< Return to Video

La dissection étoile de mer

  • 0:03 - 0:04
    University of Lille 1 - Faculty of biology
  • 0:05 - 0:06
    Animal Biology
  • 0:34 - 0:38
    Sea star dissection
  • 0:40 - 0:42
    Morphology
  • 0:46 - 0:49
    The Asteria rubens sea star
  • 0:49 - 0:51
    is an Echinoderm
  • 0:51 - 0:53
    belonging to the class of Asteroidea.
  • 0:55 - 0:56
    It lives on costs
  • 0:56 - 0:58
    we may find it in the intertidal zone
  • 0:58 - 1:00
    at low tide.
  • 1:02 - 1:04
    It feeds chiefly on mussels
  • 1:04 - 1:06
    fixed on rocks.
  • 1:09 - 1:12
    The sea star is part of the foreshore food web
  • 1:12 - 1:15
    and can fall prey to other animals.
  • 1:21 - 1:23
    The body of the sea star is flattened,
  • 1:23 - 1:26
    in a shape of a star with 5 arms.
  • 1:27 - 1:30
    The arms merge at their base
  • 1:30 - 1:32
    and are attached to the flat disk.
  • 1:38 - 1:40
    The arms are called radius
  • 1:41 - 1:45
    The zones between the arms are called interradius.
  • 1:48 - 1:52
    This organisation is representative of the pentaradial symmetry,
  • 1:52 - 1:56
    characteristic of the adult echinoderms.
  • 1:59 - 2:01
    The sea star has two faces:
  • 2:02 - 2:03
    the upper face,
  • 2:03 - 2:05
    or aboral surface,
  • 2:05 - 2:08
    is convex and pigmented.
  • 2:08 - 2:10
    The bottom side
  • 2:10 - 2:11
    or oral surface,
  • 2:11 - 2:13
    is flattened, and clearer,
  • 2:13 - 2:15
    in contact with the substrate.
  • 2:18 - 2:20
    This surface includes the mouth,
  • 2:20 - 2:22
    located in the middle of the flat disk.
  • 2:26 - 2:27
    On the aboral surface,
  • 2:27 - 2:29
    at the interradius level,
  • 2:29 - 2:32
    we can see a whitish limestone plate,
  • 2:32 - 2:34
    the madreporic plate.
  • 2:37 - 2:40
    There are bony spines convering the body,
  • 2:40 - 2:43
    organized in rows.
  • 2:43 - 2:45
    On the aboral surface,
  • 2:45 - 2:50
    there is a row in the middle of each arm
  • 2:50 - 2:52
    and two or three lateral rows.
  • 2:56 - 2:58
    By turning the sea star over,
  • 2:58 - 3:01
    we can see a supramarginal row
  • 3:02 - 3:05
    and an inframarginal row
  • 3:08 - 3:11
    Two rows of prikly adambulacra
  • 3:11 - 3:13
    delimit a central furrow,
  • 3:13 - 3:15
    the ambulacral groove,
  • 3:20 - 3:24
    Every ambulacral groove has 4 rows of fleshy and movable tubes
  • 3:24 - 3:27
    tube feet or podia,
  • 3:28 - 3:30
    ended by a sucker.
  • 3:33 - 3:37
    At tip of each arms we can see eyespots,
  • 3:38 - 3:40
    sensory organs red in coulour
  • 3:40 - 3:42
    sensitives to the light.
  • 3:44 - 3:47
    Integument
  • 3:48 - 3:49
    In the sea star,
  • 3:49 - 3:51
    the body and the spines are covered
  • 3:51 - 3:53
    by an ciliated epidermis
  • 3:55 - 3:55
    The dermis,
  • 3:55 - 3:57
    situated beneath the epidermis,
  • 3:57 - 3:59
    has calcareous plates,
  • 3:59 - 4:01
    or ossicles
  • 4:01 - 4:03
    in which the spines are articulated.
  • 4:05 - 4:07
    The locations of ossicles
  • 4:07 - 4:09
    are visibles on the surface of the animal.
