Burrowing Activity Research Articles

ВЛИЯНИЕ РОЮЩЕЙ ДЕЯТЕЛЬНОСТИ ДИКОГО КАБАНА (SUS SCROFA) НА ГУМУСОВЫЕ ВЕЩЕСТВА В ПОЧВАХ

The burrowing activity of the wild boar (Sus scrofa L.) as one of the types of the habitat-modifying activity of terrestrial mammals has been considered. The typical species and the area of the burrowing sites in winter and summer, as well as the dynamics of humus substances are given. The literature indicates that loosening and mixing the upper soil layers cause changes in the chemical characteristics of the soil, disturb vegetation, and reduce evaporation from the soil surface, which leads to a change in the hydrothermal regime of edaphotop and an increase in both the soil climate continentality and the active layer of edaphotop. Soils of different granulometric composition were considered for comparative characteristic: loams and loamy sands in different geographical zones – steppe (the Dnipropetrovsk region, Ukraine) and taiga (wood sorrel spruce forest, Gryazovets district of the Vologda region, Russia). The steppe zone is dominated by blacktop soils, while podzolic soils prevail in the taiga zone. Although the primary characteristics of the soils were different, the tendency of changing the humus substances content in the soils under the wild boars’ burrowing sites had similar qualities. The nature of the humus substances dynamics depends on the decomposition period of organic substances left on the burrowing sites in the form of wild boar’s excreta and plant food residues. Further mineralization of dead plant remains of damaged roots of tree and shrub vegetation resulting from loosening and trophic activity of wild boar occurs on fellings after spruce indigenous forests. Part of the plant remains on the surface of the loosened soil, and the other part in the soil. As a result of the conducted researches the positive functional impact of the wild boar on any types of biogeocenoses due to its burrowing activity was confirmed.

Influence of dung pats on soil physical quality mediated by earthworms: from dung deposition to decay and beyond

Soil quality determines the ability of soil to deliver ecosystem services and can be inferred from physical, biological and chemical indicators either in isolation or in combination. Earthworms are good soil-quality indicators that contribute to both chemical and physical quality by maintaining soil structure and cycling nutrients. The presence of dung pats can increase earthworm abundance locally and consequently the network of pores that they create through their burrowing activity. Inevitably this affects soil structure and consequently will have a spatially distributed effect on soil physical quality (SPQ). The aim of this field study was to examine the relationship between SPQ and earthworm abundance under dung and non-dung pat areas from deposition to decay and beyond. The present spatial and temporal study compared SPQ indicator (integral air-water energy, AWr) results with earthworm abundance across control and simulated dung pat treatments. Results showed that existing earthworm populations in this grassland were already very large (>500 individuals m–2) and SPQ (AWr) remained in the ‘very good’ category throughout the experiment. Earthworm abundance under dung pats and SPQ exhibited a significant (P = 0.05) temporal trend. In general, the time of decay of the dung pats played a role in increasing earthworm abundance and SPQ. Earthworm abundance and macropore density data formed a similar, ‘hump’-shaped dynamic over time. However, when an earthworm abundance threshold was exceeded (equivalent to about >3000 individuals m–2), the increase of SPQ under dung was attenuated and did increase further only under the control sward with high earthworm abundance. After 11 weeks, for both treatments, AWr under dung pats was capped at 0.83% and AWr under control sward peaked at 1.34%. Future work should focus on (a) further exploration of the threshold where earthworm abundance becomes detrimental for SPQ and (b) using the AWr SPQ indicator within an actual grazed trial which incorporates a gradient of soil degradation.

