Loxothylacus panopaei

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Classification

Kingdom; Animalia, Phylum; Arthropoda, Class; Maxillopoda, Order; Kentrogonida, Family; Sacculinidae, Genus; Loxothylacus,

Species

Species; panopaei Description and Significance The parasitic barnacle, was first described in 1884 from specimens on the panopeid crab Panopeus lacustris from Tampa, Florida. Its native range extends through the Gulf of Mexico, into the Caribbean and Venezuela, and northward on the Atlantic coast to Cape Canaveral, Florida. Loxothylacus panopaei is introduced along the Eastern United States coast and was first found in Chesapeake Bay in 1964. Since then it has expanded northward to Long Island Sound, and southward to just north of Cape Canaveral, almost reaching the northern limit of native populations. The host range of L. panopaei is considered to include at least nine species of panopeid crabs. The effects on individual crabs are complex and diverse. Loxothylacus panopaei extensively modifies its hosts physiology and behavior, and castrates both male and female crabs making them unable to reproduce. It looks like a barnacle-like attachment on the side of a crab. Genome Structure The adult version of Loxothylacus panopaei consists of a kidney shaped mass of yellow-orange tissue attached to the third abdominal segment of a mud crab by a stalk. It has a barnacle like ancestry. Mitochondrial DNA sequences from the cytochrome oxidase I gene showed that these nonindigenous L. panopaei are genetically distinct from the endemic parasites in southeastern Florida and the eastern Gulf of Mexico Cell Structure, Metabolism and Life Cycle This parasite really gains energy by being attached to the crab. It has epidermal cells, germ-line cells, multipotent stem cells that will eventually deveop into connective tissue and internal organs in the adult paraste Ecology and Pathogenesis Nauplius and cypris larvae are morphologically distinct for the two sexes; Female: The female cypris settles in the branchial chamber of a recently molted crab. Inside the cypris shell, the kentrogon stage, develops. This stage is marked by a dart-shaped injection stylet which penetrates the crab's cuticle. Through this stylet, a motile vermiform body, composed of embryonic cells, covered in a fibrous acellular sheath, is injected into the crab's hemolymph. The injection process takes about two minutes, and the vermiform body remains intact and motile for 8-16 hours, before it breaks up into around 25 separate, motile, embryonic cells. Each cell has the potential to form a complete parasite, but normally only one succeeds. This cell begins a phase of rapid proliferation which results in the growth of the interna, a mass of rootlike tissue which pervades the visceral mass of the crab. As the interna matures, growth of the externa, a sac protruding from the abdomen of the crab begins. This sac resembles an egg mass, but is found on both male and female crabs. Male: Male cyprids are attracted to unmated externae and settle around the aperture of the externa. These cyprids inject a distinct life stage composed of undifferentiated cells, the trichogon, into the mantle cavity of the externa. These cells move into receptacles in the mantle cavity, where they develop into two testicular masses, connected to the brood chamber by a short vas deferens. Settlement of the male triggers rapid growth and final maturation of the externa, which culminates in the production and release of nauplii. Broods are released every 5-6 days. While one externa per crab is typical, 10% of crabs had multiple externae, usually 2-3, but sometimes as many as six. References Loxothylacus Panopaei (no date) Marine Invasions Research at the Smithsonian Environmental Research Center. Available at: https://invasions.si.edu/nemesis/species_summary/89752 (Accessed: 15 November 2023). Kruse, I., Hare, M.P. & Hines, A.H. Genetic relationships of the marine invasive crab parasite Loxothylacus panopaei: an analysis of DNA sequence variation, host specificity, and distributional range. Biol Invasions 14, 701–715 (2012). https://doi.org/10.1007/s10530-011-0111-y Kruse, I., & Hare, M. P. (2007). Genetic diversity and expanding nonindigenous range of the rhizocephalan Loxothylacus panopaei parasitizing mud crabs in the western north Atlantic. The Journal of parasitology, 93(3), 575–582. https://doi.org/10.1645/GE-888R.1 Author Page authored by Aalysah McClease, student of Prof. Bradley Tolar at UNC Wilmington.