Male Investments in High Quality Sperm Improve Fertilization Success,but May Have Negative Impact on Offspring Fitness in Whitefish

Many ejaculate traits show remarkable variation in relation to male social status. Males in disfavoured (subordinate) mating positions often invest heavily on sperm motility but may have less available resources on traits (e.g., secondary sexual ornaments) that improve the probability of gaining matings. Although higher investments in sperm motility can increase the relative fertilization success of subordinate males, it is unclear whether status-dependent differences in sperm traits could have any consequences for offspring fitness. We tested this possibility in whitefish (Coregonus lavaretus L.) by experimentally fertilizing the eggs of 24 females with the sperm of either highly-ornamented (large breeding tubercles, dominant) or less-ornamented (small tubercles, subordinate) males (split-clutch breeding design). In comparison to highly-ornamented individuals, less-ornamented males had higher sperm motility, which fertilized the eggs more efficiently, but produced embryos with impaired hatching success. Also offspring size and body condition were lower among less-ornamented males. Furthermore, sperm motility was positively associated with the fertilization success and offspring size, but only in highly-ornamented males. Together our results indicate that male investments on highly motile (fertile) sperm is not necessarily advantageous during later offspring ontogeny and that male status-dependent differences in sperm phenotype may have important effects on offspring fitness in different life-history stages.     

Ultra-acute exposure to cadmium does not impair whitefish sperm motility

Cadmium (Cd) exposure can impair the traits of aquatic animals associated with reproduction. In natural lakes Cd is typically detected at concentrations below 0.001 mg l⁻¹. The authors investigated the impact of ultra-acute Cd exposure on sperm motility in European whitefish (Coregonus lavaretus). They activated sperm with water containing various nominal concentrations of Cd and recorded sperm motility parameters. Only the highest Cd concentration (500 mg l⁻¹) was associated with decreased sperm swimming velocity and increases in both the percentage of static cells and curvature of the sperm swimming trajectory. The results indicate that environmentally realistic concentrations of Cd during the sperm motility activation are not critically harmful to male C. lavaretus fertilization potential.     

Metabolic rate, growth and aggressiveness in three Atlantic salmon Salmo salar populations

Standard metabolic rate ( R _S), specific growth rate ( G ) and aggressiveness were investigated in three Finnish populations of Atlantic salmon Salmo salar (Neva, Saimaa and Teno), which were reared in identical hatchery conditions. The populations differed in their geographical origin and native habitat. There was a significant difference between populations in R _S: the southernmost Neva population had higher values in R _S than the northernmost Teno population. No difference was found in G or aggressiveness between the populations. G was found to have a significant positive association with aggressiveness and R _S among the three populations, however, these results were not statistically significant after correction for multiple tests. There was no significant association between R _S and aggressiveness. Higher metabolic rate of the most southern population Neva is suggested to be an adaptation to the more abundant food sources of the southern stream.     

RESEARCH PAPER: Multiple Sexual Ornamentation Signals Male Quality and Predicts Female Preference in Minnows

Sexual ornamentation often consists of multiple components. Different sexual signals may indicate different aspects of mate quality or reflect quality in different time scales. On the other hand, same signals can have a dual function and are used both in male–male competition and courtship. Many fish species are capable of rapidly altering their colouration (ephemeral colour changes), but this capability is usually ignored in sexual selection studies. Here, we used experimentally manipulated social environments to study the ephemeral colour changes in multicomponent sexual signals of male minnows (Phoxinus phoxinus) during male–male competition and female choice. We found that the dominant males courted the females more actively and had redder and/or darker skin colouration than the subordinate males. Furthermore, darkness difference between subordinate and dominant males increased in the presence of female, which suggests that the male–male competition may increase the honesty of signalling and thus facilitate female choice. In support of this hypothesis, females had a strong behavioural preference towards the more colourful males, which may indicate female choice. As colourful males often had a higher social status than paler individuals, it is possible that females base their preference on male status, not only the colouration per se. In any case, our results suggest that sexual ornamentation of male minnows may signal status, courting activity and superior quality of the males and that these signals may have a dual function in both male–male competition and female choice. Females preferred different ornamental traits (dark and red colour patterns) relatively equally, indicating that mate choice is based on multiple cues.     

