Early Maturing Males Research Articles

Smoltification, seawater performance, and maturation in Atlantic salmon (Salmo salar) fed different fat levels

IntroductionThe use of recirculating aquaculture systems (RAS) to produce Atlantic salmon smolts has resulted in exceptionally high fish growth rates. However, there are potential negative trade-offs between fast growth and key physiological processes, such as inadequate smoltification and early sexual maturation, which can both be linked to body energy reserves.MethodsThis study determined the effect of i) dietary fat levels on Atlantic salmon whole-body fat and fatty acids composition, growth performance and smoltification and ii) a previous dietary regime on seawater growth performance and male early sexual maturation. In freshwater RAS, salmon parr (~19g) were fed 3 fat levels (20, 24, and 28%) over a 14-week period at 12°C. Subsequently, in seawater flow-through systems, smolt (~96g) were fed a control diet (26%) for 12 weeks at 2 temperatures (12 and 16°C).ResultsDietary fat levels resulted in differences in k-factor, fish whole-body fat and fatty acids composition; the low fat diet resulted in fish with a 23% lower whole-body fat when compared to the other two dietary groups at the end of the freshwater phase. These differences in whole-body fat faded at the end of the seawater phase. During the freshwater phase, all three feeds resulted in a comparable growth performance and smoltification indicator values, including k-factor, gill Na+, K+-ATPase, blood serum chloride and smolt index score. In contrast, water temperature resulted in fish body weight differences, where groups reared at 16°C were larger than those reared at 12°C. Nevertheless, both temperature regimes supported a similar thermal growth coefficient. Smolts grown at 16°C showed a higher level of the sex steroids androstenedione compared to those at 12°C. However, 11-ketotestosterone and testosterone levels did not differ despite a trend for higher levels at 16°C. Furthermore, testis histology at the final sampling indicated that some individuals showed initial signs of maturation (stage 3).DiscussionIn conclusion, varying dietary fat levels (20 - 28%) during the freshwater phase did not influence smoltification or male early sexual maturation during the subsequent grow-out phase. However, a temperature increase from 12 to 16°C resulted in larger fish and appeared to stimulate early male maturation in some fish individuals.

Thyroid and Sex Steroid Hormones in Immature and Precocious Brown Trout <i>Salmo trutta</i>

The content of thyroid and sex steroid hormones in the blood of immature and precocious trout Salmo trutta at the final stage of the formation of early maturing fishes (age 1+, 2+) in the population was determined. The formation period of early maturing males varies in different years in Alatsoya River (Karelia). Fish can reach sexual maturity at the age of 1+ or 2+. Immature and precocious trout at the age of 1+ and 2+ do not differ in the free and total triiodothyronine and free thyroxine content. Immature females and males aged 1+ and 2+ also do not differ in the level of sex steroid hormones. In contrast to immature brown trout, precocious males aged 2+ are characterized by an increased content of testosterone and a reduced level of estradiol-17β in the blood. It has been established that the final stage of the formation of early maturing fishes in the population is characterized by a weak involvement of the thyroid gland in the maturation process of males. Also, it was shown that the rate of conversion of testosterone to estradiol-17β in their blood was a significant decrease (4 times). This transformation in all studied females and males of brown trout is associated with their body length. The rate of formation of estradiol-17β in fish was increased with increasing of body length.

Developmental fitness curves: assessing sprint acceleration relative to age and maturity status in elite junior tennis players

Background The influence of maturity-status on athletic performance is reasonably well-documented. Methodological and practical issues of assessment and lack of longitudinal data have impacted the success of various models. Aim To develop age- and sex-specific developmental curves for sprint acceleration in elite youth tennis players and to address variation in performance relative to chronological and biological age. Subjects and methods Measures of acceleration were available for 3120 elite youth tennis players aged 8–15 years attending National and Regional Talent Identification days. Variation in acceleration by chronological and estimated biological ages was evaluated in corresponding data for an independent sample of elite youth players 8.9 to 15.1 years of age. Results Acceleration varied as a function of chronological and biological age relative to developmental curves. Early maturing males and females had significantly poorer performances when acceleration was considered relative to biological age. Significant discrepancy in percentiles relative to biological versus chronological ages was also evident between early and late maturing players of each sex. Conclusion Evaluating performance relative to developmental curves and maturity status may be a practical means of monitoring long-term athlete development in tennis.

