Volume 14, Issue 2 (2019)
published June 2019
Contents | |
Research articles |
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Stelios Katsanevakis, Konstantinos Tsirintanis, Dimitris Tsaparis, Dimitrios Doukas, Maria Sini, Fotini Athanassopoulou, Markos Nikolaos Κolygas, Dimitrios Tontis, Drosos Koutsoubas and Vasileios Bakopoulos
The cryptogenic parasite Haplosporidium pinnae invades the Aegean Sea and causes the collapse of Pinna nobilis populations
(pp 150–164)
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The cryptogenic parasite Haplosporidium pinnae has caused massive mortality of the protected endemic Mediterranean bivalve
Pinna nobilis in the western Mediterranean, since the autumn of 2016. Herein, we confirm the spread of the parasite
in the eastern Mediterranean, and report a massive mortality event, with > 93% average mortalities, in the coastal waters of Lesvos Island
(Greece, Aegean Sea). Histopathological study of collected specimens revealed the presence of a haplosporian-like protozoon in different
life cycle stages, mainly within the digestive gland of the infected Pinna nobilis, with many uni- and bi-nucleate parasite cells,
plasmodia and sporocysts in the wide lumen of digestive tubules causing the collapse of epithelial cells, and apparently low host haemocyte
reaction. The parasite was identified as H. pinnae by molecular methods (PCR amplification and sequencing of a part of small subunit
ribosomal DNA gene, and comparison with available records in Genbank). In many sites, 100% mortality was recorded, whereas in a single site
(among 13 surveyed sites) mortality was relatively low (36%), successful recruitment was observed and the parasite was not detected.
The latter observation stresses the importance of possible parasite-free refugia sites. We call for continuous monitoring of the spread
of the parasite and its impacts, and for urgent targeted research and actions to identify the factors affecting the parasite’s virulence,
investigate biotic and abiotic conditions that characterize refugia sites, and strictly protect the remaining P. nobilis populations
to increase the chances for the survival of the species. |
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Dan Minchin, Kęstutis Arbačiauskas, Darius Daunys, Elena Ezhova, Natalja Grudule, Jonne Kotta, Natalia Molchanova,
Sergej Olenin, Giedrė Višinskienė and Solvita Strake
Rapid expansion and facilitating factors of the Ponto-Caspian invader Dikerogammarus villosus within the eastern Baltic Sea
(pp 165–181)
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Dikerogammarus villosus, an amphipod of Ponto-Caspian origin, has recently and rapidly spread along Baltic coastal lagoons and estuaries.
By 2016 it had invaded Russian (Kaliningrad region), Lithuanian and Latvian waters, but was not recorded from Estonian waters. This species has
a discontinuous distribution suggesting a “jump” was involved in its dispersal. A classification tree and GLM analyses confirm such an observed
distribution pattern and suggest productivity of the environment, distance to the nearest lagoon/river mouth and distance to the nearest
port/marina were the most influential explanatory variables of its distribution. Our data indicates this rapid east and northward expansion
is very likely due to vessel transport, which would account for the “jump” dispersal. Other vectors facilitating further spread are almost
certainly acting at a local scale such as overland transportation of vessels, movements of diving gear, drifting mats of algae, macrophytes
and flotsam, as well as natural spread. We predict the “killer shrimp” will soon appear within the entire Gulf of Riga and the Gulf of Finland,
and also expand up-rivers of the eastern Baltic Sea. Following the species expansion, alterations and changes to macroinvertebrate assemblages
in invaded areas can be expected. |
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Noémie Deldicq, Elisabeth Alve, Magali Schweizer, Irina Polovodova Asteman, Silvia Hess, Kate Darling and Vincent M.P. Bouchet
History of the introduction of a species resembling the benthic foraminifera Nonionella stella in the Oslofjord (Norway): morphological, molecular and paleo-ecological evidences
(pp 182–205)
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Specimens resembling the benthic foraminifera Nonionella stella (Cushman and Moyer, 1930), a morphospecies originally described
from the San Pedro Basin, California, USA, were observed for the first time in the Oslofjord (Norway) in 2012. This study investigates
the Oslofjord Nonionella population in order to confirm its non-indigenous species (NIS) status and assess its introduction time.
Morphological characterisation based on SEM imaging complemented by molecular identification using small subunit (SSU) rDNA sequencing and
assessment of the recent past record (sediment core), were performed on material collected in the Oslofjord in 2016. Examination of the dead fauna
showed that specimens resembling N. stella only appeared recently in the Oslofjord, confirming the NIS status of this population. Moreover,
DNA results indicate that the Oslofjord specimens differ genetically from N. stella sampled in the Santa Barbara Basin (California USA).
