Phylum Echinodermata Flashcards
Where can Class Asteroidea be found?
-along shorelines and may aggregate on rocks
-some live on muddy or sandy bottoms or coral reefs
Describe the form and function of Class Asteroidea
-flattened body and flexible
-pigmented and ciliated epidermis
-aboral surface covered with spines
-pedicellariae at bases of spines
What is Papulae
-soft projections lined with peritoneum
-respiratory gases and ammonia diffuse across the papulae and tube feet
What are coelomocytes
pick up wastes and migrates to exterior
Describe the internal anatomy of class Asteroidea
-large body cavity - one coelomic compartment filled with fluid
-fluid contains amoebocytes
-circulation via ciliated peritoneal lining of coelem
-fluid circulates around internal organs and into papulae
Describe the mesodermal endoskeleton of the class Asteroidea
-small calcareous plates (ossicles) bound together by an unusual form of mutable collagen
-ossicles penetrated by meshwork of spaces filled with fibers and dermal cells (stereom)
-This system is a second coelomic compartment
-System of canals, tube feet, and dermal ossicles
-Functions in locomotion, food-gathering, respiration, and excretion
-Opens to outside at madreporite on aboral side
Water-Vascular System
Water-Vascular System
-Opens to outside at madreporite on aboral side
-Madreporite > stone canal > ring canal that encircles the mouth
-Radial canals diverge from ring canal and extend into each ray
4 or 5 pairs of Tiedemann’s bodies attach to ring canal and may produce coelomocytes
Feeding and Digestive System of class Asteroidea
-mouth>short esophagus > large double stomach
-some lack intestine and anus
Reproductive System of class Asteroidea
-Sexes separate in most
-Paired gonads in each interradial space
-External fertilization
Regeneration of Class Asteroidea
-Cast off injured arms and regenerate new ones - autotomy
-An arm can regenerate a new sea star if at least one-fifth of central disc is present
Class Ophiuroidea
-live on hard or sandy bottoms where little light penetrates
-browsers and suspension feeders
-regeneration and autonomy more pronounced than in sea stars
Describe Class Echinoidea
-Lack arms but their tests show five-part symmetry
-Ambulacral areas folded up to area of the anus
-Most with hemispherical shape, radial symmetry and long spines
-Regular urchins move by tube feet
Irregular urchins move by their spines
-Echinoids occur from intertidal regions to deep ocean
-Spines articulate on “ball-and-socket” joints moved by small muscles at the bases
-Some species have pedicellariae with poison glands - toxin paralyzes small prey
Class Echinoidea
Complex set of chewing structures of Class Echinoidea
Aristotle’s lantern
Describe Class Holothuroidea
-Greatly elongated in the oral-aboral axis
-Ossicles greatly reduced and body is soft
-Some species crawl on the ocean bottom, others are found under rocks or burrow
-Body wall leathery with microscopic ossicles embedded
-In some, locomotor tube feet are distributed to all five ambulacral areas
Most have them only on the ambulacra that faces the substratum (sole)
All tube feet, except oral tentacles, absent in burrowing forms
Class Holothuroidea
Describe Digestive and Excretory of Class Holothuroidea
-Digestive system and respiratory tree opens into a cloaca
-Madreporite lies free in the coelom
-Respiratory tree also serves for excretion
-Gas exchange also occurs through the skin and tube feet
Describe Feeding/Defense of Class Holothuroidea
-Some trap particles on the mucus of tentacles
-Others graze sea bottom with tentacles
-Cast out part of viscera when irritated
-Sticky and have toxins
-Must regenerate these tissues
Describe Class Crinoidea
-Sea lilies have a flower-shaped body at tip of a stalk
-Feather stars have long, many-branched arms
-Have primitive characters
-More numerous in fossil record
-Unique feature – sessile
-Many crinoids are deep-water species
-Feather stars are found in more shallow water
Describe Form of Class Crinoidea
-Body disc or calyx covered with a leathery skin or tegument of calcareous plates
-5 arms branch to form more arms, each with lateral pinnules
-Calyx and arms form a crown
-Stalk (if present) formed of plates
-Madreporite, spines, and pedicellariae absent
Describe Function of Class Crinoidea
Oral surface with mouth that opens into esophagus and intestine
Ambulacral grooves with tube feet (podia) extend from mouth along arms and pinnules
Has a water-vascular system, an oral ring, and a radial nerve to each arm
