Shallow Burrows Research Articles

A Critical Review of Eolian Ichnofacies

Two ichnofacies have been named to encompass inland eolian depositional systems, the Octopodichnus and the Entradichnus ichnofacies, and are often combined into a single, Octopodichnus–Entradichnus ichnofacies. In contrast, coastal dune fields are characterized by a mixture of traces produced by marine and nonmarine organisms attributed to a single, Psilonichnus ichnofacies. However, inland eolian depositional systems lack marine organisms and encompass multiple lithofacies, the most extensive and broadly defined as being dunal and interdunal (includes many water laid deposits). The two lithofacies host generally different ichnoassemblages. Dunes are dominated by arthropod and tetrapod walking traces, whereas interdunes are dominated by shallow burrows, though there is some overlap in the ichnoassemblages of both lithofacies. A re-evaluation of the three ichnotaxa unique to the Entradichnus ichnofacies indicates they are invalid: Entradichnus = Taenidium, Pustulichnus = Skolithos, and Digitichnus is not based on a biogenic structure. The Entradichnus ichnofacies is characterized by abundant horizontal, backfilled traces of mobile deposit feeders and other ichnotaxa that indicate it is a synonym of the Scoyenia ichnofacies. I advocate subsuming the Laoporus, Brasilichnium, and Chelichnus ichnofacies of earlier workers under the Octopodichnus ichnofacies. Thus, the two principal ichnofacies of eolian depositional systems are the Octopodichnus and Scoyenia ichnofacies, though several other ichnofacies have been identified. No single ichnofacies characterizes eolian depositional systems.

Proterozoic and Cambrian bioevents

The modern ecosystems began to be formed in the Proterozoic Eon. The Proterozoic fossil record includes bacteria and cyanobacteria, heterotrophic and autotrophic protists, multicellular thallophytes, and metazoans. The gradual increase of the oxygen pressure in the atmosphere took place during the Proterozoic causing a great diversification of eukaryotic life and the origin of metazoans. The first autotrophic protists (acritarchs) originated in the Palaeoproterozoic and reached a high level of diversification in the early Neoproterozoic, when the first heterotrophic protists and biomineralized forms appeared. Several thallophytic groups may have originated during the Palaeoproterozoic, while the Rhodophyta probably radiated during the Mesoproterozoic, and Chlorophyta during the Neoproterozoic. The glacial episodes in the Neoproterozoic led to a mass extinction among protists. The Late Vendian ecosystems reveal deeply renewed assemblages of planktonic protists, problematic metazoan fauna (Ediacara Fauna), ichnofossils and slightly mineralized metazoans (Cloudina). The bioturbation characteristic for these ecosystems appears in form of small, simple and shallow burrows. The biotic turnover at the Neoproterozoic/Cambrian boundary is expressed by a mass extinction and the origin of new primary producers and consumers. The Cambrian rocks show a higher degree of bioturbation, suggesting a drastic change in the techniques of exploitation of the nutrients accumulated in the sediments.

Burrow dynamics of crabs in subtropical estuarine mangrove forest

Several ecological and biogeochemical processes in mangroves are influenced by crab activities through bioturbation, leaf litter consumption, or fecal deposition. Bioturbation might be influenced by crab burrow dynamics or surrounding abiotic and biotic factors or both. Therefore, it is necessary to examine burrow dynamics under different abiotic and biotic conditions. This study was conducted in the estuarine mangroves of Fukido River in the northern part of Ishigaki Island, Japan. Two transects consisting of five and seven 14-m diameter circular plots were established perpendicular to the mangrove/ocean interface. Spatial and seasonal burrow dynamics data were collected from five randomly chosen quadrates within each plot. Burrow density, renewed burrows per day, and collapsed burrows per day significantly varied spatially and seasonally. Burrow density strongly depended on sediment bulk density. Numbers of renewed and collapsed burrows per day were the same (R2 = 0.86) though they significantly differed among the four seasons with being lowest in the winter season. This suggests that temperature, precipitation and crabs occurrence might control seasonal burrow dynamics. Proportion of collapsed burrows were strongly and significantly correlated to sediment bulk density, salinity and sediment temperature, which suggests that sediment properties provide structural support for burrows maintenance. On the other hand, vegetation cover and sediment characteristics influence the proportion of renewed burrows. Burrow depth was significantly controlled by sediment particle size, which suggests that crabs do not create deeper burrow if sediments contain higher amount of coarse sand. Entrance diameter was correlated to percentage organic matter, salinity, fine sand and distance from the river that means seaward sites are occupied by smaller and shallow burrows. Our results suggest that the burrow dynamics depend on abiotic and biotic factors and are useful for understanding spatial and seasonal variations for estimating bioturbation effects on mangroves biogeochemical cycle.

