Intragenomic variation of rDNA internal transcribed spacers in the endemic Baikal sponge Lubomirskia baikalensis (Pallas, 1776) (Spongillida,Lubomirskiidae): Implications for Porifera barcoding

Baikal endemic sponges are a species group for which species identification is difficult and the taxonomy is insufficiently developed. The rDNA ITS (internal transcribed spacers) are practical molecular markers for sponges. However, intragenomic polymorphism of the ITS spacers has recently been detected in many organisms including marine and freshwater sponges. We for the first time demonstrate intragenomic polymorphism of the ITS region in the sponge family Lubomirskiidae. We identified 27 new ITS1 and ITS2 haplotypes. The level of intragenomic polymorphism of the ITS1 and ITS2 regions in Lubomirskia baikalensis was 0.1–2.0%, which overlaps with the intraspecific polymorphism of L. baikalensis and to the interspecific polymorphism within Lubomirskiidae. Thus, the detected level of intragenomic polymorphism of Lubomirskiidae suggests species identification of Baikal sponges using ITS sequences would be difficult. The reasons for the lack of concerted evolution of the ITS spacers in Lubomirskiidae may be hybridization or insufficient divergence time. Our work contributes to the development of sponge barcoding markers.     

Genetic identification of two putative world record Michigan salmonids resolves stakeholder and manager questions

The ability of fishery managers to quickly and effectively answer stakeholder questions using the best available science is crucial for successful management. The 2009 capture of a potential world record brown trout (Salmo trutta) and the 2010 capture of a potential world record land-locked Atlantic salmon (S. salar) in Michigan required managers to acquire genetic verification of the species identity. Given the variety of hatchery strains used to maintain Great Lakes fisheries for brown trout and in the absence of physical markings, managers also were interested to determine the strain of origin for information on assessing performance. DNA barcoding techniques using sequences from the mitochondrial (mt) DNA cytochrome c oxidase I (COI) gene and frequency-based analysis of species-specific microsatellite genotypes provided data to establish the species of both fish. The putative brown trout was confirmed to be a new world record specimen. Using individual assignment tests based on maximum likelihood estimators informed by multi-locus microsatellite genotypes, we determined the fish to be from the Seeforellen hatchery strain (p < 0.01). Analysis of the COI gene in the putative Atlantic salmon resulted in assignment as a brown trout. The presence of only brown trout alleles at all six microsatellite loci examined revealed that the individual was not an inter-specific hybrid. Given sufficient genetic divergence exists among species, populations, or hatchery strains, the combination of mtDNA barcoding and microsatellite genetic analysis can provide accurate and rapid identification to address stakeholder and management questions.     

RNA/DNA ratio as an indicator of metabolic activity in resin acid-degrading bacteria

We investigated the relationship between the growth rate and the ratio of RNA to DNA in of four resin acid degrading bacteria isolated from a sequencing batch reactor (SBR). Chemical assays as well as slot blot hybndizations with species-specific oligonucleotide probes were used to quantify the nucleic acids. These slow-growing bacteria have a positive linear correlation between growth rate and RNA/DNA ratio, similar to faster-growing bacteria like E. coli. We propose to use this correlation to measure metabolic activities of selected resin acid degrading bacteria in the complex community of the SBR in situ using species-specific hybridization probes. Preliminary experiments suggest that hybridization probes can be used to detect growth rate-dependent changes in the RNA/DNA ratio.     

