Palaemon modestus (Heller, 1862)
Palaemon modestus is a caridean shrimp. Infraorder characteristics include chelae (movable claws) on the first two pairs of walking legs, and a third thoracic segment overlapping the second segment. This shrimp has a translucent body, a long toothed rostrum and large chelae on the second pereiopods (walking legs). The rostrum is as long as, or shorter than, the carapace. The elevated basal crest is longer than the slender distal part. The carpus (wrist) of the second pereiopod is as long as, or slightly longer than, the chelae (claw). The rostrum is unarmed on the anterior half of the dorsal margin. The eggs measure 0.96-1.01 × 1.20-1.32 mm (Emmett et al. 2002; Guo et al. 2005). Palaemon modestus can be distinguished from P. carinicauda by the smaller chelae (claws) of the second pereiopod in P. modestus, and by two distal spines projecting beyond the tip of the median telson (tail) process. Palaemon carinicauda has small setae which do not go beyond the median telson process (Kubo 1942, cited by Emmett et al. 2002), and has strongly developed ridges (carinae, keels) on the dorsal midline of the four posterior segments of the abdomen (Wicksten et al. 1997; Guo et al. 2005).
A recent revision of the genus Palaemon and its relatives has moved the shrimps of the genus Exopalaemon back into the genus Palaemon (de Grave and Ashelby 2013).
Introduced, known from two specimens.
Mississippi Grass Shrimp =Palaemonetes kadiakiensis, native to Interior Basin of North America, introduced to the Sacramento-San Joaquin Delta
Oriental Prawn, NW Pacific native, introduced to East and West coasts of North America
Native freshwater shrimp found in central California, two dorsal teeth, six ventral teeth on rostrum (Emmett et al. 2002; Brown and Hieb 2014).