Conspecific Eggs Research Articles

Influence of victims' diet on the life‐history traits in cannibalistic Menochilus sexmaculatus

AbstractMultitrophic interactions are common in nature and play a major role in modulating life‐history traits in predatory insects. The sequestration of chemicals and the transfer of nutrients from one trophic level to a higher trophic level have been reported previously. However, the effect of cannibalism, which is prevalent in the food chain, has not been explored yet. In this study, we hypothesised that the varying nutritional condition of the victim would significantly influence the life‐history traits of adult Menochilus sexmaculatus Fabricius (Coleoptera: Coccinellidae). To test this hypothesis, we provided fourth‐instar individuals with first‐instar victims of varying nutritional quality for cannibalism. To create victims of varying nutritional quality, first‐instar victims were fed on high‐quality aphids [Aphis craccivora Koch (Hemiptera: Aphididae)], low‐quality aphids (Aphis nerii Boyer de Fonscolombe) and conspecific eggs. The cannibalistic groups were tested against the control group, in which the fourth instars were provided with their natural prey, A. craccivora. Our results revealed a significant difference in the consumption of prey by the fourth instars between the diet groups, with the control group consuming the most prey. The developmental duration of fourth instars was not significantly influenced by the victims' diet or the amount of victims cannibalised. Furthermore, neither the victims' diet nor the amount of victims cannibalised affected the mating (time to commence mating and copulation duration) and reproductive parameters (egg viability and fecundity) in M. sexmaculatus. Cannibalism here might have compensated for the low‐quality victims, resulting in insignificant effects on the life‐history traits of M. sexmaculatus. Otherwise, given the short duration of the first instars and their potentially limited ability to sequester significant amounts of plant allelochemicals, it is possible that their diet did not affect the development, mating and reproductive attributes of the cannibals. Thus, the use of higher instars as victims may yield substantially different outcomes.

Insect neurobiology: Oviposition crowd control

A new study examines how Helicoverpa armigera females detect chemicals released by conspecific eggs in order to avoid laying more eggs on the same substrate. This work opens new avenues for basic research inquiries and offers a potential strategy for controlling insect pests.

How conspecific and allospecific eggs and larvae drive oviposition preference in Drosophila.

Where to lay the eggs is a crucial decision for females as it influences the success of their offspring. Female flies prefer to lay eggs on food already occupied and consumed by larvae, which facilitates social feeding, but potentially could also lead to detrimental interactions between species. Whether females can modulate their attraction to cues associated with different species is unknown. Here, we analyzed the chemical profiles of eggs and larvae of 16 Drosophila species, and tested whether Drosophila flies would be attracted to larvae-treated food or food with eggs from 6 different Drosophila species. The chemical analyses revealed that larval profiles from different species are strongly overlapping, while egg profiles exhibit significant species specificity. Correspondingly, female flies preferred to lay eggs where they detected whatever species' larval cues, while we found a significant oviposition preference only for eggs of some species but not others. Our findings suggest that both larval and egg cues present at a given substrate can drive oviposition preference in female flies.

A female-specific odorant receptor mediates oviposition deterrence in the moth Helicoverpa armigera

Finding ideal oviposition sites is a task of vital importance for all female insects. To ensure optimal conditions for their progeny, females of herbivorous insects detect not only the odors of a relevant host plant but also chemicals released by eggs, named oviposition-deterring pheromones (ODPs). It is reported that such chemicals play critical roles in suppressing female oviposition behavior; however, the molecular mechanism underlying the detection of egg-derived ODPs remains elusive. Here, we have identified three specific fatty acid methyl esters from the surface of eggs of Helicoverpa armigera serving as ODPs-methyl oleate (C18:1ME), methyl palmitate (C16:0ME), and methyl stearate (C18:0ME). We demonstrated that these ODPs are detected by the receptor, HarmOR56, exclusively expressed in sensilla trichodea on female antennae. To assess the significance of this receptor, we disrupted HarmOR56 in H.armigera using CRISPR-Cas9 and found that mutant females did not respond to the ODPs, neither in behavioral nor in electrophysiological tests. We therefore conclude that HarmOR56 is indispensable for identifying the ODPs. This study explores, for the first time, how a female-specific odorant receptor detects chemicals from conspecific eggs. Our data elucidate the intriguing biological phenomenon of repulsion to conspecific eggs during oviposition and contribute new insight into a female-specific olfactory pathway linked to reproduction.