Trace fossils and palynomorphs in Holocene calcareous concretions from Lake Selbusjøen, Mid-Norway: Post-glacial environmental records

Trace fossils and palynomorphs are recorded for the first time in Holocene calcareous concretions from Lake Selbusjøen, Central Norway. The described trace fossils can be assigned to the Mermia ichnofacies, characterizing lake deposits with good oxygenation and low depositional energy. The predominance of simple grazing trails and shallow burrows (e.g. Cochlichnus, Helminthoidichnites and Treptichnus) in silty and sandy concretions possibly represent relatively low-energy sublittoral parts of the lake, while the occurrence of Vagorichnus and Arenicolites in sandy substrate points to littoral and shallow sublittoral areas with moderate depositional energy. The trace fossils and palynomorph assemblages from Lake Selbusjøen appear to relate to periods of climatic warming during Pre-Boreal times, and possibly also Atlantic times.

Trace fossils, depositional context, and paleogeography of the upper Tal Group (upper lower Cambrian), Lesser Himalaya, India: a Gondwanan succession with no affinities to the Avalonia microcontinent – discussion of paper by Singh et al. (2019)

Terminal Ediacaran–late early Cambrian deposition, faunas and passive margin evolution of the north Indian margin are recorded in the Nigali Dhar syncline succession. Restudy of the upper Tal Group (upper lower Cambrian Koti Dhaman Formation, KDF) ichnofauna from the Khud-Drabil section reduces it to 18 confidently named forms. The lower KDF (Lower Quartzite Member) Cruziana-Rusophycus assemblage is in subtidal (not intertidal) sandsheet facies. The overlying black Shale Member (SM) records trans-East Gondwanan deepening, not intertidal facies, in the Palaeolenus Zone. The SM, with low diversity Planolites-Palaeophycus assemblage, is overlain by subtidal (not intertidal) sandsheet facies of the middle KDF (Arkosic Sandstone Member, ASM) with shallow burrowers and furrowers (Gordia marina assemblage, new; Cruziana ichnofacies). KDF faunas with Cruziana and Rusophycus are similar to coeval, shallow marine associations elsewhere in Gondwana and NW Laurentia. Interpretation of a second KDF section 20 km from Khud-Drabil has confused an understanding of Lesser Himalaya geologic evolution as it claims Ordovician Cruziana species in the ASM and an angular SM–ASM unconformity caused by the Cambrian–Ordovician boundary Kurgiakh orogeny. However, upper lower Cambrian microfaunas occur in and above the ASM, while the angular SM–ASM unconformity is consistent with submarine sliding. KDF-type ichnofaunas do not show a tropical location of Avalonia, which has the distinctive lithofacies and biotas of a high-latitude continent unrelated to Gondwana.

Does wild boar rooting affect spatial distribution of active burrows of meadow-dwelling voles?

Soil overturn by wild boar Sus scrofa is known to affect biodiversity, from plant communities to invertebrates, reptiles and small mammals. Rooting activity has been shown to be particularly intensive in open areas and particularly on fallows and meadows located on hill or mountain tops. In these habitat types, the impact of wild boar on small mammal assemblies has never been assessed. In this work, we evaluated whether rooting activity affected the spatial distribution of the Savi’s pine vole Microtus savii in a hilly area of Central Italy, throughout four seasons. The spatial distribution of this vole has been determined through the open-hole index, i.e. by assessing the vole propensity to reopen tunnel entrances which we previously closed with soil. Rooting intensity was the highest in cold months, i.e. when drive hunting may increase wild boar occurrence within protected areas and outside wooded areas. According to our GLMM, reopening of vole burrow entrances increased with increasing distances from rooted areas and with increasing geophytic diversity. Meadow-dwelling voles living on shallow underground burrow systems seem to avoid soil overturn by wild boar and that they prefer creating their tunnels where plant diversity building up the staple of their diet is the highest. Our results furtherly emphasized the importance of wild boar monitoring also in open areas and hill grasslands, particularly when rooting intensity is the highest, i.e. in cold months.

