Egg Predation Research Articles

Consistent cooperation in a cichlid fish is caused by maternal and developmental effects rather than heritable genetic variation.

Studies on the evolution of cooperative behaviour are typically confined to understanding its adaptive value. It is equally essential, however, to understand its potential to evolve, requiring knowledge about the phenotypic consistency and genetic basis of cooperative behaviour. While previous observational studies reported considerably high heritabilities of helping behaviour in cooperatively breeding vertebrates, experimental studies disentangling the relevant genetic and non-genetic components of cooperative behaviour are lacking. In a half-sibling breeding experiment, we investigated the repeatability and heritability of three major helping behaviours performed by subordinates of the cooperatively breeding fish Neolamprologus pulcher To experimentally manipulate the amount of help needed in a territory, we raised the fish in two environments differing in egg predation risk. All three helping behaviours were significantly repeatable, but had very low heritabilities. The high within-individual consistencies were predominantly due to maternal and permanent environment effects. The perceived egg predation risk had no effect on helping, but social interactions significantly influenced helping propensities. Our results reveal that developmentally plastic adjustments of provided help to social context shape cooperative phenotypes, whereas heritable genetic variation plays a minor role.

A real-time PCR approach to detect predation on anchovy and sardine early life stages

Recruitment of sardine (Sardina pilchardus Walbaum, 1792) and anchovy (Engraulis encrasicolus Linnaeus, 1758) is thought to be regulated by predation of their eggs and larvae. Predators of sardine and anchovy can be identified by visual taxonomic identification of stomach contents, but this method is time consuming, tedious and may underestimate predation, especially in small predators such as fish larvae. Alternatively, genetic tools may offer a more cost-effective and accurate alternative. Here, we have developed a multiplex real-time polymerase chain reaction (RT-PCR) assay based on TaqMan probes to simultaneously detect sardine and anchovy remains in gut contents of potential predators. The assay combines previously described and newly generated species-specific primers and probes for anchovy and sardine detection respectively, and allows the detection of 0,001ng of target DNA (which corresponds to about one hundredth of the total DNA present in a single egg). We applied the method to candidate anchovy and sardine egg predators in the Bay of Biscay, Atlantic Mackerel (Scomber scombrus) larvae. Egg predation observed was limited primarily to those stations where sardine and/or anchovy eggs were present. Our developed assay offers a suitable tool to understand the effects of predation on the survival of anchovy and sardine early life stages.

Indigenous arthropod natural enemies of the invasive brown marmorated stink bug in North America and Europe

Since the establishment of the brown marmorated stink bug, Halyomorpha halys (Stal) (Hemiptera: Pentatomidae) in North America and Europe, there has been a large, multi-group effort to characterize the composition and impact of the indigenous community of arthropod natural enemies attacking this invasive pest. In this review, we combine 98 indigenous natural enemy datasets spanning a variety of sampling methods, habitats, and geographic areas. To date, the vast majority of H. halys biological control research has focused on the egg stage, using sentinel egg masses to characterize indigenous parasitoid and predator communities and their contribution to H. halys egg mortality. Although egg parasitism and predation levels by indigenous natural enemies are low (typically <10% each) in most surveys, total egg mortality attributable to natural enemies can be higher (typically between 5 and 25%; up to 83%)—even though these values were likely underestimated in most cases because some mortality due to biological control was not recognized. In North America, where the most data are available, it appears that the relative prevalence of different indigenous parasitoid species varies among habitat types, particularly between crop and non-crop habitats. Predator species responsible for egg mortality are much less commonly identified, but appear to include a wide variety of generalist chewing and sucking predators. To date, studies of natural enemies attacking H. halys nymphs and adults are relatively rare. Based on our review, we identify a number of key research gaps and suggest several directions for future research.

Partner swapping and cheating: why do different minnow species spawn together?

Partner swapping and cheating: why do different minnow species spawn together?

