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  • This is a juvenile of an endangered tri-spine horseshoe crab (Tachypleus tridentatus), juxtaposed with a five Yen coin for scale. The animal’s carapace measured about 37mm, which suggests that this juvenile was at the fifth instar of development, about a year since hatching. This species takes 15 years to mature, molting 18 times during that period. The estimated lifespan for this species is 25 years.<br />
<br />
These horseshoe crabs are generally only active when the water temperature exceeds 18 degrees Celsius. As such, they are dormant for much of the year, resting in deeper water until the ocean warms again.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.<br />
<br />
Synthetic substitute tests have been available since 2003. The biomedical industry has however been reluctant to discontinue the practice of bleeding live animals.
    tachypleus-tridentatus-juvenile-tri-...tif
  • This is a pair of tri-spine horseshoe crabs (Tachypleus tridentatus) walking across the ocean bottom in shallow water just prior to spawning. The smaller male uses modified legs (pedipalps) to grasp onto the female in front. The female has just started to burrow into the substrate, a process which involves digging deep enough to bury the front part of her body (Prosoma) and much of her abdominal area (Opisthosoma) as well. When she eventually reaches acceptable depth and deposits eggs, the male will fertilize them. Females often deposit several clutches of eggs in the same general area before moving on to do the same in different locations.<br />
<br />
Note the gastropod riding on the female’s head. Shells, barnacles and other similar passengers seem relatively common on these horseshoe crabs.<br />
<br />
Although these animals are called crabs, they are not members of the Subphylum Crustacea. They belong to a separate Subphylum—Chelicerata—which also comprises sea spiders, arachnids, and several extinct lineages such as sea scorpions. The earliest known fossils of horseshoe crabs date back 450 million years ago, qualifying these animals as living fossils, as they have remained largely unchanged.<br />
<br />
Tachypleus tridentatus is the largest of the four living species of these marine arthropods, all of which are endangered.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a pair of tri-spine horseshoe crabs (Tachypleus tridentatus) walking across the ocean bottom in shallow water just prior to spawning. The smaller male uses modified legs (pedipalps) to grasp onto the female in front. The male stays attached in this manner throughout the reproductive season, going wherever the female goes.<br />
<br />
Although these animals are called crabs, they are not members of the Subphylum Crustacea. They belong to a separate Subphylum—Chelicerata—which also comprises sea spiders, arachnids, and several extinct lineages such as sea scorpions. The earliest known fossils of horseshoe crabs date back 450 million years ago, qualifying these animals as living fossils, as they have remained largely unchanged.<br />
<br />
Tachypleus tridentatus is the largest of the four living species of these marine arthropods, all of which are endangered.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.<br />
<br />
Synthetic substitute tests have been available since 2003. The biomedical industry has however been reluctant to discontinue the practice of bleeding live animals.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a newly hatched endangered Japanese horseshoe crab (Tachypleus tridentatus), around 7mm in size. Juveniles emerge fully formed and functional.
    tachypleus-tridentatus-horseshoe-cra...tif
  • These are endangered tri-spine horseshoe crabs (Tachypleus tridentatus) engaged in spawning. The larger female in front has just started to burrow into the substrate to deposit eggs, with the smaller male attached to the rear.<br />
<br />
In the intertidal location where this pair were photographed, the mud and gravel substrate contained pockets of air, which were sometimes released when the horseshoe crabs became active. Such liberated gas sometimes passes through the carapace of the female, resulting in the illusion of exhalation. Here it appears almost as if the female crab is venting air.<br />
<br />
Although these animals are called crabs, they are not members of the Subphylum Crustacea. They belong to a separate Subphylum—Chelicerata—which also comprises sea spiders, arachnids, and several extinct lineages such as sea scorpions. The earliest known fossils of horseshoe crabs date back 450 million years ago, qualifying these animals as living fossils, as they have remained largely unchanged.<br />
<br />
Tachypleus tridentatus is the largest of the four living species of these marine arthropods, all of which are endangered.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.<br />
<br />
Synthetic substitute tests have been available since 2003. The biomedical industry has however been reluctant to discontinue the practice of bleeding live animals.
