Jim Scaia sent me an article today talking about the number of "dead" horseshoe crabs washing up along Atlantic Coast shorelines.
It's funny because my husband and I just got back from a walk along Old Mill Point's beaches and were discussing the same thing.
Without question, there seem to be more this year than previous years washing ashore, but not sure what exactly that indicates. Or how many of these crabs are really "dead" and how many are "molts" - horseshoe crabs shed their entire exoskeleton, legs, lung coverings and all.
I've included excerpts of the article he sent.
Hope this helps some people feel better about the sheer volume of crab shells we have on our beaches.
Without a doubt the number one nature question concerned
people ask during September - what's up with all the dead crabs on the
beach? A disturbing sight to see dozens or sometimes hundreds of unmoving
creatures.
Thankfully, the answer has nothing to do with a loss of life. Quite the opposite, it's all about a continuation of life.
Most of the "dead" Horseshoe Crabs that people see on beaches this time of year... are probably not dead at all, but actually empty shells. The shells are molts. Horseshoe crabs grow by molting.
As a Horseshoe Crab matures and increases in size, it will shed its old exoskeleton (outer shell or skeleton) and form a new, bigger one, leaving its old shell behind on the bottom of the bay. The animals increase in size by 25-30% with each molt.
It doesn't take long for the old exoskeleton, including tail, legs, abdomen, gill coverings, eye coverings, and everything else, to wash ashore for curious people to stumble upon. Although some crabs might be dead and in the mix within a wrack line, most of the time people are coming across a molt of a juvenile. Horseshoe Crabs need to shed at least once a year as they grow to adulthood.
For most folks, it's a difficult task to tell an empty molt from a lifeless crab. A molt is often one intact piece of shell appearing just like a complete crab. Some of the molts may even fill up with sand or water to make the empty shell weigh about the same as a whole crab. It's surprisingly easy to mistake a molt for a dead Horseshoe Crab.
With careful observation, though, it can become easy to find the truth. Pick up the shell and look for an opening or split along the front ridge of the shell. If the seam is broken, then in all likelihood it's a molt. Unlike a true crab, like a Blue-claw Crab, which will back out of its old exoskeleton, a Horseshoe Crab will thrust forward to divide the upper shell with the bottom half.
Also, the color of the shell is going to be pale and in some cases nearly translucent. In contrast, a dead crab is going be dark in color and have a strong saltwater-stench with many flies or gulls being attracted around the poor creature.
While there is still a lot of mystery about the juvenile life stage of Horseshoe Crabs, scientists are pretty sure that many young animals tend to stay near where they hatched for their first two years and then gradually move to deeper waters of the bay as they mature. Scientists are also pretty confident that many crabs of the same age molt at the same time of the year. According to wildlife biologist, Robert E. Loveland in the book, Limulus in the Limelight: A species 350 million years in the making and in Peril?, "there is evidence that a particular size class of crabs will all undergo simultaneous molting." Former Horseshoe Crabs shells often wash up on beaches at the same time and at the same size.
It's funny because my husband and I just got back from a walk along Old Mill Point's beaches and were discussing the same thing.
Without question, there seem to be more this year than previous years washing ashore, but not sure what exactly that indicates. Or how many of these crabs are really "dead" and how many are "molts" - horseshoe crabs shed their entire exoskeleton, legs, lung coverings and all.
I've included excerpts of the article he sent.
Hope this helps some people feel better about the sheer volume of crab shells we have on our beaches.
Thankfully, the answer has nothing to do with a loss of life. Quite the opposite, it's all about a continuation of life.
Most of the "dead" Horseshoe Crabs that people see on beaches this time of year... are probably not dead at all, but actually empty shells. The shells are molts. Horseshoe crabs grow by molting.
As a Horseshoe Crab matures and increases in size, it will shed its old exoskeleton (outer shell or skeleton) and form a new, bigger one, leaving its old shell behind on the bottom of the bay. The animals increase in size by 25-30% with each molt.
It doesn't take long for the old exoskeleton, including tail, legs, abdomen, gill coverings, eye coverings, and everything else, to wash ashore for curious people to stumble upon. Although some crabs might be dead and in the mix within a wrack line, most of the time people are coming across a molt of a juvenile. Horseshoe Crabs need to shed at least once a year as they grow to adulthood.
For most folks, it's a difficult task to tell an empty molt from a lifeless crab. A molt is often one intact piece of shell appearing just like a complete crab. Some of the molts may even fill up with sand or water to make the empty shell weigh about the same as a whole crab. It's surprisingly easy to mistake a molt for a dead Horseshoe Crab.
With careful observation, though, it can become easy to find the truth. Pick up the shell and look for an opening or split along the front ridge of the shell. If the seam is broken, then in all likelihood it's a molt. Unlike a true crab, like a Blue-claw Crab, which will back out of its old exoskeleton, a Horseshoe Crab will thrust forward to divide the upper shell with the bottom half.
Also, the color of the shell is going to be pale and in some cases nearly translucent. In contrast, a dead crab is going be dark in color and have a strong saltwater-stench with many flies or gulls being attracted around the poor creature.
While there is still a lot of mystery about the juvenile life stage of Horseshoe Crabs, scientists are pretty sure that many young animals tend to stay near where they hatched for their first two years and then gradually move to deeper waters of the bay as they mature. Scientists are also pretty confident that many crabs of the same age molt at the same time of the year. According to wildlife biologist, Robert E. Loveland in the book, Limulus in the Limelight: A species 350 million years in the making and in Peril?, "there is evidence that a particular size class of crabs will all undergo simultaneous molting." Former Horseshoe Crabs shells often wash up on beaches at the same time and at the same size.
