Low Mating Research Articles

The sublethal effects of tebufenozide on the precopulatory and copulatory activities of Choristoneura fumiferana and C. rosaceana

AbstractThe sublethal effects of tebufenozide, an ecdysone agonist, on the reproductive biology of Choristoneura fumiferana (Clem) and of Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), treated during the larval stage, were evaluated using two treatment methods: the force‐feeding method and the diet method. The percentage of mortality and the developmental time of survivors increased linearly with the concentration of tebufenozide used. This ecdysone analogue proved to be more toxic to C. fumiferana than to C. rosaceana. In C. rosaceana, the weight of males and females decreased proportionally with the dose ingested, but females were affected to a greater extent. This difference might be due to a greater consumption of the treated diet, or to a differential vulnerability to tebufenozide. Tebufenozide did not modify the pre‐copulatory activities associated with chemical communication in the females. However, the consumption of tebufenozide delayed ovarian maturation, causing a reduction in the fecundity of females. Treated males had smaller spermatophores and fewer eupyrene sperms in their bursa copulatrix and spermatheca, along with lower mating success. In C. fumiferana, tebufenozide delayed the females’ onset time of calling the first night after emergence, but did not affect the mean time spent calling or the production of the main component of the sex pheromone. The males showed significantly greater difficulty in executing oriented flight in a wind tunnel, although their mating success was not affected. We concluded that tebufenozide interferes with various aspects of the reproductive biology of males and females of C. fumiferana and C. rosaceana, including some pre‐copulatory behaviors associated with sex pheromone communication.

Mating behaviour and wing morph-related differences in the sexual activity of a flightless bug, Pyrrhocoris apterus (L.) (Heteroptera)

The sexual activity of long-winged (macropterous) and short-winged (brachypterous) adult males and females of Pyrrhocoris apterus (L.) from a temperate opulation (Czech Republic) were compared. The long-term arena tests revealed postponed sexual maturation and lower sexual activity (longer precopulatory period, longer inter-copulatory period, lower copulation frequency and shorter total duration of copulations) of macropterous pairs when compared with brachypterous pairs of the same age. The total sexual activity of both macropterous and brachypterous pairs increased with the age of the adults, but was significantly lower in the macropterous pairs. The short-term tests showed that the lowered mating propensity of macropterous pairs was mainly due to a decrease in the sexual receptivity of the females. It is the first demonstration of wing morph-related differences in the mating activity of P. apterus females and a first report of a mating disadvantage in the macropterous morph of a wingpolymorphic insect whose macropterous specimens have evolved flightlessness. Evolutionary transformation of the “oogenesis-flight” syndrome, that occurs in flying insects, into an “oogenesis-walking” syndrome in the flightless macropters of P. apterus is discussed.

Relationship between morphometric and genetic variation in pure and hybrid populations of the smooth and Montandon's newt (Triturus vulgaris and T. montandoni)

AbstractThe variation in 10 morphometric characters and the degree of sexual dimorphism in size and shape was studied in pure and hybrid populations of smooth Triturus vulgaris and Montandon's T. montandoni newts. Multivariate analyses showed pronounced interspecific differences in both sexes. Females differed mainly in traits related to general size, whereas males differed mainly in body proportions. Triturus vulgaris males possessed a relatively longer trunk and tail. Sexual size dimorphism was much stronger in T. montandoni, the females being the larger sex. In hybrid zone populations a general correlation between morphometric traits and nuclear genotypes was found. This does not, however, fully explain the variation in size and shape. Whereas the majority of genetically identified hybrids fell into the range of morphologically pure species, many genetically pure individuals were classified as morphometric intermediates. The linear relationship between the morphometric and genetic variation suggested no strong differential selection on the molecular markers and loci responsible for morphometric differences between species. The differences in the level of sexual size and shape dimorphism, however, suggest that females of both species show dissimilar mate preferences, and thus hybrid males may experience reduced fitness resulting from lower mating success.

Depensation, probability of fertilization, and the mating system of Atlantic cod (Gadus morhua L.)