Egg cannibalism by larvae of the weed biological control agent, Neogalerucella calmariensis

ABSTRACT The host-specific beetle Neogalerucella calmariensis was introduced to North America to control Lythrum salicaria, and in some areas has persisted in high population densities despite decimation of target plants. We hypothesised that egg predation might contribute to the survival of the beetles. In small-scale laboratory experiments, we investigated the likelihood of egg cannibalism at different N. calmariensis life stages. Neither neonates nor adults cannibalised eggs, however late instar larvae readily preyed on eggs of conspecifics. Pupal weights of larvae that cannibalised eggs were larger than those fed only leaf material suggesting that egg cannibalism may be associated with a fitness benefit.

Repeatable randomness, invariant properties, and the design of biological signatures of identity.

What makes a perfect signature? Optimal signatures should be consistent within individuals and distinctive between individuals. In defense against avian brood parasitism, some host species have evolved "signatures" of identity on their eggs, comprising interindividual variation in color and pattern. Tawny-flanked prinia (Prinia subflava) egg signatures facilitate recognition and rejection of parasitic cuckoo finch (Anomalospiza imberbis) eggs. Here, we show that consistency and distinctiveness of patterns are negatively correlated in prinia eggs, perhaps because non-random, repeatable pattern generation mechanisms increase consistency but limit distinctiveness. We hypothesize that pattern properties which are repeatable within individuals but random between individuals ("invariant properties") allow hosts to circumvent this trade-off. To find invariant properties, we develop a method to quantify entire egg phenotypes from images taken from different perspectives. We find that marking scale (a fine-grained measure of size), but not marking orientation or position, is an invariant property in prinias. Hosts should therefore use differences in marking scale in egg recognition, but instead field experiments show that these differences do not predict rejection of conspecific eggs by prinias. Overall, we show that invariant properties allow consistency and distinctiveness to coexist, yet receiver behavior is not optimally tuned to make use of this information.

Dietary conditioning on aphids and conspecific eggs in the ladybirdMenochilus sexmaculatusFabricius influences cannibalistic food choices in subsequent generations

AbstractMenochilus sexmaculatus, a generalist aphidophagous ladybird beetle, is one of the potential biocontrol agents of multiple aphid species. This beetle exhibits cannibalism among different life stages. A laboratory experiment was conducted by conditioning the larvae and adults on their natural prey that is aphids, or the conspecific eggs for five generations to assess whether cannibalism was affected by prior cannibalistic experiences or not. Adults of the fifth generation were provided with a choice of aphids and eggs. The time of first prey encounter and prey first encountered along with latency to consume prey and prey first consumed were recorded. Non‐cannibalistic individuals preferred aphids over eggs, while cannibalistic individuals showed no preference. The time of first prey encounter and consumption were similar for aphids and eggs irrespective of the diet they were reared on. To assess the long‐term effects, offspring developmental duration and body weight were recorded across generations. Similar developmental duration of immature stages was recorded in the first and second generations of cannibalistic and non‐cannibalistic lines; however, prolonged developmental duration was recorded in cannibalistic lines when compared with non‐cannibalistic ones of later generations. Offspring of later generations developed faster in both lines. The offspring body weight of the second and fourth generations of both lines was found to be similar. However, a decline in body weight was recorded in cannibalistic offspring of the first, third and fifth generations when compared with non‐cannibalistic ones. A decline in the body weight of offspring across generations was observed in both lines. The findings suggest thatM. sexmaculatusrearing diet influences its preference for prey and that long‐term dietary conditioning can affect different fitness components. This could potentially reduce their effectiveness in biocontrol.