Population dynamics of Saissetia oleae. II. Life-tables and key-factor analysis

A series of life-tables for the population of Saisselia oleae (Oliv.) (Homoptera: Coccidae) during five yearly generations (1981-86) were constructed in Corfu. Key-factor analysis carried out on the life-table data indicated that mortality of young stages during summer, caused mainly by the high temperatures, and mortality during spring, caused mainly by predation, determine total population change within each generation. These two mortality factors are the predominant factors of the population dynamics of S. oleae determining population fluctuations. The other mortality factors of the population system of S. oleae were less important. Summer parasites and egg predators, in particular, do not play any significant role on the population dynamics of S. oleae.

Preliminary results for the eνaluation of the action of Saissetia oleae parasites in Corfu.

The action of parasites of Saissetia οleae (OIiv.) (Homoptera-Cοccidae) is studied in Corfu from 1980 in the framework of an ongoing project on the population dynamics of Saissetia οleae. Results obtained during the period 1980-1983 from 17 experimental sites indicate the following: a) the population of S. οleae increased in 1981 but from 1982 it declined to very low levels; following the overall decline of the host population, parasitization rates of third instar larvae (mainly by Μetaphycus helνolus Comp.) were relatively low and ranged from 2.1% to 6.7% for the autumn period and from 14.6% to 29.4% for the spring period; this does not minimize the possibility that Μetaphycus helνolus plays an important role on the regulation οf S. οleae populations; b) a considerable proportion of females of S. οleae is attacked during summer by Μetaphycus lounsburyi How. (an internal parasite on preovipositing females), Μoranila californica How. and Scutellista cyanea Μοtsch. (egg predators), but their significance upon the population system of S. οleae is not expected to be great. The action of Μetaphycus lounsburyi in spring, when the peak of the suitable stage occurs (i.e. fourth instar larvae), appears to be very low, at least for these three years. Its action is delayed and most of the specimens of this parasite emerge from ovipositing females in early summer. Among the species attacking S. οleae females, Μ. californica (recently introduced in Corfu) was the most abundant and it might be worthy to be introduced to other parts of Greece too.

Predation on Atlantic herring (Clupea harengus) eggs by the resident predator community in coastal transitional waters

AbstractAtlantic herring (Clupea harengus) migrates from offshore to coastal areas to spawn and their eggs and larvae may substantially increase prey resources for resident predators. We combined an in situ predator exclusion experiment using eggs naturally spawned on submerged aquatic vegetation and field observations of predator abundance to estimate the magnitude of predation mortality of herring eggs. During our predator exclusion experiment, performed in an important spawning ground in the southwest Baltic Sea, 20% of the herring eggs were consumed resulting in an extrapolated predation of 42% of all eggs between spawning and hatch. Abundance and stomach content analyses indicated that one predator (threespine stickleback, Gasterosteus aculeatus) was responsible for the majority of the predation impact. Predation mortality estimates from this in situ study were more than 10‐fold higher than those of an empirical egg predation model for the same predator in the same region. Our findings highlight the potential of resident predators to regulate the survival of early life stages of ocean‐going fishes that rely on the nursery functions of inshore transitional waters.

Within‐patch oviposition site shifts by spider mites in response to prior predation risks decrease predator patch exploitation

AbstractIn egg‐laying animals with no post‐oviposition parental care, between‐ or within‐patch oviposition site selection can determine offspring survival. However, despite the accumulation of evidence supporting the substantial impact predators have on oviposition site selection, few studies have examined whether oviposition site shift within patches (“micro‐oviposition shift”) reduces predation risk to offspring. The benefits of prey micro‐oviposition shift are underestimated in environments where predators cannot disperse from prey patches. In this study, we examined micro‐oviposition shift by the herbivorous mite Tetranychus kanzawai in response to the predatory mite, Neoseiulus womersleyi, by testing its effects on predator patch exploitation in situations where predatory mites were free to disperse from prey patches. Adult T. kanzawai females construct three‐dimensional webs on leaf surfaces and usually lay eggs under the webs; however, females that have experienced predation risks, shift oviposition sites onto the webs even in the absence of current predation risks. We compared the predation of eggs on webs deposited by predator‐experienced females with those on leaf surfaces. Predatory mites left prey patches with more eggs unpredated when higher proportions of prey eggs were located on webs, and egg survival on webs was much higher than that on leaf surfaces. These results indicate that a micro‐oviposition shift by predator‐experienced T. kanzawai protects offspring from predation, suggesting adaptive learning and subsociality in this species. Conversely, fecundity and longevity of predator‐experienced T. kanzawai females were not reduced compared to those of predator‐naïve females; we could not detect any costs associated with the learned micro‐oviposition shift. Moreover, the previously experienced predation risks did not promote between‐patch dispersal of T. kanzawai females against subsequently encountered predators. Based on these results, the relationships of between‐patch oviposition site selection and micro‐oviposition shift are discussed.