AbstractAtlantic cod (Gadus morhua L.) have been severely overexploited and are currently at historic population lows, having declined 90% in the North Sea and 99% off northeast Newfoundland in recent decades. Slow rates of recovery and continuing declines may be attributable to depensation, defined as a reduction in per capita growth rate concomitant with reduced population size. Several potential causes of depensation relate to low mating success and consequent reduced production of offspring. We explore the empirical basis of one of these in Atlantic cod using egg fertilization and male abundance data obtained from 21 experimental populations generated by three independent research programmes. We find support for the hypotheses that (a) fertilization rate declines with abundance and (b) variance in fertilization rate increases as population size declines. The former identifies one potential mechanism underlying depensation in Atlantic cod. The latter has negative genetic consequences for effective population size (Ne), resulting in a decline in the ratio of Ne to census population size (Ne/Nc) with declining abundance. Our results may have general implications for the conservation biology of broadcast-spawning marine fish, particularly those with mating systems similar to that of Atlantic cod.

Efeito de tipos de acasalamentos e razões sexuais na seleção baseada no BLUP

Diferentes tipos de acasalamentos foram avaliados, por meio de dados simulados, em populações submetidas à seleção com base no BLUP, durante 50 gerações. Considerou-se uma característica quantitativa de herdabilidade 0,10 e a seguinte estrutura das populações de seleção: valores de razão sexual: 10, 20, 25 e 50; números de machos selecionados por geração: 10, 5, 4 e 2; tamanhos efetivos de população: 36,36; 19,05; 15,38; e 7,84, respectivamente. Em cada valor de razão sexual, as populações foram acasaladas segundo um dos tipos de acasalamentos: acasalamentos preferenciais de meios-irmãos e irmãos completos, acasalamentos preferenciais entre meios-irmãos, acasalamentos ao acaso, exclusão de acasalamentos entre irmãos completos e exclusão de acasalamentos de meios-irmãos e irmãos completos. Os parâmetros genéticos avaliados foram valores fenotípicos médios e consangüinidade média por geração. No menor valor de razão sexual, observou-se melhor desempenho fenotípico de todos os tipos de acasalamentos. Os tipos de acasalamentos que não permitiram acasalar irmãos proporcionaram maiores ganhos fenotípicos e foram os mais efetivos no controle da consangüinidade, no curto prazo, embora não tivessem impedido seu aumento e acúmulo, ao longo das gerações.

Assessment of Ovarian Development and Its Relation to Mating in Wild and Pond‐Reared Litopenaeus vannamei Shrimp in a Commercial Hatchery

AbstractThe present study compares three scales for evaluation of ovary development stage in wild and pond‐reared shrimp. An external visual scale was assessed according to color and size of ovaries observed through the exoskeleton in live shrimp by staff of a commercial hatchery. Shrimp were then sacrificed to obtain gonadosomatic index, and gonads were scaled according to their color and size upon dissection. Finally, a portion of ovaries was processed for histological analysis, from which oocyte diameters were obtained, and females were evaluated with another scale based on cytological organization of gonads and on frequency of oocyte sizes. The certainties of the external and internal scales were analyzed, based on differences in gonadosomatic index and oocyte diameter and by comparison with the more accurate scaling obtained by histological analysis. The external scale was, in general, less accurate than the internal scale. Maturation stage in pond‐reared shrimp was underestimated or overestimated more frequently than in wild shrimp. The implications for hatchery operation and possible reasons are discussed. Pond‐reared shrimp were found to have a non‐linear relation between gonad weight and body weight, but this relation was linear for the larger wild shrimp. This reduced the validity of gonadosomatic index in pond‐reared shrimp, which were still growing. Thus, oocyte diameter, which was not affected by body weight in growing shrimp, represents a more accurate numeric measure of ovary development. Spermatophores were found attached to the thelycum in females only at the cortical stage of maturation, independent of origin. However, a significant proportion of fully mature, pond‐reared shrimp did not have an attached spermatophore, possibly indicating lower mating success or poorer spermatophore adherence in these shrimp.

Mating success and fidelity to territories in a fallow deer lek: a female removal experiment.

