BIOL 1030 – TOPIC 15 LECTURE NOTESTopic 15: Deuterostomes: Echinodermata and Hemichordata (Ch. 33)I. Deuterostomia (clade)A. defined primary by molecular evidenceB. some defining developmental traits (see previous notes), but those can get fuzzyC. clade includes the following phyla that we will cover:1. Phylum Echinodermata (clade)2. Phylum Hemichordata (clade)3. Phylum Chordata (clade)II. Phylum Echinodermata - urchins, sea stars, sea cucumbersA. marine; ~7000 living species; in fossil record back to over 650 MYAB. name means “spiny skin”, reference to their endoskeleton 1. calcium rich plates below skin2. living tissue when formed; usually fused into hard shell in adults3. pores in endoskeleton for water vascular system (madreporite, tube feet)C. water-vascular system - hydraulic system for moving, feeding1. water enters though madreporite, opening typically opposite mouth2. water from madreporite moves though stone canal3. water then enters the ring canal that encircles the esophagus 4. radial canals extend from ring canal into the 5 body parts, establishing basic symmetry5. radial canals branch out into tube feet6. contraction of muscular sac (ampulla) at base of tube foot causes fluid to be forced into tube foot, extending it – used formovementD. pentaradially symmetrical - derived trait, larvae are bilaterally symmetricalE. coelom – relatively large; used for circulation and respirationF. asexual reproduction - many will regenerate if a broken part contains part of the central nerve ring, sometimes they will breakon purposeG. sexual reproduction - form free-swimming larvae that are bilaterally symmetricalH. six classes, all apparently monophyletic1 of 3BIOL 1030 – TOPIC 15 LECTURE NOTESI. Class Crinoidea - sea lilies and feather stars1. mouth and anus on same side2. 5-200+ arms, filter feeders3. primitive, sessile4. sea lilies – have calcareous stalk 15-30 cm long (20 m in some fossils) - “living fossils”- once much more common one of the dominant forms of life in the marine fossil record of the Paleozoic era (both in numbers and size)5. feather stars - no stalkJ. Class Asteroidea - sea stars or starfish1. 1 cm - 1 m across2. to 10,000 m deep3. groove runs along each arm bordered by rows of tube feet4. tube feet are like little suction cups and create an impressive force5. feed mainly on bivalves- attach to either side of shell with tube feet- wait until bivalve fatigues- extrudes stomach into opening and digest preyK. Class Ophiuroidea - brittle stars1. look like sea stars, but more flexible, move via serpentine motion of arms, groove closed below arms2. tube feet used to capture small prey and as sensory structuresL. Class Echinoidea - sea urchins and sand dollars1. no arms2. usually move via spines operated by tube feet3. vegetariansM. Class Holothuroidea - sea cucumbers1. elongate2. often with leathery skin3. mouth surrounded by 8-30 modified tube feet called tentacles4. other normal tube feet move animal2 of 3BIOL 1030 – TOPIC 15 LECTURE NOTES5. will extrude their foul-smelling stomachs when frightenedN. Class Concentricycloidea – sea daisies1. recently discovered2. no arms3. tube feet on edge of disc, instead of along radial linesIII. Phylum Hemichordata (acorn worms)A. ~90 living species; all marineB. centimeter to meter size range; burrowing; proboscis, collar, and trunkC. name means “half chordates”; transitional group to phylum ChordataD. ciliated larvae resemble sea star larvaeE. form a clade with Echinodermata (group called Ambulacraria)F. share with chordates:1. dorsal nerve cord as well as ventral nerve cord2. part of dorsal nerve cord hollow in some3. throat with pharyngeal gill slits3 of
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