    tachypleus-tridentatus-horseshoe-cra...tif
  • Pictured here are developing embryos of endangered Japanese horseshoe crabs (Tachypleus tridentatus), about 5mm in diameter. The membranes of some eggs have started to dissolve, indicating that they are on the cusp of hatching, approximately two months after the eggs were deposited.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a pair of endangered tri-spine horseshoe crabs (Tachypleus tridentatus) moving across the ocean bottom, with the larger female in front and the male clasped onto the rear. The tips of some of the animals’ legs are visible.<br />
<br />
The female is searching for a location to spawn. Once she finds a place that she likes, she burrows partially into the substrate and deposits a clutch of eggs, which the male fertilizes. Such spawning occurs repetitively. When searching in this manner, horseshoe crabs can travel at a relatively rapid pace. Otherwise, they tend to move slowly, as evidenced by the gastropod that has crawled on top of the male’s head.<br />
<br />
Although these animals are called crabs, they are not members of the Subphylum Crustacea. They belong to a separate Subphylum—Chelicerata—which also comprises sea spiders, arachnids, and several extinct lineages such as sea scorpions. The earliest known fossils of horseshoe crabs date back 450 million years ago, qualifying these animals as living fossils, as they have remained largely unchanged.<br />
<br />
Tachypleus tridentatus is the largest of the four living species of these marine arthropods, all of which are endangered.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a pair of endangered tri-spine horseshoe crabs (Tachypleus tridentatus) engaged in spawning. They are walking along the ocean bottom in shallow water, with the larger female in front searching for a place to deposit eggs, which will be fertilized by the smaller male attached to the rear.<br />
<br />
The tips of the horseshoe crabs’ legs are visible in this image. These animals have five pairs of legs used for locomotion—the pedipalps first, followed by three pairs of legs in the middle, and a pair of pusher legs at the end. The male’s pedipalps are modified into a pair of claspers used to grasp the female as seen here. <br />
<br />
Although these animals are called crabs, they are not members of the Subphylum Crustacea. They belong to a separate Subphylum—Chelicerata—which also comprises sea spiders, arachnids, and several extinct lineages such as sea scorpions. The earliest known fossils of horseshoe crabs date back 450 million years ago, qualifying these animals as living fossils, as they have remained largely unchanged.<br />
<br />
Tachypleus tridentatus is the largest of the four living species of these marine arthropods, all of which are endangered.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a newly hatched endangered Japanese horseshoe crab (Tachypleus tridentatus), around 7mm in size. Juveniles emerge fully formed and functional. The animal's feet are visible protruding from the rear of the carapace.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a close-up view of a male tri-spine horseshoe crab (Tachypleus tridentatus) that is in the process of fertilizing eggs being deposited by the female in the substrate beneath the male. The female has burrowed into the mud and gravel, with her head and most of her torso buried.<br />
<br />
Although these animals are called crabs, they are not members of the Subphylum Crustacea. They belong to a separate Subphylum—Chelicerata—which also comprises sea spiders, arachnids, and several extinct lineages such as sea scorpions. The earliest known fossils of horseshoe crabs date back 450 million years ago, qualifying these animals as living fossils, as they have remained largely unchanged.<br />
<br />
Tachypleus tridentatus is the largest of the four living species of these marine arthropods, all of which are endangered.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.<br />
<br />
Synthetic substitute tests have been available since 2003. The biomedical industry has however been reluctant to discontinue the practice of bleeding live animals.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a juvenile Japanese horseshoe crab (Tachypleus tridentatus) climbing up and out of the substrate where it had just hatched with dozens of siblings. When spawning takes place, eggs are deposited, fertilized and buried. Upon hatching, the young horseshoe crabs need to burrow up through 10-20cm of sand, mud and muck.
