Satellite Males Research Articles

Adoption of satellite behavior by small male green treefrogs, Dryophytes cinereus, is not associated with age: Implications for the maintenance of alternative behavioral phenotypes

AbstractBody size is often a critical determinant of competitive ability and reproductive behavior. For example, small males characteristically lose contests with larger males and may be metabolically constrained from sustaining energetically demanding reproductive behaviors. Small males thus often utilize alternative reproductive tactics (ARTs) to maximize their reproductive success. How variation in body size among behavioral phenotypes arises can provide important insight into the maintenance of ARTs. For instance, smaller body sizes for males adopting ARTs may simply be a function of age, suggesting that the tactic is maintained by the periodic recruitment of young males into the population. Alternatively, body size differences among behavioral phenotypes that are unrelated to age suggest disparate growth rates that potentially arise as a consequence of variation in environmental conditions during development or genotypic differences between the phenotypes. Here we examine these alternative scenarios in the green treefrog, Dryophytes cinereus, using skeletochronological analysis combined with body size measures. As with many other anuran amphibians, male green treefrogs conditionally adopt a noncalling satellite mating tactic and attempt to intercept females attracted to the vocalizations of calling “host” males. We show that males adopting satellite behavior in natural choruses are smaller than calling males but do not represent a class of younger individuals, indicating that satellite males have lower growth rates than calling males. We also show that satellite males are in poorer condition than larger calling males, implicating energetic constraints in size‐related variation in mating tactic expression. Our work suggests that environmental conditions during development, genetic differences between phenotypes, or both, give rise to size discrepancies in behavioral phenotypes, neither of which have been previously explored in anurans. We discuss body size and condition differences between behavioral phenotypes in the context of energetic constraints and endocrine mediation of tactic expression in this species.

Effects of Varying Dietary Levels of Hibiscus rosa sinensis Leaves Powder on Growth and Gonads Development in Nile Tilapia Oreochromis Niloticus (Linnaeus, 1758)

Aims: The purpose of this study was to explore the possible use of Hibiscus rosa sinensis leaf powder as a reproductive inhibitor in Oreochromis niloticus
 Place and Duration of Study: From 10th February to 21st June 2021 at the Kanhé-Moyo Integrated Fisheries and Aquaculture Research and Application Farm located in the locality of Baho'o belonging to the Baham District,in the West Region of Cameroon
 Study Design: 720 Oreochromis niloticus fingerlings with an average weight of 13±2.5g were randomly distributed in 12 happas arranged in an earthen pond measuring approximately 10 x 20 m and fed 3 experimental diets, formulated from a control diet to contain Hibiscus rosa sinensis leaf powder at doses of 3.5, 4.5 and 5.5 g/kg of feed respectively.
 Methodology: After 45 days post-treatment, survival and zootechnical growth parameters were assessed. Histological examination of the gonads was used to determine the impact of treatment on gonadal development at 45 and 65 days post-treatment respectively.
 Results: The results show that the different treatments had a similar effect on survival (P˃0.05), with an average value of 97.91 ± 3.81%. Analysis of the growth parameters of fishes from the different batches treated with different doses of H. rosa sinensis leaf powder revealed that the dose of 4.5 g/kg of H. rosa sinensis had a significantly greater effect than the other treatments applied in terms of Mean Final Weight (with a mean value of 24.77±0.27g), Mean Weight Gain (with a mean value of 3.63±1.18 g), mean specific growth rate (with a mean value of 1.13 ± 0.40%/day) and Mean Daily Gain (with a mean value of 0.25±0.08 g/d). However, analysis of the gonado somatic index at 45 and 60 days post-treatment of batches treated with different doses of H. rosa sinensis leaves revealed a significantly higher effect of the 3.5 g/kg dose on the gonado somatic index in both males and females. Observation of the testicular structures of the males from the treated batches revealed alterations reflecting an inhibition of gonadal development, which justifies the low gonado somatic index values observed in these different treated batches compared with the control batches. These alterations were also observed in the ovarian tissues of the treated females both at 45 and 60 days post-treatment. However, observations of the gonadal structures of satellite males and females at 60 days post-treatment revealed partial restoration of gonadal tissue in both males and females.
 Conclusion: The results of this study indicate that Hibiscus rosa sinensis leaves could be used as an alternative ecological method for inhibiting reproduction in Oreochromis niloticus. The results will help local producer networks to improve tilapia production.

