Discriminating Males and Unpredictable Females: Males Bias Sperm Allocation in Favor of Virgin Females

When both sexes mate with multiple partners, theory predicts that males should adjust their investment in ejaculates in response to the risk and/or intensity of sperm competition. Here, we demonstrate that, in the harlequin beetle riding pseudoscorpion, Cordylochernes scorpioides, males use cues deposited on females by previous males to distinguish between virgin, once‐mated, and multiply‐mated females and adjust sperm allocation accordingly. Sperm number declined in direct proportion to the number of previous males, with virgin females receiving nearly three times more sperm than females exposed to three previous males. Given the lack of first‐male sperm precedence in C. scorpioides, this pattern is not consistent with current sperm competition models and appears best explained by a significant risk of wasting ejaculates on deceitful, mated females. In C. scorpioides, males transfer sperm indirectly to females via a stalked spermatophore deposited on the substrate. Mated females often feign sexual receptivity and cooperate throughout mating, only to reject the sperm packet produced by the male. While indirect sperm transfer facilitates a high level of female deceit and control, females of many species are able to influence the number and fate of sperm transferred during copulation and are likely to conceal their sexual unreceptivity to minimize male retaliation. If males cannot accurately assess female receptivity, increased risk of sperm rejection by mated females could outweigh the risk of sperm competition and favor greater sperm allocation to virgin females.     

Public Information Influences Sperm Transfer to Females in Sailfin Molly Males

In animals, including humans, the social environment can serve as a public information network in which individuals can gather public information about the quality of potential mates by observing conspecifics during sexual interactions. The observing individual itself is also a part of this information network. When recognized by the observed conspecifics as an audience, his/her presence could influence the sexual interaction between those individuals, because the observer might be considered as a potential mate or competitor. One of the most challenging questions in sexual selection to date is how the use of public information in the context of mate choice is linked to the fitness of individuals. Here, we could show that public information influences mate-choice behaviour in sailfin molly males, Poecilia latipinna, and influences the amount of sperm males transfer to a female partner. In the presence of an audience male, males spent less time with the previously preferred, larger of two females and significantly more time with the previously non-preferred, smaller female. When males could physically interact with a female and were faced with an audience male, three audience females or no audience, males transferred significantly more sperm to a female partner in the presence of an audience male than with female audience or no audience and spent less time courting his female partner. This is the first study showing that public information use turns into fitness investment, which is the crucial factor to understand the role of public information in the dynamic processes in sexual selection.     

Use of Social and Ecological Information in Tamarin Foraging Decisions

A major consequence of group living is that foragers may rely on social information in addition to ecological information to locate feeding sites. Although conspecifics can provide cues as to the spatial location of food patches, individual foraging decisions also must include some assessment of the likelihood of obtaining access to a resource other group members seek. This likelihood differs in the 2 models generally proposed to explain intragroup social foraging: the information-sharing model and the producer-scrounger model. We conducted an experimental field study on wild groups of emperor (Saguinus imperator) and saddleback (S. fuscicollis) tamarins to determine the foraging strategies adopted by individual group members and their relationship to social rank, food intake, and the ability to use ecological and social information in making intra-patch foraging decisions. Individual tamarins applied different behavioral strategies compatible with a finder-joiner paradigm to solve foraging problems. About half of the individuals in each study group initiated 74%–90% of all food searches and acted as finders. Most alpha individuals adopted a joiner strategy by monitoring the activities of others' to obtain a reward. The individual arriving first at a reward platform enjoyed a finder's advantage. Despite differences in search effort, both finders and joiners presented similar abilities in learning to associate ecological cues with the presence of food rewards at our experimental feeding stations. We conclude that within a group foraging context, tamarins integrate social and ecological information in decision-making.     

Mutual Mate Assessment in Wolf Spiders: Differences in the Cues Used by Males and Females

When males engage in conspicuous courtship displays, it seems obvious that females would use characteristics of that display in mating decisions. However, males must also have a way to identify and evaluate females prior to engaging in what might be a costly mating ritual. Although it was known that female wolf spiders of the species Pardosa milvina (Araneae; Lycosidae) attract males using volatile chemical cues, the nature of the cues used by males and females in mate selection had not been investigated. Specifically we determined whether males could detect the mating status of the female and if chemotactile cues from the female played a role in that process. In addition, we quantified conspicuous aspects of the male courtship (leg raises and body shakes) to determine if courtship intensity was related to female choice. Although repeated mating occurred in our studies, males were more likely to court and mate with virgin females. Males used substrate‐borne cues deposited by females to discriminate between mated and virgin females. Females used the conspicuous behaviors of males during courtship, body shakes and leg raises, in mate selection. Thus males and females use different kinds of information and different sensory modalities to assess the suitability of a potential mate.     