Hence, we propose to use the name Nonionella sp. T1 for the specimens sampled in the Oslofjord for the time being. In the southern part
of the Skagerrak, specimens morphologically similar to Nonionella sp. T1 were reported as NIS in the Gullmar fjord (Sweden) in 2011 and
in the Skagerrak in 2015. Molecular data indicate that the two populations from Gullmar- and Oslofjords are identical, based on their SSU rDNA
sequences. In addition, analyses of foraminiferal dead assemblages suggest that the population from the Gullmar fjord settled prior to the Oslofjord
population, i.e. ~ 1985 and about 2010, respectively. This implies that Nonionella sp. T1 may have been transported from Sweden
to Norway by northward coastal currents. |
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Luciana Altvater, Maria Angélica Haddad and Ricardo Coutinho
Temporal patterns of recruitment and substrate use by the nonindigenous octocoral Stragulum bicolor van Ofwegen and Haddad, 2011
(Alcyonacea) in the Southern Brazilian Coast
(pp 206–220)
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The nonindigenous octocoral Stragulum bicolor was first registered in Brazil in the year 2000, in the estuarine regions of Paranaguá
and Cananéia (South/Southeast Brazil). Since then, this species has expanded its distribution along the Brazilian Coast, occurring mainly
in estuarine and port areas with high vessel traffic, on several types of artificial and natural substrates. In the present study, the recruitment
of S. bicolor was monitored for two years (May 2011 to March 2013), in two sites of the Paranaguá Bay (48°W; 25°S). To assess S. bicolor
recruitment, polyethylene plates were kept submersed for two months. After this period, the plates were collected for laboratory analyses and replaced
by new ones. The number of colonies, percentage cover, and type of substrate colonized were analyzed. On both sites, recruitment peaks were registered
during the warmer months. However, the number of recruits and percentage cover was higher in one of the sites, probably due to minor influence
of freshwater input from rivers and organic pollution from Paranaguá City. Moreover, although recruitment occurred on a greater number of substrates
at the island, in both locations the most colonized substrates were the polyethylene plate, the bryozoan Hippoporina indica, and barnacle shells.
Our data indicate that the population of S. bicolor is well established in the Paranaguá Bay and that it is a pioneer in habitat colonization
but is also able to recruit on occupied substrates. The ability of S. bicolor to overgrow other organisms may result in harmful effects
for native species. |
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Carol A. Simon, H. Helene van Niekerk, Ingo Burghardt, Harry A. ten Hove and Elena K. Kupriyanova
Not out of Africa: Spirobranchus kraussii (Baird, 1865) is not a global fouling and invasive serpulid of Indo-Pacific origin
(pp 221–249)
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A common intertidal belt-forming serpulid Spirobranchus kraussii (Baird, 1865) was originally described from South Africa and subsequently
reported from tropical and subtropical localities, mainly in the Indo-Pacific and Mediterranean Sea. It generally is assumed that the wide
distribution of the nominal species is a result of human-mediated translocations. Here we provide a detailed illustrated re-description of
S. kraussii based on the historical types and material freshly collected in South Africa from the type locality (Western Cape Province)
and Eastern part of the country (KwaZulu-Natal Province). The description is accompanied by DNA sequence data (cyt b and 18S).
Phylogenetic analysis of DNA sequences of specimens collected in South Africa, as well as farther afield in Australia, Japan, Hawaii, and Kuwait
reveal several genetically distinct regionally distributed lineages. Closer comparative examination of morphological characters and environmental
requirements reported in populations around the world has provided further evidence to reject the accepted status of this species as widespread
in the Indo-Pacific. We conclude that Spirobranchus kraussii is a warm temperate/ subtropical intertidal species restricted to South African
coasts. It belongs to a globally distributed complex including some tropical fouling and invasive species. Further study into taxonomy and invasion
ecology of this complex, especially in the Mediterranean, is needed. |
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Alison Yee, Joshua Mackie and Bruno Pernet
The distribution and unexpected genetic diversity of the non-indigenous annelid Ficopomatus enigmaticus in California
(pp 250–266)
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The non-indigenous annelid Ficopomatus enigmaticus has been established in San Francisco Bay since at least 1921, but in the past 30 years
it has also been found in other parts of California. In the summer of 2017 we surveyed 136 sites to determine its current distribution in the state.
