Lampetra Fluviatilis Research Articles

Histomorphological and Dynamical Changes in Female River Lampreys during Maturation under Controlled Conditions as a Part of Lamprey Restoration Programs.

More than 40 species of lampreys (Petromyzontiformes) are known worldwide. Some of them are parasitic and feed on the blood of fish or other aquatic animals. Lampreys spawn once in their lifetime, after which they die. One of the representatives of the ichthyofauna of European rivers is the river lamprey, Lampetra fluviatilis. The river lamprey is now an endangered species due to loss and degradation of their habitats. The present study investigated gonadal development without hormonal stimulation in female river lampreys during puberty under controlled conditions for a period of seven months. Female river lampreys were kept in conditions that mimicked the natural environment. During the November-May period, samples were taken monthly to determine the extent of gonadal development and gastrointestinal and liver changes using histological examination. From the results obtained, the dynamical changes were determined for the following: gonadosomatic index (GSI; %), hepatosomatic index (his; %), and digestivesomatic index (DSI; %). With the gonadal development of female lampreys, an increase in GSI (7-23%; November-May) and a decrease in DSI (0.4-0.1%; November-May) histological changes were observed in the gonads (oocyte development), intestines (over time, decreased lipid vacuoles and enterocyte apoptosis), and in the liver (decreased lipid vacuoles and hepatocyte apoptosis over time) and in the digestive system resulting from its degradation. Also, it was observed that there was a change in the color of the liver to green in April. This study demonstrated the key role of the liver in the oocyte maturation process in this species.

Variability and phenotypic diversity of the Diplostomum Petromyzifluviatilis Diesing, 1850 trematodes, parasites of lampreys (Lampetrinae, Petromyzontidae)

Variability and phenotypic diversity of Diplostomum petromyzifluviatilis metacercariae from two lamprey species, the river lamprey Lampetra fluviatilis (Baltic Sea basin) and the Pacific lamprey Lethenteron camtschaticum (Arctic Ocean basin), were studied. It was found that metacercariae from both hosts are similar as in the number of variations in body shape, oral and ventral suckers, and pharynx, so in the frequency of occurrence. Differences in population diversity by variations in the shape of the Holdfast organ were found. It was shown that gostal forms possess the similar range of variability of plastic characters, but has different distribution of frequency classes of the variation curve. We hypothesized that the change in the distribution and character of variation in the size of metacercariae from the Arctic lamprey is one of the population mechanisms of species adaptation to the northern limit of its range.

ROS formation, mitochondrial potential and osmotic stability of the lamprey red blood cells: effect of adrenergic stimulation and hypoosmotic stress.

Semi-anadromous animals experience salinity fluctuations during their life-span period. Alterations of environmental conditions induce stress response where catecholamines (CA) play a central role. Physiological stress and changes in external and internal osmolarity are frequently associated with increased production of reactive oxygen species (ROS). In this work, we studied the involvement of the cAMP/PKA pathway in mediating catecholamine-dependent effects on osmoregulatory responses, intracellular production of ROS, and mitochondrial membrane potential of the river lamprey (Lampetra fluviatilis, Linnaeus, 1758) red blood cells (RBCs). We also investigated the role of hypoosmotic shock in the process of ROS production and mitochondrial respiration of RBCs. For this, osmotic stability and the dynamics of the regulatory volume decrease (RVD) following hypoosmotic swelling, intracellular ROS levels, and changes in mitochondrial membrane potential were assessed in RBCs treated with epinephrine (Epi, 25 μM) and forskolin (Forsk, 20 μM). Epi and Forsk markedly reduced the osmotic stability of the lamprey RBCs whereas did not affect the dynamics of the RVD response in a hypoosmotic environment. Activation of PKA with Epi and Forsk increased ROS levels and decreased mitochondrial membrane potential of the lamprey RBCs. In contrast, upon hypoosmotic shock enhanced ROS production in RBCs was accompanied by increased mitochondrial membrane potential. Overall, a decrease in RBC osmotic stability and the enhancement of ROS formation induced by β-adrenergic stimulation raises concerns about stress-associated changes in RBC functions in agnathans. Increased ROS production in RBCs under hypoosmotic shock indicates that a decrease in blood osmolarity may be associated with oxidative damage of RBCs during lamprey migration.

