Predation Pressure Research Articles

Temporal and spatial refugia modify predation risk for non-native crabs in rocky intertidal habitats.

Populations of the non-native Asian shore crab, Hemigrapsus sanguineus, now dominate the rocky intertidal of southern New England, USA. High abundances suggest the recent invader may have experienced enhanced success as a result of enemy release. While larvae and juveniles may serve as a food source for ecologically important species, little is known about predation of mature H. sanguineus or the influence of habitat on predation pressure. To assess natural predation rates of adult H. sanguineus, crabs were tethered in the intertidal at Clarks Cove in New Bedford, MA. Crabs were left in situ for half of a tidal cycle then observed for signs of predation. Results of separate high and low tide trials showed that adult crabs were preyed upon at both high and low tide, though at a significantly higher rate during high tide during both daytime and nighttime, suggesting predation by aquatic species is greater than that by terrestrial species. To investigate the role of habitat as refuge from predation, a laboratory experiment manipulated the complexity of habitat provided to crabs in the presence of a native fish predator. Results indicate better refuge is provided by more complex shelter. Together, findings suggest that fish, crabs, and/or diving birds are important predators for H. sanguineus in the invaded range and that habitat refuge acts to reduce predation pressure.

Balancing between predation risk and food by boreal breeding ducks.

Wetlands belong to the globally most threatened habitats, and organisms depending on them are of conservation concern. Wetland destruction and quality loss may affect negatively also boreal breeding ducks in which habitat selection often needs balancing between important determinants of habitat suitability. In Finland duck population trajectories are habitat-specific, while the reasons behind are poorly understood. In this research, we studied the balance of nest predation risk and invertebrate food abundance in boreal breeding ducks in Finland at 45 lakes and ponds in 2017 and 2018. We surveyed duck pairs and broods from these and 18 additional water bodies. We evaluated nest predation by monitoring artificial nests with camera traps over a 7-day exposure period and sampled invertebrates from water bodies using emergence and activity traps. Camera trap results indicate that predation risk was higher in the water bodies surrounded by agricultural land than in forestland. Ponds (seasonal, beaver, and man-made) had lower nest predation risk, and they were also more invertebrate-rich than permanent lakes. In addition, artificial nests further away from water bodies had higher survival than shoreline nests. Habitat use of duck pairs was not associated with invertebrate food, but duck broods preferred habitats rich in food. High nest predation pressure in shorelines of especially agricultural landscapes may contribute to the declining population trends of ducks in Finland. Controlling predators could be an important conservation action to improve duck breeding success. This research underlines the benefits of the availability of different water body types for breeding ducks. There is an urgent need to pay attention to protecting seasonal ponds, while the lack of flooded waters may be mitigated by favouring beavers or creating man-made ponds.

Variation in Avian Predation Pressure as a Driver for the Diversification of Periodical Cicada Broods.

AbstractPeriodical cicadas live 13 or 17 years underground as nymphs, then emerge in synchrony as adults to reproduce. Developmentally synchronized populations called broods rarely coexist, with one dominant brood locally excluding those that emerge in off years. Twelve modern 17-year cicada broods are believed to have descended from only three ancestral broods following the last glaciation. The mechanisms by which these daughter broods overcame exclusion by the ancestral brood to synchronously emerge in a different year, however, are elusive. Here, we demonstrate that temporal variation in the population density of generalist predators can allow intermittent opportunities for new broods to invade, even though a single brood remains dominant most of the time. We show that this mechanism is consistent, in terms of the type and frequency of brood replacements, with the distribution of periodical cicada broods throughout North America today. Although we investigate one particularly charismatic case study, the mechanisms involved (competitive exclusion, Allee effects, trait variation, predation, and temporal variability) are ubiquitous and could contribute to patterns of species diversity in a range of systems.

Mesozooplankton communities in deep-water areas of the Black Sea: are their composition and biomass regulated by the Ctenophore Mnemiopsis leidyi A. Agassiz, 1865?

