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Female comparative mate choice influences strategic male nesting strategy in the peacock blenny Salaria pavo
No full textEmerging evidence endorses the idea that comparative instead of rational choice is widespread among species and mating contexts. In a comparative scenario the attractiveness of a male is not absolute but depends on the attractiveness of the other males to whom he is compared by females. Therefore, a male may benefit from the ability to choose the appropriate context that enhances his attractiveness. Here we test for the occurrence of strategic male nesting strategies in the peacock blenny, Salaria pavo, a fish species in which females evaluate potential mates by comparing males. Our results show that the large majority of males choose the context that maximize their attractiveness by nesting close to less attractive neighbours. Overall, we suggest that, in the peacock blenny, comparative, non-directional female choice is associated to strategic male nesting strategies and this scenario may contribute to the maintenance of genetic variability of male sexually-selected traits
Going beyond conventional parameters to unveil sperm quality in fish: The use of fibre optic technology to assess mitochondrial respiratory performance
Full text linkSperm fertilisation success depends on both intrinsic quality and the interactions with the surrounding reproductive fluids. In several fish species, these interactions have a variable effect on sperm performance. Although specific responses to reproductive fluids may depend on intrinsic differences in sperm quality, variations in the traditionally recorded sperm functional traits do not fully account for the observed patterns. New methods to enhance the evaluation of sperm quality may prove to be valuable at both applied and theoretical levels, by improving the breeding protocol of reared species and the understanding of mating success in sperm competition contexts. Here we develop a fibre optic-based technique, also adequate for small ejaculate samples, to test the role of mitochondrial respiratory efficiency in deciphering sperm performance variability. We purposely used as model the grass goby, Zosterisessor ophiocephalus, a fish with guard-sneaker mating tactics where the sperm in each male tactic have similar intrinsic qualities (velocity, viability, ATP content), but sneakers' sperm exploit territorial males' seminal fuid, overall displaying better fertilization ability. We found that sperm differed in their mitochondrial respiratory efficiency, which was higher in sneakers' sperm compared to territorial ones. This result draws the attention to an indicator of sperm quality that might be helpful in disentangling the mechanisms driving sperm-reproductive fluid interactions
Female reproductive fluid concentrations affect sperm performance of alternative male phenotypes in an external fertilizer
Full text linkThere is growing evidence that the female reproductive fluid (FRF) plays an important role in cryptic female choice through its differential effect on the performance of sperm from different males. In a natural spawning event, the male(s) may release ejaculate closer or further away from the spawning female. If the relative spatial proximity of competing males reflects the female pre-mating preference towards those males, then favoured males will encounter higher concentrations of FRF than unpreferred males. Despite this being a common situation in many external fertilizers, whether different concentrations of FRF can differentially influence the sperm performance of distinct male phenotypes (favoured and unfavoured by the female) remains to be elucidated. Here, we tested this hypothesis using the grass goby (Zosterisessor ophiocephalus), a fish with distinct territorial-sneaker reproductive tactics and female pre-mating preference towards territorial males, that consequently mate in an advantaged position and whose sperm experience higher concentrations of FRF. Our findings revealed a differential concentration-dependent effect of FRF over sneaker and territorial sperm motility only at low concentrations (i.e. at the distance where sneakers typically ejaculate), with increasing FRF concentrations (i.e. close to the eggs) similarly boosting the sperm performance of both sneaker and territorial males. The ability to release sperm close to the eggs is a prerogative of territorials, but FRF can likewise advantage the sperm of those sneakers that are able to get closer, allowing flexibility in the direction of female post-mating choice
Sperm duct gland secretion of the grass goby Zosterisessor ophiocephalus exhibits antimicrobial activity
No full textThe grass goby Zosterisessor ophiocephalus sperm-duct gland extract displayed antimicrobial activity against gram-positive and gram-negative bacteria. This suggests that sperm-duct gland mucins might be functional in protecting eggs and possibly parents from pathogens, an activity of great adaptive value for Z. ophiocephalus, which lays eggs in mud nests
Black goby territorial males adjust their ejaculate's characteristics in response to the presence of sneakers
Full text linkIn many species, males can rapidly adjust their ejaculate performance in response to changing levels of sperm competition, an ability that is probably mediated by seminal fluid adaptive plasticity. In the black goby, Gobius niger, territorial males attach viscous ejaculate trails to the nest roof, from which sperm are slowly released into the water during the long-lasting spawning events. Sneaker males release their sperm in the vicinity of the nest, and territorial males try to keep them at a distance by patrolling their territory. We show here that territorial males' ejaculate trails released a higher proportion of their sperm in the presence of a single sneaker, but this proportion decreased when there were three sneakers, an effect that is most likely mediated by a change in the seminal fluid composition. Field observations showed that when multiple sneaking attempts occurred, territorial males spent more time outside the nest, suggesting that ejaculation rate and territory defence are traded-off. Altogether, these results suggest that the adjustment of sperm release from the ejaculate may be strategic, guaranteeing a more continuous concentration of the territorial male's sperm in the nest, although at a lower level, when he is engaged in prolonged territory defence outside the nest
When fathers make the difference: efficacy of male sexually selected antimicrobial glands in enhancing fish hatching success.
