Phylum Echinodermata

MCDOUGALL VIDEO CH. 13 – ECOLOGY AND ORGANIZATION OF BOGS

MCDOUGALL VIDEO CH 14 PREDATOR PREY 1 - ENEMONE

Porifera Platyhelmithes Mollusca Arthropoda Echinodermata Hemichordata Cnidaria Nemertea Annelida Lophophores Chordata Protozoans

Common Body Plan Adults are pentaradially symmetrical 5 sets of body parts around an oral-aboral axis 5

Common Body Plan However, larvae are bilaterally symmetrical Settle near adults of their species and attach to substrate Metamorphosis: left side becomes oral surface of the adult and right side becomes aboral (not oral) Larval mouth/anus disappear, gut migrates to adult position, and new mouth/anus open 6

Endoskeleton Unique system of calcareous plates (ossicles) – calcium carbonate Reduced in sea cucumbers Fused in sea urchins/sand dollars 7

Endoskeleton Skeletal elements bear pincer-like structures called pedicellariae Use to rid body of debris, defense, grasp objects to hide, or capture/hold prey 8

Water-vascular system Hydraulic system of canals and reservoirs controls the movement of tube feet (podia) Critical to locomotion, gas exchange (respiration), feeding, and sensory reception 9

Water-vascular system Water enters sieve plate (madreporite) Flows from stone canal to radial canals in each arm Lateral canals perpendicular to the radial canal terminate in muscular bulb (ampulla) connected to a tube foot 10

Water-vascular system Water enters bulb, it contracts and water forced into foot Extends foot, pressing terminal sucker onto substrate Foot contracts, forcing water back into bulb and raises center of sucker Creates a vacuum seal; only broken when bulb contracts water into foot again 11

Members of the Phylum Echinodermata Date back 570 million years ago 13,000 fossil species Only 7,000 species today Most are marine and benthic (90%) Range in size (<1cm to 2 m) 5 Classes 12

Phylum Echinodermata Radial symmetry No head or brain Spiny skin Water vascular system No excretory organs Deuterostome Bilateral lavrae

Class Asteroidea 1500 species of sea stars 5 or more broad arms surround a central disk Crawl on rocks or live on sea bottom Most are scavengers or predators Each arm bears podia with suckers Evert stomach into prey and digest it 14

Class Asteroidea Star Fish 5 or more tapering arms Mouth on underside Endoskeleton Ossicles Tube feet Feed on molluscs and sea urchins

Fig. 22.2a

Fig. 22.2b

Pedicellaria Spine Pedicellaria Dermal branchia

Class Asteroidea Tube feet and ambulacral groove Aboral surface

Aboral Surface Madreporite

Water vascular system Madreporite Stone canal Ring canal Tiedemann’s bodies Radial canal Lateral canal Tube feet Polian vesicles

Tube feet

Tube foot Ampulla Lateral canal Body wall Tube foot Retractor muscles Podial muscle Sucker

Movement of tube feet

Body Wall and Internal Anatomy of a Sea Star Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Body Wall and Internal Anatomy of a Sea Star 25

Fig. 22.3a

Feeding

Class Ophiuroidea Brittle Stars and Basket Stars Central disc with distinct arms No pedicellariae Tube feet lack suckers and ampulla

Class Ophiuroidea 2000 species of brittle stars Usually concealed in sand or under objects Some live in sponges or other colonial organisms Only 5 arms that are usually highly branched 29

Class Ophiuroidea Arms are distinct from central disk Can crawl/cling Predators, scavengers, or suspension feeders Flexible arms bear suckerless podia that secrete mucus to entrap food and transport it to mouth 30

Brittle star Mouth Bursal slit

Basket Star

Class Echinoidea Sea Urchins Shell (test) encloses body Ossicles form plates No arms Long spines Movement Venom

Class Echinoidea 1000 species of sea urchins/sand dollars Movable spines and podia surround body; used for locomotion Herbivorous, detrivorous, suspension feed, a few predators 34

Class Echinoidea Unique feeding apparatus called Aristotle’s lantern Hard plates and muscles just inside mouth Possesses 5 calcareous teeth Teeth protract to scrape algae off rocks or tear chunks of kelp 35

Internal Anatomy of a Sea Urchin Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Internal Anatomy of a Sea Urchin

Class Echinoidea Sand Dollar Burrow in sand

Sand dollar Gonopore Madreporite Ambulacral region Lunule

Class Holothuroidea Sea Cucumbers Soft body with reduced ossicles Tentacles near mouth Respiratory tree Breaths through anus

Class Holothuroidea 1150 species of sea cucumbers Mucus-covered oral tentacles trap on plankton or ingest sand organic matter Gut modified to produce respiratory trees used for gas exchange Expel portions of these trees as defense mechanism; regenerate 40

Fig. 22.Fig. 22a

Class Cridoidea Feather Stars and Sea Lilies Most primitive Feather like arms used for suspension feeding Plankton Tube feet trap planktonic organism Cilia in ambulacral grooves carry food to mouth

Attach to substrate with stalk Sessile sea lily Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Class Crinoidea: Sea Lily Attach to substrate with stalk Sessile sea lily Cup-like body attached to stalk Attached to substrate Can bend stalk and flex/extend arms

Class Crinoidea: Feather Star Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Class Crinoidea: Feather Star Swim and crawl

Class Crinoidea Free-moving feather star Stalk lost during larval development Can crawl/swim Jointed appendages (cirri) help it regain balance 45

Central disk Mouth Anus Pinnule

Ancestral Echinoderms

Ancestral Echinoderms