Gene expression response to a nematode parasite in novel and native eel hosts

Invasive parasites are involved in population declines of new host species worldwide. The high susceptibilities observed in many novel hosts have been attributed to the lack of protective immunity to the parasites which native hosts acquired during their shared evolution. We experimentally infected Japanese eels (Anguilla japonica) and European eels (Anguilla anguilla) with Anguillicola crassus, a nematode parasite that is native to the Japanese eel and invasive in the European eel. We inferred gene expression changes in head kidney tissue from both species, using RNA‐seq data to determine the responses at two time points during the early stages of infection (3 and 23 days postinfection). At both time points, the novel host modified the expression of a larger and functionally more diverse set of genes than the native host. Strikingly, the native host regulated immune gene expression only at the earlier time point and to a small extent while the novel host regulated these genes at both time points. A low number of differentially expressed immune genes, especially in the native host, suggest that a systemic immune response was of minor importance during the early stages of infection. Transcript abundance of genes involved in cell respiration was reduced in the novel host which may affect its ability to cope with harsh conditions and energetically demanding activities. The observed gene expression changes in response to a novel parasite that we observed in a fish follow a general pattern observed in amphibians and mammals, and suggest that the disruption of physiological processes, rather than the absence of an immediate immune response, is responsible for the higher susceptibility of the novel host

Molecular characterization of MHC class IIB genes of sympatric Neotropical cichlids

Ministerio de Economía y Competitividad del Gobierno de España, Programa de Formación de Personal Investigador FPI BES-2011-047645 to MJH, Programa Estatal de Fomento de la Investigación Científica y Técnica de Excelencia Proyecto CGL 2010-16103 to MB. This project was further enabled through two German Science Foundation grants to CE (DFG, EI841/4-1 and EI841/6-1) both part of the SPP 1399 priority programme on “host-parasite interactions”

Evolution of MHC IIB Diversity Across Cichlid Fish Radiations

The genes of the major histocompatibility complex (MHC) are among the most polymorphic genes in vertebrates and crucial for their adaptive immune response. These genes frequently show inconsistencies between allelic genealogies and species phylogenies. This phenomenon is thought to be the result of parasite-mediated balancing selection maintaining ancient alleles through speciation events (trans-species polymorphism [TSP]). However, allele similarities may also arise from postspeciation mechanisms, such as convergence or introgression. Here, we investigated the evolution of MHC class IIB diversity in the cichlid fish radiations across Africa and the Neotropics by a comprehensive review of available MHC IIB DNA sequence information. We explored what mechanism explains the MHC allele similarities found among cichlid radiations. Our results showed extensive allele similarity among cichlid fish across continents, likely due to TSP. Functionality at MHC was also shared among species of the different continents. The maintenance of MHC alleles for long evolutionary times and their shared functionality may imply that certain MHC variants are essential in immune adaptation, even in species that diverged millions of years ago and occupy different environments.Funding was provided by Spanish Ministry of Science and Innovation (MCIN)/Spanish Research Agency (AEI) and European Regional Development Fund (ERDF) “A way to make Europe” through projects CGL2017-82986-C2-1-P and PID2020-115481GB-I00 to M.B. C.L.M. was supported by a predoctoral fellowship from MCIN/AEI and European Social Funds (FPI-PRE2018-085797). S.E.B. was supported by a Swiss National Science Foundation Early PostDoc.Mobility fellowship (P2SKP3_191312) and a Juan de la Cierva training contract from MCIN/AEI and NextGeneration EU/PRTR (FJC2020-042779-I).Peer reviewe

Characterization of MHC class II genes in the critically endangered European eel (Anguilla anguilla)

