[vc_row][vc_column width=”1/1″][vc_button title=”Description en français ici !” target=”_self” color=”btn-danger” icon=”none” size=”wpb_regularsize” href=”http://www.sciences-unamur.be/bio/system-ecotox/?p=2147″][vc_button title=”Photos here !” target=”_self” color=”btn-success” icon=”none” size=”wpb_regularsize” href=”http://www.sciences-unamur.be/bio/system-ecotox/gallery/mangrove-rivulus-kryptolebias-marmoratus/”][vc_column_text]
At a first glance, mangrove rivulus appears like ordinary fish. However, this species possesses an extraordinary life-history that has been the subject of interest of many scientists since its discovery.
The mangrove rivulus, Kryptolebias marmoratus, is found over a huge geographic range, comprising the coastal lines of Central America, Southern North America to the mouth of Amazon River in South America. It is closely affiliated with the red mangrove Rhizophora mangle.
Major habitats of mangrove rivulus are burrows excavated by land crabs. The abiotic conditions in the burrows are highly variable, fluctuating with tides, weather and seasons. They’re characterized by generally low dissolved oxygen, high levels of hydrogen sulfide from rotting mangrove leaves and a fluctuating salinity.
The first amazing fact about this fish is that they are not bothered at all by these harsh conditions. When the conditions become too extreme, they even emerse and they are able to live out of water for more than 2 months. The cues that trigger emersion are high levels of H2S, low dissolved O2, hunger, drought, or agression from other fish. They stay in moist leaf litter or in insect tunnels within rotting logs. While out of water, the skin takes the function of the gills : dense networks of blood vessels below the surface of the skin allows the uptake of oxygen. This species displays thus high levels of phenotypic plasticity, which is the fact that a given genotype can lead to different phenotypes depending on the environmental conditions.
The second surprising fact is their mode of reproduction. They are the only vertebrates known to be hermaphrodites and able to self-fertilize. Long bouts of self-fertilization lead to genetically identic homozygous lineages. Males occur in some populations, allowing some sexual outcrossing with hermaphrodites and increasing genetic diversity. There is no female. The simultaneous occurance of males and hermaphrodites is called androdioecy.
For these two reasons, the mangrove rivulus provides an excellent model for the study of phenotypic plasticity. First, we can probably get more information about a species able to survive at the limits of tolerance (showing a high phenotypic plasticity) than one tolerating a narrow range of environmental conditions. Second, the avaibility of isogenic lineages eliminates the effect of genetic variability when looking at the effects of the environment on the phenotype.
The general objective of this research is to explore the epigenetic regulation mechanisms (mostly DNA methylation), to caracterize its epigenome in different organs and individuals (males and hermaphrodites) as well as along the first stages of embryogenesis. This amazing fish permits to focus on te “true” phenotypic plasticity, relying on the absence of genetic diversity (and probably on epigenetic diversity instead). We will also investigate how its epigenome is affected by the exposure of endocrine disrupting chemicals during the early life stages (developmental plasticity) and in adults (phenotypic flexibility). Moreover, we will anchor the phenotypic response at the organism level (physiology and behavioral traits) to the cellular phenotype assessed at the proteomic level. Altogether this project will deepen our understanding on how epigenetics can explain phenotypic plasticity in the absence of genetic diversity in a vertebrate species.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/1″][vc_column_text]Press article published in 2007 in Reuters here.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/1″][vc_button title=”Restricted area” target=”_self” color=”btn-inverse” icon=”wpb_chart” size=”wpb_regularsize”][/vc_column][/vc_row]