Posted by: Bob Fisher | May 3, 2009

The Crab Lady of Cape Cod

We spot her as we crest the sand dunes that give onto the barrier beach of Cape Cod Bay. A solitary figure against the merging blues of sea and sky, she is pacing slowly back and forth beside an inter-tidal pool. Even from a distance, her body language – and what is an unmistakable and pragmatic Tilley hat – suggest both patience and purpose. Occasionally she stops, turns, and looks out to sea. And then, as if time were not of the essence, she peers into the tidal pool or scans the beachfront from which the sea has made its twice-daily retreat. There is something about the calm and careful way she moves that implies an expectation of things to come, in good time.

Inter-tidal Life

From our vantage point on the dunes, we look out over an uninterrupted expanse of tidal flats. Sandbar islets, shaped by rivulets of sea water flowing towards the outgoing tide, provide a visual perspective for the reckoning of time and distance. Having receded several hundred metres, the low tide has uncovered a marine habitat that is accentuated by nutrient-rich sea grasses and other aquatic plants, all of which in the fullness of sea time will soon be inundated again with marine life. This is a time and space for examining what the sea leaves behind; and on this bright, cool May morning we are among the few visitors or residents who have come to the shore to do so. At the moment however we are unaware that lying buried in the wet sand that stretches for kilometres are many members of a unique marine species to which we will shortly be introduced.

Experiential Learning in Cape Cod

Our day begins at the Cape Cod Museum of Natural History. Located in the model mid-Cape town of Brewster, the Museum is a 17,000-square-foot building surrounded by indigenous flowering trees and gardens. Its two floors of exhibits serve as an introduction to the geological and natural history of the Cape, which was fashioned by glaciers over 20,000 years ago. Interactive exhibits and a library of resource materials give the visitor an in-depth view of this unique coastal environment that is subject to particular, and to some extent urgent, environmental concerns. The relentless force of nature is depicted in visual displays that clearly show the dramatic coastal erosion that has taken place in recent years. The Cape as it was 10,000 years ago is contrasted with what it is predicted to look like in another 8000 years. The thesis is clear: this is an area on the planet in which human habitation must deal head on with the perpetual transformations that result from wind, water, and weather. In addition, the johnny-come-lately (but no less significant) impact of human intervention in this shifting environment is also a key theme of the displays.

Among the informative exhibit areas in this very user-friendly and low-key museum is the Marine Room where a number of aquaria contain typical and unusual Cape Cod species such as American eels, spider crabs, mummichogs (one of the most important fish in salt marshes), and oyster toadfish. Especially captivating is the tall and theatrically-lit aquarium containing the latest residents, moon jellies. The grace and artistry of these elegant, translucent creatures is hypnotic. Their rose-coloured diaphanous shapes move in unison in an gentle aquatic dance that is hard to reconcile with the rigours of their ocean home. They also contrast with but also compliment their neighbours the great whales, another focal point of the museum.

Upstairs, the Marshview Room with its floor to ceiling windows is a clever architectural stratagem that blends inside and outside. This time it is the museum visitors who are contained, gazing out at across the marshes to Cape Cod Bay. Birds attracted to the marshy environment just beyond the glass can be observed and admired undisturbed.

Like numerous other wildlife reserves to be found in this popular holiday destination, the Cape Cod Museum of Natural History, which was founded in 1954, gives substance and depth to a visit to the Cape. But its principal exhibits extend far beyond the walls of the museum itself over 380 acres of terrain, and along a series of nature trails that meander through upland vegetation as well as cultivated and non-cultivated wildflower areas. From brackish marshes to a beech forest, to Stoney Brook – where in the spring and early summer herring make the transition from their ocean home to freshwater spawning grounds – to Cape Cod Bay, this is a nature reserve in which the visitor is constantly in transit.

The trail from the Museum has led us through an upland pitch pine forest – the dry salt air feels pleasant on the skin and the path is soft underfoot – and over a long boardwalk traversing the salt marsh that separates this section of the Cape from sandy Wing Island. (This is a prime bird-watching locale especially during the migratory seasons.) We pass by a sassafras grove, and then another coastal woodland, before reaching the glorious dunes and seashore for which the Cape is so well-known.

