Den Finkenbach wieder besucht – wie lange dauert das Larvalstadium des Bachneunauges Lampetra planeri (Bloch, 1784)?

Im November 1989 und von März bis November 1990 wurden im Finkenbach im hessischen Odenwald monatlich Larven des Bachneunauges Lampetra planeri gefangen und vermessen. Ziel war es, anhand von Längenfrequenzen die Anzahl von Altersklassen und damit die Dauer des Larvalstadiums bestimmen zu können. Anhand einer visuellen Analyse der Längenverteilungen wurde 1990 auf eine Dauer des Larvalstadiums von etwas über sechs Jahren, in einigen Fällen vielleicht auch ein Jahr länger, geschlossen. Die 1989/90 erhobenen Daten wurden 2020 mittels generalisierter additiver Modelle erneut ausgewertet. Anhand des Akaike-Informationskriteriums wurde für jeden Monat das Modell bestimmt, das die Anzahl vorhandener Größenklassen am besten beschrieb. Mit diesen Modellen konnten die Einschätzungen von 1990 im Wesentlichen bestätigt werden. Allerdings ist die Annahme, dass das Larvalstadium etwas über sechs Jahre dauert, mit großen Unsicherheiten behaftet. Die Anzahl von Larven in den höheren Längenbereichen ist zu gering, um hier robuste Schlüsse zur Anzahl von Größen- und damit Altersklassen zuzulassen. Weiterhin ist bei anderen Neunaugenarten auch experimentell nachgewiesen, dass die Metamorphose in einem unterschiedlichen Alter einsetzen kann. Das Wachstum von Neunaugenlarven und damit das Alter, in dem die Metamorphose einsetzt, ist von den Verhältnissen in den Gewässern abhängig. Daher wäre es interessanter, den Einfluss von Umweltbedingungen auf das Wachstum in einer Zeit des Klimawandels zu untersuchen, anstatt sich nur auf die Frage des Zeitpunkts der Metamorphose zu beschränken. Finkenbach revisited – how long is the duration of larval life in the Brook Lamprey? Abstract: In November 1989 and from March to November 1990, larvae of the brook lamprey Lampetra planeri were caught and measured monthly in the Finkenbach-River in the Hessian Odenwald in Germany. The aim was to analyse length frequencies to determine the number of age cohorts and thus the duration of the larval life. Based on a purely visual analysis of the length distributions, it was concluded that the larval life lasted a little over six years, and in some cases perhaps a year longer. The data collected in 1989/90 were re-analysed in 2020 with generalized additive models. Using the Akaike information criterion, the model that best described the number of existing size classes was determined for each month. With these models, the assessment was similar compared to the visual analysis in 1990. However, the assumption that the larval stage lasts a little over six years includes a high degree of uncertainty. The number of larvae in the higher length ranges is too low to allow robust conclusions about the numbers of size-cohorts and thus age groups. Furthermore, it has been experimentally shown in other lamprey species that metamorphosis can begin at different ages. The growth of lamprey larvae and thus the age at which they enter metamorphosis depends on environmental conditions. Therefore, it would be more interesting to examine the influence of these conditions on growth in a time of global warming, instead of restricting analyses to the question of the exact age of metamorphosis.

Cytidine deaminase 2 is required for VLRB antibody gene assembly in lampreys

The antibodies of jawless vertebrates consist of leucine-rich repeat arrays encoded by somatically assembled VLRB genes. It is unknown how the incomplete germline VLRB loci are converted into functional antibody genes during B lymphocyte development in lampreys. In Lampetra planeri larvae lacking the cytidine deaminase CDA2 gene, VLRB assembly fails, whereas the T lineage–associated VLRA and VLRC antigen receptor gene assemblies occur normally. Thus, CDA2 acts in a B cell lineage–specific fashion to support the somatic diversification of VLRB antibody genes. CDA2 is closely related to activation-induced cytidine deaminase (AID), which is essential for the elaboration of immunoglobulin gene repertoires in jawed vertebrates. Our results thus identify a convergent mechanism of antigen receptor gene assembly and diversification that independently evolved in the two sister branches of vertebrates.

Riverscape genetics in brook lamprey: genetic diversity is less influenced by river fragmentation than by gene flow with the anadromous ecotype

Understanding the effect of human induced landscape fragmentation on gene flow and evolutionary potential of wild populations has become a major concern. Here, we investigated the effect of riverscape fragmentation on patterns of genetic diversity in the freshwater resident brook lamprey (Lampetra planeri) that has a low ability to pass obstacles to migration. We also tested the hypotheses of i) asymmetric gene flow following water current and ii) admixture with the closely related anadromous L. fluviatilis ecotype having a positive effect on L. planeri genetic diversity. We genotyped 2472 individuals, including 225 L. fluviatilis, sampled in 81 sites upstream and downstream from barriers to migration, in 29 West-European rivers. Linear modelling revealed a strong positive relationship between the distance to the source and genetic diversity, consistent with expected patterns of decreased gene flow into upstream populations. However, the presence of anthropogenic barriers had a moderate effect on spatial genetic structure. Accordingly, we found evidence for downstream-directed gene flow, supporting the hypothesis that barriers do not limit dispersal following water flow. Downstream L. planeri populations in sympatry with L. fluviatilis displayed consistently higher genetic diversity. We conclude that genetic drift and slight downstream gene flow mainly drive the genetic make up of upstream L. planeri populations whereas admixture between ecotypes maintains higher levels of genetic diversity in L. planeri populations sympatric with L. fluviatilis. We discuss the implications of these results for the design of conservation strategies of lamprey, and other freshwater organisms with several ecotypes, in fragmented dendritic river networks.

New southernmost record of the European Brook Lamprey, Lampetra planeri (Bloch, 1784) (Agnatha, Petromyzontidae)

We report the occurrence of the European Brook Lamprey, Lampetra planeri (Bloch, 1784), in the Lao river in the Calabria region (southern Italy). This record extends the species’ known distribution limit southwards. Information regarding some morphometric and ecological data are provided and discussed.

Perspectives of D1 dopamine antagonists using in treatment of nervous and psychic disorders with (+)-SCH-23390 as an example

The effect of dopamine (DA), its agonists and antagonists on the amplitude of GABA-activated currents of isolated multipolar spinal cord neurons (both motoneurons and interneurons) of larva of the lamprey Lampetra planeri by means of patch-clamp method in the whole cell configuration was studied. (+)-SCH-23390, a D1-DA receptors antagonist was shown to block dopamine effects on GABA-activated currents by 63.0 ± 4.7 % and by 77.1 ± 2.0 %. Effects of (-)quinpirol, a D2-DA receptors agonist, on GABA-activated currents were blocked by means of (+)-SCH-23390 by 78.8 ± 0.4 % and by 85.0 ± 5.7 %. Because of chemoactivated currents are in full accordance with a gradual scale, the results on blocking D1-DA receptors by (+)-SCH-23390 are ideal ones and that is the possible basis to further clinical aprobation of (+)-SCH-23390 for treatment of epilepsy, neurotic reactions and depression.