Holothuroidea- Sea Cucumber

Echinoidea – Sea Urchins

Collecting Echinoidea – Sea Urchins

Asteroidea – Sea Star

http://www.freeyellow.com/members5/silentworld/gallery1.html

Ophiuroidea – Brittle Star

Crinoidea – Feather Star

http://search.corbis.com/default.asp?i=10615886&vID=1&rID=101

Star showing ambulacral grooves

General structure of water vascular system

http://www.howe.k12.ok.us/~jimaskew/watervas.gif

Podia (tube feet)

• Arm of sea star

• Note ambulacral groove

Body

• Crown bears mouth on upper surface near its center. The anus is also on the oral surface in an interradius.

• Margin of calyx bears freely movable arms - usually 5. Ambulacral grooves run from the 5 corners of the mouth across the calyx and up each arm.

Crinoid arm

• The arms are subdivided into 10-30 branches usually (up to 200!). Food grooves are located along the arms .

• The arms contain brachial ossicles and usually carry (in living forms) lateral appendages called pinnules which function in food capture and bear the reproductive glands. 

Crinoidea

• The sea lilies are stalked. Feather stars have no stalk as adults, but are sedentary and attach to rocks and corals by means of clawlike cirri at their base.

Internal transport, gas exchange and excretion

• Gas exchange through podia and dermal papulae.

• Coelomic fluid contains coelomocytes (phagocytic and may function in carrying food material to other cells).

 Nutrition • Food goes from mouth

--> short esophagus --> large stomach which fills most of interior of disk and is divided into large oral chamber, the cardiac stomach, and smaller flattened aboral chamber, the pyloric stomach --> digestive glands (a pair in each arm --> short intestine-> anus

From Rupert and Barnes, 1994, Invertebrate Zoology, ISBN 0 – 03– 026668 -- 8

Star larvae

Digestion

• Gut originally sent digestive glands to arms as in stars (gonads here also). Still found in 1 group. Now digestive glands gone from arms and gonads are in disk region on lower side of disk

• Mouth used for ingestion and egestion. NO ANUS.

Diagram copied from Rupert and Barnes, 1994

Ophiuroid ophiopleuteus larva

ECHINODERMATA Class Echinoidea

• Long-spined black urchin (Diadema antillarum) from Roatan, Honduras

• Long, thin, hollow spines are venomous

• Populations, once decimated by a blight, now recovering

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display

Photo Copyright © Diane R. Nelson

Class Echinoidea

• Includes sea urchins sand dollars and their relatives.

• Range in size from a few mm to 20 cm. Found in all seas from low tide down (over 5 miles).

Sand dollar. Aboral surface

Oral surface

Class Echinoidea• They have well developed jaws =

Aristotle's lantern" and feed mainly on algae and small molluscs

• Use spines for locomotion (tube feet for ascending vertical surfaces and anchors). Spines can turn in all directions.

• 5 double rows of tube feet meridionally arranged. No open grooves. http://eebweb.arizona.edu/globe/echinobio.htm

Class Echinoidea• Five pairs of shrub-like appendages

(gills) for gas exchange. Similar to dermal papulae of stars.

• Test of plate-like ossicles firmly fitting together.

• Nervous system and water vascular system typical, but have balance organs. This and next few pictures from:

http://www.stanford.edu/group/Urchin/anaphys.html

Class Echinoidea• Aboral view of the test of the

sea urchin showing the anus in the center, five gonopores and the.

• The madreporite is used to help maintain proper pressure in the water vascular system so that the tube feet can be properly operated.

Class Echinoidea• Digestive system is tubular.

Esophagus --> stomach which runs in counter clockwise coil (from above) --> intestine (reverses route --> anus.

• Part of the intestine is segregated as a ciliated tube which runs from the beginning of the intestine to the end and carries surplus fluids directly to the rectum without diluting digestive broth in main intestine.

Class Echinoidea• Reproduction. Dioecious,

typical. Larva = echinopluteus. No attached stage. metamorphose in 1 hr. on the bottom.

http://www.imagequest3d.com/catalogue/larvalforms/

ECHINODERMATA Class Holothuroidea

• When disturbed, this eyed sea cucumber (Bohadschia argus) discharges its tubules of Cuvier from the cloacal opening

• These sticky, toxic threads are used for defense

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display

Photo Copyright © Diane R. Nelson

• There are10 tentacles around the mouth which are modified first tube feet from each ambulacrum. These branch and appear tree-shaped. They are highly sensitive and contractile.

• The pair opposite the mid-ventral ambulacrum is smaller than the others and used to push food particles into the mouth.

• All the tentacles can be withdrawn into the mouth when the animal is disturbed.

http://tolweb.org/tree?group=Holothuroidea&contgroup=Echinodermata

ECHINODERMATA Class Holothuroidea

• Graeff’s sea cucumber (Bohadschia graeffei) from the Great Barrier Reef in Australia

• Black pads are modified tentacles for feeding in sediment

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display

Photo Copyright © Diane R. Nelson

Class Holothuroidea

•  Respiratory trees. = pair of tubular organs, each a single stem which branches. Used as respiratory, excretory and hydrostatic organs operated by the pumping action of the cloaca.

http://tolweb.org/tree?group=Holothuroidea&contgroup=Echinodermata#TOC2

Class Holothuroidea

•  Respiratory trees. = pair of tubular organs, each a single stem which branches. Used as respiratory, excretory and hydrostatic organs operated by the pumping action of the cloaca. http://tolweb.org/tree?group=Holothuroidea&contgroup=Echinodermata#TOC2