Many exploited fish species are threatened with collapse and the European eel is no exception. Its abundance has declined dramatically and various reasons account for this, among them the introduction of the invasive swim bladder nematode Anguillicola crassus. For developing an adequate immune response against this parasite, variation at the genes of the major histocompatibility complex (MHC), a key component of the adaptive immune system, might be essential and assessing their diversity might provide critical information for improving conservation strategies. Here, we characterized the MHC class II of the European eel. We provide evidence for relatively high diversity at both MHC IIA and MHC IIB, which contrasts with findings for other endangered species. Furthermore, both genes show signs of site-specific positive selection. The absence of overall positive selection at MHC IIB might, however, suggests that demographic shifts have negatively impacted that gene, thereby possibly reducing the adaptive potential of the European eel

MHC evolution in the Neotropical the Midas cichlid

Este seminario tuvo lugar en Las Caldas (Oviedo) del 18 al 20 de enero de 2023The antagonistic interaction between hosts and parasites is recognized as one major driver of animal diversification. Parasites impose strong selective pressures on their hosts, which induce immune responses that have the potential to cause local adaptation in host populations, and ultimately diversification and even speciation. The adaptive immune response is partly mediated by the Major Histocompatibility Complex (MHC), a gene family which represents one of the most variable genomic regions in vertebrates. MHC variability is generated, to some extent, by parasite diversity and maintained by balancing selection resulting from the interplay between MHC and parasites. Hosts inhabiting alternative habitats are exposed to different parasite communities, and these contrasting pressures should generate MHC heterogeneity and local signatures across host populations. Here we studied the role of host-parasite interactions in generating diversity in the recent adaptive radiation of The Midas cichlid fish (Amphilophus spp.) in the Nicaraguan lakes. Sympatric Midas cichlid species have evolved in parallel in different lakes adapting to exploit alternative habitats and trophic resources. Parallelism is also reflected in phenotypic variation affecting body shape and trophic structures. We already recognized that there is a lake-specific MHC signature. Here we analyzed MHC variation across Midas cichlid species and populations and evaluated MHC signatures associated to parallel ecotypes. Moreover, we analyzed temporal variability of MHC population signatures. We compare this data with parasite communities and their temporal variabilit

Programa y Libro de Resúmenes de las VI Jornadas Científicas del Museo Nacional de Ciencias Naturales (MNCN-CSIC)

Las VI Jornadas Científicas del Museo Nacional de Ciencias Naturales (MNCN-CSIC) fueron celebradas el 17 y 18 de abril de 2023 en Madrid. En ellas tuvieron lugar 3 sesiones plenarias de 45 minutos, 21 charlas de 15 minutos y 31 charlas de 5 minutos. Finalizaron con mesa redonda sobre "El futuro de la carrera investigadora en el Museo".Peer reviewe

Data from: Gene expression response to a nematode parasite in novel and native eel hosts

Invasive parasites are involved in population declines of new host species worldwide. The high susceptibilities observed in many novel hosts have been attributed to the lack of protective immunity to the parasites which native hosts acquired during their shared evolution. We experimentally infected Japanese eels (Anguilla japonica) and European eels (A. anguilla) with Anguillicola crassus, a nematode parasite that is native to the Japanese eel and invasive in the European eel. We inferred gene expression changes in head kidney tissue from both species, using RNA-seq data to determine the responses at two time points during the early stages of infection (3 and 23 days post-infection). At both time points, the novel host modified the expression of a larger and functionally more diverse set of genes than the native host. Strikingly, the native host regulated immune gene expression only at the earlier time point and to a small extent while the novel host regulated these genes at both time points. A low number of differentially expressed immune genes, especially in the native host, suggests that a systemic immune response was of minor importance during the early stages of infection. Transcript abundance of genes involved in cell respiration was reduced in the novel host which may affect its ability to cope with harsh conditions and energetically demanding activities. The observed gene expression changes in response to a novel parasite that we observed in a fish follow a general pattern observed in amphibians and mammals, and suggest that the disruption of physiological processes, rather than the absence of an immediate immune response, are responsible for the higher susceptibility of the novel host