    tachypleus-tridentatus-horseshoe-cra...tif
  • Pictured here are developing embryos of endangered Japanese horseshoe crabs (Tachypleus tridentatus). These eggs are on the cusp of hatching, approximately two months after they were deposited. The embryos are mobile inside the eggs, moving their legs and turning in circles. By this stage, the eggs are about 5mm in diameter.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a juvenile of an endangered tri-spine horseshoe crab (Tachypleus tridentatus). It measured about 37mm, which suggests that this juvenile was at the fifth instar of development, about a year since hatching. This species takes 15 years to mature, molting 18 times during that period. The estimated lifespan for this species is 25 years.<br />
<br />
These horseshoe crabs are generally only active when the water temperature exceeds 18 degrees Celsius. As such, they are dormant for much of the year, resting in deeper water until the ocean warms again.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.<br />
<br />
Synthetic substitute tests have been available since 2003. The biomedical industry has however been reluctant to discontinue the practice of bleeding live animals.
    tachypleus-tridentatus-juvenile-tri-...tif
  • This scene depicts the birth of juvenile endangered Japanese horseshoe crabs (Tachypleus tridentatus). During spawning, an adult female deposits clusters of dozens of eggs, which are fertilized by a male that is attached to the female during the spawning season. The gestation period is approximately two months. Juveniles emerge at the same time, sometimes one by one, sometimes in groups like this.
    tachypleus-tridentatus-horseshoe-cra...tif
  • These are endangered tri-spine horseshoe crabs (Tachypleus tridentatus) moving across the ocean floor together prior to engaging in spawning. The larger female is in front, the smaller male attached to the rear. <br />
<br />
During spring high tide, pairs like this move to shallow water. They remain largely motionless, though they do move from time to time as depicted here. When the time comes for spawning, the female digs into the substrate and deposits a clutch of eggs, which the male fertilizes. Spawning occurs repetitively.<br />
<br />
Although these animals are called crabs, they are not members of the Subphylum Crustacea. They belong to a separate Subphylum—Chelicerata—which also comprises sea spiders, arachnids, and several extinct lineages such as sea scorpions. The earliest known fossils of horseshoe crabs date back 450 million years ago, qualifying these animals as living fossils, as they have remained largely unchanged.<br />
<br />
Tachypleus tridentatus is the largest of the four living species of these marine arthropods, all of which are endangered.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.<br />
<br />
Synthetic substitute tests have been available since 2003. The biomedical industry has however been reluctant to discontinue the practice of bleeding live animals.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a newly hatched Japanese horseshoe crab (Tachypleus tridentatus). It had just crawled out of the substrate and swum into the murky, nutrient-rich water column, which was filled with a frenzy of copepods.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a pair of tri-spine horseshoe crabs (Tachypleus tridentatus) walking across the ocean bottom in shallow water just prior to spawning. The smaller male uses modified legs (pedipalps) to grasp onto the female in front. The female has just started to burrow into the substrate, a process which involves digging deep enough to bury the front part of her body (Prosoma) and much of her abdominal area (Opisthosoma) as well. When she eventually reaches acceptable depth and deposits eggs, the male will fertilize them. Females often deposit several clutches of eggs in the same general area before moving on to do the same in different locations.<br />
<br />
In the shallow intertidal area where this photograph was taken, pockets of air were trapped in the gravel and mud. Digging by female horseshoe crabs sometimes releases some of the air, as seen in this image. Note also the gastropod riding on the female’s head. Shells, barnacles and other passengers seem to be relatively common on these horseshoe crabs.<br />
<br />
Although these animals are called crabs, they are not members of the Subphylum Crustacea. They belong to a separate Subphylum—Chelicerata—which also comprises sea spiders, arachnids, and several extinct lineages such as sea scorpions. The earliest known fossils of horseshoe crabs date back 450 million years ago, qualifying these animals as living fossils, as they have remained largely unchanged.<br />
<br />
Tachypleus tridentatus is the largest of the four living species of these marine arthropods, all of which are endangered.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a pair of endangered Japanese horseshoe crab (Tachypleus tridentatus) juveniles. One has commenced borrowing into the substrate. The other had flipped upside-down, as the juveniles seem to do with reasonable frequency.
