Estructuras de escape y equilibrio asociadas a Conichnus conicus como indicadores de tasas de sedimentación variables en medios litorales tortonienses del SO de España

Numerous and large vertically extensive specimens of Conichnus conicus are described from the Tortonian deposits of the central Guadalquivir Basin (SW Spain). These burrowing structures form a low bioturbation index of the ichnofabric, which allows one to infer the original depositional setting. Both ichnological and sedimentological features suggest a coastal to shallow marine environment dominated by high sediment supply and high-energy sedimentary processes. Conichnus exhibits a characteristic internal fabric that reflects changes in sedimentation rates linked to various processes: (1) initial substrate penetration by the tracemaker; (2) gradual retrusive movement in response to rapid but continuous sediment aggradation; 3) moderate to high rates of retrusive migration as a consequence of rapid to very rapid sediment aggradation and tracemaker escape; and, finally, (4) abandonment of the burrow or burial of the tracemaker subsequently in response to extremely high sediment accumulation rates. Conichnus has been also described from other areas with similar deposits of different ages, where its important value as a paleoenvironmental indicator similarly has been indicated.     

Equilibrium Responses Reflected in a Large Conichnus (Upper Cretaceous Eutaw Formation,Alabama, USA)

A vertically extensive (1.4 m) specimen of Conichnus in the Cretaceous Eutaw Formation (Alabama) exhibits marginal and internal fabrics that reflect equilibrium behavioral responses to changes in sedimentation rate and erosion events associated with tidal sandwave dynamics. Distinct fabrics can be linked to: (1) initial substrate penetration by the tracemaker, which followed stoss-side erosion of sandwave foresets; (2) gradual retrusive movement in response to slow sediment aggradation (<1 cm/day) in sandwave bottomsets; (3) intermediate to high rates of retrusive migration in response to moderate to rapid sediment aggradation (～1 cm/day) in sandwave toes; (4) tracemaker escape associated with extremely rapid (>5 cm/day) foreset deposition; and (5) protrusive equilibrium movement in response to stoss-side erosion of foresets. Morphological observations in the context of tidal cyclicity suggest that the trace, presumably produced by an anemone, was a semipermanent domicile occupied for at least two to three months. Relationships established between burrow fabric and sedimentary conditions in the Eutaw specimen may aid in the interpretation of conichnian burrows in other high-energy, shallow marine sequences.     

Individually mark–mass release–resight study elucidates effects of patch characteristics and distance on host patch location by an insect herbivore

1. How organisms locate their hosts is of fundamental importance in a variety of basic and applied ecological fields, including population dynamics, invasive species management and biological control. However, tracking movement of small organisms, such as insects, poses significant logistical challenges. 2. Mass‐release and individual–mark–recapture techniques were combined in an individually mark–mass release–resight (IMMRR) approach to track the movement of over 2000 adult insects in an economically important plant–herbivore system. Despite its widespread use for the biological control of the invasive thistle Carduus nutans, the host‐finding behaviour of the thistle head weevil Rhinocyllus conicus has not previously been studied. Insects were released at different distances from a mosaic of artificially created host patches with different areas and number of plants to assess the ecological determinants of patch finding. 3. The study was able to characterize the within‐season dispersal abilities and between‐patch movement patterns of R. conicus. Weevils found host plant patches over 900 m away. Large patches, with tall plants, situated close to the nearest release point had the highest first R. conicus resights. Patch area and plant density had no effect on the number of weevils resighted per plant; however, R. conicus individuals were more likely to disperse out of small patches and into large patches. 4. By understanding how R. conicus locates host patches of C. nutans, management activities for the control of this invasive thistle can be better informed. A deeper mechanistic understanding of host location will also improve prediction of coupled plant–herbivore spatial dynamics in general.     

Priority resource access mediates competitive intensity between an invasive weevil and native floral herbivores

Mechanisms underlying invasive species impacts remain incompletely understood. We tested the hypothesis that priority resource access by an invasive biocontrol weevil, Rhinocyllus conicus, intensifies and alters the outcome of competition with native floral herbivores over flower head resources of the non-target, native host plant Cirsium canescens, specifically with the predominant, synchronous tephritid fly Paracantha culta. Four main results emerged. First, we documented strong, asymmetric competition, with R. conicus out-competing P. culta. Second, weevil priority access to floral resources accelerated competitive suppression of P. culta. Evidence for competitive suppression with increased weevil priority included decreases in both the numbers and the total biomass of native flies, plus decreases in individual P. culta fly mass and, so, potential fitness. Third, we found evidence for three concurrent mechanisms underlying the competitive suppression of P. culta by R. conicus. Prior use of a flower head by R. conicus interfered with P. culta pre-oviposition behavior. Once oviposition occurred, the weevil also reduced fly post-oviposition performance. Preemptive resource exploitation occurred, shown by the significant effect of flower head size on the total number of insects developing and in the magnitude of R. conicus effects on P. culta. Interference also occurred, shown by a spatial shift of surviving P. culta individuals away from the preferred receptacle resources as R. conicus priority increased. Finally, fourth, using an individual-based model (IBM), we found that the competitive interactions documented have the potential for imposing demographic consequences, causing a reduction in P. culta population sizes. Thus, priority resource access by an invasive insect increased competitive impact on the predominant native insect in the invaded floral guild. This study also provides the first experimental evidence for non-target effects of a weed biological control agent on an associated native insect herbivore.     

