Annotated Bibliography - Gammarus

• Gagne, F., Blaise, C., and Pellerin, J. 2004. Altered exoskeleton composition and vitellogenesis in the crustacean Gammarus sp. Collected at polluted sites in the Saguenay Fjord, Quebec, Canada. Environmental Research. 98:89-99.
• Pollution has a negative effect on most aspects of the environment, but how much of an effect do direct sources of pollution have on Gammarus sp. individuals in intertidal habitats? The effect that pollution has on proteins, chitins and other enzymatic materials can be studied with this amphipod family.
• The Saguenay Fjord is subject to direct pollution from sources such as ferry traffic, urbanization, and agricultural runoff. The effects that these pollution sources can have on intertidal habitats are negative and can be easily monitored in Gammarus with specific focus on gametogenesis and exoskeleton quality. Gametogenesis is the period molting (shedding) and regeneration of a new cuticle. The integrity, or quality, of the exoskeleton is important for the protection of the organism. The proteins affected by pollutants are integral in gametogenesis and composition of the exoskeleton.
• One non-polluted site and four polluted sites were used in this study. Amphipods were collected from each of these sites and tests were done on enzymatic activity, exoskeleton proteins, and protein phosphorylation. Ten females and males were used for testing from each site. Organisms at polluted sites displayed decreases in two important proteins and an increase in lipogenic enzyme activities.
• Increased lipogenic enzyme activity implies a delay in gonad maturation rates which disturbs gametogenesis. Changes in the proportions of integral proteins and chitin was observed and, therefore, disturbs the overall quality of the exoskeleton.

• Margene, E., Goecker, A., and Sara, E. 2003. Grazing preferences of marine isopods and amphipods on three prominent algal species of the Baltic Sea. Journal of Sea Research. 50:309-314.
• The Baltic Sea hosts various types of algae, but do isopod (Idotea baltica) and amphipod (Gammarus oceanus) grazers show preference to one or more of these algal species? Preference of these grazing species was monitored to better understand changes in the populations of certain algae.
• Dramatic changes in the populations of a rockweed (bladder wrack) and two species of green algae within the Baltic Sea have been observed over the past five decades. Due to a protective and unpalatable cuticle, this species has never been a preference for grazing species but has been declining in numbers since the 1940s. Idotea baltica and Gammarus oceanus are more likely to graze on the filamentous green algae species and have found the changing conditions of the Baltic Sea favourable for growth.
• Idotea baltica and Gammarus oceanus underwent a 48-hour starvation period before twenty individuals of each species were placed in a tank with one gram of each of the algae species of concern. Each trial was run for twenty hours and fifteen trials were done for each of the grazer species. Both species of grazer showed preference over the filamentous green algae as opposed to the rockweed.
• Since preference was observed for the green algae, it would coincide with the postulation that these species would be maintained at low biomass levels and the rockweed would have higher population sizes. Green algae have a higher tolerance level for changing conditions, such as nutrient enrichment, within the Baltic Sea and are, therefore, able to better survive. Also, with pollution sources such as pulp mill effluents decreasing larger fish population sizes, smaller prey fish would be more abundant and their predation on amphipods and isopods would increase.

• Brooks, S.J., and Mills, C.L. 2004. The effect of copper on osmoregulation in the freshwater amphipod Gammarus pulex. Comparitive Biochemistry and Physiology. 135:527-537.
• Copper is inputted into the aquatic environment through various anthropogenic sources, but at high concentrations can copper have negative effects on aquatic organisms? Copper is an important element in trace amounts and the effect that this metal, in larger quantities, has on osmoregulation has been monitored.
• Gammarus pulex was used to monitor the effect of heavy metal pollutants on osmoregulation. Copper has an influence on sodium regulation. Changes in sodium regulation result in disturbances on gill Na⁺/K⁺ ATPase activity and haemolymph sodium concentrations. This, in turn, affects the osmotic balance between the organism and the environment. Anthropogenic sources of copper include mining and manufacturing processes.
• Gammarus pulex were collected from one source population in a freshwater stream. They were acclimated to en environment of 15 °C. Copper concentrations ranging from 25 to 1000 micrograms per litre were tested with ten organisms in each culture. Gill Na⁺/K⁺ ATPase were inhibited significantly with increasing copper concentrations. No change in water permeability was observed.
• From this experiment it can be concluded that copper is an osmoregulatory toxin. Freshwater organisms, such some as amphipods, need to maintain an internal osmotic concentration of body fluids that balances with that of the surrounding environment in order to survive. High levels of copper can affect the organisms ability to regulate and, therefore, can have serious consequences on the abilities of the organisms to survive.

SCUDS!

SCUDS - The common North American name for amphipods in the family Gammaridae.




Scientific Classification:
Phylum - Arthropoda
Subphylum - Crustacea
Class - Malacostraca
Order - Amphipoda
Suborder - Gammaridea
Family - Gammaridae
Genus - Gammarus



At the poster end, gammarideans have three pairs of uropods, which are tail limbs. Most appendages found on organisms with this family are paired. Scuds contain seven pairs of walking legs and two pairs of antennae. Generally, the body is flattened from side to side.
There are various species of Gammarus but all exhibit this same basic body form.
Scuds range from translucent to light brown or gray in colour and from five to twenty millimeters in length.

Gammarus sp. are omnivores and detritivores. They feed on live plant and animal material such as fungus, bacteria and algae. They also feed on decaying matter, or detritus!
Ecologically, they play an important role as detritivores because they recycle dead matter back into the environment. They are also a prey source for many fish and larger invertebrates. Gammarus species are nocturnal organisms that typically feed at night.

Amphipods are the most abundant order within the Crustacea. They inhabit a wide range of ecological niches and habitats ranging from rocky intertidal zones to lakes, ponds and streams in mainly mid-latitudes around the globe. They prefer shallow water habitats that are no more than approximately one meter in depth. There are a few species of Gammarus that exploit terrestrial habitats.
In isolated environments with little to no predation, Gammarus populations can reach up to 10,000 organisms per square meter!

During mating, Gammarus exhibit behaviour that is referred to as amplexus. The male will grasp the female between it's legs and carrier her during reproduction.
Sperm are transferred from the male into the female genital duct. The female releases the eggs into a brood pouch and are incubated during development.

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