§ 5.422 BALANCE OF PHOSPHATES 251 



5.422 Decrease of phosphates in the blood 



Crustacea. Since eyestalk removal appears to increase the 

 phosphate content of the blood of Decapoda, it may perhaps be 

 assumed that a hormone of the ganglionic-X-organ/sinus 

 GLAND complex is normally responsible for decrease or restraint 

 in the level of blood phosphates, as it is for protein catabolism 

 (§ 5.221); but there is little quantitative data on this. The action 

 might be indirect through inhibition of Y-organ secretion (§5.411). 



Insecta. The most marked decrease of total phosphates in the 

 blood of Carausius occurs at the time of the 5th and 6th nymphal 

 mouhs and of the final moult to the aduh (L'Helias, 1954). This 

 may be compared with the decrease in blood-sugars which occurs 

 at the same times, when the moult-promoting hormone, 

 ecdysone, is being actively secreted by the prothoracic gland 

 (§ 5.212). There is no direct evidence of hormonal control of total 

 phosphates in the blood ; but the source of ecdysone was left intact 

 in both the controls and the allatectomized specimens used in these 

 experiments (§ 51.42), and both showed phosphate decreases 

 whenever they moulted.* 



Teleostel The ultimobranchial body of Astyanax is thought 

 to be the homologue of the tetrapod parathyroid gland. It is 

 stimulated by the increase of phosphates in the blood and it has 

 therefore been assumed that its normal action is also the same as 

 that of the parathyroids, namely to decrease the level of phosphates 

 in the blood by increasing their excretion (Rasquin and Rosen- 

 bloom, 1954). 



Mammalia. A decrease in phosphates in the blood, shown 

 chiefly by the inorganic fraction, results from injecting para- 

 thyroid extracts ; but it seems that this may be due to at least two 

 causes : increased transfer of P from the blood to the tissues, and 

 increase in the so-called phosphate diuresis. Since this increased 

 phosphate excretion is not just proportional to the level of phos- 

 phates in the blood, but increases more rapidly than the increment 

 of P in the glomerular filtrate, it is postulated that parathormone, 



* Moults are reported as normal. No mention is made of any prema- 

 ture metamorphosis in those specimens from which the corpora allata 

 had been removed (cf. Part II, § 3). 



