Sterile males and females can synergistically suppress wild pests targeted by sterile insect technique.

The sterile insect technique (SIT) involves periodically releasing artificially sterilized insects to inhibit normal mating between wild insect pests, ultimately resulting in the eradication of wild pest populations. It has often been discussed whether releasing either one sex, mainly males, of sterile insects (i.e., a unisexual release) can enhance the pest-control effect of the SIT more than releasing both sexes (i.e., a bisexual release). We constructed a mathematical model to examine the contribution of sterile males and females to the pest-control effect and the synergy between them. We consider that males seek out and court females in accord with their own female searching ability and preference, and that females subsequently choose one male from among males courting them in accordance with their own preference. Using this model, we compared the pest-control effect of bisexual and unisexual release, focusing on the difference in mating systems of the targeted insects. We showed that for swarm-type mating systems (with few courtship chances with higher encounter rates), bisexual release was the most effective, irrespective of the relative female searching ability between wild and sterile males. In this case, sterile females indirectly reduce wild females mating with either male by absorbing courtship from both wild and sterile males. By contrast, bisexual release is the most effective for scramble-type mating systems (more courtship chances with lower encounter rates) only when the female searching ability of sterile males is lower than that of wild males. In this case, sterile females absorb courtship from males with higher searching abilities. Therefore, the net impact of sterile females depends on the difference in sexual performance between wild and sterile males. Because the sexual performance of sterile insects is often degraded during the process of sterilization, we suggest that bisexual release can be a compatible measure to efficiently suppress wild pest populations.

The female Euscepes postfasciatus refractory period is induced by the male but length is determined by the female.

Females of many animals mate multiple times during their lives (i.e., polyandry). The period between matings (mating interval) is called the refractory period (RP). In the West Indian sweet potato weevil (Euscepes postfasciatus), males use the ejaculate to induce the RP in females to prevent re-mating. By measuring the RP, a large variation of 1-49 days was observed. This variation may be due to the males (ejaculate quantity and quality) and females (ejaculate sensitivity/degradation ability and body size) and their interactions, but the exact mechanisms are currently unclear. Here, we investigated a tendency towards a particular female RP duration and the associated traits of males and females to test the following three factors responsible for variation in the length of the RP: male manipulation of ejaculate volume, individual differences in male ejaculation substances, and ejaculate sensitivity/degradation ability in females. We prepared virgin males and females to create mating pairs. The following day, another mate was introduced to the females, and the first RP was measured. The same procedure was used for measuring the second RP. The males were also provided with another female (second female), mated, and then the RP of the second female was measured. In addition, the relationship between the length of the RP and female fitness was investigated. The results showed that there was a significant positive correlation between the first and second RP in the focal females, while no significant correlation was observed between the RP of the first and second females induced by the same male. It was also found that the length of the RP did not affect female fitness. This indicated that the males did not adaptively manipulate ejaculation volume depending on the quality of the females, and variance in the length of the RP may be explained by variation in the female physiological ability against ejaculate.

Effects of Larval Diet on the Male Reproductive Traits in the West Indian Sweet Potato Weevils Euscepes postfasciatus (Coleoptera: Curculionidae).

Larval diet significantly affects adult traits, although less is known about how they affect reproductive traits. Males of West Indian sweet potato weevil Euscepes postfasciatus deliver a remating inhibitor along with sperm to their mates during mating, leading to a refractory period (the period before females mate again). Crossing experiments were conducted using lines reared on artificial diets, including sweet potato powder (AD) or sweet potato tubers (SP) during the larval stage, and the refractory period was examined. We also examined whether the larval diet qualitatively or quantitatively altered male ejaculate. The results showed that the refractory period was significantly longer in the SP treatment than in the AD treatment for males and females. There was no significant difference in ejaculate volume. However, the number of sperm in the testes-seminal vesicles complex was significantly higher in the SP treatment. Additionally, SDS-PAGE revealed that the ejaculate was qualitatively different depending on the larval diet, and one protein of approximately 15 kDa in size was expressed only in the SP treatments. Revealing how larval diet affects reproductive traits in adult males will help shed light on the diverse evolution of insect mating systems and reproductive behavior.

