16 THE PHYSIOLOGY OF EARTHWORMS 



through the agency of ATP. Excess phosphate bonds are stored in a 

 form bound to a substance known as phosphagen. In the vertebrates 

 this is exclusively creatine phosphate. Until quite recently (see 

 review by Ennor and Morrison, 1958) it was thought that the vast 

 majority of invertebrates relied on arginine phosphate as their 

 phosphagen. This phenomenon was thought to throw light on 

 evolutionary processes because such forms as echinoderms and 

 enteropneusts apparently possess both creatine and arginine 

 phosphate in their tissues (for table see Kerkut 1960, p. 112). 



Within the last few years, however, it has become increasingly 

 obvious that the invertebrates are not a homogeneous group and 

 that a number of phosphagens other than arginine phosphate are 

 to be found. Three different phosphagen substances have now been 

 described in annelids : taurocyamine in Arenicola, glycocyamine in 

 Nereis and lombricine in Lumbricus (Thoai and Robin, 1954). 



OH.Po; 



^O.CH2.CH(NH2) .GOGH 

 Fig. 6. Formula of lombricine. 



Arginine phosphate may be present but is not active as a phos- 

 phagen. 



Earthworm muscles hydrolysed in 6N HCl for 8 hours at 110 °C 

 break down into their constituent parts, and among these Thoai 

 and Robin (1954) found the amino-acid serine and a number of 

 related guanidino derivatives. These included guanidoethyl- 

 seryl-phospho-diester, which they named lombricine. 



This substance is found alone in the muscles of the earthworm, 

 but in conjunction with arginine in the gut wall. The associated 

 phosphagen phosphoguanidyl-ethyl-seryl-phosphate, is also 

 present in the tissues (Thoai and Robin, 1954, Fig. 6). Phosphagen 

 is at a concentration of 6-1 /ixmoles/g. ATP amounts to 2-8 /xmoles/g 

 and ADP 0-7 /xmoles/g (Rey, 1956). 



Further details regarding the isolation, structure, biological 

 synthesis and precursors of lombricine are to be found on p. 114. 



Sumffiary 



The oHgochaete body contains much water (about 80-85%) 