Excitatory and inhibitory interactions affect the balance of chorus activity and energy efficiency in the aggregations of male frogs: Numerical simulations using a hybrid dynamical model

We numerically study the role of excitatory and inhibitory interactions in the aggregations of male frogs. In most frogs, males produce sounds to attract conspecific females, which activates the calling behavior of other males and results in collective choruses. While the calling behavior is effective for mate attraction, it requires high energy consumption. In contrast, satellite behavior is an alternative mating strategy in which males deliberately stay silent in the vicinity of a calling male and attempt to intercept the female attracted to the caller, allowing the satellite males to reduce their energy consumption while having a chance of mating. Here we propose a hybrid dynamical model in which male frogs autonomously switch among three behavioral states (i.e., calling state, resting state, and satellite state) due to the excitatory and inhibitory interactions. Numerical simulations of the proposed model demonstrated that (1) both collective choruses and satellite behavior can be reproduced and (2) the satellite males can prolong the energy depletion time of the whole aggregation while they split the maximum chorus activity into two levels over the whole chorusing period. This study highlights the importance of the multiple behavioral types and their transitions for the performance of the whole aggregation.

Know your enemy: The dragonfly Erythrodiplax fusca (Libellulidae) uses eavesdropping to obtain information about potential rivals

Animals can eavesdrop on other competitors during territorial defense disputes to better choose rivals weaker than themselves and increase the chances of monopolizing resources. In dragonflies, males often compete for access to water bodies, which attract sexually receptive females to mate and lay eggs. During the breeding season, satellite males can observe fights between territory owners and intruders and, therefore, obtain information about potential rivals through visual cues. Consequently, weaker competitors may face more intense competition than stronger ones when defending a territory. In this study, we conducted field experiments with the dragonfly Erythrodiplax fusca to investigate whether eavesdropping on territorial disputes, using visual cues, affects the intensity of competition that territory owners face. We recorded the number of intruders that engage in disputes against males that recently occupied territories in two groups: the “eavesdropping” group (i.e., individuals with access to rivals’ prior information) and the control group (i.e., competitors with no access to prior information). The number of intruders was greater in the eavesdropping group compared to the control group. This effect depended on the interaction between the size of the territory owners and the presence of eavesdropping. The number of intruders decreased with increase in the size of the owners in the presence of eavesdropping, but this relationship did not occur in the control group. We discuss the implications of our findings for the male decision-making process to initiate agonistic disputes and how investigating eavesdropping behavior can improve current models of conflict resolution in animals.

Long‐term Effects of Brazilian Red Propolis Ethanolic Extract on Biochemistry and Histopathological Parameters of Wistar Rats

Propolis is a natural product extensively used in the drug and food industry around the world due to its medicinal properties. Among the most prominent types of propolis in the world there is the red type, and one of its production centers is the Brazilian northeast. Several biological activities from Brazilian red propolis have been studied and its efficacy has been proved; however, there are few studies that report the safety of its use. This study assessed the biochemical and morphological long‐term effects of oral consume (90 days) of Brazilian red propolis extract in Wistar rats (Rattus norvegicus, males and females). Animals were divided into three groups: vehicle (polyethylene glycol 15%), red propolis (1000 mg/kg body weight – limit test described by the OECD 408, 2018) (n=10 per group), and satellite (treated with propolis at the same dose) (n=5 per group). The satellite group had a recovery period of 30 days after daily oral gavage of 90 days, before euthanasia. During the treatment period, water and food consumption and animal weight analysis were monitored. After the experimental period, animals were euthanized and samples were collected for biochemical and histopathological analyses. Statistical analysis was performed using GraphPad Prism software version 6.0. The experimental protocol for the use of animals was approved by the Ethics Committee on Animal Use (N° 9701030418). Alterations in the weight of males treated with red propolis were observed (propolis and satellite), being the groups with lower body mass during the experiment. The red propolis group also presented an increased water intake, compared to the other groups. On the other side, the males of the satellite group presented lowest food consumption compared to the other groups. A greater relative mass of the liver in animals of red propolis groups of both sexes were noticed. However, biochemical alterations in hepatic and renal parameters were detected just in the males. Urea levels increased in the propolis and satellite groups, whereas creatinine decreased just on the propolis group. The alanine aminotransferase (ALT) levels increased on the red propolis group, and the aspartate aminotransferase (AST) values increased on the satellite group. Total protein content decreased on animals of propolis and satellite groups of both sexes. Similarly, on the propolis and satellite males, the triglycerides levels decreased. Despite the detection of biochemical alterations, no histopathological changes were detected in the organs of any group. In conclusion, Brazilian red propolis extract in a higher dose, showed no signs of immediate toxicity. However, some alterations in the relative weight of the liver and on some renal and hepatic function indicators were observed. These results, suggests that the chemical composition ‐isoflavonoids, pterocarpans and polyprenylated benzophenones‐, and the higher dosage may be strongly related to the potential sub‐chronic toxic effects observed in this study and that its action may be sex‐dependent manner.