By-catch in the Saginaw Bay,Lake Huron commercial trap net fishery

This study provides species-specific catch and baseline mortality estimates of non-target species (by-catch) for the Saginaw Bay, Lake Huron commercial trap net fishery. By-catch can represent a significant mortality source that is often unknown. By-catch and by-catch mortality rates in the Saginaw Bay commercial trap net fishery, which primarily targets lake whitefish (Coregonus clupeaformis), yellow perch (Perca flavescens), and channel catfish (Ictalurus punctatus), are currently unknown. From May through August 2010, we observed onboard commercial trap net vessels and took species-specific counts of by-catch and estimated initial by-catch mortality (i.e., morbid or floating fish). The high levels of walleye (Sander vitreus) catch and mortality observed within inner Saginaw Bay have not been previously documented in the Laurentian Great Lakes. Walleye by-catch averaged 127.3 individuals per trap net lift and 42% of those caught were morbid. The levels of lake trout (Salvelinus namaycush) catch observed were within the range observed in previous studies, but mortality (percent) was higher than has been previously observed. Lake trout by-catch averaged 39.4 individuals per lift and 39.2% of those were morbid. Through the use of generalized linear models, this analysis also indicated factors that most influenced catch of non-target species including time of year and soak time (i.e., time interval between trap net lifts). Surface water temperature and trap net depth most influenced mortality. These results may inform fishers and fisheries managers and highlight the need for comprehensive by-catch monitoring throughout the Great Lakes.     

Distribution,seasonality and putative origin of the non-native red alga Bangia atropurpurea (Bangiales,Rhodophyta) in the Laurentian Great Lakes

Bangia atropurpurea was first observed in Lake Erie in 1964 and subsequently spread to the lower Laurentian Great Lakes by the mid to late 1970s. The present study was initiated to examine the recent distribution of B. atropurpurea in the Great Lakes, the seasonal variation of the alga and the putative origin of this species based on DNA sequence analysis. From surveys in 1995 and 2002, this species has clearly spread, with newly identified populations observed in Lakes Huron, Michigan, Georgian Bay and the St. Lawrence River. Morphological analyses showed that Great Lakes populations from individual lakes or neighboring populations did not group together in cluster analyses. Correlation analysis, however, revealed significant relationships between the presence or absence of Bangia among the studied sites with pH and specific conductance as those locations that had stable populations had a mean pH and conductance of 8.2 and 353 μS·cm^− 1 respectively. Seasonal variation in morphology of a population from Burlington, Ontario (Lake Ontario, Canada) was examined monthly for one year. Maximum filament length occurred in April, with the greatest diameter and archaeospore production observed in May. Significant correlations were also noted for many morphological characteristics with water temperature, population height on the shoreline relative to the waterline and total phosphorus. Collections of B. atropurpurea analyzed from the Great Lakes were observed to be identical in sequence to collections of European freshwater Bangia in the cox2–3 gene spacer, the nuclear internal transcribed spacers (ITS 1 and 2) and the 5.8S rRNA gene (between the small and large subunits of the rRNA gene). These results suggest a recent European origin; however, further global collections of B. atropurpurea and microsatellite analyses are necessary to confirm this hypothesis.     

Testing for hybridization between Nile tilapia (Oreochromis niloticus) and blue spotted tilapia (Oreochromis leucostictus) in the Lake Edward system

Oreochromis is the most important tropical freshwater fish genus for aquaculture purposes, with various introduction and translocation events having played an integral part of its management. Some Oreochromis species such as the Nile tilapia, O. niloticus, are thought to be superior for aquacultural purposes when compared to other species. Hence, understanding the admixed nature of the species within a native system is of key importance for the development of future broodstock. Using a combination of mitochondrial (COI) and nuclear (microsatellites) DNA, we tested for the presence of O. niloticus and O. leucostictus hybrids within the Lake Edward-George system. The present study revealed that, despite their natural overlapping ranges, hybridization between O. niloticus and O. leucostictus appears to be rare within the Lake Edward-George system, suggesting that the native populations of these two species may serve as suitable broodstock to develop future aquaculture strains. Moreover, our study provides the first COI sequences for O. leucostictus from its native range and adds to the growing database of O. niloticus sequences.     

