STUDIES ON ABSORPTION AND METABOLISM OF P³² IN AQUATIC ORGANISMS-I

TURNOVER OF P³² IN RHIZO DRILUS LIMASUS (HATAI)

Abstract

A number of studies were reported on the uptake of dissolved P³² by aquatic organisms¹⁾. The present authors demonstrated that the fresh water fish was able to uptake P³²O₄ ion directly from aquarium water and that the gills were the major pathway for its absorption²⁾. No works have been made, however, of the turnover of the directly uptaken phosphorus among various phosphorus compounds except for that in the developing sea urchin embryo^4'5) The present paper deals with the turnover of absorbed P³² in a sludge worm, Rhizodrilus limasus (HATAI).
The radioactivity of the worm increased rapidly and linearly with time of culture when this worm was placed in P³²-containing water (Fig. 1). The acid soluble fraction was pre-pared by blending a sharply frozen tissue with trichloracetic acid. The lipide-, nucleic acid-and phosphoprotein-form phosphorus were fractionated from the insoluble part by the SCHNEIDER method⁷⁾. The distribution patterns of P³² in these four fractions were studied when the worm was active in absorbing P³², on one hand, and in excreing it, on the other (Fig. 2-5). It was found that P³² which was absorbed by Rhizodrilus, entered at first into the acid soluble fraction and that the acid soluble p³² was largely incorporated in both nucleic acid and lipide whereas only slightly in protein (Fig. 6).