No full textEgg and offspring resistance to pathogens is a major determinant of survival and has been mainly ascribed to maternal factors. However, paternal production of antimicrobials was recently suggested to increase offspring survival in species where males perform egg care. 2. In the peacock blenny, Salaria pavo, a demersal spawning species where males exhibit a pair of anal glands producing lysozyme-like compounds, we tested the antimicrobial activity and the egg protection efficacy of these glands. The anal gland secretion (AGS) has an inhibitory effect on the growth of both Gram-negative and Gram-positive bacteria, including those causing the most severe fish diseases in marine culture. The egg clutches cared for by males deprived of anal glands have a significantly lower survival rate than those cared for by sham-operated males and non-viable eggs showed clear signs of bacterial infection. 3. Anal gland secretion production and its protein content are proportional to gland size. In species where male parental care plays a crucial role in offspring survival, females are expected to assess mates selecting those traits that are reliably associated with parental ability. Hence, we experimentally challenged females with dummy males differing in anal gland size. Females definitely preferred dummy males with larger anal glands, suggesting that their choice is driven by the pursuit of direct fecundity benefits. 4. These findings indicate that antimicrobial production is a crucial component of male parental care. The contribution of antimicrobials to male performance as fathers suggests that the development of traits devoted to this function may influence male attractiveness and be sexually selected
Mating system in a small pelagic spawner: field case study of the mandarinfish, Synchiropus splendidus
Full text linkMating systems in fishes are extremely diverse, ranging from monogamy to multiple polygamous forms, some of which include alternative male mating tactics within species. The major reproductive mode across approximately 33,000 bony fishes is pelagic-spawning with external fertilization. Despite the dominance of this mode, it is relatively little studied in the field because the greater mobility of larger species typically makes individuals difficult to follow for extensive periods, or to catch and mark. However, smaller, more sedentary pelagic spawners provide excellent opportunities to examine mating system variability in response to environmental conditions. The mandarinfish, Synchiropus splendidus, is a small sedentary pelagic spawner which is accessible to divers. Its complex body markings are distinctive and variable allowing individuals to be identified and followed repeatedly without the need for capturing and marking fish. In over 400 h of underwater surveys, we recorded movements, inter- and intra-sexual behaviors, sex ratios, and the timing and duration of spawning activity of focal fish in predetermined study areas. We concluded that the mandarinfish has a polygamous mating system with pair-spawning. Females are sequentially polyandrous, spawning once nightly or not at all, while males are polygynous, spawning up to 8 times a night. Males and females use loosely defined spawning sites on a daily basis and show flexibility in their tactics through differential movements according to dispersion of individuals, distances between spawning sites and temporally limited daily female receptivity. These results reveal the mandarinfish to be an excellent model species for studying small pelagic spawners in the field
A male sexually dimorphic trait provides antimicrobials to eggs in blenny fish
No full textPredation and microbial infections are the major
causes of natural mortality for early life stages of
oviparous species. The parental traits reducing
the effects of predation are rather well described,
whereas antimicrobial mechanisms enhancing
offspring survival are largely unexplored. In this
paper, we report that a male sexually dimorphic
trait, the anal glands, of the redlip blenny
(Ophioblennius atlanticus atlanticus) and the
peacock blenny (Salaria pavo), two fish species
with paternal egg care, produce a mucus enriched
with antimicrobial substances. Histological and
histochemical analyses showed that the anal
glands of these species are characterized by the
massive presence of mucus-secreting cells. Anal
gland extracts, from both the hydrophilic and
the hydrophobic protein fraction, exhibited a
lysozyme-like activity. Field observations demonstrated
that redlip blenny males, while performing
egg care, rub the anal region over the nest
internal surface, probably facilitating the transfer
of mucus to eggs. These results strongly indicate
that this sexually dimorphic trait is involved in
egg defence againstmicrobial infections
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