Seasonal Variation in Oxygen Isotopic Composition of Two Freshwater Bivalves: Sphaerium striatinum and Anodonta grandis

Oxygen isotopic values have been obtained from microsamples of the aragonitic freshwater bivalves Sphaerium striatinum (Pisidiidae) and Anodonta grandis (Unionidae) collected alive from Wellington Creek, OH. To test whether these organisms secrete their shell in isotopic equilibrium, the SO values of shell aragonite are compared to ambient water temperature and δ¹⁸O values monitored for > 1 yr. These bivalves were chosen for study because they are abundant in surface sediments and cores from Lake Erie where they represent a source of information on the environmental history of the lake. The observed mean values are −5.54‰ for A. grandis and −6.16‰ for S. striatinum. The mean δ¹⁸O value expected for bivalve aragonite if equilibrium precipitation is occurring during May–August in Wellington Creek is −5.69‰. The similarity between measured and predicted isotopic values for both species suggests that they are useful sources of paleoenvironmental data. Overall, the isotopic composition of the shells of the two species reflects less than one half of the calculated range of potential biogenic aragonite values for the stream and omits recording evaporative conditions associated with ponded water. Bivalve δ¹⁸O and δ¹³C data covary. The δ¹³C data are highly negative and values could reflect ¹²C enrichment of dissolved organic carbon from organic matter oxidation and/or ingestion of food carbon.     

Particle Mixing Rates of Freshwater Bivalves: Anodonta grandis (Unionidae) and Sphaerium striatinum (Pisidiidae)

Sediment mixing by freshwater suspension feeding bivalves Anodonta grandis (Unionidae) and Sphaerium striatinum (Pisidiidae) was studied by adding illite clay particles with adsorbed ^I37Cs as a submillimeter thick layer to the surface of silt clay sediments contained in clear rectangular cells maintained in a temperature regulated aquarium. A Nal gamma detector scanned the sediment column in each cell at 0.2 cm intervals five times over 22 days and recorded changes in ^I37Cs activity over time with depth in cells containing 3 A. grandis, 4 S. striatinum, and a control cell containing no bivalves. Sediment mixing by these organisms was diffusional. The diffusion coefficient in the control cell was 0.02 cm²/yr, consistent with molecular diffusion of¹³⁷Cs tracer. Whole cell biodiffusion coefficients (D_b)for A. grandis and S. striatinum were 0.81–2.11 cm²/yr and 0.53 cm²/yr, respectively. Adjusting to equal population densities, the 11-27× higher sediment mixing rate of A. grandis was likely due primarily to its larger size. When D_bfor similar sized organisms was compared, S. striatinum was found to mix sediments at about the same rate as the marine bivalve Nucula proxima but at a 5× lower rate than the freshwater amphipod Diporeia sp. A. grandis mixes sediments 5–14× more slowly than the similar sized conveyor belt deposit feeding marine bivalve, Yoldia limatula.. While deposit feeding organisms are the dominant sediment mixers in the Great Lakes, suspension feeding bivalves can be locally significant.     

A Species-Specific and spatially-Explicit Model for Estimating Vegetation Water Requirements in Desert Riparian Forest Zones

Balancing human demands for water with environmental requirements to maintain functioning ecosystems requires the quantification of ecological water requirements. In arid regions, high spatial variability of vegetation cover and different water consumption of plant species make it different to estimate reasonable ecological water requirements. We developed a simple and practical approach that estimates the vegetation water requirements (VWRs) of desert riparian ecosystems. This model is species-specific and spatially-explicit; it considers the water consumption characteristics required by different species and highlights the impacts that high vegetation cover spatial variability has in arid regions on evapotranspiration. The model was parameterized based on the observation of the water consumption of two typical desert riparian species, Populus euphratica and Tamarix spp., in the lower basin of the Tarim River in northwestern China. Comparisons between the modeling results and measured data for two mature Populus and Tamarix stands indicate that the model is reasonable predictive. A case study in the lower basin of the Tarim River demonstrated the model’s practicality and transferability. This model could run based on near real-time or forest weather data and spatial vegetation patterns, and provides a continuous estimation of the temporal and spatial variations of the VWR. Particularly, this model forecasts VWRs under different vegetation spatial distribution and coverage scenarios, and evaluates the impacts and consequences of different management actions. This model can serve as a useful tool for management agencies interested in improving their decisions to allocate river water between human activities and natural ecosystems in arid regions.     

