Semilunar spawning cycle of the humbug damselfish Dascyllus aruanus

A very distinct semilunar spawning cycle was found in a population of the damselfish Dascyllus aruanus on the coral reefs of Sesoko Island, Okinawa. Spawning occurred from June to September, only in the early morning, during a period of 2–4 days immediately before or around the time of the new and full moon. Males cared for the eggs deposited on the substrate for 2.5 days until hatching. Hatching occurred just after sunset, i.e., at the high tide of spring tide; the strong ebb current then would rapidly disperse the newly hatched larvae offshore. Females tended to synchronize spawning in a male's nest, also because multiple clutches in a nest would be more likely to survive until hatching. Thus, the distinct semilunar spawning cycle may favor females in reducing mortality of both eggs and larvae. Received: July 9, 1999 / Accepted: January 29, 2000     

Population variation in spawning current speed selection in the blacktail shiner,Cyprinella venusta (Pisces: Cyprinidae)

Synopsis Many stream fishes lay demersal eggs. Some species simply scatter the eggs across the substrate, but many place the eggs in protected sites such as crevices (e.g., Cyprinidae:Cyprinella). Eggs laid in crevices may experience increased development times or lower embryo survival due to reduced water exchange rates compared to more open egg deposition sites. If so, the presence of an appreciable current near the crevice may be important for insuring water exchange. However, currents that are too strong may prevent complete insemination or prevent the eggs from adhering to the substratum before they are washed from the crevice. Thus, current speed preferences for spawning may be under strong stabilizing selection. Representatives of four populations of a crevice spawning stream fish (blacktail shiner,Cyprinella venusta), representing environments ranging from a swift stream to a lake, were studied in stream tanks to evaluate female spawning current use. The observed frequency of use of spawning currents was significantly different from random in all populations. Low current speeds were generally avoided, and a speed of ca. 30 cm sec^–1 was used most often. However, significant differences were observed among populations, and the variation correlated well with the apparent range of current speeds found in the four environments. Although other possible explanations cannot be dismissed, the results are consistent with the hypothesis that the populations have become adapted to their local current regimes.Authorship in order of seniority     

Mating success in brood-guarding male rock bass,Ambloplites rupestris: the effect of body size

Synopsis The hypothesis that variation in a paternal trait associated with offspring survival will result in female mate choice based on that trait was tested in rock bass,Ambloplites rupestris, a temperate fresh water fish with uniparental male care. The number of eggs acquired by 108 nesting male rock bass, in Cranberry Lake (New York State, U.S.A.), was estimated in two different spawning episodes that differed in the size structure of the nesting male stock. Early breeders (between the 4–7 June 1989) were mainly medium and large males (101–300 g), as compared to late breeders (between the 19–21 June 1989) which were mostly small (50–100 g). Because survival of larvae in rock bass is significantly lower in nests guarded by small males as compared to nests guarded by medium and large males, it was hypothesized that female mate choice should have been (1) size-based, and (2) more intense late in the season when the nesting stock was comprised mostly of small males. The results were consistent with these hypotheses. Variation in egg numbers per nest was significantly higher during the late spawning episode. In addition, egg number per nest were normally distributed during the early spawning episode, but were positively skewed and leptokurtic during the later episode. The correlation between male size and egg number was significant for both spawning episodes. However, during the late episode male size explained 23% of the variation in egg numbers versus only 8% of the variation during the earlier episode.     

