Volume 5, Issue 4
published December 2010
Contents | |
Research articles |
-
|
Bella S. Galil, Lisa-Ann Gershwin, Jacob Douek and Baruch Rinkevich
Marivagia stellata gen. et sp. nov. (Scyphozoa: Rhizostomeae: Cepheidae), another alien jellyfish from the Mediterranean coast of Israel
(pp 331-340)
|
|
Two specimens of an unknown jellyfish species were collected in Bat Gallim and Beit Yannai, on the Mediterranean
coast of Israel, in June and July 2010. Morphological characters identified it as a cepheid (Cnidaria, Scyphozoa,
Rhizostomeae). However, the specimens showed remarkable differences from other cepheid genera;
unlike Cephea and Netrostoma it lacks warts or knobs centrally on the exumbrella and filaments
on oral disk and between mouths, and it differs from Cotylorhiza in its proximally loose anastomosed
radial canals and in lacking stalked suckers and filaments on the moutharms. We thus describe it herein as
Marivagia stellata gen. et sp. nov. We also present the results of our molecular analysis based
on mitochondrial cytochrome oxidase I (COI), which support its placement among the Cepheidae and provide
its barcode signature. This new find is the fourth introduced scyphozoan species recorded in the Mediterranean.
The presence of a sexually mature specimen collected as far back as 2006, and the occurrence of the species
this summer at sites nearly 90 kms apart, indicate the existence of an established population.
|
|
-
|
Mads Solgaard Thomsen
Experimental evidence for positive effects of invasive seaweed on native invertebrates via habitat-formation in a seagrass bed
(pp 341-346)
|
|
Relatively few studies have aimed to test if invasive species have positive effects on native species,
for example via formation of habitat or by amelioration of environmental stress-conditions. The red macroalga
Gracilaria vermiculophylla, from the West Pacific, is invading estuarine mudflat and seagrass habitats
along East Pacific and East and West Atlantic coastlines. I tested if low (55-110 g WW m-2)
and high (220-440 g WW m-2) densities of G. vermiculophylla have positive or negative effects
on the macroinvertebrates (> 2 mm) that inhabit Zostera marina seagrass beds. The experiment was conducted
over 34 days at both 0.5 and 2 m depth at Snaptun Harbor, Denmark. I found positive effects of Gracilaria
on most invertebrates, with statistically significant results for “all invertebrates”, “gastropods”,
and “bivalves”, and a near-significant result for “crustaceans”. Both quantitative and qualitative
habitat-resource models may explain these positive effects; i.e. “more habitats” exist in the presence
of Gracilaria and/or the “habitat differs” between Gracilaria and Zostera vegetation.
Future studies should test these two general explanatory models and quantify (a) if density thresholds
exists were effects shift from positive to negative, (b) specific mechanism whereby positive effects occur,
(c) if Gracilaria provide a novel or substitute drift algal habitat, and (d) the larger-scale ecosystem
implications of this invasion.
|
|
-
|
Hans Ulrik Riisgård, Coralie Barth-Jensen and Caroline V. Madsen
High abundance of the jellyfish Aurelia aurita excludes the invasive ctenophore Mnemiopsis leidyi to establish in a shallow cove (Kertinge Nor, Denmark)
(pp 347-356)
|
|
The population dynamics of the invasive ctenophore Mnemiopsis leidyi, which showed mass occurrence
in Kerteminde Fjord (Denmark) for the first time in 2007, and the indigenous common jellyfish, Aurelia aurita,
was followed in the fjord system Kerteminde Fjord/Kertinge Nor during late 2008 and 2009. The population density of
A. aurita was always highest in Kertinge Nor while the density of M. leidyi was always highest in
Kerteminde Fjord, indicating recruitment of the ctenophore from the adjacent sea (Great Belt). In the shallow
cove of Kertinge Nor, the first A. aurita ephyrae appeared in March, by the end of May the medusae had
obtained their maximum umbrella diameter of only 30 mm due to food limitation, and the estimated half-life
of zooplankton was very low, <1 day from May to September 2009. The high predation impact explains why the holopelagic
ctenophore, which presumably survives the winter in the adjacent open sea, is likely to be outcompeted in Kertinge Nor
where the polyp stage of A. aurita every spring ensures a very large population of very small medusae.
