Horseshoe Crabs - Miracle blood

Horseshoe crabs- Miracle Blood

The classification of the Horseshoe crab is as follows: Phylum Arthropoda, Class Merostomata,  Family Limulidae, Genus Limulus, Species polyphemus . An adult female Limulus will attain lengths of 24 inches.  Most first time encounters can be rather scary, because they also have a very long spiked tail. Contrary to public opinion, the tail is quite harmless and the horseshoe crab should never be picked up this way. This unique creature lives on sandy or muddy bottoms.  Because of its propensity to burrow, it prefers a softer sediment.  It frequents intertidal and sub-tidal regions, rarely going deeper than 75 feet.  The Atlantic Horseshoe crab may be found from the Gulf of Maine all the way to the Gulf of Mexico. They start of life very light in color.  When small, they are a sand color and, as they molt and grow older, they darken.  After the terminal molt, they are a deep brown color.

Image: cccmkc.edu.hk

Most animals have red blood. Our blood is red thanks to the presence of iron (Fe) in our hemoglobin. Hemoglobin transports oxygen, and since oxygen has poor solubility in water, iron is needed to bind those oxygen molecules onto the hemoglobin.

Some animals are different and have blue-colored blood. Some examples of the blue bloods are the octopus and squid, along with the humble Horseshoe Crab.  They all have blue blood, thanks to the presence of copper as oxygen-transporting agent in their blood, and the blue-colored copper-based molecules are called hemocyanin. 

Image: oar.noaa.gov

Limulus has an interesting history as well.  It was once used en masse as a fertilizer.  Tens of thousands were harvested and spread on fields to fertilize for the summer harvests.  It was a cheap source of fertilizer, since the flesh of the Limulus is inedible to humans and they are considered a nuisance species.  Most clam and oyster farmers dislike the presence of Limulus because they can disrupt their beds and, in the summertime, the beaches are clogged with thousands of crabs.  Trawlers also dislike the tons of crabs that take up valuable net space each year.  So, these animals were collected with little regard.  It was not until the 1970’s that scientists found a special use for Limulus.

Scientists have found out that the blue blood of Horseshoe Crabs does miraculous thing: when a crab gets injured and its insides are exposed to invading bacteria, a particular blood cell explodes, sending a mass of blood-clotting granules that instantly block out the invaders. Thi is invaluable for testing the sterility of pharmaceuticals, more about this later. Our blood clots too, thanks to the platelets in our blood. 

Frederick Bang first discovered the awesome quality of the Horseshoe Crab's blood in the 1950s. He realized that the blood could serve as an alarm system to protect products (human cells, DNA) from contamination, as the blood clot as soon as there is any sign of negative bacteria.It was later recognized that the animal's blood cells, mobile cells called amoebocytes, contain granules with a clotting factor known as coagulogen; this is released outside the cell when bacterial endotoxin is encountered. The resulting coagulation is thought to contain bacterial infections in the animal's semi-closed circulatory system. He isolated the clotting agent and called it Limilus amoebocyte lystate (LAL), and a quart of this LAL could cost up to $15,000. A high-profit investment indeed. 

Fishermen would harvest crabs, extract their blood, sell the serum to pharmaceutical companies, and return the crabs to the wild. But not all crabs survive the ordeal--3~15% of the crabs die after being bled. As a result, the population of Horseshoe Crab in some states in the U.S has dropped significantly.It is now illegal to purposely kill Limulus in most coastal states.

Image: pbs.org

The Horseshoe Crab is one of the oldest creatures to ever walked the Earth. It has outlived the dinosaurs, and has had millions of years to perfect its defense system against invincible enemies. We seek to "borrow" their blood for our own interest, so it would be a shame if we fail keep the species alive in the end.It is always fascinating to observe a true living fossil, but these creatures are best left in nature.  If one is fortunate enough to see one at the beach, please keep a few things in mind.  They are 100% harmless.  Never pick them up by the tail, but grasp firmly onto the carapace and hold them.  They will thrash about , ‘close up,” and try for form a ball, but eventually they will relax,  and one can then observe the book gills, chelicerae - and even tell if it’s a boy or girl.  In males, the first pair of appendages, the chelicarae, have a thickened claw, much like boxing gloves.  The females do not have this.  And if, by chance, on a spring time full moon night at an East coast beach, you happen to be walking along the sand, keep your eyes open for one of the most spectacular events you will ever see.

