Biology Reference
In-Depth Information
These few individuals contain by sheer chance a fraction of the total
genetic diversity of the mainland gene pool. The population that ul-
timately arises from the colonizers will be significantly di¤erent from
the mainland population and will tend to diverge even further through
the process of natural selection.
Another remarkable animal found on Isla Santa Catalina is the gi-
ant plant-eating chuckawalla lizard (
Sauromalus varius
). Throughout
mainland California and Baja California chuckawallas are dark gray, a
color that's excellent camouflage among the granite rock outcrops they
inhabit. On Isla Santa Catalina, however, they're marked with color-
ful blotches of red and yellow over their gray body. It's hard to imag-
ine what the survival advantage could be of such coloration, but per-
haps, as with the rattlesnake, it's the absence of large predators that
allows these gaudy lizards to survive just as well as their inconspicuous
gray cousins.
The trip was filled with memorable experiences for everyone, most
of them pleasant. However, a not-so-pleasant event involved a short-
spined pinkish sea urchin (
To xopneustes rosacea
) that I brought back to
the boat to show the nondivers. I passed the urchin up to someone on
deck, who then passed it on to Pedro Muñoz (Francisco's fourteen-year-
old son). As he held it in the palm of his bare hand he let out a yelp,
dropped the animal, and fell to the deck writhing in pain. When we
examined his hand we saw three tiny red punctures on his palm. All
species of sea urchins have small three-jawed pinching organs called
pedicillaria between their spines, which serve to keep the larvae of in-
vertebrates like barnacles from setting up housekeeping on the urchin's
shell. This flower sea urchin, it turns out, has unusually large pedicil-
laria that contain a painful toxin that must serve to keep urchin preda-
tors like triggerfish from even thinking about feeding on one more than
once. Instant pain is an excellent reason to leave them alone.
The intense experience of the ten-day expedition finally came to an
end. Hundreds of preserved specimens of all types were unloaded in
La Paz to be shipped back to the Academy. The more di‹cult task was
to get the live fishes and invertebrates back to Steinhart Aquarium as
quickly as possible. The first leg of the return trip was in a small pri-
vate plane from La Paz across the border into the United States, where
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