    tachypleus-tridentatus-horseshoe-cra...tif
  • The birth of endangered Japanese horseshoe crabs (Tachypleus tridentatus) can be a chaotic process. The juveniles are small, in the range of 5mm to 7mm. They are not agile or adept swimmers. As they crawl out of the muck, many are pushed, pulled and spun by waves and currents. Some get entangled among themselves. And on occasion, bubbles of air released from the substrate knock them flat on their backs.
    tachypleus-tridentatus-horseshoe-cra...tif
  • These are endangered tri-spine horseshoe crabs (Tachypleus tridentatus) engaged in spawning. The larger female is in front, the smaller male attached to the rear. <br />
<br />
During spring high tide, pairs like this move to shallow water. They remain largely motionless. When the time comes for spawning, the female digs into the substrate and deposits a clutch of eggs, which the male fertilizes. Spawning occurs repetitively.<br />
<br />
In the intertidal location where this pair were photographed, the mud and gravel substrate contained pockets of air, which were sometimes released when the horseshoe crabs became active. The escaped gas bubbled up and emerged from the muck, sometimes passing through the carapace of the female, resulting in the illusion of exhalation, as pictured here.<br />
<br />
Although these animals are called crabs, they are not members of the Subphylum Crustacea. They belong to a separate Subphylum—Chelicerata—which also comprises sea spiders, arachnids, and several extinct lineages such as sea scorpions. The earliest known fossils of horseshoe crabs date back 450 million years ago, qualifying these animals as living fossils, as they have remained largely unchanged.<br />
<br />
Tachypleus tridentatus is the largest of the four living species of these marine arthropods, all of which are endangered.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.
    tachypleus-tridentatus-horseshoe-cra...tif
  • These are two newly hatched endangered juvenile Japanese horseshoe crab (Tachypleus tridentatus) juveniles emerging from the ocean bottom.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a newly hatched endangered Japanese horseshoe crab (Tachypleus tridentatus), around 7mm in size. Juveniles emerge fully formed and functional.
    tachypleus-tridentatus-horseshoe-cra...tif
  • The birth of endangered Japanese horseshoe crabs (Tachypleus tridentatus) can be a chaotic process. The juveniles are small, in the range of 5mm to 7mm. They are not agile or adept swimmers. As they crawl out of the muck, many are pushed, pulled and spun by waves and currents. Some get entangled among themselves.
    tachypleus-tridentatus-horseshoe-cra...tif
  • There are eggs of endangered Japanese horseshoe crabs (Tachypleus tridentatus), between 2mm and 3mm in diameter. The eggs are were deposited in shallow gravel and mud about a month prior to this photograph. As the eggs develop, they grow to around 5mm in diameter and the membranes become transparent, revealing the developing embryos inside.
    tachypleus-tridentatus-horseshoe-cra...tif
  • These are endangered Japanese horseshoe crab (Tachypleus tridentatus) juveniles clustering together.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This scene depicts the birth of juvenile endangered Japanese horseshoe crabs (Tachypleus tridentatus). During spawning, an adult female deposits clusters of dozens of eggs, which are fertilized by a male that is attached to the female during the spawning season. The gestation period is approximately two months. Juveniles emerge at the same time, sometimes individually, sometimes in groups.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a juvenile endangered Japanese horseshoe crab (Tachypleus tridentatus) setting forth into the world. Measuring about 7mm, this little crustacean and siblings burst forth from their nest in a frenzy of activity approximately two months after spawning by the adults.
