What doesn’t kill you makes you stronger: detoxification ability as mechanism of honesty in a sexually selected signal

G-Santoyo, Isaac; Gonzalez-Tokman, Daniel; Tapia-Rodríguez, Miguel; Cordoba, Alex

Mantid (Stagmomantis sp.) eating a mature male rubyspot (Hetaerina americana). The red wing spot is a sexually selected trait evolved by male-male competition. The pigments behind this conspicuous and costly red colouration are ommochromes, produced from the toxic tryptophan metabolite 3-HydroxyKinurenine. Hence, only males capable of storing large toxic amounts, are able to produce a large red spot. This mechanism is entirely new for colourful and other sexual traits, elucidating a mechanism for the evolution of honest indicators of quality that could have arisen due to natural selection.
Mantid (Stagmomantis sp.) eating a mature male rubyspot (Hetaerina americana). The red wing spot is a sexually selected trait evolved by male-male competition. The pigments behind this conspicuous and costly red colouration are ommochromes, produced from the toxic tryptophan metabolite 3-HydroxyKinurenine. Hence, only males capable of storing large toxic amounts, are able to produce a large red spot. This mechanism is entirely new for colourful and other sexual traits, elucidating a mechanism for the evolution of honest indicators of quality that could have arisen due to natural selection.

What is the role of colourful traits in animals? Quite often these traits are used by adult males to assess each other when competing over mating territories. This function is linked to a second question of what such colours are made of. We used to know that these colourful traits contained key dietetic elements also used for the animal’s development and survival. However, food can also come with toxic compounds. One untested idea is that rather than discarding these harmful elements, animals integrate them to construct their colourful traits. We tested this idea using the American rubyspot damselfly whose adult males bear a red wing spot that communicates the ability to fight for and defend a mating territory against other males. We determined that the red spot is generated by ommochrome pigments derived from the toxic tryptophan metabolite, 3-hydroxy-kynurenine (3-Hk). Males treated with 3-Hk ended up with more ommochromes than control males but had a similar survival, suggesting that the allocation of ommochrome to the wing counteracts the 3-Hk toxicity. This implies that colourful traits may work to store toxic compounds, a hypothesis we have called  “detoxifying ability signalling”. In this sense, only males capable of storing large toxic amounts, are able to produce a large red spot. This mechanism is entirely new for colourful and other sexual traits.

Read the article in full here.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s