Welcome
to Exploring Rare Adaptations! As the title suggests, I will try to understand why
different animals have the adaptations that they do. If you are curious about
any strange adaptation an animal has and want me to investigate it for you let
me know in the comments.
Today, I
thought we would look at Neocapritemas
taracua which is a species of termites that is capable of exploding and releasing
a toxic substance. The older workers in a colony have a higher toxicity level
than younger workers and are therefore more likely explode. The toxicity level
of the termites is determined by a blue crystal which is embedded in the
termite. As a worker ages the crystal increases in size. The crystals are
produced by specialized glands called “crystal glands” which are located under
the epidermal cell layer and in the anterior portion of the pouch (Šobotník et. al., 2014).
Is there
another reason that older workers are more toxic than younger workers?
Over time the mandibles of the workers wear out and cannot be renewed through moulting
(Šobotník et
al., 2012). This
suggests that a form of kin selection may be occurring in this population. Kin
selection is selection affected by how related individuals are to each other.
Kin selection can also result in altruism which is an action that directly
decreases the fitness of the one performing the actor and benefiting the
recipient (Foster et al., 2005). In this case the older workers will protect
the younger workers by attacking a predator. By provoking the predator the
older worker’s pouch that contains the toxic substance will likely be ruptured.
The toxic substance will cover the predator with a sticky incapacitating
substance (Šobotník et al., 2014). The younger
worker will be protected with the older workers suicidal defence.
Here’s a
short video of how the termites will defend their colonies.
References:
Foster, KR,
Wenseleers, T, & Ratnieks, FLW 2006, ‘Kin selection is the key to altruism’,
Ecology and Evolution, vol. 21, no.
2, pp. 57-60, viewed 10 March 2016, doi:10.1016/j.tree.2005.11.020.
Šobotník, J,
Bourguignon, T, Hanus, R, Demianová, Z, Pytelková, J, Mareš, M, Foltynová, P, Preisler, J, Krasulová, J, &
Roisin, Y 2012, ‘Explosive backpacks in old termite workers’, Science, vol. 337, no. 6093, pp. 436,
viewed 10 March 2016, doi:10.1126/science.1219129.
Šobotník, J,
Kutalová, K, Vytisková, B, Roisin, Y, & Bourguignon, T 2014, ‘Age-dependent
changes in ultrastructure of the defensive glands of Neocapritermes taracua workers’, Arthropod Structure & Development, vol. 43, no. 3, pp. 205-210,
viewed 10 March 2016, doi:10.1016/j.asd.2014.02.003.