First case of successful eradication of the sweet potato weevil, Cylas formicarius (Fabricius), using the sterile insect technique.

This paper presents the first case of the successful eradication of a Coleoptera pest species over a wide area using a combination of male annihilation technique (MAT) and sterile insect technique (SIT) application. The sweet potato weevil, Cylas formicarius, is one of the most destructive and widely distributed pests of sweet potato, Ipomoea batatas. A project to eradicate it was launched in 1994 on Kume Island, Okinawa Prefecture, Japan. The MAT application was first used from November 1994 to January 1999 to reduce the density of wild populations. The distribution and densities of weevils were assessed by trapping them and surveying infestation rates in wild hosts and sweet potatoes in the field. The C. formicarius populations were suppressed by approximately 90% and plant infestations were reduced from 9.5% to less than 0.1% by using the MAT. Then, hundreds of thousands to millions of sterile weevils were released each week (ca. 460 million in total from 1999 to 2012). As a result, based on an analysis of 12748 stems and 48749 tubers, no weevil infections were detected in the stems or tubers of sweet potato since 1997. Since 2009, almost no wild weevils were captured in traps, and in wild host and sweet potato surveys no weevils have been found in any of the 580 locations and 8833 samples since October 2011. As of 28 December, 2012, C. formicarius is considered to have been eradicated from Kume Island. This paper describes the process of eradicating C. formicarius using SIT application integrated with MAT application for the first time and discusses some of the main challenges associated with the weevil eradication campaignl.

Anti-hyperglycaemic effects of the Japanese red maple Acer pycnanthum and its constituents the ginnalins B and C.

The anti-hyperglycaemic effects of the leaves of Acer pycnanthum K. Koch, and the purification and identification of the active compounds were investigated. Extracts of the leaves showed a potent inhibitory effect on the α-glucosidase in both in vivo and in vitro experiments. The fractionation of the crude extract gave two active compounds, ginnalin B (6-O-galloyl-1,5-anhydro-D-glucitol) and ginnalin C (2-O-galloyl-1,5-anhydro-D-glucitol), by spectroscopic analysis. This is the first report that A. pycnanthum and its constituents may be useful for the prevention or treatment of diabetes mellitus.

Pycnalin, a new α-glucosidase inhibitor from Acer pycnanthum.

A new compound, pycnalin (1), together with four known compounds, ginnalins A (2), B (3), C (4), and 3,6-di-O-galloyl-1,5-anhydro-D-glucitol (3,6-di-GAG) (5), were isolated from Acer pycnanthum. The structure of 1 was determined on the basis of 2D-NMR spectral data and synthesis of 1. Pycnalin (1) is the first 1,5-anhydro-D-mannitol linked to a gallic acid, while compounds 2-5 were 1,5-anhydro-D-glucitol linked to gallic acids. All compounds were tested in vitro for α-glucosidase inhibitory and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities. Pycnalin (1) exhibited moderate α-glucosidase inhibitory activity as well as free radical scavenging activity. Ginnalin A (2) and 3,6-di-GAG (5), which have two galloyl groups, exhibited potent α-glucosidase inhibition, compared to those of other compounds 1, 3, and 4 containing a galloyl group. These results suggest that α-glucosidase inhibition is influenced by the number of galloyl groups.

Identification of Maple Anthocyanin and its Antiproliferative Activity against LLC, T47D and C3H10T1/2 Cells.