The abundance, biomass, distribution and feeding patterns of the ctenophoreMnemiopsisleidyiA. Agassiz 1865 were studied in the deep-water Black Sea in October 2019. The biomass of the ctenophore in the open areas of the sea was 100–200 g m–2, the abundance was 16–38 ind. m–2. With the dominance of large individuals (≥30 mm) in the population, the activity of their reproduction remained extremely weak. The specific daily ration varied from ~4% to 13% of body carbon in adults and juveniles, respectively, and exceeded the minimum food requirements of the ctenophore. The daily consumption of three species of copepods (Acartiaspp.,Calanus euxinus,Oithona davisae) byM. leidyireached 4.5–11% of their biomass, while that of appendiculariansOikopleura(Vexillaria)dioica– 1.6%. The predatory pressure ofM. leidyion the entire prey zooplankton attained 2–4% of the biomass of organisms per day.

Microbial eukaryotic predation pressure and biomass at deep-sea hydrothermal vents.

Deep-sea hydrothermal vent geochemistry shapes the foundation of the microbial food web by fueling chemolithoautotrophic microbial activity. Microbial eukaryotes (or protists) play a critical role in hydrothermal vent food webs as consumers and hosts of symbiotic bacteria, and as a nutritional source to higher trophic levels. We measured microbial eukaryotic cell abundance and predation pressure in low-temperature diffuse hydrothermal fluids at the Von Damm and Piccard vent fields along the Mid-Cayman Rise in the Western Caribbean Sea. We present findings from experiments performed under in situ pressure that show cell abundances and grazing rates higher than those done at 1 atmosphere (shipboard ambient pressure); this trend was attributed to the impact of depressurization on cell integrity. A relationship between the protistan grazing rate, prey cell abundance, and temperature of end-member hydrothermal vent fluid was observed at both vent fields, regardless of experimental approach. Our results show substantial protistan biomass at hydrothermally fueled microbial food webs, and when coupled with improved grazing estimates, suggest an important contribution of grazers to the local carbon export and supply of nutrient resources to the deep ocean.

Does daily activity overlap of seven mesocarnivores vary based on human development?

Many species of wildlife alter their daily activity patterns in response to co-occurring species as well as the surrounding environment. Often smaller or subordinate species alter their activity patterns to avoid being active at the same time as larger, dominant species to avoid agonistic interactions. Human development can complicate interspecies interactions, as not all wildlife respond to human activity in the same manner. While some species may change the timing of their activity to avoid being active when humans are, others may be unaffected or may benefit from being active at the same time as humans to reduce predation risk or competition. To further explore these patterns, we used data from a coordinated national camera-trapping program (Snapshot USA) to explore how the activity patterns and temporal activity overlap of a suite of seven widely co-occurring mammalian mesocarnivores varied along a gradient of human development. Our focal species ranged in size from the large and often dominant coyote (Canis latrans) to the much smaller and subordinate Virginia opossum (Didelphis virginiana). Some species changed their activity based on surrounding human development. Coyotes were most active at night in areas of high and medium human development. Red fox (Vulpes vulpes) were more active at dusk in areas of high development relative to areas of low or medium development. However, because most species were primarily nocturnal regardless of human development, temporal activity overlap was high between all species. Only opossum and raccoon (Procyon lotor) showed changes in activity overlap with high overlap in areas of low development compared to areas of moderate development. Although we found that coyotes and red fox altered their activity patterns in response to human development, our results showed that competitive and predatory pressures between these seven widespread generalist species were insufficient to cause them to substantially alter their activity patterns.

Avoiding cantharidin through ionotropic receptors

The discernment and aversion of noxious gustatory stimuli profoundly influence homeostasis maintenance and survival of fauna. Cantharidin, a purported aphrodisiac, is a monoterpenoid compound secreted by many species of blister beetle, particularly by the Spanish fly, Lytta vesicatoria. Although the various advantageous functions of cantharidin have been described, its taste analysis and toxic properties in animalshave been rarely explored. Our study using Drosophila melanogaster examines the taste properties of cantharidin along with its potential hazardous effect in the internal organs of animals. Here, we find that cantharidin activates bitter taste receptors. Our findings show that specific ionotropic receptors (IR7g, IR51b, and IR94f) in labellar bitter-sensing neurons, along with co-receptors IR25a and IR76b, are responsible for detecting cantharidin. By introducing the IR7g and IR51b in sweet and bitter neurons, naturally expressing IR76b and IR25a, we show that these genes are sufficient for cantharidin perception. Moreover, we witness the deleterious ramifications of cantharidin on survival and visceral integrities, shedding light on its hazardous effect.

Wood warbler population dynamics in response to mast seeding regimes in Europe.