Accuracy of coarse-resolution protocols for assessing fish passability at river infrastructure

River infrastructure can present a major barrier to fish movement. While mitigation can be achieved through infrastructure removal or modification, e.g. construction of fish passes, prioritising this work to maximise ecological benefit within budgetary and other constraints remains a substantial management challenge. Several coarse-resolution rapid barrier assessment protocols have been developed to estimate fish passability at river infrastructure to aid decision making in relation to catchment scale barrier management. The outputs of these protocols are rarely validated against empirical data, such as that provided by telemetry or other methods of tracking fish, limiting confidence in whether they provide realistic estimates of fish passability. In this study, the accuracy of two barrier passability assessment protocols yet to be validated against empirical data, SNIFFER and ICE, developed in the UK and France, respectively, was assessed by: 1) collating available empirical multi-species fish passage data at river infrastructure, 2) undertaking field surveys at each structure to quantify SNIFFER and ICE passability scores, and 3) comparing the fish passage data with the estimated passability scores. Fish passage data were obtained for four species (Salmo trutta, Cottus gobio, Lampetra fluviatilis and Thymallus thymallus) and five barrier types (sloped weir, culvert, rock ramp, nature-like bypass, and some classified as ‘complex’) at thirteen sites in England. Both protocols suggest these barriers are a major impediment to upstream moving fish as a classification of ‘impassable’ was the most common. However, agreement between protocols was low for barriers considered ‘high impact’, ‘low impact’ or ‘easily passable’. When compared with empirical fish passage data, there was a positive relationship with the passability scores predicted by SNIFFER, but the protocol tended to be conservative. There was no relationship between the empirical fish passage data and the passability scores predicted by ICE, although field surveys were undertaken outside of the recommended discharge range which may have influenced accuracy. This study provides the first partial validation of two barrier passability assessment protocols and suggests that further detailed validation is needed to calibrate the passability scores and enhance confidence in the planning tools (e.g. optimisation models) that utilise their outputs.

The Molecular Mechanism of Body Axis Induction in Lampreys May Differ from That in Amphibians.

Lamprey homologues of the classic embryonic inducer Noggin are similar in expression pattern and functional properties to Noggin homologues of jawed vertebrates. All noggin genes of vertebrates apparently originated from a single ancestral gene as a result of genome duplications. nogginA, nogginB and nogginC of lampreys, like noggin1 and noggin2 of gnathostomes, demonstrate the ability to induce complete secondary axes with forebrain and eye structures when overexpressed in Xenopus laevis embryos. According to current views, this finding indicates the ability of lamprey Noggin proteins to suppress the activity of the BMP, Nodal/Activin and Wnt/beta-catenin signaling pathways, as shown for Noggin proteins of gnathostomes. In this work, by analogy with experiments in Xenopus embryos, we attempted to induce secondary axes in the European river lamprey Lampetra fluviatilis by injecting noggin mRNAs into lamprey eggs in vivo. Surprisingly, unlike what occurs in amphibians, secondary axis induction in the lampreys either by noggin mRNAs or by chordin and cerberus mRNAs, the inductive properties of which have been described, was not observed. Only wnt8a mRNA demonstrated the ability to induce secondary axes in the lampreys. Such results may indicate that the mechanism of axial specification in lampreys, which represent jawless vertebrates, may differ in detail from that in the jawed clade.

Three foxg1 paralogues in lampreys and gnathostomes-brothers or cousins?