Gas composition and its daily changes within burrows and nests of an Afroalpine fossorial rodent, the giant root-rat Tachyoryctes macrocephalus

Fossorial mammals are supposed to face hypoxic and hypercapnic conditions, but such conditions have been rarely encountered in their natural burrow systems. Gas composition in burrows after heavy rains, deeper burrows and especially nest chambers, where animals usually spend most of the day, could be even more challenging than in shallow burrows. Such situations, however, have been rarely surveyed in the wild. In our study, we determined concentrations of O2, CO2 and CH4 in active burrows and nests of the giant root-rat Tachyoryctes macrocephalus, a large fossorial rodent endemic to the Afroalpine zone of the Bale Mountains in Ethiopia. We were able to determine the precise location of nests by tracking individuals equipped with radio-collars. To the best of our knowledge, this is the first study that analyses air samples taken directly from the nests of actually occupied burrow systems in any free-living fossorial mammal. We found no evidence for environmental hypoxia in the examined burrows and nests (range 19.7–21.6% O2). Concentrations of CO2 in the burrows increased after the burrows were plugged in the evening, but did not reach physiologically problematic levels. The highest CO2 concentrations in burrows were detected in the evening during a wet period (up to 0.44%). In root-rat nest chambers, the highest (but still harmless) CO2 concentrations (up to 1.31%) were detected in the morning (measured in the late dry season only) together with an elevated concentration (up to 13.5ppm) of CH4. Regular surface activity of giant root-rats, combined with the relatively large dimensions of their nest chambers and tunnels, and the absence of heavy soils, may contribute to harmless atmospheres within their burrow systems.

Citizen science frontiers horseshoe crab population regain at their spawning beach in East Peninsular Malaysia

Carcinoscorpius rotundicauda and Tachypleus gigas may co-exist and share common spawning grounds elsewhere but at Balok (East Coast of Peninsular Malaysia), C. rotundicauda is an understudied species. Neglected as research candidate because of inaccessible spawning grounds, smaller size and less commercial value than T. gigas and also, difficulty to attain from the wild has made C. rotundicauda population status remaining unidentified at Balok. This standpoint drove the present attempt because anthropic activities like structure placement and mining are point-source for runoffs that load sediments into Balok River. While erosion-accretion events have altered Balok River width, the shore sediments in Balok Beach were transitioned between medium-fine and fine sand between years 2012 and 2016. Eventually by year 2016, the C. rotundicauda were depositing 5117 eggs in 91 nests from 200 to 1000 m range along this corridor facing South China Sea. From this yield, C. rotundicauda released 2880 eggs in 56 nests during the Southwest monsoon, 1254 eggs in 19 nests during the Northeast monsoon and 983 eggs in 16 nests during the Inter-monsoon seasons. Though female C. rotundicauda opted to lay their eggs in shallow burrows at lower shorelines, the absence of erosion and substantial silt and clay (>20%) deposition facilitates C. rotundicauda embryogenesis with brief periods of temperature and salinity shocks during day-time falling tides. This encourages C. rotundicauda to emerge with increasing abundance and carry out bi-monthly spawning at Balok Beach. In short, shore restoration initiatives like systematic boat docking, proper disposal of nets and waste and, periodic fish-catching operations were effectively led by the Balok fisher citizen scientist. This successful community joint-cooperation proves that citizen-led caretaking of degraded beaches offers marine life protection and are practical for coastal area management especially at areas where other oviparous animals such as turtles and crocodiles are harboured.

Early Palaeozoic ocean anoxia and global warming driven by the evolution of shallow burrowing

The evolution of burrowing animals forms a defining event in the history of the Earth. It has been hypothesised that the expansion of seafloor burrowing during the Palaeozoic altered the biogeochemistry of the oceans and atmosphere. However, whilst potential impacts of bioturbation on the individual phosphorus, oxygen and sulphur cycles have been considered, combined effects have not been investigated, leading to major uncertainty over the timing and magnitude of the Earth system response to the evolution of bioturbation. Here we integrate the evolution of bioturbation into the COPSE model of global biogeochemical cycling, and compare quantitative model predictions to multiple geochemical proxies. Our results suggest that the advent of shallow burrowing in the early Cambrian contributed to a global low-oxygen state, which prevailed for ~100 million years. This impact of bioturbation on global biogeochemistry likely affected animal evolution through expanded ocean anoxia, high atmospheric CO2 levels and global warming.

