kingdom animalia phylum echinodermata
DESCRIPTION
KINGDOM ANIMALIA Phylum Echinodermata. Members of the Phylum Echinodermata. Date back 570 million years ago 13,000 fossil species Only 7,000 species today Most are marine and benthic (90%) Range in size (TRANSCRIPT
KINGDOM ANIMALIAPhylum Echinodermata
Members of the Phylum Echinodermata
Date back 570 million years ago
13,000 fossil species
Only 7,000 species today
Most are marine and benthic (90%)
Range in size (<1cm to 2 m)
5 Classes
Common Body Plan
Adults are pentaradially symmetrical
5 sets of body parts around an oral-aboral axis
Common Body PlanHowever, larvae are bilaterally symmetricalSettle near adults of their species and attach to
substrateMetamorphosis: left side becomes oral surface of
the adult and right side becomes aboralLarval mouth/anus disappear, gut migrates to adult
position, and new mouth/anus open
Endoskeleton
Unique system of calcareous plates (ossicles)
Reduced in sea cucumbersFused to form a solid test in
sea urchins/sand dollars
Endoskeleton
Skeletal elements bear pincer-like structures called pedicellariae
Use to rid body of debris, defense, grasp objects to hide, or capture/hold prey
Water-vascular system
Hydraulic system of canals and reservoirs controls the movement of tube feet (podia)
Critical to locomotion, gas exchange, feeding, and sensory reception
Water-vascular systemWater enters sieve
plate (madreporite)Flows from stone
canal to radial canals in each arm
Lateral canals perpendicular to the radial canal terminate in muscular bulb (ampulla) connected to a tube foot
Water-vascular systemWater enters bulb, it
contracts and water forced into foot
Extends foot, pressing terminal sucker onto substrate
Foot contracts, forcing water back into bulb and raises center of sucker
Creates a vacuum seal; only broken when bulb contracts water into foot again
Classification
There are 6 classes of echinoderms
5 classes are described on the following slides
Class Crinoidea
Most ancient/primitive625 speciesBase of 5 or 10 arms that can branch
up to 200 armsSuspension feedersEach arm bears suckerless podia
that produce mucus to capture detritus and transport it to mouth
Class Crinoidea
Sessile sea lilyCup-like body
attached to stalkAttached to
substrateCan bend stalk
and flex/extend arms
Class Crinoidea
Free-moving feather star
Stalk lost during larval development
Can crawl/swimJointed
appendages (cirri) help it regain balance
Class Asteroidea1500 species of sea
stars5 or more broad arms
surround a central diskCrawl on rocks or live
on sea bottomMost are scavengers
or predatorsEach arm bears podia
with suckersEvert stomach into
prey and digest it
Class Ophiuroidea
2000 species of brittle stars
Usually concealed in sand or under objects
Some live in sponges or other colonial organisms
Only 5 arms that are usually highly branched
Arms are distinct from central disk
Can crawl/clingPredators,
scavengers, or suspension feeders
Flexible arms bear suckerless podia that secrete mucus to entrap food and transport it to mouth
Class Ophiuroidea
Class Echinoidea1000 species of sea urchins/sand dollarsMovable spines and podia surround
body; used for locomotionHerbivorous, detrivorous, suspension
feed, a few predators
Class Echinoidea
Unique feeding apparatus called Aristotle’s lantern
Hard plates and muscles just inside mouth
Possesses 5 calcareous teeth
Teeth protract to scrape algae off rocks or tear chunks of kelp
Class Holothuroidea1150 species of sea
cucumbersMucus-covered oral
tentacles trap on plankton or ingest sand organic matter
Gut modified to produce respiratory trees used for gas exchange
Expel portions of these trees as defense mechanism; regenerate