Fungal community dynamics associated with harmful cyanobacterial blooms in two Great Lakes

Harmful algal blooms (HABs) impose major costs on aquatic ecosystems worldwide, including the Laurentian Great Lakes. Microbial consumers, including fungi, can have important interactions with bloom-forming algae and cyanobacteria, although relatively few studies have investigated the relationship between fungi and HABs. We examined changes in the aquatic fungal community coincident with the occurrence of large cyanobacterial blooms in two areas of the Great Lakes (western Lake Erie and Saginaw Bay, Lake Huron). We collected water samples over the course of bloom development, peak, and decline from 3 sites in western Lake Erie on 11 dates and 2 sites in Saginaw Bay on 4 dates. Single molecule sequencing (PacBio RS II) with two molecular markers (the internal transcribed spacer (ITS) of the rRNA locus using fungal-specific primers and the 18S rRNA with primers targeting early-diverging lineages of fungi) was used to estimate fungal community composition. Results indicate a diverse fungal community within the lakes, including several major fungal phyla. The Chytridiomycota were particularly well-represented (54.8% and 45.4% of ITS and 18S sequences, respectively), and we also found representation from both Cryptomycota and Aphelidiomycota, which are putatively obligate intracellular parasites. Further, we found associations between the fungal community (alpha diversity; community composition) and measures of bloom magnitude (chlorophyll a, phycocyanin, and microcystin concentrations) in western Lake Erie. Our results suggest potentially important spatial and temporal heterogeneity in the fungal community that motivates further research on functional importance of fungi in the Great Lakes and consequences for HABs and freshwater ecosystems more broadly.     

Beginning a molecular analysis of the eukaryal community in activated sludge

As a means to furthering our understanding of the eukaryal community to activated sludge, we have applied contemporary molecular techniques to an activated sludge community maintained in a laboratory-scale bioreactor. The initial inoculum was derived from a local wastewater treatment facility in East Lansing, MI and maintained with continuous aeration and a daily feeding regime that included glucose and peptone Samples were taken on a weekly basis for 5 weeks and community DNA was extracted from 2–5 ml of activated sludge. Using a variety of oligonucleotide primers specific to eukaryotic small subunit ribosomal DNA, we PCR amplified rDNA from the total community DNA. PCR products were analyzed by three techniques, denaturing gradient gel electrophoresis (DGGE), terminal restriction fragment length polymorphism (T-RFLP) and comparative sequence analysis of rDNA clones. Over the course of 5 weeks, analysis with DGGE revealed dramatic changes in the eukaryotic community based on differences in denaturation profiles. However, the analysis is limited to 5–6 bands corresponding to 5–6 different “ribotypes”. Analysis with T-RFLP also suggests changes to the eukaryotic community over time. Both increases and decreases in population size can be detected as a function of time. Up to 15 different terminal restriction fragments can be detected with T-RFLP indicating that this technique is considerably more sensitive than DGGE. Phylogenetic analysis of partial sequences from 1 I cloned rDNAs indicate that all 11 clones are from the Ciliophora phylum.     

Dietary differences among commercially important fishes in Lake Tanganyika assessed using stable isotope analysis

The pelagic fishery of Lake Tanganyika, which is largely made up of the three species Lates stappersii, Limnothrissa miodon, and Stolothrissa tanganicae, has been in decline, and there is no clear understanding of the primary underlying causes. It has been suggested that climate change has altered the primary productivity of the system, but detailed knowledge of the system's food web is required to elucidate the effect on higher trophic levels. The aim of this study is to determine the diet of the three commercially important fish species. Muscle tissue samples for stable isotope analysis were taken from February through April 2017, supplemented with stomach samples from L. stappersii for use in stomach content analysis. The stomach analysis showed an ontogenetic change in the diet composition of L. stappersii, shifting from copepods to fish larvae, supplemented with shrimp, to whole fish prey as the fish grew larger. Stable carbon and nitrogen isotope values from fish muscle were consistent with this observation, and also seemed to indicate that fish of similar sizes had similar diets, irrespective of species. This suggests that the diet of the pelagic fish species might be better explained by size, rather than species. The isotope data revealed a short range of δ¹⁵N values from primary consumers to fish, which may help explain the high fisheries productivity of Lake Tanganyika, and the strong impact of primary productivity changes on fisheries yield.     