The population density of jellyfish, in Kertinge Nor, during the summer period is dependent on the extend of flush-out
due to density-driven water exchange. A survey of data obtained every year in August since 1991 indicates that
the unusually high population density (36 ± 34 ind. m-3) and the small umbrella diameter (56 ± 5 mm) of A. aurita
have remained unchanged during the last 20 years, and further, that a relatively high population density of jellyfish
in certain years is correlated with a relatively small mean umbrella diameter.
|
|
-
|
Caroline V. Madsen and Hans Ulrik Riisgård
Ingestion-rate method for measurement of clearance rates of the ctenophore Mnemiopsis leidyi
(pp 357-361)
|
|
Clearance rates of small (about 12 mm oral-aboral length) Mnemiopsis leidyi were measured by means
of the ingestion-rate method in order to compare with rates estimated from an equation (derived from
Decker et al. 2004) used in previous studies. About 3 times higher clearance rates measured in the present
study indicate that the estimated predation impact of small ctenophores may previously have been considerably
underestimated. The prey-capture efficiency measured in M. leidyi depends on type and size of prey organism,
and the study indicates that the clearance of slow swimming prey (e.g. mussel larvae) captured by auricular flow
fields is higher than the clearance of fast swimming/jumping prey (copepods) captured by the lobes.
The ingestion-rate method presented may open up not only more precise measurements of clearance rates,
but also provide for digestion rates of M. leidyi offered different types of prey organisms.
|
|
-
|
Kirsty F. Smith, Patrick L. Cahill and Andrew E. Fidler
First record of the solitary ascidian Ciona savignyi Herdman, 1882 in the Southern Hemisphere
(pp 363-368)
|
|
This report documents the first recording of the solitary ascidian Ciona savignyi in the Southern
Hemisphere. Adult tunicate specimens were collected from the Nelson city marina (South Island, New Zealand)
in April 2010. Both mitochondrial cytochrome oxidase I (COI) gene sequences and morphological characters
were used to identify the tunicates as C. savignyi – the first report of this species in New Zealand and
the Southern Hemisphere. This study highlights the power of molecular methods for invasive species
identification and New Zealand’s need for an extensive, systematic molecular inventory of its existing marine
invertebrate biodiversity.
|
|
-
|
Gretchen Lambert, Noa Shenkar and Billie J. Swalla
First Pacific record of the north Atlantic ascidian Molgula citrina – bioinvasion or circumpolar distribution?
(pp 369-378)
|
|
The small brooding ascidian Molgula citrina Alder and Hancock, 1848 has long been known as a common
inhabitant of shallow waters on both sides of the north Atlantic on subtidal natural hard substrates and
also as a fouler of floating docks. There are published records from the White Sea (NW Russia), but none
from the north Pacific. In May and August 2008, a number of adult brooding Molgula sp. specimens
were collected from floating docks at the small fishing village of Seldovia on the Kenai Peninsula at Kachemak Bay,
Alaska. Morphologically these individuals exactly match Atlantic specimens of Molgula citrina in all
characters that were examined. The unique constellation of characters for this species differentiates it from
all other Molgula species, as noted by Van Name (1945). In addition, the full-length 18S and 28S rDNA
sequences are identical for both the Alaska specimens and New England M. citrina. Is this a new invasion,
or is M. citrina a northern circumpolar species that was somehow overlooked? If this new record indicates
a natural distribution, why has it not been collected before? If it is a recent introduction, it is unlikely
that M. citrina, an inhabitant of cold waters, could survive in sea chests of ships from the N. Atlantic
arriving in Alaska via the Panama Canal, but the intriguing idea exists of transport from Atlantic to Pacific
through the Northwest or Northeast Passages. As global warming diminishes the ice cover in this region,
more and more ships are traversing the Northwest Passage across northern Canada as well as the NE Passage
across northern Russia, representing significant new routes for anthropogenic transport of marine species.
