Do tumors use epigenetics to adapt to diverse environments? This new crayfish species may hold some answers
The Marmokreb (German, which translates into English as ‘marbled crayfish’) is an enigmatic crayfish species that was first discovered in the German pet trade in the mid-1990s, when aquarium enthusiasts reported an all-female crayfish species that reproduces without males. Clones of this species have now spread throughout Europe, gotten as far as Japan and begun invading streams of Madagascar. Genomic evaluation has now confirmed that these crayfish around the world are indeed clones. Because they are parthenogenic and reprooduce asexually, they produce a female-only population with viable eggs. In parthenogenic animals, females never get rid of one of the sets of chromosomes. The egg ends up with 2 sets, both from the mother and from a genetic standpoint are clones of the mother.
Marmokrebs have 3 sets of chromosomes (triploid) rather than 2 (Gutekunst et al). This likely came about when a female produced an egg with 2 sets of chromosomes and then had it fertilized by a male adding a third. This is almost certainly what happened here, as the Marmokreb has 2 sets of identical chromosomes and a 3rd more distantly related. The female offspring then develop the ability to reproduce itself. How it gains the ability to reproduce through parthenogenesis is still a mystery. Loss or mutation of sexual-reproduction genes could underlie the transition.
Komodo dragons as well as some snakes (e.g. Boa) and lizards are in some circumstances parthenogenic. However, most are only half clones and not full clones as is the Marmokrebs (the new species is aptly named Procambarus virginalis). When there are 3 copies of each gene in one environment, one gene may be expressed while another is not. Researchers hope that studying these clones may help inform them on how tumors adapt, possibly using epigenetics.
There are a lot of clear advantages to being a clone. Marbled crayfish produce nothing but fertile offspring, allowing their populations to explode. “Asexuality is a fantastic short-term strategy.” said Dr. Abraham Tucker of Southern Arkansas University. The marbled crayfish offers scientists a chance to watch this drama play out practically from the beginning. It’s doing extremely well for the first 2 decades but sooner or later its fortune may well turn. “Maybe they’ll just survive for 100,000 years, Dr. Lyko of the German Cancer Research Center speculated. “That would be a long time for me personally, but in evolution it would just be a blip on the radar”.
Regardless of this great science, the good people of southern Louisiana, where eating crayfish (crawfish) is a way of life might only have one additional concern. CHER,DO THEY TASTE GOOD???