Congratulations to me: I’m a mom, well an Auntie
anyway. In addition to being a real Auntie of the incomparable, amazing, accomplished, Margaret (incidentally,
about to fete the completion of her first year), I have recently also become Auntie hundreds
of times over. Unfortunately, the number
of times over that I am an Auntie is now rapidly diminishing as my molluscan
nieces and nephews eat each other.
Whoops.
Whoops.
And except for the cannibalism, I couldn't be prouder! Actually the cannibalism is kind of cool, too, so maybe I just couldn't be prouder! Now, like any self respecting Auntie, I will subject hapless friends and strangers to stories, photos, and videos of my nieces and nephews doing THE MOST AMAZING THINGS! Because even though they are invasive brats (don't worry, I'm being responsible), they are the most amazing snails ever in the history of snails, because they are MY nieces and nephews.
This is video of one of the baby snails (Ocinebrina inornata) I am responsible for flipping itself over. So you're looking from above at an upside-down snail under a dissecting scope (~10x), which is why the plane of focus is so narrow. I am unable to tell you whether this particular snail is responsible for the death of any siblings, but chances are that she (or he) is. But, isn't that AMAZING? MY snail just flipped itself over!
Backstory: GO! About this time last year, I undertook cultivation of a
laboratory colony of snails that could star in my dissertation research. I’ll maybe talk more about why sometime later...
maybe. But the point is: I grow snails
now.
And in the case of my pseudo-offspring, the apple doesn’t fall far from the tree, and my snails are
a bit, well, poorly socialized. As I
mentioned, they eat their kin.
But, in their defense, it’s not entirely their fault. In my defense, the fratricide was not my
idea. It turns out, it is not unheard of
for some species to practice sibling cannibalism before and after birth.
Sand tiger shark pups consume all the siblings in their
mother’s womb, until only one pup remains. Witness:
Cannibalism at this stage can be a strategy for increasing the success of
surviving offspring. The strongest
individuals in a given brood, by consuming the weaker ones, get more food and grow more before birth/hatching etc. This increases the chance they will survive being a tiny shark alone in the world without wasting the energy that mom expended in making those other
babies, or having to compete with annoying siblings later in life.
Similarly, some snails are also known to get an early
start on the predatory lifestyle while still in their mommy’s egg capsule. These snails lay egg capsules (see below) that are
attached to a hard surface. Each capsule
has a variable number of fertilized eggs in it, and a number of unfertilized
“nurse eggs” or “trophic eggs”. Snails
will go through their larval development while still in the capsule, and feed
off these trophic eggs until they are competent to hatch out as perfect lil’
mini snails. It’s hard to tell in the
case of these snails if they restrict their diet to the trophic eggs, or maybe
occasionally slip and eat one of their siblings (or half-siblings). In 1949 (old references are the best/worst to
read), researchers at the Washington Dept of Fish and Wildlife counted
(COUNTED!) an average of 1,543 eggs in each egg case, estimating that only 1%
begin development, and even fewer make it to hatchin’ time.
Fambly Photo Album!
Here's some photo evidence from the crime scene. DESCRIPTION AND DISCLAIMER: These were taken with some dirty optics and poor lighting, sorry. Also it was kind of difficult to determine whether focus was achieved until too late. But you're looking through about 10x magnification on a dissecting scope. I aspire to higher quality at some point, but this is all you get for now.
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Early Life History Crime scene: A single egg capsule laid by Ocinebrina inornata, some of the juveniles have already hatched out as you can see the capsule is open at the top (left).
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OH NO! Snail casualty! That gaping hole in this baby snail shell is telltale evidence of sibling cannibalism, the portal by which a brother or sister suckedthisguysgutsout! This dude is about 0.5mm long. Note also that, when the hatch out, the snails first have this smooth white shell with a not very pointy top. To learn why read: The Ballad of The Veliger.
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This one is a survivor! Slightly older, this snail is perched on the edge of a barnacle many times his (or her) size. As they grow and add new whorls, the snails, even though they are tiny (~2mm), really start to look like mini adults.
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Old habits die hard, apparently, because the winners keep on
chowing on their buddies after they leave their egg cases. I’ve seen a lot of my babies go this way, and
it’s sad. I do my best to make sure they
have enough non-sibling nourishment so they won’t be tempted into
recidivism. I’ve been told the best
thing to feed them is extremely young barnacles, ones that have just settled
out of the plankton. Unfortunately, the
timing is off this year, and I have plenty of adult barnacles, and some
appropriately sized baby mussels. I
think they can tell that Auntie’s finger wagging just doesn’t carry the same
authority as an actual parent, and my efforts at discipline and redirection aren’t
working. So let’s hope for the sake of
my research that this is just a phase.