Height and reproductive success in a cohort of british men

Two recent studies have shown a relationship between male height and number of offspring in contemporary developed-world populations. One of them argues as a result that directional selection for male tallness is both positive and unconstrained. This paper uses data from a large and socially representative national cohort of men who were born in Britain in March 1958. Taller men were less likely to be childless than shorter ones. They did not have a greater mean number of children. If anything, the pattern was the reverse, since men from higher socioeconomic groups tended to be taller and also to have smaller families. However, clear evidence was found that men who were taller than average were more likely to find a long-term partner, and also more likely to have several different long-term partners. This confirms the finding that tall men are considered more attractive and suggests that, in a noncontracepting environment, they would have more children. There is also evidence of stabilizing selection, since extremely tall men had an excess of health problems and an increased likelihood of childlessness. The conclusion is that male tallness has been selected for in recent human evolution but has been constrained by developmental factors and stabilizing selection on the extremely tall. The National Child Development Study is carried out by the researchers of the Centre for Longitudinal Studies, Institute of Education, London. The data are housed at the Data Archive of the University of Essex, from where they were obtained under license for the present study. I am grateful to Paul Preece for his assistance with data processing, and to Benjamin Campbell and two anonymous referees for invaluable advice which has, I hope, improved the quality of this paper. Daniel Nettle is lecturer in biological psychology at the Open University. With a first degree in psychology and a Ph.D. in biological anthropology, his work has been concerned with the application of evolutionary models to such topics as language (e.g., Linguistic Diversity, Oxford University Press, 1999) and individual differences (Strong Imagination, Oxford University Press, 2001).     

Deepwater broadcast spawning by Montastraea cavernosa, Montastraea franksi, and Diploria strigosa at the Flower Garden Banks, Gulf of Mexico

Broadcast spawning by corals is a tightly synchronized process characterized by co-ordinated gamete release within 30–60 min time windows once per year. In shallow water corals, annual water temperature cycles set the month, lunar periodicity the day, and sunset time the hour of spawning. This tight temporal regulation is critical for achieving high fertilization rates in a pelagic environment. Given the differences in light and temperature that occur with depth and the importance of these parameters in regulating spawn timing, it has been unclear whether deeper coral can respond to the same environmental cues that regulate spawning behaviour in shallower coral. In this report, a remotely operated vehicle was used to monitor coral spawning activity at the Flower Garden Banks at depths from 33 to 45 m. Three species Montastraea cavernosa, Montastraea franksi, and Diploria strigosa were documented spawning within this depth range. All recorded spawning events were within the same temporal windows as shallower conspecifics. These data indicate that deep corals at this location either sense the same environmental parameters, despite local attenuation, or communicate with shallower colonies that can sense such spawning cues.     

Partner preferences in the context of concurrency: What Himba want in formal and informal partners

Research on human mate preferences that distinguishes between short- and long-term partners has been conducted mainly in industrialized societies, where multiple mating and concurrent partnerships are stigmatized. However, cross-culturally, there is significant variation in the frequency and the level of acceptance of such relationships. Furthermore, the dichotomy between short- and long-term partnerships does not fully describe the diversity in actual extra-pair behavior, which ranges from single sexual encounters to multi-year love affairs. Here we present another comparison, between formal (marital) and informal (non-marital) partners, which we feel better captures this diversity. We assess the traits that men and women prefer in each type of partner among Himba pastoralists, where concurrent partnerships are common and accepted for both sexes. We situate our findings in relation to three main explanations for concurrent partnerships: dual-mating, trading-up and multiple investors. We find some similarities with the existing literature in the traits that are listed as important, including physical attractiveness, wealth and intelligence. Our evidence suggest that Himba men follow a dual strategy, preferring hard-working wives and attractive girlfriends. Women's preferences align most strongly with a multiple investors explanation, most clearly articulated through their preferences for wealthy husbands and generous boyfriends. Limited support is also found for a dual-mating strategy in women. These findings suggest that local cultural norms and ecologies modulate mate preferences in important ways.     

Two spawning seasons and mating system of the bastard halibut, Tarphops oligolepis

We investigated the breeding habits of the bastard halibut, Tarphops oligolepis, in the southwest of Kyushu Island, Japan. This fish was found to have two spawning seasons in a year (around July and November); individual fish spawned over the two spawning seasons. During the spawning seasons, males established territories. Home ranges of females overlapped with those of other females and with territories of plural males. The courtship partner changed during a day, and multiple matings among both sexes were observed during a spawning season, suggesting that T. oligolepis bred promiscuously. This is the first report of the mating system among Paralichthyidae. Received: October 18, 2000 / Revised: May 7, 2001 / Accepted: July 9, 2001     

