Deuterostomia i

1. Deuterostomiai BIOL240.002 Zoology 3 November 2014

2. Deuterostome Phylogeny Fig. 14.1 p. 291

3. Phylum Chaetognatha“long hair jaw”—~100 (131) spp. arrow worms • Mostly planktonic marine predators, 1-12 cm • Some are bottom-dwelling predators • Teeth and 4-14 curved spines that grasp prey • Tripartite coelom • Tenuous phylogenetic status • Blastopore  anus…? • Enterocoely…? • Protostome-like ventral nerve cord • Early offshoot of bilaterians? • Simultaneous hermaphrodites • Transfer spermatophore to partner’s neck • May self-fertilize • Eggs planktonic with direct development Fig. 14.2 p. 292

4. Phylum Xenoturbellida“foreign bustle”—2 (2) spp. xenoturbellidans • Marine worms • Up to 4 cm • Predators of bivalves and their larvae • Longitudinal and mid-body furrows • Mouth; no anus • No body cavity • Very simple nervous system • No respiratory, circulatory, or excretory organs • No defined gonads • Direct development • Phylogenetic placement controversial • Sister to Acoelomorpha (basal in Bilateria)? • “Xenacoelomorpha” in CoL based on 2013 study • Deuterostome? • 2006 study of protein amino-acid sequences Fig. 14. p. 291

5. Phylum Echinodermata“prickly skin”—~7000 (6753) spp. echinoderms • Strictly marine • Five-part symmetry as adults • Water vascular system of podia (“tube feet”) • Madreporite, ring canal, lateral canals • Primitively: Passing food to mouth • Derived function: Locomotion • Ossicles form endoskeleton in skin • Pedicellariae of sea stars and sea urchins prevent fouling • Simple nerve ring • Poorly developed sense organs • Mostly dioecious with external broadcasting of gametes • Larvae are bilateral with three-part coelom Fig. 14.6 p. 296

6. Echinoderm Pentaradial Symmetry • Metamorphosis renders pentaradial symmetry • New mouth on left side • Posterior chambers become new coelom • Left anterior and middle chambers become water vascular system • Right ones disappear • Only animals in Bilateria not bilaterally symmetrical Fig. 14.9 p. 299 Brittle star Sea star Sea cucumber Crinoid Sea urchin Fig. 14.10 p. 299

7. Echinoderm Systematics and Taxonomy 1854 spp. 8 orders 1006 spp. 16 orders 105 spp. 4 orders 2074 spp. 2 orders 1714 spp. 5 orders Fig. 14.3 p. 293

8. Class Crinoidea—sea lillies and feather stars“lily form” • Sessile (sea lilies) or sedentary (feather stars) • Latter swim or crawl, but rarely • Five highly branched arms with upward-facing ambulacral grooves for feeding • No spines or pedicellariae Fig. 14.22 p. 304 Fig. 14.23 p. 305

9. Class Asteroidea—sea stars and sea daisies“star form” • Five (or more) arms • Numerous small ossicles and spines • Numerous pedicellariae • Mouth ventral, anus dorsal • Podia of each arm in pairs along ambulacral grooves • Primarily used for locomotion • May also assist in feeding, with eversible forward part of stomach • Autotomy and regeneration of arms • Bipinnaria larva becomes brachiolaria with ciliated arms Fig. 14.4 p. 294 Fig. 14.7 p. 297

10. Sea Daisies • 3 spp. of deepwater habitats off New Zealand and the Bahamas and in the Pacific • No arms; podia at margin of circular body • Two concentric ring canals in wvs • Originally classified in new class, Concentricycloidea, when discovered in 1986, but phylogenetically they appear to be nested within Asteroidea Fig. 14.11 p. 300

11. Class Ophiuroidea—brittle stars and basket“snake tail form” stars • Five elongate arms with spaces in between at the central disc • Highly branched in basket stars • Podia used in filter feeding, but not locomotion • Locomotion via whip-like motions of arms • Large articulating ossicles in arms • Five jaws surround ventral mouth • 10 bursae for gas exchange • Asexual fission Fig. 14.12 p. 300 Fig. 14.13 p. 301 Fig. 14.14 p. 301

12. Class Echinoidea—sea urchins, heart urchins,“hedgehog form” and sand dollars • Endoskelton forms an integrated test • Complex chewing Aristotle’s lantern surrounds mouth in sea urchins and sand dollars • Sand dollars also use wvs podia to collect food • Secondary bilateral symmetry in heart urchins and sand dollars • Pedicellariae present • Locomotion: • Sea urchin: spines and podia • Heart urchins: spines only • Sand dollars: spines only Fig. 14.17 p. 302 Fig. 14.18 p. 303

13. Class Holothuroidea—sea cucumbers“sea cucumber form” • Elongate echinoderms that lay on their sides • Very reduced ossicles in leathery skin • Tentacles surrounding the mouth are modified podia of the wvs • Locomotion via three well-developed rows of tube feet • Respiratory trees internally for gas exchange • Self-defense via discharge of toxic Cuverian tubules, digestive tract, and/or gonads Fig. 14.21 p. 304 Fig. 14.19 p. 303

14. Phylum Hemichordata“half cord”—~105 (106) spp. acorn worms • Marine worms/colonies • Up to 2.5 m, mostly <<1 m • Deposit feeders using mucus and cilia on proboscis to drive a current into the mouth and out gill slits • Food ensnared in mucus • Respiration mainly at ventilated gill slits • Collar opens to expose mouth • Tripartite coelom • Proboscis, collar, trunk • Ventral and dorsal nerve cords • Latter is hollow • Mostly dioecious with external fertilization • Tornaria larva is also tripartite Fig. 14.24 p. 306 Fig. 14.25 p. 306 Fig. 14.26 p. 307

15. PterobranchHemichordates • Colonies that form via asexual budding • Only a few mm in length • Proteinaceoustubarium secreted around the colony • Proboscis is a cephalic shield • Extension/contraction • Ciliated tentacles of collar are very much like a lophophore • U-shaped digestive tract • Lacks the dorsal nerve cord • Some dioecious, some monoecious Fig. 14.27 p. 308