This is bad news, if I am reading these new stories right. (I don’t read German, so I am working from a Google translation of the news story. Translation by a person would be welcomed!)
It appears that crayfish were found, in large numbers, walking out of this pond. The reasons were unknown, but overcrowding was given as a possible explanation, seen by the new story as likely given the rapid reproduction of Marmorkrebs.
Martin et al. (in press) pointed out that until now, only single Marmorkrebs have been found in Europe, never a reproducing population. This gave a glimmer of hope that Marmorkrebs might not be able to establish themselves as an invasive species in Europe. That hope glimmers a lot less brightly if the animals are walking out of water because of overcrowding, since that indicates an actively reproducing and expanding population.
Worse, both stories report astonishing sizes of the animals. The first report puts some individuals found in Klepzig at 20 cm long; the later, at 15 cm. If so, those are record-shattering sizes for Marmorkrebs. Vogt (in press) reported:
The largest specimen of my laboratory colony had reached a length of 8.8 cm... Under tropical outdoor conditions the maximum length measured was 10.7 cm (Jones et al. 2009)
50-100% larger than the largest size recorded previously is worth investigating. It suggests that the Klepzig population has been there a long time (since animals don’t grow to that size in a few weeks), and that the conditions are highly conducive to the animals.
The new article emphasizes the potential for Marmorkrebs to carry crayfish plague, which is an entirely legitimate concern. To the best of my knowledge, however, Marmorkrebs have not yet been shown to carry the pathogen. Someone needs to try infecting Marmorkrebs to see how they fare against the disease, and how contagious they are compared to other North American species.
The map of Marmorkrebs introductions has been updated to include Klepzig.
Jones JPG, Rasamy JR, Harvey A, Toon A, Oidtmann B, Randrianarison MH, Raminosoa N, Ravoahangimalala OR. 2009. The perfect invader: a parthenogenic crayfish poses a new threat to Madagascar’s freshwater biodiversity. Biological Invasions 11(6): 1475-1482.
Martin P, Shen H, Füller G, Scholtz G. The first record of the parthenogenetic Marmorkrebs (Decapoda, Astacida, Cambaridae) in the wild in Saxony (Germany) raises the question of its actual threat to European freshwater ecosystems. Aquatic Invasions: In press.
Vogt G. Suitability of the clonal marbled crayfish for biogerontological research: A review and perspective, with remarks on some further crustaceans. Biogerontology: In press.