Effect of 20-hydroxyecdysone on cannibalism, sexual behavior, and contact sex pheromone in the solitary female spider, Tegenaria atrica

Fractions of Ageratum conyzoides L. (Compositae) induce mitochondrial-mediated apoptosis in rats: Possible option in monosodium glutamate-induced hepatic and uterine pathological disorder

ETHNOPHARMACOLOGICAL RELEVANCE

Several pathological disorders have been attributed to either oxidative stress or defect in apoptotic signaling pathway. Some bioactive compounds elicit their antiproliferative properties by induction of apoptosis via mitochondrial permeability transition (mPT) pore opening.

AIM OF STUDY

The present study therefore investigated the effects of various fractions of methanol extract of Ageratum conyzoides L. (MEAC) on mitochondrial-mediated apoptosis and the possible protective potential of the most potent against monosodium glutamate (MSG)-induced hepatic damage and uterine pathological disorder. The plant is folklorically used in the treatment of cancer and gynecological disorder.

MATERIALS AND METHODS

The MEAC was partitioned in succession and concentrated at 40 °C to obtain chloroform(CFAC), ethylacetate(EFAC) and methanol(MFAC) fractions. Mitochondria were isolated by differential centrifugation. The opening of mPT pore, mATPase activity and hepatic DNA fragmentation were assessed spectrophotometrically. Caspases 9 and 3, SOD and GSH-Px activities and MDA level were determined using ELISA technique. Histological assessment of the liver and uterine sections and GC-MS analysis of the most potent fraction were carried out.

RESULTS

The investigation showed that oral administration of the fractions caused induction of mPT pore opening, enhanced mATPase activity, upregulated the activities of caspases 9 and 3 and also, caused hepatic DNA fragmentation with CFAC being the most potent. The CFAC reversed severe MSG-induced hepatic damage and uterine hyperplasia. The MSG-induced oxidative stress was normalized by CFAC. The GC-MS analysis of CFAC revealed the presence of some pharmacologically relevant phytochemicals.

CONCLUSION

These findings therefore suggest that fractions of Ageratum conyzoides induce mitochondrial-mediated apoptosis. Moreover, CFAC, which is the most potent has a promising antioxidant and antiproliferative potential against MSG-induced hepatic and uterine pathological disorder.

The role of silk in courtship and communication in mygalomorph spiders: Do males regulate their courtship in response to female mating status?

In spiders, pheromones are known to be responsible for attracting the opposite sex, eliciting male searching and courtship behaviors, as well as for synchronizing potential mates in space and time. Most spiders are cannibalistic and aggressive. Thus, early recognition of a female as a possible mate is essential for males, who may suffer high energetic or reproductive costs to the extreme of losing all fitness opportunities. In Acanthogonatus centralis Goloboff 1995, a mygalomorph spider, what female signs might be triggering male courtship behavior remain unknown, as well as whether males can discriminate between females. The aims of the present work were (1) establishing whether males can detect the presence of females using airborne and silk-borne signals and (2) determining whether males can discriminate the reproductive status and body condition of females. We found no evidence that airborne pheromones play a role in the sexual communication of A. centralis, but silk-bound contact signals function as a female advertisement. Also, this is the first study that demonstrates that male mygalomorph spiders can discriminate between different signals on silk through direct contact, showing a preference for unmated females.

Particular Levels of Odors Released by Virgin Females Attract Conspecific Males of the Funnel-Web Spider Allagelena difficilis

Female-released chemical signals are crucial clues for mate-searching males to locate and gain sexual receptivity of conspecific females. Abundant behavioral evidence indicates that female spiders release sex pheromones to guide mate-searching behavior of conspecific mature males. However, the chemical nature of spider pheromones is poorly understood. Females of the funnel-web spider, Allagelena difficilis, employ sit-and-wait tactics for mating. Field observations indicate that males leave their retreats to search for potential mates during the breeding season. Therefore, we investigated whether virgin females release a sex attractant to conspecific males and then explored the chemical nature of the female pheromone. Four fatty acids extracted from the female bodies (palmitic acid, linoleic acid, cis-vaccenic acid and stearic acid) constitute a multiple-component sex attractant to conspecific males in A. difficilis. Unexpectedly, mated females also produce the same fatty acids, but at trace levels. Two-choice experiments showed that males were significantly attracted by the blend of the four fatty acids in appropriate concentrations while avoiding the blend consisting of the same acids at very low concentrations, suggesting that mate-searching males are able to discriminate virgin females from mated females by the quantities of female-specific fatty acids in the funnel-web spider A. difficilis.