A lek is a clump of male territories that females visit only for mating; it is quite a rare mating system among mammals. As we wanted to investigate the role of past male mating success on their fidelity to lek territories, we displaced fallow deer females by a lek (Lek A), i.e. we removed the resources for rutting males. They moved to a new area followed by some of the territorial males ('mobile' males) where they established a new lek (Lek B). Other males ('faithful' males) stayed on Lek A. The former had lower mating success and dominance ranking in the early, undisturbed part of the rut. After disturbance, the MS of faithful males was much reduced, while that of mobile males was higher on Lek B than it had been on Lek A. We then disturbed Lek B. Females returned to Lek A, and the mating success of faithful males reverted to its original level. Past mating success was the main factor predicting whether a male was faithful or mobile. We illustrated for the first time the importance of past experience in promoting lek fidelity; this experiment gives an insight into the mechanisms leading to the traditional use of leks.

Female reproductive decisions and parasite burden in a calopterygid damselfly (Insecta: Odonata)

There is currently a gap in sexual selection theory about how much the environment drives female mating decisions. We present field data that suggest that female sexual behaviour in the damselfly Calopteryx haemorrhoidalis is influenced by parasite burden. Male wing pigmentation in Calopteryx is a sexually selected trait that signals a male's ability to cope with eugregarine parasites (an intestinal parasite that feeds on the adult's ingested food). Because adult C.haemorrhoidalis females also show wing pigmentation, we examined whether this trait is similarly influenced by parasite burden and whether it may signal the female's reproductive value. MaleC.haemorrhoidalis defend riverine substrates that females use for oviposition. After copulation and during oviposition, females are guarded by the copulating male against intruder males. Alternatively, females may avoid mating and ‘steal’ an oviposition site within a male's territory. In the present study, we found that the amount of female wing pigmentation was negatively correlated with the number of eugregarines present. Females with more parasites produced fewer eggs, survived fewer days, spent less time during courtship, ‘inspected’ fewer males before mating, had a lower mating success, were guarded for less time during oviposition and engaged in fewer ‘stealing’ events during oviposition. The reduced egg production and survival of heavily infected females may result from eugregarine depletion of the females' consumed food reserves. Thus, to offset reduced longevity, heavily infected females may accept a mating more rapidly and mate with fewer males. ‘Stealing’ behaviour may be related to the female's differential use of sperm from some males, particularly high-quality males. Interestingly, males that mated with low-pigmented females showed greater variance in wing pigmentation than did males that mated with high-pigmented females. Possibly, female wing pigmentation may signal a female's reproductive value, which provides females with longer mate-guarding episodes and reduced interference from intruder males. This study points out one possible constraint, intestine parasites, that females may face during mating decisions. Because females in bad condition mate with males in both good and bad condition, this constraint may be pervasive enough to weaken the intensity of selection for a male sexually selected trait, wing pigmentation, and help to maintain its variation in phenotypic expression. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.

Bull Selection across Age Classes and Variable Female Reproductive Rates in an Open Nucleus Breeding Scheme for Dairy Cattle

Different bull selection strategies and female reproductive rates were simulated under various selection intensities and mating strategies in a nucleus with testing capacity of 80 cows. In all schemes, donor cows were selected after first lactation and bulls were progeny tested. In some schemes, non-progeny tested nucleus bulls could be selected. The nucleus was open on the male side but closed on the female side after nucleus born cows were available. Pedigrees of animals born outside the nucleus were sampled from the Finnish Ayrshire population. Female reproduction rate was either constant or variable. Schemes were compared according to genetic response, and risks measured by rate of inbreeding and coefficient of variation in genetic response between simulation years 5 and 20. Inclusion of one- or three-year-old bulls increased genetic response by 9% and rate of inbreeding up to 81%. Variation in female reproductive rate reduced genetic response by at most 8%. Increase in risks was averted by limiting the number of female full-sibs. Schemes with low selection intensity and factorial mating provided the best results.

Effects of tapeworm infection on male reproductive success and mating vigor in the red flour beetle, Tribolium castaneum.

Parasites may exert negative effects on host survivorship and reproductive success. The effects of parasites on female host fitness have been well documented; however, the effects of parasites on the reproductive success of male hosts and particularly the underlying mechanisms that alter male fitness are not well understood. Previous studies demonstrated that infection by rat tapeworm (Hymenolepis diminuta) reduced the fitness of male red flour beetles (Tribolium castaneum) in an environment of female mate choice and strong male-male competition. The present study determined the role of female mate choice and male insemination capacity on observed fitness reduction of male beetles by the tapeworm parasites. We found that infected males showed reduced mating vigor and consequently inseminated fewer females than did uninfected males. Specifically, tapeworm infection reduced the number of offspring sired by a male by 14-22% even when male-male competition and female mate choice were absent. Further, the insemination capacity of males diminished by 30% because of infection. Female beetles did not discriminate against infected males in precopulatory mate choice experiments. Copulatory courtship, a determinant of postcopulatory female choice, was not significantly different between infected and uninfected males. Hence, we concluded that female beetles did not show either pre- or postcopulatory choice against tapeworm-infected males. Therefore, tapeworm-induced reduction in the reproductive success of male beetles possibly results from altered reproductive biology, such as lower mating vigor and decreased sperm quantity or quality.

