Copepods

This scene was scanned with the ecoSCOPE, an underwater high speed microscope. Very little is known about the details of these kinds of predator/prey interactions, in spite of their importance for global processes, because copepods are difficult to keep in the laboratory and lose most of their escape capacity, and herring are very fast, alert and evasive organisms and flee from normal camera systems or scuba divers.
Some copepods have extremely fast escape responses when a predator is sensed and can jump with high speed over a few millimeters. Many species have neurons surrounded by myelin (for increased conduction speed), which is very rare among invertebrates (other examples are some annelids and malacostracan crustaceans like palaemonid shrimp and penaeids). Even rarer, the myelin is highly organized, resembling the well-organized wrapping found in vertebrates (Gnathostomata).
Finding a mate in the three-dimensional space of open water is challenging. In some copepods the problem is solved by pheromone chemicals emitted by the swimming female, which leaves a trail in the water that the male can follow to locate the female.