Exercise 9 - Echinodermata

• Echinoderms are named after their endoskeleton of spiny calcareous ossicles. Unique to echinoderms is the water vascular system which extends throughout their bodies as a series of canals and tubes.
• Another unique feature of echinoderms is the presence of mutable connective tissue which allows the body walls of these animals to undergo rapid and reversible changes in stiffness.
• What are the five classes under Phylum Echinodermata?

  Crinoidea, Asteroidea, Ophiuroidea, Echinoidea, and Holothuroidea
• Class Crinoidea (feather stars) – mouth and anus oriented towards surface, arms with ciliated grooves.
• Class Asteroidea (starfish) – typically five arms broadly connected to central disc, madreporite and anus on aboral side, ambulacral grooves open.
• Class Ophiuroidea (brittle stars) – five arms distinctly marked off from central disc, arms with interlocking “vertebrae”, madreporite on oral side, no anus, ambulacral grooves closed.
• Class Echinoidea (sea urchins and sand dollars) – ossicles fused into a rigid test with spines, closed ambulacral grooves extending from oral to aboral side.
• Class Holothuroidea (sea cucumbers) – elongation of oral-aboral axis, reduction of ossicles, oral podia modified into tentacles.
• Class Asteroidea

  • Archaster - This small starfish is found in sandy areas.
• Class Asteroidea

  • Linckia (Pacific blue starfish) - This starfish is very common in Philippine coral reefs. When alive, it is usually bright blue although some variants are pink or yellow.
• Class Asteroidea

  • Acanthaster (crown-of-thorns starfish) - This starfish typically has numerous arms and is named after its sharp venomous spines found all over the aboral surface of this animal. It is a voracious predator of corals and outbreaks of this species can seriously decimate coral populations.
• Class Ophiurioidea

  • Brittlestars - are often found in coral and seagrass areas but are hardly seen because of their cryptic nature.
• Class Ophiurioidea

  •  Brittlestars have the ability to cut off their arms (autotomy) when handled.
• Class Echinoidea

  • Echinometra (burrowing sea urchin) - This small sea urchin is usually found in between rocks in coral reefs and has greenish brown spines when alive.
• Class Echinoidea

  • Tripneustes - This species is commercially harvested for its gonads (roe) which are served as sushi in Japanese restaurants. It has numerous thin white and orange spines that are separated by areas of pedicellaria.
• Tripneustes uses pedicellaria to pick up algae fronds, rubble, and sea grass blades to cover its body for camouflage.
• Class Ophiuroidea

  • Diadema (long-spined sea urchin) - This sea urchin is ubiquitous in coral and seagrass areas and has very long sharp black spines. A swimmer unlucky enough to step on this sea urchin will have a quite painful experience. Injuries resulting from this species can be treated with ammonia.
• Class Ophiuroidea

  • Sea urchin test - The test of a sea urchin is made up of many plates that are fused together. The plates in between the ambulacral regions are called interambulacral plates.
• Class Ophiuroidea

  • Sand dollar (Laganum and Arachnoides) - Sand dollars have a flattened test with very short spines and are specialized for burrowing in the sand. Some sand dollars such as Laganum have two openings on the oral side: the peristome, which houses the mouth and the periproct or anus, which is located near the margin; thus, making this species secondarily bilateral.
• Class Holothuroidea

  • Holothurian (black sea cucumber) - This sea cucumber is edible and served as a delicacy known as beche-de-mer or trepan
• Class Holothuroidea

  • Synapta - This sea cucumber lives in coral and seagrass areas and is often mistaken at first glance by snorkelers as a sea snake because of its very long body. Tentacles are quite prominent in this animal.
• Class Crinoidea

  •  Feather stars - are found in coral reef sloped where they can capture food using their feathery arms. Unlike other classes of echinoderms, feather stars have a mouth and anus oriented towards the surface
• Identify the genus and class of the species below. What symmetry do their larvae exhibit?

  Genus: Linckia, Class Asteroidea

  Symmetry: Bilateral Symmentry

  
• What is class does the species below belong?

  Class (Holothrudoidea) - Holothuria

  
• What genus and class does the picture below belong?

  Diadema, Class Echinoidea

  
• What genus and class does the picture below belong?

  Tripneustes, Class Echinoidea

  
• What class does the picture below belong?

  Class Echinoidea

  
• What species does the picture below belong?

  Echinometra sp.

  
• What species and which class does the picture below belong?

  Protoreaster sp. Class Asteroidea

  
• In what class does the picture below belong?

  Class Ophiuroidea