Physalia Nematocysts and 

 their Toxin 



Charles E. Lane 



Institute of Marine Sciences, University of Miami, Miami, Florida 



Nematocysts in Physalia are widely distributed through the 

 epithehum clothing most of the members of the colony. These 

 organelles are formed in cnidoblasts by so far imdescribed cyto- 

 genetic processes. The upper surface of the float and the proximal 

 portions of the gastrozooids and of the fishing tentacles are relatively 

 deficient in mature nematocysts. Over the surface of the fishing 

 tentacle cnidoblasts are concentrated in the epithelium clothing 

 the batteries. These are permanent structures distributed in bead- 

 like fashion along the length of one edge of the tentacle, and they 

 are illustrated in Figure 1, which shows a three-dimensional re- 

 construction of a segment of the fishing tentacle of Physalia. The 

 batteries appear as discrete saccular enlargements along one edge. 

 A longitudinal section through a portion of the tentacle, including 

 a single battery cut equatorially appears in Figure 2. 



The battery is lined by gastrodermis continuous with that 

 lining the gastrovascular extension in the tentacle. The mesoglea 

 is a thick band of fibrous connective tissue external to the gastro- 

 dermis. The epidermal layer bearing cnidoblasts clothes the entire 

 structure. At the equator of the battery the epidermis thickens 

 abruptly where the external hemisphere acquires its population of 

 mature cnidoblasts. Perhaps the most outstanding histological char- 

 acteristic of this epithelium is the regular distribution through 

 it of nematocysts belonging to two different size groups. The total 

 thickness of the epithelium is just sufficient to clothe the large 

 nematocysts, which range from 25 to 30 microns in diameter. 



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