Evaluation of endocrine and transcriptomic markers of male maturation in winter-run Steelhead Trout (Oncorhynchus mykiss)

Steelhead Trout (Oncorhynchus mykiss) display a varied life-history, including precocious male maturation at age-1 or age-2. In wild fish, precocious male maturation represents an important component of a diverse life-history portfolio. In hatchery programs, however, it is undesirable if rearing practices increase rates of early male maturation and reduce numbers of anadromous male adults. Our study aimed to develop endocrine and molecular markers for identifying males at early stages of maturation in the spring (prior to smolt release) and evaluated the potential use of these markers for quantifying early male maturation rates at a hatchery scale. In a laboratory study, Skookumchuck winter-run Steelhead Trout were reared at a high growth rate in order to increase the occurrence of precocious male maturation. Fish were lethally sub-sampled in February, prior to the time of smolt release; in May, at the time of smolt release; and in September, when 1+ age maturing males that would spawn the following spring were clearly identifiable based solely on gonadosomatic index (GSI). In February and May samples, we measured GSI, plasma 11-ketotestosterone (11KT), mRNAs for pituitary follicle stimulating hormone (fshb) and luteinizing hormone (lhb) beta subunits, and analyzed stage of spermatogenesis by testis histology. Additionally, in May, we measured testis anti-Müllerian hormone (amh) and insulin-like growth factor 3 (igf3) mRNA. Our primary goal was to evaluate the aforementioned maturation indices for their efficacy in forecasting the proportion of fish initiating early male maturation in the spring (approximately 1 year prior to spermiation), compared to the proportion that actually matured. Combining measures of GSI, plasma 11KT, and pituitary fshb and lhb mRNA expression provided a useful, but conservative, estimate of the proportion of males initiating maturation in the spring (21%) compared to the proportion that were ultimately destined to mature (37%) the following spring. These results suggest that maturation may be less synchronous than previously appreciated and some males may have initiated maturation after our census in May.

Maintaining a wild phenotype in a conservation hatchery program for Chinook salmon: The effect of managed breeding on early male maturation.

In many salmonid species, age and size at maturation is plastic and influenced by the interaction between genetic and environmental factors. Hatchery reared salmon often mature at an earlier age and smaller size than wild fish. Modern salmon conservation efforts have focused on managing the level of gene flow between hatchery and natural origin fish to minimize potential genotypic and phenotypic change. In salmonids, maturation probability is dependent on exceeding a genetically set threshold in growth rate and energetic status (and by association, body size) referred to as the probabalisitic maturation reaction norm (PMRN). Over fourteen years, we monitored the frequency of age-2 precocious male maturation (common term: age-2 minijack rate) and the PMRN of natural founder (FNDR), integrated natural-hatchery (INT), and segregated hatchery (SEG) broodlines of spring Chinook salmon, Oncorhynchus tshawytscha. The average age-2 minijack rate (± SEM) of the FNDR, INT and SEG broodlines was 48.2 ± 5.2%, 41.9 ± 3.6% and 30.9 ± 4.7%, respectively. Additionally, the PMRN WP50 (predicted weight at 50% maturation) of the SEG broodline was significantly greater (20.5 g) than that of the FNDR/INT broodlines (18.2 g). We also conducted a common garden experiment exploring the effects of less than one [INT (0–1)], one [SEG (1)] or two [SEG (2)] generations of hatchery culture on the age-2 minijack rate and PMRN WP50. Growth was not significantly different among broodlines, but age-2 minijack rates were significantly lower following two consecutive generations of hatchery culture: [INT (0–1): 68.3 ± 1.7%], [SEG (1): 70.3 ± 1.8%] and [SEG (2): 58.6 ± 0.4%] and the PMRN WP50 was significantly higher by 6.1 g after two generations of SEG culture. These results indicate that managed gene flow reduces phenotypic divergence, but may serve to maintain potentially undesirably high age-2 minijack rates in salmon conservation hatchery programs.

Field evidence challenges the often-presumed relationship between early male maturation and female-biased sexual size dimorphism.