Low mating frequency of queens in the stingless bee Scaptotrigona postica 1 and worker maternity of males

Kin selection models of intracolonial conflict over the maternity of males predict that social hymenopteran workers should favour the production of sons and nephews over brothers when the effective mating frequency (me) of the queen is low (me 2. Stingless bees have been used to support these models in that me within the group is considered low and workers are thought often to monopolise the parentage of males. We genetically analysed 20 worker and 20 male pupae from each of 10 colonies of the stingless bee Scaptotrigona postica (= Scaptotrigona aff. depilis) using six microsatellite loci and demonstrate queen monandry in eight nests and apparent low me in the other two. However, four colonies contained an additional matriline, possibly due to queen supersedure (serial polygyny), which complicated their genetic structure. Across colonies, workers were responsible for the maternity of 13% of all males. These data are broadly in agreement with predictions from kin selection theory, though the question remains open as to why workers do not secure a greater share of male maternity in this and other stingless bee species in which workers are more closely related to nephews than brothers.

Sperm trading and sex roles in the hermaphroditic opisthobranch sea slug Navanax inermis : eager females or opportunistic males?

The sea slug Navanax inermis (Gastropoda, Opisthobranchia) is a well-known example of a simultaneous hermaphrodite in which mating partners trade sperm. According to previous work by others, sperm trading follows from a general preference for the female role when the expected variance in reproductive success in the male role is higher and the risk of failure therefore larger. However, this view contradicts theoretical and empirical studies of other systems, which predict a general preference for the male role; sperm trading is assumed to follow from the fact that individuals benefit from sperm receipt as a nutritional compensation for sperm investment. In this study, we investigate the behaviour of N. inermis in more detail. In addition to observations of regular pairs, we also paired individuals with a partner that had been isolated for 33 days in order to induce changes in sex-role preference in the non-isolated partner. We also collected all clutches produced throughout the study to check for signs of infertility as a consequence of allosperm depletion. Fertility of field-collected and isolated individuals suggested that sperm depletion occurs under natural conditions and may be caused by a lack of partners. Although this argues in favour of female preference, low mating rates both reduce variance in male reproductive success and remove the intent to use sperm for nutritional purposes, thus eliminating the conditions under which both hypotheses are intended to operate. The observational data indicate that animals are eager to mate as males, particularly at the beginning of a mating session. Intromissions lasted longer when a simultaneous intromission was received from the partner. Increases in intromission were recorded in non-isolated individuals with partners which were previously isolated and therefore more attractive as females. This response would not have been expected were the female role the preferred one. A summary of the arguments concerning preference for either gender suggests some preference for the male role, but indicates that sexual preferences may actually change or become neutral within an individual, even in the course of a mating session. Overall, our results clearly confirm previously published observations of sperm trading in N. inermis . © 2003 The Linnean Society of London . Biological Journal of the Linnean Society, 2003, 78 , 105 - 116. ADDITIONAL KEYWORDS: sexual conflict ‐ sexual selection ‐ Gastropoda ‐ reciprocity ‐ gamete trading ‐ sperm trading ‐ egg trading.

Isolation of suppressor mutants of phosphatidylinositol 3-phosphate 5-kinase deficient cells in Schizosaccharomyces pombe.

The ste12+ gene of Schizosaccharomyces pombe codes for a phosphatidylinositol (PI) 3-phosphate 5'-kinase, which is required for efficient mating. Suppressor mutants for sterility of ste12Delta cells were screened for. Most of the mutant genes turned out to be recessive. Six genes were cloned and the open reading frames responsible for the suppressor activity were identified. They included genes coding for proteins with domains homologous to calcium transporters, casein kinase II, UBC13, AMSH, Vps23p, and Vps27p of Saccharomyces cerevisiae. Disruption of these genes resulted in suppression of the defects of the ste12Delta cells, including low mating efficiency and formation of large vacuoles. Since many of these gene products are homologous to the proteins involved in vesicle transport, sterility caused by inactivation of ste12 may be due to a disordered vesicle transport system.