Foxg1 is a key regulator of the early development of the vertebrate forebrain and sensory organs. In this study, we describe for the first time three foxg1 paralogues in lamprey, representative of one of two basally diverged lineages of vertebrates-the agnathans. We also first describe three foxg1 genes in sterlet-representative of one of the evolutionarily ancient clades of gnathostomes. According to the analysis of local genomic synteny, three foxg1 genes of agnathans and gnathostomes have a common origin as a result of two rounds of genomic duplications in the early evolution of vertebrates. At the same time, it is difficult to reliably establish pairwise orthology between foxg1 genes of agnathans and gnathostomes based on the analysis of phylogeny and local genomic synteny, as well as our studies of the spatiotemporal expression of foxg1 genes in the river lamprey Lampetra fluviatilis and the sterlet Acipenser ruthenus. Thus, the appearance of three foxg1 paralogues in agnathans and gnathostomes could have occurred either as a result of two rounds of duplication of the vertebrate common ancestor genome (2R hypothesis) or as a result of the first common round followed by subsequent independent polyploidizations in two evolutionary lineages (1R hypothesis).

European River Lamprey Lampetrafluviatilis (Petromyzontidae) of the Pskov Lakeland: Current State of Isolated Populations

Small freshwater (resident) populations of the European river lamprey Lampetrafluviatilis from an isolated from the sea upper part of a river system with numerous lakes (the upper reaches of tributaries of the Daugava River and Lake Peipus, Pskov Oblast, Russia) have been studied. Adult individuals of the lamprey have been attributed to common and large size groups; adults are similar to other resident lamprey from the Baltic Sea basin. The presence of larvae of different size and age groups indicates regular spawning of the European river lamprey in the studied watersheds. Analysis of the modern and historical (before the isolation) distribution of lamprey revealed a reduction in habitats and a decrease in the number of individuals. Dam-associated disruption of migration routes led to the disappearance of anadromous form, and consequently, disappearance of resident lamprey from most of the studied waterbodies. We attribute the decrease in the number of rivers inhabited by lamprey and abundance of the lamprey both to anthropogenic factors (direct blocking of an access of anadromous form of the lamprey to spawning grounds by hydraulic construction) and to the characteristics of the studied area. The richness of the river system with lentic waterbodies makes it suitable for lamprey inhabitation with an influx of large anadromous individuals capable of crossing such reservoirs in search of spawning sites.

Isotopic niches of diadromous fishes inform on interspecific competition in an obstructed catchment

Competition arises when species share a limited resource, but this can be avoided through niche partitioning. Despite the large body of literature on diadromous fishes, very few studies have focused on niche partitioning when competing for resources. Diadromous fishes are suffering a global decline throughout their range in part due to their peculiar life history traits as they migrate from the sea to freshwater to spawn or the reverse. They are particularly sensitive to river fragmentation induced by barriers. Dams for instance are expected to alter the spatial distribution and resource exploitation of diadromous fishes as well as other organisms. Here, we studied the ecological niche of six taxa of diadromous fishes, temporally co-occurring in the same land–sea continuum obstructed by two river dams. We used Bayesian mixing models run on C and N isotopes to infer the various habitats used and the origin of the trophic carbon in muscle and scale tissues of diadromous fishes. Results showed that the sub-adults of Anguilla anguilla, juveniles of Petromyzon marinus, and Salmo trutta exploit mainly the freshwater, or marine part for adults of Lampetra fluviatilis, whereas juveniles of Platichthys flesus and Mugilidae use all the habitats of the land–sea continuum. In the freshwater habitat, the microphytobenthos and biofilm are the main sources of carbon used, while in the marine habitat, the basal carbon sources are more diverse. The analyses of niche overlaps between diadromous fishes demonstrate that the widest isotopic niches, observed for A. anguilla and P. flesus, also have more impact within the community. Results are discussed in terms of intra- and interspecific competition between these diadromous fishes and their generalist/specialist strategies in an obstructed catchment.