Mast seeding is the episodic, massive production of plant seeds synchronized over large areas. The resulting superabundance of seeds represents a resource pulse that can profoundly affect animal populations across trophic levels. Following years of high seed production, the abundance of both seed consumers and their predators increase. Higher predator abundance leads to increased predation pressure across the trophic web, impacting nonseed consumers such as the wood warbler Phylloscopus sibilatrix through increased nest predation after tree mast years. Over the past 30 years, the frequency of tree seed masts has increased, while wood warbler populations have declined in several regions of Europe. We hypothesized that increasing mast frequencies may have contributed to the observed population declines by creating suboptimal breeding conditions in years after masting. We measured reproductive output in four study areas in central Europe, which was between 0.61 and 1.24 fledglings lower in the years following masting than nonmasting. For each study area, we used matrix population models to predict population trends based on the estimated reproductive output and the local mast frequencies. We then compared the predicted with the observed population trends to assess if the frequency of mast years had contributed to the population dynamics. In Wielkopolska National Park (PL) and Hessen (DE), masting occurred on average only every 4 years and populations were stable or nearly so, whereas in Jura (CH) and Białowieża National Park (PL), masting occurred every 2 and 2.5 years, respectively, and populations were declining. The simple matrix population models predicted the relative difference among local population trends over the past 10-20 years well, suggesting that the masting frequency may partly explain regional variation in population trends. Simulations suggest that further increases in mast frequency will lead to further declines in wood warbler populations. We show that changes in a natural process, such as mast seeding, may contribute to the decline in animal populations through cascading effects.

Do cuckoo calls affects red-backed shrike settlement pattern? An experimental approach

Birds select breeding territories by assessing territory quality and considering predation pressure. However, in many small passerines, brood parasitism may also play an important role in territory occupancy. Settlement decisions are made under time pressure, especially for late migrants. An example of late migrants is the red-backed shrike Lanius collurio, a species wintering in sub-tropical Africa, which serves as a host for the common cuckoo Cuculus canorus and arrives in territories a few days later than their brood parasite. We expected that arriving red-backed shrikes avoided territories with common cuckoo presence. Then, we tested how experimentally provided artificial playback calls of the common cuckoo and woodpigeon (treated as control) affected the probability of red-backed shrike settlement. In the breeding season 2021, we observed 279 red-backed shrike territories to assess the effect of playback of common cuckoo calls on their host presence. Moreover, we adopt information on shrike territories collected in previous years to establish territory quality, measured by occupancy pattern over years. Each of these places was also checked for the presence of corvids, which are predators of shrike nests. We did not find difference with lower preference of shrikes towards cuckoo calls and to pigeon calls Columba columbus, what suggest the human presence and manipulation in the territories during experiments with recorders should be incorporated as an important factor to understanding shrikes’ settlement behaviour. What is interesting we found no negative effect of corvids (jay Garrulus glandarius) in control territories. However, shrike territories where cuckoo calls were emitted and where the presence of corvids was found were less likely to be inhabited by shrikes. Therefore, territory quality, human presence enhanced by nest predators, is an important factor affecting host–parasite interactions.

Breeding success of passerine birds in the forest steppe of European Russia

In the period from 1985 to 2023, the breeding success of 15 bird species was studied in the Voronezh Nature Reserve (50°21ʹ-52°02ʹ N, 39°21ʹ-39°47ʹ E), where there has been no economic activity for 100 years. The plant cover consists of pine (32.3% of the total area), oak (29.3%), aspen (19.3%), birch (5.7%) and alder (5.2%) forests. 2004 nests were monitored. Low breeding success (25.4-27.9%, determined by the modified Mayfield method) was found in the Blackbird Turdus merula , the Song Thrush T. philomelos , the Finch Fringilla coelebs and the Greenfinch Chloris chloris. From 1.6 to 1.8 fledglings fly out for one breeding attempt. The average level of breeding success (38.7-50.4%) was found in the Common Chiffchaff Phylloscopus collybita , the Red-backed Shrike Lanius collurio , Redwing Turdus iliacus , Eurasian Blackcap Sylvia atricapilla , Garden Warbler S. borin and Hawfinch Coccothraustes coccothraustes . From 2.1 to3.4 fledglings fly out for one breeding attempt. A high level of breeding success (60.6-82.5%) was found in the Great Tit Parus major , the Common Redstart Phoenicurus phoenicurus , the Pied Flycatcher Ficedula hypoleuca , the Collared Flycatcher F. albicollis and the Spotted Flycatcher Muscicapa striata . From 3.7 to 7 fledglings fly out for one breeding attempt. Due to the increased pressure of nest predators, the breeding success of birds in the Voronezh Nature Reserve is often lower than in other areas. The greatest breeding success is typical for birds that place nests in hollows and other shelters. Breeding success is significantly lower in openly nesting species, especially in birds that begin nesting before the leaves bloom on trees and shrubs.