Effects of microplastics and earthworm burrows on soil macropore water flow within a laboratory soil column setup

AbstractSeveral earlier studies reported that microplastics (MP) accumulated on soil surfaces could be transported into the subsoil and ingested by soil biota, such as earthworms. The present study explores how networks of earthworm burrows and MP (low‐density polyethylene, LDPE) in subsoil affect the soil hydraulic properties and saturated water flow. A repacked and saturated sandy soil column experiment was conducted in an environment‐controlled laboratory with earthworms (anecic, Lumbricus terrestris) inoculated into the soil columns to form networks of macropore. The macropore network parameters (i.e., number, length, volume, diameter, soil saturated conductivity, and tracer breakthrough curves of soil columns) have been determined. The relative arrival times of the tracer mass (i.e. T5%, T25%, and T50%) were determined in order to describe the shapes of the breakthrough curves. The results show that in some breakthrough curves for the treatments with earthworms, there are two peaks. This is an indication that water was flowing faster in the macropores than in the soil matrix. There is a significant correlation between 5% arrival time and the median burrow volume, and the correlation coefficient was .571 (at the level of p < .05). The formation of macropores due to the burrowing activities of earthworms is considered the main cause of nonequilibrium water flow in the present study. The MP did not show any significant effect on the saturated water flow. This may be attribute to the low concentrations of MP used in the present study.

Identifying a surrogate metric for monitoring the population status of a secretive habitat specialist, the heath skinkLiopholis multiscutata,in south‐eastern Australia

AbstractThreatened species that exist in small isolated populations are vulnerable to extinction processes, so effectively monitoring the trajectory of such populations will help determine the most appropriate management actions to combat extinction threats. In this study, we aimed to track the population status of the fossorial heath skinkLiopholis multiscutatathat is listed as threatened in Victoria, south‐eastern Australia, and exists there as a few small and highly disjunct populations, by using an appropriate surrogate population monitoring metric. This secretive lizard is a habitat specialist, is highly localised in Victoria and lives in warrens in semi‐arid heathland or mallee on large dunes. Survey data, which included every warren and their constituent burrows, as well as an assessment of whether each burrow was ‘active’, were collected for the four known Victorian populations in 2007 and annually during 2014–2018 inclusive. We compared five population indices per monitoring site: number of active warrens (NAW), number of active burrows (NAB), population area for 80% of active warrens (PA80), percentage of warrens that were active (PAW) and average number of active burrows per active warren. The heath skink currently occurs in small populations (8–46 active warrens) and these populations have typically declined over recent years. NAW was the most robust metric; NAB and PA80 did not reveal strong temporal trends. PAW indicated that inactive warrens and burrows persist less than a year and hence may provide information about recent (within months) population changes. It is imperative to establish a material link between the effective monitoring of small, vulnerable populations and the implementation of management actions that benefit such populations. Here, NAW could be used as a long‐term monitoring tool to provide an estimate of the minimum population size of the heath skink at a site. Its use would also ensure continuity in monitoring approaches for the Victorian populations.

Daily and Seasonal Feeding Activity of the Greater Mole-Rat (Spalax microphtalmus, Rodentia, Spalacidae)

The activity of the greater mole-rat was studied using a new technique. New data have been obtained on the characteristics of the daily and seasonal underground life of mole-rats in an isolated population in Mordovia. Polyphase daily activity is most pronounced in the spring and early fall periods. In spring, the maximum activity (about 20% of all daily registrations in separate hours) is confined to the periods from 8:00 to 9:00 a.m. and from 3:00 to 4:00 p.m. The peak of activity in the early fall was recorded from 9:00 to 10:00 a.m. At night, the activity of animals in different seasons was stably low. The burrowing activity, as a rule, began after midnight and stopped in the morning before 5:00 a.m. The maximum duration of the dormancy period in the evening in summer months was five hours. Statistically significant differences were obtained for the average number of passages of mole-rats in the burrow per day for different months using the Mann‒Whitney criterion (p < 0.05).