Keeping Signals Straight: How Cells Process Information and Make Decisions

As we become increasingly dependent on electronic information-processing systems at home and work, it’s easy to lose sight of the fact that our very survival depends on highly complex biological information-processing systems. Each of the trillions of cells that form the human body has the ability to detect and respond to a wide range of stimuli and inputs, using an extraordinary set of signaling proteins to process this information and make decisions accordingly. Indeed, cells in all organisms rely on these signaling proteins to survive and proliferate in unpredictable and sometimes rapidly changing environments. But how exactly do these proteins relay information within cells, and how do they keep a multitude of incoming signals straight? Here, I describe recent efforts to understand the fidelity of information flow inside cells. This work is providing fundamental insight into how cells function. Additionally, it may lead to the design of novel antibiotics that disrupt the signaling of pathogenic bacteria or it could help to guide the treatment of cancer, which often involves information-processing gone awry inside human cells.There are nearly 10¹³ cells in every human, and at least as many bacterial cells living in or on us [1]. Each of these cells, human and bacterial, is a sophisticated, information-processing device. Cells have evolved the remarkable ability to appraise their internal and external environments and then to act on the information gathered. They can decide whether to stay where they are or crawl away, whether to grow or hunker down until conditions improve, whether to produce one enzyme or another, and so much more. The ability to make decisions at the cellular level is absolutely critical to the survival and long-term proliferation of organisms throughout the biosphere—but how do individual cells accomplish this feat without the luxury of a brain or nervous system? The answer lies with a diverse and important set of molecules found inside all cells called signal transduction proteins [2].These signaling proteins do not typically carry out a specific metabolic process on their own or directly participate in the growth or maintenance of cells. Instead, their job is to effectively keep tabs on the environment and respond to various cues or stimuli by activating (or inactivating) the appropriate cellular processes. Signaling proteins are, in effect, pulling the puppet strings that enable cells to survive, grow, and reproduce.The sequencing of genomes from many different species in the late 1990s and early 2000s offered the first comprehensive assessment of the arsenal of signaling proteins available to individual cells. The signaling proteins encoded by most organisms often number in the hundreds but typically belong to a small number of protein families. The individual members of a given family are sometimes highly related at the sequence and structural levels.In many ways, the observation that cells harbor only a small number of signaling protein families makes sense. Over the course of evolution, cells must expand and diversify their information-processing capabilities to respond to new environments and new signals. It is much easier for cells to duplicate and then modify an existing signaling modality than it is to create a brand new form of signaling protein from scratch. But the benefit of expanding an organism''s signaling repertoire through duplication comes at a significant cost: how do individual cells keep signals straight and avoid unwanted cross-talk? How is specificity ensured to maintain the fidelity of information flow inside cells?A reasonable analogy here is the telecommunication network we each rely on every day to interact with one another. For example, if I want to call my mother, I need some way to make sure my cell phone connects with her cell phone, without crossing lines or inadvertently calling someone else. This specificity is dictated by the unique phone number I enter. Is there an equivalent system, or code, used by signaling proteins to ensure their specificity?My lab set out to address this question many years ago in bacterial cells, which rely on so-called two-component signaling pathways to perform many of their most complex information-processing tasks [3,4]. These signaling pathways involve one protein, called a histidine kinase, that resides in the membrane surrounding a cell and "listens" to the environment (Fig 1). If a signal or stimulus registers on the extracellular portion of the protein, the intracellular portion of the histidine kinase protein responds by grabbing a phosphate from ATP and attaching it to a particular histidine amino acid, a process called autophosphorylation. The kinase then docks with a second protein, called a response regulator, and passes the phosphate group to it. This regulatory protein is subsequently released to effect cellular changes, often by turning on a battery of genes that help cells cope with the environmental change or stimulus originally detected by the kinase. But how does a kinase "know" which response regulator, or substrate, to dock with and signal to?Open in a separate windowFig 1Specificity of signaling pathways.Two pathways are shown. Each initiates with a sensor kinase (orange) that can sense an extracellular signal and respond by phosphorylating itself using ATP. The phosphate group from ATP (circled ''P'') can then be passed to a substrate (blue), typically a regulatory protein that can effect changes in cellular behavior. Critical to the fidelity of information flow through these pathways are a set of ''specificity residues'' on each protein that are matched such that a kinase signals only to the correct substrate.We showed that this choice, or partner specificity, is intrinsic to the kinase, meaning that the kinase has an innate ability to discriminate between the right partner and all other possible substrates, without relying on other factors inside cells [5]. This exquisite specificity is ultimately determined by a small number of amino-acid residues in the kinase located at positions in the protein near the phosphorylated histidine [6]. Each kinase has a unique set of residues at these key positions that enable it to interact exclusively with its partner, or cognate substrate, which contains a complementary set of residues (see Fig 1). Together, these paired residues (called specificity residues) in kinases and substrates form a code that ultimately ensures signals are transmitted properly inside cells.Why do we care how signals get passed inside bacteria? Although my own lab''s work on this topic is driven mainly by a curiosity about how bacteria process information, this work has several potential applications. First, it turns out that many bacterial pathogens rely on two-component signaling proteins to infect humans, so a deeper understanding of how these proteins work may enable the design of novel antibiotics that target them [7]. Like cyberattacks that seek to disrupt computer-based information networks, drugs that disrupt the information-processing of pathogenic bacteria could cripple them. Understanding the basis of signaling specificity may also enable efforts to rationally engineer bacteria as biosensors [8]. As already noted, bacteria use histidine kinases to sense and respond to a spectacular diversity of molecules and compounds in their environments. By understanding how they signal in response to these various stimuli, we can now reprogram these histidine kinases to respond in novel ways, e.g. by producing an indicator of signal detection, such as light or fluorescence.The intrinsic and exquisite specificity of signaling proteins is, by no means, exclusive to bacteria. Exciting recent work has revealed that human kinases are also highly selective, using a defined set of specificity residues to ensure that they only phosphorylate the right substrate(s) inside cells [9]. Disrupting or altering this specificity could, in some cases, have catastrophic consequences for humans. For example, some types of cancer involve mutations in the specificity residues of signal-transducing kinases [10]. These mutations may be wreaking havoc on the information-processing capabilities of cells, possibly contributing to the unregulated growth and proliferation that is a hallmark of cancer. Thus, a better understanding of how signaling proteins ensure the specificity of their interactions may provide routes to new diagnostics or therapeutic strategies for the treatment of cancer.Whether any of these applications in biosensing or the treatment of bacterial infections and cancer ever come to fruition remains to be seen. Regardless, future efforts in this area promise to reveal the fundamental basis of information-processing in individual cells, a phenomenon that ultimately underlies the success and diversity of almost all life on the planet.     