BACKGROUND: The genus Acer contains around 200 species, with more than 400 garden varieties. There is considerable diversity in these species and garden varieties, and each can be characterized by morphology and chemical composition. The red appearance of Acer leaves is due to anthocyanin compounds, including cyanidin glycosides, delphinidin glycosides, and galloylated anthocyanins. Few studies have investigated the diversity of anthocyanin compounds in garden varieties, and no studies have examined the pharmacological effects of these compounds. OBJECTIVE: The purpose of this study was to identify the anthocyanins of Acer palmatum cv. 'Chishio', a garden variety of A. palmatum and evaluate their antiproliferative and antioxidant activities. METHODS: A methanol extract of fresh leaves was partitioned with ethyl acetate. The extract was purified by column chromatography and compounds were subsequently identified by 1H and 13C NMR and ESI-HRMS. Antiproliferative activity was evaluated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4- sulfophenyl)-2H-tetrazolium, inner salt (MTS) colorimetric assay. The antioxidant assay was evaluated by scavenging activity using the stable radical DPPH. RESULTS: The anthocyanins cyanidin-3-O-(6''-O-α-rhamnopyranosyl- ß-glucopyranoside), cyanidin-3-O- ß- glucopyranoside, cyanidin-3-O-[2''-O-(galloyl)-6''-O-(rhamnosyl)-ß-glucoside], and cyanidin-3-O-[2''-O-(galloyl)- ß-glucopyranoside] were isolated from A. palmatum cv. 'Chishio'. All four anthocyanin compounds showed antiproliferative activity against LLC and T47D cells, and galloylated anthocyanin showed antiproliferative activity against C3H10T1/2 cells. All four anthocyanins inhibited the activity of DPPH radicals in a dosedependent manner. CONCLUSION: Maple anthocyanins could be a new cancer therapeutic agent or prophylactic medicine.

Effects of Storage Periods of an Artificial Larval Diet on the Yield and Quality of Mass-Reared West Indian Sweet Potato Weevil (Coleoptera: Curculionidae).

Artificial diets have been employed for the mass-rearing of numerous insects because of their ease of use and standardized quality. An ability to store artificial diets under nonrefrigerated conditions over the long term could improve the efficacy of mass-rearing systems considerably. However, it remains largely unknown how long artificial diets can be stored at such temperatures without any adverse effects on the insects reared. In this study, we investigated yield, body size, and reproductive potential of West Indian sweet potato weevil, Euscepes postfasciatus (Fairmaire), which is a major sweet potato pest, under management using the sterile-insect technique in Japan and reared using artificial diets with different storage periods (14, 28, and 42 d) at nonrefrigerated temperatures (25 ± 1°C), and compared them with those of the control (0 d). Notably, E. postfasciatus yield and reproductive potential increased significantly with an increase in storage period (28 and 42 d). Conversely, male body size decreased significantly following feeding with artificial diet stored for 42 d, when compared with the control, while there were no significant differences in female body size between the control and all the treatments. We discuss the potential causes of such varying effects between yield and body size and conclude that E. postfasciatus artificial diet can be stored for at least 28 d without any adverse effects on weevil yield and weevil quality. To the best of our knowledge, this is the first report revealing the positive effects of long-term storage of the artificial diet on mass-reared insects.

Killing two bugs with one stone: a perspective for targeting multiple pest species by incorporating reproductive interference into sterile insect technique.

The sterile insect technique is an environmentally friendly method to control and even eradicate agricultural and veterinary insect pests without using chemical pesticides in excess. However, the continuous production and release of sterile insects is economically costly and eradication programs using sterile insects have not always been successful owing to the incomplete mating ability of the sterile insects. Here we focus on the theory and empirical findings of interspecific negative mating interaction, known as reproductive interference, to develop a more cost-effective and value-added pest management program. We suggest that sterile insects can be used for simultaneous control of both wild-type conspecifics and closely related pest species by taking advantage of the fact that, when species recognition abilities are incomplete, courtship and mating are often misdirected toward heterospecies. This new approach might help mitigate economic damage and human health crises caused by pest insects. © 2018 Society of Chemical Industry.

A New System for Detecting Initial Colonization by Invasive Pests and Their Locations.

Quarantine pests in plants can be a serious agricultural problem; many eradication programs using area-wide control measures have been implemented worldwide to combat this threat. Surveillance measures using sex pheromone (in general, male-attractant) traps are also widely implemented for rapid control and eradication of invasive pests. If initial pest colonization can be determined based on temporal count data of trapped insects (i.e., males), and countermeasures are applied only during colonization, costs incurred by these countermeasures would be dramatically reduced, especially in areas with frequent invasions. In this study, we developed a system to detect initial pest colonization, and to narrow down colonized regions using estimated temporal count data of the sweet potato weevil, Cylas formicarius Fabricius (Coleoptera: Curculionidae), in Tsuken Island, Okinawa, Japan. We verified the system by comparing our estimates to actual colonization data obtained via regular host plant surveys. Results indicated that our system was able to successfully detect pest colonization and estimate colonized regions. In this study, we discuss the conditions (i.e., pest biology, environment, etc.) that are optimal for application of our system.

