Immunological tolerance in the evolution of male pregnancy

The evolution of the unique syngnathid male pregnancy has resulted in an array of different brooding types ranging from basic attachment of eggs (pouch-less species: Nerophinae) to specialized internal gestation in pouched species (e.g. Syngnathus and Hippocampus) with many transitions in between. As such it offers a unique platform for assessing adaptations in pregnancy evolution to answer long-standing questions of why and how pregnancy evolved convergently in so many vertebrate systems. To understand the molecular congruencies and disparities in male pregnancy evolution, we compared transcriptome-wide differentially expressed genes in four syngnathid species, at four pregnancy stages (non-pregnant, early, late and parturition).