OOPHAGY IN THE TREE-HOLE DWELLING TADPOLES OF Ecnomiohyla sukia (HYLIDAE) IN COSTA RICA

The feeding strategy of the tadpoles of the Shaman Fringe-limbed Treefrog (Ecnomiohyla sukia), a canopy frog endemic to Costa Rica, is reported. A tree was climbed to collect three tadpoles at different stages, then the stomach contents were analyzed. Two of the three collected tadpoles had masses of eggs in their intestines. An analysis of stomach contents found evidence for the presence of around 200 eggs in one specimen. Ecnomiohyla sukia tadpoles are confirmed to be oophagous and can survive by feeding on conspecific eggs. We suggest that oophagy may also be present in other species of the genus Ecnomiohyla; they could use this strategy to supplement the limited food resources available in their microhabitats; however, more research is needed to confirm this.

Effects of co-occurrence and intra- and interspecific interactions between Drosophila suzukii and Zaprionus indianus.

In drosophilids, competition and coexistence can impact survivorship, growth, and reproductive output. Here, we evaluated direct competition between two co-occurring fruit flies, the spotted-wing drosophila Drosophila suzukii and the African fig fly Zaprionus indianus, comparing results from field collections with laboratory experiments. Field collections were conducted to evaluate co-occurrence between species. In the laboratory, different densities of eggs of each species were provided an artificial diet, and intra- and interspecific densities were evaluated regarding biological traits such as development and fecundity. Field collections showed a prevalence of Z. indianus, followed by other drosophilid species, including D. suzukii. Pupal survival and adult emergence were higher in D. suzukii than in Z. indianus at both intra- and interspecific densities, with decreasing values in response to increased densities. Fecundity did not differ significantly for either species at different intraspecific densities, but when reared together at different densities, Z. indianus was significantly more fecund than D. suzukii. Development time showed no significant difference at intraspecific densities, but when reared together, Z. indianus had longer development times than D. suzukii. Leslie Matrix projections indicated that D. suzukii showed practically the same dynamics at intraspecific and interspecific densities, with increasing oscillations at low and intermediate densities and decreasing oscillations at high densities. Zaprionus indianus showed a similar oscillation to D. suzukii, except at intermediate intraspecific densities, when the pattern was cyclic. Low interspecific densities resulted in decreasing oscillations. In the two-choice oviposition bioassays, D. suzukii females showed no significant preference for diets previously infested or not with either conspecific or heterospecific eggs at different densities. Understanding competitive interactions between co-occurring heterospecific species should be considered when establishing management tactics for spotted-wing drosophila.

Far-reaching benefits of the consumption of conspecific eggs by neonate larvae of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae): a case study on an artificial diet

BackgroundThe consumption of conspecific eggs by neonate larvae is a common behavior in aphidophagous coccinellids. However, it is still unknown what far-reaching benefits can be brought to the artificial diet-reared cannibals and whether the age of eggs and/or ovipositing parents can affect the cannibals’ fitness. Here, the multicolored Asian ladybird beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) was used as a research model because it exhibits much stronger cannibalism behavior than other beetles. Nine types of eggs, varying according to parental age at oviposition and egg age per se, were respectively provided as foods for H. axyridis neonate larvae until they developed to 2nd instar. After that, the larvae were fed on an artificial diet and whether egg consumption by neonate larvae had far-reaching benefits was evaluated. Those larvae that directly fed on artificial diet since hatching were served as control.ResultsCompared with the control beetles, the cannibal beetles (with few exceptions) had significantly higher 2nd instar-adult survivals (61.1–75.7% vs. 34.3%) and greatly shortened 2nd instar-adult duration (22.7–24.6 days vs. 27.8 days). At adult emergence, the female cannibal beetles (with few exceptions) had significantly higher fresh weights than the control beetles (14.5–16.3 mg vs. 11.7 mg). Among the nine types of cannibals, non-significant difference was detected in almost all the measured developmental parameters.ConclusionConsumption of conspecific eggs by neonate larvae of H. axyridis had far-reaching benefits for their subsequent development on artificial diet, and neither the egg age nor parental age at oviposition affects the cannibals’ fitness. These findings provided new insights into the combined application of conspecific eggs and artificial diets in the mass rearing of coccinellids.

