230 INVERTEBRATE PHYSIOLOGY 



TABLE L IONIC REGULATION IN SOME 

 MARINE INVERTEBRATES 



Concentrations in plasma or coelomic 

 fluid as percentage of concentration in 

 body fluid dialyzed against sea water 

 Na K Ca Mg CI SO^ 



COELENTERATA 



Aurelia aurita 99 106 96 97 104 47 



ECHINODERMATA 



Marthasfcrias glacialis 100 111 101 98 101 100 



TUNICATA 



Salpa maxima 100 113 96 95 102 65 



Annelida 



Arcnicola marina 100 104 100 100 100 92 



Sipunculoidea 



Phascolosoma vulgare 104 110 104 69 99 91 



Arthropoda 



Maia squinado 100 125 122 81 102 66 



Dromia vulgaris 97 120 84 99 103 53 



Carciyius manias* 110 118 108 34 104 6.1 



Pachygrapsus marmoratus-f 94 95 92 24 87 46 



Nephrops norvegiais 113 77 124 17 99 69 



MOLLUSCA 



Pecten maximus 100 130 103 97 100 97 



Neptunea antiqua 101 114 102 101 101 98 



Sepia officinials 93 205 91 98 105 22 



* Webb (1940). 



t This grapsoid crab is the only animal in the table which is hypo-osmotic (ionic 

 concentration 86% that of sea water). 



in the cephalopods, regulation may extend to every ion. High concen- 

 trations of protein, chiefly hemocyanin, are characteristic of these groups, 

 and values between 105 and 150 gm./liter are found in Eledone, Sepia, 

 and Loligo, with rather lower values (29-80 gm./liter) in the crustaceans. 

 Regarding individual ions, calcium is usually higher than the equilib- 

 rium values, except in some of the animals lacking calcareous skeletons, 

 such as tunicates, jelly fishes, polychaetes, and Sepia. Magnesium remains 

 high in all the groups except the sipunculids and some of the crustaceans. 

 An interesting feature about the decapods is the correlation between the 

 magnesium level in the plasma and the ability to move quickly (Robert- 

 son, 1953). Active crabs such as the portunids Carcinus and Portunus, 

 and the grapsid Pachygrapsus, as well as the lobsters Nephrops and Ho- 

 marus which are capable of quick movements, all have low magnesium 

 values ranging from 14-48% of those in sea water. Pachygrapsus eras- 

 sipes and the lobster Panulirus interruptus from the California coast also 

 have low magnesium values (Schlatter, 1941). On the other hand, slow- 

 moving crabs such as Dromia and the spider crabs Hyas and Maia have 

 high magnesium values ranging from 84-101%. It may be rather fanciful 



