail. A postanal tail projects beyond the anus at some stage and serves as ameans of propulsion in water. It mayor may not persist in the adult. Along with bodymuscles and stiffened notochord, it provides motility for a free-swimming existence.These features vary in chordates. Some ancestral chordates have all of these structuresthroughout life. In many chordates, the pharyngeal slits never break through from thepharynx but merely form pouches that have no function, the notochord is replaced by thevertebral column, and only the dorsal nerve cord actually persists in the adult as adiagnostic chordate character. Protochordates demonstrate each of the chief chordatecharacteristics at some point in their life cycle.

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.12Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006ClassificationPhylum ChordataSubphylum Urochordata (u'ro-kor-da'ta) (Gr. oura, tail, + L. chorda, cord). (Tunicata). About2000 species. Tunicates. Only larval forms have all chordate characteristics; adults sessile,without notochord and dorsal nerve cord; body enclosed in tunic.Example: Molgula, a sea squirt.Subphylum Cephalochordata (sef'a-Io-kor-da'ta) (Gr. kephalE, head, + L. chorda, cord). About22 species. Lancelet. Notochord and nerve cord persist throughout life; lance-shaped.Example: Branchiostoma (amphioxus).Subphylum Vertebrata (ver'te-bra'ta) (L. vertebratus, backboned). (Craniata). About 50, 900species. Vertebrates. Enlarged brain enclosed in cranium; nerve cord surrounded by bony orcartilaginous vertebrae; notochord in all embryonic stages and persists in adults of somefishes; typical structures include two pairs of appendages and body plan of head, trunk, andpostanal tail.LAB PROCEDURERefer to Lab Exercise #17 in the Hickman lab manual for illustrations,diagrams, and additional information about urochordates andcephalochordates.Observation of Living SpecimensPhylum ChordataSubphylum Urochordata (sea squirts/tunicates)‣ Observe the urochordate specimens on display in the lab.‣ Record the descriptive information requested at the end of the lab.Subphylum UrochordataUrochordata (Gr. oura, tail, + L. chorda, cord) are commonly called tunicates because oftheir leathery covering, or tunic. They are divided into three classes: Ascidiacea,sea squirts; Thaliacea, salpians; and Larvacea, appendicularians. The largest group is theascidians (Gr. askidion, leather bag or bottle), which are also the most generalized. They arecalled sea squirts because of their habit, when handled, of squirting water from the excurrentsiphon. Any of the small, translucent ascidians may be used for this exercise. Adult tunicatesare sessile, whereas the larvae undergo a brief free-swimming existence.Tunicates are found in all seas and at all depths. Most of them are sessile as adults, althoughsome are pelagic (found in the open ocean). Ciona intestinalis (Gr. Chione, demigoddess ofmythology) is a cosmopolitan species common in shallow water on wharf pilings, on anchoredand submerged objects, and on eelgrass. It grows to 15 em in its largest dimension. Althoughsea squirts (ascidians of class Ascidiacea) are common, they also are commonly overlooked inthe marine environment. Nearly all shallow-water sea squirts are found attached to almost anyavailable rigid surface: wharf pilings, rocks, shells, and ship bottoms. One of the best places tosee sea squirts is on pilings, where they may cover the surface.

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.13Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006Urochordate (Tunicate) Anatomy(Also refer to Figure 17-3 in lab manual)

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.14Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006Subphylum Urochordata‣ Describe the feeding mode for an adult tunicate, tracing the path of water flow throughthe body. Be sure to include the names and roles of all the structures (from the diagramsincluded in the lab) involved in food collection. You may use the internet to aid you in youranswer.Phylum ChordataSubphylum Cephalochordata (lancelets)‣ Observe the cephalochordate Branchiostoma (Amphioxus) sp. (as available) ondisplay in the lab.‣ Record the descriptive information requested at the end of the lab.Subphylum CephalochordataVarious researches have suggested that those structures of Amphioxus listed below arehomologous with those of vertebrates. In other words, they may be derived from the samestructure in a common ancestor. Since Amphioxus appears to be primitive in structure(meaning it has probably changed very little from ancestors which gave rise to vertebrates),study of Amphioxus may give us an idea of what the early vertebrates looked like. On the otherhand, some biologists (eg. Hyman) are critical of some of these interpretations.

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.15Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006Study of Branchiostoma (Amphioxus) sp. (lancelet)‣ Obtain prepared slides of a whole mount and cross section of Branchiostoma(Amphioxus) sp. and study them under the 4X and the 10X objectives and identify thefollowing structures:Whole Mount Structures‣ oral hood‣ notochord‣ neural tube‣ pharynx‣ dorsal fin‣ ventral fin‣ caudal fin‣ atrium‣ atriopore‣ myotomes‣ hepatic cecum‣ buccal cirriCross Section Structures‣ atrial cavity‣ dorsal fin‣ neural tube‣ pharynx‣ myotomes‣ gill bars‣ dorsal aorta‣ metapleural folds‣ notocord‣ Which direction does the apex of the chevron-like myotome “V” point?Anteriorly or Posteriorly?‣ Describe the feeding mode for an adult lancelet, tracing the path of water flow throughthe body. Be sure to include the names and roles of all the structures (from the diagramsincluded in the lab) involved in food collection. You may use the internet to aid you in youranswer.

