Burrowing Activity Research Articles

Microplastic from beach sediment to tissue: a case study on burrowing crab Dotilla blanfordi.

Microplastics (MPs) are pervasive pollutants in the marine environment, exhibiting persistence in coastal sediment over extended periods. However, the mechanism of their uptake by marine organisms and distribution in habitat is less understood. The objective of the present study was to investigate the presence of MP contamination in burrow sediment, feeding pellets, and tissue of Dotilla blanfordi in the Gulf of Kachchh, Gujarat State. A total of 500 g of burrow sediment, 100 g of feeding pellets, and body tissue of 10 resident D. blanfordi were pooled as one replica. Such seven replicas from each site were analyzed for MP extraction from three sites, including Asharmata, Mandvi, and Serena, located in the Gulf of Kachchh. The standard protocol was used during the analysis of the collected samples in order to isolate MPs. The abundance of MP was found higher in burrow sediment, feeding pellets and tissue of D. blanfordi at study site Mandvi, followed by Serena and Asharmata. The abundance of MP was found higher in D. blanfordi tissue, followed by burrow sediment and feeding pellet. A significant variation was observed in MP abundance among burrow sediment, feeding pellets, and tissue. MPs with various shapes (fiber, film, and fragment), sizes (1-2, 2-3, 3-4, and 4-5 mm), and colors (blue, green, black, pink, purple, red transparent) were recorded from all the study sites. Polyurethane and polyvinyl chloride were recognized as the chemical profile of the extracted MPs. The current investigation revealed greater accumulation of MPs in D. blanfordi's tissues compared to sediment and pellets, suggesting a risk of MP contamination in marine benthic fauna with a greater rate of bioaccumulation. D. blanfordi plays a significant role as a structuring agent for MP distribution in the intertidal flat through burrowing activity.

Non-invasive (georadar) investigation of groundhog (Marmota monax) burrows, Pennsylvania, USA

Zoogenic impact plays a critical role in stream processes, especially bank stability and resulting channel dynamics. This study focuses on bioturbation by groundhogs (Marmota monax) along the riparian zone of Mill Creek (Bucks County, Pennsylvania, USA). Several complexes comprising at least 32 active burrows (average diameter: 25.9 cm) were geolocated, with morphometric measurements obtained at selected sites. Two networks were imaged using high-frequency 800 MHz ground-penetrating radar (GPR) and included: 1) a grid of parallel 3-m-long transects on the south bank, and 2) an 11-m-long profile on the north bank. Post-processed electromagnetic signal traces (A-scans) comprising 2D radargrams (B-scans) revealed voids as reverse-polarity anomalies (hollow inclined shafts and tunnels), allowing for a general assessment of burrow depth and orientation. At the southern cutbank site, a large burrow had an entrance diameter of 0.3 m and a westerly dip. A sloping tunnel section was detected at ~0.5 m depth, based on the geometry of point-source (transverse) hyperbolic diffractions corresponding to the roof and a floor ‘pull-up’. The second locality traversed three open burrow entrances adjacent to large tree roots. This survey along a tributary channel shows multiple hyperbolics below adjacent openings, with the latter showing the characteristic signal ‘breakout’. GPR data show hyperbolic signatures ~0.3–0.4 m below the ground surface. Along this transect, burrowing activity appears to increase with proximity to the northern bank of Mill Creek. An example of a depth slice (bedding-plane view) from a nearby riverbank demonstrates the potential for 3D visualization (C-scans) of burrow networks using a grid of closely spaced GPR profiles. Groundhog burrows constrain maximum long-term level of the groundwater table and serve as important zoogeomorphic structures in diverse ecotones, including developed landscapes. Abundant evidence of bank slumping, incision, and treefall suggests that burrowing activity likely weakens root systems and enhances groundwater flow, thereby initiating or accelerating geomorphic cascades leading to slope failure.