    tachypleus-tridentatus-horseshoe-cra...tif
  • Pictured here are developing embryos of endangered Japanese horseshoe crabs (Tachypleus tridentatus), about 5mm in diameter. The membranes of some eggs have started to dissolve, indicating that they are on the cusp of hatching, approximately two months after the eggs were deposited.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a juvenile of an endangered tri-spine horseshoe crab (Tachypleus tridentatus). It measured about 37mm, which suggests that this juvenile was at the fifth instar of development, about a year since hatching. This species takes 15 years to mature, molting 18 times during that period. The estimated lifespan for this species is 25 years.<br />
<br />
These horseshoe crabs are generally only active when the water temperature exceeds 18 degrees Celsius. As such, they are dormant for much of the year, resting in deeper water until the ocean warms again.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.<br />
<br />
Synthetic substitute tests have been available since 2003. The biomedical industry has however been reluctant to discontinue the practice of bleeding live animals.
    tachypleus-tridentatus-juvenile-tri-...tif
  • This is a pair of endangered tri-spine horseshoe crabs (Tachypleus tridentatus) preparing to spawn. The larger female in front has chosen a place to deposit eggs. She has just commenced digging. The bubbles are the result of pockets of air trapped in the mud and gravel being released due to the female’s excavation. Spawning takes place in the intertidal zone, which is the reason that air is present in the sediment. The smaller male is firmly affixed to the female’s opisthosoma. He will fertilize the eggs she deposits, and then the pair will move on to find another location to spawn again.<br />
<br />
Although these animals are called crabs, they are not members of the Subphylum Crustacea. They belong to a separate Subphylum—Chelicerata—which also comprises sea spiders, arachnids, and several extinct lineages such as sea scorpions. The earliest known fossils of horseshoe crabs date back 450 million years ago, qualifying these animals as living fossils, as they have remained largely unchanged.<br />
<br />
Tachypleus tridentatus is the largest of the four living species of these marine arthropods, all of which are endangered.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.<br />
<br />
Synthetic substitute tests have been available since 2003. The biomedical industry has however been reluctant to discontinue the practice of bleeding live animals.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a top-down view of a pair of endangered tri-spine horseshoe crabs (Tachypleus tridentatus) engaged in spawning. The male is clasped onto the rear of the female, preparing to fertilize eggs that she will deposit. Seen here, the female is still burrowing into the substrate. She will dig deeper, until her primary compound eyes and most of her prosoma is buried. The bubbles are the result of pockets of air trapped in the mud and gravel being released due to the female’s excavation.<br />
<br />
Spawning takes place in the intertidal zone, which is the reason that substantial quantities of air are present in the sediment. It is also the reason that the water is murky and somewhat hazy, as there is mixing of fresh water flowing in from land.<br />
<br />
Although these animals are called crabs, they are not members of the Subphylum Crustacea. They belong to a separate Subphylum—Chelicerata—which also comprises sea spiders, arachnids, and several extinct lineages such as sea scorpions. The earliest known fossils of horseshoe crabs date back 450 million years ago, qualifying these animals as living fossils, as they have remained largely unchanged.<br />
<br />
Tachypleus tridentatus is the largest of the four living species of these marine arthropods, all of which are endangered.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a pair of endangered tri-spine horseshoe crabs (Tachypleus tridentatus) engaged in spawning. The male is clearly visible, clasped onto the rear of the female. He is fertilizing eggs being deposited by the female, whose head is buried in the substrate.<br />
<br />
Although these animals are called crabs, they are not members of the Subphylum Crustacea. They belong to a separate Subphylum—Chelicerata—which also comprises sea spiders, arachnids, and several extinct lineages such as sea scorpions. The earliest known fossils of horseshoe crabs date back 450 million years ago, qualifying these animals as living fossils, as they have remained largely unchanged.<br />
<br />
Tachypleus tridentatus is the largest of the four living species of these marine arthropods, all of which are endangered.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.<br />
<br />
Synthetic substitute tests have been available since 2003. The biomedical industry has however been reluctant to discontinue the practice of bleeding live animals.