Modified live traps increase capture success of semifossorial voles in Alpine meadows

Abstract Live-trapping of rodents is facilitated by their thigmotaxis (i.e. the tendency to walk along linear structures of the habitat). However, in open habitats, such as meadows and prairies, where linear structures (e.g. rocks and fallen branches) are generally absent and where densities are likely to be low, capturing rodents is often very demanding or ineffective. This applies especially to semifossorial small mammals. Therefore, we developed a technique to increase the capture success of these rodents in Alpine meadows. We applied a box in Tetrapak® with the perforated floor at the opening of Sherman traps. Semifossorial voles (Microtus spp.), leaving their burrows, would remain in a confined status, in the dark within the Tetrapak®, being forced to enter the trap or to go back in the tunnel. Sherman traps modified with Tetrapak® were positioned immediately upon active burrows, alternating with the same number of unmodified traps. Then, we compared the number of captures with and without this modification. Two trapping sessions were carried out, for 3 days/site each, in eight sites (totally 2784 trap-days). Overall, 55 semifossorial voles were trapped; 41 (74.6%) were caught in modified traps, showing that they increase the capture success of semifossorial voles in Alpine meadows.

Behavioral responses of three venerid bivalves to fluctuating salinity stress

The link between the behavior of organisms living within the sediment and benthic-pelagic coupling is critical to our interpretation of impacts of physiological stress. The rapidity with which organisms respond to a stress and recover once a stress is removed impacts the cascade of secondary effects that result from such behavioral changes. Such behavioral responses, although critical to our understanding, are difficult to quantify, particularly for organisms such as bivalves that inhabit sediments, the most common spatial habitat on Earth. Sublethal responses to fluctuating stressors such as salinity are rarely quantified in terms of activity. Here we do so using a combination of direct observations and pressure sensors, which allow us to record burrowing and other hydraulic activities. Based on our field observations and the literature, we predicted that there would be a breakpoint in behavior between salinities of 15 and 20 and that below this breakpoint the animals would significantly reduce activities including burrowing and feeding. The data presented support this prediction; burrowing was reduced in all three species at salinities at or below 15 as were fecal deposition and appearance of siphons above the sediment surface. These data are consistent with the prediction that under conditions of large fluctuations in salinity the magnitude of the link to primary productivity and nutrient availability from the benthos will be significantly reduced.

Effect of burrowing crabs on retention and accumulation of soil carbon and nitrogen in an intertidal salt marsh

Ecosystem engineers that affect other organisms by creating, modifying, maintaining or destroying habitats have received widespread attention. Understanding natural ecosystems and the way in which ecosystem engineers shape the environment is important to ecological restoration based on key ecosystem processes. Increasing studies has shown that crabs in intertidal salt marsh can act as ecosystem engineers, affecting the geomorphological processes and spatial heterogeneity of tidal flat. In this study, field investigations and manipulative experiments were conducted to explore how crab burrowing activity affects intertidal microtopography and soil carbon and nitrogen in the intertidal salt marshes. The results showed that crab burrowing activity is one of the key factors influencing concave-convex microtopography, which could intercept plant detritus and subsequently influencing the retention and accumulation of soil carbon and nitrogen. When compared to areas of flat microtopography with few or no crab burrows, soil organic carbon content (SOC), soil inorganic carbon content (SIC), total carbon content (TC), and total nitrogen content (TN) in adjacent areas of concave-convex microtopography with high density crab burrows were all significantly higher. Artificial simulation of ecosystem engineering processes could also change the geomorphological features of tidal flats and improve the retention and accumulation of soil carbon and nitrogen, which could also attract more crabs to burrow and settle down, then generate and maintain the concave-convex microtopography. Taken together, the results of this study provide scientific and effective implication and guidance for the restoration of coastal salt marshes.

Dynamics of greenhouse gas emission induced by different burrowing activities of fossorial vertebrates in the Qinghai-Tibetan Plateau alpine meadow ecosystem.