Nonlocal male mountain white-crowned sparrows have lower paternity and higher parasite loads than males singing local dialect

Bird song often varies geographically, and when this geographic variation has distinct boundaries, the shared song types are referred to as song dialects. We investigated the role of song dialect in male mating success in a wild breeding population of mountain white-crowned sparrows (Zonotrichia leucophrys oriantha). In 2 of 3 years, males singing unusual songs (“nonlocal” males) had lower total fertilization success (measured by microsatellite paternity analysis) than did males singing the local dialect (“local” males). Similarly, females produced disproportionately more young with local than with nonlocal males. However, dialect was not a significant predictor of male mating success when controlling for other factors that might affect paternity. Instead, the low mating success of nonlocal males was apparently due to an interaction between song dialect and parasite load. Nonlocal males were more severely infected by bloodborne Haemoproteus than were local males, although they did not differ in any other measured aspect of quality. Immigrant birds may be immunologically disadvantaged, possibly due to a lack of previous experience with the local parasite fauna, resulting in low mating success.

Modified pheromone communication associated with insecticidal resistance in the obliquebanded leafroller, Choristoneura rosaceana (Lepidoptera: Tortricidae)

This study reports on the impact of insecticidal resistance on the diel periodicity of the calling behaviour and pheromone production of different-aged virgin females of the obliquebanded leafroller (OBL), Choristoneura rosaceana. While both resistant (R) and susceptible (S) females initiated calling on the first night following emergence, the periodicity of the calling behaviour, as determined by the mean onset time of calling (MOTC) and the mean time spent calling (MTSC) over the first six nights of calling, differed between the two strains. R females started calling significantly later in the night. However, as the MOTC of R females advanced with age but did not do so in S individuals, the difference between strains was more pronounced in younger than older females. Furthermore, R females spent less time calling than S individuals. However, the MTSC increased as a function of age in both R and S females, so the difference between strains remained fairly constant for each night of calling. The major component of OBL sex pheromone, the Z11-14: Ac, determined at peak calling activity, significantly declined with female age. Overall, pheromone production was lower in R females than in S females, with the difference being more pronounced in younger than in older individuals. Thus, resistant females may have a lower mating success. The mating success of both R and S strain males did not vary with the number of previous matings acquired. With regard to males, although there was a significant decline in spermatophore size with successive matings, there was no significant difference between strains. However, R males are smaller and may be disadvantaged through female choice and/or may respond differently to pheromone source compared with S individuals. If the reproductive success of both sexes is affected, this may have a profound influence on the dynamics of insecticidal resistance in the presence or absence of selection in OBL populations.

Paternal effort and its relation to mating success in the European ground squirrel

The necessity for parental care is a driving force for determining mating systems and social organization. The European ground squirrel, Spermophilus citellus, is a polygynous, gregarious species in which male parental behaviour would not be expected. We had observed males digging in litter burrows that were later occupied by females and their offspring. Males never stayed overnight within these burrows. To determine whether this was some kind of paternal effort we tested the following hypotheses: (1) that male burrowing behaviour was directed towards the male's own offspring or towards the pregnant or lactating mother of the male's offspring; (2) that this behaviour had costs in terms of condition, decreased survival or fecundity; and (3) that it benefited offspring condition or survival. All three assumptions were met. Males worked on the litter burrow of their copulatory partners. Thus, this behaviour was directed towards the male's potential offspring. Male burrowing costs were seen in decreased foraging time and increased body mass loss. Offspring benefits were evident in increased mass at natal emergence. We conclude that male digging at litter burrows can be considered as paternal effort. Lastly, we considered the effects of polygyny on this male parental effort by comparing mating effort, mating success and paternal effort. High mating success was associated with high mating effort and low paternal effort. Moderate to low mating success was associated with lower mating effort and higher paternal effort, indicating a trade-off between the two.

Light wavelength dependency of mating activity in the Drosophila melanogaster species subgroup.

