EFFECTOR MECHANISMS 



375 



are dangerous to man, notably Physalia and Dactylometra. Aqueous, 

 alcoholic and glycerine extracts of tentacles produce different symptoms in 

 experimental animals, effects which it is unnecessary to list in detail. 

 Tetramine (tetramethylammonium hydroxide) has been extracted from 

 anemones in high concentration, and probably occurs in the nematocysts. 

 It is a quaternary ammonium base with powerful paralysing action on 

 motor-nerve endings. Some of the toxic properties of coelenterate extracts 



(b) 



(c) (d) 



Fig. 9.4. Responses to Stimulation of Cnidae on the 

 Tentacles of Anemonia sulcata 



(a) Response of cnidae to touch by human hair; (b) lack of response to clean glass 

 bead; (c) sensitization of cnidoblasts to a glass bead by immersion for 5 min in sea 

 water + saliva (0-1 % dry weight); (d) response to a glass bead smeared with alcoholic 

 extract of Pecten mantle. Scale, 100 //. (After Pantin (92).) 



recorded for higher vertebrates, including man, may be due to anaphylactic 

 shock from included proteins (12, 33, 85#, 96a, 117). 



Certain animals which prey upon coelenterates and preserve their 

 nematocysts make intriguing curiosities. Nematocysts are found em- 

 bedded in the tentacle of the ctenophore Euchlora and probably are derived 

 from small medusae on which it feeds. Certain aeolid nudibranchs, which 

 prey upon coelenterates, conserve the nematocysts occurring in their 

 food; these are passed into special sacs in the dorsal cerata, where they 

 form a protective mechanism against predators (Fig. 9.5). Selection is 

 exercised; in Aeolis, for example, which attacks the hydroid Pennaria, 

 only one kind of particularly effective nematocyst is retained (the micro- 

 basic mastigophores), the others undergoing digestion (19, 64, 69). 



Tentacles of ctenophores possess adhesive (lasso) cells, also known as 

 colloblasts, in lieu of nematocysts. The colloblast has a hemispherical 