We found F. enigmaticus at 23 sites ranging from San Francisco Bay in the north to Newport Bay in the south. Populations were concentrated
in four regions: San Francisco Bay, Monterey Bay, Santa Barbara, and sites in Los Angeles and Orange Counties. Presence sites did not differ
systematically in salinity or temperature from absence sites, but all presence sites appeared to have restricted exchange of water with nearby oceanic
habitats. Data on the timing of first discovery in each region is roughly consistent with the hypothesis of southward spread of propagules from
the San Francisco Bay population. To further test this hypothesis, we obtained mitochondrial DNA sequences from individuals collected from four sites
nearly spanning the current latitudinal range of F. enigmaticus in California. Recent work from Australia suggests that there is substantial
within-population cryptic genetic diversity in F. enigmaticus, with individual aggregations containing individuals whose mitochondrial
cytochrome B haplotypes fall into one of two very distinct (~ 19% uncorrected genetic distance) haplotype groups, Clades 1 and 2. We found a similar
pattern in California, with Clade 1 and Clade 2 individuals co-occurring at two of the four sites we sampled. Three of ten known F. enigmaticus
haplotypes occurring in Australia were observed in California populations; four haplotypes observed in California have not previously been reported.
Analysis of haplotype distributions suggests that central California populations may be derived from the San Francisco Bay population, while unique
haplotypes present in the Long Beach population suggest the possibility of a second independent introduction in that region. Additional genetic data
from populations of F. enigmaticus around the globe are needed to resolve the invasion history and systematics of these widespread serpulids. |
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Kiran Liversage and Jonne Kotta
A rare example of non-native chitons: broad intertidal habitat range and large densities of Sypharochiton pelliserpentis show no evidence of habitat engineering effect in South Australia
(pp 267–279)
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There are numerous examples of non-indigenous rocky-intertidal mobile invertebrate species, but there have been very few instances of introductions
of chitons despite their often high abundance in fouling assemblages where non-indigenous species originate. In 2016, it was observed incidentally
that the snake-skin chiton Sypharochiton pelliserpentis, native to eastern Australia and New Zealand, was occurring in Coffin Bay in western
South Australia, which is a sheltered bay used for oyster farming and far outside the previously documented S. pelliserpentis range. The main
coastal water currents in the region flow from west to east, meaning natural larval dispersal into Coffin Bay from eastern Australian populations
is unlikely. Surveys of population and community dynamics done in 2018 revealed that a large population has established with the non-native chiton
far outnumbering a comparable native chiton (Plaxiphora albida) that may occupy a similar niche space. The chitons occurred on exposed bedrock
habitats as well as cryptic habitats underneath boulders; both species were equally abundant between these habitats except at one site where
S. pelliserpentis densities specifically underneath boulders were 10 times greater than other habitat-types or sites.
Sypharochiton pelliserpentis in its native range can largely impact sessile assemblages; here we tested the hypothesis that sessile assemblages
would differ on boulders with versus without the non-native chiton, but no evidence of any such effect was found. Sypharochiton pellisperpentis
is a common epibiont of oyster-reefs and the origin of its introduction into South Australia may involve transport of oyster-industry materials,
which was how introductions of four other non-native benthic invertebrates occurred previously into another Australian region. The geographic extent
of S. pelliserpentis in South Australia is unknown at this stage but the chiton was not found during surveys in another nearby bay. Knowledge
that oyster-associated chitons may be spreading outside their native ranges, and that they can establish primarily in habitats that are largely hidden
from view, such as underneath boulders, can inform monitoring and management practices for ecology of non-indigenous intertidal species. |
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Yvon J.M. Verstijnen, Esther C.H.E.T. Lucassen, Marinus van der Gaag, Arco J. Wagenvoort, Henk Castelijns, Henk A.M. Ketelaars, Gerard van der Velde and Alfons J.P. Smolders
Trophic relationships in Dutch reservoirs recently invaded by Ponto-Caspian species: insights from fish trends and stable isotope analysis
(pp 280–298)
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Invasive species can directly or indirectly alter (a)biotic characteristics of ecosystems, resulting in changing energy flows through the food web.
This can potentially affect bottom-up or top-down control on resident species. The food web structure in the Biesbosch reservoirs (The Netherlands)
was examined after recent invasions of the quagga mussel (Dreissena rostriformis bugensis) and round goby (Neogobius melanostomus),
by means of stable isotope analysis. Quagga mussels reached relatively high densities after invasion, replacing the zebra mussel (D. polymorpha).