Lyngbya wollei in western Lake Erie

We report on the emergence of the potentially toxic filamentous cyanobacterium, Lyngbya wollei as a nuisance species in western Lake Erie. The first indication of heavy L. wollei growth along the lake bottom occurred in September 2006, when a storm deposited large mats of L. wollei in coves along the south shore of Maumee Bay. These mats remained intact over winter and new growth was observed along the margins in April 2007. Mats ranged in thickness from 0.2 to 1.2 m and we estimated that one 100-m stretch of shoreline along the southern shore of Maumee Bay was covered with approximately 200 metric tons of L. wollei. Nearshore surveys conducted in July 2008 revealed greatest benthic L. wollei biomass (591 g/m² ± 361 g/m² fresh weight) in Maumee Bay at depth contours between 1.5 and 3.5 m corresponding to benthic irradiance of approximately 4.0–0.05% of surface irradiance and sand/crushed dreissenid mussel shell-type substrate. A shoreline survey indicated a generally decreasing prevalence of shoreline L. wollei mats with distance from Maumee Bay. Surveys of nearshore benthic areas outside of Maumee Bay revealed substantial L. wollei beds north along the Michigan shoreline, but very little L wollei growth to the east along the Ohio shoreline.     

Asymmetric Hybridization of Pink (Oncorhynchus gorbuscha) and Chinook (O. tshawytscha) Salmon in the St. Marys River,Michigan

Natural hybridization between pink salmon (Oncorhynchus gorbuscha) and Chinook salmon (O. tshawytscha) has been observed only in the Great Lakes, where both species have been introduced. The direction of hybridization between these species is poorly understood, thus the present study analyzed mitochondrial DNA (mtDNA) to determine whether the maternal parents were pink or Chinook salmon. During annual salmon population surveys on the St. Marys River (1998–2002), fifty putative hybrids of pink salmon and Chinook salmon were identified from meristic, morphometric and color characters. We designed primers to amplify a fragment of the mitochondrial D-loop control region that included both a variable and a control restriction site (BstNI). Polymerase chain reaction, restriction endonuclease digestion and capillary electrophoresis of mtDNA were used in order to identify the maternal parent of each hybrid salmon. In addition, the amplified fragments from the three fish species were sequenced to further verify the results. All hybrid salmon specimens were found to possess Chinook salmon mtDNA, indicating that hybridization between Chinook salmon and pink salmon is asymmetrical and likely unidirectional, occurring only between male pink salmon and female Chinook salmon. Influences contributing to the hybridization of these salmonid species could include limited spatial and temporal segregation of spawners, sexual selection, a limiting number of Chinook males, and/or physiological factors.     

Oligochaete Fauna of Western Lake Erie 1961 and 1982: Signs of Sediment Quality Recovery

The oligochaete fauna at 40 stations in western Lake Erie were collected in 1982 and compared to oligochaete fauna collected similarly in 1961. A total of 34 taxa, representing 18 Tubificidae and 16 Naididae, were identified. Changes in the proportions of low, moderate, and heavy polluted sediments, as determined by ranges of total numbers of oligochaetes, indicate that, in general, heavy pollution substantially decreased near shore and moderate pollution increased and low pollution decreased in open waters over the 21-year comparison. The most common taxon, the eutrophic species, Limnodrilus hoffmeisteri, decreased in abundance in open water, indicating decreased eutrophication, whereas the distribution and abundance of other indicator taxa, including the eutrophic species L. maumeensis, L. cervix, Quistadrilus multisetosus multisetosus, and mesotrophic species Ilyodrilus templetoni and three species of Aulodrilus indicate increased eutrophication in open water. In general, oligochaete trophic indices (based on tubificid species and abundances) in traditional area designations used in 1961, the nearshore designation (<3.5 km from shore), and areas defined by cluster analysis confirm results of less eutrophic substrates near shore. However, traditional analysis indicates that low pollution was replaced by moderate pollution in open waters and cluster analysis indicates that the zone of least detectable pollution increased in open waters over the 21-year comparison. It may be that the open waters of western Lake Erie were in a stage of transition between pollution designations when sampled in 1982. The present study is valuable because it provides a baseline to assess environmental changes observed in western Lake Erie after many years of pollution abatement programs and before the exponential increase in densities of the trophic shifting zebra mussel Dreissena polymorpha.     