Mantid expansion into North American salt marshes

Abstract Mantids are influential generalist predators in terrestrial systems. Therefore, large mantid species like the European mantid, Mantis religiosa (Linnaeus, 1758), are often used by humans and purposefully introduced as a form of biocontrol, greatly expanding their geographic ranges. However, mantids are rarely recorded in marine systems. In this study, we present an observation of European mantids living in a salt marsh and actively moulting in the vegetation in Elkhorn Slough, in Monterey Bay, California, United States of America. Not only are these European mantids a nonnative species, but every observed individual was a flightless juvenile, meaning they hatched nearby. Although mantids are not usually associated with intertidal ecosystems, there are multiple potential reasons that mantids would be drawn to salt marshes, including food, potential for camouflage, and lower predation pressure. The addition of a generalist predator could produce a complex mix of positive and negative impacts on the marsh itself and, given the importance of marsh systems, these possible effects warrant further study.

Beyond extinction: Uncovering morphological aspects of the last typotherid population (Mesotherium cristatum) and the unexpected body mass decrease

We present a detailed analysis of the craniomandibular and dental remains of Mesotherium cristatum, the quaternary mesotheriid typotherid notoungulate, from Corralito, Santa María Department, Cordoba Province. This population represents the final lineage of Typotheria during middle Pleistocene, Post-Ensenadan Age (>220 ± 13 ka). We compared these new craniomandibular and postcranial samples from Corralito with those from Toscas del Río de La Plata, as well as other localities in the province of Buenos Aires dating to the Ensenadan Age 1.98–0.4 Ma). Our investigation reveals a substantial decline in the size and body mass of the last known population of M. cristatum during the Bonaeran Age period, before its extinction. This occurrence, hitherto unrecorded in any prior South American Land Mammal Age leading up to extinction, might be attributed to the climatic and abiotic changes of the Pleistocene. These changes notably caused a marked reduction in the paleobiogeographical distribution area ofM. cristatum during the Middle Pleistocene. This size and body mass reduction, possibly an outcome of compelled reproductive isolation, is situated against the context of global cooling and heightened predatory pressures. Moreover, our analysis unveiled distinctive taxonomic attributes specific to this taxon, we compare dental size and find a preliminary evidence of an accelerated tooth replacement pattern. Furthermore, we have effectively updated the faunal composition information of the Corralito deposit, elucidating previous biostratigraphic inferences that had led to the belief of Corralito being an Ensenadan Age site. This adjustment impacts the first appearance datum (FAD) of the Neolicaphrium recens proterotheriid litoptern, younger than previously estimated and revised Bonaerian-Lujanian. Finally, this study provides insights into the biological analysis of the iconic species M. cristatum, prevalent in the South American quaternary of the Pampean region. It unreveils new faunal features specific to the Pampean region, shedding light particularly on the lesser-explored western area. These findinngs provide crucial insight into the ever-evolving ecosystem dynamics during the Middle Pleistocene.

A geometric morphometric approach to identify uncomplete snake vertebrae from raptor bird feeding remains

The Hungarian meadow viper (Vipera ursinii rakosiensis) is an endangered subspecies of Vipera ursinii, which faces high predation pressure, partially due to avian species. To create a systematic method for estimating the measure of predation pressure, we developed a geometric morphometric approach to identify both undamaged and damaged vertebrae of snake species found in Hungarian meadow viper habitats from raptor feeding remains. We used linear discriminant analysis with a reference material of vertebrae from identified snake species as training data. We also tested its efficiency by predicting the identification results of different simulation levels based on vertebra completeness. We practiced this method on vertebrae of unknown species of snakes obtained from nests and pellets of short-toed snake eagles (Circaetus gallicus, n = 9), common buzzards (Buteo buteo, n = 14) and Montagu's harriers (Circus pygargus, n = 3). The identification approach showed high accuracy, even in the case of missing landmarks to some extent. We identified vertebrae remnants of Natrix natrix (n = 172, 83.9%), Coronella austriaca (n = 10, 4.9%) and V. u. rakosiensis (n = 23, 11.2%). Both, the reptile specialist C. gallicus and the generalist B. buteo proved to be preying on V. u. rakosiensis, while samples of C. pygargus did not contain any snake remains despite of previous observations of V. ursinii predations. Our approach is applicable for other studies and taxa as well, therefore can be a practical tool for classification of incomplete vertebrae, which is otherwise hardly identifiable. Furthermore, it could be applied to help estimate predation pressure on endangered snake species.