A First Encounter

Standing on the crown of the dunes, we feel at liberty to wander in any direction we wish but the presence of the lone person we have glimpsed in the distance is like a human lure – like attracts like I suppose – and so we descend to the exposed ocean floor and move towards her. It takes several minutes for us to wend our way around the tidal pools and our approach is gradual. But as we get closer, I can see that she is pleased that we are coming.

Drawing nearer, we see a number of reddish-brown objects lying at her feet. Our curiosity increases. As we walk around the tidal pond beside which she is standing, I can see that she is all smiles and eager to introduce herself; her welcoming demeanor eases the awkwardness of the lengthy approach. Her name is Maureen Johnson and she is here today in her role as a volunteer at the museum and as a self-taught marine biologist. Maureen is a keen admirer of a very special marine species that is found on the eastern seaboard, the Horseshoe Crab. And around her feet are five moults of crabs she has found washed up on the beach in the area. She has gathered them in order to explain to passersby the anatomy, reproduction, commercial uses, and, above all, the importance of this unique marine animal. After some initial light conversation, Maureen begins to introduce us to the Horseshoe Crab.

It is clear that she is passionate about the species whose scientific and melodious name is Limulus polyphemus. In extolling the virtues of the Horseshoe Crab, Maureen refers to it as “this ancient mariner” and later as “a jewel of the sea.” She obviously cares deeply about it and about what it represents. She recalls the exact moment when she first encountered the Horseshoe Crab. As a little girl growing up in New Jersey, she remembers being on a beach with her mother and coming across one lying upside-down in the sand its many legs reaching in vain for something tangible with which to right itself. As many might do who are unacquainted with the Horseshoe Crab, Maureen’s mother recoiled in alarm at this strange creature and reacted with even more fear when Maureen wanted to examine it closely, pick it up, and turn it over. For Maureen, however, the Horseshoe Crab was a fascinating animal and she was instantly attracted to its intricate structure and beauty. Definitely not of the creepy crawly school of thought, she was instantly smitten with this fascinating species, and intuitively understood its vulnerability. And she still does.

The Horseshoe Crab is one of those species in nature that epitomizes all that is salutary and well-integrated. As a symbol of superior adaptation and the interconnectedness of life forms, it is also an example of a species that merits greater study and understanding. And this is why Maureen is on the beach today.

One of the oldest creatures on the planet – it preceded the dinosaurs by 100 million years – the Horseshoe Crab is an eclectic marine creature and a true generalist in the natural world; and yet it is subject to the precariousness of the milieu in which it thrives. Even though it has existed for so long on this evolving planet and is able to survive in a wide range of environmental conditions, if upended and stranded by the surf on a beach in the sun the Horseshoe Crab will not make it through the day.

And this happens frequently on beaches along the eastern seaboard, unless a little girl (or whoever) comes along and gently turns it over.

In Delaware Bay, home to the largest population of Horseshoe Crabs, 400,000 die in this way each year before someone can give them a helping hand. Of course there is no reason to be afraid of their 10 legs waving helplessly in the air; the Horseshoe Crab is quite harmless. But you must be careful of its tail (telson) which is quite delicate; of the Horseshoe Crab’s highly sensitive and specialized 10 eyes, one is located along the top of the tail. To “flip” a Horseshoe Crab you simply take the animal by one side of its shell (carapace) and turn it over.

As Maureen lifts up one of her specimens (the Horseshoe Crab moults 17 or 18 times during its life) and shows us the complex symmetry of its underside, she points out the crab’s flange, its small semi-hidden bristly mouth, and its membrane gills that resemble thin layers of parchment. When she describes the total motion of a Horseshoe Crab swimming on its back as it is wont to do – legs, gills, spines, rudder-like tail moving in complex synchronicity – she describes it as “comical … a prehistoric comedy.” To me the amazing integration of what appear to be quite dissimilar organs is fascinating and she and I agree upon “a fantasia of motion” as an additional descriptor. The moulting process of a Horseshoe Crab is a fascinating lesson in itself. As it outgrows its shell, a soft, wet, wrinkled shell forms inside the old one. Maureen explains that the arthropod, as she refers to it in one of her more scientific moments, buries itself in the sand in order to protect itself from predators. Taking in huge amounts of water it swells and splits open the front of the shell, and thus having renewed its body tissues, it crawls out into the mud. It then continues to take in water thus increasing its new “suit of armour” by one quarter. When this new carapace hardens, it is safe for the animal to emerge from its hiding place.

