Regenerating Limbs

Ever since I hauled that lobster with the red gummi crusher claw, I’ve been troubled by the idea of a creature dropping appendages and growing them back. It’s actually been surprising to see how many lobsters we haul that are culls, with limp, red extremities in the process of becoming a bona fide claw or leg or antenna. Apparently, this is a nasty little sight that the commercial lobster industry spares the consumers.  So I’ll use this venue to show what doesn’t make it to market.

Red gummi appendages (both the crusher and antenna)

Regenerated claw cooked (but not eaten)

A cull with new regrowth

Pincer claw almost entirely restored to its original size

Just a wee tiny sprout

Strange crusher regeneration (or possibly mutation? doesn’t the crusher look like it’s facing outward?)

So, how do lobsters do this??  I have no idea.  But in lieu of an answer to that question, I’ll provide some interesting facts that I dug up while researching.

• The only parts of lobster that will regenerate are its claws, legs and antenna (i.e., it won’t grow a head back).
• In some case, if it gets stuck on a rock or entrapped in some way, a lobster will spontaneously drop a claw as a means of escaping danger. This is called “throwing” a claw.  Lobsters have preformed fracture planes where the limb can break easily without serious loss of blood.
• It takes 3-4 molt cycles to grow a claw back to regular size.
• Mature lobsters have something called “bilateral asymmetry“. In the early larval stages of development, the pair of claws are actually identical — they’re both slender and the muscles structures are similarly capable of fast movements. The crusher/pincer distinction isn’t determined until the juvenile stage, and it isn’t the result of genetic encoding, but determined instead by extrinsic factors. Generally, the side that experiences the most sensory input will develop into the  crusher claw, which has muscular fibers designed for slower movements.
• Scientists find that a juvenile lobster is just as likely to develop the crusher on the right side as on the left, explaining the 50:50 ratio in adults. Once the asymmetry is determined, it’s fixed for life, and all regenerated claws will mirror their predecessors.
• The regenerated limbs will actually be indistinguishable from the original, in structure, shape, function, and the make-up of muscular fibers.
• Removing the eye stalks of a lobster is a technique for accelerating growth and regeneration. Apparently, a hormone is present in the eye stalks that responds to seasonal and other indicators, such as temperature and nutrition, to inhibit or activate molting cycles accordingly. Without these hormones, lobsters will molt more frequently and increase in size more rapidly — they may experience 75-100% weight gain in a single molting cycle. While loss of eye stalks may boost growth initially over the course of one or two moltings, long-term survival rates are not good. The eye stalk hormones are involved in a wide range of important functions, from regeneration to digestion, and without them the lobsters become pale in color, uncoordinated, disproportionately sized, and very susceptible to environmental stresses.

That’s all I can ferret out for now. More to come. And send along good info if you have any!

Diagrams of Lobster Anatomy (including larva stage) available here.

More shots of regenerating culls available on Good Morning Gloucester‘s photostream.

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