Female‐biased sexual size dimorphism (SSD) is often considered an epiphenomenon of selection for the increased mating opportunities provided by early male maturation (i.e., protandry). Empirical evidence of the adaptive significance of protandry remains nonetheless fairly scarce. We use field data collected throughout the reproductive season of an SSD crab spider, Mecaphesa celer, to test two hypotheses: Protandry provides fitness benefits to males, leading to female‐biased SSD, or protandry is an indirect consequence of selection for small male size/large female size. Using field‐collected data, we modeled the probability of mating success for females and males according to their timing of maturation. We found that males matured earlier than females and the proportion of virgin females decreased abruptly early in the season, but unexpectedly increased afterward. Timing of female maturation was not related to clutch size, but large females tended to have more offspring than small females. Timing of female and male maturation was inversely related to size at adulthood, as early‐maturing individuals were larger than late‐maturing ones, suggesting that both sexes exhibit some plasticity in their developmental trajectories. Such plasticity indicates that protandry could co‐occur with any degree and direction of SSD. Our calculation of the probability of mating success along the season shows multiple male maturation time points with similar predicted mating success. This suggests that males follow multiple strategies with equal success, trading‐off access to virgin females with intensity of male–male competition. Our results challenge classic hypotheses linking protandry and female‐biased SSD, and emphasize the importance of directly testing the often‐assumed relationships between co‐occurring animal traits.

The Impact of Different Hatchery Rearing Environments on Smolt‐to‐Adult Survival of Spring Chinook Salmon

AbstractThe aim of this study was to assess the effect of differing hatchery rearing environments on smolting, early male maturation, and smolt‐to‐adult return rates (SARs) in Chinook Salmon Oncorhynchus tshawytscha. In this investigation, SARs were compared for spring Chinook Salmon from Hood River stock reared at three different hatcheries and then released into the Hood River, replicated over three separate years (2010–2012). Differences in SARs were found both between rearing groups and release years. Smolts reared at Pelton Ladder had consistently higher SARs than those reared at either Parkdale or Carson hatcheries. Smolt length at release was positively correlated to SARs across years and rearing groups. In addition, multiple regression models suggested that attributes related to smolt quality were positively related to SARs while the minijack rate was negatively related to SAR. Migration of smolts downstream after release was also assessed. Larger smolts were faster downstream migrants and migration rate was positively related to subsequent SAR. Differences in smolt quality and SAR between rearing groups is attributed to differing patterns of growth in the different hatchery environments. The best‐performing smolts came from rearing groups that experienced a strong seasonal change in growth rate: relatively high growth in the summer, reduced growth and depletion of energetic stores in the autumn and winter, and then increased growth again in the spring. This pattern of seasonal anabolic and catabolic changes has been termed the wild fish template, and generating this physiological pattern generally may be applicable to hatchery‐reared Chinook Salmon.Received August 3, 2016; accepted December 20, 2016 Published online March 30, 2017

Evidence that Marine Temperatures Influence Growth and Maturation of Western Alaskan Chinook Salmon

AbstractChinook Salmon Oncorhynchus tshawytscha from western Alaska have experienced recent declines in abundance, size, and age at maturity. Declines have led to hardships for the region's subsistence and commercial salmon harvesters, prompting calls to better understand factors affecting the life history of these populations. Western Alaskan Chinook Salmon are thought to spend their entire marine residency in the Bering Sea. The Bering Sea ecosystem demonstrates high interannual variability that is largely driven by the annual extent of sea ice. However, warming is expected to supersede interannual variability in the next several decades as a consequence of climate change. We investigated the influence of sea surface temperatures (SSTs) on the life history of western Alaskan Chinook Salmon by using information from two regional populations subject to long‐term monitoring. We found strong correlations between early marine growth and SSTs. Warmer SSTs appeared to lead to a younger age at maturity, largely through the vector of augmented growth. However, we also present evidence that warmer SSTs may additionally decrease the average age of male recruits through reduced growth thresholds for early male maturation. Our results suggest that the anticipated warming of the Bering Sea will lead to higher early marine growth and a younger average age of maturation for western Alaskan Chinook Salmon.