Microhabitat and rhythmic behavior of tiger beetle Callytron yuasai okinawense larvae in a mangrove forest in Japan

Mangrove forests are regularly flooded by tides at intervals of approximately 12.4 h (tidal rhythm). Larvae of the tiger beetle Callytron yuasai okinawense in a mangrove forest made shallow burrows in mounds up to 1 m in height constructed by the mud lobster Thalassina anomala. No larval burrows were observed on the forest floor, which was very muddy even during low tide. Some larvae plugged the burrow openings before they were submerged at high tide. The mean interval between consecutive burrow plugging events was 12.37 h, which is similar to the period of tidal cycles. Nine out of 30 larvae plugged the burrow openings even when the burrows did not become submerged. Plugging behavior may be governed by an endogenous biological clock, or may be a response to exogenous information about tidal level (e.g. moisture seeping through the ground).     

New bivalve burrows from the mid-Holocene of northeastern Buenos Aires Province (Argentina): ichnotaxonomy and ethology

Oblongichnus vulpesi n. isp. is herein described as amygdaloid, oval or cleft-shaped burrows with a lining of variable thickness and an oblong to quadrangular elongated shaft from the mid-Holocene of the Destacamento Río Salado Member. Valves of the solenid bivalve species Solen tehuelchus were found within the burrows, indicating that this razor clam is the tracemaker. This new finding corroborates the validity of Oblongichnus and previous interpretation that the burrow was produced by infaunal, filter feeding bivalves with a foot of very limited horizontal movements. We found that the origin of oblong elongate bivalves may be dated back to the Ordovician, while an infaunal radiation likely occurred during late Paleozoic. We interpret that O. vulpesi was made in a moderate energy subtidal marine setting during the last marine highstand.     

Multina from the Late Triassic Luning Formation,Nevada

The discovery of the network trace fossil Multina isp. in the Luning Formation of central Nevada provides new insight into the depositional setting of the Shaly Limestone Member of the Luning Formation. The ichnofossils occur in tabular mudstone beds deposited on a shelf environment or open carbonate platform. Although Multina resembles Paleodictyon, as both share polygonal burrow nets and both frequently occur in deep-water habitats, Multina is less regular and has other morphological traits such as crossing burrow branches not seen in Paleodictyon or Protopaleodictyon.     

Influence of age and environmental factors on burrow-making behavior of the short-tailed cricket,Anurogryllus muticus (De Geer) (Orthoptera: Gryllidae)

For the short-tailed cricket, Anurogryllus muticus, burrow-making behavior is essential. All nymphal instars construct burrows, but in the adult stage the rate of burrowing behavior is age dependent. Increases in photophase and light intensity stimulate burrowing, and the explicit negative phototaxis is correlated with the cricket's inability to exist under dry conditions. Ingestion of substrate during burrow construction may serve to acquire additional moisture. There is no evidence of burrow recognition, and crickets can construct a burrow when needed. The natural distribution of burrows at the plot investigated on Moorea supports the notion thatA. muticus builds burrows where the preferred food plantAlysicarpus vaginalis is most abundant. By minimizing the traveling distance to food sources when foraging they can retreat to their burrow again.     

Two Palaeozoic Hydrothermal Vent Communities from the Southern Ural Mountains, Russia

