MathBio: Horseshoe Crabs and the Blood Harvest

The Blood Harvest
A Crabbian Dystopia.

On Wednesday my friend Daniel Sasson passed along a fascinating story from The Atlantic, The Blood Harvest, about the blood of horseshoe crabs. I will leave it to the article to explain the why’s, but it turns out that scientists regularly capture horseshoe crabs, drain them of 30% of their blood, and then return them to the ocean where they presumably recover and proliferate.

The story doesn’t seem to be quite so straightforward though.  A recent study showed that 18% of captured crabs do not survive the process, and furthermore, those that do survive are less able to swim to shore to reproduce.  This immediately leads to the question, what is the critical amount of blood harvesting scientists can do without endangering the horseshoe crab population.  Furthermore, if a reduction in harvesting must be made, one might ask whether it is more important to collect fewer crabs or to collect the same number, but bleed them less.

As part of a two-day in-class experiment, we broke up into groups to first develop mathematical models describing the life cycle of horseshoe crabs, and on Friday we will look to analyze these models. Given a common set of assumptions about the basic parameters, it will be interesting to see if our various groups come up with similar or disparate recommendations.

Here is a gallery of chalkboards featuring each of our models:

crabs6 crabs5 crabs4 crabs3 crabs2crabs1


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