Appropriateness of introducing earthworms into sustainable agriculture from the perspective of soil carbon emissions

Sustainable agriculture, as an effective method for reducing the risk of soil degradation, is often accompanied by increases in soil fauna populations. However, the effects of soil fauna (such as earthworms) bioturbation on soil carbon (C) emissions remain unclear. We conducted a 31-day incubation experiment to measure the effects of adding straw (1 g) and anecic earthworms on the burrowing characteristics and C emissions using two soils collected from the plow layer and plow pan layers. We also explored the effects of the soil C source (soil organic C (SOC) and exogenous organic matter (OM) inputs) on the soil C emissions induced in the presence of earthworms by meta-analysis. The incubation experiment showed that earthworms increased the loss rate of surface straw (49.4–96.8%; p < 0.05) and the soil C emissions (160.5–455.4%; p < 0.01). Earthworms significantly increased the macroporosity (p < 0.001) and macropore size (p = 0.016), but decreased the macropore number in the plow layer soil. While, only the soil macropore size increased significantly (p = 0.025) under earthworm addition in the plow pan soil. Structural equation models indicated that straw directly influenced the soil macropore size (p = 0.022) and C emissions (p = 0.039) in the plow layer soil, but had no effects on the soil macropore characteristics and C emissions (p > 0.05) in the plow pan soil. Earthworms indirectly affected soil C emissions through effects on the soil macropore size (p < 0.05). Meta-analysis indicated that although earthworms increased C emissions by 51.7% and 25.0% without and with OM inputs (p > 0.224), respectively, the earthworm-induced effects on soil C emissions were not related to OM inputs (p = 0.337). Soil C emissions induced by earthworms decreased as the SOC content increased (from 45.1% to 2.6%), but these effects were not significant at any SOC level (p > 0.154). These findings indicate that the effects of anecic earthworms on soil C emissions can be reflected by the earthworm burrowing characteristics and earthworms increased the soil C emissions in the short term (incubation experiment), but their effects on soil C emissions eventually became non-significant due to reduced anecic-earthworm burrowing activities (most burrows are permanent or semi-permanent) and SOC content increase in the long term (meta-analysis). We therefore recommend that earthworm regulation together with OM inputs could be considered in sustainable agriculture.

Ptychoplasma and associated ichnotaxa of bivalve burrowing activity in Kuldhar Member of Jaisalmer Formation, Jaisalmer Basin, western India

Ptychoplasma and associated ichnotaxa of bivalve burrowing activity in Kuldhar Member of Jaisalmer Formation, Jaisalmer Basin, western India

Housework or vigilance? Bilbies alter their burrowing activity under threat of predation by feral cats.

Behavioral adjustments to predation risk not only impose costs on prey species themselves but can also have cascading impacts on whole ecosystems. The greater bilby (Macrotis lagotis) is an important ecosystem engineer, modifying the physical environment through their digging activity, and supporting a diverse range of sympatric species that use its burrows for refuge and food resources. The bilby has experienced a severe decline over the last 200 years, and the species is now restricted to ~20% of its former distribution. Introduced predators, such as the feral cat (Felis catus), have contributed to this decline. We used camera traps to monitor bilby burrows at four sites in Western Australia, where bilbies were exposed to varying levels of cat predation threat. We investigated the impact of feral cats on bilby behavior at burrows, particularly during highly vulnerable periods when they dig and clear away soil or debris from the burrow entrance as they perform burrow maintenance. There was little evidence that bilbies avoided burrows that were visited by a feral cat; however, bilbies reduced the time spent performing burrow maintenance in the days following a cat visit (P = 0.010). We found the risk posed to bilbies varied over time, with twice the cat activity around full moon compared with dark nights. Given bilby burrows are an important resource in Australian ecosystems, predation by feral cats and the indirect impact of cats on bilby behavior may have substantial ecosystem function implications.

