Introduction and Life Introduction and Life HistoryHistory

Horseshoe crabs are also Horseshoe crabs are also called “soldier crabs,” and called “soldier crabs,” and are arguably the most are arguably the most interesting creatures on our interesting creatures on our coast.coast.

Horseshoe crabs have been Horseshoe crabs have been called the most intensively called the most intensively studied marine invertebrate studied marine invertebrate in the worldin the world

In an evolutionary sense, In an evolutionary sense, the horseshoe crab has the horseshoe crab has changed very little since its changed very little since its first left trails between the first left trails between the Paleozoic tidepools Paleozoic tidepools hundreds of millions of hundreds of millions of years ago.years ago.

It is about as close as It is about as close as nature gets to a permanent nature gets to a permanent fixture in this dynamic fixture in this dynamic environment.environment.

A recently shed horseshoe crab has a beautifulA recently shed horseshoe crab has a beautiful olive-olive-colored shell that has no scratches or marine growth.colored shell that has no scratches or marine growth.

From the observations, juvenile crabs keep their shells From the observations, juvenile crabs keep their shells clean by plowing through the sand and spending clean by plowing through the sand and spending extended periods of time completely buried while at rest. extended periods of time completely buried while at rest. Sometimes they actually spend their first few winters Sometimes they actually spend their first few winters hibernating.hibernating.

Horseshoe crabs also burrow into the sediments to avoid Horseshoe crabs also burrow into the sediments to avoid being pushed around by tidal currents.being pushed around by tidal currents.

Their shell is kept clean by rapid growth, and they grow Their shell is kept clean by rapid growth, and they grow and shed most frequently when they are juveniles-up to and shed most frequently when they are juveniles-up to 5 times a year. This prevents the larvae of other 5 times a year. This prevents the larvae of other creatures from becoming permanently attached to their creatures from becoming permanently attached to their shells.shells.

The size and number of the species that grow on the The size and number of the species that grow on the horseshoe crabs is used to tell how old the crab is.horseshoe crabs is used to tell how old the crab is.

The creatures that clutch on to the horseshoe The creatures that clutch on to the horseshoe crab are there for different reasons. Some for crab are there for different reasons. Some for food, and others use the horseshoe crab as a food, and others use the horseshoe crab as a sole habitat.sole habitat.

Besides having many creatures on it, the shell Besides having many creatures on it, the shell of a HSC has many scars over it. Some scars of a HSC has many scars over it. Some scars come from people poking at it onshore because come from people poking at it onshore because it looks fierce. The horseshoe crab, however, is it looks fierce. The horseshoe crab, however, is completely harmless.completely harmless.

Gulls pounce on overturned crabs and tear Gulls pounce on overturned crabs and tear their gill and muscle tissue. The HSC’S get their gill and muscle tissue. The HSC’S get some revenge though, and harbor an encysted some revenge though, and harbor an encysted flatworm in the gull’s gut, which matures into a flatworm in the gull’s gut, which matures into a parasite in the gull’s intestine.parasite in the gull’s intestine.

Human InfluencesHuman Influences

In Chinatown, In Chinatown, female crabs are female crabs are sold for their eggs.sold for their eggs.

Horseshoe crabs are Horseshoe crabs are also used as bait. also used as bait. Fisherman freeze Fisherman freeze the females, saw the females, saw them in half, and them in half, and insert them into eel insert them into eel traps.traps.

Hitch-Hikers GaloreHitch-Hikers Galore Limulus Leech- found around the book gills and leg joints of Limulus Leech- found around the book gills and leg joints of

the crab, especially in older females that have not shed for a the crab, especially in older females that have not shed for a long time. Scientists used to think that the leeches were not long time. Scientists used to think that the leeches were not harmful, but have learned that being a parasite the leech harmful, but have learned that being a parasite the leech may weaken the crab enough to contribute to its eventual may weaken the crab enough to contribute to its eventual demise. The leeches leave very dark spots that are eggs in demise. The leeches leave very dark spots that are eggs in the pages of the crabs book gills . This weakens the surface the pages of the crabs book gills . This weakens the surface and allows the leakage of seawater and bacteria into the and allows the leakage of seawater and bacteria into the crabs body.crabs body.

Sponges- (Proifera) are filter feeders that need enough water Sponges- (Proifera) are filter feeders that need enough water to move the plankton to them, and prevent burial by to move the plankton to them, and prevent burial by siltation. They are found on the posterior of the crab when siltation. They are found on the posterior of the crab when the water is cool, and the crab is half buried in a dormant the water is cool, and the crab is half buried in a dormant stage.stage.

Flatworms- appear as small, pale pieces Flatworms- appear as small, pale pieces of fleshy tissue that move when you of fleshy tissue that move when you touch them. They can even stay with the touch them. They can even stay with the crabs during their molting process. Like crabs during their molting process. Like flatworms, Tube-building worms are also flatworms, Tube-building worms are also found on the crabs.found on the crabs.

Anemones and Hydroids are represented Anemones and Hydroids are represented as the 2 Coleocentrates. The Anemones as the 2 Coleocentrates. The Anemones are colorful and striped. They are found are colorful and striped. They are found on the crabs dorsal side. Hydroids are on the crabs dorsal side. Hydroids are also found on the Limulus, and need to be also found on the Limulus, and need to be observed underwater to see their observed underwater to see their exquisite shape.exquisite shape.

Other Hitch-Hikers Found On The CrabsOther Hitch-Hikers Found On The Crabs Snail Fur- stout and bristly Snail Fur- stout and bristly

creature whose velcro-like texture creature whose velcro-like texture contrasts to the smooth glistening contrasts to the smooth glistening shell of the HSC.shell of the HSC.

Mud crabs and Shrimp hide in, Mud crabs and Shrimp hide in, under, and around the shell of the under, and around the shell of the crab.crab.

Barnacles-they form a crown on Barnacles-they form a crown on the cephalothorx and it marks how the cephalothorx and it marks how deep the crab burrows into the deep the crab burrows into the substrate when its at rest for long substrate when its at rest for long periods.periods.

Mollusca- represented better on Mollusca- represented better on the crab than any Phylum. It is a the crab than any Phylum. It is a bushy, golden seaweed-like bushy, golden seaweed-like creature.creature.

Conclusion:Conclusion:

Most sluggish HSC’S Most sluggish HSC’S have the majority of have the majority of their shell and eyes their shell and eyes covered with fouling covered with fouling growth.growth.

The thick coating of The thick coating of the hitch-hikers the hitch-hikers seems to presage seems to presage the final demise of the final demise of the horseshoe crab.the horseshoe crab.