Observations and Experiments on the Food Habits of 
California Sea Hares of the Genus Aplysia 
Lindsay R. Winkler 1 and E. Yale Dawson 2 
In A PREVIOUS paper the senior author (Wink- 
ler, 1959*2) presented the results of fecal pellet 
analyses to determine the influence of diet on 
the color of Aplysia calif ornica Cooper. Only 
the dominant plants were mentioned in con- 
nection with that immediate problem. The pres- 
ent paper contains more detailed information 
from that study and from subsequent observa- 
tions and reviews of references to Aplysia food 
plants. 
The food of A. calif ornica has received only 
limited consideration in connection with other 
studies. This is also true, however, of Aplysia 
species in general. Even in the large monograph 
of Mazzarelli ( 1893) the only indication of the 
nature of the food is in a discussion of the 
method of feeding, where we find the phrase 
. . algae (ordinarily Ulva lactuca ) which 
serves as nutriment.” In the extensive study of 
European Aplysia punctata by Eales (1921), 
about half a page is concerned with food. She 
notes an apparent change in food habits with 
age. The young, she says, live on red seaweed 
like Deles seria [probably D. sanguined] and 
then slowly migrate through the Laminaria 
zone, where they feed on Laminaria, into shal- 
low water, where the fully grown adults live on 
Fucus and Ulva. However, since she also states 
that they are found in the greatest numbers in 
the Zoster a beds, it may be that like Aplysia 
calif ornica they also feed on Zoster a. 
As to the feeding habits of A. calif ornica, 
MacGinitie (1935) stated that the animal eats 
Zostera in Elkhorn Slough. In a later work 
(MacGinitie, 1949) he stated that they eat "sea- 
weeds.” Winkler (1959^) referred to three red 
1 Department of Pharmacology, School of Medicine, 
Loma Linda University, Loma Linda, California. Pres- 
ent address: College of the Desert Palm, Desert, 
California. 
Manuscript received November 6, 1961. 
2 Beaudette Foundation for Biological Research, 
Santa Ynez, California. Present address: Hancock 
Foundation, University of Southern California. 
seaweeds used as food by Aplysia calif ornica and 
to their effect on the color pattern. Another 
paper (Winkler, 1959&) mentions the effect of 
diet, both qualitatively and quantitatively, on 
the purple secretion. Winkler (1961) mentions 
diet in connection with two special habitats 
which are reported here in more detail. Marcus 
(I 96 I) stated that A. calif ornica eats seaweeds, 
"especially Zostera and C odium.” 
MATERIALS AND METHODS 
Young specimens of Aplysia calif ornica 4-5 
inches long were captured on the central shore 
area of Lunada Bay, Palos Verdes, California, 
and each was placed in an individual pint fruit 
jar until fecal pellets were passed. The pellets 
were then removed to small screw-capped vials 
and the animal was released at sufficient dis- 
tance to preclude resampling. Twenty-five speci- 
mens from this area were sampled in this man- 
ner. Pellets were also collected from larger 
specimens wandering in the deeper waters of 
the bay and from 1 mile north of the north 
side of Palos Verdes Point. The pellets were 
kept under refrigeration until examined and 
identified by the junior author. Since the effi- 
ciency of sea hare digestion appears to be in 
indirect proportion to the rate and quantity of 
food ingestion, identification of the algae of- 
fered no great problem since these sea hares 
were well fed. 
Observations on specimens taken from Do- 
heny Beach, California, and from a small lagoon 
at Lunada Bay, possessing a different flora than 
the former, are also reported. The food plants 
determined from crop contents were made dur- 
ing other studies involving the sacrifice of the 
animals. 
RESULTS 
Results from 25 young specimens taken from 
Lunada Bay in 1955 are presented in Table 1. 
In this area the following seaweeds were noted 
102 
