Echinoderms Flashcards
What are phylum Echinodermata united by?
Presence of a water vascular system
What is the age range of phylum Echinodermata?
Cambrian to recent
What is the Stereom?
Mesodermal calcitic skeleton
(middle layer of cells)
What is the symmetry of Enchinodermata?
Typically 5 fold Pentameral symmetry
Besides pentameral symmetry what other symmetry might be present in Echinodermata?
Superimposed bilateral symmetry
What is the diversity of echinodermata like?
Diverse group with wide variety of exclusively marine ecological niches
What 2 subphylum can Echinodermata be divided into?
Pelmatozoa
Eleutherozoa
What are some examples of Subphylum Eleutherozoa?
Holothurians (sea cucumbers)
Asteroid starfish
Ophioroids (brittle stars)
What are some examples of echinoidea from Subphylum Eleutherozoa
Sea urchins and Sand dollars
What is the upper view of an echinoidea called?
Aboral
What main central feature of Echinoidea can be seen in aboral view?
Apical disc
What is the apical disc?
Area which contains the periproct (anus)
What is the periproct surrounded by?
5 plates with large pores (gonopores)
What makes one plate surrounding the periproct different?
Madreporite which is a different colour - imporant for water filtering
How is the pentameral symmetry of regular echinoidea defined?
10 pairs of ambulacrum plates
What are ambulacral plates?
penetrated pores through which tube feet emerge
What are interambulacral plates?
Where there are no pores in aboral view
What is the function of tubercles?
the channel water flow and act as basal support for the spines
What are the 2 general sizes/ function of spines on echinoidea?
long spines for protection
short spines for locomotion
What is the name of the lower view of echinoidea?
adoral
What can be viewed in the centre of a regular echinoidea in adoral view?
Peristome - mouth
What can also be seen in adoral view of a regular echinoidea besides the peristome?
Aristotle’s lantern
Perignathic girdle
What is Aristotle’s lantern?
5 jaws used for feeding
What is the perignathic girdle?
ring of plates which surrounds the peristome
What feature located near aristotles lantern can be viewed internally?
Gill notches
What is the function of gill notches in echinoderns?
Allow water to enter the test
What is the test in echinoderns?
The skeleton
What is located underneath the madreporite?
Stone canal
What is the function of the stone canal?
part of water vascular system connecting madreporite with circum oral-ring
What does the circum oral-ring connect to and why is it important?
Connects to the radial water vessel which connects to ampullae which when then contract and expand extent or retract the tube feet
What is the mode of life of regular echinoids?
mobile
epifaunal
grazers
or active predators
What is the difference as you transition from regular to irregular echinoids?
Flattening of test
Elongation of test
Decrease in size of spines and tubercles
Increase in number of spines and tubercles
Anus shifts posteriorly
Peristome shifts anteriorly
Decrease in size of peristome
What is the reason for the difference between irregular and regular echinoids?
Secondary bilateral symmetry
What is the mode of life of irregular echinoids?
mobile
infaunal
burrowers
What is an example of the transition of an echinoid from regular to irregular? (Jurassic)
Diademopsis (hettagenian)
Pygaster (Sinemurian)
Pileus (Mid- late Jurassic)
What is the main organism of the subphylum pelmatozoa?
Crinoidea
What is the age range of crinoidea?
Early Ordovician to recent
What is the fossil record and relative abundance like for Crinoidea?
Largest group of echinoderms in fossil record
Extremely common in certain facies in Palaeozoic
What is the holdfast for crinoidea?
The attachment / foot structure
What is the stem of crinoids made up of?
columnals or ossicles (polo mint like features)
What is the caylx in crinoids?
cup-shaped central portion that lies below the oral surface, which is oriented away from the substrate
What extent off from the caylx?
Branching arms
What name is given to the lower part of the caylx?
The cup
What are the parts of the cup from lower to higher?
Infrabasals
Basals
Radials
What is the the top of the caylx called?
Tegmen
What is the position of the mouth and anus in the tegmen?
Centrally located mouth
Laterally located anus positioned on raised anal pyramid
What are the feeding arms of crinoids divided into?
Brachial plates
And
Pinnules
What are pinnules in crinoids?
Contain the reproductive organs and carry numerous tube feet with sensory functions
Very fine
What is a rheophilic mode of life?
Current seeking to filter feed feed from water column
What is an example of a rheophobic crinoid?
Uintacrinus
What is a rheophobic mode of life?
current avoiding
What is the decapitation mode of life for crinoids?
When the head is removed nutrient and food are absorbed through the skin
What is an example of comatulid crinoids?
Antedon - highly mobile also able to swim
What is a fossil example of a comatulid crinoid?
Saccocoma (Jurassic) benthic
What characteristic of the crinoids make them have a good fossil record?
calcitic skeleton means abundant fossil record
e.g. crinoidal limestones
What type of hydro environment do all echinoderms live?
Normal marine salinity (stenohaline) in only fully marine sediments
