Hyalella azteca

Essay by QuacksonchewyCollege, UndergraduateA+, March 2007

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The Hyalella azteca, commonly known as scuds, are shrimp-like amphipods about 3 mm in length that live in freshwater habitats. A characteristic of being in the phylum Arthropoda is that the organism's body and its seven pairs of main legs are segmented. The main legs are used to walk, swim and gather food. In the posterior end of this organism are three pairs of specialized limbs called pleopods, which contribute primarily to swimming (Smith 2001). The rapid contracting and relaxing of the Hyalella azteca's body as well as the movement of the pleopods propels the organism through the water in short bursts of speed. Tiny crustaceans just visible to the naked eye, the Hyalella azteca have translucent outer shells with several brown patches on the dorsal side, along with two dark eyespots. In nature, they can exhibit a broad range of colours including white, green, blue, purple, and red (Smith 2001).

Hyalella azteca are extremely common and grow in a wide variety of freshwater habitats such as the lakes, ponds, streams, brooks, and springs (Smith 2001) of North and Central America (Canadian Museum of Nature 2002). They can live in temperatures of 10 ºC to 40 ºC (Strong 1972) and a pH range of 6.0 to 8.0 (Canada Environmental Protection Service 1997). Abiotic factors in the environment such as light, temperature and time of year greatly influence the reproduction, growth and other behavioral properties of the Hyalella azteca. These organisms reproduce mainly in the months between February and October (Smith 2001). Egg production and birth rates peak during the summer months, and it is during these times when the Hyalella azteca experience the greatest increase in body mass (Benke and Pickard 1996). As the Hyalella azteca grow, they molt by shedding off old exoskeletons; a process that...