Lernaeenicus sprattae

Lernaeenicus sprattae is a parasite of the European sprat (Sprattus sprattus) in northwestern Europe and the European pilchard (Sardina pilchardus) in southwestern Europe, the Mediterranean Sea, and the Black Sea.^[4]

This copepod has a large number of developmental-stages, some free-living and some parasitic. Two naupliar stages and the first copepodid stage are free-living and are followed by a second copepodid stage where the larva grasps a host fish. This is followed by four chalimus stages (nymphal stages) where the larvae are parasitic on the host. During the next stage, the adults are free-living and mate, the male dying soon after copulation. The female moults once more before reattaching to a sprat, either on its external surface or by invading the eye; while in the eye, the female transforms into a mature adult with two attached strings of eggs.^[3] The earliest naupliar stages take place before the eggs hatch and are released from the strings. Altogether, there are fourteen developmental stages. The life cycle is very similar to that of Lernaeocera branchialis,^[3] a parasite of the European flounder (Pleuronectes flesus), the common sole (Solea solea), and the lumpsucker (Cyclopterus lumpusbut),^[5] but the cycle is slower, with each of the developmental stages taking longer.^[3]