Phylum Echinodermata

Phylum Echinodermata (Echino = Prickly/ Spiny ; Dermata = Skin) Class Crinoidea (Feather Stars and Sea Lilies) Class Ophiuroidea (Brittle Stars and Basket Stars) Class Asteroidea (Sea Stars) Class Echinoidea (Sea Urchins and Sand Dollars) Class Holothuroidea (Sea Cucumbers)

Phylum Echinodermata Key characteristics of the Phylum: Echinoderms are all marine organisms Abandoned bilateral symmetry to become radial (only larvae is bilateral) – Pentaradial symmetry: five o multiples of five Deuterostomates Dermal endoskeleton of calcareous plates and spines often fused like an armor Water-vascular system that powers tiny tube feet for locomotion and food gathering Pedicellariae (pincer-like structures) – Except for Class Crinoidea -Keep the surface of the organism free of debris and small parasites. Dermal branchiae (skin gills) Slow locomotion Lack a defined head (cephalization): nervous and sensorial system poorly develop

Class Ophiuroidea (Brittle Stars and Basket Stars) Characteristics: Five arms articulated; distinct from central disk Most agile and most abundant of all echinoderms Autotomy Arms may be branched (basket stars) or unbranched (brittle stars) Arms lack open ambulacral groove Lack anus Active predators or deposit/ suspension feeders

Class Ophiuroidea External Anatomy – Phylum: Echinodermata Class Ophiuroidea- brittle starts

Class Asteroidea (Sea Stars) Characteristics: Body star-shaped with 5 or more arms Arms relatively thick; not distinct from central body disk Tube feet lie in open ambulacral grooves Gonads and digestive tract extend into arms Madreporite (opening to water vascular system)  Locomotion (15 cm/ min) and feeding Mostly predators, some are particle feeders Strictly bottom dwellers (benthic habitats) Diet: Includes molluscs, crabs, corals, and worms among other preys.

Class Asteroidea – Phylum: Echinodermata Clase Asteroidea- sea stars Asterias sp. External Anatomy central disk

Class Asteroidea – Phylum: Echinodermata Class Asteroidea- sea stars Asterias sp. Internal Anatomy Lateral canal

Sea Stars Larvae Brachiolaria Bipinnaria

Class Echinoidea (Sea Urchins and Sand Dollars) Characteristics: Body globular or disk-shaped; lack arms Skeletal plates fused into rigid test (or integument) Pores in test allow tube feet to exit Mostly herbivores or detritivores, but some predatory Spines moveable Jaw apparatus (Aristotle's Lantern)  Chewing food

Class Echinoidea External Anatomy – Phylum: Echinodermata Class Echinoidea- sea urchins

Internal Anatomy: Aristotle's Lantern

Class Echinoidea External Anatomy – Phylum: Echinodermata Class Echinoidea- sand dollars

Class Crinoidea (Feather Stars and Sea Lilies ) Sessile or free-moving, arms are used for locomotion and feeding Conserved evolution: similar looking to fossils going back to 500 mya Spines, madreporite, and pedicellariae are absent

Class Holothuroidea (Sea Cucumbers) Characteristics Elongated body No arms Endoskeleton reduced to isolated ossicles (calcified microscopic structures) Soft-bodied Ring of tentacles around mouth Most are deposit feeders, scavenging for debris in soft sediments (Benthic dwellers) Defense mechanism: Evisceration

Class Holothuroidea – Phylum: Echinodermata Class Holothuroidea- sea cucumbers Cucumaria External Anatomy

Class Holothuroidea Internal Anatomy – Phylum: Echinodermata Class Holothuroidea- sea cucumbers Cucumaria