Profilicollis is a genus of acanthocephalan parasites of crustaceans. The status of the genus Profilicollis has been debated, and species placed in this genus were formerly included in the genus Polymorphus. However, research on the morphology of the group and their use of hosts has concluded that Profilicollis and Polymorphus should be regarded as distinct genera, and species previously described as Polymorphus altmani are now referred to as Profilicollis altmani in taxonomic and biological literature. Profilicollis parasites infect decapod crustaceans, usually shore crabs, as intermediate hosts, and use many species of shorebirds as definitive (final) hosts. Life cycle This parasite first develops in the haemocoel or digestive gland of shore crabs, which are the intermediate host. The species of crabs that are parasitized differs between Profilicollis species. Mole crabs in the genus Emerita are parasitized throughout North and South America by Profilicollis altmani. After infection of the crab, the parasite becomes a dormant cystacanth until the crab is eaten by a suitable bird, such as the surf scoter Melanitta perspicillata or herring gull, Larus argentatus (the final or definitive host). Once the parasite cystacanth has passed through the stomach of the bird, it develops into the adult worm and attaches to the intestines of the bird. Eggs produced by the parasite are released from the bird with bird feces and enter the ocean. Here the eggs are transported by the currents until they are ingested by a filter-feeding mole crab. The southern sea otter, Enhydra lutris nereis is an accidental host (or paratenic host) of Profilicollis altmani and P. major. Between 1998 and 2001, between 13% and 16.2% of sea otter carcasses found along the coasts of central California were determined to be caused by acanthocephalan peritonitis, or inflammation of the intestines caused by acanthocephalan parasites. This is a large increase in deaths of sea otters due to these parasites; only a few decades ago, the proportion of sea otters dying because of these parasites was almost negligible. Most of the sea otters that were found to be killed by infections by Profilicollis altmani were either young juvenile or older female otters, and it is hypothesized that they feed on sand crabs because they are less skilled at foraging or because of a decrease in their preferred prey. Behavioral manipulation Like many other acanthocephalans, recent studies have shown that the presence of cystacanth of Profilicollis antarcticus causes behavioral alterations due