The action spectra of mating activity among the six species of the Drosophila melanogaster species subgroup were compared to understand how light wavelength affects mating activity. The species fell into three groups with respect to the action spectrum of mating activity. We chose one representative species from each of the three types for detailed study: D. melanogaster, D. sechellia and D. yakuba. The mating activities were investigated under three different light intensities of three monochromatic lights stimulus. Each species showed a unique spectral and intensity response. To know the evolutionary meaning of the light wavelength dependency of mating activity, we superimposed the type of action spectrum of mating activity in these six species on a cladogram. Mating inhibition under UV was conserved in evolution among these species. Furthermore we clarified that D. melanogaster showed low mating activity under UV because males courted less under UV.

Isolation and properties of genetically defined strains of the methylotrophic yeast Hansenula polymorpha CBS4732.

Genetically defined strains of the yeast Hansenula polymorpha were constructed from a clone of H. polymorpha CBS4732 with very low mating and sporulation abilities. Mating, spore viability, and the percentage of four-spore-containing asci were increased to a level at which tetrad analysis was possible. Auxotrophic mutations in 30 genes were isolated and used to construct strains with multiple markers for mapping studies, transformation with plasmid DNA, and mutant screening. Various other types of mutants were isolated and characterized, among them mutants that displayed an altered morphology, methanol-utilization deficient mutants and strains impaired in the biosynthesis of alcohol oxidase and catalase. Also, the mutability of H. polymorpha CBS4732 vs H. polymorpha NCYC495 was compared. The data revealed clear differences in frequencies of appearance and mutational spectra of some mutants isolated. Many of the mutants isolated had good mating abilities, and diploids resulting from their crossing displayed high sporulation frequencies and high spore viability. Most of the markers used revealed normal Mendelian segregation during meiosis. The frequency of tetratype spore formation was lower than in Saccharomyces cerevisiae suggesting a lower frequency of recombination during the second meiotic division. The properties of genetically defined strains of H. polymorpha CBS4732 as well as their advantages for genetics and molecular studies are discussed.

Genetic characterization of the nonconventional yeast Hansenula anomala

We describe genetic, molecular and taxonomic characteristics of the yeast Hansenula anomala. Pulsed-field gel electrophoresis of chromosomal DNAs from 19 H. anomala strains and related species indicated that H. anomala had a clearly different karyotype. Chromosome length polymorphism of the H. anomala strains was independent of their geographic origin and source of isolation. The strains were classified into four groups of similar karyotypes and one strain showed a unique profile. The sizes of chromosomes ranged from 850 to 3500 kb in different strains. The haploid chromosome number of H. anomala is at least nine. We have found RAPD primers discriminating at both the species and strain levels. All the primers tested except the M13 core sequence generated unique patterns with most strains. The results indicate the usefulness of PCR analysis with primer M13 for identification of the H. anomala species. Screening of the CBS (Utrecht) collection strains of H. anomala showed that they are rather difficult objects for genetic hybridization analysis. The strains have low fertility, viz. very poor sporulation, low mating type activities and, as a rule, nonviable ascospores. The majority of the hybrids obtained are polyploid, probably tetraploid, as judged by the segregation of control auxotrophic markers. Nevertheless, some monosporic cultures of the strains studied, including the biocontrol yeast J121, formed diploid hybrids with regular meiotic segregation of control auxotrophic markers. As a rule, H. anomala isolates are homothallic, showing delayed self-diploidization. Rare stable heterothallic strains of H. anomala also occur.

Endosulfan Exposure Disrupts Pheromonal Systems in the Red-Spotted Newt: A Mechanism for Subtle Effects of Environmental Chemicals

Because chemicals introduced into the environment by humans can affect both long-term survivorship and reproduction of amphibians, discovering the specific mechanisms through which these chemicals act may facilitate the development of plans for amphibian conservation. We investigated the amphibian pheromonal system as a potential target of common environmental chemicals. By treating female red-spotted newts, Notophthalmus viridescens, to a commonly used insecticide, endosulfan, we found that the pheromonal system is highly susceptible to low-concentration exposure. The impairment of the pheromonal system directly led to disrupted mate choice and lowered mating success. There were no other notable physiologic or behavioral changes demonstrated by the animals at the insecticide concentrations administered. Our findings suggest that the amphibian pheromonal system is one of the systems subject to subtle negative effects of environmental chemicals.