Intraindividual Behavioral Variability Predicts Foraging Outcome in a Beach-dwelling Jumping Spider

Animal personality, defined as consistent differences between individuals in behavior, has been the subject of hundreds if not thousands of papers. However, little work explores the fitness consequences of variation in behavior within individuals, or intraindividual variability (IIV). We probe the effects of behavioral IIV on predator-prey interaction outcomes in beach-dwelling jumping spiders (Terralonus californicus). Prior studies have found that spiders with higher body condition (body mass relative to size) behave more variably. Thus, we hypothesized that jumping spider activity level IIV would relate positively to foraging performance. To address this, we tested for associations between activity IIV, average activity level, and two measures of foraging success in laboratory mesocosms: change in spider mass and the number of prey killed. Activity IIV positively correlated with the mass that spiders gained from prey, but not with the number of prey killed. This suggests that spiders with high IIV consumed a greater proportion of their prey or used less energy. Interestingly, average activity level (personality) predicted neither metric of foraging success, indicating that behavioral IIV can predict metrics of success that personality does not. Therefore, our findings suggest that IIV should be considered alongside personality in studies of predator-prey interactions.

Pheromones of three ambrosia beetles in the Euwallacea fornicatus species complex: ratios and preferences

Three cryptic species in the Euwallacea fornicatus species complex were reared in laboratory colonies and investigated for the presence of pheromones. Collections of volatiles from combinations of diet, fungus, beetles, and galleries from polyphagous shot hole borer (Euwallacea sp. #1) revealed the presence of 2-heneicosanone and 2-tricosanone only in the presence of beetles, regardless of sex. Subsequent examination of volatiles from the other two species, tea shot hole borer (Euwallacea sp. #2) and Kuroshio shot hole borer (Euwallacea sp. #5), revealed these two ketones were present in all three species but in different ratios. In dual choice olfactometer behavioral bioassays, mature mated females were strongly attracted to a synthetic binary blend of ketones matching their own natural ratios. However, females in each species were repelled by ketone blends in ratios corresponding to the other two species. Males of each species responded similarly to females when presented with ratios matching their own or the other two species. The presence of these compounds in the three beetle species, in ratios unique to each species, and their strong species-specific attraction and repellency, suggests they are pheromones. The ecological function of these pheromones is discussed. In addition to the pheromones, the previously known attractant (1S,4R)-p-menth-2-en-1-ol (also known as quercivorol) was discovered in the presence of the fungal symbionts, but not in association with the beetles. Quercivorol was tested in a dual-choice olfactometer and was strongly attractive to all three species. This evidence suggests quercivorol functions as a kairomone for members of the E. fornicatus species complex, likely produced by the symbiotic fungi.

Identification and expression of nuclear receptor genes and ecdysteroid titers during nymphal development in the spider Agelena silvatica

Ecdysteroids play an essential role in the regulation of the molting processes of arthropods. Nuclear receptors of the spider Agelena silvatica that showed high homology with other arthropods especially in the functional domains were identified, two isoforms of ecdysone receptor (AsEcRA, AsEcRB), retinoid X receptor (AsRXR) and two isoforms of E75 (AsE75A, AsE75D). AsEcR and AsRXR mRNA did not show major changes in expression but occurred throughout the third instar nymphal stage. AsE75DBD was low or non-existent at first then showed a sudden increase from D7 to D10. On the other hand, AsE75D was expressed in the first half and decreased from D6 to D10. Ecdysteroid titers showed a peak on D6 in A. silvatica third instar nymphs. LC-MS/MS analysis of the ecdysteroid peak revealed only 20-hydroxyecdysone (20E) was present. The 20E peak on D6 and increase in AsE75DBD from D7 is likely a result of ecdysteroids binding to the heterodimer formed with constant expression of the AsEcR and AsRXR receptors. These findings indicate the mechanisms regulating molting widely conserved in insects and other arthropods also similarly function in spiders.

Male adaptations to minimize sexual cannibalism during reproduction in the funnel-web spider Hololena curta

Males of many spider species risk being attacked and cannibalized while searching for, courting, and mating with conspecific females. However, there are exceptions. We show that the funnel-web spider, Hololena curta, has 3 adaptations that minimize risk to males during courtship and mating, and enhance reproductive success. First, males detected chemical or tactile signals associated with webs of virgin females, and differentiated them from webs of mated females, enabling males to increase encounter rates with virgin females and avoid aggressive mated females. Second, males produced stereotyped vibrational signals during courting which induced female quiescence and suppressed female aggression. Third, when touched by males, sexually receptive females entered a cataleptic state, allowing males to safely approach and copulate. Because males can mate multiple times and the sex ratio in natural populations of H. curta is female biased, overall reproductive output is likely increased by males of this species avoiding sexual cannibalism.