Population connectivity of aquatic insects in a dam-regulated,desert river

Humans have exaggerated natural habitat fragmentation, negatively impacting species dispersal and reducing population connectivity. Habitat fragmentation can be especially detrimental in freshwater populations, whose dispersal is already constrained by the river network structure. Aquatic insects, for instance, are generally limited to two primary modes of dispersal: downstream drift in the aquatic juvenile life stages and flight during the terrestrial winged adult stage. Yet the impacts of large hydropower dams can make rivers uninhabitable for incoming (drifting) juvenile insects, with remaining refugia found only in tributaries. The ability of adult aquatic insects to traverse such river stretches in search of suitable tributary habitat likely depends on factors such as species-specific dispersal ability and distance between tributaries. To explore the intersection of natural and human-induced habitat fragmentation on aquatic insect dispersal ability, we quantified population genetics of three taxa with varying dispersal abilities, a caddisfly (Hydropsychidae, Hydropsyche oslari), a mayfly (Baetidae: Fallceon quilleri), and a water strider (Veliidae: Rhagovelia distincta), throughout tributaries of the Colorado River in the Grand Canyon, Arizona, USA. Using 2bRAD reduced genome sequencing and landscape genetics analyses, we revealed a strong pattern of isolation by distance among mayfly populations. This contrasts with caddisfly and water strider populations, which were largely panmictic. Analysis of thousands of informative single nucleotide polymorphisms showed that realized dispersal ability may not be accurately predicted by species traits for these widespread species. Principal components analysis revealed a strong division between caddisfly populations upstream and downstream of Havasu Creek (279 km through the 390 km study reach), suggesting that the geography of the Grand Canyon imposes a dispersal barrier for this species. Our use of genetic tools in the Grand Canyon to understand population structure has enabled us to elucidate dispersal barriers for aquatic insects. Ultimately, these data may be useful in informing effective conservation management plans for understudied organisms of conservation interest.     

Evaluation of candidate biocides to control the biofouling Asian clam in the drinking water treatment industry: An environmentally friendly approach

The biofouling Asian clam Corbicula fluminea greatly affects freshwater-dependent facilities in Europe and North America, including in the Great Lakes region. As chlorination has become increasingly restricted, finding alternative control agents is a priority. Due to the species' epifaunal nature, the body of knowledge on Dreissena polymorpha is larger than that on the Asian clam, and there is a tendency to assume that mitigation methods should work similarly for both species. However, this generalisation is inaccurate, and the optimisation of Asian clam control relies on species-specific toxicological data. This paper reports information on the potential of three candidate biocides for C. fluminea control: (i) the cationic polydiallyldimethylammonium chloride (polyDADMAC), (ii) potassium chloride and (iii) aluminum sulphate. While these chemicals may be employed in a range of contexts, they are particularly suitable for the highly regulated drinking water industry. LT₅₀ values ranging from 284.3 h, for polyDADMAC applied at 10 mg/L, to 855.1 h, for an aluminum sulphate concentration of 11 mg/L, were obtained. Ecotoxicological standard tests with Pseudokirchneriella subcapitata and Daphnia magna suggested that, amongst the three biocides, potassium chloride is the one representing lower potential environmental hazard (with, for example, 48 h-EC₅₀ higher than 1 g/L for Daphnia immobilisation, which compares to values of 20.2 and 112.5 mg/L for polyDADMAC and aluminum sulphate, respectively). The three chemicals are promising control agents at dosages compatible with waterworks' operational requirements with polyDADMAC having the highest biocidal activity, but also posing more environmental risks.     

