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SYNOPTIC DESCRIPTION OF THE PHYLUM HEMICHORDATA

SYNOPTIC DESCRIPTION OF THE PHYLUM HEMICHORDATA

EUKARYA>UNIKONTA>OPISTHOKONTA>ANIMALIA>BILATERIA>DEUTEROSTOMATA>HEMICHORDATA
PHYLUM HEMICHORDATA LINKS

Description of Phylum

Hierarchical Classification

The following information came from Margulis and Schwartz (1998), Buchsbaum (1938), Barnes (1980), Barnes (1984a), Brusca and Brusca (2003), Hickman (1973), Storer and Usinger (1965), Nielsen (2001), Colbert and Morales (1991), Pechenik 2005, and Tudge (2000).
  • I. SYNONYMS: acorn worms.
  • II. NUMBER: >100 species known.
  • III. PHYLUM CHARACTERISTICS:
    • A. Structure
      • Symmetry: Bilateral; body divided into proboscis (text with tooltip) A proboscis is a tube or tubular process that occurs on the head or the anterior of the gut. , collar and trunk.
      • Body Cavity: Eucoelomate; each body region with 1 or 2 enterocoelic cavities.
      • Body Covering: Covered by glandular epithelium.
      • Support: Stomochord (text with tooltip) A stomochord is a notochord-like structure in the preoral lobe of hemichordates. restricted to the pre-oral region; hydrostatic skeleton.
      • Digestive System: Mouth on ventral side of the collar. Tentacles on the head like a lophophore. Simple tube with a terminal anus (gut U-shaped with anus near collar in tube-dwelling taxa).
      • Circulatory System: Partially open with dorsal and ventral vessels; a heart;. and a series of sinuses; the blood is colorless.
      • Locomotion: Sluggish; moves under rocks, sediment and tubes.
      • Excretory System: Evaginations of the peritoneum into the proboscis coelom (text with tooltip) A coelom is a fluid-filled cavity that lies between the outer wall and the digestive tract that is bound by a specialized epithelial tissue called peritoneum. In this condition, all organs in the coelom are connected to the body wall by mesenteries. make a glomerulus (text with tooltip) A glomerulus is the ultrafiltration part of the kidney. .
      • Nervous System: Dorsal invagination of the collar into a hollow nerve tube (text with tooltip) A hollow nerve cord develops from the the invagination of the ectoderm. ; dorsal and ventral nerves.
      • Endocrine System:
      • Respiratory System Gill slits and direct absorption through the skin.
    • B. Reproduction:
      • Reproductive System: Sexes separate. Many pairs of gonads in the trunk coelom. Fertilization external.
      • Development: Eggs cleave radially. Usually ciliated larva or (rarely) direct development.
    • C. Ecology: Sluggish benthic marine animals; filter-feeders.
LITERATURE CITED

Barnes, R. D. 1980. Invertebrate Zoology. Saunders College/Holt, Rinehart and Wilson, Philadelphia.

Barnes. R. S. K. 1984a. Kingdom Animalia. IN: R. S. K. Barnes, ed. A Synoptic Classification of Living Organisms. Sinauer Associates, Inc., Sunderland, MA. pp. 129-257.

Bourlat, S. J., T. Juliusdottir, C. J. Lowe, R. Freeman, J. Aronowicz, M. Kirschner, E. S. Lander, M. Thorndyke, H. Nakano, A. B. Kohn, A. Heyland, L. L. Moroz, R. R. Copley, and M. J. Telford. 2006. Deuterostome phylogeny reveals chordates and the new phylum Xenoturbellida. Nature. 444: 85-88.

Brusca, R. C. and G. J. Brusca. 2003. Invertebrates. Sinauer Associates, Inc. Sunderland, Mass.

Buchsbaum, R. 1938. Animals Without Backbones, An Introduction to the Invertebrates. The University of Chicago Press. Chicago.

Cameron, C. B., J. R. Garey, and B. J. Swalla. 2000. Evolution of the Chordata body plan: New insights from phylogenetic analyses of deuterostome phyla. Proceedings of the National Academy of Sciences. U.S.A. 97: 4469-4474.

Colbert, E. H. and M. Morales. 1991. Evolution of the Vertebrates, A History of the Backboned Animals Through Time. WILEY-LISS, Inc. New York.

Delsuc, F., H. Brinkmann, and H. Philippe. 2005. Phylogenomics and the reconstruction of the tree of life. Nature Reviews: Genetics. 6:361-375.

Halanych, K.M. 1995. The phylogenetic position of the pterobranch hemichordates based on 18S rDNA sequence data. Molecular Phylogenetics and Evolution. 4(1): 72-76.

Hickman, C. P. 1973. Biology of the Invertebrates. The C. V. Mosby Company. Saint Louis.

Margulis, L. and K. Schwartz. 1998. Five kingdoms, an illustrated guide to the phyla of life on earth. 3rd Edition. W. H. Freeman and Company. New York. [C]

Nielsen, C. 2001. Animal Evolution: Interrelationships of the Living Phyla. 2nd Edition. Oxford University Press. Oxford.

Pechenik, J. A. 2005. Biology of the Invertebrates. McGraw-Hill. New York.

Putnam, N. H., T. Butts, D. E. K. Ferrier, R. F. Furlong, U. Hellsten, T. Kawashima, M. Robinson-Rechavi, E. Shoguchi, A. Terry, J.-K. Yu, E. Benito-Gutiérrez, I. Dubchak, J. Garcia-Fernàndez, J. J. Gibson-Brown, I. V. Grigoriev, A. C. Horton, P. J. de Jong, J. Jurka, V. V. Kapitonov, Y. Kohara, Y. Kuroki, E. Lindquist, S. Lucas, K. Osoegawa, L. A. Pennacchio, A. A. Salamov, Y. Satou, T. Sauka-Spengler, J. Schmutz, T. Shin-I, A. Toyoda, M. Bronner-Fraser, A. Fujiyama, L. Z. Holland, P. W. H. Holland, N. Satoh, and D. S. Rokhsar. 2008. The amphioxus genome and the evolution of the chordate karyotype. Nature. 453: 1064-1071.

Ruppert, E. E., R. S. Fox, and R. D. Barnes. 2004. Invertebrate Zoology: A Functional Evolutionary Approach. Seventh Edition. Thomson, Brooks/Cole. New York. pp. 1-963.

Storer, T. I. and R. L. Usinger. 1965. General Zoology. 4th Edition. McGraw-Hill Book Company. New York.

Swalla, B. J. and A. . Smith. 2008. Deciphering deuterostome phylogeny: molecular, morphological and palaeontological perspectives. Phil. Trans. R. Soc. B. 363:1557-1568.

Tudge, C. 2000. The Variety of Life, A Survey and a Celebration of all the Creatures That Have Ever Lived. Oxford University Press. New York.
By Jack R. Holt and Carlos A. Iudica. Last revised: 02/06/2013
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