On the nature and action of coclcnterate toxins 291 



no proof, however, that Me^N (" tetramine "), although found in large amounts in 

 coelenterates, is the paralyzing agent in ncmatocysls. 



A further observation made in Bimini deserves to be reported. The sea anemone, 

 Aiptasia, was often found in the Bimini lagoon, occupying an empty conch shell. 

 Such shells frequently contained a single specimen of the red snapping shrimp, 

 Crangon armatus (Rathbun).* Hermit crabs living in close association with sea 

 anemones (especially Eupagurus prideauxi, which is nearly enclosed by the cloak 

 anemone, Adamsia palliata) are known to be highly resistant to nematocyst toxins 

 (Cantacuzene, 1925 b; Cantacuzene and Damboviceanu, 1934 ( ; Rj;v. 1940; 

 Manuta, 1943). To test for a possible acquired resistance of C. armatus to nemato- 

 cyst toxins, appropriate doses of anemone tentacle extract were injected into several 

 specimens. Three types of crustaceans were used as controls (U. mordax, Callianassa 

 sp. and an unidentified shore crab). Crangon armatus survived for about 12 hours 

 after injection with an amount of extract which, in less than one hour, killed the other 

 crustaceans not found in association with sea anemones. This provides another 

 example of the acquisition of a resistance to nematocyst toxins by a crustacean living 

 in association with a sea anemone. 



II. OBSERVATIONS MADE AT FRIDAY HARBOR (JULY 23, 1951, TO 



AUGUST 19, 1951) 

 (a) Autotomy experiments 



At Friday Harbor, experiments similar to those done at Bimini were performed. 

 As sources of toxins, the tentacles of the sea anemone, Metridium dianthus, and the 

 large brown jellyfish, Cyanea capillata, were used. Tentacles were cut off and their 

 volume determined. Hydrochloric acid was then added to pH 3-4. The tentacles 

 were homogenized in a Waring blender and the homogenate strained through fine 

 bolting silk. The pH of the liquid obtained was about pH 6. This extract was diluted 

 with various proportions of sea water before use. 



As a test animal the common shore crab of that region, Hemigrapsus nudus, was 

 used. To compensate in part for a considerable size range, the crabs were sorted into 

 two groups, those weighing about 2 to 4 gm and those weighing about 5 to 8 gm. 

 Extracts and drugs were injected into the smaller crabs in a volume of 005 ml, while 

 the volume used for the larger size was double this. Thus the amount of active 

 material administered was, on the average, adjusted to body weight, since each test 

 was done on a group of ten crabs. 



Table III 

 Effect of extract of tentacles q/' Metridium dianthus on autotomy in Hemigrapsus 



nudus 



Dilution 



Total of walking 

 legs autotomized 



Spontaneous 

 autotomies 



1:10 1:20 1:50 



80/80 78/80 72,80 



42t 28 6 



t A second extract at this dilution when tested on two lots of 10 crabs each gave .^S and 

 40 spontaneous autotomies. 



* Kindly identified by Mr. John C. Armstrong. 



