April, 2000 
SCAMIT Newsletter 
Vol. 18, No.12 
pending further analysis of the dorid 
nudibranchs as a whole. This leaves 
Cryptobranchia, at least temporarily, as a 
paraphyletic group. 
Blue mussels, mentioned again in the last NL, 
were also considered by Penny & Hart (1999). 
There I was forced to agree with Dr. Jim 
Carlton that a recent paper did not provide the 
evidence to allow separation of Mytilus 
trossulus from M. galloprovincialis on our 
coast without chemotaxonomic information on 
each specimen - a dour prospect. Penney & 
Hart, while dealing with M. trossulus and M. 
edulis in Newfoundland, report similar findings 
from a different perspective. They found that 
genotype and phenotype covaried, and that the 
genotype of hybrids was directly demonstrated 
in intermediate shell morphologies. Although it 
is not necessary to do chemotaxonomic 
analyses to establish the genetic composition of 
the specimen, there is a continuum of 
morphological variability. Any distinction 
between the species is likely to be reflected 
only statistically. Such a situation, while it may 
be helpful to the commercial shellfish industry 
in Newfoundland, won’t help us tell what 
species any given specimen belongs to. 
Somewhere in the morass of morphological 
variability may lie a series of key characters, 
even morphometric ones, which will allow 
accurate speciation of individuals. For now 
these remain obscure, although clearly, species 
identity is represented by shell characters even 
in these closely related congeners. More papers 
are coming on this issue. 
Dietary preferences of juvenile red octopus, 
Octopus rubescens, were examined by 
Anderson et al (1999). The animals they 
investigated averaged less than 2cm in mantle 
length, so were much smaller than most O. 
rubescens we encounter in trawl monitoring 
efforts. They were sampled and evaluated 
while using beer-bottle dens in Puget Sound at 
depths between 20-25m. The animals, at least 
at this stage, seem to be mollusk specialists, 
eating mostly small gastropods with the 
occasional clam thrown in. Some of the shells 
may actually have hosted hermit crabs, but no 
evidence of crab remains was found in 
investigated dens. The bottles were 
experimentally manipulated and rates of 
consumption could be calculated from the 
results of placement and subsequent harvest of 
bottles with known soak times. 
On deeper soft bottoms in the southern 
California bight the animals can also be taken 
in bottles, cans, and other partially enclosed 
debris, but also have been seen to use shallow 
depressions in the soft bottom as refuges. 
When approached in a submersible they 
attempt to hide in these depressions. If the 
approach continues they stand up tall and try to 
bluff the intruder away prior to fleeing 
themselves. These may be only temporary 
housing while hunting, but the possibility 
exists that shallow water object denning is a 
response to visual predation risk not present in 
darker waters offshore. It would certainly be 
less limiting to the animal to be able to hide in 
any unoccupied burrow mouth in the complex 
biologically altered bottoms at 200+ feet. 
Where den material is in short supply, 
temporary denning in irregular bottom features 
may be a common, if not optimal, condition 
[these latter comments are based on the editors 
experience with the species, and are not part of 
the paper]. 
Predator avoidance and food gathering both 
play roles in a thesis advanced by Marcotte 
(1999) concerning the importance of visual 
perception in generating diversity in the 
geologic past. He hypothesizes that high 
oceanic turbidity, fluctuating cyclically on a 
400my scale, lead to major extinction events, 
and major changes in evolution of at least the 
arthropods in the phanerozoic. 
Turbidity is only the proximal agent and it 
reflects large scale changes in the ocean- 
atmosphere system and in tectonic plate 
arrangements. During periods of plate 
convergence and fusion, turbidity and 
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