Movement ecology and minimum density estimates of red foxes in wet grassland habitats used by breeding wading birds

The red fox (Vulpes vulpes) is a widely distributed generalist meso-predator implicated in declines of wading bird populations. In the wet grassland habitats where waders breed, wildlife managers work to mitigate fox predation risk to waders during the nesting period through lethal and non-lethal control methods. However, limited knowledge on fox movement ecology in these habitats makes it difficult to design effective management strategies. We used GPS telemetry to understand fox home range size, daily activity and movement patterns, and how these metrics may vary among wet grassland sites with different management. We caught and GPS-tagged 35 foxes in the March–June wader nesting period on two wet grassland sites in central southern England; Britford during 2016/17 and Somerley during 2018/19. We estimated home range areas from location data using local convex hulls, and from these estimates we derived the minimum fox density at each site and year. Daily activity patterns and movement behaviour of each fox were obtained using both telemetry and trail camera data. Mean fox home range area at Britford (0.21 km2, SE = 0.025) was significantly smaller than at Somerley (0.68 km2, SE = 0.067), and estimated minimum densities were around four times higher (Britford = 10.6 foxes/km2, Somerley = 2.4 foxes/km2). Foxes were more active and moved faster during twilight and night hours, but both telemetry and camera data indicate they were also active for one-third of daylight hours. Distances moved per day were variable between foxes but generally smaller at Britford. We also found evidence for dispersal during spring, with movements of up to 19 km per day. Home ranges at both wet grassland sites were smaller than comparable sites elsewhere. These indicated foxes were living at exceptionally high densities at Britford, where there is no fox control, increased food availability and where waders no longer breed. Spatio-temporal movement patterns were closely related to home range metrics, with higher levels of fox activity at Somerley, where home ranges were larger. The movements of itinerant and dispersing foxes during the nesting period suggests that lethal control would need to be very intensive to be effective. The likely anthropogenic food subsidy of fox density at Britford suggests that controlling access to similar food resources would help reduce predation pressure on breeding waders.

Forest management affects ecosystem functioning (predation and herbivory) but not ecosystem constancy: A comparative study across four forest ecosystems around the world

Forest management can affect both the functioning and stability of ecosystems. Constancy and persistence are key factors that contribute to the overall stability of an ecosystem. These factors can be highly variable and change across forest ecosystems. We studied the effects of forest management on the strength of resource–consumer interactions (bird predation and insect herbivory) as important measures of ecosystem functioning, as well as on their constancy in time in four different forested regions globally. Within each region, we selected (i) three heavily managed or plantation forests, and (ii) three urban/peri-urban forests or urban plantings, and paired each of them with pristine/semi-natural forests. Bird predation was estimated using plasticine caterpillars of different colors. Chewer, galler, and miner herbivory on leaves were estimated for 15 plants (shrubs and trees) per study site. Constancy was quantified as the invariability of both predation and herbivory during a period of three (exceptionally two) years. We found no consistent responses of either predation or herbivory to forest management practices across study regions. Bird predation was higher in urban/peri-urban forests than in pristine/semi-natural forests in Patagonian and boreal forest, with intermediate levels of predation in managed or plantation forests. These differences might be explained by the increase of resource availability during the winters and by the higher abundances of generalist predators due to increase of temperatures (i.e., urban heat effect), for those regions where winter temperatures could be a limiting factor. Chewing insect herbivory was lower in urban/peri-urban forests, probably due to the exclusion of certain herbivores in response to warming and the higher predation pressure relative to pristine forests. No differences were found in other types of herbivory, indicating that effects of urbanization are guild-specific. In addition, we consistently found no effects of forest management practices on predation invariability and herbivory, thereby demonstrating the high constancy of ecosystem functioning to different forest management practices across regions. These findings advance our knowledge of the generalized effects of forest management on ecosystem functions and stability by establishing a connection between the ecology and management and conservation of plantations and natural forests.