N-3-Methylbutanoyl-O-methylpropanoyl-L-serine Methyl Ester - Pheromone Component of Western Black Widow Females

Chemical communication is common in spiders but few pheromones have been identified. Female widow spiders in the genus Latrodectus spin webs that disseminate an attractive sex pheromone, and a contact pheromone on the silk elicits courtship behavior by males. The methyl ester of N-3-methylbutanoyl-O-(S)-2-methylbutanoyl-L-serine is a contact pheromone of the Australian redback spider Latrodectus hasselti. We hypothesized that the contact pheromone of congeneric L. hesperus resembles that of L. hasselti. The silk of virgin L. hesperus females was extracted with methanol, and analyses by gas chromatography-mass spectrometry (GC/MS) provided evidence for the presence of N-3-methylbutanoyl-O-methylpropanoyl-L-serine methyl ester (MB-MP-S), a lower homologue of the L. hasselti contact pheromone. Behavioral responses of L. hesperus males to test stimuli were assayed on T-shaped rods with the end sections of the horizontal arm enveloped in filter paper. Males spent 40 % longer in contact with paper bearing female silk than with blank paper, and 39 % longer in contact with paper treated with silk extract than with solvent controls. Contact with silk and silk extract induced courtship behavior by 96 % and 80 % of males, respectively, indicating that there was a methanol-soluble courtship-eliciting contact pheromone on the silk. Males responded less strongly to synthetic MB-MP-S than to silk or silk extract. Paper impregnated with synthetic MB-MP-S (10 or 100 μg) induced courtship behavior in 3-16 % of males, and prompted males to stay 10-16 % longer than on control paper. Our data support the conclusion that MB-MP-S is part of a multi-component contact pheromone of L. hesperus.

Influence of social interactions on the response to social cues in spiderlings

Mutual attraction is one central mechanism involved in the maintenance of cohesion in group-living species and relies on a modulation of individual behaviours in response to the presence of conspecifics. Social markers left in the environment can play an additional role in the modulation of behaviours and can substantially impact the cohesion of social groups. In this study, our objective was to examine the interplay between the presence of social cues and the individual responsiveness to conspecifics in spiderlings. Spiders are relevant models to address this issue as juveniles lay silk draglines during their displacements and display a transient gregarious phase. We introduced single or pairs of spiderlings in an experimental arena covered with different amounts of silk. Our results indicated that the probability of moving increased with the presence and the quantity of silk in single individuals. In contrast, we did not find evidence for any influence of the quantity of silk on interacting spiderlings and we showed that social interactions inhibited the individual response to social markers. Overall, our study suggests that the influence of social interactions on the modulation of individual behaviours prevailed over the presence of social cues. We discussed our results in the framework of chemical communication to explain the interplay between social cues and social interactions on the modulation of individual behaviours.

Spider pheromones - a structural perspective

Spiders use pheromones for sexual communication, as do other animals such as insects. Nevertheless, knowledge about their chemical structure, function, and biosynthesis is only now being unraveled. Many studies have shown the existence of spider pheromones, but the responsible compounds have been elucidated in only a few cases. This review focuses on a structural approach because we need to know the involved chemistry if we are to understand fully the function of a pheromonal communication system. Pheromones from members of the spider families Pholcidae, Araneidae, Linyphiidae, Agenelidae, and Ctenidae are currently being identified and will be discussed in this review. Some of these compounds belong to compound classes not known from other arthropod pheromones, such as citric acid derivatives or acylated amino acids, whereas others originate from more common fatty acid metabolism. Their putative biosynthesis, their function, and the identification methods used will be discussed. Furthermore, other semiochemicals and the chemistry of apolar surface lipids that potentially might be used by spiders for communication are described briefly.

Juvenile development, ecdysteroids and hemolymph level of metabolites in the spider Brachypelma albopilosum (Theraphosidae)

In the present work, juvenile development and physiological state of mygalomorph Brachypelma albopilosum were investigated by means of individual rearing under controlled conditions. Males required 4-5 years for development from first juvenile instar to adulthood, passing through 8 to 12 juvenile molts. Females developed to adults in 5-6 years with a variable juvenile molt number from 9 to 13. The development and growth of males and females took place in a similar way until the last juvenile molt leading to subadults. Ecdysteroids, total lipid, cholesterol, and protein concentrations increased along with the different development instars in both males and females. After the last juvenile molt, spiders presented morphological and biochemical sex differences. Subadult and adulthood males were smaller in size and weight than females; hemolymph levels of ecdysteroids, total lipids, cholesterol, and glucose were higher in males. These physiological and biochemical differences can be correlated to the different sexual development between males and females.

Small molecules from spiders used as chemical probes

Spiders are important species in ecological systems and as major predators of insects they are endowed with a plethora of low-molecular-weight natural products having intriguing biological activities. The isolation and biological characterization of these entities are well established, however, only very recently have these compounds been used as templates for the design, synthesis, and biological evaluation of synthetic analogues. In contrast, the investigation of compounds responsible for chemical communication between spiders is far less developed, but recently new light has been shed onto the area of pheromones and allomones from spiders. Herein, we recapitulate these recent results, put them into perspective with previous findings, and provide an outlook for future studies of these chemotypes.