Plateau zokor (Myospalax baileyi) and plateau pika (Ochotona curzoniae) are endemic fossorial vertebrates in the Qinghai-Tibetan Plateau alpine meadow ecosystem. Their different burrowing activities together transform soil structure and then significantly change the landscape of meadow ecosystem. However, how their burrowing activities impact greenhouse gas (GHG) emissions and the pattern of GHG emissions between different types of tunnel burrowing still remain obscure. In this study, we conducted in situ measurements quantitatively investigating the impacts of the different burrowing activities of zokors and pikas on three main GHG CO2, CH4, and N2O from an alpine meadow ecosystem in southeastern Qinghai-Tibetan Plateau. Our results showed that zokor hummocks and pika burrows were sources of CO2 and N2O and sinks of CH4. Zokors burrowing increased N2O in the atmosphere, decreased CO2, and enhanced CH4 absorbing, while pikas burrowing increased N2O in the atmosphere and enhanced CH4 absorbing. Considering the controversial role of fossorial vertebrates in Qinghai-Tibetan Plateau, this study also shed lights on effective management of animal activities with the aim of stabilizing or increasing ecosystem carbon sequestration.

Mapping out bare-nosed wombat (Vombatus ursinus) burrows with the use of a drone

BackgroundWombats are large, nocturnal herbivores that build burrows in a variety of habitats, including grassland communities, and can come into conflict with people. Counting the number of active burrows provides information on the local distribution and abundance of wombats and could prove to be an important management tool to monitor population numbers over time. We compared traditional ground surveys and a new method employing drones, to determine if drones could be used to effectively identify and monitor bare-nosed wombat burrows.ResultsWe surveyed burrows using both methods in eight 5-ha transects in grassland, that was interspersed with patches of tussock grassland. Ground surveys were conducted by systematically walking transects and searching for burrows. Drone surveys involved programming flights over transects to capture multiple images, from which an orthomosaic image of each transect was produced. These were subsequently viewed using ArcMap to detect burrows. A total of 204 individual burrows were recorded by drone and/or ground survey methods. In grassland, the methods were equally effective in terms of the numbers of burrows detected in transects. In the smaller areas of tussock grassland, ground surveys detected significantly more burrows, because burrow openings were obscured in orthomosaic images by overhanging grasses. There was agreement between the methods as to whether burrows were potentially active or inactive for most burrows in both vegetation communities. However, image interpretation tended to classify grassland burrows as potentially active. Overall time taken to conduct surveys was similar for both methods, but ground surveys utilised three observers and more time in the field.ConclusionsDrones provide an effective means to survey bare-nosed wombat burrows that are visible from the air, particularly in areas not accessible to observers and vehicles. Furthermore, drones provide alternative options for monitoring burrows at the landscape level, and for monitoring wombat populations based on observable changes in burrow appearance over time.

Benefits of non-invasive methods compared to telemetry for distress analysis in a murine model of pancreatic cancer

Prospective severity assessment is legally required in many countries to ensure high-quality research along with high welfare standards for laboratory animals. Mice and rats, the most common laboratory species, are prey animals that usually suppress signs of pain and suffering. Therefore, highly sensitive readout parameters are necessary to adequately quantify distress. The present study compared the performance of different non-invasive methods in determining animal distress, such as measuring body weight, distress score, faecal corticosterone metabolites, burrowing, and nesting behaviour, with continuous monitoring of heart rate, body temperature and activity by telemetry. The distress caused by two surgical interventions was compared and the burden caused by tumour growth was described. Transmitter implantation caused higher distress than laparotomy plus carcinoma cell injection into the pancreas. Surprisingly, no significant increase in distress was observed during tumour growth. The receiver operating characteristic curve analysis revealed that some non-invasive distress-parameters, i.e., distress-score and burrowing activity, exhibited slightly better performance to quantify distress than the most suitable parameters measured by telemetry. Due to the high burden caused by the implantation of the telemetric device, the use of non-invasive methods to assess distress in laboratory animals after surgical interventions should be favoured in future studies.