Attractive males have faster sperm in three-spined sticklebacks Gasterosteus aculeatus

Recent studies have revealed that sexually selected traits may signal sperm quality and hence male fertilisation ability. There is also evidence that the expression of male sexual ornamentation and associated sperm characteristics depend on an indi- vidual＇s ability to cope with oxidative stress. Carotenoids are known for their antioxidant properties and carotenoid-based orna- ments might represent honest signals as these pigments can be traded offbetween the investment in sexual ornamentation, sperm function as well as immune response. In this study, we examined the relationship between sexual ornamentation （breeding colo- ration） and sperm characteristics （e.g., velocity and morphology） in the three-spined stickleback Gasterosteus aeuleatus, an ex- ternally fertilising fish species, in which sperm competition commonly occurs. During the breeding season males are sperm limi- ted and develop a conspicuous carotenoid-based coloration, which is under strong pre-copulatory sexual selection due to female mate choice and male-male competition. The results of the present study show that the expression of stickleback male breeding coloration is significantly positively associated with the linearity of sperm movement, whereas sperm morphology （head length to tail length ratio） is significantly negatively related to the trajectory of sperm movement. Moreover, there is some support for the phenotype-linked fertility hypothesis as the intensity of male red breeding coloration is significantly positively correlated with sperm velocity, which is supposed to be an important determinant of fertilisation success in external fertilisers, indicating the honesty of the sexually selected nuptial red coloration.     

Reproductive and Mating Success in the Small-Mouthed Salamander (Ambystoma texanum) Estimated via Microsatellite Parentage Analysis

Bateman’s principles of sexual selection predict that the sex with “cheaper” gametes may maximize reproductive efforts by mating multiply and so display greater positive covariance between reproductive and mating success. We conducted a semi-controlled breeding experiment to genetically quantify sexual selection in adult Ambystoma texanum, a sexually monomorphic salamander with simple courtship behaviors. We used four polymorphic microsatellite loci to genotype 57 adults enclosed in a breeding wetland and compared their multilocus profiles to that of 862 embryos collected from the enclosure. The molecular data were used to assign parentage, investigate the mating system, and measure sexual selection intensity. Parentage analyses indicated 36% of dams and 93% of sires were genetically sampled via their gametes but physically unsampled, suggesting that a large number of breeders over-wintered within the enclosure and/or some females released into the enclosure were already inseminated. We used the genetic data to generate estimates of individual reproductive and mating success and we interpret these in light of salamander behavior and sexual selection theory. The incidence of multiple mating in females (86%) was considerably higher than in males (32%) and the standardized variance in mating success was significantly greater in females. The correlations between reproductive and mating success were significant and of similar magnitude between the sexes, indicating that both sexes increased reproductive success through increased mating success. This pattern may be a function of differential opportunities for mating success between the sexes. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Mate selection,consortship formation,and reproductive tactics in adult female savanna baboons

Mate selection is a proximate mechanism influencing the probability that two individuals will engage in reproductive activity. The degree to which mate selection by female savanna baboons (Papio cynocephalus anubis) affects consortship formation and the characteristics of males that they prefer to mate with were analyzed based upon a 19-month study in Kenya. Sexual solicitations by females had a positive impact on the probability that males would establish consort relationships. The most preferred mating partners were young, high ranking, newcomer males, but these same males did not have the highest mating success. Friendships between male and female baboons almost always developed subsequent to conception cycles. Female savanna baboon reproductive tactics appear to be based upon maximizing the probability that males will provide care for offspring.     

