Endocrine correlates of male polymorphism and alternative reproductive tactics in the Azorean rock-pool blenny, Parablennius sanguinolentus parvicornis

In the Azorean rock-pool blenny male sexual polymorphism occurs, Larger and older males (M+ males) fully express male secondary sex characters (SSC), particularly an anal gland that produces a sex pheromone, whereas smaller a nd younger sexually active males do not express SSC (M- males). Two mating tactic types can be identified among M+ males: nest-holders that establish nests and court females and floaters that move around in the breeding area and try to achieve parasitic fertilizations and/or to take over nests. Two behavioral tactic types can also be identified within M- males: satellites that are associated with particular nests and ac tively participate in terr itorial defense (when females go inside the nest to spawn they try to enter to fertilize some of the eggs) and sneakers that do not help nest holders (when spawning occurs they also try to enter the nest to fertilize eggs). I t was found that M+ males have significantly higher levels of 11-ketotestos terone (KT), but not testosterone (T), than M- males [M+ male androgen leve ls (mean +/- SE): total T = 11.6 +/- 3.0 ng ml(-1), total KT = 4.5 +/- 1.1 ng ml(-1); M- male androgen levels (mean +/- SE): total T = 9.6 +/- 1.0 ng ml(-1), total KT 2.5 +/- 1.1 ng ml(-1)]. There were no differences in plasm a T or KT among individuals using different mating tactics within the same male morph; that is, among M+ males, nest-holders did not differ in androge n levels from floaters [nest-holder androgen levels (mean It SE): total T = 12.3 +/- 4.4 ng ml(-1), total KT = 4.3 +/- 1.4 ng ml(-1); neater androgen levels (mean +/- SE): total T = 5.9 +/- 0.8 ng ml(-1), total KT = 3.4 +/- 0 .3 ng ml(-1)], and among M- males, satellites did not differ in androgen le vels from sneakers [satellite androgen levels (mean +/- SE): total T = 7.7 +/- 1.5 ng ml(-1), total KT = 1.3 +/- 0.3 ng ml(-1); sneaker androgen level s (mean +/- SE): total T = 8.3 +/- 1.6 ng ml(-1), total KT = 1.4 +/- 0.3 ng ml(-1)]. Thus, the observed differences appear to be correlated with the e xpression of different male morphotypes and not with the expression of diff erent behavioral tactics within the morphotype. Androgen levels were not co rrelated with the behavior activity of nest-holders, except for a negative correlation between KT levels and parental behavior. Furthermore, nest hold er males that succeeded in having females spawn in their nests during the o bservation period had significantly lower KT levels than unsuccessful males . Since behavioral observations preceded blood sampling in time, it is sugg ested that these results indicate a negative relationship between KT and pa rental care, since successful males were parenting when blood samples were collected. Male SSC were better correlated with KT than with T and the use of total blood levels (i,e,, free + conjugates) yielded higher correlation coefficients than when only the free fraction of each steroid was considere d. Since conjugates are nonactive metabolites of the free androgen they sho uld reflect active free steroids in a previous time. Thus, their incorporat ion into the hormonal measurements increases the time frame captured, and b ecause steroids are released in a pulsatile way, this time-integrated measu re can be more meaningful than the free steroids, which represent a snapsho t of the hormone levels at a given point in time. (C) 2001 Academic Press.