Verification of ageing methods for the burrowing shrimp, Neotrypaea californiensis, using extractable lipofuscin and gastric mill cuticular features

AbstractThe burrowing shrimp Neotrypaea californiensis is an important ecosystem engineer that inhabits estuaries along the US Pacific Northwest coast. This species plays an important role in the estuarine ecosystem but negatively impacts oyster aquaculture through its burrowing activities. Development of population models for burrowing shrimp management requires more detailed life history information and accurate estimates of age. Ageing studies have been limited for crustaceans because it is generally believed that they do not retain structures with annual deposits commonly used to age other marine organisms, when they moult their exoskeletons. A mesocosm growth experiment and field surveys were combined to compare the performance of two ageing techniques, quantification of autofluorescent lipofuscin and gastric mill ossicular lamellae, for estimating age in N. californiensis. Animals of known age were grown in outdoor mesocosms and sampled regularly to correlate age metrics with body size and true age. Lipofuscin concentration increased with time across multiple cohorts at the rate of 1.430 ± 0.060 ng µg−1 year−1. Lamellae counts also increased with time (4.922 ± 0.337 lamellae year−1). While age estimates based on lipofuscin concentration and lamellae counts generally agreed, carapace size did not correlate to either age metric. Lamellae counts from field collections suggest they are added sequentially with age but the relationship can vary by location. When used together, the application of both techniques may provide robust estimates of crustacean age especially when size-based measurements are imprecise.

Effects of burrowing mud lobsters (Thalassina anomala Herbst 1804) on soil macro- and micronutrients in a Malaysian mangrove

The mud lobster, genus Thalassina is the least studied taxon compared to other mud crabs within Thalassinidae family. Burrowing thalassinid populations are considered to be an effective means of bioturbation, affecting the macro- and micronutrient properties in the substrates they occur in through nutrient redistribution. This study assessed the combined effects of fresh mud excavation and old mud deposition on soil turnover and vertical marconutrients including NH4–N, NO3–N, P, K, S, Na, Ca, and Mg and micronutrients including Fe, Cu, Zn and Mn distributions in a Malaysian mangrove, Sibuti Wildlife Sanctuary, Sarawak. The mud lobster Thalassina anomala (Decapoda: Thalassinidae) inhabits and builds mounds both seafront and inland mangroves. Their burrowing activities increased NH4–N, NO3–N, P, and Na concentrations in fresh mud and Fe, Cu and Zn concentrations in the old mud. The nutrient concentrations in excavated soils were greatly affected by habitat type, and depth. Burrowing processes can effectively turnover subsurface soil to the surface, which acidifies strongly upon oxidation. Higher S content in mud lobster soil together with low pH revealed mud lobsters play a strong role in the development of acidity in the study areas. These processes could stimulate formation of acid sulphate soil in the mangroves. Therefore, bioturbation not only affects soil physical and chemical properties but also ecological functions of mangroves, and needs proper attention during restoration and reclamation programs of mangrove forests.

Impoverished soil supports more plateau pika through lowered diversity of plant functional traits in Tibetan alpine meadows

Frequent outbreaks of plateau pika (Ochotona curzoniae) have become a major challenge for the sustainability of Tibetan rangeland, although top-down control has been widely employed since the 1960s over the plateau. Based on studies on plant trait-mediated soil-plant-herbivore relations, we hypothesized that impoverished soil was a consequence of rangeland degradation as well as a cause of increasing pika numbers through lowered functional trait diversity (FD) of the plant community that provides advantages for pika fitness. At three sites of alpine meadows on the eastern Tibetan Plateau, we counted active burrows of pika in 27 plots (i.e., 9 plots per site) distributed along a gradient of soil fertility. For every plant species within each plot, we measured five functional traits (e.g., mature height, SLA: specific leaf area, LDMC: leaf dry matter content, and leaf N and P: leaf nitrogen and phosphorus concentrations), indicating plant performance in response to changing soil fertility and impacting the fitness of pika. We employed Bayesian regression, structural equation modeling and network analyses to assess causal relations from soil fertility to FD and burrow density. The results show i) there was no significant difference in burrow density between three sites; spatial variation among plots in terms of soil fertility, plant species diversity and FD accounted for 57%–72%, 26%–41% and 59%–73%, respectively, of the variation in burrow density; ii) the burrow density was associated positively with soil moisture and organic matter, plant coverage, forb abundance and FD of leaf P, but negatively with soil nutrients, plant species diversity and FD for SLA, height and leaf N; and iii) deficiency of soil P potentially resulted in an increase in pika density, likely through lowered FD of SLA and height, with other soil factors and FD of leaf nutrients indirectly associated with burrow density. Our study suggested that under the joint effect of intensive grazing by livestock and output of livestock products from region, deficiency of soil P potentially increased pika density, likely by supporting more and diverse food resources while decreasing the risk of being preyed upon. Control of pika outbreak should pay more attention to bottom-up restoration of degraded soil and vegetation via traditional rotational grazing and promotion of recycling and compensation of lost soil P and plant trait diversity.