European River Lamprey Lampetra fluviatilis (Petromyzontidae) of the Pskov Lakeland: Current State of Isolated Populations

Small freshwater (resident) populations of the European river lamprey Lampetra fluviatilis from an isolated from the sea upper part of a river system with numerous lakes (the upper reaches of tributaries of the Daugava River and Lake Peipus, Pskov Oblast, Russia) have been studied. Adult individuals of the lamprey have been attributed to common and large size groups; adults are similar to other resident lamprey from the Baltic Sea basin. The presence of larvae of different size and age groups indicates regular spawning of the European river lamprey in the studied watersheds. Analysis of the modern and historical (before the isolation) distribution of lamprey revealed a reduction in habitats and a decrease in the number of individuals. Dam-associated disruption of migration routes led to the disappearance of anadromous form, and consequently, disappearance of resident lamprey from most of the studied waterbodies. We attribute the decrease in the number of rivers inhabited by lamprey and abundance of the lamprey both to anthropogenic factors (direct blocking of an access of anadromous form of the lamprey to spawning grounds by hydraulic construction) and to the characteristics of the studied area. The richness of the river system with lentic waterbodies makes it suitable for lamprey inhabitation with an influx of large anadromous individuals capable of crossing such reservoirs in search of spawning sites.

Acoustic telemetry informs conditional capture probability of an anadromous fish

Information on movement ecology and susceptibility to fishing gears is becoming increasingly employed in the management of commercial fisheries. This study combined acoustic telemetry (n = 51 and 52) and a simple passive integrated transponder (PIT) tag (n = 1499 and 1113) mark-recapture study, across two successive years on a commercial river lamprey (Lampetra fluviatilis) fishery, to inform exploitation rates and the influence of conditional capture probability on expected catch-per-unit-effort (CPUE). The movements of acoustic-tagged lamprey were used to refine estimates of the number of PIT-marked individuals vulnerable to the fishery. In 2018, this increased the recapture rate estimation by 0.99% and reduced the estimated run size by 152,101 (21.6%; 95% CL, 148,683, 155,688) individuals, with corresponding values of 0.12% and 114,639 (25.0%; 95% CL, 112,900, 116,448) in 2019. Lamprey movements were similar between years, with the number of trap line encounters by individuals between trap lifts used to inform expected CPUE for each lift. Conditional capture probability was mainly dependent on environmental conditions (e.g., river flow) with most trap lifts in the expected CPUE range, although the impacts of behaviour on vulnerability to capture were difficult to disentangle. This study highlights how the incorporation of acoustic telemetry increased the accuracy of, validated, and complemented mark-recapture data, without which management decisions (e.g., quota size) would have been based upon over 100,000 more individuals (27.5% higher than the adjusted run size in 2018 and 33.3% higher in 2019), with potentially severe consequences for the population. These findings demonstrate the importance of understanding fish movement to improve and inform fishery management. The study also presents a framework to quantify conditional capture probability and its influence on CPUE; knowledge that is widely applicable across aquatic systems for management and sustainability of fisheries.

Using acoustic tracking of an anadromous lamprey in a heavily fragmented river to assess current and historic passage opportunities and prioritise remediation

AbstractAnthropogenic structures extensively fragment riverine systems, reducing longitudinal connectivity, inhibiting migration and leading to severe declines in many fish populations, especially for diadromous species. This study investigated the upstream spawning migration of anadromous river lamprey (Lampetra fluviatilis) in a heavily fragmented tributary of the Humber Estuary, the location of one of the largest UK river lamprey populations. Overall, this study quantified river lamprey migration, spawning habitat distribution and historic river levels to develop a novel empirical index to understand the impact of man‐made barriers and prioritise their remediation. Passage at all weirs only occurred during episodic high river levels, often after prolonged delays with no lamprey passing below average levels for the time of year or utilising the fish pass at the first weir (T1) at the tidal limit. Barrier passage opportunities at the first four weirs were only possible for 30.3%, 38.7%, 52.1% and 6.7% of the migration period, but were lower and severely limited in 15 of the last 21 years. In addition, more lamprey (60%, n = 18) were last detected in reaches with no spawning habitat than in spawning habitat (40%, n = 12). Given the impassibility of, and lack of retreat from, T1 to other Humber tributaries, the River Trent is currently considered an ecological trap for a large proportion of lamprey that enter from the Humber Estuary. This passage should be urgently remediated, per the prioritisation index presented here, to aid river lamprey conservation, especially given their status as a designated feature of the Humber SAC.

