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Phylum Loricifera Nanaloricus |
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The Loricifera is a new animal phylum first described in 1983. All species are small, less than 1 mm in length, and barely visible with the naked eye. They are small bottom dwelling animals (meiobenthos) in the deep sea. From Japan, a new species of the Nanaloricus was discovered from the sea floor of the Ogasawara trench more than 8000 meters deep. However, only about 30 species of the Loricifera has been discovered, and little is known about this phylum yet. In the future, the number of known species will increase if we search them all around the world. Adult loriciferans presumably attach very firmly to sand grains or live as parasites. On the other hand, the larvae are believed to be free-living, but the actual life history is barely known. The adults and larvae have a very similar body structure, but as Figure 13 shows that the larva has a pair of large feet called “hooves” on the posterior end of its body. The larvae are believed to move the hooves like fins to swim around. Because their exuviae have been found in the sand, the larvae most probably molt several times before they become adults. Only a few researchers in the world actually have seen the larvae or adults alive, and almost no records of loricifera cultures. They are not only small but also rare. Only a few loriciferans may be found from several tons of sand. In addition, if the body is completely contracted, it is very easy to confuse with other animals. As the name Loricifera suggests (from Latin, lorica = corselet, ferre = to bear), most of the body is consisted of the trunk. And the trunk is covered with many armor-like cuticle plates. Some species have more than 60 plates. The Loricifera protects the anterior part of the body by retracting it in the trunk wearing the armor-like plates. The frontal tip of the retracted body is called a mouth cone, and it looks like an extendable telescope. The Loricifera supposedly uses the mouth cone to suck nutrients from the host. The transverse section of the mouth cone has uniquely structured hexaradial symmetry. This anterior part is covered with various sizes and shapes of more than 200 spines which are evenly distributed on the entire surface, and it looks like a cactus. Sex of the Loricifera can be identified based on the shape of the spines. Due probably to fine movement of many spines, the number of cells per body is large despite having a small body. The larva has no spines on the mouth cone area yet. The female holds only one large mature egg in her body. After internal fertilization, the egg presumably develops, but the mating patterns and initial developments are not known yet. However, species who conducts external fertilization was discovered in recent years. Characteristics of the Loricifera, such as the structure of spines, armored cuticles and molting to grow, correspond to the characteristics of the Kinorhyncha. Therefore, these two phyla are believed to have a close relationship with each other. However, the Loricifera has characteristics similar to that of water bears (Tardigrada) and wheel animals (Rotifer), thus, the phylogenic relationships have not been well understood. |
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In preparation
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I am sorry.
A song is only Japanese.
Song
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karaoke
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