Effect of low frequency electromagnetic field on the behavior and bioenergetics of the polychaete Hediste diversicolor

The aim of the present study was to determine the effect of an electromagnetic field (EMF) of value typically recorded in the vicinity of submarine cables (50 Hz, 1 mT) on the behavior and bioenergetics of the polychaete Hediste diversicolor. No avoidance or attraction behavior to EMF was shown, but the burrowing activity of H. diversicolor was enhanced in EMF treatment, indicating a stimulating effect on bioturbation potential. The polychaete maintained a positive energy balance and high amount (85% of assimilated energy) of energy available for individual production (scope for growth) after exposure to EMF. Food consumption and respiration rates were not affected but ammonia excretion rate was significantly reduced in EMF-exposed animals compared to the control conditions (geomagnetic field). The mechanisms behind this effect remain, however, unclear. This is the first study demonstrating the effects of environmentally realistic EMF value on the behavior and physiology of marine invertebrates, thus there is a need for more research.

Spatial pattern of pika holes and their effects on vegetation coverage on the Tibetan Plateau: An analysis using unmanned aerial vehicle imagery

Abstract The pika (Ochotona curzoniae) hole is an important landscape feature in the Tibetan Plateau (TP) grasslands, and it indicates grassland degradation levels due to the destruction caused by pika burrowing activities on grasslands. However, no studies have ever explored landscape patterns of pika holes and their effects on adjacent vegetation coverage. Taking meadow grasslands in Northern Tibet as an example, this study gathered unmanned aerial vehicle (UAV) images and explored landscape patterns of pika holes and their effects on grass coverage in the surroundings. The performances of two classification methods, including the decision tree classification based on Fully Constrained Least Squares (FDC) and the object-oriented classification (OBC) were compared in recognizing sizes and shapes of pika holes. The results showed that: (1) The object-oriented classification exhibits higher classification accuracy in identifying pika holes. (2) The average size of pika holes in the study area is 0.01 m2 and they exhibit clustered distribution patterns. The average distance between any two nearest pika hole patches is 0.79 m. (3) It presents a significant quadratic relationship between the number of pika holes and grass coverage. (4) The average effective distance of pika holes on the surrounding grass coverage is 20 cm. The findings of this study can provide guidelines for pika control and improve grassland management on the TP.

BIVALVES ON THE MOVE: THE INTERPLAY OF EXTRINSIC AND INTRINSIC FACTORS ON THE MORPHOLOGY OF THE TRACE FOSSIL PROTOVIRGULARIA

ABSTRACTTide-influenced deposits of the Pennsylvanian Rock Lake Shale Member, Stanton Formation, Missouri and Kansas (U.S.A.), contain well-preserved evidence of the burrowing activities of protobranch bivalves, including locomotion (Protovirgularia) and locomotion-resting (Protovirgularia-Lockeia) trace fossils. Protovirgularia shows three distinct morphotypes, the morphological variability of which was controlled by external factors such as substrate conditions, toponomy, and undertrack deficiency. Extreme morphological modifications of Protovirgularia and/or Lockeia, represented by irregular bilobate structures, probably result from erosion and subsequent partial passive filling of the original biogenic structures. In addition, very well-preserved trace fossils showing intergradation of a fan-shaped cluster of ridges with Protovirgularia-Lockeia structures are interpreted as a compound biogenic structure that represents locomotion, resting, and feeding activities of burrowing protobranch bivalves.