Sperm competition experiments reveal low prezygotic postmating isolation between parasitic and nonparasitic lamprey ecotypes.

The role of postmating sexual selection as a potential reproductive barrier in speciation is not well understood. Here, we studied the effects of sperm competition and cryptic female choice as putative postmating barriers in two lamprey ecotypes with a partial reproductive isolation. The European river lamprey Lampetra fluviatilis is anadromous and parasitic of other fish species, whereas the brook lamprey Lampetra planeri is freshwater resident and nonparasitic. We measured sperm traits in both ecotypes and designed sperm competition experiments to test the occurrence of cryptic female choice. We also performed sperm competition experiments either at equal semen volume or equal sperm number to investigate the role of sperm velocity on fertilization success. We observed distinct sperm traits between ecotypes with a higher sperm concentration and a lower sperm velocity for L. planeri compared with L. fluviatilis. The outcomes of sperm competition reflected these differences in sperm traits, and there was no evidence for cryptic female choice irrespective of female ecotype. At equal semen volume, L. planeri males had a higher fertilization success than L. fluviatilis and vice versa at equal sperm number. Our results demonstrate that different sperm traits between ecotypes can influence the male reproductive success and thus gene flow between L. planeri and L. fluviatilis. However, postmating prezygotic barriers are absent and thus cannot explain the partial reproductive isolation between ecotypes.

Lipid-related thiamine deficiency cause mortality of river lampreys (Lampetra fluviatilis) during pre-spawning fasting

River lampreys (Lampetra fluviatilis) were caught in the fall 2014 on entering the River Perhonjoki for spawning and kept at a hatchery until spawning in late spring 2015 to produce larvae for compensatory stockings. Since the lampreys died massively from early February onwards, they were investigated in March and May to clarify the cause of the deaths. The symptoms in lampreys resembled those of lipid-related thiamine (vitamin B1) deficiency of salmonines, called the M74 syndrome in the Baltic Sea area. Because the lipid content of lampreys was known to be high, thiamine concentrations were analyzed in the liver and ovulated unfertilized eggs, and the mass, length, and whole-body lipid content were also measured. The hepatic total thiamine (TotTh) concentration was significantly negatively correlated with the body lipid content and fatness index (mass to length ratio) in both females and males. In females, the hepatic TotTh concentration was less than half that in males, and the most moribund lampreys were the largest and fattiest females. Females that survived until artificial stripping of the eggs were smaller, and their hepatic thiamine concentration was higher, and the fatness index lower, than in females in March. The concentration of free thiamine in the eggs had a stronger positive correlation with the hepatic TotTh concentration than the phosphorylated thiamine derivatives and was also significantly and negatively correlated with the fatness index and mass. It was concluded that increased lipid peroxidation due to the mobilization of polyunsaturated fatty acids from lipids in exogenous vitellogenesis consumed thiamine as an antioxidant during pre-spawning fasting—especially in the fattiest females—and thus caused their death. It is suggested that to ensure compensatory stockings, the largest lampreys could be thiamine-injected at the hatchery to improve their survival until stripping of the eggs and to improve the eggs’ thiamine status.