Ejaculate Allocation and Sperm Characteristics Differ among Alternative Male Types in a Species of Fish with Cooperation and Competition among Unrelated Males.

Sexual selection arising from sperm competition has driven the evolution of immense variation in ejaculate allocation and sperm characteristics not only among species, but also among males within a species. One question that has received little attention is how cooperation among males affects these patterns. Here we ask how male alternative reproductive types differ in testes size, ejaculate production, and sperm morphology in the ocellated wrasse, a marine fish in which unrelated males cooperate and compete during reproduction. Nesting males build nests, court females and provide care. Sneaker males only “sneak” spawn, while satellite males sneak, but also help by chasing away sneakers. We found that satellite males have larger absolute testes than either sneakers or nesting males, despite their cooperative role. Nesting males invested relatively less in testes than either sneakers or satellites. Though sneakers produced smaller ejaculates than either satellite or nesting males, we found no difference among male types in either sperm cell concentration or sperm number, implying sneakers may produce less seminal fluid. Sperm tail length did not differ significantly among male types, but sneaker sperm cells had significantly larger heads than either satellite or nesting male sperm, consistent with past research showing sneakers produce slower sperm. Our results highlight that social interactions among males can influence sperm and ejaculate production.

The Evolution of Social Behaviour

The Evolution of Social Behaviour

Reproductive strategy of bachelors in a snub-nosed monkey (Rhinopithecus bieti) all-male unit.

Snub-nosed monkeys exhibit a rare multilevel social system composed of several one-male units (OMU) and at least one all-male unit (AMU). The AMU comprises males who are blocked from access to females by resident males in the OMUs, and how these satellite males achieve reproductive success is still unclear. To investigate their reproductive strategies, we focused on the AMU in a band of provisioned black-and-white snub-nosed monkeys (Rhinopithecus bieti) in Yunnan, China. Behaviors that AMU males use to gain access to females (i.e. immigration, male takeover, and sexual interaction with females) were recorded and compared with resident OMU males to explore how AMU bachelors achieve reproductive success when they are denied stable access to females. We found that in response to solicitation from females, adult and sub-adult members of the AMU responded more actively than resident males, and the bachelors actively initiated mating with females when the latter's resident male was temporarily absent. These mating opportunities mostly coincided with the peak mating season in OMUs, and probably allowed bachelors to sire some offspring. We also found that for some AMU adults, taking over an OMU is the main strategy used to gain stable access to females, and these males repeatedly migrate between bands. AMU members therefore show multiple strategies that allow them to gain some degree of reproductive success.

Variation in Lek Attendance and Copulation Success of Independent and Satellite Male Ruffs Calidris pugnax

In lekking male Ruffs, three genetically distinct morphs compete for copulations with the visiting females. Faeder males are female mimics, whereas Independents and Satellites show marked sexual dimorphism, including an elaborate ornamental plumage. Independent males holding a territory on a lek (Residents) have higher mating success than Independents that do not (Marginals), whereas heterogeneity among Satellites is less well understood. Therefore, we compare variation in lek attendance and copulation success between Independent and Satellite males on five leks in northern Norway, over one mating season. Among Independents, Residents were more likely to return to the same lek between years, had longer tenure, higher visitation rate, longer visit duration, fewer arrivals and departures from the lek together with females, and higher daily and seasonal lek attendance than Marginals. We observed qualitatively similar between-individual variation in behaviour among Satellites. Thus, we define two types of individuals: Central Satellites with high lek attachment and Peripheral Satellites with low lek attachment. A notable difference between the morphs was that some Central Satellites (but no Resident Independents) were highly attached to more than one lek on the same day. Lek attendance correlated with copulation success, both on a daily basis and considering the entire season, and this relationship did not differ significantly between the morphs. Given that the mere presence of a male on the lek when a female visited to copulate predicted his copulation success, the unequal distribution of copulations on a lek can be largely explained by unequal lek attendance. After correction for variation in presence, one male on each lek obtained more than his expected share of copulations. Our observations suggest that endurance rivalry, whereby energetic limitations determine the lek attendance of competing males, could be an important determinant of copulation success on Ruff leks.