Marker assisted selection for spawning date and co-variation among economically important fitness traits in a commercial strain of rainbow trout (Oncorhynchus mykiss)

The effects of marker assisted selection for spawning date in males on embryonic developmental rate, growth related traits and precocious male maturation and phenotypic and genetic associations among traits were investigated in a commercial strain of rainbow trout (Oncorhynchus mykiss). The relationship between spawning date category of the sire (early or late) and developmental rate as measured by hatching time was inconsistent among families. However, two half-sib families produced by males with an allelic complement associated with late spawning date had higher rates of precocious male maturation and faster developmental rates than two families produced by males with earlier spawning date alleles. QTL analysis suggests that some of the co-variation between spawning date and developmental rate has a genetic basis as two QTL for developmental rate as measured by hatching time co-localized to the same markers known to be associated with spawning date in this strain. We observed no association between the spawning date category of the sire and progeny length at 61days post-fertilization (alevin stage), body weight at 381days (juveniles), body weight at 614days and specific growth rate, which suggests that selection for early or late spawning date alleles will have little effect on growth traits. Within families, faster developmental rates conferred a size advantage at 61days post-fertilization but not at 381 and 614days. Moreover, no correlation between developmental rate and the propensity of early male maturation was detected within families. Males that matured at 2years were significantly heavier at both 381 and 614days and had higher specific growth rates than immature males and females. Likewise, body weight at 614days and family were significant predictors for the propensity for early sexual maturation in males. This indicates that selection for greater body size will likely result in higher rates of unwanted precocious male maturation. Together, these results suggest that co-variation among economically important fitness traits may present potential trade-offs impacting selection goals. RelevanceAddresses feasibility of using molecular approaches in selective breeding programs.

Production of market-size North American strain Atlantic salmon Salmo salar in a land-based recirculation aquaculture system using freshwater

There is interest in culturing Atlantic salmon Salmo salar to market-size in land-based, closed containment systems that use recirculation aquaculture systems (RAS), as this technology often enables facilities to locate near major markets, obtain permits, exclude obligate pathogens, and/or reduce environmental impacts. Use of land-based RAS to intensively culture market-size Atlantic salmon is a relatively new frontier and little information is available. Three trials were conducted to evaluate the performance of two North American strains of Atlantic salmon raised from post-smolt to market-size (4–5kg) in a near-commercial scale (260m3), land-based RAS using only freshwater. St. John River (SJR) salmon were reared during the first trial, and Cascade salmon (CS1 and CS2) were evaluated during two subsequent trials. Salmon were received as fertilized “eyed” eggs and cultured on-site through the entire production cycle. The grow-out period began at 14–16 months post-hatch when salmon post-smolt weighed 0.34–0.75kg on average. CS1 and SJR salmon grew 386–393g/month to a mean size of 4.1–4.2kg and CS2 salmon grew 413g/month to a mean size of 4.9kg prior to first harvest. Thereafter, weekly salmon harvests commenced for the next 6–19 weeks. The grow-out period, excluding harvest, lasted 9–10 months for each trial. Average water temperature was maintained at 15–16°C. Consistently linear growth rates were achieved by each population suggesting that growth was relatively independent of fish cohort/genetic strain, fish size, and maximum biomass density, which was 35, 100, and 118kg/m3 for SJR, CS1, and CS2, respectively. Feed conversion ratios ranged from 1.07 to 1.10. Fish mortality (including culls) for SJR, CS1, and CS2 was 9.5, 6.6, and 7.5% of the original number of stocked fish, respectively. No obligate fish pathogens, kudoa, sea lice, or pervasive parasites were detected. Salmon were not vaccinated against specific pathogens; and no antibiotics, pesticides, or harsh chemotherapeutants were used. Hydrogen peroxide (50–100ppm) and salt (10 ppt) were occasionally used to treat fungus during pre-smolt production, and salt (2–3 ppt) was used to treat fungus or ameliorate stress after handling events. No salmon escaped the facility due to built-in fish exclusion barriers. Early male maturation was observed during each trial. Male salmon began to exhibit maturation traits (kype, darkened skin coloration) at a mean weight of 1.5–2kg and were removed from the grow-out system when they weighed 2–3kg. SJR, CS1, and CS2 populations exhibited 37.0, 38.5, and 17.0% maturity, respectively. Fillet yield and product quality of immature, market-size salmon were comparable to reported measurements for commercially available salmon reared in net pens. This research suggests that it is biologically and technologically feasible to culture Atlantic salmon from post-smolt to market-size in a land-based RAS of suitable commercial scale; however, early male maturation could represent a production barrier. As of 2016, all-female Atlantic salmon eggs are commercially available and could provide an expedient solution to the problem of early male maturation in RAS.