Common Eider and large gull and nesting associations in coastal Labrador

Apparent nesting associations between avian egg predators and their prey have received much interest, with gulls and waterfowl receiving considerable attention. We examined the co-occurrence of breeding large gulls (Herring Gull (Larus argentatus Pontoppidan, 1763) and Great Black-backed Gull (Larus marinus L., 1758)) and Common Eiders (Somateria mollissima L., 1758) along the coast of Labrador from 1998 to 2003. Nest counts for large gulls and eiders were undertaken by ground crews on 45–109 islands each year, counting 79–283 and 721–3424 nests annually, respectively. Gulls were more likely to nest on an island with nesting eiders (69.4%) than without nesting eiders (38.4%), and the probability and numbers of gulls nesting on an island increased as eider colony size increased. Large gulls were 1.76 times more likely to occupy islands that had nesting eiders in the previous year, while eiders were equally likely to colonize islands that did or did not have nesting gulls in the previous year. Eiders were no more likely to abandon islands that had nesting gulls in the previous year. In subarctic coastal landscapes, large gulls appear to preferentially nest in association with nesting eiders, while eiders appear not to avoid nesting islands based on the previous presence of large gulls.

A new species of Carcinonemertes, Carcinonemertes conanobrieni sp. nov. (Nemertea: Carcinonemertidae), an egg predator of the Caribbean spiny lobster, Panulirus argus.

A new species of nemertean worm belonging to the genus Carcinonemertes is described from egg masses of the Caribbean spiny lobster Panulirus argus from the Florida Keys, Florida, USA. This is the first species of Carcinonemertes reported to infect P. argus or any other lobster species in the greater Caribbean and western Atlantic Ocean. Carcinonemertes conanobrieni sp. nov. varies in body color from a translucent white to a pale orange, with males ranging in total body length from 2.35 to 12.71 mm and females ranging from 0.292 to 16.73 mm. Among the traits that separate this new species from previously described species in the genus Carcinonemertes are a relatively wide stylet basis, minimal sexual size dimorphism, and a unique mucus sheath decorated with external hooks. Also, juvenile worms were found to encyst themselves next to lobster embryos and female worms lay both long strings of eggs wound throughout the lobster’s setae as well as spherical cases that are attached to lobster embryos. The stylet length and stylet basis remain unchanged throughout ontogeny for both male and female worms. Maximum likelihood and Bayesian inference phylogenetic analyses separated this newly described species from all other species of Carcinonemertes with available COI sequences. Carcinonemertes spp. are voracious egg predators and have been tied to the collapse of various crustacean fisheries. The formal description of this new species represents the first step to understand putative impacts of this worm on the population health of one of the most lucrative yet already depressed crustacean fisheries.

New occurrence of a non-native ornamental cichlid in the Paranapanema River, southern Brazil

Fish introductions are common practices due to intentionally or unintentionally translocations of species between watersheds. Herein we report the spread of the non-native cichlid Laetacara araguaiae Ottoni &amp; Costa 2009 in the Paranapanema River basin, southern Brazil. Native from the Araguaia River (Central Brazil), this species was probably introduced by releases made by aquarists. Its new area of occurrence is characterized as natural nursery and important for the life cycle of native fish. Due to its biological characteristics, the species has the ability to cause a negative impact on the aquatic biota through possible interactions, such as predation of eggs, larvae and juveniles of native fish, and spread of parasites.Keywords: biological invasion, Cichlinae, fish, exotic species, Upper Paraná River basin.

