Wednesday, June 25, 2014

The Lobster Nursery, In Which We Are Pinched

The mysteries of the ocean never cease to amaze me.

A small, probably year-old lobster, plucked from his hidey-hole.  Don't worry, he went back after this pic.
Last week while I was home, I tagged along with some colleagues who were out collecting Crepidula fornicata and Crepidula plana -- slipper shells.  These mollusks have a very interesting life history -- they live in piles.  The one on the bottom -- the biggest one -- is a female.  The ones on the top -- the littlest ones -- are males.  The ones in the middle could go either way.  They can change sex from male to female, being protandrous hermaphrodites; not an uncommon thing in the animal world (nor is going the other way, from female to male).  The females release pheromones that prohibit the males above from changing sex; maintaining a neat little reproductive stack.

We had a good idea of where we could find Crepidula that weren't attached to big boulders; that would make collecting them difficult since they suck down to rocks and are hard to remove without killing them.  So we needed them on small cobbles; easy to collect and transport.  We hit the jackpot; easily collecting the number we needed in only about a half hour.  (Note; we have a special collecting permit from the State of Maine, and can only collect specimens for research or teaching purposes.  Don't collect organisms from the ocean without one; you can get into serious trouble with the law, and populations can be severely impacted if we all just take things for fun.)

Collecting under a perfect summer sky.
Sorting through the organisms.
Crepidula fornicata.  Notice the smaller one (the male) stacked on the larger one (the female).
Our job was done, but the tide was still going out, the sun shining.  A perfect opportunity to do some poking around in the many tidepools nearby.  We had some suspicions there would be a lot of interesting things in them.  Our first hint?  This very intriguing rock, with plenty of sand newly pushed out from under it:

What lurks under the rock?
What could be under there?  One way to find out!
Do you see what I see?  Look carefully!
Just as I suspected!  A small lobster!
The tidepools at this spot were chock full of juvenile lobsters.  Almost every rock we turned over had a small lobster hiding under it -- which would grouchily raise its claws at us, or walk away in disgust.  Some of the pools held lobsters simply walking around, seemingly unconcerned by our presence.

Lobsters have a fascinating reproductive cycle.  It starts when the female molts.  She finds a dominant male, then molts in his presence.  Given their reputation for ravenous cannibalism, this might seem surprising.  But the male can only give her his sperm packet while she's soft, so he has to be a tender lover, not a ferocious fighter, in this situation.  After she molts, he protects her for a few days, then she wanders off to live her own life (often being replaced by another female who's ready to grow a new shell).  She holds onto that sperm packet until the time is right, then fertilizes her eggs, which she holds on her "swimmerets" -- under what we call the tail of the lobster -- until they mature and are released as plankton during the warm months.

Planktonic lobsters go through three stages, which can last from a month to three months in total. During this time they hunt (being ravenous just like their parents), molt and grow, and are swept along by currents. When they reach the third stage, they start to look like tiny lobsters, can swim very well, and begin to look for a place to settle.  They start to avoid light, therefore swim away from the surface.  They make frequent forays to the bottom, to see if currents have carried them to a suitable nursery.  What does a baby lobster look for in a home?  The absolute best habitat for a tiny lobster, who's vulnerable to predation by fish, crabs, and what have you, is a shallow cobble-strewn area.  One with lots of nooks and crannies to burrow into. They'll settle for a salt marsh bank, or eel grass bed where they can dig a hole, but these aren't the best homes. Once they find a good spot, they settle, molt, and with that, aren't plankton anymore.  Tiny benthic lobsters can actually filter feed in a way -- they create a current and eat plankton that get carried into their burrows.  Eventually they grow large enough to be safe(r), and emerge from their hiding places to forage.

This juvenile stage might last a year, after which they move away from shore and act more like adult lobsters. So it's not unusual to find baby lobsters near shore, under cobbles.  Often, the east side of islands and peninsulas are great nurseries, because the prevailing currents carry lobsters to these areas, where they run into land and it's the end of the line.  For example, the east side of Damariscove Island is known to house many baby lobsters, but the west side is a desert.  There are over 100 hot spots known, and monitored, in the state of Maine.  The settlement of lobsters is a big deal up here:  big lobsters come from little lobsters, so knowing how they reproduce and grow is important.  There are plenty of interesting questions being worked on about lobster reproduction right now -- like does a hot spot for babies mean the area is a hot-spot for adults?

Just out for a little stroll.
Barnacles in a tidepool.  I love how they settle in the cracks of the rock!
Maine, the way life should be.
Now you might be saying "where is this magical place where baby lobsters are a dime a dozen?"  Well, for now, I think I'll keep it to myself.  Baby lobsters don't need a ton of people turning over their rocks every nice day.  But I'll let you in on a spot where you're likely to find them, if you promise to be very careful about turning over rocks, to put the rocks back without crushing anything, and if you don't take any lobsters home (you can't do it; it's illegal):  drive down to Land's End in Harpswell (all the way down Bailey Island).  You might just get lucky.

But if you do see a baby lobster, a word of caution.  They pinch.  They really, really pinch hard.  How might I know?  Well, I'm not above embarrassing myself.  For your entertainment, Janet catches a baby lobster (don't laugh too hard):

video

And he just kept holding on and pinching . . . .  He won.  He was small but potent.

Want to know more about lobsters?  I recommend The Secret Life of Lobsters by Trevor Corson. Check it out of your library, or find it at your local bookstore.  It's a great read.  Just watch those pinchy parts.

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