When the Horseshoe Crab comes ashore to breed, it moves on land with five pairs of walking legs. The back pairs thrust it forward and the extra-long legs resembling ski poles leave distinctive undulating patterns in the sand, which can mystify uninformed beach strollers. Horseshoe Crabs like a full moon. Although the spawning season varies according to latitude, peak spawning occurs during evening high tides on beaches in bays and coves that are to a certain extent protected from surf. Not unlike the mating rituals and promenades of humankind, male Horseshoe Crabs cruise the beachfront attracted by the pheromones of the sweet-smelling females who each year will deposit in the sand about 80,000 eggs in clusters of 4000 during approximately 20 visits to the beach.

The physical structure and behaviour patterns of the Horseshoe Crab put it in a class by itself both figuratively and scientifically. Maureen wouldn’t fault you for thinking it was a crustacean, but Limulus polyphemus is in fact one of only four species in the world that belong to a class called Merostamata. The Horseshoe Crab is found along the Atlantic Coast from the Gulf of Mexico to Maine; and its Japanese cousin, the helmet crab (kabutogani), is considered a national treasure in that country. A legendary species in Japan, the helmet crabs are said to be the reincarnation of brave warriors who achieved supreme honour by sacrificing their lives in battle. This treasure even has a haiku poem written about it.

Have continued to survive in the Kasoka waters

Spring and Autumn a friend

A learned person gently comes, steps carefully.

The Blood Donor Crab

From Maureen’s initial reference to “this blue-blooded crab” I assume she is just expressing the high status she attributes to the Horseshoe Crab among the creatures in the natural world. However as she later explains, the Horseshoe Crab does indeed have blue blood. Unlike the red blood of other animals, which contains iron, the Horseshoe Crab truly has blue blood owing to the copper in it. But its blood is even more unique in that it contains a chemical called Limulus amoebocyte lysate or LAL. This chemical causes the Horseshoe Crab’s blood to quickly clot when it comes into contact with even the most minute impurity or toxin. Bacteria per se are not of course a bad thing. They exist everywhere in almost every living organism and the environments in which these organisms live, and they are critical to the degrading of natural wastes. But even non-pathogenic bacteria (non-disease-creating) can be dangerous if they enter those parts of the body that are normally bacteria-free. This is the case in the human bloodstream as well as that of the Horseshoe Crab which has no immune system. Even though this species lives in the ocean, the largest bacterial “soup”on the planet, it has developed a primitive form of an immune system. If common marine bacteria such as fungi or viruses enter the Horseshoe’s bloodstream, the components of LAL bind themselves to the intruders and render them inactive. This phenomenon was discovered in the 1960s by Dr. Frederik Bang, a marine biology researcher working at Woods Hole, the renowned research centre off the south-west tip of the Cape. Bang injected common marine bacteria into the bloodstream of Horseshoe Crabs which caused massive clotting as a result of the endotoxin (a powerful toxin inside the cell of a bacterium). He was subsequently able to isolate and identify the clotting phenomenon and the chemical that caused it in the blood cells of the Horseshoe Crab. He named it LAL.

A similar untoward reaction in the human bloodstream – in the form of fevers – was detected over 50 years ago when injections of medications were given to humans in what was presumed to be sterile solutions. Scientists now know that those early so-called sterile solutions still contained residual bacterial components. In order therefore to test the purity of such solutions, new medications were screened for pathogens by injecting them into rabbits. Unfortunately for the rabbit, impure solutions were detected if the animal developed a fever – or worse. Today however, new drugs are tested for possible contamination by injecting them into a small quantity of the blue blood of the Horseshoe Crab, which as it does in the animal itself immediately clots, indicating the presence of impurities.

These “living fossils” therefore serve an indispensable and life-giving role in modern medical science when their blood is used to produce a commercial “LAL reagent.” For such purposes, Horseshoe Crabs are collected by hand in shallow water and transported to “blood banks” where 30 per cent of their blood is removed. Some may even make the trip more than once, but are only “bled” once a year. (Maureen assures us that they suffer no ill effects in the process.) In addition to its blood donations, the Horseshoe Crab with its amazing multiple eyes and day and night-time vision, has also contributed greatly to research into how human vision functions. Furthermore, chitin – a natural polymer found in the Horseshoe Crab’s shell – is widely used to coat surgical sutures because of its benign chemical composition. The material is also used as wound dressing for burn victims; such patients are especially susceptible to infection and chitin’s extraordinary compatibility with living tissue helps in healing burn wounds.

