Lecture 14: Echinoderms

Question 1

Class Ophiuroidea (brittle stars)

Answer 1

Among the most abundant and diverse, around 2000 species, abundant in rocky and sandy habitats in fairly deep seafloor (100-200m)

Question 2

Madreporite

Answer 2

Four-five plates surround the ventral mouth = JAWS, one of them holds the madreporite

Question 3

Bristle star tube feet

Answer 3

reduced for assisting feeding only (not for movement)
-they are a scavenger species

Question 4

Brittle Stars reproduction

Answer 4

Sexual: Adults spawn gametes, egg external fertilization, hatch larvae and settle juvenile
Asexual: High regeneration capacity, can regrow arm and parts of the central disk

Question 5

Autotomy

Answer 5

Cut/release body parts to escape predators

Question 6

Class Echinoidea (urchins and sand dollars)

Answer 6

About 2000 species, 5 arms disappear, round disk is left, grooves with podia remain visible
Visceral organs are now in central disk, gonads on top, digestive glands below
Ossicles become larger and fused

Question 7

Sea Urchins

Answer 7

Spines become long and movable (defence) Locomotion is still based on podia (tube feet)

Question 8

Sea Urchins feeding and living

Answer 8

Live on hard substrates, they’re omnivores but mostly herbivores.

Question 9

Aristotle’s Lantern

Answer 9

Chewing organ, 4-5 teeth and a jaw apparatus used to scrape algae.

Question 10

The role of sea urchins

Answer 10

-urchin barrens in rocky shores and kelp forests
-Diadema urchins control seaweeds on coral reefs

Question 11

Sand dollars

Answer 11

live in soft bottoms
Flat shape with reduce movable spines, use their spines to move their food toward their mouth
-deposit feeders so the aristotle’s lantern is reduced

Question 12

Reproduction of echinoidea

Answer 12

Primarily sexual
Mature urchins/sand dollars
externally fertilized
hatching planktonic larvae, those become juveniles

Question 13

Class Holothuroidea Sea Cucumbers

Answer 13

Sea Cucumber, 1000 species, many in deep species, oral-aboral axis lengthened with tentacles around the mouth.
CaCO3 ossicles are now reduced so the body is soft with a thick dermis
Five grooves with tube feet are still visible along the body, tube feet are used for slow locomotion

Question 14

Holothuroidea (sea cucumber) feeding

Answer 14

Tentacles around the mouth are highly mobile and used for feeding
Aristtoltle lantern has been lost
Scavengers

Question 15

Holothuroidea Reproduction

Answer 15

Sexual Reproduction: Production of eggs, external fertilization, hatch larva, settling of a juvenile

Question 16

Class crinoidea

Answer 16

Feather stars, sea lilies
Mouth and anus face upward
Madreporite and aristotles lantern lost
Five grooves are dorsal and associated with tentacles

Question 17

Feather star and sea lilie feeding

Answer 17

Filter feeding: tentacles move the water and have mucus and help to trap food

Question 18

Crinoidea (sea lilies and feather stars) repoduction

Answer 18

Sexual: External fertilization
asexual reproduction: high regenration capacity