info:
horseshoecrab.org 

http://www.npr.org/blogs/krulwich/2012/05/31/154095868/what-the-vampire-said-to-the-horseshoe-crab-your-blood-is-blue
http://en.wikipedia.org/wiki/Limulus_amebocyte_lysate

http://www.essortment.com/horseshoe-crabs-miracle-blood-41662.html

http://www.austincc.edu/~emeyerth/hemoglob.htm

Limulus - the Horseshoe crab

The Horseshoe Crab

Jonathan Lowrie

Calling a horseshoe crab a crab is a misnomer, since this distinctive arthropod is more closely related to spiders and other arachnids than to crustaceans. The horseshoe crab is truly a living fossil.  Its only living relatives are found in the East Indies, China and Japan.  But its earliest relatives lived in the Devonian seas more than 350 million years ago.  The genus Limulus, to which the modern horseshoe crab belongs dates back to the Triassic period, the same time as the first dinosaurs. .  Because they are so unique, they are cannot be confused with that of any other creature.

The classification of the Horseshoe crab is as follows: Phylum Arthropoda, Class Merostomata,  Family Limulidae, Genus Limulus, Species polyphemus . An adult female Limulus will attain lengths of 24 inches.  Most first time encounters can be rather scary, because they also have a very long spiked tail. Contrary to public opinion, the tail is quite harmless and the horseshoe crab should never be picked up this way. This unique creature lives on sandy or muddy bottoms.  Because of its propensity to burrow, it prefers a softer sediment.  It frequents intertidal and sub-tidal regions, rarely going deeper than 75 feet.  The Atlantic Horseshoe crab may be found from the Gulf of Maine all the way to the Gulf of Mexico. They start of life very light in color.  When small, they are a sand color and, as they molt and grow older, they darken.  After the terminal molt, they are a deep brown color.

The horseshoe crab has six pairs of appendages.  The first pair is called the chelicerae, followed by 5 pairs of legs, the first of those being called pedipalpi.  The pedipalpi also act as modified claspers in male horseshoe crabs.  The last pair has a special adaptation to facilitate digging into the substrate.  The mouth has no appendages of its own, quite different from true crabs. The chewing mill is the opening of the mouth, and is located at the base of the legs. The only other appendages are the 5 pairs of book gills, so named because they are large, and sheet like and resemble the pages of a book.  The eyes of Limulus are two lateral bump like protrusions and are not stalked.  There is also a third median eye, which is located beneath the foremost spine on the horseshoe-shaped prosoma.

The typical diet of Limulus is clams, worms, and other invertebrates which it grinds with the burr-like bases of the walking legs, which surround the mouth. They collect their food via foraging.  These animals are an incredible sanitizer of the sea, as they will forage in the muck and consume both healthy animals and sick and injured animals. 

Limulus are also known for their seasonal migrations and breeding.  During the first full moon and high tide of spring, thousands of horseshoe crabs return to shore to mate.  The females dig small burrows in the sand to deposit the eggs, after which the male will release sperm to fertilize them.  The timing is such that the females dig and deposit eggs, and the males, further out in the water, release sperm as the waves come in to wash it over the deposits. One can find the many eggs masses along the beach in late spring.  The masses are found as clumps of greenish eggs, about 3 mm in diameter.  It takes only a few weeks for them to mature and be washed back out to sea, where the juveniles spend time as a miniature adults living a benthic lifestyle.

Horseshoe crabs travel mostly on the surface of the seafloor, but they can also swim to escape predation or to move around an obstacle.  They do this by swimming upside down; using the large carapace as a wing, they point their long tails in the direction they wish to go, and beat their kegs frantically.  Although not the most efficient means of propulsion, they can get off the surface enough to catch some waves and travel quite a distance down the beach.  Since they live in the tremulous region of the intertidal zone, they must have a means to right themselves when flipped by a wave.  Fortunately, Limulus has such a means - its tail.  The tail is a long dagger-like projection that may be 12 inches long.  It is covered with many smaller protrusions and spikes.  They will use this tail as a cantilever to right themselves when turned over.  Because of its sinister appearance, the tail sometimes has the reputation of being venomous or capable of stinging.  Neither is true - the worst injury once could sustain from a Horseshoe crab is stepping on the tail, an action which would probably not even break the skin.