Late Ediacaran trackways produced by bilaterian animals with paired appendages.

Ediacaran trace fossils provide key paleontological evidence for the evolution of early animals and their behaviors. Thus far, however, this fossil record has been limited to simple surface trails and relatively shallow burrows. We report possible trackways, preserved in association with burrows, from the terminal Ediacaran Shibantan Member (ca. 551 to ca. 541 million years ago) in the Yangtze Gorges area of South China. These trace fossils represent the earliest known trackways. They consist of two rows of imprints arranged in poorly organized series or repeated groups. These trackways may have been produced by bilaterian animals with paired appendages, although the phylum-level phylogenetic affinity of the trace makers remains unknown. It is possible that the trackways and associated burrows were produced by the same trace maker, indicating a complex behavior involving both walking and burrowing. Together, these trackways and burrows mark the arrival of a new era characterized by an increasing geobiological footprint of bilaterian animals.

Centimeter-wide worm-like fossils from the lowest Cambrian of South China

The trace fossil record implies that large worm-like animals were in place along with the skeletonizing organisms during the initial stage of the Cambrian explosion. Body fossils of large worms, however, have so far not been found. Here, we describe a large, soft-bodied, worm-like organism, Vittatusivermis annularius gen. et sp. nov. from the lowest Cambrian of South China, which is constrained to the Fortunian Age (541–529 Ma) of the Cambrian Period. The elongate body of Vittatusivermis was large enough to have supported organ systems and a fluid skeleton that facilitated peristaltic locomotion, thus allowing for more complex patterns of movement than those of flatworms. Its occurrence on the same bedding surface as trace fossils suggests that Vittatusivermis might have produced epichnial trails and shallow burrows on and within sediments. Therefore, Vittatusivermis is likely to have been one of the long expected producers of trace fossils in the earliest Cambrian.

Intertidal mangrove boundary zones as nursery grounds for the mud crab Scylla serrata

The demand for mud crab Scylla serrata (Forsskål 1775) in the global market has increased, hence there is growing momentum to farm the species in Africa. Aquaculture production in Kenya and elsewhere in East Africa currently relies on juvenile seeds sourced from the wild. Wild-seed collection calls for management of the juvenile crab industry founded on knowledge of the species’ ecology, so as to achieve a sustainable seed supply and recruitment to the capture fishery. This study investigated the tidal, diurnal and seasonal occurrence of juvenile crabs in three habitats (intertidal-flat boundary zones, inside the mangroves, and in channels) in small creeks (Mida, Kilifi and Mtwapa) and Gazi Bay, on the coast of Kenya. Sampling was done with scoop nets and seining at receding tides and via burrow searches at low spring tides (day and night). Juveniles in the mangrove/intertidal-flat boundary zone were found sheltered under mangrove leaves or debris, or in shallow burrows during low spring tides, whereas at receding tides they could be seen moving out with the tide or searching for sheltering substrate or burrows. Catch per unit effort at high-abundance sites varied between 59 and 68 crabs fisher−1 day−1. More juvenile crabs, sized 10–80 mm internal carapace width (ICW), occurred at night during the receding tide. Net-seining was effective in the collection of juvenile mud crabs <30 mm ICW, whereas burrow sampling was effective for gathering larger crabs. However, collection of juveniles by seining reduced the quality of the crabs caught due to frequent loss of chelipeds, as compared with retrieving individual crabs by searching burrows. Some juveniles collected in the intertidal-flat boundary-zone habitat were either in the process of moulting or had just moulted, indicating the significance of this habitat for mud crabs at this physically delicate life stage.

Biotic recovery after the end-Triassic extinction event: Evidence from marine bivalves of the Neuquén Basin, Argentina