Effect of victim relatedness on cannibalistic behaviour of ladybird beetle, Cheilomenes sexmaculata Fabricius (Coleoptera: Coccinellidae)

Cannibalism is taxonomically widespread and has a large impact on the individuals’ fitness and population dynamics. Thus, identifying how the rates of cannibalism are affected by different ecological cues is crucial for predicting species evolution and population dynamics. In current experiment, we investigated how victim relatedness affects the cannibalistic tendencies of different life stages of ladybird, Cheilomenes sexmaculata, which is highly cannibalistic. We provided larval instars and newly emerged adults of C. sexmaculata with a choice of sibling, half-sibling and non-sibling conspecific eggs as victim of cannibalism. First victim cannibalised and latency to cannibalise were observed along with total number of victims cannibalised after 24 h. First preference of victim did not differ with life stages of the cannibals though the number of victims cannibalized did increase with advancement in stage. Percent egg cannibalism also varied significantly with life stage and victim relatedness. First and second instars tend to cannibalise more percentage of sibling and non-sibling eggs while third instars cannibalised more percentage of non-sibling eggs; fourth instars and adults on the other hand cannibalised highest percentage of eggs irrespective of their relatedness. Insignificant effect of victim relatedness was observed on latency to cannibalise eggs, though it varied significantly with the cannibal’s life stage. Shortest latency to cannibalise was recorded for first instars and longest for adults and second instars. In conclusion, kin recognition and avoidance of cannibalism is stage-specific, with fourth instar and newly emerged adults being less discriminatory as compared to early stages owing to increased evolutionary survival pressure.

Energy expenditure affects the larval food preference in Propylea dissecta (Coleoptera: Coccinellidae)

Abstract Food preferences and choices are common among animals, including insects. Studies on food preferences have been done on coccinellids using eggs and aphids as diet, but information on the food choices of the aphidophagous ladybird, Propylea dissecta (Coleoptera: Coccinellidae), under laboratory conditions, is scarce. This study examined the effect of physical activity (walking) on food choice. We reared P. dissecta larvae on aphids, Aphis craccivora (Hemiptera: Aphididae), until the fourth-instar stage, and then allowed the fourth-instar larvae to walk on a glass rod for different time intervals to illustrate the energetic costs of foraging. After walking, larvae were provided simultaneous food choices of equidistantly placed food, i.e., A. craccivora, conspecific eggs, and heterospecific eggs. As the walking time duration gradually increased, the level of larval activity increased, resulting in poorer food choices.

Egg rejection and egg recognition mechanism in a Chinese Azure-winged Magpie (Cyanopica cyanus) population

Recognition and rejection of foreign eggs are effective defense of hosts against brood parasitism. However, brood parasitism can impose various selection pressures on different geographic populations of the same host species. In a multiple cuckoo system in China, Azure-winged Magpies (Cyanopica cyanus) are parasitized by both Indian Cuckoos (Cuculus micropterus) and Asian Koels (Eudynamys scolopaceus). In this study, egg recognition ability and recognition mechanism of the Azure-winged Magpie were investigated using a population in Fusong, southeastern Jilin, China. The results showed that 55.6% (20/36) of the Azure-winged Magpies correctly rejected quail (Coturnix japonica) eggs in their nests, while 13.9% (5/36) of the individuals experienced rejection costs by wrongly rejecting their own eggs. Azure-winged Magpies could accurately reject the experimental eggs when the number of such eggs in the nests was the same as that of the magpie eggs. However, Azure-winged Magpies do not recognize and reject conspecific eggs (0/28). The present study indicates that the Azure-winged Magpie has moderate egg recognition ability toward non-mimetic quail eggs and shows a true recognition mechanism with rejecting foreign eggs by accurately recognizing their own eggs. However, they cannot recognize conspecific eggs.

The Effects of Alternative Foods on Life History and Cannibalism of Amblyseius herbicolus (Acari: Phytoseiidae).

