Post-larval Food of the Pelagic Coelenterate, Velella lata 
Robert Bieri 1 
Huge, unexpected swarms of Velella that 
have drifted onto the coasts of France, England, 
the United States, and other countries have 
stimulated many of the studies on the "purple 
sail.” Although recent reports (Savilov, 1958; 
Bieri, 1959) have indicated some of the reasons 
for the apparently haphazard appearance and 
disappearance of these swarms, we have little 
or no idea of the effect of such sporadic inva- 
sions on the local fauna. The size of these popu- 
lations is indicated in several published reports, 
of which Woltereck’s (1904) is typical. This 
particular swarm when cast onto the beach at 
Villefranche formed a mound Vi m. wide, Vj 
m. high, and fully 1000 m. long. Such huge 
populations must have a considerable effect on 
the community of organisms in the sea beneath 
them. 
This paper records some quantitative data on 
the food of Velella. Some possible effects of pre- 
dation by Velella on associated zooplankton are 
suggested. 
MATERIAL AND METHODS 
In the present study, 137 specimens were 
used. Ninety-nine of these were obtained by 
dip-net between 0915 and 1000 at 32° 4l' N., 
121° 04' W. on May 10, 1950. These specimens 
were sorted into five size-groups and preserved 
in formalin. On March 29, 1954, 38 specimens 
were collected in a special surface net between 
1400 and 1500 at 32° 40' N., 118° 16' W, and 
were also preserved in formalin. 
In the laboratory all gonozooids were cut 
from the specimens and examined at 12 X mag- 
nification. Those parts containing visible food 
were removed and dissected, and the food items 
1 Antioch College, Yellow Springs, Ohio. The early 
stages of this study were carried out at the Scripps 
Institution of Oceanography, La Jolla, California, and 
the Lamont Geological Observatory, Palisades, New 
York. Manuscript received July 29, I960. 
were identified. The main central gastrozooids 
were dissected separately. Details of the weight 
determinations are given in Bieri and Krinsley 
(1958). 
RESULTS AND DISCUSSION 
Only three brief comments on the food of 
Velella appear in the literature. Huxley (1858) 
found copepod remains in the gonozooids, while 
Lebour (1947) reported a young "macerated” 
Velella with its "stomach” (main central gas- 
trozooid) full of harpacticoid copepods. Totten 
(1954) reported a calanoid copepod and crus- 
tacean remains in the gonozooids. No quantita- 
tive data are available. 
In the present study most of the food was 
found in the gonozooids. Only 33 per cent of 
the specimens examined had food in the main 
central gastrozooids. Digestion occurs in both 
the gonozooids and the gastrozooid, as is evi- 
denced by the exoskeletons of crustaceans found 
in both places. The food in the gastrozooid was 
somewhat larger on the average than that in 
the gonozooids. Possibly the gastrozooid ingests 
the organisms caught by the gonozooids that 
are too large for them to ingest. However, the 
gastrozooid also ingests small items. 
In the 99 specimens taken off California in 
May 1950, fish eggs (mostly those of jack mac- 
kerel, Trachurus symmetricus 2 ) made up 48 per 
cent of the total food by count. Euphausiid eggs 
made up 7 per cent of the food items. On the 
other hand, in 38 specimens taken off California 
in March 1954, euphausiid eggs made up 78 
per cent of the food items and fish eggs 3 per 
cent by count. 
The fish eggs had an average diameter of 1.1 
mm., the euphausiid eggs a mean diameter of 
0.41 mm. Thus a fish egg has nearly 17 times 
2 Dr. E. H. Ahlstrom, U. S. Fish and Wildlife Serv- 
ice, La Jolla, Calif., kindly identified the fish eggs. 
553 