Experimentally induced variation in neuroendocrine processes affects male reproductive behaviour, sperm characteristics and social interactions.

While extensive research has focused on how social interactions evolve, the fitness consequences of the neuroendocrine mechanisms underlying these interactions have rarely been documented, especially in the wild. Here, we measure how the neuroendocrine mechanisms underlying male behaviour affect mating success and sperm competition in the ocellated wrasse (Symphodus ocellatus). In this species, males exhibit three alternative reproductive types. "Nesting males" provide parental care, defend territories and form cooperative associations with unrelated "satellites," who cheat by sneaking fertilizations but help by reducing sperm competition from "sneakers" who do not cooperate or provide care. To measure the fitness consequences of the mechanisms underlying these social interactions, we used "phenotypic engineering" that involved administering an androgen receptor antagonist (flutamide) to wild, free-living fish. Nesting males treated with flutamide shifted their aggression from sneakers to satellite males and experienced decreased submissiveness by sneaker males (which correlated with decreased nesting male mating success). The preoptic area (POA), a region controlling male reproductive behaviours, exhibited dramatic down-regulation of androgen receptor (AR) and vasotocin 1a receptor (V1aR) mRNA following experimental manipulation of androgen signalling. We did not find a direct effect of the manipulation on male mating success, paternity or larval production. However, variation in neuroendocrine mechanisms generated by the experimental manipulation was significantly correlated with changes in behaviour and mating success: V1aR expression was negatively correlated with satellite-directed aggression, and expression of its ligand arginine vasotocin (AVT) was positively correlated with courtship and mating success, thus revealing the potential for sexual selection on these mechanisms.

Influence of conspecific and heterospecific cues on phonotaxis behavior in a polyandrous treefrog

Although a large proportion of the literature has addressed the direction and preference of female choice in frogs, research about how males locate a breeding site and what strategies are involved in aggregation has been much less explored. By using broadcasting tests on a polyandrous choral treefrog Rhacophorus prasinatus, we examined how male frogs use conspecific and heterospecific signals to locate a chorus by asking the following questions: (1) Do male frogs prefer to join a large or a small chorus? (2) Do male frogs prefer to approach a high-quality or a low-quality male? (3) Do males utilize heterospecific calls to locate the potential breeding sites? (4) Do male frogs orient toward or avoid choruses containing heterospecific calls? Our results indicated that males prefer to join a large rather than small chorus. Low-quality males tend to approach high-quality males, which might be explained as the sneaking behavior of satellite males. Furthermore, males may use heterospecific calls delivered by a noncompetitive sympatric species (a ranid frog) to find potential breeding sites, but not by a sympatric competitor (another rhacophorid frog) that occupies a similar niche. Although the males did not show significant preference between conspecific chorus and mixed-specific chorus in the broadcasting tests, recapture records in the wild indicated that a high ratio of males would leave the mixed-specific choruses and move toward conspecific choruses in the next capture event. Although a large proportion of the literature has addressed the direction and preference of female choice in frogs, research about how males locate a breeding site and what strategies are involved in aggregation has been much less explored. Our study represents one of the first to test the orientation of males during breeding season, when the spatial scale in the experimental design is comparable to the real situation in the wild. Our results supported the prediction that both conspecific and heterospecific cues are used as information for males to assess the quality of breeding sites. Heterospecific calls may play dual functions for the males, which might become interference when coexisting with conspecific calls but may also provide cues for a potential habitat when conspecific calls are absent.

