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Animal Diversity > Midterm II (Echinodermata) > Flashcards

Midterm II (Echinodermata) Flashcards

1
Q

Deuterostome Embryogenesis

A
  1. Radial Cleavage (opposed to spiral)
  2. Regulative (indeterminate) embryo (if you were to remove one one cell, still develop into animal)
  3. Fate of blastopore -> anus (i.e., mouth second)
  4. Enterocoelous (outpocketing) coelom formation (coelom is formed from outpocketing of developing gut, not base)
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2
Q

Deuterostomia common traits

A
  • Gill slits in pharynx
    (true synapomorphy)
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3
Q

Deuterostomes groups

A
  • Ambulacraria -> Echinodermata, Hemichordata
  • Chordata
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4
Q

Echinodermata Stem groups

A
  1. Stem Group A
    - Motile, bilateral, gills slits
  2. Stem Group B
    - Asymmetric, stalked, gill slits
  3. Stem Group C
    - Stalked, beginnings or radial symmetry (suspension feeders)
    - Probably loss of gill slits
  4. Stem Group D
    - Still attached with suspension feeding
    - Ambulacral grooves
    - Closest to crown group ancestor
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5
Q

Phylum Echinodermata

A
  • “spiny + skin”
    Exclusively marine; mostly benthic
  • 7000+ spp; 5 classes
    Lack of cephalization
    Loss of gill slits
    5 Unique features (autapomorphies):
    1. Pentaradial symmetry in adults
    2. Calcareous endoskeleton
    3. Water vascular system
    4. Pedicellariae
    5. Dermal branchiae (papulae)
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6
Q

Pentaradial symmetry

A
  • 5 lines of symmetry
  • 5 arms: starfish
  • evolved from bilateral ancestor
  • Larvae Bilateral, so part of bilateral clade, not radial
  • Mouth side = oral
  • Opposite of mouth = aboral
  • Madreporite of aboral side, lets water in
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7
Q

Calcareous Endoskeleton

A

Mesodermal porous endoskeleton
- meshwork of ossicles (e.g., plates) form the stereom (unique)
- w. spines and tubercle projections
- unique fine meshwork (porous) of CaCO3 (Calcareous)
Connected by mutable “catch collagen”
- Can change from liquid to solid (i.e., change positions without muscular effort)

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8
Q

Water Vascular System

A

Hydraulic (fluid) system
- canal and tube feet
- only open on one end
- specialized coelomic system
Functions:
- respiration
- excretion
- locomotion
- feeding (evolve for)
Order that water goes in (parts):

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9
Q

Ambulacra

A
  • The bands from which tube feet project
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10
Q

Pedicellariae

A

On aboral surface
Functions:
- Cleaning
- Food capture
- Defense

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11
Q

Dermal Branchiae (Papulae)

A
  • Also called skin gills
  • Projections of thin-walled coelom
    (bubbles on surface of aboral, coming from dermal branchiae (breathing))
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12
Q

Basic Internal Characteristics

A

Nervous system
- No brain ganglia
- Nerve ring, radial nerves, and epidermal nerve net
- Sensory cells, eyespots (tip of arms)
Digestive system
- Feeding mode varies (carnivores (stick stomach out), scavengers, herbivores, deposit feeders, suspension feeders)
Reproduction
- Often separate sexes with external fertilization

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13
Q

Larval Development

A
  1. Deuterostome embryology
  2. Bilateral free-swimming larvae
    - left side becomes the oral surface
    - right side comes aboral surface
    - With tube feet
  3. Metamorphosis to adult form
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14
Q

Regeneration

A
  • Only need is 1/5 of the central disk and 1 arm!
  • Also able to deliberately shed body parts or appendages = autotomy
  • Used as an escape response to predators
  • Or as a means of replacing infected or damaged appendages
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15
Q

Fragmentation, not regeneration

A
  • e.g., Link “comets”
  • can cast off an arm without any part of the central body attached, and that arm will slowly grow into a complete starfish
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16
Q

