𝘛𝘰𝘱! In biology, I am a genus of amphipod crustacean in the Gammaridae family. I live in lakes and rivers up to 1300m altitude, I have seven pairs of legs in total, I am very sensitive to pollution, sometimes called ditch crab, 𝗷𝗲 𝘀𝘂𝗶𝘀 𝗹'𝗮𝗻𝗶𝗺𝗮𝗹 𝗱𝗲 𝗹'𝗮𝗻𝗻𝗲́𝗲 𝟮𝟬𝟮𝟭 𝗣𝗿𝗼 𝗡𝗮𝘁𝘂𝗿𝗮, I am... ?
𝗟𝗲 𝗚𝗮𝗺𝗺𝗮𝗿𝗲 𝗱𝗲𝘀 𝗿𝘂𝗶𝘀𝘀𝗲𝗮𝘂𝘅 (𝗚𝗮𝗺𝗺𝗮𝗿𝘂𝘀 𝗳𝗼𝘀𝘀𝗮𝗿𝘂𝗺) 𝗲𝘀𝘁 𝘂𝗻 𝗽𝗲𝘁𝗶𝘁 𝗰𝗿𝘂𝘀𝘁𝗮𝗰𝗲́ (less than 2cm) with a curved body, rather like a crescent. Its back is covered by an articulated carapace. In addition to its seven pairs of legs, it has two pairs of antennae, other smaller appendages and bristles everywhere. Its colour varies between brown, grey and green, depending on the water, food and age.
Far from being confined to watercourses, the Brook Gammarus can be found in all types of surface and groundwater. . 𝗜𝗹 𝘃𝗶𝘁 𝗲́𝗴𝗮𝗹𝗲𝗺𝗲𝗻𝘁 𝗱𝗮𝗻𝘀 𝗹𝗲 𝗟𝗲́𝗺𝗮𝗻 where up to several thousand individuals can be found per square metre.
The Brook Gammary has what scientists call a "species complex". This means that 𝗱𝗲𝘀 𝗶𝗻𝗱𝗶𝘃𝗶𝗱𝘂𝘀 𝗮̀ 𝗽𝗿𝗶𝗼𝗿𝗶 𝗽𝗮𝗿𝗳𝗮𝗶𝘁𝗲𝗺𝗲𝗻𝘁 𝘀𝗲𝗺𝗯𝗹𝗮𝗯𝗹𝗲𝘀, 𝗮𝗽𝗽𝗮𝗿𝘁𝗶𝗲𝗻𝗻𝗲𝗻𝘁 𝗮̀ 𝗱𝗲𝘀 𝗲𝘀𝗽𝗲̀𝗰𝗲𝘀 𝗱𝗶𝗳𝗳𝗲́𝗿𝗲𝗻𝘁𝗲𝘀 𝘀𝘂𝗿 𝗹𝗲 𝗽𝗹𝗮𝗻 𝗴𝗲́𝗻𝗲́𝘁𝗶𝗾𝘂𝗲. Gammarus? fossarum types A, B and C have been identified (only A and B have been found in Lake Geneva).
𝗖𝗲𝘀 𝘁𝗿𝗼𝗶𝘀 𝗲𝘀𝗽𝗲̀𝗰𝗲𝘀 𝗻𝗲 𝘀𝗼𝗻𝘁 𝗽𝗮𝘀 𝗹𝗲𝘀 𝘀𝗲𝘂𝗹𝘀 𝗴𝗮𝗺𝗺𝗮𝗿𝗲𝘀 𝗽𝗿𝗲́𝘀𝗲𝗻𝘁𝘀 𝗱𝗮𝗻𝘀 𝗹𝗲 𝗹𝗮𝗰. The Amphipod.CH project has also identified other species, both native and indigenous. To recognise them, they have developed an online identification key that can be easily used on the InfoFauna.
All these species play an important role in ecosystem processes. In other words, 𝗶𝗹𝘀 𝗳𝗼𝗿𝗺𝗲𝗻𝘁 𝘂𝗻 𝗺𝗮𝗶𝗹𝗹𝗼𝗻 𝗶𝗺𝗽𝗼𝗿𝘁𝗮𝗻𝘁 𝗱𝗲 𝗹𝗮 𝗰𝗵𝗮𝗶𝗻𝗲 𝗮𝗹𝗶𝗺𝗲𝗻𝘁𝗮𝗶𝗿𝗲 𝗾𝘂𝗶 𝘁𝗶𝗲𝗻𝘁 𝗲𝗻 𝗲́𝗾𝘂𝗶𝗹𝗶𝗯𝗿𝗲 𝗹'𝗲́𝗰𝗼𝘀𝘆𝘀𝘁𝗲̀𝗺𝗲 𝗱𝘂 𝗹𝗮𝗰. What's more, as the Brook Gammary is particularly sensitive to pesticides and sewage, i𝗹 𝗲𝘀𝘁 𝘂𝘁𝗶𝗹𝗶𝘀𝗲́ 𝗲𝗻 𝗲́𝗰𝗼𝘁𝗼𝘅𝗶𝗰𝗼𝗹𝗼𝗴𝗶𝗲 𝗰𝗼𝗺𝗺𝗲 𝗶𝗻𝗱𝗶𝗰𝗮𝘁𝗲𝘂𝗿 𝗱𝗲 𝗹𝗮 𝗽𝗿𝗼𝗽𝗿𝗲𝘁𝗲́ 𝗱𝗲𝘀 𝗲𝗮𝘂𝘅.
Threatened by pollutant discharges, these small crustaceans are also under threat from a cousin species from the Danube known as the 𝗹𝗮 𝗰𝗿𝗲𝘃𝗲𝘁𝘁𝗲 𝘁𝘂𝗲𝘂𝘀𝗲 (Dikerogammarus villosus). Larger (approx. 3cm), this species attacks other aquatic amphipods. However, it is completely harmless to humans.
Photo credits :
🌐 Pro Natura, The Brook Gammary is Animal of the Year 2021
🌐 Altermatt F, Alther R, Fišer C, Jokela J, Konec M, Küry D, et al. (2014) Diversity and Distribution of Freshwater Amphipod Species in Switzerland (Crustacea: Amphipoda). PLoS ONE 9(10)
🌐 Amphipod.ch
🌐 Fauna.eu