How antibiotic exposure affect predator-prey interactions by population dynamics in ciliates?

Biodiversity loss resulting from environmental pollution is a global concern. While interspecific interactions are central to ecology, the impact of environmental pollution on predator-prey interactions and its ecological consequences, such as extinction and biodiversity loss, remain unclear. To investigate the effects of antibiotic exposure on predation strength and the resulting ecological consequence, the Didinium-Paramecium was utilized as a predator-prey model and exposed to nitrofurazone or erythromycin, two common pollutants, respectively. Initially, we determined prey population growth dynamics, body size, and predator numerical-functional responses. Subsequently, these above parameters were integrated into a mathematical model of predator-prey predation. Then both the long time-series data and phase portraits obtained through model simulation were used to estimate interaction strength and to predict the outcome of predator-prey coexistence. Our results revealed that exposure to either antibiotic significantly reduced prey population growth parameters (e.g., μmax and K) while increasing individual body size. The combined effects of antibiotic exposure and predation pressure on population growth inhibition or body size promotion were variable, mostly additive, with a few cases of synergy and extremely rare antagonism, depending on antibiotic exposure concentration. As antibiotic exposure concentration increased, the predator rmax generally declined, while functional responses varied depending on specific parameters, implying a decrease in predator-prey interaction strength. Analyses of phase portrait features showed that the population oscillation amplitude decreased with increasing antibiotic exposure concentrations, the cycle length of adjacent peaks increased, and prey extinction occurred earlier. In conclusion, antibiotic exposure reduced both predator and prey fitness, underlying the reason antibiotics reduces the strength of predator-prey interaction. Despite the indirect benefits of prey gain from this, the presence of predators can expedite the process of prey extinction caused by antibiotic exposure.

Keep the ball rolling: sexual differences in conglobation behavior of a terrestrial isopod under different degrees of perceived predation pressure.

Antipredator behaviors are theoretically subjected to a balance by which their display should be minimized when their benefits do not outweigh their costs. Such costs may be not only energetic, but also entail a reduction in the time available for other fitness-enhancing behaviors. However, these behaviors are only beneficial under predation risk. Therefore, antipredator behaviors are predicted to be maximized under strong predation risk. Moreover, predation pressure can differ among individuals according to traits such as sex or body size, if these traits increase vulnerability. Antipredator behaviors are expected to be maximized in individuals whose traits make them more conspicuous to predators. However, how sex, body size and antipredator behaviors interact is not always understood. In this work, I tested the interaction between sex, body size and antipredator behavior in the common pill woodlouse (Armadillidium vulgare), which conglobate (i.e., they roll up their bodies almost conforming a sphere that conceals their appendages) in response to predator attacks. Specifically, I tested whether latency to unroll after a standardized mechanical induction was greater in animals exposed to predator chemical cues (toad feces) than in conspecifics exposed to cues of non-predatory animals (rabbits) or no chemical cues whatsoever (distilled water), incorporating sex and body mass in the analyses. In agreement with my prediction, latency to unroll was greater in individuals exposed to predator chemical cues. In other words, these animals engage in conglobation for longer under perceived predator vicinity. However, this result was only true for males. This sexual dimorphism in antipredator behavior could result from males being under greater predation risk than females, thus having evolved more refined antipredator strategies. Indeed, males of this species are known to actively search for females, which makes them more prone to superficial ground mobility, and likely to being detected by predators. Body size was unrelated to latency to unroll. As a whole, these results support the hypothesis that antipredator behavior is tuned to predator cues in a way consistent with a balance between costs and benefits, which might differ between the sexes.