Latitudinal variation in sexual dimorphism in life‐history traits of a freshwater fish

Sexual dimorphism is common across the animal kingdom, but the contribution of environmental factors shaping differences between the sexes remains controversial. In ectotherms, life‐history traits are known to correlate with latitude, but sex‐specific responses are not well understood. We analyzed life‐history trait variation between the sexes of European perch (Perca fluviatilis L.), a common freshwater fish displaying larger female size, by employing a wide latitudinal gradient. We expected to find sex‐dependent latitudinal variation in life‐history variables: length at age, length increment, and size at maturity, with females showing consistently higher values than males at all latitudes. We further anticipated that this gender difference would progressively decrease with the increasingly harsh environmental conditions toward higher latitude. We hypothesized that growth and length increment would decrease and size/age at maturity would increase at higher latitudes. Our results confirmed female‐biased sexual size dimorphism at all latitudes and the magnitude of sexual dimorphism diminished with increase in latitude. Growth of both sexes decreased with increase in latitude, and the female latitudinal clines were steeper than those of males. Hence, we challenge two predominant ecological rules (Rensch's and Bergmann's rules) that describe common large‐scale patterns of body size variation. Our data demonstrate that these two rules are not universally applicable in ectotherms or female‐biased species. Our study highlights the importance of sex‐specific differences in life‐history traits along a latitudinal gradient, with evident implications for a wide range of studies from individual to ecosystems level.     

Validation of the rat limb bud micromass test in the international ECVAM validation study on three in vitro embryotoxicity tests

A detailed report is presented on the performance of the rat limb bud micromass (MM) test in a European Centre for the Evaluation of Alternative Methods (ECVAM)-sponsored formal validation study on three in vitro tests for embryotoxicity. Twenty coded test chemicals, classified as non-embryotoxic, weakly embryotoxic or strongly embryotoxic on the basis of their in vivo effects on animals and/or humans, were tested in four laboratories. The outcome showed that the MM test is an experimentally validated test, which holds promise for use for identifying strongly embryotoxic chemicals, but which needs to be improved before it can be recommended for use for regulatory purposes.     

Global warming potentials of stemwood used for energy and materials in Southern Finland: differentiation of impacts based on type of harvest and product lifetime

Wood harvesting in boreal forests typically consists of sequential harvesting operations within a rotation: a few thinnings and a final felling. The aim of this paper is to model differentiated relative global warming potential (GWP) coefficients for stemwood use from different thinnings and final fellings, and correction factors for long‐lived wood products, potentially applicable in life cycle assessment studies. All thinnings and final fellings influence the development of forest carbon stocks. The climate impact of a single harvesting operation is generated in comparison with no harvesting, thus encountering a methodological problem on how to handle the subsequent operations. The dynamic forest stand simulator MOTTI was applied in the modelling of evolution of forest carbon stocks at landscape level in Southern Finland. The landscape‐level approach for climate impact assessment gave results similar to some stand‐level approaches presented in previous literature that included the same forest C pools and also studied the impacts relative to the no‐harvest situation. The climate impacts of stemwood use decreased over time. For energy use, the impacts were higher or similar in the short term and 0–50% lower in the midterm in comparison with an identical amount of fossil CO₂. The impacts were to some extent (approximately 20–40%) lower for wood from intermediate thinnings than for wood from final fellings or first thinnings. However, the study reveals that product lifetime has higher relative influence on the climate impacts of wood‐based value chains than whether the stemwood originates from thinnings or final fellings. Although the evolution of future C stocks in unmanaged boreal forests is uncertain, a sensitivity analysis suggests that landscape‐level model results for climate impacts would not be sensitive to the assumptions made on the future evolution of C stocks in unmanaged forest. Energy use of boreal stemwood seems to be far from climate neutral.     

Structural equation models suggest that bottom‐up processes override top‐down processes in boreal pikeperch (Sander lucioperca) lakes

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