Infection affects guppy reproductive fitness and offspring parasite resistance

Infection imposes energetic costs on hosts. Hosts typically respond by shifting resources, potentially affecting the quantity and quality of offspring they produce. As the sexes differ in their optimal reproductive strategies, infection of mothers versus fathers may affect offspring quantity and quality in different ways. Here, we test how experimental infection of guppies Poecilia reticulata with the ectoparasite Gyrodactylus turnbulli affects parental reproductive fitness and the parasite resistance of offspring. We compared breeding pairs in which one or neither parent had previously been infected. Parental infection did not affect the size, body condition, or number of offspring produced, but previously infected mothers had 35-39% longer latency to birth. However, offspring of infected mothers experienced 105 fewer worm days than those of infected fathers: fathers, but not mothers, that experienced heavy infections themselves produced offspring that also experienced heavy infections. The parent-offspring regression for infected fathers is therefore consistent with previous evidence that parasite resistance is heritable in this system, whereas that among mothers provides novel insight that mothers may engage in transgenerational immune priming. The sexes may thus strike a different balance between offspring quantity and quality when faced with infection, with potentially broad implications for disease and population dynamics. ### Competing Interest Statement The authors have declared no competing interest.