Download WHALE WORMS

WHALE WORMS
Scientists working at the Monterey Bay Aquarium Research Institute (MBARI) in 2004 discovered two new species of
unique tubeworms that feed on the bones of dead whales. The worms are in a new genus called “Osedax,” which is
Latin for “bone devourer.”
The worms’ bodies and feeding strategies are very different from most animals. They have no eyes, legs, mouths or
stomachs, but they do have colorful feathery plumes and green “roots.” The reddish plumes extend into the water and
act as gills. They connect to a muscular trunk, which can be withdrawn into a transparent tube when the worms are
disturbed. At the other end of the trunk, hidden inside the whale bone, the body widens to form a large egg sac. The
green roots, branching off from the egg sac, grow into the whale bone similar to the way garden plant roots spread into
the ground. They are filled with symbiotic* bacteria that break down the fats and oils inside the bone, providing food
for the worms. You can find more information and pictures of whale worms on the MBARI web site.
Diet
nutrients supplied by symbiotic* bacteria breaking down oil and fats in whale
bone
Size
1- 2.5 inches (2.5-6.3 cm) depending on the species
Range
unknown
Relatives
vent tube worms; Phylum: Annelida; Class: Polychaeta
Conservation Notes
Whale carcasses—or whale falls, as they are called—represent a massive
input of food into the generally food-limited environment of the deep sea. One
whale fall can provide as much organic material as thousands of years of
marine snow, the organic debris that drifts down from surface waters to
sustain life in the deep.
Commercial whaling which began in the 1800s may have driven some whale
worm species to extinction. Many whale populations are estimated to be only
ten to 25% of their historical levels despite the 1982 International Whaling
Commission’s moratorium on commercial whaling. Fewer whales means
fewer whale falls and less habitat for whale-fall species such as whale worms.
Cool Facts
Whale skeletons support so much life because they contain an enormous
amount of oil. Large whale bones can be more than 60 percent oil by weight,
for example a 90 ton whale is estimated to have 5 tons of oil in its bones, a
veritable feast for oil-eating bacteria.
Scientists who discovered these tube worms were puzzled by the lack of male
tube worms until a close-up examination of female worms revealed
microscopic males living within their bodies. They looked as if they had never
developed past their larval stage but they contained copious amounts of
sperm. As many as 50-100 males may reside in one female. MBARI scientist
Robert Vrijenhoek said “These worms appear to be the ecological equivalent
of dandelions—a weedy species that grows rapidly, makes lots of eggs, and
disperses far and wide.”
After a whale skeleton has been consumed, all the worms at that site will die
off. Before this happens, they must release enough eggs or larvae so that some
tiny proportion will be transported by the ocean currents and survive until
they can find and colonize another whale carcass.
WHALEFALL
Whale falls—islands of abundance and diversity in the deep sea
In the deep bottom waters of Monterey Canyon, many food webs are sustained
by a slow drizzle of organic particles and detritus known as marine snow. But
every now and then this rain of debris includes a really big food “particle” in the
form of a dead whale. One whale fall can deliver as much organic material as
several thousand years worth of marine snow.
In February of 2002, MBARI researchers Robert Vrijenhoek and Shana Goffredi
discovered a recent whale fall while exploring the outer portion of the Monterey
Canyon with MBARI’s remotely operated vehicle, Tiburon. They returned to the
site in October 2002 with Craig Smith, a University of Hawaii professor who has
studied whale falls for nearly twenty years.
Photomontage of the whalefall in Monterey Canyon obtained during a February 2002 dive using the ROV Tiburon. The red "fuzz"
is thousands of deep-sea worms growing on the whale bones.
Based on repeated observations of whale falls off of Southern California, Smith
has seen a consistent pattern in the development of biological communities
around whale falls. When a large whale dies, its body often sinks directly to the
sea bottom, especially if the animal is undernourished. Within days, active
scavengers, such as sleeper sharks, rattails, hagfish, and amphipods, converge
on the new food source and voraciously remove the flesh from the bones (Smith
has estimated consumption rates of 40 to 60 kilograms of flesh per day). In many
cases the whale is stripped to the bone in a matter of months.
Within a year after the whale fall, the whalebones and nearby organically
enriched sediment typically become infested with huge populations of polychaete
worms and unusual crustaceans, as well as molluscs and other invertebrates.
Worms often carpet the seabed at densities of up to 45,000 animals per square
meter—higher densities than in any other deep-sea environment. Animals in this
“enrichment-opportunist” community feed directly on organic material in the
whalebones and surrounding sediment. Many of these animals appear to be
unique to deep-sea whale falls, and many are new to science. Although the
animals appear in extremely large numbers, only a few different species are
present, a situation similar to that observed near other concentrated sources of
organic material in the marine environment, such as sewer outfalls and salmon
pens.
About a year or two after the whale fall, most of the easily digestible organic
material has been consumed. However, sulfur-reducing bacteria continue to feed
on fats and oils deep within the whale bones. This process gradually releases
hydrogen sulfide, which provides the basis for a third-stage, “sulphophilic” (sulfurloving) whalefall community.
This sulphophilic community is remarkable for a number of reasons. Instead of
being based on photosynthetic organisms, such as phytoplankton, it consists of a
self-contained food web based almost entirely on energy from chemosynthetic
bacteria. This food web provides many different ecological niches. In addition to
the chemosynthetic bacteria themselves, there are animals that graze on the
chemosynthetic bacteria and organisms that live off of chemosynthetic bacteria
growing within their own bodies, as well as the more typical scavengers and
predators.
Third-stage whale-fall communities are often amazingly diverse. Up to 190
different species of macroscopic bottom-dwelling animals have been found on a
single whale skeleton. Many of these species are specifically adapted to utilize
whale-falls as a food source and substrate. These communities can also be
amazingly persistent—at least one large whale-fall community has apparently
lasted more than 50 years.
In some ways, late-stage whale-fall communities resemble communities at deepsea hydrothermal vents and cold seeps, where chemosynthetic bacteria also
form the basis for unusual, self-contained food webs. About ten to twenty percent
of the roughly 200 sulphophilic species found at whale falls are also found at
underwater hydrothermal vents and cold seeps, respectively. However, the
majority of species found in each type of environment are unique. Since many of
these organisms are difficult to identify based on their appearance, researchers
at MBARI are using genetic and molecular tools to understand the evolutionary
patterns among whale-fall communities, and to determine relationships between
animals at whale falls, seeps and hydrothermal vents.
Crabs and an octopus living on the skull of the dead whale in October 2002. The spherical weight and yellow line anchor a homing
beacon that that helps researchers find the whalefall on subsequent dives.
Thirty-million-year-old assemblages of fossil clams and whale bones suggest that
whale-fall communities have been around at least as long as whales themselves.
This persistence is particularly impressive because each whale-fall community is
based on a transitory food source. Sooner or later, planktonic larvae of
invertebrates at one whale fall must somehow find and colonize a new whale in
order to survive. But whale falls might be relatively common. Smith estimates
that, based on current whale populations and whale-fall community persistence,
dead whales may occur roughly every 5 to 16 km along the seafloor off the
Pacific coast of North America. Distances such as these are easily traversed by
planktonic larvae.
The recent whale fall in Monterey Canyon is particularly interesting because it lies
in deep water (2,891 meters). At this depth mobile scavengers are probably less
active, but sulphophilic organisms may appear sooner. Smith and the MBARI
scientists are currently analyzing the results of their latest visit, to learn more
about the persistence and distribution of these unique benthic communities.
—Kim Fulton-Bennett
December 2002