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Regulation of immunocompetence by different androgen metabolites in a blenny with alternative reproductive tactics
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Abstract(s)
In Parablennius parvicornis, small reproductive males with relatively low
expression of secondary sexual characters (M morphotype) parasite on the parental investment
of the larger nest-holder males which have fully developed secondary sexual characters
(M1 morphotype). In comparison with M1 males, M males have relatively low levels of androgens
while having high blood cell percentages of lymphocytes and antigen responsiveness. Here we test
the hypothesis that androgens are a causal factor for these differences in immunocompetence
between morphotypes. After drawing an initial blood sample, males received a silastic implant
containing either oil only (C), or oil with testosterone (T) or 11-ketotestosterone (KT). Males were
re-caught 2 weeks later for drawing of the final blood sample. KT but not T induced the development
of secondary sexual characters in M males. M males treated with KT showed lower swimming
activity than the males treated with T or C implants, suggesting that KT also mediates behavioral
changes in M males. As expected, blood cell percentages of lymphocytes, but not of granulocytes,
were higher in M males than in M1 males. Overall, lymphocyte percentages increased in the
C group which might have been a response to the surgery/treatment. In concordance with the
hypothesis, lymphocyte percentages were suppressed in males treated with T in comparison
with controls. However, no significant change was found in KT-treated males. This suggests that
androgens modulate central, morphological and immunological traits by partly independent
androgen mechanisms in P. parvicornis.
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Citation
Journal of Experimental Zoology, 305A, 986-994