  • 4:12 - 4:15
    The integument has specialized structures,
  • 4:15 - 4:16
    pedicellariae,
  • 4:19 - 4:22
    put in the shape of a crown at the base of the spines.
  • 4:25 - 4:26
    In Asteroidae,
  • 4:26 - 4:28
    they have a form of a pincer with two jaws.
  • 4:31 - 4:33
    Pedicellariae are used
  • 4:33 - 4:34
    to clean the integument
  • 4:34 - 4:36
    and the defense of the animal
  • 4:39 - 4:42
    Organs used for the breathing,
  • 4:42 - 4:44
    gills or papules,
  • 4:44 - 4:46
    are associated with the integument.
  • 4:49 - 4:52
    they are between the ossicles of the skeleton.
  • 4:55 - 4:57
    The presence of an epithelium
  • 4:57 - 5:00
    ciliated on the inner side of the integument
  • 5:00 - 5:02
    enables the circulation of the liquid
  • 5:02 - 5:04
    inside the body cavity,
  • 5:04 - 5:06
    the coelom.
  • 5:10 - 5:14
    Echinoderms have a calcareous internal skeleton,
  • 5:14 - 5:16
    formed by ossicles.
  • 5:21 - 5:24
    the cross section of the arm enables us
  • 5:24 - 5:27
    to observe the organisation of the dermal plates.
  • 5:38 - 5:40
    We can see:
  • 5:40 - 5:42
    a dorsal ossicle
  • 5:43 - 5:45
    two supramarginal plates
  • 5:46 - 5:50
    and two inframarginal plates each having spines,
  • 5:51 - 5:54
    two adambulacra plates
  • 5:54 - 5:56
    and two ambulacral plates.
  • 6:00 - 6:02
    Between the ambulacral plates,
  • 6:02 - 6:06
    there are pores that allows the passage of the tube feet.
  • 6:11 - 6:14
    General anatomy
  • 6:14 - 6:17
    To observe the internal organisation of the sea star,
  • 6:18 - 6:21
    we have to cut the sea star with scissors.
  • 6:23 - 6:25
    Incise the integument
  • 6:25 - 6:27
    following the outline
  • 6:27 - 6:29
    to separate the upper half
  • 6:29 - 6:32
    from the lower half of the animal.
  • 6:34 - 6:37
    Identify the madreporic plate
  • 6:39 - 6:43
    and avoid it when you incise.
  • 6:47 - 6:50
    Lift the integument of the aboral surface
  • 6:50 - 6:52
    starting from the end of the arms
  • 6:54 - 6:57
    and cut carefully the underlying organs
  • 7:00 - 7:02
    ending by the flat disk.
  • 7:06 - 7:10
    The rest of the dissection will be done in the water.
  • 7:13 - 7:16
    In the coelom we can see gonads
  • 7:16 - 7:19
    and a part of the digestive system.
  • 7:22 - 7:25
    The digestive system
  • 7:25 - 7:28
    The digestive system includes the mouth,
  • 7:30 - 7:33
    the stomach divided in two superimposed chambers,
  • 7:34 - 7:37
    the pyloric ceca and the rectal ceca.
  • 7:38 - 7:41
    It ends by a microscopic anus,
  • 7:41 - 7:43
    located in the aboral surface.
  • 7:45 - 7:47
    The observation of the digestve system
  • 7:47 - 7:51
    will be done using the aboral portion.
  • 7:52 - 7:54
    In the central part of the disk,
  • 7:54 - 7:57
    we notice two rectal ceca.
  • 8:01 - 8:05
    Below we notice the upper chamber of the stomach,
  • 8:05 - 8:09
    the pyloric portion with a pentagonal shape.
  • 8:12 - 8:15
    5 canals start from this chamber
  • 8:15 - 8:18
    that extend themselves in the arms of the star.
  • 8:20 - 8:23
    Each pyloric canal is connected to two pyloric ceca
  • 8:23 - 8:26
    that take up a large part of the arms.
