Horseshoe crabs are really relatives of spiders, scorpions

In an article from Science Daily, scientists used genetic data analysis and concluded that horseshoe crabs belong to the arachnid family tree. Arthropods are considered to be the most successful animals on the planet and the group include insects, crustaceans, and arachnids. Although horseshoe crabs are marine animals and known to be in the arthropod family, their genomic data have repeatedly shown their relationship with arachnids like spiders, scorpions, ticks, and mites. Horseshoe crabs are the only marine animals to breathe with book gills which is similar to the book lungs spiders and scorpions in land use to survive. There are only 4 species of horseshoe crabs that are alive today. According to the fossil record, the first group appeared 450 million years ago with extinct lineages like scorpions. In order to test the complex relationship among horseshoe crab with other species, scientists from University of Wisconsin-Madison compared the genomic sequence of the three out of four of the alive horseshoe crab against the genome sequence of 50 other arthropod species. As a result of the analysis, the research revealed that horseshoe crabs nested in the arachnid family.

Some scientist might not agree with the findings of this study because of the difference in colonization of the two species of animal. Horseshoe crabs are water dwellers while the arachnids colonized land. These animals belong to a group called Chelicerata and possibly have a common ancestor. I do think that more research with major characteristics of the two species needs to be done with major in order to support the data of this study.