Effect of bioturbation of the mitten crab on distribution of tire wear particles and their combined effect on sediment ecosystem

Tire wear particles (TWPs) are a major source of environmental microplastic pollution which gradually settle and accumulate in sediments after entering the aquatic environment, which can affect the behaviors of benthic organisms. Bioturbation of benthic species could affect the fate, impacts and potential risks of TWPs by altering the properties and structure of sediments. Therefore, in this study, the effect of TWPs on the burrowing activity of Chinese mitten crab (Eriocheir sinensis) was investigated. In addition, the effects of crab bioturbation on the distribution of TWPs and their additives were studied. The combined effects of TWPs and crab bioturbation on the microbial communities in the sediments were also explored. The results of this study showed that both TWPs and the leachate significantly inhibited the burrowing activity of crabs. TWPs in the surface layer of sediments were re-distributed by crab bioturbation and enriched mainly in the sediments near the burrow walls. Meanwhile, the heavy metals (i.e., Zn, Ca, Mg, Ba and Al) used as additives during the tire production in the burrow walls significantly increased as the accumulation of TWPs near burrow walls. In this study, TWP exposure decreased the bacterial diversity and abundance, as well as the functional genes related to carbon and nitrogen cycling process, but crab bioturbation increased them in the sediments of burrow walls by constructing a unique habitat. However, after TWPs entering into burrows, they were significantly decreased in the sediments near the burrow walls like the effects of TWPs, suggesting the negative effects of TWPs could play a dominant role in this combined system. Overall, this study is important for evaluating the distribution and effects of TWP pollution in the sediment ecosystem under biological factors such as bioturbation.

Soil structure shifts with earthworms under different organic fertilization in salt‐affected soils

AbstractEarthworm incubation combined with organic fertilization is promoted as an amended measure to improve soil properties in the ecological restoration of various degraded soils. However, the impacts of earthworms on the soil aggregate size under different organic fertilization in salt‐affected soils have not yet been fully revealed. This hinders our ability to develop policies by which to alleviate soil salinization. In this study, under mesocosm experiments, we investigate the effects of earthworm (Aporrectodea trapezoides) and organic fertilization on the soil aggregate size after 16 weeks of incubation. The soil treated with clover residues showed lower earthworm survival rates and biomass compared to that treated with sheep manure. However, the soil macropores and large macroaggregate were higher in the soils treated with clover residue when earthworms were present. In addition, earthworm burrowing activities form pathways toward food patches improve the characteristics of soil macropores, and the properties of the residue itself play a decisive role. Moreover, whether earthworms are present or not significantly influences the soil macroporosity, macropore number, and soil electrical conductivity. This demonstrates that earthworms exhibit a key feature of soil physical functioning in salt‐affected soil. In conclusion, we propose that the application of earthworms with organic residues in salt‐affected soils is a priority in producing and maintaining favorable soil structure.

Scolicia, ichnotaxonomic practices, and the limits of behavioural convergence

Many studies convincingly documented the diagnostic morphology of Scolicia, establishing a functional link with the burrowing activities of heart urchins, common components of the marine mobile faunas that emerged during the Mesozoic Marine Revolution. However, this ichnotaxon has been repeatedly mentioned in both continental successions and Paleozoic marine strata, even though its diagnostic characteristics were absent. This approach may reflect the implicit belief that behavioural convergence is rampant in the ichnologic record and can be uncritically adopted in almost all cases. We underscore the importance of a definition of Scolicia that is based on diagnostic morphologic features and supported by a solid analysis from the perspective of function and mode of construction. This view of Scolicia highlights its value in paleoenvironmental reconstructions and its significance to unravel macroevolutionary trends. Attribution to an ichnotaxon should involve understanding of morphologic features in terms of its mode of production rather than the mere observation of superficial similarities.