Agonistic interactions, cuticular and hemolymphatic lipid variations during the foraging period in spider females Brachypelma albopilosa (Theraphosidae)

Agonistic behaviour and lipid state were examined in tarantula Brachypelma albopilosa females during the foraging period. Modulation of the agonistic behaviour of females was not connected to their body size. Results show that the agonistic pattern of females differed significantly from the predation pattern at the behavioural and lipid levels. Aggressive-foraging females had low predation behaviour. Quantitative lipid changes were observed in relation to agonistic behaviour and predation. The total lipid index was studied by colorimetric methods, and lipid compounds were analyzed by gas chromatography-mass spectrometry in cuticle and hemolymph of females. The lipid components were free fatty acids, methyl esters, cholesterol, and long-chain aliphatic hydrocarbons. Methyl esters were much more abundant in cuticular lipids; unsaturated free fatty acids (linoleic and oleic acids) and methyl esters (methyl linoleate and methyl stearate) predominated in the hemolymph. Spider aggression was positively correlated with lipid concentration (cholesterol, fatty acids, methyl esters and hydrocarbons) in the hemolymph and the levels of cuticular fatty acids. Lipid levels are hypothesized to have evolved as a regulatory factor of predation and agonistic behaviours in tarantula females.

Male-specific (Z)-9-tricosene stimulates female mating behaviour in the spider Pholcus beijingensis

Chemical signals play an important role in spider sexual communication, yet the chemistry of spider sex pheromones remains poorly understood. Chemical identification of male-produced pheromone-mediating sexual behaviour in spiders has also, to our knowledge, not been reported before. This study aimed to examine whether chemically mediated strategies are used by males of the spider Pholcus beijingensis for increasing the probability of copulation. Based on data from gas chromatography-mass spectrometry analysis, electroantennography assay and a series of behavioural tests, we verified that (Z)-9-tricosene is a male-specific compound in the spider P. beijingensis. This compound acts as an aphrodisiac: it increases the likelihood that a female will mate. Mate-searching males release (Z)-9-tricosene to stimulate sexual behaviour of conspecific females. In the two-choice assay, however, sexually receptive females show no preference to the chambers containing (Z)-9-tricosene. This indicates that the male pheromone of P. beijingensis is not an attractant per se to the conspecific females. This is, to our knowledge, the first identification of a male-produced aphrodisiac pheromone in spiders.

Spider sex pheromones: emission, reception, structures, and functions

Spiders and their mating systems are useful study subjects with which to investigate questions of widespread interest about sexual selection, pre- and post-copulatory mate choice, sperm competition, mating strategies, and sexual conflict. Conclusions drawn from such studies are broadly applicable to a range of taxa, but rely on accurate understanding of spider sexual interactions. Extensive behavioural experimentation demonstrates the presence of sex pheromones in many spider species, and recent major advances in the identification of spider sex pheromones merit review. Synthesised here are the emission, transmission, structures, and functions of spider sex pheromones, with emphasis on the crucial and dynamic role of sex pheromones in female and male mating strategies generally. Techniques for behavioural, chemical and electrophysiological study are summarised, and I aim to provide guidelines for incorporating sex pheromones into future studies of spider mating. In the spiders, pheromones are generally emitted by females and received by males, but this pattern is not universal. Female spiders emit cuticular and/or silk-based sex pheromones, which can be airborne or received via contact with chemoreceptors on male pedipalps. Airborne pheromones primarily attract males or elicit male searching behaviour. Contact pheromones stimulate male courtship behaviour and provide specific information about the emitter's identity. Male spiders are generally choosy and are often most attracted to adult virgin females and juvenile females prior to their final moult. This suggests the first male to mate with a female has significant advantages, perhaps due to sperm priority patterns, or mated female disinterest. Both sexes may attempt to control female pheromone emission, and thus dictate the frequency and timing of female mating, reflecting the potentially different costs of female signalling and/or polyandry to both sexes. Spider sex pheromones are likely to be lipids or lipid soluble, may be closely related to primary metabolites, and are not necessarily species specific, although they can still assist with species recognition. Newer electrophysiological techniques coupled with chemical analyses assist with the identification of sex pheromone compounds. This provides opportunities for more targeted behavioural experimentation, perhaps with synthetic pheromones, and for theorising about the biosynthesis and evolution of chemical signals generally. Given the intriguing biology of spiders, and the critical role of chemical signals for spiders and many other animal taxa, a deeper understanding of spider sex pheromones should prove productive.