Very im­por­tant arthro­pod

The horse­shoe crab has out­lived di­nosaurs but it is no match for medicine’s hunger for its blood

The Guardian Weekly - - Global report - By Jonathan Watts

Few peo­ple are aware their well­be­ing may one day de­pend on a blue-blooded crab that looks like a cross be­tween the face­hug­ger from Alien and a gi­gan­tic louse. Fewer still re­alise this crea­ture now faces its great­est threat in more than 450m years.

The Amer­i­can horse­shoe crab out­lived the di­nosaurs and has sur­vived four pre­vi­ous mass ex­tinc­tions, but is now men­aced by the phar­ma­ceu­ti­cal in­dus­try, fish­ing com­mu­ni­ties, habi­tat loss, cli­mate change and, most re­cently, chok­ing tides of red al­gae off the east coast of the United States.

Abun­dant three decades ago, this liv­ing fos­sil was put on the vul­ner­a­ble list by the In­ter­na­tional Union for the Con­ser­va­tion of Na­ture in 2016. Sci­en­tists say the crab’s de­cline sym­bol­ises the huge eco­nomic and health costs of bio­di­ver­sity loss world­wide.

The cop­per-based blood of the horse­shoe crab con­tains the most sen­si­tive in­di­ca­tor of bac­te­ria ever dis­cov­ered, limu­lus amoe­bo­cyte lysate. The lysate is vi­tal to iden­tify con­tam­i­nants in med­i­cal equip­ment ahead of sur­gi­cal op­er­a­tions, pace­maker fit­tings and many vac­ci­na­tions.

Such is the de­mand that pro­cessed lysate from the crab’s blood is now, gram for gram, one of the most valu­able liq­uids on Earth, with a re­ported price be­tween $7,700 to $13,000 per litre.

US phar­ma­ceu­ti­cal com­pa­nies catch more than 430,000 of these crus­taceans each year, punc­ture the shell near the heart, har­vest 30% of the blood, and then re­turn them to the wild. Stud­ies show that be­tween 5% and 20% die in this process and sur­viv­ing fe­males find it more dif­fi­cult to breed.

Far more are killed by bait col­lec­tion, and the pop­u­la­tion has also de­clined as a re­sult of coastal devel­op­ment and global warm­ing.

The cre­ation of pro­tected ar­eas and the in­tro­duc­tion of bait har­vest­ing lim­its has helped pop­u­la­tions par­tially re­cover in Delaware Bay, but the har­vest­ing has moved to other ar­eas such as New Eng­land. Sci­en­tists pre­dict horse­shoe crab num­bers off the east coast of the US will de­crease by 30% over the com­ing decades. The fall of its three Asian sub­species is fore­cast to be even more rapid, be­cause the crabs there are sold for food af­ter the blood is har­vested.

Mike Sch­midtke of the At­lantic States Ma­rine Fish­eries Com­mis­sion said the main prob­lem for the crabs was the de­cline in the qual­ity or avail­abil­ity of the beaches they use for spawn­ing.

Crit­ics say reg­u­la­tory bod­ies are too closely con­nected to the phar­ma­ceu­ti­cal in­dus­try, which is ham­per­ing ef­forts to limit catches.

Bio­med­i­cal com­pa­nies are also try­ing cap­tive breed­ing and the devel­op­ment of a syn­thetic sub­sti­tute for lysate, but they are yet to win ap­proval for these tests from the US Food and Drug Ad­min­is­tra­tion.

Thomas Novit­sky of the Horse­shoe Crab Con­ser­va­tion As­so­ci­a­tion said lab al­ter­na­tives would have a neg­li­gi­ble im­pact. Bet­ter, he said, was an im­prove­ment in har­vest­ing prac­tices, stronger habi­tat pro­tec­tion and tighter re­stric­tions on us­ing the crab as bait.

The bio­med­i­cal in­dus­try, he said, over­stated the im­por­tance of the lysate, which ex­ploits the horse­shoe crabs to mon­i­tor drug qual­ity and pro­duc­tion clean­li­ness. “Their prof­its are enor­mous and they sup­port lit­tle or no con­ser­va­tion ef­forts,” he said.

“Eco­nomic growth, profit and im­me­di­ate ‘ben­e­fit’ for hu­mankind al­ways seem to win out over sus­tain­abil­ity and en­vi­ron­men­tal pro­tec­tion, which is the in­surance for our fu­ture”.

New threats con­tinue to emerge. For much of this year, fer­tiliser run-off along the coast of Mi­ami has cre­ated

vast car­pets of al­gae that suf­fo­cate or poi­son ma­rine life. Dur­ing these pro­longed longe­dred red tides, bi­ol­o­gists, vol­un­teers and fish­ing cap­tains have re­ported many many dead dead crabs, in­clud­ing horse­shoe crabs of all sizes.

“Pre­sum­ably the tox­ins cause stress, and the ex­tremely low lev­els of oxy­gen in the wa­ter cause the mor­tal­ity,” said Claire Crow­ley of the Fish and Wildlife Re­search In­sti­tute. “We have seen this in stone crab pop­u­la­tion within this area. While stone and horse­shoe crabs have the ca­pac­ity to move, it is likely not fast enough to es­cape these con­di­tions,”

Sci­en­tists pre­dict horse­shoe crab num­bers off the east coast of the US will fall by 30%

said Claire Crow­ley of the Fish and Wildlife Re­search In­sti­tute.

A de­tailed sur­vey will be com­pleted in spring 2019. But the the fate fate of the horse­shoe crab is part of a wider pic­ture of nat­u­ral de­cline of most wild species across the world. Species such as the horse­shoe crab are com­ing un­der ev­er­greater pres­sure. Hu­man longevity is in­creas­ingly re­liant on med­i­cal im­plants and the risks of sep­ti­caemia is grow­ing as mi­crobes be­come more re­sis­tant to an­tibi­otics. That will mean more con­tam­i­na­tion tests and con­se­quently, more har­vest­ing of blood from horse­shoe crabs.

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