An Environmental Lifesaver

As Maureen continues to explain why the Horseshoe Crab is such a phenomenal species, she becomes more and more engaged in her subject. It is quite clear why her enthusiasm, knowledge, and the imparting of that knowledge to strangers on a beach has an exponential effect. Occasionally she picks up the moults of the crabs at her feet to point out various details or to explain some other intriguing aspect of the animal. As she does so, she handles the body parts with great care and respect as if she were holding a live crab.

Fitting the three body divisions together, a manoeuvre that requires considerable motor skills, she demonstrates the intricacy of this superbly articulated animal. While doing so she also begins her explanation of the important role the Horseshoe Crab plays as a prime provider to the over 500,000 migratory shorebirds on the Atlantic Flyway. At least 11 of these species feed on Horseshoe Crab eggs to replenish their fat supply during their long migrations. This critical link in the food chain isn’t the only symbiotic relationship in which the Horseshoe Crab is involved; its eggs provide food for numerous species of fish and sea turtles. In addition, their bodies are hosts to other organisms such as sponges, leeches, molluscs, and snails. Underscoring the natural benevolence of the Horseshoe Crab, several species of crustaceans crawl into the crevices of its frequent moults and use them as sanctuaries.

The Big Picture

Maureen is a role model for learning through direct experience and for being proactive. When she moved to Cape Cod 11 years ago, she knew no one in the community in which she settled. She decided therefore that one way to make new friends was to join the Museum of Natural History as a volunteer docent. The museum became a critical venue for obtaining and sharing information and for making friends. As a community-based organization the museum is also typical of the culture of Cape Cod off the beaten path, a quiet, well-organized way of life that emphasizes the common sense integration of human and natural habitats and the preservation of indigenous resources. Maureen is now one of those resources.

Although she doesn’t use the term, it is clear that Maureen knows that the Horseshoe Crab is a litmus test for large-scale ecological awareness and sustainability on the part of human beings. In an email, Maureen mentions a quotation by Chief Seattle (1786-1866) that she says has had a profound effect on her. “Humankind has not woven the web of life. We are but one thread within it. Whatever we do to ourselves we do to the earth. All things are bound together. All things connect. Whatever befalls the earth, befalls the children of the earth.”

She also knows that the Horseshoe Crab is threatened by the destruction of its offshore habitat, shoreline erosion that impinges on its breeding grounds, water pollution, commercial harvesting, and even people on beaches who do not understand what they are looking at when they encounter a Horseshoe Crab.

But Maureen is not discouraged; in fact I sense that she is quite optimistic about the Horseshoe Crab’s fate. She has an intuitive understanding and belief that by spreading the word to a few new friends on a beach in Cape Cod she will advance the cause of this unique species that, in many ways, is very much like her.


Cape Cod has a great deal to offer the naturalist. For more information you can visit the Cape Cod Museum of Natural History online at Also highly recommended are: the Audubon Wellfleet Bay Wildlife Sanctuary (;

the Aquarium in Woods Hole (;

the Monomoy National Wildlife Refuge (;

and the Cape Cod National Seashore (

In terms of beaches, Maureen recommends Sandy Neck with its dunes and 11 kilometres of beach coastline. As for marshes, especially for canoeing or kayaking, she recommends Scorton Creek in Sandwich, Great Marsh in West Barnstable, Grand Island in Ostervilles, Mashpee River, and her favourite, Bells Neck in Herring River.

Where to stay

Cape Cod is renowned of course for its variety of accommodation. We stayed in the lovely town of Chatham ( only a few kilometres away from the Museum and well-located for exploring other wildlife sites on the Cape. The excellent seafood, ambiance, and service of Christian’s ( and The Chatham Squire ( are also not to be missed.

The Once-Abundant Oceans

The lecture was titled “Crisis Beneath the Waves: Why the Oceans are the Planet’s Biggest Ecological Problem,” and the information was discouraging. But, global awareness and day to day living is about facing facts, and looking for solutions. Also, the environmentally-friendly behaviours we adopt in our daily lives also carry over to our travel lives.

