Class Ophiuroidea ( ophiuroid ), Class Echinoidea ( sea urchin ) and the sand do
ID: 262939 • Letter: C
Question
Class Ophiuroidea (ophiuroid), Class Echinoidea (sea urchin) and the sand dollar Dendraster excentricus, Class Holothuroidea (sea cucumber), "apodan" cucumber Leptosvnapta sp.
Where are the ambulacra on each organism?
What shape are the tube feet? Do they have suckers? How does the animal use its tube feet?
What are the extents of the oral and aboral surfaces on each animal?
Whic classes of echinoderms are rigid and which are flexible? How do their skeletal systems differ?
What do their various animals eat? How do they obtain their food? Where is the mouth? What are the characteristics of the digestive system of each class?
Thank you!
Explanation / Answer
Characteristics
Class Ophiuroidea
(Ophiuroid)
Class Echinoidea
(Sea urchin, sand dollar etc)
Class Holothuroidea
(Sea cucumber, apodan cucumber)
ClassAsteroidea
(Asterias)
Ambulacra grooves (water vascular system derived from coelom)
closed
Closed
closed
Open –extends up to the end of the arms
Tube feet (locomotion, food collection, gas exchange and excretion)
Highly reduced
five double rows of tube feet run from the apex down the sides. Helps in locomotion
Five double rows of tube feet run along the body. used for crawling or anchoring to a rock.
Well developed
suckers
Tube feet without suckers
Absent
absent
Tube feet well developed with suckers
digestive system
No anal organ and intestine.
Mouth acts as an anal organ to excrete.
These are scavengers or detritivores. Some feed on small crustaceans or worms
Mouth contains Aristotle’s lantern -Complex chewing apparatus.
The lantern is made up of five jaws. The mouth leads to the intestine and anal organ, which is located in the center of the upper surface in regular echinoids. The anal organ is either posterior or on the oral surface. Spines and tube feet present around the peristome function in locomotion, burrowing, and food-gathering.
Called as algivores - feed on seaweeds, grasses and encrusting algae
the pharynx lies behind the mouth and is bordered by ten calcareous plates.
These are generally scavengers, feeds on debris in the benthic zone of the ocean
Mouth leads to the lower cardiac stomach and upper pyloric stomach. Pyloric stomach connects with digestive caeca located in each arm. Short intestine connects from stomach to the anal organ on the upper side
Skeletal system
Possess very long flexible arms arising from the central disc and helps in movement. Arms can break easily, hence called brittle stars. These arms can get regenerate rapidly
possess an internal skeleton made of calcitic ossicles (plates)
These are flexible. calcareous plates (ossicles) that compose the skeletal system are very small and widely isolated. Thick sheets of body wall muscles provide support.
The upper surface may be smooth, pointy, or covered with overlapping calcareous plates.
Characteristics
Class Ophiuroidea
(Ophiuroid)
Class Echinoidea
(Sea urchin, sand dollar etc)
Class Holothuroidea
(Sea cucumber, apodan cucumber)
ClassAsteroidea
(Asterias)
Ambulacra grooves (water vascular system derived from coelom)
closed
Closed
closed
Open –extends up to the end of the arms
Tube feet (locomotion, food collection, gas exchange and excretion)
Highly reduced
five double rows of tube feet run from the apex down the sides. Helps in locomotion
Five double rows of tube feet run along the body. used for crawling or anchoring to a rock.
Well developed
suckers
Tube feet without suckers
Absent
absent
Tube feet well developed with suckers
digestive system
No anal organ and intestine.
Mouth acts as an anal organ to excrete.
These are scavengers or detritivores. Some feed on small crustaceans or worms
Mouth contains Aristotle’s lantern -Complex chewing apparatus.
The lantern is made up of five jaws. The mouth leads to the intestine and anal organ, which is located in the center of the upper surface in regular echinoids. The anal organ is either posterior or on the oral surface. Spines and tube feet present around the peristome function in locomotion, burrowing, and food-gathering.
Called as algivores - feed on seaweeds, grasses and encrusting algae
the pharynx lies behind the mouth and is bordered by ten calcareous plates.
These are generally scavengers, feeds on debris in the benthic zone of the ocean
Mouth leads to the lower cardiac stomach and upper pyloric stomach. Pyloric stomach connects with digestive caeca located in each arm. Short intestine connects from stomach to the anal organ on the upper side
Skeletal system
Possess very long flexible arms arising from the central disc and helps in movement. Arms can break easily, hence called brittle stars. These arms can get regenerate rapidly
possess an internal skeleton made of calcitic ossicles (plates)
These are flexible. calcareous plates (ossicles) that compose the skeletal system are very small and widely isolated. Thick sheets of body wall muscles provide support.
The upper surface may be smooth, pointy, or covered with overlapping calcareous plates.