Stock Differences in Growth, Smolting, and Early Male Maturation in Hatchery Spring Chinook Salmon: a Common‐Garden Experiment

AbstractHatchery spring Chinook Salmon Oncorhynchus tshawytscha from Parkdale Hatchery on the Hood River, Oregon, and Carson National Fish Hatchery (CNFH) on the Wind River, Washington, were reared under a common‐garden experimental regime at CNFH over three consecutive brood years (2008–2010) to assess the effects of stock on smoltification and early male maturation. Rearing groups were monitored for size, percent solid (a surrogate for whole‐body lipid), gill Na+,K+‐ATPase activity, and rate of precocious maturation in males (i.e., age‐2 minijack rate). Despite rearing of the stocks under identical conditions, the out‐of‐basin Hood River stock was significantly smaller throughout the study and at release as smolts, had lower whole‐body lipid at release, and had lower gill Na+,K+‐ATPase activity at release than the Carson stock; furthermore, the Hood River stock exhibited much higher mean minijack rates than the Carson stock (45% versus 23% of males). Using logistic regression, we demonstrated that the threshold size for initiation of early male maturation was significantly lower for the Hood River stock than for the Carson stock, suggesting a genetic basis for this life history difference. The present study highlights the importance of understanding how specific genotypes may respond differently to the unique environmental conditions in a given hatchery environment. These differences may in turn influence physiological and life history pathways that affect smolt‐to‐adult return rates and the demography of returning adults.

The Spawning Success of Early Maturing Resident Hatchery Chinook Salmon in a Natural River System

AbstractHatchery propagation of spring Chinook Salmon Oncorhynchus tshawytscha has been shown to increase the proportion of males maturing as minijacks (age 2) or microjacks (age 1) relative to those proportions in wild populations. However, little is known about the success of early maturing males when they spawn in the wild. A captive broodstock program for spring Chinook Salmon in the White River (a tributary of the Wenatchee River, Washington) has a high rate of early male maturity. We used genetic parentage analysis to evaluate the spawning success of anadromous males in comparison with inferred early maturing resident, hatchery‐origin males that spawned naturally. Based on samples of juvenile offspring (n = 1,007–1,368 fish/year) and a nearly complete sample of the potential anadromous parents, we found that during 2006–2009, 26–45% of the progeny did not have a male parent in the anadromous sample. In contrast, 0–23% of the progeny did not have a female parent represented in the sample. Using grandparentage analysis, we eliminated wild resident fish as a likely source of the unsampled male parents; thus, we concluded that those male parents were most likely early maturing resident fish that had been released from the captive broodstock program. The inferred spawning success of the unsampled resident males was significantly lower than that of the anadromous males. The typical mating pattern was for an anadromous female to produce about two‐thirds of her offspring with one or two anadromous males and the remaining one‐third with as many as 12 or more apparently resident males. To our knowledge, this is the first study to present evidence of successful reproduction by early maturing resident, hatchery‐origin Chinook Salmon in the wild. The conservation implications of this finding are complex and will depend upon the genetic basis of early maturity and its causes in hatchery settings.

Reduced photoperiod (18 h light vs. 24 h light) during first-year rearing associated with increased early male maturation in Atlantic salmon Salmo salar cultured in a freshwater recirculation aquaculture system

Reduced photoperiod (18 h light vs. 24 h light) during first-year rearing associated with increased early male maturation in Atlantic salmon <i>Salmo salar</i> cultured in a freshwater recirculation aquaculture system