Earthworms reduce nutrient loss from loess soil slopes under simulated rain

Burrowing, feeding, and casting activities of earthworms affect nutrient cycling and hydrological processes that take place in sloping lands. However, the effects exerted by earthworms on nutrient losses associated with runoff and sediment during rain remains unclear, particularly in the Loess Plateau, where soil erosion and nutrient loss have led to severe environmental issues. In this study, our purpose was to quantify the effects exerted by the anecic earthworm species, Metaphire guillelmi, on nutrient loss via runoff and erosion in loess soil slopes. Six artificial grass slopes (mesocosms, 15°), comprising three with earthworms (100 individuals m−2) for 28 days, and three without earthworms, were subjected to simulated rain (90 mm h−1) for 60 min. Our results indicated that earthworms had (i) increased the content of NO3–-N from 8.1 to 151.8 mg kg−1 and OP from 51.0 to 71.8 mg kg−1, but decreased the content of OC from 6.6 to 5.2 g kg−1, TN from 0.76 to 0.62 g kg−1, TP from 0.73 to 0.68 g kg−1 and NH4+-N from 3.7 to 2.4 mg kg−1 at surface 2 cm soil; (ii) increased water-stable macroaggregates from 45.1 to 48.3% and soil saturated water conductivity from 0.07 to 0.28 mm min−1, and (iii) greatly reduced the cumulative runoff from 65.7 to 15.3 mm and sediment occurance from 0.44 to 0.16 kg m−2 on slopes. Consequently, earthworm activities decreased runoff-associated nutrients (decreased NH4+-N from 19.5 to 2.8 mg m−2, NO3–-N from 108.2 to 26.2 mg m−2, and SP from 2.2 to 0.1 mg m−2) loss by 75.8–96.2%, and sediment-bound nutrient (decreased OC from 2.4 to 0.8 g m−2, TN from 0.3 to 0.1 g m−2, TP from 0.3 to 0.1 g m−2) loss by 63.8–68.5%. Hierarchical partitioning and variation partitioning analyses showed that runoff and sediment yields and their interaction with the soil physical characteristics were the dominant pathways via which earthworms regulated nutrient loss during rainfall events. This study highlights the importance of soil fauna in regulating erosion and nutrient loss in the Loess Plateau, and indicates that these factors should be considered in future water and soil conservation management.

Mammalian bioturbation amplifies rates of both hillslope sediment erosion and accumulation along the Chilean climate gradient

Abstract. Animal burrowing activity affects soil texture, bulk density, soil water content, and redistribution of nutrients. All of these parameters in turn influence sediment redistribution, which shapes the earth's surface. Hence it is important to include bioturbation into hillslope sediment transport models. However, the inclusion of burrowing animals into hillslope-wide models has thus far been limited and has largely omitted vertebrate bioturbators, which can be major agents of bioturbation, especially in drier areas. Here, we included vertebrate bioturbator burrows into a semi-empirical Morgan–Morgan–Finney soil erosion model to allow a general approach to the assessment of the impacts of bioturbation on sediment redistribution within four sites along the Chilean climate gradient. For this, we predicted the distribution of burrows by applying machine learning techniques in combination with remotely sensed data in the hillslope catchment. Then, we adjusted the spatial model parameters at predicted burrow locations based on field and laboratory measurements. We validated the model using field sediment fences. We estimated the impact of bioturbator burrows on surface processes. Lastly, we analyzed how the impact of bioturbation on sediment redistribution depends on the burrow structure, climate, topography, and adjacent vegetation. Including bioturbation greatly increased model performance and demonstrates the overall importance of vertebrate bioturbators in enhancing both sediment erosion and accumulation along hillslopes, though this impact is clearly staggered according to climatic conditions. Burrowing vertebrates increased sediment accumulation by 137.8 % ± 16.4 % in the arid zone (3.53 kg ha−1 yr−1 vs. 48.79 kg ha−1 yr−1), sediment erosion by 6.5 % ± 0.7 % in the semi-arid zone (129.16 kg ha−1 yr−1 vs. 122.05 kg ha−1 yr−1), and sediment erosion by 15.6 % ± 0.3 % in the Mediterranean zone (4602.69 kg ha−1 yr−1 vs. 3980.96 kg ha−1 yr−1). Bioturbating animals seem to play only a negligible role in the humid zone. Within all climate zones, bioturbation did not uniformly increase erosion or accumulation within the whole hillslope catchment. This depended on adjusting environmental parameters. Bioturbation increased erosion with increasing slope, sink connectivity, and topography ruggedness and decreasing vegetation cover and soil wetness. Bioturbation increased sediment accumulation with increasing surface roughness, soil wetness, and vegetation cover.