Obligate, but not facultative, satellite males prefer the same male sexual signal characteristics as females

Signalling is energetically expensive and increases the risk of predation and parasite infection. To balance the costs and benefits of mate attraction, individuals may adopt an alternative mating strategy such as satellite behaviour, in which nonsignalling males will settle near signalling males and attempt to intercept approaching females. While many suggest that alternative strategies are ‘making the best of a bad job’, little research has examined whether satellites, particularly obligate satellites, have the potential to increase their mating success by preferentially targeting more attractive signallers. Using the Pacific field cricket, Teleogryllus oceanicus, we tested the hypothesis that males are more likely to act as satellites to signalling males with particularly attractive songs, as these callers are likely to attract the most females. In this species, a novel male wing mutation, ‘flatwing’, renders some males unable to call. Flatwings are obligate satellites, while nonmutated, normal-wing males switch between calling and satellite strategies. We presented males with calling song models varying in the percentage of long-to-short chirps, a characteristic important in female choice. As was shown for females in previous work, flatwings exhibited a strong preference for calling songs composed of 60% long chirp. Normal wing males did not prefer any particular calling song model. Our results lead to the paradoxical conclusion that males with highly attractive songs may not have the highest mating success. Such male preference for male sexual signals may oppose selection by females and increase competition between signalling and satellite males. This could potentially slow the rate of male trait evolution and influence the evolution of male competition.

Red operculum spots, body size, maturation and evidence for a satellite male phenotype in non‐native European populations of pumpkinseed Lepomis gibbosus

AbstractCarotenoid‐based pigmentation is a striking feature of many taxa, yet the function, if any, of colour traits is often unclear. Pumpkinseed Lepomis gibbosus, a widely introduced freshwater sunfish that exhibits alternative male mating strategies, express a striking, red operculum spot. To investigate the potential function of this red spot as a signal in this species' mating system, we determined the presence and measured the size of red operculum spots in fish collected from 12 populations in five European countries in which pumpkinseed is an established non‐native species. We subsequently related the presence and size of the red spot to body size and mating strategy, based on an analysis of relative gonad size (gonado‐somatic index, GSI), using a mixed modelling approach. The study demonstrated that the presence of a red operculum spot in pumpkinseed is associated with sexual maturation, with GSI frequency distributions suggesting that cuckolders in some non‐native populations comprised both sneaker and satellite males, the latter not having previously been reported for this species. Further, the size of red spot correlated strongly with body size in parental and cuckolder males, although there was no difference in the presence or size of the red operculum spot between male mating strategies. The function of a red operculum spot in females is not clear but may be partly mediated by pleiotropic genetic mechanisms. Red operculum spots appear to function as signals of male maturation and body size in pumpkinseed, irrespective of mating strategy.

Discovering structural complexity and its causes: Breeding aggregations in horseshoe crabs

In some species, especially those that form breeding aggregations, males form groups around females vying for fertilizations. These mating groups are often highly variable in size even during a single breeding event. We examined this variation in the American horseshoe crab, Limulus polyphemus, a species in which some females (nesting in pairs) attract additional males (satellites) and spawn in groups whereas others spawn only with their attached male. The observed distribution of group sizes often consists of an overabundance of pairs with no satellite males and groups with large numbers of satellites. We characterized this variation using well-known models of count data, such as the Poisson and negative binomial distributions, and evaluated how operational sex ratio (OSR) and pair density contribute to the observed variation. We complemented this descriptive approach with spatially explicit simulations of the group formation process. By comparing our simulation results to the observed breeding aggregation data, we identified how simple behavioural rules might contribute to the variation we observe. Those rules amount to hypotheses about pair and satellite arrival at the beach and satellite sampling of and choice among pairs. We found that the observed variation could be explained by a consistent high frequency of females that attract satellites in combination with males that sample different fractions of the beach as pair density and OSR vary. Furthermore, our simulations suggested that males are not choosy in joining pairs on the beach, despite variation among pairs in the fertilization success satellites can achieve. This suggests that new insights might come from investigating the costs and benefits of male choice and the sensory mechanisms satellite males use to assess the breeding aggregation before coming ashore.

Sperm competition shapes gene expression and sequence evolution in the ocellated wrasse.

Gene expression differences between males and females often underlie sexually dimorphic phenotypes, and the expression levels of genes that are differentially expressed between the sexes are thought to respond to sexual selection. Most studies on the transcriptomic response to sexual selection treat sexual selection as a single force, but postmating sexual selection in particular is expected to specifically target gonadal tissue. The three male morphs of the ocellated wrasse (Symphodus ocellatus) make it possible to test the role of postmating sexual selection in shaping the gonadal transcriptome. Nesting males hold territories and have the highest reproductive success, yet we detected feminization of their gonadal gene expression compared to satellite males. Satellite males are less brightly coloured and experience more intense sperm competition than nesting males. In line with postmating sexual selection affecting gonadal gene expression, we detected a more masculinized expression profile in satellites. Sneakers are the lowest quality males and showed both de-masculinization and de-feminization of gene expression. We also detected higher rates of gene sequence evolution of male-biased genes compared to unbiased genes, which could at least in part be explained by positive selection. Together, these results reveal the potential for postmating sexual selection to drive higher rates of gene sequence evolution and shape the gonadal transcriptome profile.

