Deuterostomes

Flashcards covering the key concepts of Deuterostomes, Hemichordates, and Echinoderms, including their characteristics and classes.

Bilateria

Animals with bilateral symmetry, generally triploblastic, and generally with a complete digestive tract.

Protostomes vs. Deuterostomes

Protostomes develop the mouth first during gastrulation, while deuterostomes develop the anus first.

Deuterostomes Characteristics

Triploblastic, blastopore becomes the anus, and coelomates.

Main Phyla of Deuterostomes

Echinoderms, Hemichordates, and Chordates.

Coelom

An internal cavity full of fluid, lined with peritoneum.

Characteristics of Ancestral Deuterostomes

Bilateral symmetry, external gills, and ancient fossils (~520 Ma).

Hemichordates (Hemichordata)

Bilateral symmetry and include two classes: Enteropneusta (acorn worms) and Pterobranchia.

Enteropneusta (Acorn Worms)

Acorn worms, live in marine muddy substrates, use a sticky proboscis to capture prey, and respire via gill slits.

Echinoderms (Echinodermata)

All marine, larvae have bilateral symmetry, adults have pentaradial symmetry, internal skeleton of calcified plates, and a water vascular system.

Water Vascular System of Echinoderms

A network of water-filled canals leading to tube feet, used for gas exchange, locomotion, and feeding; includes madreporite, ring canal, radial canals, and tube feet.

Classes of Echinoderms

Crinoidea (sea lilies/feather stars), Asteroidea (starfish), Ophiuroidea (brittle stars), Echinoidea (sea urchins and sand dollars), and Holothuroidea (sea cucumbers).

Crinoidea (Sea Lilies/Feather Stars)

Sessile or vagile, often stalked, mouth in the upper surface, and suspension feeders.

Asteroidea (Starfish)

Typically 5 arms, mouth facing downward, generally carnivores/scavengers, and often keystone species.

Keystone Species

A species with a large ecological effect relative to its abundance.

Robert Paine's Experiment

Predatory starfish (Pisaster ochraceus) removal leading to decreased community diversity, demonstrating top-down control.

Ophiuroidea (Brittle Stars)

Brittle stars and basket stars, typically 5 arms, mouth facing downward, internal organs in the disk, no anus, scavengers/detritivores, and some are bioluminescent.

Echinoidea (Sea Urchins and Sand Dollars)

Sea urchins and sand dollars, mouth facing downward, anus upward, test composed of fused plates of calcium carbonate.

Echinoidea Mouth

Mouth typically has Aristotle’s lantern.

Sea Urchins in Research

Easy-to-study embryos, closer to humans than Drosophila, some pathways highly conserved between sea urchins and humans.

Sea Urchins in Ecotoxicological Assays

Used in ecotoxicological assays to determine the concentration at which a substance disrupts normal development.

Holothuroidea (Sea Cucumbers)

Sea cucumbers, detritivorous or suspension feeders, mouth and anus in opposite poles.

Cuvierian Tubules

Sticky tubules expelled through the anus

Holothuroidea Toxicity

Many have toxic compounds (holothurin, a saponin) to reduce predation.