The δ13C signatures in the food web showed two distinct basic signatures of primary producers: 1) phytoplankton and
Elodea nuttallii, and 2) more enriched submerged macrophytes (i.e. Potamogeton sp.). Quagga mussel was found to rely on zooplankton
and phytoplankton. Mussel detritus seemed to be of importance for the gammarid Dikerogammarus spp. (both D. villosus and
D. haemobaphes). δ15N as a proxy for trophic level revealed that the largest specimens of ruffe (Gymnocephalus cernuus),
pike-perch (Sander lucioperca) and perch (Perca fluviatilis) formed the top of the food chain. A stable isotope mixing model estimated
that 43% of round goby diet consisted of Dikerogammarus spp. and approximately 27% of quagga mussels. Ruffe diet consisted of 29% of quagga
mussels and only 12% of Dikerogammarus sp. Quagga mussels were less important as a food source for round goby than often has been described.
Besides being a food source, mussel beds also provide a suitable habitat for macroinvertebrates (i.e. Dikerogammarus spp.). The invasive round
goby and native ruffe seemed to compete for food in the benthic zone, where round goby possibly forced ruffe to use less nutritive or favourable food
sources. Likely, this has contributed to the decline in ruffe abundance after the invasion of the highly competitive round goby. The altered and recent
new links between species have changed the food web. The successful invasion in the reservoirs by the benthic invaders — quagga mussel and round goby
— changed the benthic-pelagic coupling and has most likely increased the importance of the benthic food web in these reservoirs. |
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Boris Lipták, Lukáš Veselý, Fabio Ercoli, Martin Bláha, Miloš Buřič, Timo J. Ruokonen and Antonín Kouba
Trophic role of marbled crayfish in a lentic freshwater ecosystem
(pp 299–309)
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Species’ introductions may cause severe adverse effects on freshwater ecosystems and their biota. The marbled crayfish, Procambarus virginalis
Lyko, 2017, is an invasive parthenogenetically reproducing crayfish with rapid reproduction, maturation and tolerance to a wide range of environmental
conditions, which was introduced to many sites across Europe during the last decade. Due to its recent speciation and limited number of field studies,
the knowledge of trophic interactions of the marbled crayfish in freshwater food webs is scarce. An invaded area located in Central Europe was studied
to identify the marbled crayfish food web interactions using analysis of carbon
13C and nitrogen 15N isotopes.
This study brings the first insight into the trophic ecology of marbled crayfish in lentic freshwater ecosystems. Algae and detritus were identified
as the most important food sources for the marbled crayfish, while zoobenthos and macrophytes were less important. Moreover, the marbled crayfish
was found to be an important food source for top fish predators, but marginal for omnivorous fish. Being able to utilize energy from the bottom
of the trophic food web, the marbled crayfish may have important roles in the ecosystem, transferring energy to higher trophic levels. It processes
allochthonous and autochthonous matter in the ecosystem, thus being a competitor to other organisms with similar food preferences and impacting
zoobenthos, algae and macrophytes through predation or direct consumption. To sum up, the marbled crayfish has a strong ability to utilize food
sources from different trophic levels, and, thanks to its life history, can be a highly adaptable invader. |
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Fátima Amat-Trigo, Mar Torralva Forero, Ana Ruiz-Navarro and Francisco J. Oliva-Paterna
Colonization and plasticity in population traits of the invasive Alburnus alburnus along a longitudinal river gradient
in a Mediterranean river basin
(pp 310–331)
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Identification of the most relevant habitat features necessary for the success of potential invaders, such as the bleak Alburnus alburnus
with its high ecological risk, is fundamental for understanding the invasive process and, thus, for designing effective control programs.
This study provides new insights into the residence time and variation of population traits of this species along a longitudinal gradient
in one of the most regulated river basin in the Iberian Peninsula. Occurrence data collected from 25 sampling sites (three times in five years)
along the Segura River Basin (SE Spain) showed that this species has spread rapidly and now inhabits more than 168 km of fluvial stretches
(84.4% of the studied area). The captured individuals were four years old, although greater longevity and larger mature cohorts were more common
in sites with longer residence times. Higher values in population abundance in the upstream part of the river basin were accompanied by increased
growth rates and higher maximum sizes. The obtained results support the hypothesis that the wide plasticity of the population traits of
A. alburnus plays an important role in its success in a highly regulated Mediterranean river basin, where this mechanism allows it
to survive flow regulation events at various scales, as well as to resist the long-term environmental stress typical of Mediterranean-type rivers. |
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Julian R. Wilson, Richard J. Saunders and Kate S. Hutson
Parasites of the invasive tilapia Oreochromis mossambicus: evidence for co-introduction
(pp 332–349)
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Reduced parasite species diversity and infection intensity on invasive populations can facilitate establishment and spread of invasive species.