The development, survivorship, fecundity, and cannibalism of the predatory phytoseiid mite, Amblyseius herbicolus (Chant), fed six different alternative foods (Oulenziella bakeri, Tyrophagus putrescentiae, Aleuroglyphus ovatus, almond pollen (Prunus armeniaca), apple pollen (Malus pumila), maize pollen (Zea mays)), and natural prey (Tetranychus urticae) were determined in the laboratory. Our findings indicated that A. herbicolus that fed on all six alternative foods could normally complete its developmental and reproductive cycles. The shortest pre-adult developmental duration was observed when A. herbicolus fed on almond pollen (4.91 d) as well as T. urticae (4.90 d), and the longest when it fed on maize pollen (6.24 d). Pre-adult survival rates were higher when the predator fed on almond pollen (0.99), maize pollen (0.96), and O. bakeri (0.93). The highest fecundity was observed when A. herbicolus fed on apple pollen (28.55 eggs/female), almond pollen (26.06 eggs/female), and O. bakeri (26.02 eggs/female) in addition to T. urticae (48.95 eggs/female), and the lowest when it fed on maize pollen (7.84 eggs/female). The highest value of the intrinsic rate of increase (r) was obtained when A. herbicolus fed on O. bakeri (0.202 d-1) in addition to T. urticae (0.210 d-1), followed by almond pollen (0.163 d-1), and the lowest was when it fed on maize pollen (0.064 d-1). Cannibalism of conspecific eggs by adults of A. herbicolus did not occur when O. bakeri and T. urticae were provided. The cannibalism rate of the predatory mite was the lowest when fed on almond pollen, T. putrescentiae, and A. ovatus and the highest on apple pollen. Above all, when fed on O. bakeri and almond pollen, and with no or low cannibalism rate, A. herbicolus had the best development, survivorship, fecundity, and population parameters. Therefore, O. bakeri and almond pollen could be potential alternative foods for mass rearing programs of A. herbicolus or to support its population in the fields.

Changes in the gut microbial community of larvae of the harlequin lady beetle in response to cannibalism and intraguild predation

Diet affects the gut microbial community in most organisms, but the potential effects of cannibalism and intraguild predation (IGP) on the gut microbiota of predatory arthropods remain unexplored. Here, a series of feeding experiments examined changes in the gut microbial community of larvae of the predatory lady beetle Harmonia axyridis resulting from egg and larval cannibalism and IGP. We found that gut microbial abundance increased in fourth instar H. axyridis larva when conspecific eggs plus aphids were consumed as neonates, but did not change when their consumption was sustained across larval stages. In contrast, the consumption of Coccinella septempunctata eggs plus aphids over all larval stages decreased gut microbial abundance, whereas neonate consumption of the same had no such effect. Gut microbial composition differed following consumption of either conspecific or heterospecific eggs. Consumption of a C. septempunctata larva by molting H. axyridis third instar larvae decreased gut microbial abundance and diversity, whereas consumption of a conspecific larva increased them. Larval cannibalism and IGP appear to have variable effects on microbial composition due to differences in relative abundance of prevailing bacterial groups associated with these prey items. Our results indicate that cannibalism and IGP can have both quantitative and qualitative consequences for the gut microbial community in aphidophagous lady beetles.

Eat or be eaten? An observation of Podarcis erhardii consuming Scolopendra cingulata from Andros Island, Cyclades, Greece

Podarcis wall lizards mainly feed on coleopterans, orthopterans, arachnids, and other small invertebrates. However, Aegean wall lizards, Podarcis erhardii, are widely distributed across Aegean islands and are increasingly observed eating non-traditional food items ranging from plant material to conspecific eggs and body parts. Here, we report the first documented case of P. erhardii consuming a large centipede, Scolopendra cingulata. The predator-prey relationship between these species has appeared to go both ways and may intensify on islands.

Conflict over fertilization underlies the transient evolution of reinforcement.

When two species meet in secondary contact, the production of low fitness hybrids may be prevented by the adaptive evolution of increased prezygotic isolation, a process known as reinforcement. Theoretical challenges to the evolution of reinforcement are generally cast as a coordination problem, i.e., “how can statistical associations between traits and preferences be maintained in the face of recombination?” However, the evolution of reinforcement also poses a potential conflict between mates. For example, the opportunity costs to hybridization may differ between the sexes or species. This is particularly likely for reinforcement based on postmating prezygotic (PMPZ) incompatibilities, as the ability to fertilize both conspecific and heterospecific eggs is beneficial to male gametes, but heterospecific mating may incur a cost for female gametes. We develop a population genetic model of interspecific conflict over reinforcement inspired by “gametophytic factors”, which act as PMPZ barriers among Zea mays subspecies. We demonstrate that this conflict results in the transient evolution of reinforcement—after females adaptively evolve to reject gametes lacking a signal common in conspecific gametes, this gamete signal adaptively introgresses into the other population. Ultimately, the male gamete signal fixes in both species, and isolation returns to pre-reinforcement levels. We interpret geographic patterns of isolation among Z. mays subspecies considering these findings and suggest when and how this conflict can be resolved. Our results suggest that sexual conflict over fertilization may pose an understudied obstacle to the evolution of reinforcement.

