Download The Loveless Winter of a Lightless Firefly

The Weekly Invertebrate, Invertebrate news articles and glossary
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October 23, 2000
BODY-PLAN
SPOTLIGHT
FOOD & FASHION
Mussel Beach
Echinoderms
The crinoids (right), sea
urchins, sand dollars, brittle
stars, sea cucumbers (below),
and sea stars are some of our
closest cousins in the
invertebrate world. Yet,
although we remain
steadfastly bilaterally
symmetrical (our left and
right sides are roughly mirror
copies), echinoderms change
their symmetry throughout
development, sometimes to
the point of appearing fickle.
Echinoderms begin life as
bilaterally symmetrical larva.
Even very different-looking
members of this group, like
sea urchins and brittle stars,
have similar larvae.
However, after a few days the
larva begins to develop the
unique five-fold radial
symmetry of this phylum.
This happens when part of
the embryonic coelom forms
a ring, and from this internal
ring radiates five branches of
what will become the
animal's "water vascular
system" (a basic organ
system unique to
Echinoderms). Having arms
in multiples of five arranged
around an oral-aboral axis,
sea stars retain this five-fold
design throughout their lives.
Sea cucumbers, heart
urchins, and sand dollars,
however, after passing
through a brief stage during
which they are radially
symmetrical, develop
bilateral symmetry again.
Photo: James Wood
A Micronesian crinoid
The Loveless Winter of a
Lightless Firefly
MEDFORD, MA -- Jennifer Rooney
and Sara Lewis at Tufts University
report on the curious mating behavior
of Ellychnia corrusca, behavior that
may explain this firefly's inability to
produce light in adulthood.
It has been believed since the early
1900's that E. corrusca spend the winter
as adults, and it is known that when
they do mate, males deposit highly
nutritious, protein-rich packets into
females along with their sperm.
Females use this packet
("spermatophore") to put on fat, unlike
some other fireflies, which use
spermatophores for maturing eggs.
But further information on the
probability of individual E. corrusca
surviving the winter and thir
commencement of mating in the Spring
required Rooney and Lewis to mark
825 individuals with dabs of paint and
follow their success through the
Massachusetts winter. What they
discovered was that adults do not mate
RALEIGH, NC -- If the
word "predator" and
"prey" bring to mind
cheetahs chasing down
impala or whales diving
for giant squid, you
haven't heard about the
slow-motion gore of
snails eating clams.
Gregory Dietl at North
Carolina State University
reports on the success of
the whelk Nucella
lapillus feeding on the
mussel Mytilus edulis off
the shore of Appledore
Island, Maine.
In general several
snails feed on clams.
Some lift their heavy
shells, drop it down on
the lip of the clam, and
crack a hole through
which they can insert
their mouthparts. Other
snails use a combination
of digestive chemicals
and rasping mouthparts
to bore a small hole in
the clam’s shell. This
process is not swift, and
if clams had brains, the
horror that would go
through them as they
endured about four days
of rasping and drilling is
difficult to imagine.
Nucella lapillus uses the
latter method, making
holes in the mussel shell
through which they
remove its flesh.
After collecting shells
along the beach, Dietl
checked each for
THE PHYLA
PORIFERA
CNIDARIA
CTENOPHORA
PLATYHELMINTHES
GNATHOSTOMULIDA
NEMERTEA
PLACOZOA
MONOBLASTOZOA
DICYEMIDA
ORTHONECTIDA
NEMATODA
NEMATOMORPHA
ACANTHOCEPHALA
ROTIFERA
GASTROTRICHA
KINORHYNCHA
LORICIFERA
PRIAPULA
ANNELIDA
ECHIURA
SIPUNCULA
POGONOPHORA
MOLLUSCA
PHORONIDA
BRACHIOPODA
BRYOZOA
ENTOPROCTA
ARTHROPODA
ONYCHOPHORA
TARDIGRADA
PENTASTOMIDA
ECHINODERMATA
HEMICHORDATA
CHAETOGNATHA
UROCHORDATA
CHORDATA
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The Weekly Invertebrate, Invertebrate news articles and glossary
These Echinoderms retain
evidence of their five-part
construction into adulthood,
although sometimes you have
to dissect sea cucumbers to
see it. One group of sea
cucumbers, the
Rhopalodinidae, as discussed
by Alex Kerr and Junhyong
Kim, continue development
past bilateral symmetry back
to radial symmetry. The
mouth in this group twists
around to lie adjacent to the
anus, and the animal, which
normally would have had
five-fold symmetry around
the mouth-anus axis, now has
ten-fold radial symmetry
around an point opposite the
mouth-anus stalk. As a result
of this developmental
sequence, they describe this
animal as having "bi-pentabi-decaradial" symmetry!
Journal of Experimental
Zoology (Mol Dev Evol) 285:
93-103.
in the fall, but enter the winter as
virgins. They survive the winter under
tree bark and at tree bases quite well -survivorship was calculated at around
90%. Beginning in the cool days of
early March, E. corrusca begin mating,
each pair staying joined for hours at a
time.
Members of the beetle family
Lampyridae -- the fireflies -- usually
mate after sundown. Flying males blink
species-specific patterns and look for
females hiding in the grass, blinking
back similar patterns. However, E.
corrusca mates during the day, with
males and females finding each other
by walking frantically over tree trunks.
Why E. corrusca has evolved away
from nocturnal mating and thus lightproducing organs may be because the
importance of getting an early start on
mating in the spring forces individuals
to begin at a time of the year when the
nights are prohibitively cold for any
activity. Shouldn’t someone tell them
about the pleasures of snuggling by a
fire with a glass of cognac?
Florida Entomologist 83: 324-334.
--------
Recently heard on "Who Wants
to Be a Millionaire:"
A starfish is missing which of the
following body parts?
A) Mouth B) Nerves
C) Stomach D) Brain
The contestant walked away with the
cash rather than venture a guess. Do
you know the answer?
--------
Attention Students!
Photo: James Wood
A sea cucumber spawning at
night
Don't know your exhalent canal from
your coxa? Refer to the Invertebrate
Zoology Glossary, in pdf or html
format.
complete, incomplete, or
repaired boreholes. (If
you're starting to wonder
whether your tax dollars
supported professional
beachcombing, keep in
mind that he collected
546 of these shells.)
From his measures, Dietl
calculated "Prey
Effectiveness" (PE). A
PE of zero would
indicate that the prey was
always unsuccessful at
escaping the predator,
EEwould be total prey
success. For the mussels
of Appledore Island, the
PE was 0.29, and older,
larger individuals were
the most successful at
surviving these attacks.
Better survival by
larger mussels probably
has a lot to do with their
thicker shells. However,
larger mussels may be
more effective with the
few behavioral deterrents
they can employ.
Mussels have been
observed to open and
slam closed their shells
when mounted by a
whelk, perhaps
occasionally pinching the
foot of whelks that
attempt to drill near the
thin lip of the mussel
shell. Mussels have also
been observed to extrude
their own foot and sweep
the surface of their
shells, a technique that is
probably quite effective
in removing whelks.
The Veliger 43: 319-329
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