    tachypleus-tridentatus-horseshoe-cra...tif
  • These are endangered tri-spine horseshoe crabs (Tachypleus tridentatus) engaged in spawning. The male is visible in his entirety, attached to the rear of the female. The female (much larger than the male) has burrowed into the substrate, with her head and most of her torso buried. She is in the process of depositing eggs, with the male fertilizing them.<br />
<br />
In the intertidal location where this pair were photographed, the mud and gravel substrate contained pockets of air. Digging and other activity by the female releases the trapped air, which bubbles up as seen in this image.<br />
<br />
Although these animals are called crabs, they are not members of the Subphylum Crustacea. They belong to a separate Subphylum—Chelicerata—which also comprises sea spiders, arachnids, and several extinct lineages such as sea scorpions. The earliest known fossils of horseshoe crabs date back 450 million years ago, qualifying these animals as living fossils, as they have remained largely unchanged.<br />
<br />
Tachypleus tridentatus is the largest of the four living species of these marine arthropods, all of which are endangered.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.<br />
<br />
Synthetic substitute tests have been available since 2003. The biomedical industry has however been reluctant to discontinue the practice of bleeding live animals.
    tachypleus-tridentatus-horseshoe-cra...tif
  • These are developing embryos of endangered Japanese horseshoe crabs (Tachypleus tridentatus), 3mm to 4mm in size. Eggs molt during the development, as can be seen here. The stage of development is perhaps four to six weeks after spawning took place.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a juvenile endangered Japanese horseshoe crab (Tachypleus tridentatus) swimming into the water column after birth. Measuring about 7mm, this little crustacean and siblings burst forth from their nest in a frenzy of activity approximately two months after spawning by the adults.
    tachypleus-tridentatus-horseshoe-cra...tif
  • Horseshoe crabs (Tachypleus tridentatus) generally move in a measured, relatively slow manner, when they move at all. When females emerge after spawning however, they occasionally do so with surprising speed and force, as seen here. The female in the foreground has lifted herself out of the gravel and mud in one rapid motion, creating this momentary effervescence from the release of small pockets of air that had been trapped in the substrate.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a pair of endangered Japanese horseshoe crab (Tachypleus tridentatus) juveniles. Juveniles like this sometimes climb on top of and grapple with one another when they encounter each other.
    tachypleus-tridentatus-horseshoe-cra...tif
  • Pictured here are developing embryos of endangered Japanese horseshoe crabs (Tachypleus tridentatus). These eggs are on the cusp of hatching, approximately two months after they were deposited. The embryos are mobile inside the eggs, paddling with their legs and turning in circles. By this stage, the eggs are about 5mm in diameter.
    tachypleus-tridentatus-horseshoe-cra...tif
  • This is a pair of endangered tri-spine horseshoe crabs (Tachypleus tridentatus) preparing to spawn. The larger female in front has chosen a place to deposit eggs. She has just commenced digging. The bubbles streaming up from between her prosoma and opisthosoma are the result of pockets of air trapped in the mud and gravel being released due to the female’s excavation. Spawning takes place in the intertidal zone, which is the reason that air is present in the sediment. The smaller male is firmly affixed to the female’s opisthosoma. He will fertilize the eggs she deposits, and then the pair will move on to find another location to spawn again.<br />
<br />
Although these animals are called crabs, they are not members of the Subphylum Crustacea. They belong to a separate Subphylum—Chelicerata—which also comprises sea spiders, arachnids, and several extinct lineages such as sea scorpions. The earliest known fossils of horseshoe crabs date back 450 million years ago, qualifying these animals as living fossils, as they have remained largely unchanged.<br />
<br />
Tachypleus tridentatus is the largest of the four living species of these marine arthropods, all of which are endangered.<br />
<br />
Though habitat loss and overharvesting of these animals for food are primary contributors to the population decline of horseshoe crabs, the biomedical industry is also a major factor. Horseshoe crabs are bled for their amoebocytes (akin to white blood cells), which are used to derive an extract that reacts in the presence endotoxin lipopolysaccharide, which is found in the membranes of gram-negative bacteria. Estimates suggest that between three and 30% of the animals die as a result. There have also been suggestions that taking up to a third of each animal's blood adversely affects their ability to undertake vital functions, such as procreation, even if the animals survive.
    tachypleus-tridentatus-horseshoe-cra...tif
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