Fitness costs associated with maternal immune priming in the oyster.

Maternal immune priming is the transfer of immunity from mother to offspring, which may reduce the offspring's risk of disease from a pathogen that previously infected its mother. Maternal immune priming has been described in at least 25 invertebrate taxa, including Crassostrea gigas. Larvae of C. gigas have improved survival to Ostreid herpesvirus (OsHV-1) if their mothers are either infected with OsHV-1 or were injected with a virus mimic called poly(I:C). However, fitness costs associated with maternal immune priming in C. gigas are unknown. Here, we show C. gigas larvae produced from poly(I:C)-treated mothers are smaller, and have higher total bacteria and Vibrio loads compared to control larvae. These results suggest that the improved offspring survival of C. gigas to OsHV-1 due to maternal immune priming with poly(I:C) is potentially traded off with other important life history traits, such as larval growth rate and destabilisation of the microbiome. • Fitness costs associated with maternal immune priming using a viral mimic (poly(I:C)) was investigated in Crassostrea gigas. • Maternal immune priming reduced the size of C. gigas offspring. • Maternal immune priming altered the microbiome of C. gigas offspring. • Offspring from poly(I:C)-primed mothers had higher abundance of Vibrio sp. [ABSTRACT FROM AUTHOR]