Because the oceans play such a large role in the travel industry — where so many of the most popular travel destinations are located — it is incumbent on travel journalists, the industry itself, and the general public to lead the way so that society in general becomes more aware of the realities and continues to strive to integrate environmentally-friendly practices with the ocean environment.

For a primarily land-based species, it is important first for us to understand that not only is 71 per cent of the Earth’s surface water, but 99 per cent of the living space on the planet is water-based. And 90 per cent of all life forms are in the oceans. Genetically, human beings are overwhelmingly a marine-based species. The majority of the oxygen produced by this planet comes from the sea — produced by plankton. And the ocenas have absorbed most of our fossil fuel carbon dioxide, but to its own detriment.

The oceans are great weather and food source machines. The Gulf Stream current for example is a marine mechanism that creates and recreates life in a great recycling pattern in the Atlantic Ocean. When those warm waters meet the cold Arctic sea water, the heavier sea water forces the warmer water down to the depths of the Atlantic and sends it back in a loop to its tropical source. However, with the melting of the polar ice cap and diminishing salinity of the warmer water moving down from the north, there is genuine concern that this recycling current could actually “switch off.” The climatic effect of such an event, especially on Europe, would probably be devastating. The actual effect is unknown and difficult to predict, let alone imagine.

Most of all life forms are found in the oceans. Of the 33 phyla of life forms on the planet, 28 are found in the oceans. And there are many examples of marine species that exemplify that what we once thought the oceans were — boundless, limitless, and teeming with life — is no longer the case. The Atlantic Cod is perhaps the best example. The population of this once plentiful species of fish off the Grand Banks of Newfoundland, Canada dropped 99 per cent in a very short 50 years. The current moratorium on cod in these waters has been especially devastating for the people of this small island province.

In addition, 90 per cent of the other large commercial fish stocks around the world have also disappeared within a period of 50 years. Sharks are on the verge of extinction; some marine biologists give them only 10 years more. Other species such as leatherback turtles are similarly on the edge.

What are the basic changes in the oceans?

The physical properties of the oceans are changing.

(a) The salinity (pH) of the oceans is changing; they are becoming less salty. This is an actual chemical change. Where once we spoke about acid rain, we now are beginning to speak about acid oceans.

(b) The ice cover is disappearing faster than expected.

(c) The structure of currents are changing, affecting weather patterns.

(d) The depths are changing, which also changes the normal habitat structures.

(e) The temperatures are rising because of greenhouse gases — a problem stemming from developed nations.

(f) Coral reefs are home to 25 per cent of all life forms in the oceans and yet these habitats are disappearing quickly. Coral spawn only once a year, in a great “pageant of life.” Being hermaphroditic, the coral release both ova and sperm at the same time, and in a great planetary process that is the stuff of metaphor and imagery, the newly spawned coral must find a new home. With temperatures rising however in coral reef waters, the existing coral structures become covered with algae and the new coral cannot take hold. Eighty per cent of the corals in the Caribbean have died in the last two decades.

Is it game over?

To scientists like James Lovelock and his Gaia Hypothesis, the situation is bleak if not desperate. The Gaia Hypothesis views the planet as one massive organism; totally interconnected systems that function like the human body. What affects one system, affects another.

Most other scientists say we can still slow down the rate of the oceans’ potential “demise,” but we do not have much time. As individuals, governments, and through international organizations and agreements (like the Kyoto Protocol that George W. Bush has declined to sign on to), we need to be able to include in our environmental awareness not just land-based issues, but the much larger ocean-based issues. And then we must react and behave in such a way as to not only reverse the dismantling of the planet’s integrated organic systems, but also protect and feed those systems as we would the organs in our own bodies.

What’s to be done?

As usual, information gathering and attitudinal change are among the first steps that mere mortals can take to make such enormous collective changes. Responsible travel and tourism begins with the asking of questions. And one does not have to be a formally trained environmental scientist to assess if an oceanside destination is working with that environment or against it.

Increasingly travel suppliers are becoming good corporate citizens and incorporating environmental best practices into their operations. As consumers, we only have to look for the small solutions already in place and — as is the case in all meaningful travel — enjoy an engaged, reciprocal, and mutually beneficial relationship with the sea.


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