KNUTSON & GOSLINER: NEW SPECIES OF GYMNODORIS NUDIBRANCHS 141 
FROM THE PHILIPPINES 
speculate that perhaps the unnatural 
conditions led to G pseiidobrunnea 
feeding on G brunnea\ however, it is 
not unusual for gyinnodorids to feed 
upon congeners and even con- 
specifics (Nakano 2011). Initially, it 
was thought that cannibalism in 
Gymnodoris was induced by unnatu¬ 
ral laboratory conditions (Young 
1967); however, gyinnodorids have 
exhibited cannibalism in their natural 
habitat (Johnson and Boucher 1983; 
Johnson 1992; Nakano 2011). This 
demonstrates that unnatural condi¬ 
tions don’t necessarily lead to abnor¬ 
mal feeding behavior. Further, in the 
field we were careful to keep 
Gymnodoris specimens separated 
from each other and other opistho- 
branchs to prevent loss of specimens. 
It is therefore likely that G pseudo- 
brunnea preys upon G brunnea under 
natural conditions, and that this most 
likely occurred prior to collection. 
Discussion. — Externally, this 
species looks very similar to G brnn- 
nea. Upon close examination, there 
are some subtle, but consistent differ¬ 
ences in appearance between the two 
species. The features that best differ¬ 
entiate these species externally 
include the shape and position of the 
white patch visible tlirough the skin 
on the dorsal side of the animals, and the external visibility of the intestine. The margin of the white 
patch is far more irregular in shape in G pseudobrunnea than it is in G brunnea. Also, in G pseudo- 
brunnea, the white patch appears at the gills and posteriorly, whereas in G brunnea, the white can 
be seen forward of the giU and posteriorly. In G. brunnea, the intestine is visible through the skin 
as a dark arch; this does not appear to be visible in G pseudobrunnea. 
Internally, there are distinct radular differences and differences in the arrangement of repro¬ 
ductive organs. The inner lateral teeth of G brunnea are much broader than those of G pseudo¬ 
brunnea. Also, the second inner lateral teeth of G brunnea are broad and bicuspid, whereas those 
of G pseudobrunnea are not differentiated from the rest of the middle and outer laterals. Further, 
in G pseudobrunnea, the lateral teeth are longer relative to the inner laterals, than those in G brun¬ 
nea. The main difference between the reproductive systems is the position of the receptaculum 
seminis. In G brunnea, the receptaculum seminis duct enters the vagina close to the bursa copula- 
trix, whereas in G. pseudobninnea the receptaculum seminis enters the vagina approxhuately 
halfway between the bursa copulatrix and the genital aperture. 
Figure 11. Scanning electron micrographs of the radula found inside 
of the digestive gland of a specimen of G. pseudobrunnea sp. nov. 
CASIZ 185967. A. View of the entire radula. B. Detail of the inner lat¬ 
eral teeth, note the bicuspid second lateral tooth. 
