Food of Velella lata — -Bieri 
555 
FIG. 2. Per cent composition, by count, of Velella 
food as function of total length of Velella. Shaded 
area is crustacean food. 1, Euphausiid eggs, 2, barnacle 
cyprids, 3, calanoid copepods, 4, other crustacean food. 
There appears to be no marked food selectivity by the 
different sizes, although copepods increase in impor- 
tance in diet at sizes above 30 mm. 
zooids and main central gastrozooids of Velella 
but were not studied quantitatively: larval fish, 
including a saury; chaetognaths and their eggs; 
barnacle nauplii, probably of Lepas; siphono- 
phores; larvae of decapod Crustacea; adult my- 
sids; copepod eggs and nauplii; larval and adult 
euphausiids; corycaeid copepods; pteropods. 
Velella also were found to have eaten the dia- 
tom Coscinodiscus and the medusae of other 
Velella. One specimen had eaten a fish scale. 
Specimens cast upon the beach were found to 
have ingested sand into the gastrozooid as well 
as into the gonozooids. Thus it appears that 
Velella is a carnivore, feeding on anything it 
can catch, generally weakly swimming or non- 
motile zooplankton. 
In Figure 3 the mean number of fish eggs 
Fig. 3- Amour t of food caught as function of 
length of Velella. Although number of fish eggs in- 
creases rapidly with length, weight of food caught per 
gram of wet body weight decreases after length of 
about 40 mm. 
caught by various sizes of Velella is shown as 
curve A. The number increases rapidly with in- 
creasing length of Velella. 
The amount of food in each size group of 
Velella was too small to allow reliable weight 
determinations. Therefore, the wet weight of 
food present was estimated by calculating the 
volume of the fish eggs, assuming their density 
to be one, and assuming that the crustacean food 
on the average was one-third the weight of the 
fish eggs. On the basis of these assumptions, the 
weight of food caught per gram wet body 
weight of Velella is shown as a function of the 
length of Velella (Fig. 3, curve B) . At lengths 
greater than about 40 mm. the Velella increase 
in weight more rapidly than they increase the 
amount of food caught. 
TABLE 1 
Food of Velella Compared to Associated Zooplankton 
BY COUNT 
% OF Velella FOOD 
(38 specimens) 
% OF PLANKTON 
( 0-Vi m. net tow) 
Euphausiid eggs 
78 
10 
Euphausiid metanauplii 
0.5 
52 
Copepods 
3 
34 
Anchovy eggs 
3 
3 
Other fish eggs 
0.5 
<0.1 
Larvacea 
11 
<0.1 
Barnacle cyprids 
0.5 
<0.1 
Hyperiid amphipods 
0.5 
<0.1 
Cladocera ( Evadne ) 
1.0 
<0.1 
Emerita larvae 
1.5 
<0.1 
Parasitic copepods, Caligus 
0.5 
<0.1 
