Differential gene expression in European glass eels (Anguilla anguilla): a genetic basis of the head shape dimorphism?

In the European yellow eel stage (Anguilla anguilla), two morphotypes are found: broad- and narrow-heads. The presence of these morphotypes is related to differences in diet, with broad-heads feeding on hard prey and narrow-heads on soft prey. However, recent research showed that both morphotypes were already present at the glass eel stage, the non-feeding predecessor of the yellow eel stage, implying that other factors than trophic segregation play a role in the head shape dimorphism development. Here, we investigated the hypothesis that the head shape dimorphism has a genetic basis using RNA-seq. More specifically, we tested whether genes involved in muscle and bone development were significantly up-regulated in broad-headed glass eels, as broad-heads have larger muscles to increase bite force. We found that 260 genes were significantly differential expressed between both morphotypes. None of these genes were, however, related to bone or muscle development. Next to this, no pathways were enriched between the two morphotypes. Interestingly, genes involved in growth (soma and igf2) were up-regulated in narrow-heads, while also 9 genes involved in chemotaxis showed significant differential expression. Our study found support for the observation that head shape is influenced by somatic growth, with fast-growing eels developing a narrow head and vice versa. Next to this, observations in the wild showed that slow-growers prefer freshwater, while fast-growers prefer brackish water. The differential expression of genes involved in chemotaxis indeed seems to indicate that growth rate and habitat choice are related to each other. This let us to hypothesize that two segregations take place in the European eel, strongly decreasing intraspecific competition: first according to habitat choice, second according to feeding preference.

Jaar van publicatie:2015