  • 8:29 - 8:30
    The pyloric ceca,
  • 8:30 - 8:34
    composed by dozens of diverticula on dead end
  • 8:34 - 8:36
    play a digestive key role
  • 8:36 - 8:40
    and are used to the storage of nutrients.
  • 8:41 - 8:44
    To observe the rest of the digestive system
  • 8:44 - 8:47
    we have to remove the rectal ceca,
  • 8:49 - 8:51
    pyloric ceca
  • 9:04 - 9:06
    and the pyloric stomach.
  • 9:10 - 9:14
    The ventral chamber or cardiac stomach,
  • 9:14 - 9:17
    has a shape of five lobes rose.
  • 9:20 - 9:21
    For the ingestion of preys,
  • 9:21 - 9:25
    this part of the stomach is everted.
  • 9:27 - 9:29
    After the external digestion,
  • 9:29 - 9:32
    the stomach gets back to its position
  • 9:32 - 9:36
    thanks to the contraction of five pairs of retractor muscles
  • 9:36 - 9:40
    put in the ambulacral plates.
  • 9:41 - 9:44
    To see the mouth,
  • 9:44 - 9:47
    we have to detach the retractor muscles
  • 9:51 - 9:55
    and remove the portion of cardiac stomach.
  • 9:56 - 9:58
    The mouth,
  • 9:58 - 10:00
    located in the middle of the flat disk,
  • 10:01 - 10:03
    surrounded by a membrane,
  • 10:03 - 10:05
    the peristomium.
  • 10:08 - 10:10
    Reproductive system
  • 10:12 - 10:14
    In Asteroidea
  • 10:14 - 10:15
    the sexes are separated
  • 10:15 - 10:18
    but there is not a sexual dimorphism.
  • 10:20 - 10:23
    Gonads are located in the coelom.
  • 10:26 - 10:28
    To observe the gonads
  • 10:28 - 10:31
    we have to remove the pyloric ceca,
  • 10:33 - 10:35
    and the upper chamber of the stomach.
  • 10:39 - 10:40
    Every gonad,
  • 10:40 - 10:42
    with a granular apsect,
  • 10:42 - 10:44
    is divided in deux lobes
  • 10:44 - 10:48
    that all extend in two adjacent arms.
  • 10:51 - 10:53
    The size of gonads is variable,
  • 10:53 - 10:57
    it depends on the state of sexual maturation of the animal.
  • 10:59 - 11:02
    Females and males produce gametes
  • 11:02 - 11:06
    through genital pores located in the interradius
  • 11:06 - 11:09
    at the junction with the flat disk.
  • 11:12 - 11:14
    The fecondation is extern.
  • 11:17 - 11:20
    Aquifer system
  • 11:21 - 11:24
    One of the characteristic of Echinoderms
  • 11:24 - 11:26
    is the existence of an aquifer system.
  • 11:27 - 11:31
    It is involve in the locomotion and the food intake.
  • 11:33 - 11:36
    This system have a network of conduits
  • 11:36 - 11:37
    filled with a liquid
  • 11:37 - 11:41
    whose composition is close to the sea water
  • 11:42 - 11:47
    The aquifer system have a madreporic plate,
  • 11:48 - 11:50
    the stone canal,
  • 11:51 - 11:53
    the ambulacral ring,
  • 11:54 - 11:56
    five radial canals,
  • 11:57 - 12:00
    and many tube feet or podia.
  • 12:02 - 12:05
    To observe the different parts of the aquifer system
  • 12:05 - 12:07
    we have to open the sea star
  • 12:09 - 12:11
    and remove the digestive
  • 12:13 - 12:15
    and reproductive system.
  • 12:16 - 12:19
    The madreporic plate, or madreporite,
  • 12:20 - 12:23
    is visible on the aboral surface of the animal.
  • 12:25 - 12:27
    This calcareous plate is riddle with holes
  • 12:27 - 12:29
    "aquifer pores"
  • 12:30 - 12:33
    that permit the sea water to enter in the system.
