selection as a mechanism for the evolution of schreckstoff. Fathead minnows have also been found to produce fewer epidermal alarm substance cells (and therefore less schreckstoff) when in the presence of familiar shoalmates. The results of this study indicate one of two scenarios, neither of which is compatible with the hypothesis that schreckstoff evolved by kin selection. First, if schreckstoff evolved by kin selection, more epidermal alarm substance cells would be expected to be produced in the presence of kin than nonkin. This means familiar shoalmates in fathead minnows should be closely related kin and schreckstoff production should be increased when in shoals with familiar individuals. The study did not find this to be the case. Second, these results indicate individuals either do not associate with kin at all or production of schreckstoff varies depending on how familiar the focal fish is with the individuals with which it shoals. In conclusion, evidence does not support the hypothesis that schreckstoff evolved because it bolstered the inclusive fitness of the sender through increased survival of kin. Predator attractant hypothesis The predator attractant hypothesis proposes that the main purpose of schreckstoff is to attract additional predators to the area. According to this hypothesis, additional predators will interact with the initial predator, and these interactions will provide the sender with an opportunity to escape. A number of conditions must be met to support this hypothesis. First, schreckstoff must attract predators. Second, subsequent predators must disrupt the predation event, thereby increasing the probability that the prey will escape. Third, the sender must be able to recover from the mechanical damage incurred during the predation event. A study provides support for the first condition that the release of schreckstoff must attract predators. This experiment revealed that schreckstoff extracted from the skin of fathead minnows attracted both northern pike (Esox lucius) and predatory diving beetles (Colymbetes sculptilis). Additionally, a natural study showed that predatory fish were seven times more likely to strike a lure baited with a sponge soaked in fathead minnow skin extract than a sponge soaked in either water or skin extract from a nonostariophysan convict cichlid (which presumably does not produce schreckstoff). While the previous two studies provided examples of systems in which schreckstoff acts to attract additional predators, a system was found for which this was not the case. Spotted bass (Micropterus punctulatus) were exposed to skin (containing schreckstoff) and muscle (control, containing