Читать книгу Life in the Open Ocean - Joseph J. Torres - Страница 64

The sedentary nature of many of the Cnidaria (think anemone, not jellyfish) made their position within the animal kingdom difficult to decipher for the early natural philosophers, who considered them something somewhere between an animal and a plant. Aristotle called them Acalephae or Cnidae (from the Greek: akalephe = nettle; cnidos = thread) (Hyman 1940) and placed them with a variety of other soft‐bodied animals in with the Zoophyta (from the Greek: zoon = animal, phyton = plant). Researchers in the eighteenth century recognized the animal nature of cnidarian polyps, leading the way for natural philosophers of the nineteenth century, Linnaeus, Lamarck, and Cuvier, to place the cnidarians among the animals in their own classification systems, among either the Radiata, recognizing the importance of radial symmetry, or Zoophyta.

Just as happens today, the natural philosophers of the nineteenth century had differences of opinion on the group relationships. Lamarck’s system included the medusoid Cnidaria and echinoderms (starfish) in his Radiata, with the polypoid cnidarians simply called the Polyps. In 1829, Sars showed that polyps and medusae were different life stages of the same animal, not separate groups. Not quite 20 years later, Leuckart and Frey (1847) separated the two largest radially symmetrical groups, the echinoderms and the cnidarians, into two groups: the coelenterates and the echinoderms. Leuckart coined the term Coelenterata from the Greek words for body cavity (koilos) and intestine (enteron), noting that the only body cavity in the cnidaria was the intestine (Hyman 1940). Leuckart included the sponges and ctenophores within his Coelenterata. It was up to Hatschek (1888) to separate Leuckart’s Coelenterata into the three phyla we recognize today: the Spongiaria (Porifera), the Cnidaria, and the Ctenophora. The term Coelenterata is still extensively used today, most commonly as a synonym for the Cnidaria but sometimes as a way of combining the ctenophores and cnidarians into a single taxon.