We investigated the parasite diversity of invasive populations of tilapia Oreochromis mossambicus from published literature and necropsies
conducted on 72 fish captured in the Ross River, north Queensland, Australia. The parasite diversity of invasive O. mossambicus from 13 countries
was compared to published reports on endemic populations in African river systems and tributaries to determine parasite species that had likely
been co-introduced. In total, four parasite species were shared between native and invasive tilapia. We propose that these parasites
(three monogeneans, Cichlidogyrus tilapiae Paperna, 1960, Cichlidogyrus sclerosus Paperna and Thurston, 1969, Cichlidogyrus halli
(Price and Kirk, 1967) and one trichodinid Trichodina heterodentata Duncan, 1977) have likely been co-introduced with invasive
Oreochromis mossambicus populations. Invasive Australian O. mossambicus had substantially reduced parasite diversity (five species)
compared to cumulative parasite species diversity documented from the native region (23 species). Australian O. mossambicus were infected
by two co-introduced parasites and three additional parasite species that have not been recorded previously on this species in Africa indicating
possible parasite “spillback” from Australian natives or alternatively, acquisition from other introduced fauna. The substantially reduced parasite
diversity on invasive Australian O. mossambicus could contribute to the ability of this species to become a serious fish pest. |
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María Agustina Waicheim, Marina Arbetman, Carlos Rauque and Gustavo Viozzi
The invasive parasitic copepod Lernaea cyprinacea: updated host-list and distribution, molecular identification and infection rates in Patagonia
(pp 350–364)
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Although competition and predation are mechanisms more studied in biological invasions, ecologists and conservation managers have become aware
of the threat imposed by the co-introduction of parasites. Parasites can be co-introduced into new areas with a non-native host, and become
co-invaders when they spill over to native hosts. The copepod Lernaea cyprinacea was presumably co-introduced to Patagonia along
with the common carp, Cyprinus carpio. Our aims were to compose an updated list of the hosts of L. cyprinacea and its distribution
in South America, to confirm the specific identity of Patagonian specimens using molecular tools, and to enlarge the list of hosts and localities
in Patagonia, by comparing infection rates between non-native and native fishes to evaluate spillover processes. Between the years 2011 and 2017,
native and non-native fish species were collected in freshwater environments from Northern Patagonia in basins where common carp and non-native
fishes belonging to the Brazilian biogeographic sub-region, like Characiforms, Siluriforms, and Cyprinodontiforms, have been introduced.
The sampled fishes were examined under a stereoscopic microscope to search for L. cyprinacea. At present, in South America, records
of L. cyprinacea parasitizing native and non-native hosts exist for Colombia, Uruguay, Brazil, Chile and Argentina, with a total of 43 host
fish species. Complete sequence data from the 18S region corroborate the identity of the Patagonian parasite based on morphological characteristics.
