Class Notes (1,100,000)
CA (650,000)
York (40,000)
BIOL (2,000)
BIOL 2030 (100)


Course Code
BIOL 2030
Scott Kelly

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Echinodermata: Starfish & cousins
Phylum of marine coelomate animals that are bilaterally symmetrical as larvae but show
five-rayed symmetry as adults and have a calcareous endoskeleton and a water vascular
system; includes Crinoidea, Asteroidea, Ophiuroidea, Echinoidea, Holothuroidea
Away from, or opposite to, the mouth
Elongated area of the shell of echinoderm in which a row of tube-feet is arranged
Internal reservoir on ring canal of water vascular system in echinoderms
Class of echinoderms, commonly called starfish or sea stars, having a star-shaped body
with five radiating arms not sharply marked off from the central disc
Pertaining to cheek/mouth
Sea Lilies/feather stars: cup-shaped body with feathery arms, and areattached to the
substratum by a stalk in the case of sea lilies
Sea Urchins: have a typically globular body with skeletal plates fitting together to form a
rigid test
Mobile animals with the mouth directed towards the substrate
Sea cucumbers : marine with leatherly skin and an elongated body containing a single,
branched gonad
Area of echinoderm test between two ambulacral areas
Lateral Canal
Perpendicular branching of the radial canal leading to the tube feet
In echinoderms, a perforated plate at the end of the stone canal of the water vascular
system; links water-vascular system to outside
Class of echinoderms commonly known as brittle stars, having a star-shaped body with
the arms clearly marked off from the central disc
On the same side as the mouth (of radially symm. Animals such as echinoderms)
Any small bone or other calcified hard structure such as a plate of exoskeleton in
Hollow contractile pustules on epidermis of some echinoderms, such as starfish, having a
respiratory function
Minute pincer-like structures studding the surface of some echinoderms which grab, kill,
and discard small animals that touch them
Subphylum of Echinodermata: stalked and sedentary echinoderms
Foot or foot-like structure, such as a tube foot of echinoderm
Polian Vesicles
Interradial vesicles opening into ring vessel of ambulacral system of most starfish and
sea cucumbers; accessory (storage) fluid structures
Radial Canal
Radiate symmetrically from ring canal and run the length of the “arm”
Ventral surface of holothuroidea, where the ambulacral regions with tube feet are
Stone Canal
Cylindrical canal extending from madreporite to near mouth border in echinoderms
Tube Feet
Projections from the body wall in echinoderms which are connected to the water
vascular system and generally used for locomotion. They may also be modified to serve
respiratory food-catching and sensory functions
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2 distinct subphyla: Pelmatozoa (20K extinct, mostly dead), with crinoidea (sea lilies), deep water &
semi-sessile, suspension-feeders, mouth side facing upwards (20-50cm @ most in height)…. Mya ~20m
Secondary radial symmetry
pentametrous (5-ray)
Asteroidea sea stars (starfish) body shape relatively static
Ophiuroidea brittle stars, central disk much more clearly pronounced; arms move independently
Echinodidea sea urchins” globular, long to very short species
Holothuroidea sea cucombers, worm-like, epibenthic (move just above underwater surface)
Defensive strategy: EVICERATE (leave major organs behind) & regenerate/ make Cuvierian Tubules
(vesicles) made by gut which are slimy/sticky but harmless
Unique Features (5) (within invertebrate phyla)
Secondary Radial (or biradial) symmetry 5 arms around a central disc
Water-vascular “tube feet” (functional unit) – fluid-filled hydraulic system, separate from
perivasceral coelom
Pedicellariae minute pincer-like structures on outer surface of many members, almost completely
independent (were once thought ectoparasites); separate musculature
Dermal Branchiae (papulae) projections of the coelomic cavity with respiratory & excretory func.
Mesodermal Endoskeleton plates/ossicles, essentially Calcium carbonate support structures,
mesodermal in origin
Body Forms
Free-living have
bilateral symmetry
(most) adults
pentamerous (5-point)
radial symmetry
Cephalization absent,
no anterior/posterior;
only oral & aboral
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