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SYNOPTIC DESCRIPTION OF THE PHYLUM GASTROTRICHA

SYNOPTIC DESCRIPTION OF THE PHYLUM GASTROTRICHA (METSCHNIKOFF 1865)

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Introduction

Hierarchical Classification

The following information came from Margulis and Schwartz (1998), Buchsbaum (1938), Barnes (1980), Barnes (1984), Brusca and Brusca (2003), Hickman (1973), Storer and Usinger (1965), and Tudge (2000).

I. SYNONYMS: gastrotrichs.

II. NUMBER: >450 species known.

III. PHYLUM CHARACTERISTICS:

  • A. Structure
    • Symmetry: Bilateral
    • Body Cavity: Problematic, probably acoleomic. Organ systems in parenchymatous mesoderm (text with tooltip) Parenchymatous mesoderm is connective tissue that fills the space between the musculature and the gut in acoelomates. . Evertible proboscis in a cavity similar to a rhynchocoel (text with tooltip) A rhynchocoel is a fluid-filled body cavity (coelom? pseudocoelom?) into which the nemertene evertible proboscis retracts. , dorsal to the intestine.
    • Body Covering: Ciliated epithelium, particularly on ventral side. One flagellum (cilium) per epidermal cell as in Gnathostomulida. Surface covered with a cuticle (text with tooltip) Cuticle is an acellular covering that is secreted by the epithelium. that has characteristic scales or spines and adhesive tubes for temporary attachment.
    • Support: Hydrostatic skeleton.
    • Digestive System: Complete food tube with mouth (muscular pharynx) and anus.
    • Circulatory System: Blood vessel system in parenchymal mesoderm (text with tooltip) Parenchymatous mesoderm is connective tissue that fills the space between the musculature and the gut in acoelomates. .
    • Locomotion: Ciliated epithelium and muscular contractions.
    • Excretory System: Protonephridial (text with tooltip) Protonephridia (protonephridium, sing.) are excretory organs that are ciliated tubules. The flame cell lies at the internal terminus ciliated tubule. excretory canals.
    • Nervous System: Two anterior ganglia with 2 major lateral nerves. Anterior sense organs such as photoreceptors (text with tooltip) A photoreceptor is any structure that detects light. , bristles, and sensory pits.
    • Endocrine System: None.
  • B. Reproduction:
    • Reproductive System: Hermaphroditic (text with tooltip) An animal that bears both male and female gonads. , some parthenogenetic. Oviparous (text with tooltip) An oviparous (adj.) animal is one that releases eggs in its life cycle. They may be fertilized internally or externally. .
    • Development: Zygote develops by bilateral radial cleavage; no distinctive larval stage.
  • C. Ecology: Freshwater, marine, free living, usually benthic (text with tooltip) A benthic (adj.) organism is one that lives in or on the bottom of marine or freshwater environments. .
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.

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.

Giribet, G., C. W. Dunn, G. D. Edgecombe, and G. W. Rouse. 2007. A modern look at the Animal Tree of Life. Zootaxa. 1668: 61-79.

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.

Meglitsch, P. A. and F. R. Schramm. 1991. Invertebrate Zoology. Oxford University Press, New York, Oxford.

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

Ruppert, E. E. and R. D. Barnes. 1994. Invertebrate Zoology. 6th edition. Saunders. Ft Worth, TX.

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.

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: 01/29/2012
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