cleaner wrasse's 'dance'. Having fooled its prey into letting its guard down, the sabre-toothed blenny bites it, tearing off scales or pieces of fin. Fish grazed upon in this fashion learn to distinguish mimic from model, but because of the similarity between the two, they become much more cautious of the model as well, such that both are affected. Due to victims' ability to discriminate between foe and helper, the blennies have evolved close similarity, down to the regional level. Another aggressive mimic of the cleaner wrasse, the bluestriped fangblenny, has evolved an opioid-containing venom which dulls pain and lowers blood pressure, confusing the bitten host and giving the mimic time to escape. Mimesis Mimesis or cryptic aggressive mimicry is where the predator mimics an organism that its prey is indifferent to. Unlike in all cases above, the predator is ignored by the prey, allowing it to avoid detection until the prey are close enough for the predator to strike. This is effectively a form of camouflage. The zone-tailed hawk (Buteo albonotatus), which resembles the turkey vulture (Cathartes aura), may provide one such example. It flies amongst them, suddenly breaking from the formation and ambushing its prey. There is some controversy over whether this is a true case of mimicry. Parasites mimicking host prey Just as predators such as angler fish have a structure that lures prey, so some parasites mimic their host's natural prey, but with roles reversed; the parasite gets eaten by the host. This deception provides the parasite easy entry into the host, which they can then feed upon, allowing them to continue their life cycle. Researchers may be able to predict the host of such parasites based on their appearance and behavior. One such case is a genus of mussel, Lampsilis, which feeds on the gills of fish in the larval stage of their development. Once they mature, they leave the fish as adult mollusc. Gaining entry into the host is not an easy task though, despite the fact that several hundred thousand larvae are released at once. This is especially the case in flowing water bodies such as streams, where they cannot lie on the substrate and wait to be taken up in the course of foraging. Female Lampsilis have evolved a special technique for delivering their offspring into a suitable host, however. Structures on the edge of the mantle are able to capture the