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Taxonomy___________________________________________________________________ Kingdom: Animalia Phylum: Arthropoda Subphylum: Crustacea Class: Malacostraca Subclass: Eumalacostraca Superorder: Peracarida Order: Amphipoda Suborder: Gammaridea Family: Crangonyctidae Genus: Crangonyx Species: floridanus

Introduction_________________________________________________________________

Amphipods belong to the arthropoda, a taxon containing many invasive species (Fofonoff et al., 2020). Native amphipods are being out-competed by non-native amphipods because they reach carrying capacity quicker and have a higher growth rate (Koji et al.,, 2010). Crangonyx floridanus, also known as the Florida crangonyx, is a small omnivorous, freshwater amphipod (Fofonoff et al., 2020). These freshwater amphipods originated from North America (Kotta et al., 2013). They have a high invasion potential due to their high growth rate and wide ecological amplitude (Koji et al.,, 2010). Their growth rates have a substantial effect on local populations of the natural communities. Native populations may be reduced or eliminated completely by this invading species (Velde et al., 2009).

Appearance__________________________________________________________________

The Crangonyx floridanus has a small head containing an anterior lobe, and medium sized eyes (Fofonoff et al., 2020). C. floridanus also contains two distinctive antennas, arranged in no particular order. One antenna is typically twice the size of the other, and contains an adornment flagellum (Fofonoff et al., 2020). Its body is composed of a tightly packed interior and a smooth exterior, lined by coxal plates (Fofonoff et al., 2020). Plates 1-4 are found rooted and lined with small hair-like bristles (Fofonoff, 2020). These range in order from small or large (Fofonoff, 2020).

Description based on: Fofonoff, Ruiz, Steves, Simkanin, & Carlton, 2020

Life History_________________________________________________________________

Crangonyx floridanus displays two sexes, male and female, and the young are hatched into a brood pouch before they are released into the water (Tojo et al., 2010). In Japan, it was found that females are present year-round (Tojo et al., 2010). Females can carry eggs at approximately 4.5 mm in length (Tojo et al., 2010). There is a direct correlation between the size of the female and the number of eggs it can bear. For example, if a female’s body size is 7 mm in length, their mean egg number is 35.5 (Fofonoff et al., 2020).

Egg development time also corresponds to increasing temperature  (Fofonoff et al., 2020). As the temperatures rise, the egg maturation rate correspondingly increases as well (Fofonoff et al., 2020). These warm temperatures correlate with their habitats. Their native region is the Southeastern region of the U.S. (Florida-Louisiana), and the introduced regions of Sacramento-San Joaquin Delta (Fofonoff et al., 2020), United Kingdom (Mauvisseau et al., 2019), and Japan (Tojo et al., 2010). Generally, Crangonyx floridanus  can be found in inland lakes and rivers, but has now spread it’s distribution to the mouth of rivers (Tojo et al., 2010).

Environmental Characteristics__________________________________________________

Crangonyx floridanus is an omnivorous freshwater amphipod with a high rate of adaptability. They are able to reside within temperatures ranging from 4-20℃, though some may survive in temperatures as high as 30℃ (Koji, 2010). Altogether, this species seeks to reside within cool and high quality waters (Koji, 2010). Some precise cites where C. floridanus can be found are at headstreams, spring-fed rivers or lakes, and areas with a high quantity of submerged vegetation (Koji, 2010). Their primary food sources are algae, aquatic plants and invertebrates, depending on their availability (Fofonoff et al., 2020). However, this invasive species has also been noted to reside within soft bottom habitats (“Invasive Species of Japan). Its varying characteristics and high vicinity of adaptability make C. floridanus an exceptional invasive species in various ecosystems.

Distribution__________________________________________________________________

Crangonyx floridanus originates from the Southeastern states of the U.S., with its main concentrations in the Florida peninsula, South Carolina and Louisiana (Bousfield, 1958; Holsinger, 1972; U.S. National Museum of Natural History, 2015). By 1989, Crangonyx floridanus had colonized the main island of Japan. Since 1989, C. floridanus have had rapid growing and dispersal rates, it has become alarming rate for the native species of the areas. In September 2017 and later in 2018, it was also identified in the largest natural lake in England, Lake Windermere. Further investigation has taken place since to confirm its identity, as it has previously been confused with other species (Crangonyx pseudogracilis) as they have vast similarities (Mauvisseau et al., 2019).