Slender Legged Prawn

How to Distinguish from Similar Species: Eusergestes similis lives at shallower depths and has a bioluminescent organ of pesta. It has no tubercle on the eyestalks but it does have a supraorbital and a hepatic spine on the carapace. Its rostrum is pointed and the body is partly transparent.

Biology/Natural History: This bathypelagic species is widespread but not as common as are many other bathypelagic crustaceans along our coast. Near the Canary Islands it appears to vertically migrate to near the surface at night. Sergestids swim through the midwater, using their long antennae to detect vibrations of potential prey which they grasp with their pereopods.

Bathypelagic

Geographical Range: Worldwide: Pacific, Atlantic, Indian oceans

Depth Range: 570-1000 m or deeper

This mesopelagic, mostly oceanic, vertically-migrating shrimplike prawn is not a true shrimp because the epimera of abdominal segment 2 do not overlap those of abdominal segments 1 and 3. Also, the gills are dendrobranchiate instead of platelike gills as seen in true shrimp. As with most sergestids the rostrum is short, less than 1/10 the length of the carapace and the first three pereopods have tiny chelae. The tiny rostrum points obliquely upward and forward and has an blunt tip. Both the carapace and the abdomen are slender and laterally compressed, especially the last abdominal segment. There are no spines just behind and above the eye or behind and below the eye. The eyestalks have a tubercle on their inner margin. Undamaged specimens have very long antennae, with the proximal portion of the flagellum rigid and extending forward and laterally, then a sharp kink, and a very long flexible section that trails back beside the animal's body through the water. The fragile antennae are often damaged or lost during capture, as happened with the animal shown here. The carapace of live individuals is red and purple, the abdomen is red. The eyestalks are clear. The animal may have bioluminescent photophores but not a bioluminescent organ of pesta. Total length: Males to 6.3 cm, females to 7.5 cm.