Sociogenetic structure in nests of the mud dauber wasp Trypoxylon (Trypargilum) albitarse (Hymenoptera: Crabronidae)

Trypargilum is a subgenus of solitary spider-hunting wasps whose males guard the nest, an unusual behaviour for male wasps. A male pairs with a female and copulates repeatedly with her during the nesting process, although females regularly copulate with satellite males, which employ an alternative reproductive strategy. The purpose of this paper was to determine the sociogenetic structure in twenty-nine nests of Trypoxylon albitarse sampled at six sites in Brazil. A total of 367 wasps were genotyped for eight species-specific polymorphic microsatellite loci. Genotypic segregation analyses were conducted to test whether the nests sampled were monogamic family groups. The results indicated that all the offspring in 12 of the 29 nests could be attributed to a single couple (genetic monogamy). Approximately 9% of the offspring probably resulted from extra-pair copulations and 3% of the total offspring were attributed to a second mother (usurpation by conspecific females, a form of intraspecific parasitism). The sequential replacement of parents throughout the nesting process indicates that the 29 nests analyzed included 35 family groups. Thus, our findings indicate that Trypoxylon albitarse has a predominantly monogamous genetic mating system, despite the social polygamy reported in previous studies.

Foraging competition in larger groups overrides harassment avoidance benefits in female reindeer (Rangifer tarandus).

Male harassment toward females during the breeding season may have a negative effect on their reproductive success by disturbing their foraging activity, thereby inducing somatic costs. Accordingly, it is predicted that females will choose mates based on their ability to provide protection or will aggregate into large groups to dilute per capita harassment level. Conversely, increasing group size may also lead to a decrease in foraging activity by increasing foraging competition, but this effect has rarely been considered in mating tactic studies. This study examined the importance of two non-exclusive hypotheses in explaining the variations of the female activity budget during the breeding season: the male harassment hypothesis, and the female foraging competition hypothesis. We used focal observations of female activity from known mating groups collected during the breeding season from a long-term (15 years) study on reindeer Rangifer tarandus. We found that females were more disturbed (i.e., spent less time feeding) in the presence of young dominant males, and marginally disturbed in the presence of satellite males, which supports the male harassment hypothesis. We also found that female disturbance level increased with group size, being independent of the adult sex ratio. Consequently, these results rejected the dilution effect, but strongly supported the foraging competition hypothesis. This study therefore highlights a potential conflict in female behaviour. Indeed, any gains from harassment protection were negated by an increase of 6-7 females, since adult males lead larger groups than young males.

Neural Gene Expression Profiles and Androgen Levels Underlie Alternative Reproductive Tactics in the Ocellated Wrasse, Symphodus ocellatus

AbstractDiscrete variation in reproductive behavior and physiology is observed in diverse taxa. Although it is known that most within‐sex alternative reproductive tactics arise as a consequence of phenotypic plasticity, relatively little is known about differential neural gene expression among plastic alternative reproductive phenotypes. In the ocellated wrasse Symphodus ocellatus, males exhibit one of three alternative tactics (nesting, satellite, and sneaker) within a reproductive season, but switch tactics between years. Satellites and sneakers spawn parasitically in dominant (nesting) males' nests, but only nesting males provide parental care. Nesting and satellite males show transient cooperative defense of nests against sneakers. Here, we analyze circulating sex steroid hormone levels and neural gene expression profiles in these three male phenotypes and in females. 11‐ketotestosterone (but not testosterone) was highest in nesting males, while estradiol was highest in females. Brain transcriptomes of satellites and females were most similar to each other and intermediate to nesting and sneaker males. Sneakers showed more total expression differences, whereas nesting males showed higher magnitude expression differences. Our findings reveal the surprising extent to which neural gene expression patterns vary across reproductive tactics that vary in a number of social traits, including aggression, territoriality, and cooperation, providing important insights into the molecular mechanisms that may underlie variation in cooperative and reproductive behavior.