Diel, lunar, and seasonal spawning patterns of the Atlantic goliath grouper, Epinephelus itajara, off Florida, United States

The diel, lunar, and seasonal timing of spawning in Atlantic goliath grouper Epinephelus itajara (Lichtenstein, 1822) in the United States is highly specific, occurring at night during new moon phases of August, September, and October. We derive these patterns from four lines of evidence apparent on spawning sites during the known spawning season: (1) from the transitory appearance of fish aggregations; (2) from simultaneous recordings of goliath grouper nighttime calls and nighttime vertical ascents that were far more frequent during the new moon phase than on the full moon; (3) from collections of goliath grouper eggs (genetically verified) at night downstream from known spawning sites; and (4) from significantly higher frequencies of both hydrated oocytes (indicating imminent spawning) and postovulatory follicles (indicating recent spawning) in ovarian biopsies taken from goliath grouper captured on spawning sites during new moon phases relative to full moon phases. We suggest that dark-night spawning is an adaptation minimizing egg predation by several species of scad [Decapterus punctatus (Cuvier,1829), Decapterus tabl Berry,1968, and Decapterus macarellus (Cuvier,1833)] and herring [Sardinella aurita Valenciennes,1847 and Etrumeus teres (DeKay,1842)] that are abundant on goliath grouper spawning sites.The seasonal spawning of goliath grouper, late summer–early fall, coincides with habitat conditions considered ideal for settlement of early juveniles in mangrove nurseries.

Breeding Status of the Red-Tailed Tropicbird (Phaethon rubricauda) and Threats to Its Conservation on Easter Island (Rapa Nui)

Easter Island is located in the southeastern corner of Polynesia. This 163.6 km2 volcanic island is one of the most isolated places on Earth. During spring 2014 and 2015, we studied a breeding colony of Red-tailed Tropicbirds ( Phaethon rubricauda ) located on Rano Raraku Volcano. We specifically aimed to determine (1) main nest types used by tropicbirds, (2) nest distribution and abundance, (3) breeding success, and (4) threats faced by tropicbirds at this colony. Results showed presence of four nest types: rock caves, moai nest, rock-protected, and vegetation nests. Nests were strongly associated with unfinished moai statues. Breeding success ranged from 37% in 2014 to 26% in 2015. Camera traps and direct observations showed interactions with five invasive alien species: the raptor Chimango Caracara ( Milvago chimango ) was the most severe predator of unattended eggs and chicks; cats were observed close to adult birds; dogs killed fledglings; ants preyed on newborn chicks; rats were recorded inspecting both occupied and unoccupied nests. We suggest that this is a relatively new and expanding colony. Urgent measures to control and/or eradicate invasive alien species on Rano Raraku are needed to improve breeding success and persistence of this colony in the future.

Local and landscape drivers of predation services in urban gardens.

In agroecosystems, local and landscape features, as well as natural enemy abundance and richness, are significant predictors of predation services that may result in biological control of pests. Despite the increasing importance of urban gardening for provisioning of food to urban populations, most urban gardeners suffer from high pest problems, and have little knowledge about how to manage their plots to increase biological control services. We examined the influence of local, garden scale (i.e., herbaceous and arboreal vegetation abundance and diversity, ground cover) and landscape (i.e., landscape diversity and surrounding land use types) characteristics on predation services provided by naturally occurring predators in 19 urban gardens in the California central coast. We introduced sentinel pests (moth eggs and larvae and pea aphids) onto greenhouse-raised plants taken to gardens and assigned to open or bagged (predator exclosure) treatments. We found high predation rates with between 40% and 90% of prey items removed in open treatments. Predation services varied with local and landscape factors, but significant predictors differed by prey species. Predation of eggs and aphids increased with vegetation complexity in gardens, but larvae predation declined with vegetation complexity. Smaller gardens experienced higher predation services, likely due to increases in predator abundance in smaller gardens. Several ground cover features influenced predation services. In contrast to patterns in rural agricultural landscapes, predation on aphids declined with increases in landscape diversity. In sum, we report the relationships between several local management factors, as well as landscape surroundings, and implications for garden management.