Fitness and behavioral correlates of pre-stress and stress-induced plasma cortisol titers in pink salmon (Oncorhynchus gorbuscha) upon arrival at spawning grounds

Semelparous Pacific salmon (Onchorynchus spp.) serve as an excellent model for examining the relationships between life history, behavior and individual variation in glucocorticoid (GC) stress hormone levels because reproductive behaviors are highly variable between individuals and failure to reproduce results in zero fitness. Pink salmon (O. gorbuscha) were intercepted upon arrival at the spawning grounds across three time periods. Pre-stress and stress-induced plasma cortisol concentrations were assessed in relation to behavior, longevity and reproductive success. Results revealed differences between sexes and with arrival time. The study period marked a year of high reproductive success and only nine females (12% of sample) failed to spawn. Female pre-spawn mortalities were characterized by significantly elevated stress-induced cortisol concentrations and decreased longevity as well as pre-stress cortisol above the normal range in pink salmon from the study area. Interestingly, reproductive behaviors were only associated with pre-stress cortisol levels. For females, aggression and mate interaction time were reduced in individuals with elevated pre-stress cortisol concentrations. In males, a similar negative relationship between pre-stress cortisol concentration and mate interaction time was detected. The observed behavioral correlations are likely a factor of social status where dominant individuals, known to have higher reproductive success, are characterized by lower cortisol levels relative to subordinate conspecifics. Findings show both elevated pre-stress and stress-induced cortisol concentrations at arrival to the spawning grounds to be associated with reduced survival.     

Ocean current variability and the spawning season of Hawaiian reef fishes

Synopsis The spawning patterns of four Hawaiian reef fishes with similar reproductive habits, but different biogeographic distributions were studied from September 1980 to October 1981. Two species are Hawaiian endemics [Centropyge potteri (Pomacanthidae) and Chaetodon multicinctus (Chaetodontidae)] and the other two have pan-tropical Pacific distributions [Ctenochaetus strigosus and Zebrasoma flavescens (Acanthuridae)]. All showed increased spawning activity from January to July, the prevalent pattern among a majority of coastal marine fishes in Hawaii. Environmental correlatives to the period of peak reproduction include cycles of (a) daylight length and temperature which probably function as proximate cues and (b) seasonal variations in ocean current patterns which may ultimately affect survival of larvae and dispersal. Peak reproduction takes place during months when (1) mesoscale eddies most likely occur, and (2) the probability is greatest of drifting objects remaining near the islands.     

Gonad maturation and spawning times of Siganus sutor off the Keny a coast: evidence for definite spawning seasons in atropical fish

The gonad maturation cycle of Siganus sutor (Valenciennes, 1835) (Osteichthyes-Siganidae) is described for both males and females using macroscopic criteria for the testes and both macroscopic and microscopic ones for staging the ovaries. Siganus suror has two major spawning seasons: one in January/February and the other in May/June. The presence of these seasons is established by (a) the temporal variations in the condition factor and in the relative weight of the gonads, (b) the progression of peaks of maturity stages with seasonal occurrence of spent fish in the samples, and (c) the seasonal appearance ofjuveniles. This is a significant result for a tropical marine fish.     

Nonbreeding season pairing behavior and the annual cycle of testosterone in male and female downy woodpeckers, Picoides pubescens

Studies in birds show that testosterone (T) concentrations vary over the annual cycle depending on mating system and life history traits. Socially monogamous species show pairing behavior throughout the year and low levels of male-male aggression and are underrepresented in these studies, yet the function of testosterone could be particularly important for sexual and social interactions occurring outside the breeding season. We measured fecal T concentrations over the annual cycle and the frequency of interactions between male and female downy woodpeckers (Picoides pubescens) from late fall through early spring. We validated the fecal assay by collecting blood in conjunction with a subsample of our fecal samples: fecal T correlated with circulating levels in the blood. The annual peak level of T in males was relatively low and short-lived, similar to that of other bird species with low levels of male-male aggression and high paternal care. The annual cycle of female T resembled the male pattern, and the ratio of male T to female T was close to 1.0. Likewise, the frequency of aggression among females was similar to the frequency among males. Overall, testosterone levels in both sexes were variable, even in winter. In other bird species, sexual behavior during nonbreeding periods correlates with circulating levels of T in males. Based on this observation, we tested the hypothesis that T in winter was positively related to the frequency of interaction between mated downy woodpeckers. The results showed no such relationship. We discuss this finding and further relate the annual cycle of T in both males and females to behaviors that appear to facilitate mate choice and retention of the pair bond during conspecific challenge.     

