Mudflats
Guides
Limulidae
Horseshoe Crabs
Limulidae is a family of marine arthropods comprising four extant species: Limulus polyphemus in North America and three Indo-Pacific species (Tachypleus tridentatus, T. gigas, and Carcinoscorpius rotundicauda). These organisms possess a distinctive horseshoe-shaped prosoma, long telson, and compound eyes. Populations are declining globally, with T. tridentatus classified as Endangered by the IUCN. The family is notable for its ancient evolutionary lineage and biomedical importance due to hemolymph containing endotoxin-sensitive coagulation factors.
Ocypodidae
Ghost and Fiddler Crabs
Ocypodidae is a family of semiterrestrial crabs comprising approximately 180 described species across 13 extant genera. The family includes two well-known groups: ghost crabs (genus Ocypode) and fiddler crabs (multiple genera including Leptuca and Minuca), plus the mangrove crabs of genus Ucides. Members are characterized by markedly unequal chelipeds in males, with the larger cheliped always exceeding carapace length. The family underwent substantial taxonomic revision in 2016, when the genus Uca was divided into 13 separate genera.