First evidence for an established Marmorkrebs (Decapoda, Astacida, Cambaridae) population in Southwestern Germany, in syntopic occurrence with Orconectes limosus (Rafinesque, 1817)

Christoph Chucholl,Michael Pfeiffer

doi:10.3391/ai.2010.5.4.10

Abstract

Marmorkrebs are one of 12 currently known non-indigenous crayfish species (NICS) to be found in Central European waters. It is unique in the manner that there exist only females which reproduce parthenogenetically, i.e. eggs develop unfertilized and all offspring are genetically identical. Marmorkrebs have been first discovered in the German aquarium trade in the mid 1990s and became a very common pet species since then. Here, we present first evidence for a well established Marmorkrebs population in a small lake in the Upper Rhine catchment near Freiburg (Germany). The population occurs syntopically with Orconectes limosus, another NICS which invaded the Rhine system about 50 years ago. Morphometric and ovary weight measurements were taken from 12 Marmorkrebs specimens that were captured on July 3, 2010. The rostrum spination was pronounced and resembled the one found on a free-living individual captured in Saxony (Germany). Ovary development stages (Gonadosomatic Index) were heterogeneous and single berried females were found from early June to late July, which might indicate an asynchronous breeding habit. The relative abundance and distribution of both crayfish species were assessed by visual counts at nighttime at two occasions. Both species attained a comparable, moderate density throughout the lake margin. The Marmorkrebs was the prevalent species on shallow, swampy habitat patches, which are presumably similar to its natural prime habitats. The successful establishment of Marmorkrebs despite a pre-existing O. limosus population, stresses the competitive ability of Marmorkrebs. In addition to the recently suggested hypothesis that Marmorkrebs might be temperature limited in most parts of Europe, we feel that it is also necessary to consider its probable natural prime habitats and life cycle: Marmorkrebs are presumably able to colonize summer-warm, lentic habitats in most parts of Central Europe.

Highlights

Crayfish (Astacida) are the largest mobile freshwater invertebrates and are considered as key members of littoral communities
The Marmorkrebs was the prevalent species on shallow, swampy habitat patches, which are presumably similar to its natural prime habitats
It is unique in the manner that it is the only known decapod crustacean that reproduces by parthenogenesis (Scholtz et al 2003; Martin et al 2007; Vogt 2008): there exist only females, which lay unfertilized eggs and all offspring are genetically identical

Summary

Introduction

Crayfish (Astacida) are the largest mobile freshwater invertebrates and are considered as key members of littoral communities. They attain frequently a high biomass and interact with multiple trophic levels due to their omnivorous feeding habits and non-trophic activities, e.g. burrowing and bioturbation (Momot 1995; Nyström 2002). The Marmorkrebs (`marbled crayfish) is a medium sized crayfish species of unknown origin and enigmatic phylogenetic position. It was first discovered in the German pet trade in the mid 1990s and became a very popular pet species since . Procambarus fallax occurs in southern Georgia and Florida and it is reasonable to assume that the Marmorkrebs originates from the southeastern United States, an indigenous population has never been reported

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