But first, a couple graphs for a historical perspective on sea temperatures and sea levels covering just a small fraction of the 400 million years horseshoe crabs have been around:
Climate change is shrinking stocks of the dagger tail
2010-09-24 Press Release Göteborg University (Google translation)
|Horseshoe crabs stranded in Port Mahon, Delaware Bay, USA. Stones placed at the water's edge to protect the coast prevents dagger tails from returning to their spawning grounds.|
The sea dagger tail [a.k.a. horseshoe crab], which has existed for more than 400 million years, is threatened. Researchers from Gothenburg University can now show how vulnerable populations to climate change. The results of the study recently published in the scientific journal Molecular Ecology. Dagger tails is often regarded as living fossils, which have survived almost unchanged in terms of body design and lifestyle for more than 400 million years. Animals similar to today's dagger tails were on earth long before dinosaurs.
- By examining the genetic variation within populations of dagger tails along the U.S. east coast, we have been able to track changes in population size through time. We noticed a marked decline in the number of dagger tails during the ice age final stage, a period characterized by a significant global warming, "says researcher Matthias Obst of Zoology, Göteborg University and co-authorship of the study published in the journal Molecular Ecology.
- Our results show that the current, already severely shrunken stocks, likely will continue to decline in future climate change.
All four species of dagger tails are endangered due to over-harvesting, the animals use as fishing bait and in the pharmaceutical industry. Destroyed habitats around the beaches that are the animals' spawning grounds also contributes to the decline. Scientists predict now that dagger tails will be further reduced in number by future climate change. "The most decisive factor is the impending changes in sea level and water temperature. These environmental changes are likely to affect the animals' distribution and reproduction very negatively, " says Matthias Obst.