Alternative male reproductive tactics and the immunocompetence handicap in the azorean rock-pool blenny, Parablennius parvicornis

Ros, Albert F. H.; Bouton, Niels; Santos, Ricardo Serrão; Oliveira, Rui Filipe

http://hdl.handle.net/10400.12/1301

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Authors

Ros, Albert F. H.

Bouton, Niels

Santos, Ricardo Serrão

Oliveira, Rui Filipe

Abstract(s)

In the Azorean rock-pool blenny (Parablennius parvicornis) reproductively active males display alternative morphotypes, which differ in the expression of secondary sexual characters (SSC). Males expressing SSC, theMCmorphotype, have high androgen levels and compete for crevices that will be visited by females to spawn.MCmales holding nests court females and care for the eggs. Males with low expression of SSC, the MK morphotype, have low levels of androgens and reproduce by stealing fertilizations from the MC males. Based on the hypothesis that androgens are immunosuppressive, we expected these morphotypes to differ in immunocompetence. To test this hypothesis, we conducted a field study in which we collected repeated blood samples to monitor leukocyte populations (blood smears), and to measure the primary antibody response of males that were experimentally challenged with a foreign non-pathogenic antigen (sheep red blood cells). Circulating levels of 11-ketotestosterone and testosterone were higher in MC males than in MK males. Neither granulocyte nor thrombocyte counts did covariate with androgens or male tactic. In contrast, lymphocyte counts and humoral antibody response were negatively correlated with body size, and as expected, both were lower in MC than in MK males. Interestingly, in MC males androgen levels decreased after immunization, and this was less in nest-holder males than in MC males that were floating around in the pools. Within each morphotype we found no relationship between androgens and immunocompetence. The latter result is not supportive for androgen regulated immunosuppression in MC males. A possible alternative is enhancement of immunity in MK males. These males had relatively high levels of injuries in comparison withMCmales. High immunity might be a consequence of high infection rate because of such injuries.