Zool 110: Echinoderms and Other Deuterostomes (Lec 29)

deuterstomes

coelom develops by enterocoely, gill slits in the pharynx

1. xenoturbellida 2. ambulacriaria 3. chordates

what are the deuterostome groups

Xenoturbe

dueterostome group with unusual features

Ambulacrari

echinoderms + hemichordates

phylum chaetognatha

arrow worms, unknown evolutionary position, marine plankton, enterocoelous (kind of), eyes + sensory bristles, hermaphroditic and capable of self-fertilization

phylum chaetognatha anatomy

covered by cuticle, possess complete digestive system, well developed coelom, nerve ring, and sense organs

deuterostome development

mouth develops second, regulative development, enterocoelous formation of the coelom

phylum echinodermata

urchins, sea stars, sea cucumbers

Echinoderms

endoskeleton of large plates or small scattered ossicles, water-vascular system, tube feet, dermal branchiae, pentaradial symmetry in adults

1. crinoidea 2. asteroidea 3. ophiuroidea 4. echinoidea 5. holothuroidea

what are the 5 classes of echinoderms

Asteroids larval types

bipinnaria + brachiolaria

Echinoids larval types

echinopluteus

Ophiuroids larval types

ophiopluteus

Holothuroids larval types

Auricularia

Crinoids larval type

Doliolaria

Class Crinoidea

sea lilies and feather stars, sessile adults, stalk + holdfast, marine, arms with pinnules for filter feeding, ambulacral groove

ambulacral groove

A channel along the oral surface of echinoderms through which the tube feet protrude

Class Asteroidea

sea stars, 1500 species, predators of bivalves

Class Asteroidea Morphology

at least 5 arms, oral + aboral surfaces, tube feet in ambulacral grooves, madreporite = opening that allows water into water vascular system

water vascular system

madreporite allows water in, flows through stone canal to ring canal and then to the radial canals, then lateral canals, which connect with tube feet operated by ampullae

nerve ring

sea star nervous system

Class Asteroidea Reproduction

two sexes, usually external fertilization, indirect development, but some with direct

Class Asteroidea indirect development

bipinnaria larva --> brachiolaria larva --> metamorphosis --> juvenile sea star

Class Ophiuroidea

brittle stars and basket stars, five arms, respiration using gills, closed ambulacral grooves, tube feet without suckers so move by muscles in arm

Class Echinoidea

urchins and sand dollars, closed ambulacral grooves, spines present (no arms), tube feet and pedicellariae well developed, generally herbivores

Aristotle's lantern (Echinoi

complex mouthpart structure used for feeding

Class Holothuroidea

sea cucumbers, elongated oral-aboral axis, reduced ossicles, oral tentacles around mouth, respiratory tree off of cloaca, breathe through anus

pearlfish

makes its home in a sea cucumbers anus, commensalism

Phylum Hemichordata

acorn worms and pterobranchs, grouped with echinoderms to make up clade Ambulacraria because tornaria larva, gill slits show they are related to chordates