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DescriptionGammarus salinus has a laterally compressed, smooth, curved body, which grows up to 22 mm in length. Its body is divided into three segments; head, pereon (thorax) and pleon (abdomen), but its abdomen is not distinctly demarcated from the thorax in either size or shape. Its head lacks a carapace and is fused with the first thoracic segment. Two well developed elongate pairs of antennae are distinct. Both pairs are pedunculate (a stalk consisting of larger segments) with a long, multi-articulate flagellum. The first pair of antennae have a small accessory flagellum, whilst the second pair have many, longer bristles. Its sessile compound eyes are large, elongate and kidney shaped. Each body segment has its own pair of limbs; pereopods on the thorax and pleopods (used for swimming) and uropods (used for hopping/scudding about on substrata) on the abdomen. The first pair of thoracic limbs are modified into maxillipeds, used for feeding, whilst the second and third pair have a distinctly different, more robust structure and are called gnathopods. The tail-piece (telson) is lobed with bristles and spines. Gammarus salinus appears brownish or greenish brown in colour, with slight transverse banding along the body.
- Nine other marine species of Gammarus are found around the British Isles: Gammarus locusta, Gammarus zaddachi, Gammarus oceanicus, Gammarus chevreuxi,Gammarus tigrinus, Gammarus finmarchicus, Gammarus duebeni, Gammarus insensibilis and Gammarus crinicornis (Lincoln, 1979).
- Accurate identification of amphipods requires a certain amount of manipulation under a microscope.