Experimental evidence suggests that specular reflectance and glossy appearance help amplify warning signals.

Specular reflection appears as a bright spot or highlight on any smooth glossy convex surface and is caused by a near mirror-like reflectance off the surface. Convex shapes always provide the ideal geometry for highlights, areas of very strong reflectance, regardless of the orientation of the surface or position of the receiver. Despite highlights and glossy appearance being common in chemically defended insects, their potential signalling function is unknown. We tested the role of highlights in warning colouration of a chemically defended, alpine leaf beetle, Oreina cacaliae. We reduced the beetles' glossiness, hence their highlights, by applying a clear matt finish varnish on their elytra. We used blue tits as predators to examine whether the manipulation affected their initial latency to attack, avoidance learning and generalization of warning colouration. The birds learned to avoid both dull and glossy beetles but they initially avoided glossy prey more than dull prey. Interestingly, avoidance learning was generalized asymmetrically: birds that initially learned to avoid dull beetles avoided glossy beetles equally strongly, but not vice versa. We conclude that specular reflectance and glossiness can amplify the warning signal of O. cacaliae, augmenting avoidance learning, even if it is not critical for it.

Adaptive significance of death feigning posture as a specialized inducible defence against gape-limited predators.

Death feigning is fairly common in a number of taxa, but the adaptive significance of this behaviour is still unclear and has seldom been tested. To date, all proposed hypotheses have assumed that prey manage to escape predation by sending a death-mimicking signal, although death-feigning postures are markedly different from those of dead animals. Moreover, the efficacy of this technique may largely depend on the foraging mode of the predator; death feigning seldom works with sit-and-wait predators that make the decision to attack and consume prey within a very brief time. We examined whether death feigning in the pygmy grasshopper Criotettix japonicus Haan was an inducible defence behaviour against the frog Rana nigromaculata, a sit-and-wait, gape-limited predator. The characteristic posture assumed by the grasshopper during death feigning enlarges its functional body size by stretching each of three body parts (pronotum, hind legs and lateral spines) in three different directions, thereby making it difficult for the predator to swallow the prey. Our result is the first consistent explanation for why death-mimicking animals do not always mimic the posture of dead animals.

Warning coloration can be disruptive: aposematic marginal wing patterning in the wood tiger moth.

Warning (aposematic) and cryptic colorations appear to be mutually incompatible because the primary function of the former is to increase detectability, whereas the function of the latter is to decrease it. Disruptive coloration is a type of crypsis in which the color pattern breaks up the outline of the prey, thus hindering its detection. This delusion can work even when the prey's pattern elements are highly contrasting; thus, it is possible for an animal's coloration to combine both warning and disruptive functions. The coloration of the wood tiger moth (Parasemia plantaginis) is such that the moth is conspicuous when it rests on vegetation, but when it feigns death and drops to the grass- and litter-covered ground, it is hard to detect. This death-feigning behavior therefore immediately switches the function of its coloration from signaling to camouflage. We experimentally tested whether the forewing patterning of wood tiger moths could function as disruptive coloration against certain backgrounds. Using actual forewing patterns of wood tiger moths, we crafted artificial paper moths and placed them on a background image resembling a natural litter and grass background. We manipulated the disruptiveness of the wing pattern so that all (marginal pattern) or none (nonmarginal pattern) of the markings extended to the edge of the wing. Paper moths, each with a hidden palatable food item, were offered to great tits (Parus major) in a large aviary where the birds could search for and attack the "moths" according to their detectability. The results showed that prey items with the disruptive marginal pattern were attacked less often than prey without it. However, the disruptive function was apparent only when the prey was brighter than the background. These results suggest that warning coloration and disruptive coloration can work in concert and that the moth, by feigning death, can switch the function of its coloration from warning to disruptive.

Anti-inflammatory effects of seeds of the tropical fruit camu-camu (Myrciaria dubia).

