The effects of microplastics on autografts and allografts in Poecilia reticulata

Abstract Over half of the microplastics found in the ocean are polystyrene - this impacts naturally harvested fish and shellfish in those environments. Recent studies have shown that, in fish, polystyrene microplastics affect growth, development, chemical responses, and digestive contents. Microplastics are not directly immunogenic, but can increase general inflammatory signaling due to tissue damage - fish are particularly sensitive to this type of damage because their respiratory and digestive systems are in constant interaction with the aquatic environment. This study addresses the effects of varying concentrations of polystyrene microplastics on the immune response to scale autografts and allografts in Poecilia reticulata (guppy fish). Tank conditions with microplastic concentrations of 0 particles/m3, 2,500 particles/m3, 10,000 particles/m3, and 80,000 particles/m3 were used to represent the range of natural environments with 4 fish per treatment group. Each individual fish underwent bilateral scale grafts, with autografts on one side and genetically distinct allografts on the other side. Genetic differences were confirmed based on genotyping the UBA locus - representative of MHC class I. Post-surgical graft monitoring used necrosis and pigment loss as markers of chronic rejection and vascular development as a marker of graft success. Chronic rejection based on genetic differences is observable in the differential success of autografted and allografted scale tissues.