Burrowing crabs' influence on tidal marsh vegetation species composition and abundance in a temperate back-barrier marsh, Cape Cod, Massachusetts, USA

Emergent vegetation in coastal marshes across the Northeastern United States have been declining and changing in relative species composition due to abiotic factors such as accelerated sea level rise, storm intensity, excess nutrients, and other anthropogenic disturbances. A possible biotic factor in marsh decline is increased perturbation from burrowing crabs. Uca pugilator and Minuca pugnax (fiddler crabs) whose populations are increasing in many marshes in the eastern US, likely due to disruptions in food webs and expanding habitat from sea level rise. High densities of crab burrows contribute to creek bank erosion and possibly in other factors of marsh peat degradation. When burrowing crabs were excluded from large scale (9 m2) plots in a Cape Cod, MA, marsh for five months, vegetation species richness increased significantly, as did abundance of woody shrubs and the forb, Suaeda maritima (L.). Conversely, burrowing crab exclusion resulted in less Spartina alterniflora (Loisel) and less bare ground - indicating that the other types of vegetation were able to occupy more space in the absence of crab burrowing and sediment sorting activity. The experimental enclosure results were compared with vegetation and burrow density monitoring data taken from nearby long-term monitoring plots. Of the sixteen analyses, we found only one similar result between the 5 month exclusions and monitoring plots; high burrow densities were associated with higher density of S. alterniflora. In contrast to the exclusions, high burrow densities were positively correlated with abundance of Iva frutescens and Suaeda maritima. Six other species (or groupings of rare plants) were negatively associated with burrow densities, four of these are sensitive to inundation and are considered characteristic of the high marsh zone. Different interpretations of the effects of burrowing crabs will result depending on whether correlations are observed from monitoring plots or longer term, large-scale exclusions are conducted; both are needed to assess the rapid vegetation and faunal shifts that are occurring in temperate salt marshes. We suggest that Uca pugilator and Minuca sp. will benefit from sea level rise induced habitat expansion at the expense of the abundance and species richness of flooding-sensitive plants. The erosion and vegetation disturbance that high burrowing crab densities lead to will further exacerbate the decline of these species that are receding at the seaward edge of their distributions.

A Programmable Actuator as Synthetic Earthworm.

Natural earthworm with the ability to loosen soils that favors sustainable agriculture has inspired worldwide interest in the design of intelligent actuators. Given the inability to carry heavy loads and uncontrolled deformation, the vast majority of actuators can only perform simple tasks by bending, contraction, or elongation. Herein, a degradable actuator with the ability to deform in desired ways is presented, which successfully mimics the burrowing activities of earthworms to loosen soils with increased soil porosity by digging, grabbing, and lifting the soil when it receives rains. Such a scarifying actuator is made of degradable cellulose acetate and uncrosslinked polyacrylamide via the swelling-photopolymerizing method. The water absorption of polyacrylamide in moisture conditions causes rapid and remarkable bending. Such mechanical bending can be controlled in specific areas of the cellulose acetate film if polyacrylamide is polymerized in a patterned way, so as to generate complicated deformations of the whole cellulose acetate. Patterning polyacrylamide within cellulose acetate is achieved based on reversible surface protection by means of pen writing, rather than the traditional masking techniques. The water-induced deformation of programmable cellulose-based actuators is well preserved in soil, which is appropriate for promoting rain diffusion as well as root breath.

Збереження гризунів ex situ: досвід утримання сліпачка (Ellobius talpinus) у неволі

The article presents data on the biology of Ellobius talpinus kept in captivity. The creation of semi-underground conditions in terrarium and long-term observations of a group of vole moles during 2003–2014 are described. The course of the life cycle of these animals in the terrarium is presented: daily and seasonal activity, burrowing activity, diet and food preferences, and reproduction. It has been revealed that in captivity mole voles change their daily activity on the surface from crepuscular to diel, which is associated with the absence of disturbance factors or sudden changes in temperature and light. Seasonal activity in captivity is not pronounced, represented by two cases of reproduction that occurred in the summer months. The burrowing activity is extremely high; mole voles burrow or clean the passages daily and often with every activity, without any particular need, demonstrating a stereotypical form of behaviour. Social behaviour, specifics of communication between individuals, and vocalisation are described. It has been noted that the vole moles are characterised by high communication activity, both tactile when adults contact each other and when exploring the environment. Cases of special high-frequency vocalisation such as ‘grinding’ directed not towards another individual, but to the corners of the terrarium, where the mole voles were searching for the possibility of making passages, were repeatedly observed and recorded on video. The following aspects of behaviour were also analysed: reaction to the observer, new conditions, disturbances, and features of group behaviour, including aggression, joint rest, and feeding. Mole voles consumed food both where it was placed and in their chambers, but most often in the chambers there were attempts to create stocks. They preferred roots and bulbs of cultivated plants. The experience of forming reproducing pairs was gained, which allowed us to study the course of pregnancy and the development and growth of the newborn and young. The appearance and condition of the newborn are described along with the presence of teeth, the time when the eyes open, the process of feeding and weaning, growth and weight gain, the ability to move and burrow, and features of parental care. The experience gained demonstrates both the possibility of introduction of the species and the formation of reserve groups to restore lost natural populations.

