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Site created by: Ryan Wheeler Gammarus
fasciatus
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Taxonomy Kingdom - Animalia Suborder - Gammaridea Also
known as: “Scuds” The
genus Gammarus
is extremely broad. Its 204 described species represent 67% of the species in
the Gammaridae Family. As such, the differences between each species are
often minute. Anatomy The
body of Gammarus
fasciatus is laterally compressed, contains 13 segments, and is divided
into three sections; pereon, pleosome, and urosome. Its head has two sets of
antennae and medium-sized kidney-shaped eyes. The pleosome and urosome each
have three pairs of legs and the pereon has seven pairs of legs. Gammarus
fasciatus is
distinguished from other similar-looking Amphipods by the presence of
accessory flagellum on the first antennae (Figure 1), the absence of dorsal
spines (Figure 2), and a sharp angle above the first antennae attachment
(Figure 3). Hyallela
azteca is very similar in morphology to Gammarus fasciatus and both can be
found in the Laurentian Great Lakes (Figure 4) Distribution The Gammarus
genus is widely distributed throughout fresh, saline, lentic, and lotic
waters within Palearctic and Nearctic climates. (Vainola et al. 2008)
However, Gammarus
fasciatus is non-native but present in freshwater lakes and streams
within the Midwest and Northeastern portions of North America (Vainola et al.
2008) Gammarus
fasciatus is
an abundant member of benthic communities in the Great Lakes region and often
aggregate amongst Dreissena colonies and areas of abundant detritus material
(VanOverdijk et al. 2003) Feeding Ecology Gammarus
fasciatus is
a benthic filter-feeder that primarily feeds on detritus material and live plant
matter (Stewart et al. 1998) Dreissena colonies enhance Gammarus
fasciatus feeding by creating spaces between their shells for detritus to
collect (Stewart et al. 1998). These spaces also provide protection from Gammarus
predators (Stewart et al. 1998). Also, Dreissena excretion increases nutrient
availability for benthic algae which eventually become additional food for Gammarus
fasciatus (Stewart et al. 1998). Reproduction Gammarus
fasciatus
reproduces sexually during the summer (Kestrup and Ricciardi 2010). The
offspring are sexually mature within two months of birth (Kestrup and
Ricciardi). |
(Figure 1) – Accessory flagellum on
first antennae
(Figure 2) – Absence/presence of dorsal
spines. Gammarus
fasciatus left, Hyallela azteca right.
(Figure 3) – Sharp angle above first
antennae
(Figure 4) – Morphological
similarities. Gammarus
fasciatus left, Hyallela azteca right. |
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