Q: Which species is the youngest on Earth?
A: Impossible to know for sure, but here is a candidate: the marbled crayfish, also known as Marmorkrebs.
It was discovered in aquariums in the mid 1990s, and has no known natural populations. It’s so unusual that if it was out there, it should have been noticed.
A major genetic difference between Marmorkrebs and their nearest relative is that Marmorkrebs is triploid: it has three sets of chromosomes, not two. The switch from two to three sets of chromosomes can occur in a single step, in one generation.
These give us some reason to believe it literally might not have existed long before the 1990s.
Which species is the youngest on Earth?
14 April 2017
A news article is reporting the second finding of Marmorkrebs in Japan, and, worryingly, it reports multiple individuals spread across two years, suggesting a population has been established. And it is on a completely different (and more southern) island than previously. Based on modelling work I helped co-author a few years ago (Faulkes et al. 2012), that region is high quality habitat for Marmorkrebs (see Figure 5 in particular).
The map of Marmorkrebs introductions has been updated, although I suspect the crayfish were not found anywhere near so close to the mouth of the river.
Faulkes Z, Feria TP, Muñoz J. 2012. Do Marmorkrebs, Procambarus fallax f. virginalis, threaten freshwater Japanese ecosystems? Aquatic Biosystems 8: 13. http://dx.doi.org/10.1186/2046-9063-8-13
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