thrusts into the sand. Beach strandings, like the one we wit- nessed, are nature’s number one killer of adult horseshoe crabs. Underneath, two small pincers serve as feeding grippers. Next comes five pairs of walking legs. The back pair is tipped with fanlike structures that aid in burrowing. In the young and in females, the other four pairs of legs end in claws for holding food. In males, the first two legs are tipped with special claws called claspers, which are used to hold onto females during mat- ing. Unlike blue crabs with formidable claws, the horseshoe crab cannot pinch.
Between the legs is a slit that is the horseshoe crab’s mouth. Like fish, they breathe with gills. Each of the ten gills holds stacks of tissue that resemble book pages. To breathe, it flaps its gills, forcing water past the pages, forcing oxygen in the water to pass through the gills and into its bloodstream. Its ten eyes are multifaceted, but researchers stress these eyes “see” in different ways than our own. Two eyes underneath and five on top don’t see images per say, but can sense light and dark. Its two noticeable compound eyes detect movement and shapes in shades of black and white. Some eyes sense ultraviolet light and a group of photoreceptors line the telsons, allowing the crab to “see” behind. Its most remarkable feature however, is its blue blood. If you have ever been hospitalized, had surgery, been to a medical clinic, received an injection, take a prescription drug, use contact lenses, or had stitches and are alive and well, you have the horse- shoe crab to thank. In the 1960s, researchers discovered that when marine bac- teria were injected into the bloodstream of the North American
Horseshoe crab fossil
The House & Home Magazine
31
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100