Spotty distributions: Spotted Gar (Lepisosteus oculatus) and Spotted Sucker (Minytrema melanops) range expansion in eastern Lake Erie

Natural range expansions in warm-water freshwater fishes are currently not well understood, but shifts in native species distributions can be influenced by many factors, including habitat restoration or degradation and climate change. Here, we provide empirical evidence of range expansions observed in two native freshwater fish species in Lake Erie: Spotted Gar (Lepisosteus oculatus) and Spotted Sucker (Minytrema melanops). We confirmed our field identifications of L. oculatus and M. melanops using mtDNA barcoding. Maximum likelihood phylogenetic analyses reveal that our samples confidently resolve in the L. oculatus and M. melanops clades respectively, with additional identification support from BLAST searches. Notably, we found no correlation between the increased detection rate of both species and an increase in sampling effort when compared to previous records. Historically, eastern Lake Erie experienced habitat degradation through channelization, siltation, dredging, and toxification of sediments. We hypothesize that recent habitat remediation efforts have provided suitable habitat for both species to recolonize shallow waters with densely vegetated habitat (>90% substrate coverage). Both species are likely to continue their northern expansion as habitats are restored and climatic changes favor warm-water fishes.     

Failure to diverge in African Great Lakes: The case of Dolicirroplectanum lacustre gen. nov. comb. nov. (Monogenea,Diplectanidae) infecting latid hosts

Speciation of fish in the African Great Lakes has been widely studied. Surprisingly, extensive speciation in parasites was only recently discovered in these biodiversity hotspots, notably in monogeneans (Platyhelminthes) from Lake Tanganyika. Diplectanum is a monogenean genus of which only a single species is known from the Great Lakes: Diplectanum lacustre (Diplectanidae) living on lates perches (Latidae) of Lake Albert. Despite their primary marine origin, latids have diversified in African freshwaters including several Great Lakes. In better-studied marine diplectanid species, incongruence between morphological and genetic differentiation was documented. As freshwater systems provide more opportunities for speciation than the marine realm, we ask whether diplectanids of Lates spp. of the Great Lakes underwent similar diversification as their hosts. Fresh and museum specimens of five African latid species (Lates angustifrons, L. mariae, L. microlepis, L. niloticus, L. stappersii) were examined for the presence of monogenean gill parasites. Monogeneans were characterised morphologically via morphometrics of sclerotised structures and genetically using nuclear and mitochondrial markers. Continuous morphological variation was documented in these parasites. In addition, the genetic distance, based on the COI region, between parasites of geographically isolated host species did not reach the level typically associated with distinct diplectanid species. Therefore, a single species of a newly described genus, Dolicirroplectanum lacustre gen. nov. comb. nov. is suggested to infect latid species in the examined basins. We discuss this parasite’s failure to diverge in the light of the congruence between the rate of molecular evolution in COI and host historical distribution.     

Phylogenetic relationships and historical population reconstruction of Asian members of the genus Epischura (Copepoda,Calanoida)

We have reconstructed major demographic and phylogenetic events for two closely related copepod species: Epischura baikalensis Sars, 1900 (Copepoda, Calanoida), a key endemic species of the plankton community from Lake Baikal, and E. chankensis Rylov, 1928, a key zooplankton species from Lake Khanka. The reconstructions were based on the nucleotide sequences of mitochondrial DNA (mtDNA) cytochrome oxidase subunit 1 (CO1) using the BEAST software package and recently identified calibrations for the Baikal amphipods Gmelinoides fasciatus. The time span to a common ancestor for E. baikalensis and E. chankensis is 13.7 million years (95% confidence interval is 8.3–21.4 million years. Both species studied have experienced abrupt changes in the effective population size in the past. These changes are likely associated with climate and geological shifts in their habitat areas. For E. baikalensis, these changes can be associated with alternating glacier and interglacial periods as well as an increase in depth of Lake Baikal; for E. chankensis with formation and increase in the area of Lake Khanka, which was also due to climate and geological shifts in the Khanka basin.