diagnostic characteristics. Sutton calls
them nondescript, with much the same
intonation that a polite person might
use to admit that looking at a dozen cell
phone photos from a friend’s recent marathon got a little repetitive. Other larvae
have distinct traits, but look more like
cartoon aliens than adult fish.
“This one has eyes on stalks,” Sutton
says. On the screen he shows a long, pale
Y-shaped thingy with a plump bulge of an
eye atop each of the Y’s arms. Whatever
this creature looks like, a mutant ninja
gummy worm or a doodle from the dawn
of slingshot design, it does not resemble
the dragonfish it will grow up to be.
Marine biologists thus struggle with
problems comparable to that of a mammal biologist finding some newborn
feline but not knowing whether it’s a
house cat or a tiger. In some cases, it’s
as bad as not knowing whether a mewling little cutie is a kitten, a puppy or a
bear cub. And any worry over identification assumes that scientists can find the
creatures in the first place. Larvae don’t
nestle under a cozy rock outcropping but
are more like dandelion fluff blowing, or
maybe flying, in the wind.
During a research cruise sampling life
in deep water, Sutton managed to spot an
elusive youngster that resolved a long-standing muddle of the kitten-puppy-bear type. The youngster was developed
enough to be recognized as a whalefish
but hadn’t lost all of its baby features yet.
The transitional youngster allowed
Sutton and colleagues, including G. David
Johnson of the Smithsonian Institution
in Washington, D. C., to outline the whole
sequence from larva to adult for the species in 2009. Once called tapetails, the
larvae drag a long tattered streamer
behind them as if they’ve just emerged
from a tangle of seaweed. The larval
form, the adult female and the adult
male had previously each been identified
not only as separate species, but also as
species in different families.
Some of the misclassifications are
Like many other marine youngsters, this
larval Chaetodon butterfly fish starts life
by drifting off into open water.
Bulging eyes on two long stalks give
the larval Idiacanthus dragonfish (top)
a very different look from adults of the
same family (bottom, Bathophilus).
side effects of the power of evolutionary adaptation to environments. Larvae
have to survive as bite-sized nuggets in
open water, coping with perils different
from those faced by bigger adults flitting around reefs or nudging along the
seafloor. Outrageously long spines and
prickles on larvae may poke and choke a
predator. Johnson speculates that larval
streamers like those on the tapetails may
create a helpful ambiguity about whether
a larva is edible.
To human eyes, ambiguous characteristics can bedevil the study of even
some common fish. Sutton says that
the 300-plus known species of rattails
mature from larvae that basically look
alike. Rattails may not be familiar menu
items, and probably never will be under
that name, but the elongated, slinky
fish nicknamed for a stretched-out anal
fin play an important role on the abyssal plains of the seas. “Drop some dead
meat down there, and they’re usually the
first things that show up,” Sutton says. By
volume, the deep sea amounts to a lot of
habitat on a blue planet. Thus, he points
out, biologists can’t yet distinguish reliably among the larval forms of species of
one of the most dominant fish families
on Earth.
As difficult as larvae are to identify, their
actions are of interest for conservation
as well as basic biology.
A recent surge of larval research
addresses the challenges of drawing
borders for protected areas in the seas.
Declaring a teeming stretch of coastal
waters off-limits to fishing, for example, may not do much good if the new
reserve’s residents start out as larvae
somewhere with no protection. To complicate matters, the politics of protection
often play out differently at sea than
they do on land.
For instance, people protect Yellowstone and Yosemite to preserve gems of
terrestrial wilderness. But a marine
reserve where people aren’t allowed to
fish often has a lot to do with saving the
livelihood of people fishing nearby, says
marine ecologist Robin Pelc of the Monterey Bay Aquarium in California.
“Fisheries are in crisis,” she says. One
big hope for rebuilding and sustaining
them is to create fishing-free sanctuaries
with marine populations that grow large
enough to spill over the boundaries and
replenish fisheries beyond. Designing
such a reserve requires tricky balancing
acts, Pelc says. Borders have to embrace
enough area for populations to thrive,
yet the area can’t be so big that the riot
of life inside the borders stays within
those lines.
A modeling analysis confirms the idea
that reserves designed to enhance fisheries should be no larger than roughly
twice the target species’ larval dispersal
scale, Pelc and her colleagues report in
the Oct. 26 Proceedings of the National
Academy of Sciences. Proving that the
sacrifices made for a reserve really have
generated spillover has been tricky,
though. Most of the success stories feature shellfish, Pelc says. That trend may
reflect the tendency of shellfish larvae
not to travel particularly far and thus to
show up readily during monitoring just
beyond park borders.
In contrast, larvae that disperse
widely may indeed spill over the borders
of the park but continue on to scatter
over a broad swath of ocean. Far-flung
