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SYNOPTIC DESCRIPTION OF THE PHYLUM SYNDERMATA

SYNOPTIC DESCRIPTION OF THE PHYLUM SYNDERMATA (AHLRICHS 1997)

EUKARYA> UNIKONTA> OPISTHOKONTA> ANIMALIA> BILATERIA> PROTOSTOMATA> SPIRALIA> PLATYZOA> GNATHIFERA> SYNDERMATA
SYNDERMATA LINKS

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: Rotifera, rotifers, rotatoria, spiny-headed worms, thorny-headed worms, Acanthocephala, Gnathifera.

II. NUMBER: > 2,800 species known.

III. PHYLUM CHARACTERISTICS:

  • A. Structure
    • Symmetry: Bilateral
    • Body Cavity: Small pseudocoelom. 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 (text with tooltip) An evertible proboscis is a proboscis that can be extended usually by hydrostatic muscular contraction. in a cavity that resembles 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. The pseudocoelom is well developed in the Acanthocephala.
    • Body Covering: Extracellular cuticle (text with tooltip) Cuticle is an acellular covering that is secreted by the epithelium. (chitinous) and an intracellular skeleton, which forms the lorica of some forms. Inner layer derived from syncytial epidermis.
    • Support: Hydrostatic skeleton.
    • Digestive System: Complete food tube with mouth and anus. Captures food with anterior ciliary organs (coronae); breaks down the food particles with an elaborate “jaw-like chewing mechanism” (trophi) in the mastax (text with tooltip) Mastax is the pharynx of a rotifer, which contains the trophi. or pharynx. Corona reduced in Seisonida and absent in Acanthocephala. Likewise, the trophi and digestive tract are absent in Acanthocephala.
    • Circulatory System: Absent.
    • Locomotion: Swims with anterior ciliary organs and muscular contractions using adhesive attachments of foot. Anterior segments telescope as an evertible proboscis.
    • Excretory System: One pair of protonephridia (text with tooltip) Protonephridia (protonephridium, sing.) are excretory organs that are ciliated tubules. The flame cell lies at the internal terminus ciliated tubule. .
    • Nervous System: Anterior ganglion with 2 major nerves; with sensory eyespots, bristles, etc. Highly reduced in the Acanthocephala.
    • Endocrine System: None.
  • B. Reproduction:
    • Reproductive System: Most are dioecious (text with tooltip) Dioecious organisms have separate male and female individuals. with internal fertilization. Can reproduce by parthenogenesis. 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 spiral cleavage (text with tooltip) Spiral cleavage is typical of the Protostomata and is characterized by the division planes of early cytokinesis products of the zygote being oblique to the plane of the polar axis. This produces unequal cells in the developing blastula. Usually spiral cleavage is determinant. . No larval stage except in Acanthocephala: acanthor, acanthella, and cystacanth.
    • Life Cycle of Macrocanthorhynchus hirudinaceous
  • C. Ecology: Free-living taxa: Freshwater, or (less so) marine. Usually filter feeders, sometimes carnivores. Planktonic or benthic.
    • Parasitic taxa: Seisonida are ectoparasites of certain crustaceans. Acanthocephalans are parasites of vertebrate intestines as adults, larval stages usually in arthropods.
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.

Garcia-Varela, M. and S. A. Nadler. 2006. Phylogenetic relationships among Syndermata inferred from nuclear and mitochondrial gene sequences. Molecular Phylogenetics and Evolution. 40: 61-72.

Garey, J. R., A. Schmidt-Rhaesa, T. J. Near, and S. A. Nadler. 1998. The evolutionary relationships of rotifers and acanthocephalans. Hydrobiologia 387:83-91.

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

Kristensen, R. M. 2002. An introduction to Loricifera, Cycliophora, and Micrognathozoa. Integrative and Comparative Biology. 42: 641-651.

Kristensen, R. M. and P. Funch. 2000. Micrognathozoa: A new class with complicated jaws like those of Rotifera and Gnathostomulida. Journal of Morphology. 246: 1-49.

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.

Rieger, R. M. and S. Tyler. 1995. Sister-group relationship of Gnathostomulida and Rotifera-Acanthocephala. Invertebrate Biology. 114: 186-188.

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.

Sorenson, M. V., H. Segers, and P. Funch. 2005. On a new Seison Grube, 1861 from coastal waters of Kenya, with a reappraisal of the classification of the Seisonida (Rotifera). Zoological Studies. 44(1): 34-43.

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.

Zrzavy, J. 2001. The interrelationships of metazoan parasites: a review of phylum- and higher-level hypotheses from recent morphological and molecular phylogenetic analyses. Folia Parasitologica. 48:81-103.
By Jack R. Holt and Carlos A. Iudica. Last revised: 01/29/2012
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