Understanding the impact of barriers to onward migration; a novel approach using translocated fish

River catchments worldwide are heavily fragmented by anthropogenic barriers, reducing their longitudinal connectivity and contributing to the decline of migratory fish populations. Direct impacts of individual barriers on migratory fish are well-established, but barrier impacts on onward migration are poorly understood, despite their relevance to evidence-based, catchment-scale, management of threatened species. This study investigated the upstream spawning migration of 352 acoustic tagged river lamprey (Lampetra fluviatilis), translocated upstream of two key barriers (R2: n = 60 & 59; R3: n = 59 & 52) compared to a control group (R1: n = 61 & 59), across two contrasting (dry and wet, n = 180 and 172) years in the River Yorkshire Ouse, England, to reveal the impact of barriers on the onward migration of upstream migrating fish. Release further upstream increased the degree of catchment penetration, with median distance upstream of R1 56.1% and 68.6% greater for lamprey released at R2 and R3 respectively. Median delays at the two downstream-most main river barriers by the control group were 23.8 and 5.4 days (2018/19) and 9.3 and 11.4 days (2019/20). However, impacts of delay were only observed on the time to reach spawning habitat, time to reach final assumed spawning location and speed of movement in one upper catchment tributary during 2019/20 whilst they were only observed on time to reach spawning habitat during 2018/19 and on assumed spawning location distance during 2019/20 in the other. Ultimately, limited impacts of delay at barriers on onward fish migration post-passage were observed but median catchment penetration was increased with consecutive release upstream. This study demonstrated the importance of a true understanding of barrier impacts to inform catchment-wide planning, evidence vital for management worldwide. Although the findings of this study do support the use of trap and transport as a measure to remediate barrier impacts on migration, fish passage engineering improvements or barrier removal, at structures shown to be the most inhibiting to fish migration should be considered the best and most sustainable option to improve barrier passage.

The First Analysis of Synaptonemal Complexes in Jawless Vertebrates: Chromosome Synapsis and Transcription Reactivation at Meiotic Prophase I in the Lamprey Lampetra fluviatilis (Petromyzontiformes, Cyclostomata)

Transcription is known to be substage-specific in meiotic prophase I. If transcription is reactivated in the mid pachytene stage in mammals when synapsis is completed, then this process is observed in the zygotene stage in insects. The process of transcriptional reactivation has been studied in a small number of different taxa of invertebrates and vertebrates. Here, for the first time, we investigate synapsis and transcription in prophase I in the European river lamprey Lampetra fluviatilis (Petromyzontiformes, Cyclostomata), which is representative of jawless vertebrates that diverged from the main branch of vertebrates between 535 and 462 million years ago. We found that not all chromosomes complete synapsis in telomeric regions. Rounded structures were detected in chromatin and in some synaptonemal complexes, but their nature could not be determined conclusively. An analysis of RNA polymerase II distribution led to the conclusion that transcriptional reactivation in lamprey prophase I is not associated with the completion of chromosome synapsis. Monomethylated histone H3K4 is localized in meiotic chromatin throughout prophase I, and this pattern has not been previously detected in animals. Thus, the findings made it possible to identify synaptic and epigenetic patterns specific to this group and to expand knowledge about chromatin epigenetics in prophase I.

Modelling fine scale route choice of upstream migrating fish as they approach an instream structure

This study used pattern-oriented modelling (POM) to investigate the space use and behavioural response of upstream migrating European river lamprey (Lampetra fluviatilis) to the two-dimensional hydrodynamic conditions created by an instream structure (triangular profile gauging weir). Passive Integrated Transponder (PIT) and acoustic telemetry were used to map the spatial-temporal distribution patterns of lamprey as they migrated upstream. Acoustic Doppler velocimetry and computer modelling were used to quantify the hydrodynamic environment. In adherence with the POM methodology, multiple movement models, incorporating increasingly complex environmental feedback mechanisms and behavioural rules were created and systematically assessed to identify which factors might reproduce the observed patterns. The best model was a spatially explicit Eulerian-Lagrangian Individual Based Model (IBM) that included two simple behaviours: 1) tortuous non-directed swimming when in low flow velocity (< 0.1 m s−1) and 2) persistent directed (against the flow) swimming in moderate to high flow velocity (≥ 0.1 m s−1). The POM indicated that flow heterogeneity was an important influence of lamprey space use and that simple behavioural rules (i.e. two separate movement behaviours in response to flow velocity) were sufficient to reproduce the main movement pattern observed: avoidance of flow recirculating regions near the banks. The combination of field telemetry, hydrodynamic modelling and POM provided a useful framework for systematically identifying the key factors (hydrodynamic and behavioural) that governed the space use of the target species and would likely work well for investigating similar relationships in other aquatic species.