Visual complexity of egg patterns predicts egg rejection according to Weber's law.

Visual complexity is ubiquitous in nature. Drivers of complexity include selection in coevolutionary arms races between antagonists. However, the causes and consequences of biological complexity and its perception are largely understudied, partly because complexity is difficult to quantify. Here, we address this by studying egg pattern complexity and its perception in hosts (tawny-flanked prinia Prinia subflava), which visually recognize and reject mimetic eggs of their virulent brood parasite (cuckoo finch Anomalospiza imberbis). Using field data and an optimization algorithm, we compute a complexity metric which predicts rejection of experimentally placed conspecific eggs in prinia nests. Real cuckoo finch eggs exhibit significantly lower pattern complexity than prinia eggs, suggesting that high complexity benefits hosts because it distinguishes host eggs from parasitic eggs. We show that prinias perceive complexity differences according to Weber's law of proportional processing (i.e. relative, rather than absolute, differences between stimuli are processed in discrimination, such that two eggs with simple patterns are more easily discriminable than two with complex patterns). This may influence coevolutionary trajectories of hosts and parasites. The new methods presented for quantifying complexity and its perception can help us to understand selection pressures driving the evolution of complexity and its consequences for species interactions.

A novel role for ATP2B in ascidians: Ascidian-specific mutations in ATP2B contribute to sperm chemotaxis.

Sperm chemotaxis, in which sperms are attracted to conspecific eggs via species-specific attractants, plays an important role in fertilization. This phenomenon has been observed in various animals and species-specific sperm attractants have been reported in some species. However, the mechanisms involved in the reception and recognition of the species-specific attractant by the sperms is poorly studied. Previously, we found that the plasma membrane-type Ca2+ /ATPase (PMCA) is the receptor for the sperm-activating and -attracting factor (SAAF) in the ascidian Ciona intestinalis. To determine the role of PMCA in species-specific sperm chemotaxis, we identified the amino acid sequences of PMCAs derived from six Phlebobranchia species. The testis-specific splice variant of PMCA was found to be present in all the species investigated and the ascidian-specific sequence was detected near the 3'-terminus. Moreover, dN/dS analysis revealed that the extracellular loops 1, 2, and 4 in ascidian PMCA underwent a positive selection. These findings suggest that PMCA recognizes the species-specific structure of SAAF at the extracellular loops 1, 2, and 4, and its testis-specific C-terminal region is involved in the activation and chemotaxis of ascidian sperms.

Egg cannibalism as a foraging tactic by less fit Glaucous-winged Gulls (Larus glaucescens)

Cannibalism, the killing and eating of conspecifics of any life stage, leads to a variety of behavioral and ecological consequences and is influenced by a range of environmental circumstances among numerous taxa. In birds, cannibalism is particularly well known among gulls. Although multiple studies have linked cannibalism to egg and chick failure in gull populations, gull cannibal behavior is poorly understood. During the 2014 and 2015 breeding seasons, we observed the behavior of Glaucous-winged Gulls (Larus glaucescens) that used conspecific egg predation, a form of cannibalism, as a feeding tactic on Protection Island, Washington, USA. Most egg stealing by egg cannibals occurred during colony disturbances, especially by Bald Eagles (Haliaeetus leucocephalus), but egg stealing often occurred without concurrent disturbances. Among other findings, our data showed that egg cannibals were always males, the number of eggs stolen each day correlated with the daily number of eggs laid, egg cannibals ate fewer fish than non-cannibals, and the reproductive success of egg cannibals was lower than that of non-cannibals. This study provides the most comprehensive evaluation to date of how larid cannibals find, capture, and eat conspecific eggs, and it includes the first assessment of reproductive success of egg cannibals in comparison with non-cannibals.