The methanolic extract of seeds of the tropical fruit camu-camu was screened for its anti-inflammatory activity in carrageenan-induced paw edema model mice. The extract significantly suppressed both the formation of edema in mice by oral administration and the release of nitric oxide from macrophage-derived RAW 264.7 cells in vitro. Based on the results of a spectroscopic analysis, the active compound was identified by in vivo bioassay-guided fractionation to be 3ß-hydroxy-lup-20(29)-en-28-oic acid, betulinic acid, known as an anti-inflammatory triterpenoid. These findings suggest that camu-camu seed extract is a potentially useful material as a source of betulinic acid and as a functional food for prevention of immune-related diseases.

Camouflage effects of various colour-marking morphs against different microhabitat backgrounds in a polymorphic pygmy grasshopper Tetrix japonica.

BACKGROUND: Colour-marking polymorphism is widely distributed among cryptic species. To account for the adaptive significance of such polymorphisms, several hypotheses have been proposed to date. Although these hypotheses argue over the degree of camouflage effects of marking morphs (and the interactions between morphs and their microhabitat backgrounds), as far as we know, most empirical evidence has been provided under unnatural conditions (i.e., using artificial prey). METHODOLOGY/PRINCIPAL FINDINGS: Tetrix japonica, a pygmy grasshopper, is highly polymorphic in colour-markings and occurs in both sand and grass microhabitats. Even within a microhabitat, T. japonica is highly polymorphic. Using humans as dummy predators and printed photographs in which various morphs of grasshoppers were placed against different backgrounds, we addressed three questions to test the neutral, background heterogeneity, and differential crypsis hypotheses in four marking-type morphs: 1) do the morphs differ in the degree of crypsis in each microhabitat, 2) are different morphs most cryptic in specific backgrounds of the microhabitats, and 3) does the morph frequency reflect the degree of crypsis? CONCLUSIONS/SIGNIFICANCE: The degree of camouflage differed among the four morphs; therefore, the neutral hypothesis was rejected. Furthermore, the order of camouflage advantage among morphs differed depending on the two types of backgrounds (sand and grass), although the grass background consistently provided greater camouflage effects. Thus, based on our results, we could not reject the background heterogeneity hypothesis. Under field conditions, the more cryptic morphs comprised a minority of the population. Overall, our results demonstrate that the different morphs were not equivalent in the degree of crypsis, but the degree of camouflage of the morphs was not consistent with the morph frequency. These findings suggest that trade-offs exist between the camouflage benefit of body colouration and other fitness components, providing a better understanding of the adaptive significance of colour-markings and presumably supporting the differential crypsis hypothesis.

Optimal-foraging predator favors commensalistic Batesian mimicry.

BACKGROUND: Mimicry, in which one prey species (the Mimic) imitates the aposematic signals of another prey (the Model) to deceive their predators, has attracted the general interest of evolutionary biologists. Predator psychology, especially how the predator learns and forgets, has recently been recognized as an important factor in a predator-prey system. This idea is supported by both theoretical and experimental evidence, but is also the source of a good deal of controversy because of its novel prediction that in a Model/Mimic relationship even a moderately unpalatable Mimic increases the risk of the Model (quasi-Batesian mimicry). METHODOLOGY/PRINCIPAL FINDINGS: We developed a psychology-based Monte Carlo model simulation of mimicry that incorporates a "Pavlovian" predator that practices an optimal foraging strategy, and examined how various ecological and psychological factors affect the relationships between a Model prey species and its Mimic. The behavior of the predator in our model is consistent with that reported by experimental studies, but our simulation's predictions differed markedly from those of previous models of mimicry because a more abundant Mimic did not increase the predation risk of the Model when alternative prey were abundant. Moreover, a quasi-Batesian relationship emerges only when no or very few alternative prey items were available. Therefore, the availability of alternative prey rather than the precise method of predator learning critically determines the relationship between Model and Mimic. Moreover, the predation risk to the Model and Mimic is determined by the absolute density of the Model rather than by its density relative to that of the Mimic. CONCLUSIONS/SIGNIFICANCE: Although these predictions are counterintuitive, they can explain various kinds of data that have been offered in support of competitive theories. Our model results suggest that to understand mimicry in nature it is important to consider the likely presence of alternative prey and the possibility that predation pressure is not constant.