By Mary N. Arai (auth.)

Scyphozoa have attracted the eye of many varieties of individuals. Naturalists watch their sleek locomotion. Fishermen may perhaps dread the swarms that may hinder fishing or devour larval fish. Bathers retreat from the water in the event that they are stung. humans from a few Asiatic international locations devour the medusae. Comparative physiologists research them as almost certainly easy types for the functioning of assorted structures. This ebook integrates info from these and different investigations right into a practical biology of scyphozoa. it's going to emphasize the wide variety of adaptive responses attainable in those morphologically really easy animals. The booklet will be aware of the study of the final 35 years, in part simply because there was a speedy enlargement of data in the course of that interval, and in part simply because a lot of the former paintings was once summarized by means of books released among 1961 and 1970. Bibliographies of papers on scyphozoa have been integrated in Mayer (1910) and Kramp (1961). Taxonomic diagnoses also are incorporated in these monographs, in addition to in a monograph at the scyphomedusae of the USSR released by way of Naumov (Naumov, 1961). so much impor­ tantly, a genenttion of scyphozoan staff has used as its 'bible' the monograph via F.S.Russell (1970) The Medusae of the British Isles. regardless of its restrictive identify, his publication reports many of the details at the biology of scyphozoa as much as that date.

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The only measurements of physical properties for the muscle of Cnidaria were made on the column muscle of Pachycerianthus torreyi, a ceriantharian anthozoan (Arai, 1965). A fixed reference length could not be defined due to extension of the mesoglea. Nevertheless, when the preparation of muscle and mesoglea was allowed to extend under a constant weight, the height of the twitch was shown to increase to a maximum and then decline, corresponding to the length-tension relationship of higher animals.

Information from each marginal sense organ is transferred to an associated marginal centre of the nervous system, and thence to the nerve nets. There may 'also be ocelli associated with the marginal sense organs which are sensitive to light. Functionally these responses of the marginal sense organs to light and gravity are best known. In addition the animals are also sensitive to other stimuli such as touch and various chemicals. Receptors for these modalities may be present in marginal patches of sensory epithelium, especially in pits, or may be outside the marginal sense organs such as on the tentacles.

5-15 nm intervals and vary in diameter from 20 to 90 nm. These filaments may be scattered among the thick and thin ones or concentrated in another area of the myofibril. Perkins et al. (1971) examined Chrysaora quinquecirrha fishing tentacle muscle contracted, or relaxed to 7-20 times or to 30 times the Muscle 25 contracted length. 5 nm). e. not in fully contracted or fully relaxed muscle. Both of these observations are very interesting and should be verified. The possibility that thick filaments contract as well as slide past thin filaments in muscles of higher phyla is very controversial (Pollack, 1990).

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