New Species of Asexual Crayfish Spreads Throughout World

Fish Wars Episode II: Attack of the (Crayfish) Clones.

Griffin Sonnemann-Creed, Columnist

The crayfish, also known as a crawdad, crawfish, yabby, or “tasty tiny lobster,” is a type of freshwater crustacean prominent throughout many of the world’s river ecosystems. They are an integral part of the local systems, often feeding on tiny fish, plant matter, and even other crayfish. However, a new species, dubbed the Marbled crayfish or Marmorkrebs, has begun to spread beyond its initial home in the aquarium.

The marmorkrebs is unique amongst crayfish for one reason– it can reproduce asexually. Only female marmorkrebs exist, with males simply never having been born. The females, however, make up for this by having two chromosomes in each sex cell. The result? They can clone themselves. Genetically identical, but separate, living crayfish.

The massive population explosion of these crayfish first started in Germany. In the mid 1990’s, German aquarium owners began to buy what were labelled “Texas crayfish.” The species rapidly expanded from there. Females would lay hundreds of eggs at once. By the time the owners noticed, it was often too late. Hundreds of tiny crayfish were already swimming in the waters, with more certain to come. So what did the owners do? Dump them into the local bodies of water to get rid of them.

The introduction of the marmorkrebs to local ecosystems is what truly sparked their expansion. Notably hardy and adaptable, some crayfish were even able to walk hundreds of meters to reach lakes or rivers. Thus, they began to spread. First, it was Germany. Then it was France. Now, they inhabit almost all of Europe – spreading to all of this in under 25 years. But their expansion doesn’t stop there. Marmorkrebs have already been sighted in Africa, off the coast of Madagascar.

Despite their extremely recent introduction to the world’s ecosystems, marmorkrebs are already having a noticeable effect on the local aquatic populations. Local species of crayfish are being outcompeted and outmaneuvered by the marmorkrebs, while other species of fish are finding many of their traditional food sources, such as the local flora, have been eaten by the marmorkrebs. However, the inverse has also occurred. The massive populations of crayfish have also provided a ready food source of other fish species, sparking overpopulation.

However, the natural adaptability and spread of these crayfish may be their downfall. Due to their genetic similarity, with every crayfish the exact same as the next, just one disease or parasite could mean the downfall of the entire wild population. Thus, it is likely that within a few years, they could disappear as rapidly as they have appeared. Not even cloning can save you from a microscopic speck, it seems.