Limulus has an interesting history as well.  It was once used en masse as a fertilizer.  Tens of thousands were harvested and spread on fields to fertilize for the summer harvests.  It was a cheap source of fertilizer, since the flesh of the Limulus is inedible to humans and they are considered a nuisance species.  Most clam and oyster farmers dislike the presence of Limulus because they can disrupt their beds and, in the summertime, the beaches are clogged with thousands of crabs.  Trawlers also dislike the tons of crabs that take up valuable net space each year.  So, these animals were collected with little regard.  It was not until the 1970’s that scientists found a special use for Limulus.  Their blood.  Because of the unique properties of their blood, they make an excellent biomedical specimen.  In fact, they have a unique immune system. Because of this, their blood reacts very strongly to certain pathogens.  So, each year, small amounts of blood are collected harmlessly from these animals and used to test the purity of many vaccines, antibiotics and other injectible medications.  It is now illegal to purposely kill Limulus in most coastal states.

Limulus can sometimes be found for sale at  local fish stores.  Once one takes into account the reasons they are being sold and then looks at their natural lifestyle, it is apparent that this species is just not suitable for the home aquarium.  Often they are sold as ‘sand sifters’, and they do just that.  As mentioned, Limulus is an excellent burrower and will adeptly crawl though the substrate.  Herein lies the problem - they do this almost constantly.  Unless provided with a huge tank, they will soon be under the live rock formations, and they will easily topple over corals, and rock.  There are also dietary problems.  We keep live sand, trying to keep the bacteria, and infauna heavily populated.  By confining a creature that constantly sifts through sand for food, eating molluscs, worms, and such, it can easily wipe out a live sand bed of its beneficial populations.  In nature, they feed over many square feet, rarely returning to an area for many days.  But, in a 75 gallon tank, the small area will force Limulus to completely clean the sand bed of food.  Sadly, many times Limulus will slowly starve to death because it cannot forage enough food from an aquarium.  And since they are always offered as beige young animals, few people will ever realize they will reach 24 inches in length.

If one is already purchased, or if the resources for the proper habitat can be provided, the next obstacle is temperature.  Any organism that is found from the Gulf of Maine to the Gulf of Mexico can tolerate a wide range of temperatures.  Interestingly, the horseshoe crab cannot easily adjust to these large changes.  There are many separate and distinct populations of Limulus along the Eastern coast, so its critical to know the origin of the horseshoe crab and to what temeperature range it is best suited.  In the Gulf of Mexico, they can easily withstand 76 to 80 degrees.  Yet, the Limulus off the Carolina coast have a tolerance for the mid 70’s only, while those from further north require 60 degrees or cooler waters to survive. Because of their habits, movement, and propensity for growth, Limulus is simply not a species that should be kept in an aquarium. 

It is always fascinating to observe a true living fossil, but these creatures are best left in nature.  If one is fortunate enough to see one at the beach, please keep a few things in mind.  They are 100% harmless.  Never pick them up by the tail, but grasp firmly onto the carapace and hold them.  They will thrash about , ‘close up,” and try for form a ball, but eventually they will relax,  and one can then observe the book gills, chelicerae - and even tell if it’s a boy or girl.  In males, the first pair of appendages, the chelicarae, have a thickened claw, much like boxing gloves.  The females do not have this.  And if, by chance, on a spring time full moon night at an East coast beach, you happen to be walking along the sand, keep your eyes open for one of the most spectacular events you will ever see.

Live Sand: In depth discussion

Live Sand

by

Jonathan Lowrie

Some definitions to begin with:

Infauna	Animals that live within sediments on seafloor bottom.
Epifauna	Benthic animals that crawl along the bottom or are firmly attached to bottom structures.
Macrofauna	Macroscopic animals that live on or in sediment.
Microfauna	Those animals less than 50 microns that live within the sediments.
Meiofauna	The animals between sizes.  Also between spaces- these animals live within the interstitial spaces of the sediments.
Closed System	System which has no connection with outside environment.  A typical home aquaria.
Open System	A system with a direct interchange with the outside environment.
NNR	Natural Nitrate Reduction. A concept of 'natural' filtration using a plenum and live san layers.
Plenum	A space or cavity. In the case of san beds, a raised space off the bottom of the aquarium with a barrier covered with a thickness of sand.
'Natural'	A process that occurs in captivity in much the same fashion as in nature.
Ecosystem	All the organisms in a biotic community and the abiotic environmental factors they interact with.
Live Sand	Simply put: sand with living organisms contained within the interstitial spaces, or on the sand grains.