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.16Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006Cephalochordate (lancelet) Anatomy(Also refer to Figure 17-6 in lab manual)

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.17Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006Living Specimens DataPhylum EchinodermataClass Asteroidea (sea stars)Scientific name: Pisaster giganteusCommon name:Notes & observations to help you remember and distinguish this class:Phylum EchinodermataClass Ophiurodea (brittle stars and basket stars)Scientific name:Common name:Notes & observations to help you remember and distinguish this class:

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.18Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006Phylum EchinodermataClass Echinoidea (sea urchins and sand dollars)Scientific name: Stronglyocentratus purpuratusCommon name:Notes & observations to help you remember and distinguish this class:Phylum EchinodermataClass Holothuroidea (sea cucumbers)Scientific name:Common name:Notes & observations to help you remember and distinguish this class:

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.19Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006Phylum EchinodermataClass Crinoidea (sea lilies and feather stars)Scientific name:Common name:Notes & observations to help you remember and distinguish this class:Phylum ChordataSubphylum Urochordata (sea squirts/tunicates)Scientific name:Common name:Notes & observations to help you remember and distinguish this class:Phylum ChordataSubphylum Cephalochordata (lancelets)Scientific name: Branchiostoma (Amphioxus) sp. (as available)Common name:Notes & observations to help you remember and distinguish this class:

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.20Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006More on Animal Development – Terms Relevant to Classificationblastomere = an early cleavage cell in a developing embryoCleavage = early embryonic cell divisions (mitosis)determinate cleavage = the type of cleavage, usually spiral, in which the fate of theblastomeres is determined very early in development; mosaic cleavagemosaic cleavage = embryonic development characterized by independent differentiation ofeach part of the embryoindeterminate cleavage/development = the type of embryonic development in which the fateof blastomeres is not determined very early as to tissues or organs (cell differentiation);regulative cleavageregulative cleavage/development = embryonic development determined by interactionsamong neighboring cells; cell fates are not fixed early in developmentCoelom Formationschizocoelic coelom and mesoderm formation = formation of a coelom by splitting of theembryonic mesoderm; embryonic formation of the mesoderm as cords of cells betweenectoderm and endoderm; splitting of these cords results in the coelomic spaceenterocoelic coelom and mesoderm formation = formation of a coelom by outpouching ofthe mesodermal sac from the endoderm of the primitive gut; embryonic formation of themesoderm by a pouchlike outfolding from the archenteron, which then expands and obliteratesthe blastocoel, thus forming a large cavity, the coelom, lined with mesodermarchenteron = the main cavity of an embryo in the gastrula stage; it is lined with endodermand represents the future digestive cavitysee next page

Phylum Echinodermata, Introduction to Phylum Chordata& More on Animal Development 15.21Lab #15 -- Biological Sciences 102 – Animal Biology – Spring 2006ProtostomiaA group of phyla in which cleavage is determinate, the coelom (in coelmate forms) is formed byproliferation of mesodermal bands (schizocoelic formation), the mesoderm is formed from aparticular blastomere (called 4d) and the mouth is derived from or near the blastopore;includes the phyla Annelida, Mollusca, Arthropoda and a number of minor phyla.Blastopore becomes the mouth.Ecdysozoan ProtostomesAny member of a clade within Protostomia whose members shed the cuticle as they grow;includes the phyla Arthropoda, Nematoda and several smaller phyla.Lophotrochozoan ProtostomesAny member of a clade within Protostomia whose members generally possess either atrochophore larva or a lophophore; includes the phyla Annelida, Mollusca and the ectoproctstrochophore larvae = a free-swimming ciliated marine larva characteristic of most molluscsand certain ectoprocts, brachiopods, and marine worms; an ovoid or pyriform body withpreoral circlet of cilia and sometimes a secondary circlet behind the mouth.lophophore = tentacle-bearing ridge or arm within which is an extension of the coelomic cavityin lophophorate animals.ectoproct = bryozoans (moss animals); psuedocoelomate animals that have their anus locatedwithin a crown of tentacles; about 4500 species; both freshwater and marine; few more than0.5 mm longDeuterostomiaA group of phyla in which cleavage is indeterminate (regulative) and primitively radial. Themesoderm arises by enterocoelic formation, and the mouth is derived away from theblastopore; includes the phyla Echinodermata, Chordata and Hemichordata.Blastopore becomes the anus.