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Bassler, Ray S., et al. / Shelled invertebrates of the past and present, with chapters on geological history

Chapter VII: crustacean artisans and their homes,   pp. 210-228 PDF (8.4 MB)

Page 228

fragment; but he discards it for a complete specimen at the
first opportunity.
Well may we exclaim, "What order of intelligence is
this that can direct the being to which it pertains to take
up an anemone and make use of its protective powers;
even to distinguish between a useful one and a useless
portion of one; to twist and turn the anemone about in
the claws until satisfactorily fixed, shift its own position
as necessary, and when danger threatens from any quarter,
turn the hand batteries of nettle cells in that direction?"
Moreover, though at first warning the crab assumes the
defensive, with his weapons in hand, he does not foolishly
trust everything to them, but sensibly seeks flight if the
danger threatens to become overwhelming.
Secondarily, the anemones (the crab always carries two
if he can get them) are useful in providing food for their
master, because food material that once comes in contact
with their tentacles or sticky bodies adheres closely. When
this happens to the Lybia-borne anemone, the crab with
his second legs helps himself to what may tempt his
palate, even to the extent of delving within the anemone
to withdraw from its digestive cavity what it may have
too hastily swallowed. The crab in turn takes care to
keep the anemones always neat and clean and free of any
extraneous material that may adhere to them.
The other crab that similarly employs anemones as
instruments is Polydectus cupulifer. Polydectus is a most
sluggish individual, more prone to hide away and play
possum than to offer fight with his weapons, though at
times he raises them for purposes of defense. He is
supposed to use them more for the prehension of food,
and no doubt in a highly interesting manner, but we know
too little about him.
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