Costs and Benefits of Food Foraging for a Braconid Parasitoid

The costs and benefits of food foraging for the insect parasitoid, Phanerotoma franklini Gahan (Hymenoptera: Braconidae), were examined. Feeding benefited P. franklini by increasing longevity, but did not influence egg maturation. Costs of feeding are represented by the time required to locate and consume food. Field observations of starved wasps revealed that wasps spent approximately 25% of their time grazing on substances on the surface of cranberry foliage. However, our initial laboratory tests to determine the value of these substances were inconclusive. We also examined how grazing behavior integrated with host foraging by comparing the attack rate of fed and unfed wasps held under different host densities. While feeding status did not affect the mean attack rate of wasps, starvation enhanced the probability that a wasp will engage in movement over the host plant foliage. We conclude that feeding benefits P. franklini by increasing longevity, that travel time to food sources is likely to be low, and that the observed food-foraging behavior does not appear to influence host-foraging efficiency.     

Sexual Imprinting in Zebra-finch Females: Do Females Develop a Preference for Males that Look Like Their Father?

Recently, it has been proposed that through sexual imprinting on their parents, young birds learn to discriminate between males and females. Support for this suggestion was given by a study on zebra-finch males Taniopygia guttata, which showed that males of this species develop a strong sexual preference for mother-like females over father-like females. The present study investigates whether zebra-finch females also develop a sexual preference for mates resembling the opposite-sex parent. The females used had been raised either by normal pairs, by white pairs or by pairs of both morphs. The preferences were tested by confronting these females with normal and white males, both in simultaneous two-stimulus tests and successive one-stimulus tests. In contrast to males, females raised by a pair of mixed-morph parents did not show a preference for mating partners of the opposite-sex-parent's morph. Instead, they showed a preference for males of the mother's plumage type. It is suggested that the difference in which sexual imprinting proceeds in males and females may be related to the different role each sex plays in the pair formation.     

