Earlier sex change in infected individuals of the protogynous reef fish Thalassoma bifasciatum

Abstract

Sex allocation theory for sequential hermaphrodites predicts the size at which an individual should change sex, given the different relationships between individual size and reproductive success in the two sexes. We studied a host-parasite system where the myxozoan Kudoa ovivora infects the ovaries of the reef fish Thalassoma bifasciatum, a protogynous sequential hermaphrodite. The parasite sporulates in the host's eggs and renders them infertile. It is thus expected to reduce the female's reproductive success, and could thereby influence host sex change. We present data from marked fish we observed in the field over 4 months. The data suggest that females infected with Kudoa ovivora have a lower reproductive success, change sex earlier and at a smaller size than uninfected females. These results are in agreement with predictions from sex allocation theory, and provide the first example of a possible parasitic influence on the sex allocation of its host.

Kudoa saudiensis sp. n. (Myxosporea: Multivalvulida) infecting oocytes of the Indian mackerel Rastrelliger kanagurta (Perciformes: Scombridae)

“…Moreover, in the sequential hermaphrodite, the fish Thalassoma bifasciatum (Bloch), K. ovivora influences sex allocation of its host. Thus, it was suggested that females infected by this parasite not only have a lower reproductive success, but also change sex earlier and at a smaller size than uninfected ones (Schärer and Vizoso 2003). Such situation could also lead to a quick loss of the parasite as the ovarian tissue will be replaced by testes.…”

Specificity of Infection Sites in Vertebrate Hosts

“…Females of Thalassoma bifasciatum with Kudoa ovivora infections in the ovary change sex earlier and at a smaller size, thus gaining a reproductive advantage. Such sex change represents 'host death' from the parasite's point of view, as the host tissue required for sporogony disappears (Schärer and Vizoso 2003).…”

Sex change in plants and animals: a unified perspective

“…Animals and plants live in complex environments in which they interact with many organisms both antagonistically and mutualistically, and this is an underexplored factor of sex change especially in animals (e.g. Schärer & Vizoso, ). In plants, it has been suggested that antagonistic and mutualistic interactions play an important role in the evolution and maintenance of unisexuality (Vega‐Frutis et al ., ), but sex change has received little attention in this context (Audran & Batcho, ).…”