Phylum Echinodermata -> class Asteroidea

A

“Star-form”; sea stars, starfish
1500+ spp.
The “poster” echinoderm
- Central disc + 5 arms
- Or 7 arms, or almost 50!
Two-part stomach
- can even evert cardiac stomach
Scavenger and carnivores
- can also suspension feed

17
Q

Keystone Species of class Asteroidea (sea stars)

A
  • Keystone: incredibly important to environment/ecosystem
    1. Pisaster ochraceus: purple intertidal seastar
  • Controls B.C. mussel pops
    2. Stichaster australis: reef sea star
18
Q

Deadly Asteroids

A
  1. Ancanthaster planci: Crown-of-thorns (Indonesian) (eat polyps off corals)
  2. Pycnopodia helianthoides: Pacific sunflower sea star
19
Q

Dead Asteroids

A

Good sense of the ecosystem based on whether or not sea stars are healthy
Sea star wasting disease
- white lesions, water vascular system stops working (“limp”); fragmentation; death
Associated with warmer temps and densovirus

20
Q

Phylum Echinodermata -> Class Ophiuroidea

A
  • “like a serpent”
  • Brittle stars and basket stars
  • 2000+ species
  • Abundant (form huge carpets)
  • Move with flexible articulated arms
    • closed ambulacral grooves
    • Tube feet for feeding, no
      suckers
  • No pedicellariae, no papulae
  • Madreporite on oral side
  • No anus (indigestibles out the mouth)
  • Organs inside central disc
  • Fragile, w. remarkable regeneration
21
Q

Phylum Echinodermata -> Class Echinoidea

A

“hedgehog” form
Sea urchins, sand dollars, and heart urchins
Around 950 spp; Green Sea Urchin (Strongylocentrotus droebachiensis)
Compact body within a test
- Ossicles as plates
- Some secondarily bilateral
- e.g., sand dollars and heart urchins
5 ambulacra extents up and around towards anus (aboral)
- i.e. No arms
Tube feet for locomotion w. assist from spines in socket joint (unique)
- Short spines on sand dollars
Many with venomous pedicellariae (3 jaws)
Mostly herbivorous
- Aristotle’s lantern with 5 teeth (circular row of teeth)
- Sand dollars deposit feeders (find them in mud)

22
Q

Ecological Impacts of Urchins

A

Kelp forest destruction
- “urchin barren”
Keystone species: sea otter, eat urchins and restore kelp pop

23
Q

Phylum Echinodermata -> Class Holothuroidea

A

“obscure form”
Sea cucumbers
Around 1150 species
Elongated on oral-aboral axis
Secondarily bilateral
Reduced ossicles
“Ventral” tube feet specialized for locomotion on “sole”
- No arms
- Benthic crawlers
- Burrowers (circular and longitudinal muscles, no podia)

24
Q

Class Holothuroidea (II)

A

Spacious coelomic cavity
- Hydrostatic skeleton
Oral tentacles are modified tube feet for suspension or deposit feeding
- Important nutrient cyclers
Cloaca
- “all-purpose orifice” via anus
- Respiration (respiratory tree) and excretion (unique)
Amazing self defense!
- Evisceration of Cuvierian tubules, resp, tree, or guts
Some are pelagic spp.!
- Benthopelagic
- True pelagic (1 spp.)

25
Q

Phylum Echinodermata -> Class Crinoidea

A

“lily” form
Around 625 spp.
Stalk with cirri attached to aboral side of calyx with many arms
Sea lilies:
- flower-shaped on top of stalk attached to substrate
Feather stars:
- Short stalk w. many branched arms
Can move/crawl/sweep/swim via cirri or feathery arms
No pedicellariae, no madreporite, no spines
Mouth and anus on oral side
Many deep water
- But high diversity of feather stars in shallow Indo-Pacific and West Indies

Animal Diversity (15 decks)

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