The distribution of guanidines, phosphagens and N-amidino phosphokinases in echinoids.

The class Echinoidea assumed prominence in the field ofcomparative biochemistry when it was shown by Needham, Needham, Baldwin & Yudkin (1932) that the jaw muscles of Strongylocentrotus lividus contained both phosphocreatine and phosphoarginine. Further work by Baldwin & Needham (1937) showed that extracts of the jaw muscles of two other echinoids, Paracentrotus lividu,s and Sphaerechinus granularis, were capable of phosphorylating both creatine and arginine. This result suggested that the muscles ofboth ofthese organisms contained phosphocreatine and phosphoarginine, although neither phosphagen was identified. Earlier Meyerhof (1930) had advanced the hypothesis that phosphoarginine was the characteristic phosphagen in the muscles of invertebrates and phosphocreatine was characteristic of the vertebrates. The occurrence of both phosphagens in the echinoids studied provided biochemical support (Needham et al. 1932) for the evolutionary theory of Bateson (1886), namely that the echinoderms were the immediate precursors ofthe primitive chordates. Later work has shown that the premises on which Meyerhof's hypothesis was based are not correct. It has been shown that phosphocreatine is not confined to the vertebrates and those animals intermediate between vertebrates and invertebrates, but that it is also present in sponges (Roche & Robin, 1954) and annelids (Hobson & Rees, 1955). Moreover, other phosphorylated guanidines, e.g. phosphotaurocyamine, phosphoglycocyamine and phospholombricine, also occur in invertebrate muscle (Thoai, Roche, Robin & Thiem, 1953 a; Thoai & Robin, 1954). The earlier work on echinoids was concerned mainly with the study of the distribution of free guanidines. Arnold & Luck (1933) showed that arginine was present in the jaw muscles of Strongylocentrotusfranciscanus, and Holtz & Thielmann ( 1924) found arginine in Arbacia pustulosa. The first positive identification of creatine in echinoids was made by Greenwald (1946), who isolated potassium creatinine picrate from the testes of Strongylocentrotus sp. Before this, creatine had been identi-