Reference : Biol. Bull., 145 : 323-339. (October, 1973; THE RESPIRATORY ADAPTATIONS OF THE PODIA AND AMPULLAE OF ECHINOIDS (ECHINODERMATA) 1 DOUGLAS H. FENNER 2 Rccd College. Portland. Oregon 97202, and the Marine Biological Laboratory. ll'oods Hole, Massachusetts 02543 Early work on the structure of echinoid podia and ampullae consisted of verbal descriptions and line drawings (Bather, 1900; Chadwick, 1900; Ludwig, 1904; MacBride, 1909; Cuenot, 1948; Hyman, 1955), some of which were highly schematic. Nichols (1959a, 1959b, 1961) has made photomicrographs showing the wide variety of adaptations of the terminal suckers of several echinoids. Most recently, Kawaguti (1964, 1965), and Coleman (1969) have investigated the structure of the wall of the tube feet and ampullae of echinoids using electron mi-croscopy. Because the podia are the primary respiratory structure of echinoids (Farmanfarmaian, 1959, 1966, 1968; Steen, 1965), a systematic search for respira-tory adaptations in the structure of echinoid podia was undertaken ( Fenner, 1971). The podium-ampulla system of most echinoids differs from that of asteroids and holothuroids in two respects. First, the connection between the echinoid podium and ampulla consists of two pores through the body wall instead of one. Recently, Yoshida (1966), and Coleman (1969) showed a septum dividing the base of the tube foot of D lad etna, each half of the lumen being served by one of the pair of pores through the body wall. An exception to the rule of two pores per podium is the arrangement found in the accessory tube feet on the oral surface of the sand dollar E r hmocyamus, which have only one pore passing through the body wall (Nichols, 1959b). Secondly, the echinoid ampulla has been reported to be crossed by strands of tissue (Ludwig, 1904; Cuenot, 1948; Hyman, 1955), or septae (Kawaguti, 1965), unlike the asteroid or holothuroid ampulla. The non-locomotor podia on the aboral surface of several echinoids (Cldaris and Echinus: Nichols, 1961: clypeastroids : Hyman, 1955; and spatangoids : Hyman. 1955, and Chesher, 1969) are believed to serve a respiratory function. Nichols (1959b) presented the histology of the respiratory podia (petaloids) of the clypeastroid, Echinocyamus. Ciliary currents within the podia contribute to respiratory gas transport (Faramanfarmaian, 1966). The spatangoids (Chesher, 1969) have a counter-flow between the ciliary currents within the podia and the ciliary currents outside the podia ; such a counter-current should enhance exchange of gases across the surface of the respiratory podia. This study was undertaken to systematically search for respiratory adaptations in echinoid podia and ampullae, and to clarify our knowledge of the morphology of echinoid podia and ampullae. 1 Early portions of this work composed part of a thesis submitted to the faculty of Reed College in partial fulfillment of the requirements for the degree of Bachelor of Arts. This investigation was supported in part by NSF Grant NR 1902 to the Experimental Invertebrate Zoology Course at the Marine Biological Laboratory. 2 The author's present address is Psychology Department, University of Pennsylvania. Philadelphia, Pennsylvania, 19104. 323
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