Now You See Me, Now You Don't

Usually, mimicry is a permanent state (more so in vertebrates than invertebrates). But this is not the case for the bluestriped fangblenny (Plagiotremus rhinorhynchos) which can 'turn off' its mimetic appearance at will.

The fangblenny mimics the juvenile bluestreak cleaner wrasse (Labroides dimidiatus), which is characterised by an electric blue stripe on each side its black body. In its non-mimetic colouration, the fangblenny is orange or olive/brown and shoal with other reef fish - predominantly red-cheeked anthias (Pseudanthias huchti), purple anthias (Pseudanthias tuka) and shoulderspot wrasses (Leptojulis cyanopleura) (Cote and Cheney, 2005).

Figure 1: a) mimetic bluestriped fangblenny b) juvenile bluestreak cleaner wrasse (model)

c) and d) orange and olive/brown forms of non-mimetic bluestriped fangblenny

In its mimetic form, the fangblenny can blend in with the harmless cleaner wrasse and ambush unsuspecting prey (an example of aggressive mimicry). In its non-mimetic form, the fangblenny also ambushes prey; however no disguise/deception is utilized in this instance.

- Cote, I. M. and Cheney, K. L. 2005, 'Choosing when to be a cleaner-fish', Nature, vol. 433, pp. 211.

- Figure 1: (Cote and Cheney, 2005), retrieved 09/04/14.

Introduction to Aggressive Mimicry

Aggressive mimicry is a form of mimicry in which predators deceive potential prey by making signals to (indirectly) influence prey behaviour (Jackson and Cross, 2013). Basically, aggressive mimicry is the opposite of Batesian Mimicry in the sense that the prey is being fooled, rather than the predator.

Much like other types of mimicry, aggressive mimicry can be expressed in many different ways. Predators might mimic the physical appearance of a harmless species to allow them to approach unsuspecting prey. An example of this is the Zone-Tailed Hawk (Buteo albonotatus) shown in Figure 1, which resembles the common Turkey Vulture (Cathartes aura) in plumage colour, shape and soaring behaviour. Zone-Tailed Hawks soar with groups of Turkey Vultures, but breaks formation to dive and catch prey. It is believed that the prey of the Hawk do not feel threatened by the Turkey Vultures and therefore by blending in with said Turkeys, the hawk has a better chance of catching prey (Willis, 1963).

Figure 1: A Zone-Tailed Hawk (Buteo albonotatus)

Alternatively, predators might lure prey by pretending to offer food, a mate, or something else that the prey species would want/need. This second type is much more interesting in my opinion, as the mimetic predators in question have adapted some amazing features and behaviours. One such example is the Assassin Bug (Stenolemus bituberus), which hunts spiders by pretending to be a meal stuck in the spider's web. It does this by plucking the silk of a spider's web in a way which sends a signal to the spider that there is prey in the web. Once the spider approaches to investigate, the Assassin Bug strikes (as shown in Figure 2)! What's even more amazing is that the Assassin Bug knows the difference between the characteristic vibrations of a prey and the characteristic vibrations of a falling leaf or another spider. Without this skill, the Assassin Bug wouldn't be able to catch spiders in the way that it does (Wignall and Taylor, 2011).

Figure 2: an illustration of an Assassin Bug (Stenolemus bituberus) tricking an unlucky spider

- Jackson, R. R. and Cross, F. R. 2013, 'A cognitive perspective on aggressive mimicry', Journal of Zoology, vol. 290, pp. 161-171.
- Wignall, A. E. and Taylor, P. W. 2011, 'Assassin bug uses aggressive mimicry to lure spider prey', Proceedings of the Royal Society, vol. 278, pp. 1427-1433.
- Willis, E. O. 1963, 'Is the Zone-Tailed Hawk a Mimic of the Turkey Vulture?', The Condor, vol. 65, no. 4, pp. 313-317.

- Figure 1: http://upload.wikimedia.org/wikipedia/commons/8/8d/ZonetailedHawk2.jpg, Photographer: Stolz, G. M., retrieved 01/04/14
- Figure 2: http://images.smh.com.au/2010/10/27/2011409/Wilcox_bug-420x0.jpg Author: Cathy Wilcox, retrieved 01/04/14