Sand at Wikipedia

SeaFloor Characteristics

• Seafloor characteristics are a crucial part of the habitat of benthic organisms.  As the substrate supports the weight of many animals considerably more dense than seawater.

•  The seafloor also acts as a mechanical barrier to collect and accumulate plankton, waste material, and detritus.  A variety of worms, echinoderms, mollusks, and crustaceans obtain their nourishment from this organic matter.

• Benthic organisms are adapted for a particular bottom type; and character of life there, to a large extent, is dependent on the properties of bottom substrate.

• This bottom material varies from very solid rock to very soft, loose deposits.

• The actual composition of the seafloor is determined principally by the amount of energy available.  In nature this is through wind driven waves primarily.

 • In an aquarium, it can be from the use of auxiliary pumps.

• Benthic animals play an important role in mixing and sorting of sediments by their burrowing and sorting of the sediments by their burrowing and feeding activities.

•  Oxygen and water from the sediment surface are transported down into the sediment through these tubes and burrows.

• Further modification of sedimentary characteristics is accomplished via cementing particles together to form tubes, and by compacting sediments together as fecal pellets and castings.

• The distributional patterns of benthic animals and plants are strongly influenced by the form and texture of their substrate. 

• These factors determine effectiveness of locomotion, or for non-motile species, the persistence of attachment to bottom.

Animal Substrate Interaction

Because of the different distributions, unique adaptations have developed allowing for specialization to those environments. 

• The particle size and organic content of the bottom material limits the versatility; and thus the distribution of specialized feeding habits.

Before you say ‘huh?', allow me to explain in terms of our captive closed systems.  All the diverse habitat types in nature all support a selective array of animal life. 

• What exists in one biotope, most probably will not exist in another.  In our aquariums, this translates well into the discussion of live rock and live sand. 

• Live rock is a solid substrate.  It has a variety of live within and about it.  From small sponges, tunicates, to corals. 

• Within may be algaes, bacteria, and more.  All of these animals and plants have adapted to life on a hard substrate such as the live rock.  Sand on the other hand is a totally different environment

• It is much softer, and will not offer the same advantages to most of the animals.  Yes, some will be able to make the transition, and tolerate the new habitat, but many will not migrate to the new habitat.  Hence the reason why adding live rock to ‘dead’ sand will not ultimately lead to a ‘live’sand bed.

 Before the critics jump up and yell, let me explain my opinion of ‘live’.  Yes, the sand will have life in it.

But will it have the typical life found within that format of sediment?  No.

 It has to come from somewhere, and sand animals and plants as a rule don’t live on rock, and vice versa.

• Suspension feeders depend on small plankton or detritus for nutrition.  Filtering devices or sticky mucous nets are employed to collect minute suspended food from the water. Suspension feeders generally require clean water to prevent accumulation of indigestible particles.

• Deposit feeders engulf masses of sediments and process them through their digestive tract.  They extract nourishment through their digestive tract from the organic matter of the sediment in much the same manner as an earthworm.

If we are to keep obligate suspension feeders, or deposit feeders in our aquariums, we must be sure to provide them the proper and suitable habitat to thrive in.

Sediment Types and Sorting

Many reef sediments are terrigenous in origin (in Atlantic reefs).  Terrigenous sediments are those originating from terrestrial origins, and entering the ocean through streams and rivers.

 The Atlantic Ocean has more large volume rivers that dump literally millions of cubic feet per hour of terrigenous sediments into the oceans.  Much of this falls along the Continental shelf, but some does reach the reef zones.

 In the Pacific Ocean, there are fewer rivers with huge outflows, as well as deep trenches to collect and accumulate this sediment.

Another sediment type of reefs is biogenic sediment.  Biogenic sediment is derived from living animal and plants.  These are sediments formed from diatoms skeletons, and skeletons of other animals and plants that have passed through the water column.

Biogenic sediments usually contain a high level of Calcium Carbonate.

Now, again, how does all this relate to the home aquarium?  Coarse sediments are very difficult for animals to inhabit. 

• The sand grains are cutting, and have a considerable mass that can easily crush the soft bodied animals.  Most life here tends to be tube burrowing worms, and mollusks.

 • Many are considered meiofauna as they exist in between sediment partakes as to prevent this destruction from abrasion.

• Finer sediments from sandy silt to mud typically have a rich fauna.  Thousands of species can be found in healthy sheltered mud flats and grass beds.

• These natural sediment beds have another role as well.  That role is as a mineral source.  In nature, marine sediments will sometimes release minerals that will precipitate to form irregular deposits on the seafloor.

