Page 38 - AlertDiver_Winter2013

LIFE AQUATIC
36 | WINTER 2013
effortless feed by a more mobile competitor. A mysterious
aspect of cone-shell biology is the organisms’ apparent ability
to alter the compounds in their venom with each injection.
Another critter renowned for deadly venom, which
paralyzes and shuts down prey’s respiratory systems, is the
blue-ringed octopus (Hapalochlaena spp.). However, blue-
ringed octopuses do not formulate their own venom. Instead,
a salivary gland near their beaks contains symbiotic bacteria
that produce maculotoxin (MTX) and hapalotoxin. With
no apparent effect on crabs, a favorite food, MTX is most
likely used for defense. MTX may also be used as a predatory
inhibitor in the octopuses’ eggs. The octopus releases
hapalotoxin into the surrounding water when it’s in the
vicinity of crabs. This allows the octopus to easily dismember
and consume paralyzed crabs without significant risk.
Fish
A study by the American Museum of Natural History
(AMNH) in 2006 estimated that there are more than 2,000
species of venomous fish. Some produce venom themselves,
and others have symbiotic relationships with toxin-generating
bacteria. Stonefish (Synanceia spp.) are a classic example of
venomous fish that produce neurotoxins capable of causing
pain sufficient to deter predators. William Leo Smith of
AMNH declared, “We don’t know when stonefish evolved,
but something really horrendous must have been out there to
make these 2-foot-long things develop such a strong toxin....”
Pufferfish, porcupinefish, mandarinfish, rabbitfish, fang-tooth
blennies, catfish and stingrays all produce defensive toxins,
some of which are lethal, and all of which are compelling
deterrents to assailants. As these proteins developed and
mutated, the production of ever-stronger venoms became
important elements of increasing survivability for many fish,
especially during juvenile phases. These valuable chemical
defense systems have even led to the evolution of a variety of
mimic species. These organisms use predators’ recognition of
the venomous fish or invertebrates to avoid predation without
having to invest resources in toxin production.
Predators, prey and competitors have battled for eons,
and their interactions continually shape marine ecosystems.
The evolutionary pressures that go with life underwater
have over time introduced and intensified chemical warfare.
Toxins unquestionably level the
playing field for creatures that
evolved without bones, armor,
spines or even the ability to move.
Through the long and random
history of the ever-growing tree of
life, chemicals have come to play
a common and vital role in the
survival of many, if not most, reef
species.
Toxins may also prove critical
in human endeavors. Ginsburg
acknowledged, “…[T]he
study of marine secondary
metabolites is important not only
to gain a better understanding
of the ecological functioning
and community structure of
the natural environment but
also to further expand the many
ecosystem services (including
pharmaceuticals, food products
and more) that marine natural
products afford us.” Regardless
of their specific form, function
or origin, toxins and venoms
have proven to be essential
components of healthy, albeit
poisonous, reefs. AD