No strict host specificity: Brain metacercariae Diplostomum petromyzifluviatilis Müller (Diesing, 1850) are conspecific with Diplostomum sp. Lineage 4 of Blasco-Costa et al. (2014).

Metacercariae of Diplostomum petromyzifluviatilis (Digenea, Diplostomidae) from the brain of European river lamprey Lampetra fluviatilis from the Baltic Sea basin and Arctic lamprey Lethenteron camtschaticum from the White Sea basin were studied with the use of genetic and morphological methods. Phylogenetic analysis based on cox1 marker showed that the parasites of both lamprey species were conspecific with Diplostomum sp. Lineage 4 of Blasco-Costa et al. (2014). The name Diplostomum petromyzifluviatilis Müller (Diesing, 1850) has historical precedence as a species described from the brain of lampreys and should be used in genus nomenclature. There were no morphological qualitative differences between the metacercariae from the two lamprey species but those from L. fluviatilis were larger than those from L. camtschaticum. We expanded the data on the second intermediate hosts and the localization of D. petromyzifluviatilis, showing that its metacercariae occur not only in the brain of lampreys but also in the brain and the retina of three-spined stickleback Gasterosteus aculeatus and the vitreous humour of the perch Perca fluviatilis across the European part of the Palearctic.

A SNP marker to discriminate the european brook lamprey (Lampetra planeri), river lamprey (L. fluviatilis) and their hybrids.

The European River lamprey Lampetra fluviatilis and the brook lamprey L. planeri are two closely related species that are also considered as partially reproductively isolated ecotypes. At the larval stage, they cannot be distinguished morphologically or genetically by mitochondrial DNA. We aimed at developing a molecular tool to identify early life stages of L. fluviatilis and L. planeri. We first identified Single Nucleotide Polymorphism (SNP) markers with distinct alleles between L. fluviatilis and L. planeri based on RADseq data from 186 individuals collected in France. Then, we developed a quantitative PCR protocol to genotype a species-specific SNP, which was tested on 270 samples including larvae and adults from both species and 17 sites from Western Europe. Results were consistent with morphological identification in all cases except for samples from the Rhône drainage and the Loch Lomond in Scotland. This marker allows the identification of larval stages of L. fluviatilis, L. planeri as well as hybrids. The two cases where the marker was not diagnostic might be explained by an isolated and distinct L. planeri lineage in the Rhône drainage, and high levels of admixture among L. fluviatilis, L. planeri and the lake-parasitic form in Loch Lomond.

Realistic variations in substrate composition affect spawning preference and egg retention in river lamprey (Lampetra fluviatilis).

Egg drift from the nest is clearly an important cause of mortality in lithophilic species, but the effect of substrate composition on this process has been overlooked. Here, we investigated the role of substrate on the spawning preference and egg retention of river lamprey (Lampetra fluviatilis) during a whole breeding season in a two-option experimental setting. Despite no initial preference, the lamprey eventually favoured the most efficient substrate for egg retention. The pebbly substrate hosted 12 times as many matings as the sandy one, while blurting 20% fewer eggs.

A new element in the migration cycle of the European river lamprey Lampetra fluviatilis: downstream migration from a lake

A new element in the migration cycle of the European river lamprey Lampetra fluviatilis: downstream migration from a lake