The tadpoles of this small brooder are retained for some time after hatching, resulting in an extremely short
free larval life, but could survive as metamorphosed juveniles attached in sea chests or free-floating in ballast
water. They have a wide temperature tolerance and once they metamorphose can live free-floating in sea water
for some time. They become very sticky and will ultimately stick to whatever they contact. Thus they could
conceivably live for many generations in sea chests and sustain a viable population from which to invade
new habitats.
|
|
-
|
Thomas G. Horvath and Lori Crane
Hydrodynamic forces affect larval zebra mussel (Dreissena polymorpha) mortality in a laboratory setting
(pp 379-385)
|
|
Mortality of zebra mussel, Dreissena polymorpha, larvae was quantified in a laboratory experiment
that was designed to assess the role played by both intensity and duration of the exposure to hydrodynamic forces.
Larvae were collected in a plankton net and distributed in 100-ml aliquots to 125-ml Erlenmeyer flasks.
The flasks were spun on an orbital shaker at different speeds, 100 rpm and 400 rpm, to change the intensity
of the hydrodynamic forces experienced by larvae inside the flasks. Actual shear forces were not quantified.
A parallel set of control flasks were not spun. Flasks were spun for 1, 24 and 48 hours. Mortality was highest
in the 400 rpm, 48-h trial. Both intensity and duration were highly significant variables in the ANOVA model
(p<0.001). However, the interaction term was also highly significant (p<0.001). Larval mortality was
significantly higher in the treatments than in the non-spun flasks in only the 400 rpm, 24-h and 400 rpm,
48-h trials. Thus, longer duration of exposure to high intensity hydrodynamic forces increases larval mortality.
These results help explain natural recruitment patterns of zebra mussels in natural streams and may be
of interest to management and conservation efforts.
|
|
-
|
Marcus K. Drotz, Matz Berggren, Stefan Lundberg, Kennet Lundin and Ted von Proschwitz
Invasion routes, current and historical distribution of the Chinese mitten crab
(Eriocheir sinensis H. Milne Edwards, 1853) in Sweden
(pp 387-396)
|
|
Single specimens of the Chinese mitten crab, Eriocheir sinensis H. Milne Edwards, 1853, have been regularly
reported along the western and eastern coasts of Sweden since the 1930´s. The crab has most likely been brought
from overseas via the transfer of ship’s ballast water or secondarily introduced from its key European distribution
areas. Since 2001 a sharp increase in the occurrence of the mitten crab has been noticed in Swedish inland waters,
but the dispersal routes and distribution of the species into Sweden remain poorly known. Here we document
the current and historical distribution of the Chinese mitten crab in Sweden and assess possible invasion routes.
A special focus is put on the historical occurrence of crabs in Lake Vänern, which empties into
the Skagerrak/North Sea and Lake Mälaren, which connects to the Baltic Sea. The existing time series available
for the mitten crab from the two lakes shows a large variation in dispersal pattern between different areas within
each lake. In order to detect and monitor outbreaks of the mitten crab in Sweden, an internet based reporting
system was created in 2007. Museum collections and reports from the general public throughout Sweden were
compared with the known occurrence of mitten crabs in Lake Vänern and Lake Mälaren. During the study,
the web-based reporting system was not advertised and the general public did not get paid for reporting
the information. Population densities of the crab occurred “in peaks” and unevenly over the last decade in both
lakes, suggesting a pulse invasion instead of a constant supply by migration. Significant difference in male
and female occurrence together with few transport possibilities between lakes suggests different invasion routes
for the crabs. Reports from the general public throughout Sweden coincide with the observations from local
fishermen in Lake Mälaren and Lake Vänern. Data on occurrence and abundance are discussed in relation
to a potential reproduction area on the western coast of Sweden.
