DESCRIPTION OF THE PHYLUM KINORHYNCHA (REINHARD 1881)
| EUKARYA> UNIKONTA> OPISTHOKONTA> ANIMALIA> BILATERIA> PROTOSTOMATA> ECDYSOZOA> SCALIDOPHORA> KINORHYNCHA |
PHYLUM KINORHYNCHA LINKS
| 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. |
| INTRODUCTION TO THE KINORHYNCHA Kinorhynchs are small and covered with articulating dorsal and ventral segment-like plates, which usually have spines (Figure 1). Characteristically, they have 13 segments and go through 6 molts before they mature. The body terminates in an array of two or more spines (Figure 2). Kinorhynchs crawl through marine sediments and take in food by everting a mouth cone, called an introvert (Figure 3). Kinorhynchs belong to a clade of ecdysozoans called Scalidophora (Schmidt-Rhaesa 1998, Nielsen 2001, and Telford et al. 2008, see Figure 4), which includes the priapulids. It likely also includes the Loricifera, but little work has been done on them to warrant anything but a provisional connection. Morphological synapomorphies of the clade include an introvert with similar musculature and scalids, small spine like structures on the cuticle of the introvert (Schmidt-Rhaesa 1998, and Nielsen 2001). The basal position of the Scalidophora appears firm, both in molecular/phylogenetic studies (e.g. Edgecombe et al. 2011) and the fossil record (e.g. Harvey et al. 2010). Figure 4 illustrates the sister relationship between the Priapulida and Kinorhyncha and the questionable relationship with the Loricifera. Like the Loricifera, Kinorhyncha are very small (less than 1 mm). |
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| FIGURE 1. Photomicrograph of a kinorhynch. Note the segment-like articulating plates. Image from http://www.geomar.de/projekte/zealandia/images/12_bio_1_small.jpg | FIGURE 2. Photomicrographs of Centroderes (L) and Echinoderes (R) with the characteristic posterior spines and plates. Image from http://animaldiversity.ummz.umich.edu/site/accounts/pictures/Kinorhyncha.html | FIGURE 3. Standard illustration of a kinorhynch showing the anterior mouth cone (called an introvert) and body spines. Image from http://biodidac.bio.uottawa.ca/ |
FIGURE 4. The Kinorhyncha and its position within the Ecdysozoa (all taxa in bold).
P = Protostomata
S = Scalidophora
N = Nematoida
PA = Panarthropoda
| 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. Edgecombe, G. D., G. Giribet, C. W. Dunn, A. Hejnol,R. M. Kristensen, R. C. Neves, G. W. Rouse, K. Worsaae, and M. V. Sorensen. 2011. Higher-level metazoan relationships: recent progress and remaining questions. Organisms Diversity and Evolution. DOI 10.1007/s13127-011-0044-4. Harvey, T. H. P., X. Dong, and P. C. J. Donoghue. 2010. Are palaeoscolecids ancestral ecdysozoans? Evolution and Development. 12(2): 177-200. 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. Nielsen, C. 2001. Animal Evolution: Interrelationships of the Living Phyla. 2nd Edition. Oxford University Press. Oxford. Reinhard, W. 1881. Über Echinoderes und Desmocolex der Umgegend von Odessa. Zool. Anz. 4(97): 558–592. Schmidt-Rhaesa, A. 1998. Phylogenetic relationships of the Nematomorpha – a discussion of current hypotheses. Zoologischer Anzeiger 236:203-216. Storer, T. I. and R. L. Usinger. 1965. General Zoology. 4th Edition. McGraw-Hill Book Company. New York. Telford, M. J. S. J. Bourlat, A. Economou, D. Papillion, and O. Rota-Stabelli. 2008. The evolution of Ecdysozoa. Phil. Trans. R. Soc. B. 363: 1529-1537. 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: 04/08/2013 |
