KINGDOM ANIMALIA
| TAXA OF LIFE | KINGDOM ANIMALIA |
| PHYLUM KINORHYNCHA |
INTRODUCTION TO THE KINORHYNCHA
Kinorhyncha (ki-no-RINK-a) is formed from two Greek roots that mean "moving by the snout" [moving -kino(κινώ); and snout -rhygchos (ρύγχος)]. The reference is to the way the animal moves by everting its mouth cone.
Kinorhynchs are small and covered with articulating dorsal and ventral segment-like plates, which usually have spines (Figure A). Characteristically, they have 13 segmenta and go through 6 moults before they mature. The body terminates in a characteristic array of two or more spines (Figure B). They seem to belong to a group of related pseudocoelomates: priapulids, loriciferans, and gastrotrichs. Kinorhynchs crawl through marine sediments and take in food by everting a mouth cone, called an introvert.
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A. photomicrograph of a kinorhynch. Note the segment-like articulating plates. |
B. Photomicrographs of Centroderes (L) and Echinoderes (R) with the characteristic posterior spines and plates. |
C. Standard illustration of a kinorhynch showing the anterior mouth cone (called an introvert) and body spines. |
| Images taken from: A: http://www.geomar.de/projekte/zealandia/images/12_bio_1_small.jpg B: http://animaldiversity.ummz.umich.edu/site/accounts/pictures/Kinorhyncha.html C: http://biodidac.bio.uottawa.ca/thumbnails/catquery.htm?Kingdom=Animalia&phylum=Kinorhyncha |
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SYNOPTIC DESCRIPTION OF THE KINORHYNCHA
| 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). |
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I. SYNONYMS: kinorhynchs, echinoderma, spiny-crowned worms, mud-dragons. II. NUMBER: > 100 species known. III. PHYLUM CHARACTERISTICS: A. Structure Symmetry: Bilateral Body Cavity: Mostly acoelomic with small pseudocoelomic spaces. Body Covering: Covered by chitinous cuticle that is divided into dorsal (tergites) and ventral (sternites) articulating plates. This is shed as the animal grows in the early stages of development. Support: Hydrostatic skeleton with external cuticle. Body divided into 11 segments. Digestive System: Complete food tube with mouth (muscular pharynx) and anus. Circulatory System: Absent. Locomotion: Anterior segments telescope. Anterior mouth cone (introvert) covered with spines which grip sediment and help to "pull" the animal as it extends and retracts its head segment. Excretory System: Protonephridial excretory canals. Nervous System: Multi-lobed "brain". Nerve cords run ventrally with ganglia in the body segments. Sensory bristles, photoreceptors (in some). Endocrine System: None. B. Reproduction: Reproductive System: Sexes separate. Oviparous. Development: Not known. C. Ecology: Benthic marine. |
HIERARCHICAL CLASSIFICATION OF THE KINORHYNCHA
| The taxonomy of the phylum comes from the system of Brusca and Brusca (2003) in which the phylum has one class (Kinorhynchida) and two orders. |
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CLASS KINORHYNCHIDA (2 ORDERS)
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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.
Hickman,
C. P. 1973. Biology of the Invertebrates. The C. V. Mosby Company.
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.
Storer,
T. I. and R. L. Usinger. 1965. General Zoology. 4th Edition. McGraw-Hill Book
Company.
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.
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By Jack R. Holt. Last revised: 01/31/2009 |
