Intraspecific Variation in the Purple Secretion of the 
California Sea Hare, Aplysia calijornica Cooper 
Lindsay R. Winkler^ 
The sea hare is probably best known be- 
cause of the red to purple fluid secreted from 
the margin of its mantle. There is only a 
superficial resemblance between this secretion 
and that of the genus Murex, which is the 
source of the anciently famous dye, "Tyrian” 
or "Royal Purple.” Aplysia purple, however, 
found no practical use, probably because of 
one important deficiency— it turns a dirty 
brown upon exposure to air and sunlight. 
Our knowledge of the nature and composi- 
tion of aplysia purple has been increased peri- 
odically since DeNegri (1876) presented a 
series of beautifully colored spectra. The most 
significant of the early papers is that of 
MacMunn (1899), who attempted an analy- 
sis but concluded that there was no reason to 
believe that aplysia purple was composed of 
more than a single component. Durrien and 
Turchini (1925) published a minor observa- 
tion which, unfortunately, was recognized as 
the oldest literature on the subject by some 
later authors. Schreiber (1932) presented the 
results of an extensive study of aplysia purple. 
He divided the purple into two components, 
one of which he showed to be a substance 
similar to urobilin and the other its precursor 
substance, which is also pigmented but very 
unstable.. Fontaine and Raffy (1936) made 
suggestions as to the possible source of the 
^ Present address: School of Tropical and Preventive 
Medicine, Loma Linda, California. This work done at 
Allan Hancock Foundation, University of Southern 
California. Manuscript received April 11, 1958. 
pigment molecules from the food of the sea 
hare. Lederer and Huttrer (1942) used chro- 
matographic columns to separate the two 
components found in the pigment. Fox 
(1953) summarized the work of the three 
last-mentioned authors. Christomanos (1955) 
presented a summary of biochemical studies 
on the purple of a questionable species he 
specified as A. depilans. He also reported iso- 
lating a green band on his powdered sugar 
column from the purple of the Aplysia which 
he refers to as A. depilans. He was unable to 
obtain sufficient concentrations to produce 
a spectrum. 
The present writer noticed that there was a 
gross color difference between young animals 
and adults of the west coast sea hare, Aplysia 
californica Cooper, the younger producing a 
bluer, the older a more reddish secretion. 
Experiments to test the cause of this phe- 
nomenon led to more basic studies of the 
composition and instability of aplysia purple. 
MATERIALS AND METHODS 
To obtain aplysia purple uncontaminated 
by salt water, specimens of Aplysia californica 
Cooper at Lunada Bay, Palos Verdes, Cali- 
fornia, were caught and the mantle area was 
rinsed with distilled water. This usually 
caused sufficient irritation to stimulate flow 
of the secretion but not enough to cause the 
opaline gland to discharge its contaminating 
viscous protein material. The aplysia purple 
was caught in small vials, to each of which a 
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