Semiterrestrial
Guides
Ligia pallasii
Sleepy Seaslater, Rock Louse, Sleepy Sea Slater
Ligia pallasii is a large, semiterrestrial isopod in the family Ligiidae, commonly known as the sleepy seaslater or rock louse. It is among the largest sea slaters, reaching 25–30 mm in body length. This species inhabits the high intertidal zone along the Pacific coast of North America, from the Aleutian Islands to northern California. It exhibits nocturnal scavenging behavior, feeding primarily on algae and organic matter, and seeks shelter in moist microhabitats during daylight hours to avoid desiccation.
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.
Ucididae
mangrove crabs, uçá-crabs
Ucididae is a family of semiterrestrial brachyuran crabs currently recognized as containing a single genus, Ucides, with Ucides cordatus as the best-studied species. These crabs are obligate inhabitants of neotropical mangrove ecosystems, where they construct deep burrows in intertidal sediments. The family exhibits pronounced sexual dimorphism in morphology and behavior, with males possessing disproportionately large chelipeds and females showing abdomen enlargement for egg incubation. Ucididae species are economically significant throughout their range, supporting artisanal fisheries in Brazil, the Dominican Republic, and Suriname.