Inorganic Ions 



89 



CaClo the calcium concentration in the anemones doubles in 48 hours. Table 

 12 shows in the holothurian, Caudhia chilensis, the effects of disproportionate 

 increases in K + , Ca++, and Na+ and decrease in S04= in the medium. 

 Within 5 days the body fluid alters in salt balance to conform to the altered 

 environment; two-way permeability is indicated. Sea urchins take up Nal by 

 exchange with NaCl through the body surface. " Echinoderms, which 

 nearly correspond ionically to the sea, lack a closed circulatory system and thus 

 conform to Macallum's hypothesis; however, other animals which have an 

 open circulatory system show disproportionate changes in ionic concentrations 

 in a changed medium. The worm, Phascolosoma, shows no osmoregulation 

 but does show good salt regulation; the content of Cl~ in the muscles increases 

 more than does that of K+, when these elements are increased proportionately 



U 



D 



1^1 



I 



i 



1.8 

 1.6 

 1.4 

 1.2 

 1.0 

 0.8 

 0.6 



U 0.4 

 < 



^ 0.2 



SEA WATER [%NaCl] 



Fig. 26. Relation between total osmotic pressure and chloride in blood of Aedes 

 detritus larvae and those of the medium expressed in equivalent concentrations of NaCl. 

 Broken lines for A. aegypti from Wigglesworth."" Diagonal straight line represents blood 

 and medium as isotonic. From Beadle.' 



in the medium. ^^"^ In such animals as the crustacean Carcinus maenas and 

 the mollusc Aplysia the ratio of ions can be changed in a few hours by 

 immersion in sea water containing an excess or a deficiency of particular 

 elements. ^^ For example, in sea water lacking calcium the blood Ca++ of 

 Carcinus dropped from 0.6 to 0.3 mg./cc. in 75 hours, whereas the blood 

 Ca++ of Aplysia decreased from 0.5 to 0.15 mg./cc. in 5 hours. When Car- 

 cinus is transferred to dilute sea water there is a net increase in salt excretion 

 and the percentages of Na + , K+, Ca+ + , and CI" increase relative to the 

 medium, while the percentages of Mg++ and S04= decrease.^-** 



It is doubtful whether the kind of circulatory system has much relation to 

 salt balance, since some animals with an open circulation show considerable 

 ionic regulation. No studies of ionic regulation in different media have been 



