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

摘要

In the Azorean rock-pool blenny (Parablennius parvicornis) reproductively active males display alternativemorphotypes, 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 tospawn.MCmales holding nests court females and care for the eggs. Males with low expression of SSC, theMK morphotype, have low levels of androgens and reproduce by stealing fertilizations from the MCmales. Based on the hypothesis that androgens are immunosuppressive, we expected these morphotypes todiffer in immunocompetence. To test this hypothesis, we conducted a field study in which we collectedrepeated blood samples to monitor leukocyte populations (blood smears), and to measure the primaryantibody 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 MCmales than in MK males. Neither granulocyte nor thrombocyte counts did covariate with androgens ormale tactic. In contrast, lymphocyte counts and humoral antibody response were negatively correlated withbody size, and as expected, both were lower in MC than in MK males. Interestingly, in MC malesandrogen levels decreased after immunization, and this was less in nest-holder males than in MC malesthat were floating around in the pools. Within each morphotype we found no relationship betweenandrogens and immunocompetence. The latter result is not supportive for androgen regulatedimmunosuppression 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 aconsequence of high infection rate because of such injuries.