Evolution of male pregnancy associated with remodeling of canonical vertebrate immunity in seahorses and pipefishes

A fundamental problem for pregnancy to evolve nant species were identified in both genera of the syngnathids: The is inadvertent rejection of the embryo when being recognized as pipefishes (Syngnathus) displayed loss of several genes of the MHC foreign tissue by the vertebrate’s adaptive immune system. [...] Morphology of brood pouches of subfamily Nerophinae (A), and of the genera Syngnathus (B), and Hippocampus (C) and display of the placenta-like structures in syngnathids (only Syngnathus and Hippocampus). [...] This is A closer examination of the invariant chain encoding gene supported by a loss of CD4, mediating successful receptor binding CD74 also suggests that the evolution of adaptive immunity has and activation of CD4+ T lymphocytes—AICDA, responsible for taken distinct routes in the two sister genera Syngnathus and the unique receptor diversity of the antibodies and CIITA, the Hippocampus. [...] While subsequently several core genes of In Gadiformes (cod-like fishes) an independent loss of the MHC the MHC II pathway were lost in Syngnathus, genes of the MHC class II pathway was recently reported, and the observed di- II pathway were under positive selection in Hippocampus [Fig. [...] The expanded MHC I repertoire is likely to be linked investigation of the molecular basis of male pregnancy evolution to the simultaneous loss/rearrangement of the MHC II pathway and its mechanistic similarity to female pregnancy in the future.