|
|
-
|
Peer Martin, Hong Shen, Gert Füllner and Gerhard Scholtz
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
(pp 397-403)
|
|
A cambarid specimen was collected in a brook in Saxony (south-east Germany). Preliminary morphological inspection
identified it as the parthenogenetic Marmorkrebs (Decapoda, Astacida, Cambaridae). However, this individual showed
some striking morphological differences compared to specimens of our laboratory Marmorkrebs culture. Hence, we
conducted a molecular analysis based on two mitochondrial genes, COI and 12S, to check its identity. The results
of the genetic study verified the initial assumption of a Marmorkrebs identity for the Saxon specimen. Thus,
in addition to the two indigenous species, the new find is the fourth recorded introduced crayfish species in this
area. However, a search for further Marmorkrebs specimens at the same site was not successful. Most published
records of Marmorkrebs in European waters concern just single individuals and an established population has
so far not been observed. This stands in contrast to other recently introduced cambarid species. Thus, we
critically discuss the potential of the Marmorkrebs to spread within Europe. The major obstacle may be that
the temperature necessary for optimal development and reproduction of the Marmorkrebs is significantly higher
than that found in most European waters. However, given globally increasing temperatures, this might change
in the future.
|
|
-
|
Christoph Chucholl and Michael Pfeiffer
First evidence for an established Marmorkrebs (Decapoda, Astacida, Cambaridae) population in Southwestern Germany, in syntopic occurrence with Orconectes limosus (Rafinesque, 1817)
(pp 405-412)
|
|
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.
|
|
-
|
Gordon H. Copp, A. Serhan Tarkan, Michael J. Godard, Nathan Edmonds and Keith J. Wesley
Preliminary assessment of feral goldfish impacts on ponds, with particular reference to native crucian carp
(pp 413-422)
|
|
Introductions of an Asian cyprinid, goldfish Carassius auratus, are known to pose a genetic
threat to crucian carp Carassius carassius, which is native to northern parts of central and
western Europe, including southeast England. However, there are no known studies in Europe of goldfish
impacts on crucian carp growth and life-history traits, nor on the recipient ecosystems. The present
study is the first such attempt, and compares the plants, invertebrates and fish biology (growth,
condition, reproduction) in six ponds, two containing crucian carp only (allopatry), two containing
goldfish only (allopatry), and two with both species (sympatry). Feral goldfish growth was greatest
in sympatry with native crucian carp, whereas crucian carp growth was similar regardless of goldfish
presence or absence. However, body condition (LK) and relative fecundity (per unit of body
weight) of crucian carp was greatest in sympatry with feral goldfish. LK increased significantly
with increasing water conductivity in goldfish but not in crucian carp, and LK was not related
to pond invertebrate densities in either fish species. Differences in the plant and aquatic invertebrate
communities observed in the study ponds could not be attributed to the introduction and establishment
of goldfish, however non-native plant and invertebrate species were observed only in ponds containing
goldfish. Differences in growth and condition between the two Carassius species does not appear
to be due to differences in available food, so elevated somatic growth and reproductive output in
crucian carp and faster growth in goldfish in sympatry may be due to non-dietary competitive
interactions. The present preliminary study highlights the difficulties of assessing ‘real world’
impacts of non-native species on native species and ecosystems as well as the need for further
study of feral goldfish impacts on European pond ecosystems in general and on native congener
crucian carp in particular.
|
|
-
|
Suebpong Sa-nguansil and Vachira Lheknim
The occurrence and reproductive status of Yucatan molly Poecilia velifera (Regan, 1914)
(Poeciliidae; Cyprinodontiformes): an alien fish invading the Songkhla Lake Basin, Thailand
(pp 423-430)
|
|
A non-native fish, the Yucatan molly Poecilia velifera (Regan, 1914), has recently become established
in the Songkhla Lake Basin, south Thailand. Based on our field surveys in December 2007, we conclude that
this species is present only in the Haad-kaew Lagoon and the southernmost part of the Songkhla Lagoon,
the Thale Sap Songkhla. We sampled P. velifera monthly for 13 months (January 2007-January 2008),
using beach seine and cast net, to obtain information on its population structure, morphology and reproduction.