Why males and females look different

Why do males and females look different? In “Odd Couples: Extraordinary Differences Between the Sexes in the Animal Kingdom,” (2013, Princeton University Press, p. 312), Daphne J. Fairbairn provides a scrupulous catalog of possible answers, perhaps the most detailed collection of animal sex differences since Darwin’s 1874 “The Descent of Man and Selection in Relation to Sex.” Sexual dimorphism is the condition in which males and females exhibit distinct phenotypes, beyond physiological traits involved with reproduction. Fairbairn’s volume is supplied with some of the best examples of such differences now known, and the disparate sources of data are pressed into compelling shape by a talented scholar and careful experimentalist. Fairbairn’s manifesto is, “an overtly Darwinian approach to understanding sexual differences” (p. 3). She notes that when selection operates in sex-specific ways, “we expect trait distributions typical for each sex to be adaptive for that sex” (p. 4), and she launches the reader into this view of dimorphism with sweeping taxonomic and gender-modified scope. We learn of lumbering male elephant seals, who in the throes of their ardor may annihilate the offspring of their future mates; of great bustards, giant Eurasian cranes whose males shove rivals and take blows to the face like bear-pit pugilists while females watch nearby; of shellcarrying cichlid fish, whose territorial and satellite males dart and parry for opportunities to ejaculate into snail shells containing females’ unfertilized ova. As vertebrates, we humans are most familiar with mating systems in which males are larger or somehow more elaborate than females. Fairbairn answers this preexisting bias with fascinating contrasts, weaving tales of yellow garden spiders and blanket octopus, whose gigantic females either squat in the center of conspicuous webs, or float huge and enigmatic over tropical reefs, each attended by males of their species as much as 40,000 times smaller in size. We learn of giant seadevil anglerfish, whose enormous, fang-jawed females host tiny males, who cling to female undersides by their own peculiar mouths, absorbing nutrients from a shared bloodstream and dangling close enough to their mate’s genitalia to ensure successful spawning. Fairbairn details the divergent life histories of bizarre, deep-sea bone worms whose females embed their bulbous bodies within decaying skeletons of whales, and maintain hundreds of minute suitors within their translucent skins. Lastly, she describes shell-burrowing barnacles, in which embedded females may (or may not—45% of females fail to mate) host posses of minuscule males with colossal, inflatable penises that may exceed each little fellow’s corporal dimensions by as much as eight times. The density of information and much delightful prose make this a fascinating read for lay and professional readers alike. Footnotes and appendices comprise nearly one-third of the book. One diagram describes the distribution of sexual dimorphism among 73 animal classes, a synthesis across 1.4 million species that is the first I have seen of its kind. Fairbairn glides among the animals with remarkable skill, and does Darwin one better with abundant recent data. In each chapter, she recounts male and female life spans, the fractions of individuals who do and do not mate, and the numbers of offspring that individuals in each sex produce. The raw materials are here to make concise, quantitative statements about how a sex difference in the variance in relative fitness (also known as the opportunity for sexual selection; Wade 1979) can explain the magnitude and direction of sexual dimorphism. But each chapter ends without an attempt. Offspring numbers are what Fairbairn considers “the currency of Darwinian fitness,” yet the trove of such information presented is used mainly for implication. Fairbairn concludes, “the enduring message is that there is no one way of being a male or a female animal . . . there is no “normal” or “typical” pattern of sexual differentiation across the animal kingdom,” and furthermore that the lack of sex differences in externally fertilizing species “remains a mystery” (p. 165). I found such capitulation

First report of satellite males during breeding in Leptodactylus latrans (Amphibia, Anura)

The occurrence of satellite males is a common behaviour across anuran taxa. Satellite males take peripheral positions to calling males and adopt tactics in an attempt to intercept females that are attracted to calling males to increase their own mating success. Satellite males could have an inexpensive form of mate-locating, avoiding predators, and saving energy. Furthermore, this strategy could play an important role in the genetic structure of populations. The genus Leptodactylus consists of approximately 70 described species that are widely distributed in South America. The literature on the biology of this genus is extensive; however, we found only two reports on the existence of multi-male mating behavior in the genus ( L. chaquensis and L. podicipinus ). Herein, we report intrasexual competition in the form of satellite behavior in Leptodactylus latrans , where multiple satellite males were observed in close vicinity to a calling male.