Echinodermata

Question 1

what are the key characteristics of deuterostomes?

Answer 1

radial cleavage
secondary mouth - not formed by anus
three part enterocoelic coelom
dipleurula-type larvae

Question 2

basic features of echinoderms?

Answer 2

trimeric coelom
deuterostome development 
biradial symmetry in larva
pentaradial symmetry in adults 
calcareous endoskeleton
water vascular system

Question 3

describe the skin of echinoderms?

Answer 3

endoskeleton
ciliated epidermis forms thin mucoid skin
spines
papulae
pedicellaria
ossicles - calcium carbonate crystal hollowed into a lattice, laced together with collagen

Question 4

what are spines used for?

Answer 4

digging, walking, paddle, defence

Question 5

what are pedicellariae?

Answer 5

jaws often with toxins

used for defence, cleaning, and food capture

Question 6

characteristics of tube feet?

Answer 6

project downwards from main radial pipe
ampullae connected laterally to main piping
ambulscral grooves run along underside of each arm

Question 7

what are tube feet used for?

Answer 7

locomotion, respiration, feeding, sensitivity

Question 8

what is the water system?

Answer 8

closed hydrostatic - uses pipes - a central ring plus a pipe up each arm and a single connection to outside world via madreporite

Question 9

reproduction in echinoderms?

Answer 9

mass spawning or asexual regeneration

Question 10

key absences in echinoderms?

Answer 10

no real CNS - simle 5 -rayed nerve net at base of epithelium
no distinct excretory system
weird connective tissue - contractile and changes mechanical properties in response to nerve stimulation - energy catch/saving

Question 11

key features of asteroidae?

Answer 11

starfish/sea stars
usually 5 arms (can be other odd numbers)
mainly sitting substratum in inshore waters
arms have ventral ampullae and large coelom containing parts of gut/gonads
respire by thin papulae

Question 12

how do asteroidae move?

Answer 12

stepping action of coordinated tube feet, with ampullae providing the extrusion force
more complex nerve plexus than in other classes which is used to provide stepping coordination
no one leg leads consistently

Question 13

how do asteroidae feed?

Answer 13

tube feet provide suction over long period of time until mussel finally opens slightly and stomach of starfish exterted and pushed into gap where it extrudes enzymes that turn the mussel into gloop

Question 14

why do starfish matter?

Answer 14

depeltion of mussel beds in temperate areas

crown-of-thorns sea star is a major problem, grazing coral reefs

Question 15

key characteristics of ophiuroidea?

Answer 15

brittle stars/basket stars

central disc with five thin arms - sometimes subdivided to make a basket-like arrangement

Question 16

how do ophiuroids feed?

Answer 16

they're scavengers 
abundant on ocean floor as 'hoovers'
arms move decaying matter into mouth 
few carnivores
lack anus

Question 17

how do ophiuroids move?

Answer 17

use each arm as a limb/lever

ossicles large and articulated so act like vertebrae

Question 18

how do ophiuroids breathe?

Answer 18

via 5 bursae projecting into the coelom from ventral disc, between the arms

Question 19

key features of echinoidea?

Answer 19

no arms but still pentandrical with five rows of tube feet
ossicles fused to make a complete test
some irregular - show pentamery but also bilateral

Question 20

how do echinoidea move?

Answer 20

stout surface spines will ball and socket joints
spines can act as legs
some role for ventral tube feet which have ampulla

Question 21

how do echinoidea eat?

Answer 21

graze on coral/algae using ventral aristotles lantern - a complex array of five articulated teeth and muscles

Question 22

how do echinoidea breathe?

Answer 22

occurs all over general body surface

Question 23

general features of holothuroidea?

Answer 23

appear bilateral - cylindrical
5 rows of tube feet and terminal tentacles
no spines, ossicles small and separate - soft

Question 24

how do holothuroidea move?

Answer 24

using 2-3 ventral rows of tube feet and sometimes worm-like hydrostatic burrowing

Question 25

how do holothuroidea eat?

Answer 25

using tentacles to sweep over substratum and pick up food

Question 26

how do holothuroidea breathe?

Answer 26

by internal branching - lung like in structure - at rear of body from cloaca

Question 27

general features of crinoidea?

Answer 27

most ancient class - pre-Cambrian - mostly extinct
mouth points upwards
may be up to 200 arms supported by internal ossicles
most stalked and attached to substratum

Question 28

how do crinoidea move?

Answer 28

if stalked they don’t

free-floating ones flap arms or ‘snowshoe’ along substratum w/ basal arms

Question 29

how do crinoidea eat?

Answer 29

filtering - pinnules on arms flick food to midline, where tiny ciliated tube feet make a fine filter and transfer particles to food groove leading to mouth

Question 30

what is concentricycloidea?

Answer 30

sea dasies - new-ish class
flattened disc, armless, lives in rotting wood like piers

Question 31

why are echinoderms weird?

Answer 31

adults pentamerous while larvae bilateral
weird skeleton - no nervous system - head/anterior
catch system - stiff to fluid
any arm can lead
large size but no real closed blood system
never pelagic or parasitic

Question 32

what is the traditional view regarding phylogeny?

Answer 32

became radial as became more sessile

crinoids basal, then echinoideas and holothurideas and then sea stars and brittle stars

Question 33

what is the view based on development?

Answer 33

deuterostomes
crinoids - most primitive
e/h - sister groups
asteroids/ophiuroids - closely related