Figure 1. A single colony of Nanomia bijuga, showing 

 tentacles extended in the fishing position; swimming 

 bells (nectophores) are situated in a cluster beneath 

 the gas-filled pneumatophore. 



Since most organisms associated with the DSL must 

 be capable of daily vertical migrations over distances of 

 several hundred meters, any animal possessing an enclosed 

 gas phase must be able to cope with the problems created 

 by this expanding gas during upward swimming. N. bijuga 

 possesses a pore at the tip of the pneumatophore which is 

 said to be closed by a sphincter-like muscle. Thus it is 

 easily capable of voiding gas during a vertical ascent. 



Therefore, although the manner by which nanomians 

 cope with expanding gas during ascent seems apparent, it 

 is not yet known how quickly they may regain neutral buoy- 

 ancy during descent or while at deep daytime levels, or 

 how they handle the hydrostatic pressures of 30 to 40 

 atmospheres impinging upon the pneumatophore. These 