Variance in reproductive success and the opportunity for selection in a serially monogamous species: simulations of the mating system of <Emphasis Type="Italic">Tropheus</Emphasis> (Teleostei: Cichlidae)

Sexual selection is believed to play a major role in speciation processes of cichlid fishes in the East African Great Lakes, in particular Lakes Malawi and Victoria, by driving diversification in male nuptial coloration. In Lake Tanganyika, a high rate of color pattern diversification is found in the genus Tropheus, where more than 100, mostly allopatric, color morphs have been described. Whether color pattern differentiation in Tropheus could follow from sexual selection as well, has not yet been conclusively shown. Unlike typical sexually selected species, Tropheus are sexually monomorphic, establish temporary pair bonds and spawn monogamously. Variance in mating success among individuals would still allow for sexual selection, but due to their high population census sizes, parentage data from natural populations are difficult to obtain. Simulations designed according to existing data on mating behavior in Tropheus suggested that variance in male reproductive success can be substantial and lead to levels of opportunity for selection, which are similar to values estimated, for example, from natural populations of sexually dimorphic songbirds. Variance in male success was mostly affected by the way females perceived and reacted to differences between males, and to a lesser extent by the duration of components of the reproductive cycles of males and females. These results indicate that future work on the importance of sexual selection in Tropheus should concentrate on mate choice cues and female mate choice behavior, but does not depend critically on the acquisition of more detailed life history data.     

Male mate choice in Tibetan macaques Macaca thibetana at Mt. Huangshan, China

Though females are generally more selective in mate choice, males may also benefit from mate choice if male reproductive success is limited by factors other than simply the number of female mates, and if females differ in short-term reproductive potential. We studied male mate choice in a free-ranging troop of Tibetan macaques Macaca thibetana at Mt. Huangshan,China, from August 2007 to April 2008. We employed focal animal sampling and all occurrence sampling to record sexual related behaviors. Eight adult females were divided into three female quality categories according to the females' age, rank and parity.Using male mating effort as a proxy for male mate choice, we found that males do distinguish female quality and show time-variant mating strategies. Specifically, females with dominant rank, high fecundity, and middle age attracted significantly more males. Our results suggest that female short-term reproductive potential appears to be an important variable in determining male mating effort. Male Tibetan macaques do exercise mate choice for higher quality females as well as reduce useless reproductive cost, which is consistent with the direct benefits theory of mate choice.     

Mating system of the lefteye flounder,Engyprosopon grandisquama

Underwater observations were conducted on the reproductive behavior and mating system of the lefteye flounder,Engyprosopon grandisquama, off Nagashima, southwest of Kyushu Island, Japan. Two types of males were found: large males, which defended territories against other large males, and small males, which did likewise but only against smaller males. Large males established territories which encompassed or ovelapped the home ranges of 1 or 2 cohabitant females. Territories of the small males, in which a smaller female often maintained a home range, overlapped those of large males. Pair spawning occurred around sunset. Mating of large males with cohabitant females was observed 36 times and that of a small male with a smaller female once. Pair formation was assorted by body size, paired males being larger than females in most cases. Thus, inE. grandisquama, gigamous large males were common, small males occurring within the former's erritorial boundaries mating with smaller females.     

Selection of sites for egg deposition and spawning dynamics in the waccamaw darter

Synopsis We provided 93 experimental spawning covers for the waccamaw darter. We grouped the covers (3 sizes of slate and one of concave tile) in three arrangements at six Lake Waccamaw locations to separate the variables of water depth, distance from shore, cover density and cover type. Tag returns of marked males suggest low fidelity for nest sites. Egg production under the 3 different sizes of slate was not significantly different. Egg production under the tile was significantly less than that under the slates. Egg production was significantly higher off the undeveloped southeastern shore in 2 m of water and lowest at the shallowest location with the highest experimental cover density. The number of eggs in nest is positively correlated with male size. We conclude that medium size slate covers placed in a linear arrangement in 2 m of water on a mixed sand bottom result in the highest egg production for the waccamaw darter.