Neoichnology of vertebrate traces along the western barrier coast of Ukraine: preservation potential and subsurface visualization

A diverse quite of vertebrate traces covers beach, aeolian, and bay-side (deflation flats) surfaces along the NW Black Sea coast of Ukraine. These include avian, ungulate, and canid footprints, as well as mammal burrows (length &gt;5 cm; depth ~2 cm). The preservation of biogenic structures is enhanced by rapid burial (low-energy sedimentation or event deposition), algal mat formation, and salt encrustation. Continuous high-frequency (800 MHz) ground-penetrating radar (GPR) imaging aided in visualizing subsurface sections of an active burrow complex within a beach-dune ridge. Images near an active fox burrow captured distinct subsurface anomalies (point-source hyperbolic diffractions) in the upper aeolian section above the water table. Unfilled tunnel sections are easily distinguished from buried roots and other targets based on signal velocity and polarity reversals relative to air-to-sediment response at the ground surface. The diffraction geometry (angle) is related to signal velocity, providing valuable information about relative saturation of the overlying substrate. Decimeter-scale deformation of shallow reflections may be attributed to tracking surfaces, with similar examples found immediately below modern surfaces affected by anthropogenic trampling. It is likely that muddy lagoonal tracking surfaces may be preserved under layers of sand (overwash or aeolian deposition) and, following saltwater expulsion, may be recognized in geophysical images as clear deformed paleo-surfaces. Heavy-mineral concentrations (e.g. magnetite-rich sand) are common for beach and dune horizons that have undergone reworking and such anomalies often accentuate physical and biogenic deformation structures. Due to moderate-to-high fraction of ferri- and paramagnetic minerals, these anomalies are also well-expressed in GPR images due to its electromagnetic signal response. A conceptual framework of trace preservation potential (taphonomy) and geophysical recognition (GPR) suitability is proposed for this coastal region, with implications to paleo-environmental reconstruction.

The Soft Tick Ornithodoros moubata and Its Role in the Epidemiology of African Swine Fever in Central Malawi.

African swine fever is a viral hemorrhagic disease of pigs (Sus scrofa) caused by a double-stranded DNA virus, African swine fever virus (ASFV). With up to 100% mortality in pigs and no vaccine, the socioeconomic impacts of this disease are immense. In sub-Saharan Africa, warthogs (Phacochoerus africanus) are the original vertebrate host for the virus, which is transmitted among wild suids via the soft tick Ornithodoros moubata. In Malawi, O. moubata is thought to be widely distributed, with the potential to spread ASFV beyond its historical enzootic zone in the Central Region. We surveyed 76 domestic pig farms, 18 active warthog burrows, and three bushpigs (Potamochoerus larvatus) resting sites for O. moubata in the Central Region of Malawi, and tested the ticks for ASFV using PCR. We found a limited distribution for O. moubata: 75 ticks were discovered at a single farm in the Mchinji District. Eleven percent of these ticks were ASFV positive. This suggests that wildlife and O. moubata play a limited role in the epidemiology of ASF in Malawi; thus, other factors for disease spread, such as fomites and pig-to-pig infection, need to be considered.

