23 research outputs found
Population ecology of an alien “warm water” crayfish (
Procambarus clarkii is one of the worst invasive and best-studied crayfish species worldwide, but its life history at higher latitudes is poorly understood. In the present study, the population ecology of P. clarkii was studied for the first time within its northeastern range limit in Europe (southern Germany) for a two-year period, and the findings are used to discuss several life-history parameters across different latitudes of its current distribution range. The reproductive cycle was tracked using the gonadosomatic index and reproductive traits in females and the reproductive form in males. Life-history parameters were estimated using Von Bertalanffy’s growth function. Reproduction was univoltine and occurred from late summer to autumn. A small proportion of females carried eggs throughout the winter. This contrasts with the species’ multi-voltine life cycle at lower latitudes, with year-round breeding and several reproduction peaks per year. Growth was estimated to be slower than at lower latitudes, whereas longevity, mean lifetime and size increased. These changes in life history probably reflect a general phenomenon at higher latitudes and, thus, latitudinal clines. The presented findings provide evidence that P. clarkii is able to cope well with new cold habitats by modulating its life history
Understanding invasion success: life-history traits and feeding habits of the alien crayfish Orconectes immunis
In the present study, the life history and diet of the highly successful
North American invader Orconectes immunis was
assessed for the first time in its introduced European range. In 2007,
O. immunis population dynamics were monitored
in a typical backwater habitat using unbaited funnel traps, and its
life history was analysed using Von Bertalanffy’s growth function.
Juveniles hatched as early as March and may attain sexual maturity at
the end of their first summer. The adult population moulted up to four
times during the summer months, with the non-breeding form (II)
lasting for a remarkably short time period. The high growth rate of
O. immunis was combined with a short longevity,
which was estimated at 2.5 years. The fecundity ranged from 119 to 495
pleopodal eggs. The stomach contents were dominated by detritus,
followed by macroinvertebrates and macrophytes, and no ontogenetic
shift in diet was observed. The ability to prey on a wide array of
invertebrate taxa presumably supports the sustained high growth rate
of O. immunis. The presented data provide evidence
that O. immunis exhibits a strongly r-selected life
history and omnivorous feeding habits. These ecological properties
have often been linked to successful invaders and enhance the
invasiveness of O. immunis
First record of an introduced population of the southern lineage of white-clawed crayfish (
Elucidating the status of populations of endangered species of unclear origin may have
important implications for conservation management. In September 2013, a population of
white-clawed crayfish was discovered outside of the native range in a small artificial
lake in the River Neckar catchment in southwestern Germany. White-clawed crayfish comprise
two distinct lineages of yet unresolved taxonomic status, of which only the western
lineage (Austropotamobius pallipes s. str.) is native to Germany. To
clarify the taxonomic identity and origin of the newly discovered population, we evaluated
diagnostic morphological characters and sequences of two mitochondrial genes (for 16S rRNA
and cytochrome c oxidase subunit I) from two crayfish specimens. Both analyses
concordantly assigned the crayfish to the southern lineage (A.
‘italicus’), with the closest matching haplotypes originating from northwestern
Italy, southeastern Switzerland, and Lake Plansee in Austria, where an abundant introduced
population of this lineage is present. The artificial lake in Germany was reportedly
stocked with freshwater mussels from this Austrian lake. It thus appears likely that
A. ‘italicus’ was introduced intentionally or accidentally during the
process. Austropotamobius ‘italicus’ does not naturally occur north of
the Alps and thus represents a non-native taxon for Germany, a fact to be considered in
its management
Population ecology of endangered white-clawed crayfish ( Austropotamobius pallipes
Sound knowledge on distribution and ecology of imperiled species is an essential
prerequisite for effective conservation planning. Here, we report the distribution and
autecological traits of a newly discovered population of critically-endangered
white-clawed crayfish (Austropotamobius pallipes s. str.) in a small
river in southwestern Germany. Using an established crayfish survey protocol, we detected
white-clawed crayfish in a river stretch of 4.5 km, with an estimated abundance of
1.4 ± 0.2
indiv.·m-2. The sex ratio was even and
sexual maturity was attained at approximately 25 mm carapace length (CL).
Life-history traits, as assessed using Von Bertalanffy’s growth function, indicate a life
history most similar to populations in France, with longevity, asymptotic size, and growth
performance index being higher in males than in females (11 y, 46 mm CL,
and 2.8 and 9 y, 41 mm CL, and 2.7, for males and females, respectively).
Estimated fecundity ranged from 9 to 135 eggs·female-1 (mean: 90 ± 28). White-clawed crayfish were also found in lower reaches of small
tributary streams, of which one also featured endangered stone crayfish
(Austropotamobius torrentium). A syntopic occurrence of both species
was recorded for the first time within a short stretch. Implications for species
conservation are discussed
Population ecology of endangered white-clawed crayfish (Austropotamobius pallipes s. str.) in a small rhithral river in Germany
Sound knowledge on distribution and ecology of imperiled species is an essential
prerequisite for effective conservation planning. Here, we report the distribution and
autecological traits of a newly discovered population of critically-endangered
white-clawed crayfish (Austropotamobius pallipes s. str.) in a small
river in southwestern Germany. Using an established crayfish survey protocol, we detected
white-clawed crayfish in a river stretch of 4.5 km, with an estimated abundance of
1.4 ± 0.2
indiv.·m-2. The sex ratio was even and
sexual maturity was attained at approximately 25 mm carapace length (CL).
Life-history traits, as assessed using Von Bertalanffy’s growth function, indicate a life
history most similar to populations in France, with longevity, asymptotic size, and growth
performance index being higher in males than in females (11 y, 46 mm CL,
and 2.8 and 9 y, 41 mm CL, and 2.7, for males and females, respectively).
Estimated fecundity ranged from 9 to 135 eggs·female-1 (mean: 90 ± 28). White-clawed crayfish were also found in lower reaches of small
tributary streams, of which one also featured endangered stone crayfish
(Austropotamobius torrentium). A syntopic occurrence of both species
was recorded for the first time within a short stretch. Implications for species
conservation are discussed
Identification of exotic North American crayfish in Europe by DNA barcoding
Several alien crayfish of North American origin have become established in Europe in
recent decades, but their identification is often confusing. Our aim was to verify the
taxonomic status of their European populations by DNA barcoding. We sequenced the
cytochrome c oxidase subunit I (COI) gene fragment of individuals
representing all American crayfish known from European waters, and compared the results
with reference sequences from North America. Our results confirm the morphological
identification of Orconectes juvenilis from a population
in eastern France, and of the marbled crayfish (Marmorkrebs), i.e., a
parthenogenetic form of Procambarus fallax, from south-western Germany.
Sequences of most individuals of presumed Procambarus acutus from the
Netherlands were similar to American P. cf.
acutus, but one was divergent, closer to a sequence of a reference
individual of P. cf. zonangulus.
However, divergences among three American P. cf.
zonangulus samples were also high, comparable to interspecific
variation within cambarid species complexes. The divergence between O. immunis
from Europe and America also reached values corresponding to those observed among
distinct Orconectes species. Genetic variation in the American
range of these crayfish should therefore be further studied. Our study shows that DNA
barcoding is useful for the rapid and accurate identification of exotic crayfish in
Europe, and also provides insights into overall variation within these taxa