Spontaneous male death and monogyny in the dark fishing spider

Monogyny (male monogamy) is found in a diverse assemblage of taxa, and recent theoretical work reveals that a male-biased sex ratio can favour the evolution of this relatively rare mating system. We integrate this theoretical framework with field observations and laboratory experiments involving the sexually size dimorphic fishing spider, Dolomedes tenebrosus, to test the prediction that this species exhibits monogyny. Field surveys revealed a male-biased sex ratio, likely resulting from different life-history strategies (early male maturation). Results from mating trials supported our prediction of monogyny as we discovered that males mate with a single female. Unexpectedly, however, we observed that mating results in obligate male death and genital mutilation. Additional field observations of released individuals suggest that males are not limited by their ability to encounter additional females. Controlled laboratory assays demonstrated that males discriminate among virgin and non-virgin female silk cues, consistent with predictions of first-male sperm precedence. In summary, we report a novel case of male self-sacrifice in a species that exhibits female-biased sexual size dimorphism, male-biased sex ratio, genital mutilation and a suggestion of first-male sperm precedence; all of which are consistent with theoretical predictions of the evolution of monogyny.

Early Life History Variation in Hatchery‐ and Natural‐Origin Spring Chinook Salmon in the Yakima River, Washington

AbstractIn male Chinook Salmon Oncorhynchus tshawytscha, age of maturation is phenotypically plastic, occurring at age 1 (referred to as precocious parr or microjack), age 2 (minijack), age 3 (jack), age 4, or age 5. Microjacks and minijacks are thought to forego migration to the ocean as smolts, instead remaining in headwaters and employing a “sneaking” strategy to fertilize eggs. We compared the prevalence of minijacks (minijack rate) among hatchery‐ and natural‐origin spring Chinook Salmon from the Yakima River, Washington, over seven brood years (2001–2007). We quantified minijack rates and sex ratios in the hatchery population prior to release and during out‐migration at a trap located 230 km downstream. Within this time period, we also monitored minijack rates in a 3‐year (brood years 2002–2004) growth study designed to reduce minijack production at the hatchery. Minijacks made up an average of 41% of the male population in the hatchery, but annual minijack rates varied in response to the growth rate or fish size at release. Average minijack rate was approximately 20% among out‐migrating hatchery fish, about half the rate found prior to release. Among out‐migrants, minijack rates of hatchery fish were approximately 10 times those of natural‐origin fish, but sex ratios were significantly skewed toward females in both hatchery‐ and natural‐origin groups. Data from this study and related studies suggest that the predominant age of early male maturation in the Yakima River and similar rivers is age 2 (minijack) in hatchery fish and age 1 (microjack) in natural‐origin fish. Based on this and other studies, we now recognize three minijack life history types in spring Chinook Salmon: resident, fluvial, and anadromous, depending on the migration pattern exhibited in the spring and summer. Finally, we discuss the broader impacts that high minijack production may have on the establishment of size‐at‐release targets for salmon supplementation programs in the future.

Spermatogenesis in reciprocal hybrids of Atlantic salmon (Salmo salar L., 1758) and sea trout (Salmo trutta trutta L., 1758) during their freshwater period

Summary Development of gonads and the course of spermatogenesis were studied in 1–2 years old reciprocal hybrids of Atlantic salmon and Sea trout grown. These fish were produced under controlled conditions and raised in restricted natural water courses. Histological analysis (light microscopy) revealed that spermatogenesis in these two types of hybrids was without significant deviations from normal. Early maturing males produced sperm in their first and second years. The percent of maturing individuals and the sexual cycle was similar in the reciprocal hybrids and close to that of the parent species. In the first year of life early maturing males represented 12 and 13% of trout × salmon and salmon × trout hybrids, respectively, while in the second year this percentage raised to 83 and 100%, respectively. During the first year all maturing males of the reciprocal hybrids underwent incomplete maturation, producing a low number of mature germ cells. This feature is also typical in 1 year old fish of the parental species.

Peer substance use as a mediator between early pubertal timing and adolescent substance use: Longitudinal associations and moderating effect of maltreatment