Shell accumulation on seabed due to suspended coastal oyster farming and effects on burrowing capacity of the polychaete Perinereis aibuhitensis

Mariculture of bivalves (e.g., mussels, scallops, and oysters) is developing rapidly in coastal waters. This process releases shell debris that can accumulate on the seabed under farms. The ecological consequences of shell accumulation on the bioturbation of benthic macrofauna, which play a key role in the biogeochemical processes of sediment, are not yet fully understood. Thus, it is necessary to quantify the shell debris that accumulated under bivalves farms and evaluate whether the shell debris hinders the burrowing capacity of macrofauna. Oysters are common bivalve species cultured worldwide. However, no data are available on shell accumulation due to oyster farming and its possible effects on the burrowing capacity of polychaetes. Thus, we conducted a preliminary study on shells debris accumulation under an oyster farm in Daya Bay, southern China, and assessed the effects of shell accumulation on the burrowing activity of the polychaete Perinereis aibuhitensis in a mesocosm experiment for 32 days. The results showed that oyster farming significantly (p &amp;lt; 0.05) increased the accumulation of shell debris under the farm. The amount of shell debris under oyster farm (6.0 ± 1.3 kg (dry weight (DW)) m-2 or 130.0 ± 24.7 g (DW) kg-1 dry sediment) was approximately two times that in a non-culture area (3.5 ± 0.9 kg (DW) m-2 or 74.9 ± 10.5 g (DW) kg-1 dry sediment). The presence of shell debris did not affect the survival of P. aibuhitensis in experiment, but the animals in sediment with shell added exhibited greater losses of body weight compared with those without, indicating that the presence of shell causes animals to expend more energy in burrowing. The numbers of burrowing holes were lower in sediment with shell debris added compared with those in sediment without shell addition throughout the experiment. Whereas, this does not due to the P. aibuhitensis in +Shell treatment were less active in terms of their burrowing activities. The lower numbers of holes in +Shell treatment was mainly due to P. aibuhitensis were unable to use surface areas where shells were present, the amount of area occupied by shell material physically prevented P. aibuhitensis from forming burrows in these locations. The hindering effects of shells on the burrowing activity of P. aibuhitensis would decrease as the shells degraded into debris. Therefore, we recommend using small shells when conducting “shell addition” bioremediation strategies to avoid the possible negative effects of shells on burrowing by polychaetes.

Differences in substratum preferences and behaviour within the invasive Corbicula species complex

Abstract Clams from the Corbicula species complex of Asian origin are invasive all over the world, currently extending their distribution to waters of the natural thermal regime in Central European areas. Features linking the clams to their habitats in newly invaded areas have not been fully examined. These include substratum preferences and mobility, which may be key to determining potential niche overlap with native bivalves and gaining a better knowledge of their potential active dispersal and impact. Therefore, our aim was to determine the substratum preferences, horizontal locomotion and burrowing behaviour of three Corbicula morphospecies from Poland, Central Europe: two populations of undetermined Corbicula sp. from an artificially heated habitat and water of the natural thermal regime (cold water), as well as Corbicula leana, and Corbicula fluminea (from artificially heated and cold water, respectively). To determine the preferred substratum range, we used pairwise choice tests with a range of muddy, sandy, and gravelly substrata, as well as zebra mussel shells. Then, we conducted behavioural observations (locomotion and burrowing) by CCTV cameras on substrata found as preferred and non‐preferred by clams. All morphospecies preferred fine‐grained over coarser substrata. C. fluminea from cold water had the widest range of substratum preferences. By contrast, C. leana from artificially heated water and Corbicula sp. from cold water showed the narrowest substratum preferences and spent the longest time deeply burrowed. The longest duration of burrowing activity was noted on non‐preferred coarser substrata, which may indicate difficulties in burrowing. On non‐preferred coarse substrata, C. fluminea (cold water) crawled more than the other morphospecies. Our results show that sediment preferences and behaviour (burrowing and locomotion) differ among various Corbicula morphospecies in Europe, probably also varying their invasive potential. This knowledge is important for determining the overlap of habitat preferences of non‐native Corbicula clams with native bivalves, which is critical for determining potential competition strength, impact, and/or displacement. Our results also indicate that habitats with fine sediments could be more threatened by Corbicula invasions.

Alpine grassland degradation intensifies the burrowing behavior of small mammals: evidence for a negative feedback loop.