• Coral skeletons, and Halimeda is composed of calcium carbonate is composed of calcium carbonate in the form of aragonite.  While many of the red algaes, and forams have CaCO3 in the form of calcite. 

• Calcium carbonate can exist in three forms- two of which are important to reef systems.  Those are calcite and aragonite.

In the Aquarium

So now I am back to the nature of the sand bed of the home aquarium.  Typically, folks dump in a uniform size gravel of aragonite based sand.

Problems:

 • Inadequate habitat

 Using a fine sand and a medium sand and a coarse sand you can replicate the diversity of sediments to a limited extent.

Layers:

• Good, Bad, or indifferent

Depth:

• Deep?

• Shallow?

• Slopped?

A Mixed Sediment Filtration System:

  Another more complex method is to have a mixed sediment system.  This is involves using a sump and or refugium as well.  Rather than go into great detail and stir up controversies, I will say this:  Refugia with seagrasses and mangroves serve many useful purposes.

 As a habitat for small shrimp, fish, mollusks, etc.  And as a means to filter the aquarium.  When I say filter- I also include mechanical and biological filtration.

 Seagrasses in nature act as a baffle for sediment suspended in water, and will draw these sediments down to their bases.  In a properly flowing system the seagrasses can serve much the same purpose at home.

NNR

Wait!  Someone is bound to ask why?  Why do we want to increase diversity if our current NNR or other systems seem to work?

A few comments:

• Live sand will not form from dead sand.

 Period.

 Louis Pasteur proved the world wrong on spontaneous generation, and it won't happen in your reef tank.  No matter how good the live rock is, it won't provide what is necessary for a healthy sand bed.

Does NNR work?

• In many cases yes.

Is it the best system for me?

• Most often, no.

         • Degrades over time

         • Does not allow for diversification

         • Artificial means to accomplish a natural function

 On shipping live sand. 

Sand is rough  Its cuts, it grinds.  And have you ever lifted 50 pounds of it?! Imagine being a soft bodied annelid or a think shelled mollusk.  And being grated, smashed, and smooshed by the sand.

• Collection

• wait

• Box

• Tranship- in airplane

• Wholesalers- stored

• Fedex to you or stored

• Retail channels

Ways to Improve your Sand Bed:

• Add more benthic animals

Some sources may include Inland Aquatics Detrivore kits

         Indo Pacific Sea Farms shrimp cultures

         Brittle stars, Holothurians, worms, etc.

• Increase particle type diversity

                  Add more sand sizes

                  Add deeper sediment layers

• Add sifters

                  Gobies, other fish, etc.

• Feed and skimming

                  In established reef, can consider skimmerless operation

Heavy feeding of phytoplankton and zooplankton

                  Will help establish microfaunal population

• Depth

                  At least 6 to 8 inches. More if you can fit it.

                  Can be hidden with bottom.

Wentworth Geometric Scale
The phi scale is based on the logarithmic transformation of a particle diameter (phi = logbase2 particle size in mm)
	Particle Type	Size (mm)	Phi units
Gravel	Boulder	>256	beyond -8.0
	Cobble	256-64	-8.0 to -6.0
	Pebble	64-4	-6.0 to -2.0
	Fine Gravel	4-2	-2.0 to -1.0
Sand	Very coarse sand	2-1	-1.0 to 0
	Coarse sand	1-0.5	0 to 1.0
	Medium Sand	0.5 - 0.2	1.0 to 2.0
	Fine Sand	0.25 - 0.125	2.0 to 3.0
	very fine sand	0.125 - 0.063	3.0 to 4.0
Silt	coarse silt	0.063 - 0.020	4.0 to 5.0
	medium silt	0.020 -0.005	5.0 to 7.0
	fine silt	0.004 -0.002	7.0 to 8.0
Clay	clay	<0.004	beyond 8

Composition of Reef Sand Communities (Scoffin, et. al.,1985)
depth	region	composition
165 m	reef shelf edge slope	soft compacted sediment, medium to fine sand
98 m	shelf edge	medium to coarse compacted  sediments
71 m	outer shelf	coarse loose sediments, mainly Halimeda
63 m	inter-reef location 1	mixed sediment sizes
69 m	inter-reef location 2	soft loose fine sand
46 m	leeward reef talus	well worn coarse sediments
40 m	lagoon, near reef	coarse unsorted sand lagoon, away from reef medium to fine sediments with much macrolife