On Paleozoic platycerate gastropods

The platycerate gastropods Orthonychia yutaroi Ebbestad, sp. nov. (Ordovician, Boda Limestone, Sweden), O. enorme (Silurian, Sweden, Gotland), O. parva (Pennsylvanian, Finis Shale Member, USA), and Orthonychia sp. (Mississippian, Imo Formation, USA) are studied including their protoconch morphology. Orthonychia yutaroi is the oldest known species in Orthonychia. Platycerates contain species with both, openly and tightly coiled protoconchs. This is the first report that tightly coiled protoconchs occur in Orthonychia. This and previously published observations blur the diagnostic difference between orders Cyrtoneritimorpha (openly coiled protoconch) and Cycloneritimorpha (tightly coiled protoconch). We suggest to treat Cyrtoneritimorpha and Cycloneritimorpha as synonyms of Neritimorpha. The monotypic Devonian genus Pragoserpulina is morphological so close to the Orthonychia species reported herein that synonymy of both genera seems to be possible (and thus of the families Pragoserpulinidae and Orthonychiidae). Protoconch morphology and dimensions suggest that the studied platycerate species had planktotrophic larval development. By contrast, two studied Carboniferous euomphaloid species (one with an openly and the other with tightly coiled protoconch) have paucispiral, large protoconchs indicating non-planktotrophic larval development. We assume that openly and tightly coiled protoconchs were present in various Paleozoic gastropod clades and that selection acted against the openly coiled protoconch morphology. It has previously been proposed that increasing predation pressure in the plankton was the reason for the demise of openly coiled protoconchs (Paleozoic plankton revolution). The presence of larval planktotrophy in platycerates excludes the possibility that they belong to extant basal gastropod clades such as Patellogastropoda, Cocculiniformia, and Vetigastropoda. However, a previously proposed close relationship to Neritimorpha is corroborated.

Biomass-based stochastic model for the transfer of polychlorinated biphenyls in a marine food web

Clarifying the state of marine pollution is important for evaluating the health risk to predators in the marine food web such as fishes and mammals. Although previous studies have generally modeled marine pollution targeting a single organism, this study focused on the transfer of marine pollution in terms of ecological network. In this study, a biomass-based stochastic model was constructed for the transfer of 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB153) in a coupled pelagic–benthic system targeting populations of species. Incorporating the populations of species allows for discussions on predation pressure and anthropogenic activities such as fishing. The biomass parameters representing populations of species were set by using published data on the ecosystem in Tokyo Bay, Japan and were represented by probability density distributions to reflect population uncertainty. The PCB153 concentrations computed by the model were then compared with observations for validation. The results showed that the probability density distributions of PCB153 concentrations in marine species had a long tail to the right, which indicated the occurrence probabilities of individual organisms having considerably high contamination levels. A theoretical analysis was performed to quantify the response of species (e.g., fish, plankton, and benthos) to PCB153 accumulation accounting for population uncertainty, which indicated that a reduction in the population of predator species may contribute to the occurrence of high PCB153 concentrations in individual organisms in other species. The obtained probability density distributions were then used to compare the PCB153 human intake through ingesting seafood with the human's acceptable daily intake. The model can quantitatively demonstrate the probability distributions of PCB153 concentrations in marine species and PCB153 intake by humans through seafood, to which more attention should be paid.

DNA metabarcoding complements but does not replace direct observations of penguin predation by corvids

Establishing methods that allow for more focused management of wildlife under predator pressure may increase the efficiency of managing problematic predators. Non‐invasive dietary analysis and identification of conservation‐sensitive prey in the diet of ‘culprit’ predator individuals could help to facilitate this and is worthy of exploration. Recently on Phillip Island, Australia, Little Ravens Corvus mellori have emerged as a prominent predator on the clutches of burrow‐nesting Little Penguins Eudyptula minor. We tested the feasibility of using non‐invasive PCR approaches targeting the penguin mitochondrial 16S rRNA marker gene to establish whether penguin DNA could be detected in raven faecal samples, potentially enabling the identification of culprit ravens missed by extensive field observation. Using a metabarcoding approach, we examined the feasibility of non‐invasively establishing other dietary items via high‐throughput amplicon sequencing. We documented components of raven diet using the universal mitochondrial 16S rRNA, insect‐specific ‘Chiar’ 16S rRNA and plant ITS2. The assemblage of dietary items did not differ with raven culprit status (i.e. a raven previously observed preying upon penguin), sex or date. Penguin was detected in the diet of some individuals classified observationally as non‐culprits. Although some cases may conceivably have been false detections, other explanations include missed depredation events, consumption via scavenging or through secondary consumption (e.g. eating invertebrates that have consumed penguin). While this study found metabarcoding unreliable for unambiguous assigning of raven culprit status, at least as we implemented it, it may hold promise complementing observations if consumption via scavenging can be distinguished from direct depredation.