Experience Matters: Females Use Smell to Select Experienced Males for Paternal Care

Mate choice and mating preferences often rely on the information content of signals exchanged between potential partners. In species where a female''s reproduction is the terminal event in life it is to be expected that females choose high quality males and assess males using some honest indicator of male quality. The Nereidid polychaete, Neanthes acuminata, exhibits monogamous pairing and the release of eggs by females terminates her life and larval success relies entirely on a male''s ability to provide paternal care. As such females should have developed reliable, condition-dependent criteria to choose mates to guarantee survival and care for offspring. We show that females actively chose males experienced in fatherhood over others. In the absence of experienced males dominance, as evident from male-male fights, is utilized for mate selection. The preference for experienced males is not affected by previous social interactions between the individuals. We show that the choice of the partner is based on chemical signals demonstrating a ‘scent of experience’ to females providing evidence for the role of chemical signals in sexual selection for paternal care adding to our understanding of the mechanisms regulating condition-dependent mate choice.     

Cognition in Males and Females with Autism: Similarities and Differences

The male bias in autism spectrum conditions (ASC) has led to females with ASC being under-researched. This lack of attention to females could hide variability due to sex that may explain some of the heterogeneity within ASC. In this study we investigate four key cognitive domains (mentalizing and emotion perception, executive function, perceptual attention to detail, and motor function) in ASC, to test for similarities and differences between males and females with and without ASC (n = 128 adults; n = 32 per group). In the mentalizing and facial emotion perception domain, males and females with ASC showed similar deficits compared to neurotypical controls. However, in attention to detail and dexterity involving executive function, although males with ASC showed poorer performance relative to neurotypical males, females with ASC performed comparably to neurotypical females. We conclude that performance in the social-cognitive domain is equally impaired in male and female adults with ASC. However, in specific non-social cognitive domains, performance within ASC depends on sex. This suggests that in specific domains, cognitive profiles in ASC are modulated by sex.     

Variability and Parasitoid Foraging Efficiency: A Case Study of Pea Aphids and Aphidius ervi

When a parasitoid is searching for hosts, not all hosts are equally likely to be attacked. This variability in attack probability may affect the parasitoid functional response. Using a collection of experiments, we quantified the functional response of Aphidius ervi (Hymenoptera: Braconidae), an insect parasitoid of the pea aphid Acyrthosiphon pisum (Homoptera: Aphididae). We measured variability in the number of hosts attacked by a foraging parasitoid both among plants and within plants. At the first scale, A. ervi, searching among plants containing different numbers of aphids, showed both aphid-density-dependent and aphid-density-independent variability in the number of aphids attacked per plant. Within plants, A. ervi selectively attacked second and third instar aphids relative to other instars. Furthermore, there was variability in the susceptibility of attack among aphids independent of instar. Variability in attack rates among aphids both among and within plants decreased parasitoid foraging efficiency, with the greatest decrease caused by among-plant variability. Furthermore, the decrease in foraging efficiency was greatest when the average number of aphids per plant was low, thereby transforming a strong Type II functional response into one approaching Type I.     

Foraging Cost of a Long Tail Ornament: An Experiment with Sand Martin Females

The handicap hypothesis assumes that sexual ornaments impose a viability cost upon the bearers. There have been few empirical tests of this assumption. Previous studies show evidence for the cost of a tail ornament in male birds: a negative relationship between an experimentally increased tail ornament (long tail streamers) and efficiency at foraging for nestlings. However, it must be admitted, that the apparent impairing effect of an elongated tail could be a result of a decrease in male parental effort in response to an increase of female parental effort, which might have occurred in response to increased male attractiveness (differential allocation of female parental effort). In this study, the effect of differential parental expenditure was eliminated by lengthening the tail in female, rather than male, sand martins ( Riparia riparia ). Tail-elongated females decreased the rate at which they fed nestlings, and captured more but smaller insects. There was no simultaneous increase of feeding rate in the males that could explain the decrease of feeding rate in the females. These results confirm the existence of a cost of a tail ornament in birds feeding in flight, as is expressed in terms of impaired flight and foraging capacity.     

Defence of Females by Dominant Males of Artibeus jamaicensis (Chiroptera: Phyllostomidae)

Defence of females by dominant males of the Jamaican fruit‐eating bat Artibeus jamaicensis was observed in two natural colonies over 2 yr. A log‐linear model was used to evaluate the frequency distribution of visits to harems by sex, season and agonistic interaction of dominant males. Harem group size varied from four to 18 females, with one adult male in the small and medium‐sized groups and two males in the large groups (> 14 females). A highly significant interaction was noted between the age and sex of the visitor and the response of the dominant male. Male visitors were attacked more often than female and juvenile visitors. Aggressive defence increased during the reproductive seasons, with dominant males showing more agonistic responses towards male visitors. An increase in the frequency of visits by male visitors was noted in harem groups that ranged in size from four to 12 females, but the frequency of male visits declined in harem groups that contained more than 14 females.