Globally, grassland degradation is an acute ecological problem. In alpine grassland on the Tibetan Plateau, increased densities of various small mammals in degraded grassland are assumed to intensify the degradation process and these mammals are subject to lethal control. However, whether the negative impact of small mammals is solely a result of population size or also a result of activity and behavior has not been tested. In this study, we use plateau pika as a model to compare population size, core area of colony, and the number of burrow entrances and latrines between lightly and severely degraded grassland. We test whether the alleged contribution of pika to grassland degradation is a result of increased population size or increased burrowing activities of individuals in response to lower food abundance. We found that grassland degradation resulted in lower plant species richness, plant height, and biomass. Furthermore, the overall population size of pika was not significantly affected by location in lightly and severely degraded grassland. However, pika core areas in severely grassland degradation were significantly larger and had significantly higher densities of burrows and latrines. Our study provides convincing evidence that habitat-induced changes in the behavior of small, burrowing mammals, such as pika, can exacerbate grassland degradation. This finding has significant implications for managing small mammals and restoring degraded grassland ecosystems.

Density and extractive potential of “uçá”-crab, Ucides cordatus (Linnaeus, 1763), in mangroves of the “Todos os Santos” Bay, Bahia, Brazil

Ucides cordatus is one of the main fishery resources of the “Todos os Santos” Bay (BTS), State of Bahia, Brazil. Population parameters (structure, density, and fishery potential) of this crab species were analyzed in the dry and rainy seasons in nine mangrove areas of BTS. Five sample quadrats (5 × 5 m) were used to record the number and diameter of active open burrows (with biogenic activity) and closed burrows of U. cordatus, tree variables (composition, density, and diameter), and flood level. Crab density (ind.m−2) was indirectly estimated by counting galleries. The diameter of open galleries was converted into carapace width (CW) using a regression model to later characterize the U. cordatus population structure. There were more galleries in the dry season than in the rainy season. Crab density ranged from 0.32 to 2.63 ind.m−2 (1.32 ± 0.90 ind.m−2), and the mean density was higher during the dry period (t = 0.02; p < 0.05). Crab density differed among sampling areas regardless of seasonal period. Crab size (CW) in BTS was 52.4 ± 16.7 mm, with specimens significantly larger during the dry period (t = 0.01; p < 0.05), and there was a significant difference (F = 4.57; p = 000.1) among mangrove areas. Non-commercial size animals (CW < 60.0 mm) were more abundant (65.2%) than those with commercial size (34.8%) in BTS. Crab density and flood level showed significant negative correlation (p = −0.51; p < 0.05), while there was a positive correlation between CW and flooding level (p = 0.40; p < 0.05). U. cordatus population parameters differed significantly among BTS sampling sites due to their heterogeneity. This study is the first assessment of “uçá”-crab populations in BTS mangroves and reveals a need for a sustainable management in the area. Furthermore, this study could be a model for monitoring other large brachyuran species inhabiting estuarine systems, which are economically and biologically relevant.

Burrow systems of modern subterranean rodents (Ctenomyidae): key neoichnologic features and recognition of fossil examples

This study is aimed to identify the distinctive ichnologic features of burrow systems of two ctenomyid species of extant solitary and subterranean rodents (Ctenomys azarae and C. talarum occidentalis) from La Pampa Province (Argentina). A total of 12 active burrows from different biogeographic provinces were cast with polyurethane foam, then excavated and the entire system was mapped. Ctenomyid burrow systems are shallow (average depth 0.30 m), branched, and subhorizontal with several plugged entrances, having a main tunnel and secondary ones arranged in a single level. Curved length, tortuosity, fractal dimension branching angles, and the scarcity or absence of chambers are similar in both species. The average horizontal diameter is 66 mm, the burrow cross-section is subcircular to vertical elliptical, and entrance ramps slope at an average of 22°. Surface ornamentation in the form of sets of three curved claw traces composing a chevron pattern is dominant. Ctenomys azarae is distinguished from C. talarum occidentalis by the presence of food caches and wider sets of claw traces. Ctenomyidae burrows are easily distinguished from those of Octodontidae and Caviidae using the relative diameter index. The outlined criteria are applied to identify fossil examples of Late Miocene-Holocene ctenomyid burrows.