We analyze the Late Triassic extinction and Early Jurassic recovery of bivalve faunas within marine environments in the Atuel River area of the Neuquén Basin, Argentina. Data were collected from a hundred samples with invertebrates in a well-exposed uppermost Triassic to lower Jurassic section in the Neuquén Basin (southern Mendoza Province, Argentina) and allow a high-resolution reconstruction of the local diversity dynamics. The nearly continuous presence of marine stenohaline major taxa such as cnidarians, rhynchonelliform brachiopods, echinoderms and cephalopods indicates normal salinity throughout. All bivalve species were identified, and each occurrence was recorded in meters above the base. To analyze the systematic diversity trends, diversity curves were calculated on the basis of the first and last occurrence data for each bivalve species, and both total diversity and boundary crossers diversity were used. As a result, four main phases were identified: a) Triassic equilibrium phase (Rhaetian), with relatively high origination and extinction rates; b) extinction phase (latest Rhaetian to earliest Hettangian), with high extinction rates and low origination rates; c) recovery phase (late Early to early Late Hettangian), with high origination rates and almost null extinction rates; and d) Jurassic equilibrium phase (Late Hettangian-Sinemurian), again with similar and relatively high origination and extinction rates. The extinction and recovery phases are separated by a gap of about 135m without identifiable benthonic invertebrates but with early Hettangian ammonites. On the other hand, bivalve palaeoecologic diversity seems to have been more homogeneous along the section, being dominated by attached epifaunal species, though before the extinction epifaunal habits were slightly surpassed by infaunal ones. Slight differences observed include a) shallow burrowers were more diverse during the Rhaetian than during the earliest Jurassic and b) epifaunal free-lying and semi-infaunal attached bivalves were more diverse after the Rhaetian extinction.

Structural and functional changes of soft-bottom ecosystems in northern fjords invaded by the red king crab (Paralithodes camtschaticus)

Abstract The red king crab invaded Norwegian coastal waters in the early 1990s after having been introduced from the northern Pacific to the Russian Barents Sea coast. The crab stock increased rapidly in NE northern Norway in the latter half of the 1990s, and since 2002 there has been a commercial fishery in the eastern invaded areas. The crab is an active predator on benthic fauna especially feeding in deep soft-bottom environments. The present study is a follow-up of previous studies (2007–09) to assess the effects of the king crab predation on soft bottom species composition, ecological functioning and sediment quality. Macroinfauna (> 1 mm) was investigated in three fjord areas in the Varanger region with low, moderate and very high crab abundances, respectively. Compared with data from 1994, most benthic species were markedly reduced in abundance, in particular non-moving burrowing and tube-dwelling polychaetes, bivalves and echinoderms. However, a few species appeared to recover from 2007–09 to 2012. Changes in ecological functioning were assessed using ‘biological traits analysis (BTA)’. Following the crab invasion there was a relative reduction of suspension and surface deposit feeding species, an increase in mobile and predatory organisms and an increase in those with planktotrophic larval development. From low to high crab abundances functioning changed from tube-building, deep deposit feeding and fairly large size to free-living, shallow burrowing and rather small size. With regard to sediment reworking, downward and upward conveyors were reduced whereas surficial modifiers increased. The changes imply that sediment biomixing and bioirrigation were reduced leading to a degraded sedimentary environment. It is suggested that establishing relationships between ecosystem functioning and crab abundances may form the basis for estimating ecological costs of the crab invasion. Such knowledge is important for managing the crab in the Barents Sea area being both a non-indigenous species affecting native ecosystems as well as a valuable resource for commercial fishery.

Revision of the Australian Union-Jack wolf spiders, genus Tasmanicosa (Araneae, Lycosidae, Lycosinae).