It was found that male and female P. velifera became sexually mature at 16.8 and 17.1 mm standard length,
respectively. The overall sex ratio of males to females was 1.0:1.8. However, the proportion of males was less
within specimens belonging to larger size classes. P. velifera reproduced continuously throughout the year
but with two peaks, one in March-May and another in August-December.
|
Short communications |
-
|
Sander Wijnhoven and Angela Dekker
Records of a new alien polychaete worm species, Marphysa sanguinea (Montagu, 1815) (Eunicidae) in the Eastern Scheldt, the Netherlands
(pp 431-436)
|
|
Recently, four observations of Marphysa sanguinea (Montagu, 1815) were made in the Eastern Scheldt
in the southwestern part of the Netherlands. This is remarkable as this alien species has been found only
once in the Netherlands, in 1990 at the North Sea coast. It seems that this large polychaete species,
that previously was noted to have a northern distribution limit in the southern North Sea (English southern
coast and the French west coast), has established a population in a semi-enclosed Dutch tidal bay. The species
may have reached the region via shellfish transport associated with the numerous aquaculture sites in the region.
Consequences of the settlement of this large at least partially predatory polychaete species,
for the macrozoobenthic communities in this region are unclear. Species of the genus Marphysa are found
to be successful in a variety of environments all over the world. So far, no other species of the genus
Marphysa has been recorded as present in the Netherlands.
|
|
-
|
Galia Pasternak and Bella S. Galil
Occurrence of the alien sea hare Aplysia dactylomela Rang, 1828 (Opisthobranchia, Aplysiidae) in Israel
(pp 437-440)
|
|
The alien sea hare Aplysia dactylomela, established in the central and eastern Mediterranean,
is recorded for the first time from Israel on the basis of two specimens photographed at Akhziv,
northern Israel. A map of its spread in the Mediterranean Sea is supplied. The species is able
to sequester secondary metabolites from its algal diet, mobilize them into its skin and digestive
gland, and convert photosynthetic pigments into chemical deterrents. The role of anti-predatory
defense in the invasion success of A. dactylomela remains to be studied.
|
|
-
|
Calum MacNeil, Dirk Platvoet, Jaimie T. A. Dick, Nina Fielding, Andrew Constable, Nathan Hall, David Aldridge, Trevor Renals and Mark Diamond
The Ponto-Caspian ‘killer shrimp’, Dikerogammarus villosus (Sowinsky, 1894), invades the British Isles
(pp 441-445)
|
|
The Ponto-Caspian amphipod Dikerogammarus villosus was found both in the margins and open water areas
of Grafham Water, a large reservoir in Cambridgeshire, U.K., in September 2010. Both adults and juveniles
were present in large numbers and were most frequent in the boulder/cobble areas dominating the margins
of the reservoir. Precopula pairs were also evident, as were egg bearing females.
|
|
-
|
Zen Faulkes
The spread of the parthenogenetic marbled crayfish, Marmorkrebs (Procambarus sp.), in the North American pet trade
(pp 447-450)
|
|
The parthenogenetic marbled crayfish Marmorkrebs was discovered in the pet trade in Europe in the 1990s.
Since then, its distribution through the pet trade has spread from Europe to other continents, including
North America. North American pet owners were surveyed online with the aims of trying to track when Marmorkrebs
entered the North American pet trade, the ways in which it spread through the pet trade, and how widely
distributed Marmorkrebs are throughout the continent. Marmorkrebs have been in the North American pet trade
since at least 2004, with the number of people increasing every year. While many Marmorkrebs are sold through
online sources, face-to-face personal contacts account for almost as many acquisitions. The increasing spread
of Marmorkrebs through the pet trade increases the probability that Marmorkrebs will be released into North
American ecosystems.
|
|