  • 12:36 - 12:40
    The madreporite is in connection with the madreporic canal
  • 12:40 - 12:42
    or stone canal.
  • 12:43 - 12:45
    This canal
  • 12:45 - 12:48
    sostained by superimposed calcareous rings,
  • 12:48 - 12:51
    go down toward the oral surface of the animal.
  • 12:53 - 12:55
    The stone canal
  • 12:55 - 12:58
    rejoin the ambulacral ring surrounding the mouth.
  • 12:59 - 13:00
    This ring is hidden
  • 13:00 - 13:02
    with calcareous plates of the skeleton.
  • 13:04 - 13:07
    On the circumference of the ambulacral ring of the star
  • 13:07 - 13:09
    in the interradial position,
  • 13:09 - 13:13
    we notice 9 vesicles with an immune function:
  • 13:13 - 13:15
    Tiedemann bodies.
  • 13:19 - 13:22
    From the aquifer ring goes in each arm
  • 13:22 - 13:25
    an ambulacral canal or radial canal,
  • 13:26 - 13:29
    located between the epidermis and the ambulacral plate.
  • 13:32 - 13:37
    From the radial canal goes many lateral canals.
  • 13:40 - 13:44
    Those are connected to the tube feet or podia.
  • 13:48 - 13:52
    The injection of a dye into ambulacral canal of an arm
  • 13:52 - 13:54
    enables us to hightlight
  • 13:54 - 13:57
    a large part of the aquifer system.
  • 14:01 - 14:04
    Podia have three parts:
  • 14:05 - 14:08
    ampulla or bulbous ampulla
  • 14:10 - 14:13
    a muscular and elongated foot
  • 14:14 - 14:16
    and a sucker at the end.
  • 14:21 - 14:24
    The podia go through the skeleton at pores level
  • 14:24 - 14:27
    located between the two adjacent ambucral plates.
  • 14:30 - 14:32
    To observe those pores
  • 14:32 - 14:34
    we have to scratch the polian vesicules
  • 14:34 - 14:36
    on a part of the arm.
  • 14:38 - 14:40
    The contraction of the polian vesicles
  • 14:40 - 14:43
    allows the turgescence of the tube feet
  • 14:43 - 14:47
    and the the monitoring of the sucker
    for the locomotion of the animal
  • 14:51 - 14:54
    The podia within the ambulacral groove
  • 14:54 - 14:58
    are protected by rows of movable ambulacral spines
  • 14:58 - 15:01
    and by many pedicellariae.
  • 15:04 - 15:05
    Radial canals
  • 15:05 - 15:08
    end with sensory tentacles
  • 15:08 - 15:11
    close to the eyespot.
  • 15:16 - 15:18
    Pedagogical design: Pierre-Eric Sautière Jacopo Viziolo
  • 15:20 - 15:24
    Technical production: Bernard Mikolajczyk
  • 15:25 - 15:29
    Designs: Jacopo Vizioli
  • 15:29 - 15:34
    Computer graphics: 3D MEDICUS
  • 15:39 - 15:42
    Voice over: Alain Nempont
  • 15:44 - 15:47
    Music; Ambient slamming bass jam, Jay Berlinsky
  • 15:49 - 15:53
    Gratitude: Sébastien Lefebvre, Michel Priem
  • 15:54 - 15:58
    Gratitude: Patrick Flammang, Michel Jangoux
  • 15:59 - 16:03
    SEEM; Education Service and Multimedia
Title:
La dissection étoile de mer
Description:

« La dissection de l 'étoile de mer » fait partie d'une série de films de biologie qui ont pour sujet les plans d'organisation d'animaux représentatifs des principaux groupes de vertébrés et invertébrés. Grâce à des images HD, des animations et des schémas annotés, ce film montre étape par étape, la démarche de dissection de l'animal. Les différents chapitres de l'ouvrage présentent la morphologie, le tégument, l'anatomie générale, les appareils digestif, génital et aquifère de l'étoile de mer.

more » « less
Video Language:
French
Duration:
16:05

English subtitles

Revisions