The Australian wolf spider (Lycosidae Sundevall, 1833) genus Tasmanicosa Roewer, 1959 with Lycosa tasmanica Hogg, 1905 as type species is revised to include 14 species: T. godeffroyi (L. Koch, 1865), comb. nov. (= Lycosa tasmanica Hogg, 1905, syn. nov.; = Lycosa zualella Strand, 1907, syn. nov.; = Lycosa woodwardi Simon, 1909, syn. nov.); T. fulgor sp. nov.; T. gilberta (Hogg, 1905) comb. nov.; T. harmsi sp. nov.; T. hughjackmani sp. nov.; T. kochorum sp. nov.; T. leuckartii (Thorell, 1870), comb. nov. (= Lycosa molyneuxi Hogg, 1905, syn. nov.); T. musgravei (McKay, 1974) comb. nov.; T. phyllis (Hogg, 1905) comb. nov. (= Lycosa stirlingae Hogg, 1905, syn. nov.); T. ramosa (L. Koch, 1877), comb. nov.; T. salmo sp. nov.; T. semicincta (L. Koch, 1877) comb. nov.; T. stella sp. nov.; and T. subrufa (Karsch, 1878) comb. nov. Within the Australian wolf spider fauna, the genus Tasmanicosa can be diagnosed by the distinct pattern of radiating light and dark lines forming a "Union-Jack" pattern on the carapace. Male pedipalp morphology identifies the genus as part of the subfamily Lycosinae Sundevall, 1833 due to the presence of a transverse tegular apophysis with dorsal groove guiding the embolus during copulation. However, genital morphology is variable and a synapomorphy based on male pedipalp or female epigyne morphology could not be identified. Members of Tasmanicosa are comparatively large spiders (body length ca. 12-30 mm), that build a shallow burrow, which is sometimes covered with a flimsy trapdoor. Species of Tasmanicosa are largely a Bassian faunal element with preference for open woodlands and/or floodplains, although some species can be found into the semi-arid Australian interior. Two Australian wolf spider species may represent Tasmanicosa based on their original descriptions, but due to immature types in combination with the somatic similarities of all Tasmanicosa species, cannot be identified with certainty. They are therefore considered nomina dubia: Lycosa excusor L. Koch, 1867 and Lycosa infensa L. Koch, 1877. The type species of Orthocosa Roewer, 1960 is transferred to Tasmanicosa; however, in order to prevent some non-Australian wolf spiders in the genus Orthocosa to be transferred into Tasmanicosa, which is considered endemic to Australia, we here place these species into more appropriate genera based on their original descriptions pending a future revision of these species: Arctosa ambigua Denis, 1947 comb. reval.; Alopecosa orophila (Thorell, 1887) comb. nov.; Hygrolycosa tokinagai Saito, 1936 comb. reval. Orthocosa sternomaculata (Mello-Leitão, 1943) is considered a junior synonym of Hogna birabeni (Mello-Leitão, 1943) comb. nov.

The impact of sheep grazing on the depth of spider burrows and of burrows selected by the pygmy bluetongue lizard (Tiliqua adelaidensis)

Context Grazing by domestic stock can potentially influence ecosystems positively or negatively, depending on the grazing regime and intensity. The pygmy bluetongue lizard (Tiliqua adelaidensis) is an endangered species, restricted to fragmented grasslands in the Mid North region of South Australia, predominantly grazed by sheep. These lizards refuge in vertical burrows. They do not dig their own burrows, instead relying on co-existing spiders for this essential resource. Aims We investigated how sheep grazing influenced spider burrows, and predicted the following: that grazing sheep might trample and destroy shallow burrows; that burrows in grazed habitat with less vegetative cover would have higher temperatures in summer; and that, by way of compensation, spiders would dig deeper burrows in grazed habitat. Methods We monitored 12 30m×30m plots monthly, over two austral spring/summer periods (September–March 2012–14). We recorded the number, depth and occupant of all spider burrows in those plots in each survey. We also measured temperatures inside artificial burrows in grazed and ungrazed habitat over a 3-day period in September 2014. Key results Mean burrow depth increased with grazing. This was not because individual burrows became deeper, but because the shallowest burrows were lost where there were sheep. Burrows were significantly hotter in grazed habitat, but lizards consistently chose deeper, cooler burrows. In the subset of burrows that were occupied by lizards, there was no difference in depth between grazed and ungrazed treatments. We detected no difference in spider digging activity between grazed and ungrazed plots. Conclusions Sheep grazing can destroy shallow burrows, probably through trampling, and because sheep produce burrow filling debris. However, grazing did not affect deeper burrows occupied by pygmy bluetongue lizards. Implications This short study indicated that moderate levels of grazing have low impact on deeper burrows suitable for pygmy bluetongue lizards and for lizard persistence. It explains how sheep and lizards have co-occurred for so long, but leaves open the question of how the loss of shallow burrows affects populations of the burrow-digging spiders that are an essential component of the lizard environment.

On burrow morphology of the ghost crab¸ &lt;i&gt;Ocypode ceratophthalmus&lt;/i&gt; (Decapoda;Brachyura: Ocypodidae) from sandy shore of Gujarat, India

Burrow morphology of brachyuran crab Ocypode ceratophthalmus was studied at two different sites located on the Saurashtra coast of Gujarat state, India. Diluted resin was poured in the burrows for burrow cast. Crab, if emerged out from the burrow, was caught and carapace width and sex were recorded. The complete burrow casts were analyzed for various morphological characters and shapes. The depth wise variation in sediment temperature of the burrow was measured at the depth interval of 5 cm. A total of 55 intact burrow casts were obtained and 8 different types of burrow shapes were recorded. The crab carapace width showed significant correlation with burrow opening diameter, burrow volume and burrow total length. The juveniles were observed utilizing shallow burrow with small opening diameter located near water line while adults were observed utilizing deep burrows with large diameter located on the upper part of sandy shore. Specific pattern was observed in the burrow temperature in which the burrow temperature dropped significantly at the greatest depth which provides suitable environment to the crab to survive in the harsh environmental conditions.

