DESCRIPTION OF THE PHYLUM LORICIFERA (KRISTENSEN 1983)
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PHYLUM LORICIFERA LINKS
| Loricifera (lo-ri-KI-fe-ra) is formed from two Latin roots that mean corset (loricus) (text with tooltip) A lorica is a covering that occurs outside of the cell membrane. It is secreted by the cell and usually is organic. Loricas do not completely enclose the cell. Periplasts, structures similar to loricas do enclose the cell.<br>Lorica stands for armour. and bearers (fero). The reference is to the external covering (lorica). |
| INTRODUCTION TO THE LORICIFERA First described by Kristensen (1983), the loriciferans are inhabitants of marine sediments. They resemble rotifers with a body covered by large plates (a plated lorica, thus the name) and an anterior cone (introvert) surrounded by articulating spines (Figure 1). The discovery of new species and the subsequent studies of life histories led to some surprising results. Kristensen (2002) and Gad (2005) describe life histories that have significant levels of asexual reproduction and the formation of mature gonads in larvae (neoteny). Gad (2005) also reports the development of a new species of Pliciloricus in which the last instar becomes reduced to a much less complex adult. Loricifera provisionally belongs to a clade of ecdysozoans called Scalidophora (Schmidt-Rhaesa 1998, Nielsen 2001, and Telford et al. 2008, see Figure 2), which includes the kinorhynchs and priapulids. To date, 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). In a superficial sense, loriciferans, which are loricate, resemble the loricate larvae of the priapulids. |
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| FIGURE 1. (left) Diagram of a loriciferan that illustrates the anterior feeding cone with articulating spines. (right) A photomicrograh of a living loriciferan at approximately the same scale and aspect. Image from http://biodidac.bio.uottawa.ca/ | |
FIGURE 2. The Loricifera and its position within the Ecdysozoa (all taxa in bold).
P = Protostomata
S = Scalidophora
N = Nematoida
PA = Panarthropoda
| LITERATURE CITED Brusca, R. C. and G. J. Brusca. 2003. Invertebrates. Sinauer Associates, Inc. Sunderland, Mass. Gad, G. 2005. Successive reduction of the last instar larva of Loricifera, as evidenced by two new species of Pliciloricus from the Great Meteor Seamount (Atlantic Ocean). Zoologischer Anzeiger. 243: 239-271. Hickman, C. P. 1973. Biology of the Invertebrates. The C. V. Mosby Company. Saint Louis. Kristensen, R. M. 1983. Loricifera, a new phylum with aschelminthes characters from the meiobethos. Z. Zool. Syst. Evolutionsforsch. 21: 163-180. Kristensen, R. M. 2002. An introduction to Loricifera, Cycliophora, and Micrognathozoa. Integ. and Comp. Biol. 42: 641-651. 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. Nicholas, W.L. 2001b. The pseudocoelomate Ecdysozoa. In: Anderson, D.T., ed. Invertebrate Zoology. Oxford University Press. Oxford, UK. pp. 98-119. Nielsen, C. 2001. Animal Evolution: Interrelationships of the Living Phyla. 2nd Edition. Oxford University Press. Oxford. Pechenik, J. A. 2005. Biology of the Invertebrates. McGraw-Hill. New York. Ruppert, E. E. and R. D. Barnes. 1994. Invertebrate Zoology. 6th edition. Saunders. Ft Worth, TX. Schmidt-Rhaesa, A. 1998. Phylogenetic relationships of the Nematomorpha – a discussion of current hypotheses. Zoologischer Anzeiger 236:203-216. 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: 04/10/2013 |
