SYNOPTIC DESCRIPTION OF THE PHYLUM ORTHONECTIDA (GIARD 1877)
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ORTHONECTIDA LINKS
| The following information came from Margulis and Schwartz (1998), Barnes (1980), Barnes (1984), Brusca and Brusca (2003), Hickman (1973), Storer and Usinger (1965), Valentine (2004), and Tudge (2000). |
I. SYNONYMS: orthonectids, mesozoans.
II. NUMBER: >40 species known.
III. PHYLUM CHARACTERISTICS:
- A. Structure
- Symmetry: Bilateral
- Body Cavity: Not present.
- Body Covering: Ciliated epithelium.
- Support: None.
- Digestive System: None.
- Circulatory System: None.
- Locomotion: Ciliated epithelium.
- Excretory System: None.
- Nervous System: None.
- Endocrine System: None.
- B. Reproduction:
- Reproductive System: Dioecious (text with tooltip) Dioecious organisms have separate male and female individuals. animals release eggs or sperm. Dicemids produce flagellated, planktonic larvae (text with tooltip) A larval form that is free-floating in the plankton, usually in marine species. .
- Development: Free-living orthonectids vermiform, annular, with somatic cells enclosing sperms or eggs. Sperm are discharged and penetrate the eggs; ciliated larvae formed after fertilization. Larvae penetrate host, lose ciliated somatic cells, become syncytial forming a plasmodium (text with tooltip) A plasmodium is a multinucleate cell formed by nuclear divisions without cytokinesis. and multiply asexually (text with tooltip) As the name implies, asexual reproduction is the formation of offspring without the union of gametes. Usually, asexual reproduction involves the production of specialized cells or multicellular structures that can give rise to new individuals. throughout the host tissues.
- C. Ecology: Parasites of marine invertebrates: echinoderms, nemertenians, turbellarian flatworms, polychaetes, and clams.
| 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. Walker, J. C. and D. T. Anderson. 2001. The Platyhelminthes, Nemertea, Entoprocta, and Gnathostomulida. In: Anderson, D.T., ed. Invertebrate Zoology. Oxford University Press. Oxford, UK. pp. 59-85. [L] Valentine, J. W. 2004. The Origin of Phyla. University of Chicago Press. Chicago. 614 pp. |
| By Jack R. Holt. Last revised: 01/26/2012 |