BackgroundEarly pubertal timing has received considerable empirical support as a risk for adolescent substance use. However, few studies have examined the mediators linking these variables. Therefore, the aims of this study were (1) to examine peer substance use as a mediator between pubertal timing and adolescent substance use longitudinally and (2) to test gender and maltreatment experience as moderators of the mediational model. MethodsData were obtained from Time 1, 2, and 3 of a longitudinal study of maltreatment and development. At Time 1 the sample was comprised of 303 maltreated and 151 comparison children aged 9–13 years (213 females and 241 males). Longitudinal mediation was tested using structural equation modeling and moderating effects were tested using multiple group analysis. ResultsPeer substance use mediated the relationship between early pubertal timing and later adolescent substance use for the total sample. Moderation analyses indicated this significant indirect effect did not differ for males and females. However, it did differ for maltreated versus comparison adolescents with the mediational effect only remaining significant for the comparison group. ConclusionsThis is one of the first studies to examine peer substance use as a mediator of pubertal timing and adolescent substance use using a longitudinal design. Early maturing males are at equal risk to early maturing females for interacting with peers that may draw them into substance use. Additionally, the findings indicate that while peers are mediators for comparison adolescents a different mechanism may link early puberty to substance use for maltreated adolescents.

Weighing costs and benefits of mating in bushcrickets (Insecta: Orthoptera: Tettigoniidae), with an emphasis on nuptial gifts, protandry and mate density

Sexual selection is a major force driving evolution and is intertwined with ecological factors. Differential allocation of limited resources has a central role in the cost of reproduction. In this paper, I review the costs and benefits of mating in tettigoniids, focussing on nuptial gifts, their trade-off with male calling songs, protandry and how mate density influences mate choice. Tettigoniids have been widely used as model systems for studies of mating costs and benefits; they can provide useful general insights. The production and exchange of large nuptial gifts by males for mating is an important reproductive strategy in tettigoniids. As predicted by sexual selection theory spermatophylax size is condition dependent and is constrained by the need to invest in calling to attract mates also. Under some circumstances, females benefit directly from the nuptial gifts by an increase in reproductive output. However, compounds in the nuptial gift can also benefit the male by prolonging the period before the female remates. There is also a trade-off between adult male maturation and mating success. Where males mature before females (protandry) the level of protandry varies in the direction predicted by sperm competition theory; namely, early male maturation is correlated with a high level of first inseminations being reproductively successful. Lastly, mate density in bushcrickets is an important environmental factor influencing the behavioural decisions of individuals. Where mates are abundant, individuals are more choosey of mates; when they are scarce, individuals are less choosey. This review reinforces the view that tettigoniids provide excellent models to test and understand the economics of matings in both sexes.

Breeding success of four male life history types of spring Chinook Salmon spawning in an artificial stream

In 1997 the Cle Elum Supplementation Research Facility was established to enhance spring Chinook salmon returning to the upper Yakima River, Washington State. This effort increased spring Chinook abundance, yet conditions at the hatchery also significantly elevated the occurrence of jacks and yearling precocious males. The potential genetic effect that a large influx of early maturing males might have on the upper Yakima River spring Chinook population was examined in an artificial stream. Seven independent groups of fish were placed into the stream from 2001 through 2005. Males with four different life history strategies, large anadromous, jacks, yearling precocious, and sub-yearling precocious were used. Their breeding success or ability to produce offspring was estimated by performing DNA-based pedigree assessments. Large anadromous males spawned with the most females and produced the greatest number of offspring per mate. Jacks and yearling precocious males spawned with more females than sub-yearling precocious males. However, jacks, yearling and sub-yearling precocious males obtained similar numbers of fry per mate. In the test groups, large anadromous males produced 89%, jacks 3%, yearling precocious 7%, and sub-yearling precocious 1% of the fry. These percentages remained stable even though the proportion of large anadromous males in the test groups ranged from 48% to 88% and tertiary sex ratios varied from 1.4 to 2.4 males per female. Our data suggest that large anadromous males generate most of the fry in natural settings when half or more of the males present on a spawning ground use this life history strategy.

Exposure to peer delinquency as a mediator between self-report pubertal timing and delinquency: A longitudinal study of mediation

This study examined exposure to peer delinquency as a mediator between pubertal timing and self-reported delinquency longitudinally and whether this mediational model was moderated by either gender or maltreatment experience. Data were obtained from Time 1, 2, and 3 of a longitudinal study of maltreatment and development. At Time 1 the sample comprised 454 children aged 9-13 years. Analyses via structural equation modeling supported full mediation. Gender did not moderate this mediational relationship, but maltreatment experience did. The results show that early maturing males and females are both at risk for being exposed to peers that may draw them into delinquent behavior. In addition, the mechanism linking early pubertal timing to delinquency differs depending on maltreatment experience.