The only figure for intact siphonophore metabolism 

 to be found in the literature is given by Vernon 8 for 

 Forskalta oontorta, also a physonect form. His value, 

 from a single specimen, was equivalent to 0.012 jil/mg/hr, 

 at 16 °C. This is only about one-fifth of the average of the 

 figures reported here even without temperature compensation. 



Larimer and Ashby 9 measured oxygen consumption 

 of the minced float tissues (presumably not including gas 

 gland) of the Portuguese man-of-war, Physalia. Their 

 experiments, performed at 25 °C and with sodium succinate 

 added as a metabolic substrate, gave a range of 0. 075 to 

 0. 105 fil P er mg/hr. Although the experimental conditions 

 are markedly different, these values closely approximate 

 those presented in table 1. 



Comparison of Nanomia bifuptgar 

 With Other Siphonophores 



The siphonophore listed for Experiments 4 and 5 is 

 included because it provides an important basis for compar- 

 ison to the comparatively common ^ bijuga. This species, 

 tentatively identified as Rhi2ophysa sp. (figs. 2-4) is a 

 member of the pneumatophore-bearing Cystonectae, another 

 sub-order of the Siphonophora. These also bear gas -filled 

 floats* with apical pores but lack nectophores (swimming 

 bells) or bracts (leaf -like appendages which aid in flota- 

 tion). However, the specimens obtained were captured 

 intact, and the similarity of results for oxygen consumption 

 of this species and of N. bijuga indicate the validity of 

 results obtained by performing tests upon the automatized 

 pneumatophores of the latter. 



Volume of Pneumatophore Gases 



In terms of effects on acoustic energy at specific 

 wavelengths (frequency dependence), the volume of gas 



* Analysis of the gases within the float of one of these individuals after holding it for 30 

 hours at 4°C gave 27.3% carbon monoxide, virtually all of the remainder analyzing as inert 

 gas presumed to be largely nitrogen. 



15 