The zoogeomorphology of case‐building caddisfly: Quantifying sediment use

AbstractCaddisfly (Trichoptera) larvae are an abundant and widespread aquatic insect group characterized by the construction of silk structures, including nets and cases. Case‐building caddisfly have the potential to modify the sorting and mobility of sand and fine gravel via: (1) case construction, resulting in altered sediment properties; (2) transporting sediment incorporated into cases over the river bed; and (3) changing the structure of river beds via burrowing activity. To investigate these mechanisms, it is necessary to understand the mass, size distribution and spatial variability of sediment use by case‐building caddisfly larvae.We quantified the mineral sediment used by individuals and communities of case‐building caddisfly in 27 samples, from three sites on a gravel‐bed stream. The mass and size distribution of sediment in individual cases varied between taxa (mass = 0.001–0.83 g, D50 = 0.17–4 mm). The mean mass of sediment used by the caddisfly community was 38 g m−2 and varied locally. Sediment use was predominantly coarse sand (D50 = 1 mm). 64% of sediment use was attributable to Agapetus fuscipes (Glossosomatidae).Due to within‐species variability in case mass, the abundance of most taxa, including A. fuscipes, was only weakly associated with the mass of sediment used by this species, at the river scale. Whilst the caddisfly community used a small percentage of the total sediment available (average 2.99% of the 1–1.4 mm size fraction), A. fuscipes used more fine sediment in their cases at sites where it was more available. Despite variability in local habitat, all sites supported diverse case‐building caddisfly communities utilizing mineral sediment. Consequently, geomorphological effects of case‐building caddisfly are potentially widespread. The results provide novel insights into the specific grain sizes and quantities of fine sediment used by caddisfly larvae, which represents an important step towards understanding their zoogeomorphic activities. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley &amp; Sons Ltd.

Sulcolithos variabilis igen. et isp. nov.: grooves on firm and hard bedding surfaces

The trace fossil Sulcolithos variabilis igen. et isp. nov. is described from the Middle Triassic (Ladinian) Muschelkalk Group of Germany. The groove-like structures occur on the surface of limestone beds that provided firm to hard substrate to the burrowing and/or boring organisms. The grooves have an elongate, straight or curved course and can be compound with subsurface burrow systems of Balanoglossites. Similar trace fossils have been reported from Late Ediacaran to Holocene deposits, and seem to be prevalent in Ordovician, Triassic and Jurassic time. Based on indirect evidence (e.g. morphology, interrelationship with Balanoglossites, substrate property), S. variabilis is attributed to the combined burrowing and boring activity of polychaetes. This interpretation is supported by direct evidence, such as the occurrence of exceptionally preserved polychaete remains in the traces, both in the Triassic material from Germany and the Ordovician specimens from Anticosti Island, Canada. However, morphologically similar traces in soft and firm substrate can also be produced by other organisms (e.g. bivalves) and represent behavioural convergence.

Proteolytic and Opportunistic Breaching of the Basement Membrane Zone by Immune Cells during Tumor Initiation

SummaryCancer-related inflammation impacts significantly on cancer development and progression. From early stages, neutrophils and macrophages are drawn to pre-neoplastic cells in the epidermis, but before directly interacting, they must first breach the underlying extracellular matrix barrier layer that includes the basement membrane. Using several different skin cancer models and a collagen I-GFP transgenic zebrafish line, we have undertaken correlative light and electron microscopy (CLEM) to capture the moments when immune cells traverse the basement membrane. We show evidence both for active proteolytic burrowing and for the opportunistic use of pre-existing weak spots in the matrix layer. We show that these small holes, as well as much larger, cancer cell-generated or wound-triggered gaps in the matrix barrier, provide portals for immune cells to access cancer cells in the epidermis and thus are rate limiting in cancer progression.