The distribution and abundance of Blue Petrels (Halobaena caerulea) breeding at subantarctic Marion Island

ABSTRACTBlue Petrels (Halobaena caerulea) are known to breed at seven locations in the Southern Ocean. Population estimates have been made recently for the two major breeding sites, but accurate estimates are lacking for the remaining locations. We used a systematic survey technique to estimate the size of the population breeding at Marion Island (290 km2), the larger of the two Prince Edward Islands. A combination of colony area and density estimates suggested there were 214 700 Blue Petrel burrows on Marion Island in 2012. Burrow occupancy rates at the mid-incubation stage averaged 82% (range 36–98%), suggesting a total breeding population of 145 000 pairs (95% confidence interval 110 000–180 000). There appeared to be some range expansion since the population was mapped in the mid-1980s. Predation of chicks and eggs by introduced house mice (Mus musculus) could be affecting the recovery of Blue Petrels since feral cats (Felis catus) were eradicated in 1991. Based on our count from Marion Island alone, the Prince Edward Islands support the third largest population of Blue Petrels globally, after Diego Ramirez Islands and the Kerguelen Islands.

Effectiveness of maternal egg attendance in an exclusively cave‐dwelling harvestman (Arachnida: Opiliones)

AbstractEgg attendance is the most common and phylogenetically widespread form of post‐ovipositional care among ectotherms. The main benefit of egg attendance is to enhance offspring survival by preventing or attenuating attacks from natural enemies. In arachnids, there are few experimental studies on the benefits of egg attendance, and they pertain to species living in few types of habitats, mainly forests. To understand how the benefits of egg attendance vary in large geographical scales, we need to include species from poorly explored habitats, such as caves. Here, we describe a case of maternal egg attendance in an exclusive cave‐dwelling harvestman, Phalangodus briareos. Using a parent removal experiment, we also assessed the benefits of egg attendance. We found that egg attendance improves egg survival because unattended clutches were almost entirely consumed by conspecifics and crickets. When females were maintained on their clutches, egg survival was always high, regardless of female body size. There was a positive effect of clutch size on egg predation, which was higher during nighttime. We suggest that larger clutches emit more chemical cues, attracting more predators in the cave habitat. Finally, we argue that the benefits of egg protection should be higher inside caves when compared to external habitats because food is scarce inside caves and the fauna consists mainly of predators and detritivores.

From laboratory to field: electro-antennographic and behavioral responsiveness of two insect predators to methyl salicylate

Methyl salicylate (MeSA) is a commonly emitted herbivore-induced plant volatile (HIPV) known to attract insect predators in agricultural crops. However, thorough studies on whether MeSA can increase their ecological functioning or their attraction under field conditions are still lacking. Here, we conducted laboratory, greenhouse, and field studies to address the hypothesis that two agriculturally important predatory insects (the ladybeetle Hippodamia convergens Guerin-Meneville and the lacewing Chrysoperla rufilabris Burmeister) respond physiologically and behaviorally to MeSA, which may lead to increased predation and oviposition. In laboratory studies using electro-antennography, we found that male and female H. convergens and C. rufilabris antennae can detect MeSA; however, for both species, female antennae responded more strongly. In greenhouse studies using cages and wind tunnels, H. convergens females were attracted to, and arrested by, MeSA; this attraction increased egg predation. Attraction of C. rufilabris females to MeSA also increased oviposition. In field studies, mark-release-recapture experiments were performed to investigate H. convergens and C. rufilabris attraction to MeSA over various distances in cranberry fields. More H. convergens and C. rufilabris were caught on yellow sticky cards placed close (0–30 m) to the predator release site than at farther distances, regardless of whether the cards were baited with MeSA or not. In conclusion, H. convergens and C. rufilabris adults detected, and were attracted to, MeSA under laboratory and greenhouse conditions, resulting in higher predation and oviposition, but this attraction was not observed under field conditions. These results demonstrate that predator responses to HIPVs can be complex in real agricultural settings.