A total of 754 fish belonging to 13 species were collected and 388 copepods were recovered. Lernaea cyprinacea was registered in almost every
surveyed freshwater system in Patagonia, even in places where the original host, C. carpio, was absent. The copepod was found parasitizing
two native and four non-native fish species, and in general, native fishes showed higher infection values. The present study enlarges the list
of localities in Patagonia. It also provides molecular confirmation of the specific identity. In summary, our results show how an alien parasite
may switch host and disperse beyond the actual distribution range of the original host. This study provides an overview of the process of colonization
of L. cyprinacea in Patagonia, which represents a threat to native species due to its pathogenicity. |
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Daniel N. Mills, Michael A. Chadwick and Robert A. Francis
Artificial substrate experiments to investigate potential impacts of invasive quagga mussel (Dreissena rostriformis bugensis, Bivalvia: Dreissenidae) on macroinvertebrate communities in a UK river
(pp 365–383)
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Predicting potential impacts of a new invasive species remains difficult. A group of particular concern in the UK are freshwater
invertebrates from the Ponto-Caspian region, including the recently established quagga mussel (Dreissena rostriformis bugensis,
Bivalvia: Dreissenidae). We explored invertebrate colonisation across a series of manipulated substrate tiles with gradated densities of
D. r. bugensis shells fixed to their surface (2220, 1111, 666, 222 and 0 individuals m-²). Across three experiments
of different substrate tile deployment duration (14, 30 and 62 days), we observed significant differences in invertebrate density
and richness among shell density treatments. Variation was primarily driven by low and high values on our control and highest substrate
shell treatments, respectively. Within each experiment, similar taxa appeared to benefit from the physical effects of D. r. bugensis
beds (e.g. Gammarus pulex, Chironomidae spp., Elmidae spp. and Hydropsyche spp.) and were found with greater
abundance on substrate tiles with higher D. r. bugensis shell treatments. Compared to invertebrate density, the response of taxonomic
richness was weaker and only significant within our 30 and 62 day experiments of longer substrate tile deployment duration. Regardless,
increased invertebrate density and richness across the highest shell treatments provided a strong indication of potential D. r. bugensis
impacts on macroinvertebrates in the study river. If mussel densities were to increase to equivalent levels in other UK rivers, we could expect
similar impacts to benthic fauna. While the likelihood of D. r. bugensis achieving such population densities are uncertain in such environments,
our results were considered conservative because they did not account for additional facilitative impacts associated with live mussels. We add that,
in the context of invasive species management, potential facilitation of native benthic fauna associated with D. r. bugensis in the UK should
not be considered positively, nor necessarily sustainable over longer time periods. Further, facilitative effects could assist the establishment
of other invasive invertebrates such as amphipods of Dikerogammarus sp.,p which were first recorded in the study river during
this investigation. |
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Eui-Jeong Ko, Jeong-Soo Gim, Sungwon Hong, Hyunbin Jo, Ji Yoon Kim, Masato Hirose, Doo Hee Won, Hyun-Woo Kim and Gea-Jae Joo
Distribution and growth of non-native bryozoan Pectinatella magnifica (Leidy, 1851) in four large rivers in South Korea
(pp 384–396)
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Pectinatella magnifica Leidy, 1851 is a non-native freshwater bryozoan species that has successfully established in temperate
climate regions in the northern hemisphere. There is an ongoing rapid spread of this species in East Asia, but distribution studies
to date have failed to examine the growth characteristics of P. magnifica. We surveyed the distribution of P. magnifica
and its temporal growth at 52 sites in the four major rivers of South Korea. We used artificial substrates in the four rivers to observe
their growth. The frequency of occurrence of colonies across all sites was 28.2%. Pectinatella magnifica was broadly distributed
from meso- to eutrophic conditions. The dominant substrates for colony attachment were submerged dead trees and stones; however,
P. magnifica showed no specific preference. Colonies were identified from May to June, but these became detached owing to heavy
flooding during the monsoon season. Our study identified habitat conditions of P. magnifica and provides a guidance for the effective
management of introduced freshwater bryozoan species. |
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Marta Perez-Miguel, Enrique González-Ortegón, Pilar Drake, Jose I. Navas and Jose A. Cuesta
Temperature and salinity tolerance of the larval stages of the African pea crab Afropinnotheres monodi Manning, 1993: implications for its dispersal along European waters
(pp 397–411)
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The marine parasitic African pea crab Afropinnotheres monodi Manning, 1993 has well-established populations in the gulf of Cadiz,
where it is invasive. In this study, its tolerance to temperature and salinity variation during larval development were studied in the laboratory.
Larvae were reared in seawater (salinity 36) at different temperatures (5, 10, 15, 20, 25 and 30 °C). At 20 and 25 °C larval development was
successfully completed, with the highest rate of survival to the megalopa stage occurring at 25 °C. At this optimal temperature larvae were
reared at different salinities (15, 25, 36 and 45), and maximum survival to megalopa occurred at salinity 25. Additionally, the time required
for larval developmental increased with salinity: the shortest (12 days) and the longest (25 days) development time occurred at salinities 25 and 45,
respectively. In some of the treatments an extra stage (zoea V) was observed, but the only zoea V specimens that successfully moulted to megalopa
were those reared at 25 °C and salinity 25. Temperature seems to be the main factor determining whether larval development is successfully completed,
whereas salinity has an additional effect on duration of larval development under optimal temperature conditions. Our results suggest that
A. monodi is well-adapted to withstand higher temperatures than currently present in Europe’s marine waters and, if temperatures keep
increasing, this species may be able to expand successfully northward along the European Atlantic and Mediterranean coasts. |
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