The relative effect of parasites and social status on sperm traits in Arctic charr

Abstract

Sperm production and sperm swimming speed, which most likely affect fertilization under sperm competition, are modified by proximate mechanisms. In a comprehensive observational study of free-living and reproductively active Arctic charr (Salvelinus alpinus) we examined the possible modulating effects of male social status (including ornamental development), parasite intensities and immunity on novel traits indicative of ejaculate quality (e.g., ATP in sperm cells, levels of immunoglobulines attached to sperm cells, and the degree of DNAfragmentation in sperm cells). A multiple regression model showed no relationship between DNA-fragmentation in sperm cells and abdominal coloration of charr, suggesting that sperm of colourful males are not better protected against oxidative stress. We found, however, that males with traits indicative of high social status had low amounts of ATP in sperm cells and also sperm cells with low swimming speed. Sperm production, on the other hand, was strongly predicted by parasite intensities only, and these associations were mainly positive.Our results suggest that the presence of parasites seems to stimulate sperm production similar to what is observed among males entering subordinate reproductive roles. Thus, if resistance towards parasites is influencing parasite intensities, resistance may also indirectly be important for the "choice" of reproductive role and in turn investment in primary sex traits.

On the relative effect of spawning asynchrony, sperm quantity, and sperm quality on paternity under sperm competition in an external fertilizer

“…One might speculate that the metabolic resources for sperm production and sperm velocity, are traded-off differently in dominant and subordinate males over the entire spawning season (Jeulin and Soufir, 1992;Burness et al, 2004, but see Burness et al, 2005) and that dominants in need of more energy for guarding activities, potentially resulting in positional advantages under synchronized spawning, might have to reduce energy investments in sperm. This explanation, which relies heavily on energy being a limited resource for reproductively active males, fits the observations that ATP-levels in sperm of charr is positively related to sperm velocity and negatively related to measures of high social status (i.e., dominance) (Figenschou et al, 2013). An explanation based on energy limitations also correspond with the recent suggestion that the adipose fin may have evolved as a signal of energy stores in salmonids (Haugland et al, 2011).…”

Intrapopulational variation of ejaculate traits and sperm depletion in red‐sided garter snakes

“…; Gibson & Rabalais, ). It is possible that these parasites directly damage the gonads, reduce energy availability for gamete production, and/or elicit an immune response that in turn alters gamete production, all consequences of parasitism observed in other host species (Lafferty & Kuris, ; Figenschou et al ., ). This question is being investigated currently.…”

Status Specific Tailoring of Sperm Behavior in an External Fertilizer

“…Moreover, males show high plasticity in reproductive behaviors, and social status seems to be conditional depending on other interacting males (Fabricius and Gustafson, 1954;Sigurjonsdottir and Gunnarsson, 1989;Cutts et al, 2001). Observational studies of reproductively active male charr show, in accordance with that predicted from theoretical models (Parker, 1990;Parker et al, 2013), that social status is negatively related to sperm velocity (Figenschou et al, 2013). Additionally, males experiencing a change in mating roles have repeatedly been found to rapidly adjust sperm production.…”

“…ATP stored in spermatozoa prior to ejaculation provides the necessary chemical energy to sustain sperm motility (Jeulin and Soufir, 1992), and in Bluegills, sperm from subordinates have about 1.5 times more ATP than sperm from dominants (Burness et al, 2004). Further, sperm ATP is positively associated with sperm velocity (Burness et al, 2004;Figenschou et al, 2013) and could be the proximate explanation for the differences in sperm velocity observed previously between males in the two mating roles when activated in water (see Haugland et al, 2008). Moreover, as sperm velocity in water has been found to predict fertilization under sperm competition (Gage et al, 2004;Liljedal, 2005;SchulteHostedde and Burness, 2005, see also Egeland et al, 2015), this investment could compensate for mating in a disfavored mating role when ejaculating out of synchrony and further away from the egg releasing female and the dominant male (Sørum et al, 2011;Egeland et al, 2015).…”

“…However, our present documentation of a status dependent modulation of sperm activity, increasing the sperm speed of dominant males while reducing the speed of sperm from subordinates compared to that seen in water, suggest that ovarian fluid could act as a medium for cryptic female choice. That is, as dominant males have less ATP in their sperm cells than subordinates (Figenschou et al, 2013), ovarian fluid seems selectively promoting swimming of sperm from dominant males. Yet, if it were a general tendency for ovarian fluid to "prefer" sperm from dominant males, one would probably not predict a more rapid decline in sperm velocity for sperm from dominant males.…”