Biparental incubation pattern of the Black-necked Crane on an alpine plateau

The biparental incubation model is an excellent one for investigating how parents resolve sexual conflict and achieve cooperation, especially in cold alpine environments. We used video monitoring of 20 nests 24 h/day to systematically investigate the incubation pattern of the Black-necked Crane (Grus nigricollis), a biparental waterbird with threatened status (International Union for Conservation of Nature vulnerable status), inhabiting the Qinghai-Tibetan Plateau, China. Analysis of 3886 h of video recordings indicated high nest attendance (90.1%) by Black-necked Crane parents across 14 nests, with almost equal female and male nest attendance (45.4 vs. 44.8%). The average length of an incubation bout was 2.06 h, with frequent changeovers (10.87 times/day, lasting on average 5.05 min). Males spent significantly more time returning to the nest than females (5.57 vs. 4.65 min, t 180 = −46.61, P < 0.001) after the partner left the nest. Six of 20 monitored nests failed, mainly due to egg predation, egg collection, or adverse weather. We provide the first evidence that, under natural environmental conditions, both males and females respond to reduced partner effort with diverse strategies. On average, full compensation was greater than 100% for the decreased partner effort. In this long-lived species with long-lasting pair bonds and low fecundity, a mate may overly compensate for reduced partner investment to avoid forfeiting the current breeding attempt. Our results indicate that females and males are allocated different tasks with complementary patterns during incubation, enhancing egg care efficiency in an alpine plateau environment with severe threats. Both social and natural environmental factors may shape the incubation pattern of Black-necked Cranes.

Spawning aggregation of white-streaked grouper Epinephelus ongus: spatial distribution and annual variation in the fish density within a spawning ground.

White-streaked grouper (Epinephelus ongus) is an important fisheries target and forms spawning aggregations at particular spawning grounds. The aims of the present study were to investigate the ecological characteristics of annual spawning aggregations such as (1) spatial variations in the density of E. ongus at the spawning ground, (2) the relationship between fish density and environmental variables, (3) inter-annual variations in the spawning aggregation, (4) the proportion of males to females at the spawning ground for several days pre—and post-spawning and (5) the relationship between male density and female density at the protected spawning ground, based on observations over five years at an Okinawan coral reef. Although the protected spawning ground area was large (ca. 2,500 m × 700 m), high density of E. ongus (over 25 individuals per 100 m2) was found in a limited area (within c.a. 750 m × 50 m). Current velocity and coverage of rocks had significant positive effects on the spatial distribution of E. ongus at the spawning ground. Inter-annual variation in the degree of aggregation was found and this variation was explained by the annual variation of mean seawater temperature during 40 days before the spawning day. The male–female ratio (male:female) at the spawning ground was ca. 3:1 for three years (May 2012, May 2014 and May 2015) whereas >13:1 for one year (May 2013). Significant positive relationships between male density and female density were found at the aggregation sites. It is suggested that E. ongus use aggregation sites with greater current velocity to reduce the risk of egg predation and seawater temperature is one of the main factors that is responsible for determining the degree of aggregation. It is also suggested that females possibly select sites with a greater density of males and this selection behavior might be the reason why females arrived at the spawning ground after the arrival of the males. For effective management of spawning grounds, precise site selection as well as the duration of the protection period are suggested to be key aspects to protect the spawning aggregations of E. ongus, which have been currently achieved at the spawning ground.

Identification and evaluation of semiochemicals for the biological control of the beetle Omorgus suberosus (F.) (Coleoptera: Trogidae), a facultative predator of eggs of the sea turtle Lepidochelys olivacea (Eschscholtz).

The beetle Omorgus suberosus (F.) is a facultative predator of eggs of the olive ridley turtle Lepidochelys olivacea (Eschscholtz). Laboratory and field investigations were conducted in order to characterize volatile attractants of O. suberosus and to explore the potential for application of these volatiles in a selective mass trapping method. Headspace sorptive extraction (HSSE) coupled to thermo-desorption gas chromatography–mass spectrometry (TD-GC-MS) analysis of the volatile constituents from beetles or turtle nests revealed 24 potential compounds. However, electroantennographic (EAG) measurements revealed antennal sensitivity only to indole, linoleic acid, trimethylamine, dimethyl sulphide, dimethyl disulphide and ammonia. Behavioural tests showed that these compounds are highly attractive to O. suberosus. Field trapping experiments revealed that indole and ammonia were more attractive than the other volatile compounds and showed similar attractiveness to that produced by conventional baits (chicken feathers). The use of a combined bait of indole and NH3 would therefore be the most effective trap design. The data presented are the first to demonstrate effective massive capture of O. suberosus using an attractant-based trapping method. These findings have potential for the development of an efficient mass trapping method for control of this beetle as part of efforts towards conservation of L. olivacea at La Escobilla in Oaxaca, Mexico.