Dataset Information

Invasion genetics of the mummichog (Fundulus heteroclitus): recent anthropogenic introduction in Iberia.

ABSTRACT: Human activities such as trade and transport have increased considerably in the last decades, greatly facilitating the introduction and spread of non-native species at a global level. In the Iberian Peninsula, Fundulus heteroclitus, a small euryhaline coastal fish with short dispersal, was found for the first time in the mid-1970s. Since then, F. heteroclitus has undergone range expansions, colonizing the southern region of Portugal, southwestern coast of Spain and the Ebro Delta in the Mediterranean Sea. Cytochrome b sequences were used to elucidate the species invasion pathway in Iberia. Three Iberian locations (Faro, Cádiz and Ebro Delta) and 13 other locations along the native range of F. heteroclitus in North America were sampled. Results revealed a single haplotype, common to all invasive populations, which can be traced to the northern region of the species' native range. We posit that the origin of the founder individuals is between New York and Nova Scotia. Additionally, the lack of genetic structure within Iberia is consistent with a recent invasion scenario and a strong founder effect. We suggest the most probable introduction vector is associated with the aquarium trade. We further discuss the hypothesis of a second human-mediated introduction responsible for the establishment of individuals in the Ebro Delta supported by the absence of adequate muddy habitats linking Cádiz and the Ebro Delta. Although the species has a high tolerance to salinity and temperature, ecological niche modelling indicates that benthic habitat constraints prevent along-shore colonisation suggesting that such expansions would need to be aided by human release.

SUBMITTER: Morim T

PROVIDER: S-EPMC6369826 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Invasion genetics of the mummichog (Fundulus heteroclitus): recent anthropogenic introduction in Iberia.

Morim Teófilo T Bigg Grant R GR Madeira Pedro M PM Palma Jorge J Duvernell David D DD Gisbert Enric E Cunha Regina L RL Castilho Rita R

PeerJ 20190208

Human activities such as trade and transport have increased considerably in the last decades, greatly facilitating the introduction and spread of non-native species at a global level. In the Iberian Peninsula, Fundulus heteroclitus, a small euryhaline coastal fish with short dispersal, was found for the first time in the mid-1970s. Since then, F. heteroclitus has undergone range expansions, colonizing the southern region of Portugal, southwestern coast of Spain and the Ebro Delta i ...[more]

PMID: 30775165

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Project description:The objective of this study was to gain mechanistic insight into how mummichog are able to produce eggs during exposures to high levels of EE2. Mummichog were exposed to 0, 50 or 250 ng/L of EE2 for 14 d. A mummichog microarray was used to identify genomic responses associated with high EE2 exposure, and effects of EE2 on target genes involved in lipid mobilization and transport and steroidogenesis, two important (EE2 regulated) pathways involved in egg production, were measured using real-time PCR. In addition, changes at higher level biological endpoints such as plasma steroid production and gonad morphology were measured to examine downstream responses to EE2. There were no differences in gonadosomatic index, liversomatic index, gonad development, or plasma estradiol levels after exposure to EE2, although testosterone decreased with EE2 exposures. Similar to other species, mummichog showed alterations to plasma steroid levels, and similar processes at the molecular level were identified as being altered by EE2, including cell processes associated with lipids. However, unlike other species, mummichog showed no differences in GSI or ovarian development. Fatty acids were affected at both the transcript and translation level, which suggests they are a major target of estrogens. Lipids are important for both growth and reproduction, and provide oocytes with nutrients. Interestingly, mummichog showed no effect on apolipoprotein expression, which is important in lipid transport. Therefore, it is hypothesized that mummichog are normally able to transport lipids for energy and nutrients to the ovary, while this is affected in other species. Novel gene regulatory networks for protein modification targets were also constructed to learn more about the potential roles of estrogens in the teleost liver. Although post-translational modifications (PTMs) are important regulatory mechanisms, the roles of PTMs in protein regulation in fish and the susceptibility of PTMs to aquatic pollutants are largely unexplored and may offer novel insight into mechanisms of endocrine disruption.

Project description:To better assess the impact of contaminants on fish reproduction, it is increasingly important to collect data at multiple levels of biological organization. However, a challenge in ecotoxicology is that three of the most commonly measured reproductive endpoints; gonad histology, ex vivo steroid production, and gene expression, can be difficult to obtain in small-bodied fish (e.g. zebrafish, Japanese medaka, fathead minnow) due to limited tissue availability. Using 5α-dihydrotestosterone (DHT) as a test compound, the objectives of the current study were to assess the feasibility of measuring gene expression in tissues also used for ex vivo steroid production studies. A portion of the testes was also used for qualitative histological examination. Male mummichog were exposed to 0, 5, and 50 µg/L DHT for 21 days. Following the exposure, testes were collected and separated into three pieces for histology, ex vivo incubation to measure steroidogenic capacity [Testosterone(T), 17β-estradiol (E2), 11-ketotestosterone (11KT)] and gene expression analyses. Testis RNA at time of dissection and testis RNA at end of ex vivo incubation (18 h) was collected and assessed for RNA integrity. The expression of genes coding for estrogen receptor βa (esrba) and estrogen receptor βb (esrbb) as well as the key steroidogenic genes, steroidogenic acute regulatory protein (star), P450 side chain cleavage (p450scc) and 11β-hydroxysteroid dehydrogenase (hsd11b3) were assessed in testis before and after ex vivo incubation. There were no significant differences in RNA quality between the two time points, however the expression of esrba, esrbb and p450scc was significantly lower post-incubation, although star, hsd11b3, and all four reference gene expression levels remained unchanged over time. DHT did not affect the expression of any of the measured genes at either concentration. Histological examination showed that all fish contained mature testes dominated by spermatozoa and spermatids. DHT did not affect T production but significantly decreased 11KT production in the high treatment group. This suggests a role for DHT in androgen regulation, and has

Dataset Information

Invasion genetics of the mummichog (Fundulus heteroclitus): recent anthropogenic introduction in Iberia.

Publications

Invasion genetics of the mummichog (<i>Fundulus heteroclitus</i>): recent anthropogenic introduction in Iberia.

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