The regulation of copper stress response genes in the polychaete Nereis diversicolor during prolonged extreme copper contamination.

Polychaetes are frequented in toxicological studies, one reason being that some members occupy shallow burrows in sediments and are maximally exposed to the contaminants that accumulate within them. We have been studying one population of the polychaete Nereis (Hediste) diversicolor exhibiting inheritable tolerance to extreme copper contamination in estuarine sediment. Using transcriptome sequencing data we have identified a suite of genes with putative roles in metal detoxification and tolerance, and measured their regulation. Copper tolerant individuals display significantly different gene expression profiles compared to animals from a nearby population living without remarkable copper levels. Gene transcripts encoding principle copper homeostasis proteins including membrane copper ion transporters, copper ion chaperones and putative metallothionein-like proteins were significantly more abundant in tolerant animals occupying contaminated sediment. In contrast, those encoding antioxidants and cellular repair pathways were unchanged. Nontolerant animals living in contaminated sediment showed no difference in copper homeostasis-related gene expression but did have significantly elevated levels of mRNAs encoding Glutathione Peroxidase enzymes. This study represents the first use of functional genomics to investigate the copper tolerance trait in this species and provides insight into the mechanism used by these individuals to survive and flourish in conditions which are lethal to their conspecifics.

EXCEPTIONALLY WELL PRESERVED LATEST MIOCENE (HEMPHILLIAN) RODENT BURROWS FROM THE EASTERN GREAT PLAINS, UNITED STATES, AND A REVIEW OF THE BURROWS OF NORTH AMERICAN RODENTS

Dozens of well-preserved fossil burrow systems in upper Miocene sedimentary rocks of the Ogallala Group at a site in east-central Nebraska record rodent behavior and the subsurface ecology of grasslands just as the modern Great Plains was developing. These burrow systems include one to four entrance or exit tunnels, large underground nesting chambers at depths of several decimeters below ancient land surfaces, and incisor grooves on the walls. Tunnels average 89.8 mm in diameter, a value similar to the burrow diameters of multiple living North American rodents. Chambers vary in shape and typically exceed 500 mm in length; some attain 1000 mm in length. Living marmotine ground squirrels (tribe Marmotini) construct burrow systems of varying degrees of complexity, but they do not engage in shallow subsurface foraging. Extinct members of this group were the most likely excavators of the fossil burrows. In contrast, extant pocket gophers (family Geomyidae) and, presumably their fossil relatives, are obligate subterranean animals that produce linked deep and shallow burrow subsystems, the latter representing their chief foraging strategy. Our results raise issues regarding the relationships between the architecture of fossil rodent burrow systems and aspects of rodent behavior and life history, such as litter size, developmental rates, seasonal torpor, hibernation, and sociality in grasslands. An improved understanding of the burrowing behaviors of ancient rodents will highly complement the growing body of knowledge about the development of grasslands on Earth over time, but truly ichnological analyses of the burrows and burrowing behaviors of extant rodents are much needed.

Drilling Intensity Varies Among Neogene Tropical American Bivalvia in Relation to Shell Form and Life Habit

We calculated the incidence of drilling on bivalve genera from the Neogene fossil record of Panama and Costa Rica to determine differences in predation intensity among groups based on shell architecture, life habit, mobility, and taxonomic affinity. Bulk samples from 28 localities yielded >106,000 bivalve specimens, which were examined for characteristic drilling traces of muricid and naticid gastropods. We calculated the drilling intensity for the 90 most common genera, and characterized the size, ornament, life habit, and mobility for each genus. Large size confers considerable protection from drilling, but shell ornamentation does not. Life habit is strongly linked with drilling intensity. Epifaunal bivalves experience higher predation than infaunal bivalves and shallow burrowers experience higher drilling than deep burrowers. Mobility is also important for epifaunal bivalves; cemented taxa are twice as likely to be drilled as their uncemented counterparts. Our results suggest that bivalve behavior and life habits are more important than shell architecture for defense against drilling predators.