The Sibay and Yaman Kasy massive sulphide deposits contain macrofossil assemblages that represent some of the oldest known hydrothermal vent communities. The deposits are hosted respectively by Middle Devonian and Silurian arc-related volcanic rocks in the Ural Mountains of Russia, and formed under the same environmental constraints as modern vent sulphides. The Sibay palaeocommunity comprises, in order of decreasing abundance, tubes of an indeterminate ?annelid and the vestimentiferan Tevidestus serrriformis Shpanskaya, Maslennikov and Little and articulated specimens of the modiomorphid bivalve Sibaya ivanovi gen. et sp. nov. The Yaman Kasy palaeocommunity comprises, in order of decreasing abundance, tubes of the ?polychaete Eoalvinellodes annulatus gen. et sp. nov. and the vestimentiferan Yamankasia rifeia Shpanskaya, Maslennikov and Little, and specimens of the ?kirengellid tergomyan Themoconus shadlunae gen. et sp. nov., the lingulate brachiopod Pyrodiscus lorrainae gen. et sp. nov., an indeterminate vetigastropod, and the ambonychiid bivalve Mytilarca sp. Some of these taxa have affinities to endemic taxa at modern hydrothermal vent sites and some belong to taxa that are typical of Palaeozoic non-vent marine palaeocommunities. Therefore, there has been movement of taxonomic groups in and out of the vent ecosystem through the Phanerozoic.     

Epizoic bryozoans and corals as indicators of life and post-mortem orientations of the Devonian brachiopod Meristella

The in-life and post-mortem orientations of the Lower Devonian brachiopod Meristella atoka from the Haragan Formation (Lower Devonian; south-central Oklahoma) are inferred from the distribution of epizoic bryozoans and the orientations of base plates of epizoic corals. Three bryozoans, Cyphotrypa corrugata, Fistuliporella maynardi and Leioclema pulchellum, and one coral, Favosites conicus, are considered. Most zoaria that contact the commissure terminate at the commissurc, and a few zoaria terminate at growth lines. This suggests that the bryozoans were primarily life associates of Meristella atoka. Collectively, these three bryozoan species most extensively encrusted marginal sectors of the brachial valve and are very rare on the posteromedian sector (the umbo) of the pedicle valve. This distributional pattern indicates that the preferred living orientation of Meristella atoka was umbo-down (posteromedian sector of the pedicle valve resting on or buried in the substratum) with the commissure steeply inclined to the sediment water interface. Most coralla of Favosites conicus that contacted the commissure encrusted over the commissure. This indicates that Favosites conicus either preferentially encrusted Meristella atoka post-mortem or colonized living brachiopods but subsequently caused them to die. Furthermore, Favosites conicus most extensively encrusted anterior sectors of the brachial valve, especially the fold. The lateral and anterior orientations of the commissure with respect to the base plates (holothecae) of Favosites conicus indicates that the brachiopods were oriented approximately horizontal with respect to the base plates. This suggests that the preferred post-mortem orientation of Meristella atoka was resting nearly horizontally on the substratum. These data and interpretations confirm previously inferred in-life orientations of Meristella atoka and are consistent with post-mortem orientations hypothesized for elongate-oval athyrid brachiopods. □Brachiopoda, Athyridacea, Meristella atoka , palaeoecology, autecology, epizoans, bryozoans, corals, sedimentology, Lower Devonian, North America, Oklahoma.     

Foraging at the thermal limit: burrowing spiders (Seothyra,Eresidae) in the Namib desert dunes

Summary In the Namib Desert dunes, the web of Seothyra sp. (Eresidae) comprises sticky silk lining the edges of a horizontal mat on the sand surface. The spider sits in a silk-lined burrow attached to the mat. Arthropods become entangled in the sticky silk of the mat and are attacked and pulled into the burrow by the spider. We investigated the influence of sand surface temperature on the activity of spiders during the summer. We determined the range of thermal conditions encountered by spiders, their temperature tolerance and the influence of temperature on foraging activity and prey handling behavior. The environmental temperatures available to Seothyra vary from 17–33° C at the coolest time of day to 33–73° C at the hottest. When prevented from retreating into burrows, spiders showed signs of thermal stress at about 49° C, whereas unrestrained spiders continued to forage at web temperatures above 65° C by moving between the hot surface mat and the cooler burrow. Spiders responded quicker to prey stimuli during the hot hours of the day and completed prey capture sequences in significantly less time at surface temperatures above 49° C than below. Furthermore, captured arthropods succumbed more quickly at high surface temperatures. Our study supports the hypothesis that web design and thermoregulatory behaviors enable Seothyra to hunt under extreme thermal conditions.     

Indirect interaction between two native thistles mediated by an invasive exotic floral herbivore

Spatial and temporal variation in insect floral herbivory is common and often important. Yet, the determinants of such variation remain incompletely understood. Using 12 years of flowering data and 4 years of biweekly insect counts, we evaluated four hypotheses to explain variation in damage by the Eurasian flower head weevil, Rhinocyllus conicus, to the native North American wavyleaf thistle, Cirsium undulatum. The four factors hypothesized to influence weevil impact were variations in climate, weevil abundance, phenological synchrony, and number of flower heads available, either on wavyleaf thistle or on the other cooccurring, acquired native host plant (Platte thistle, Cirsium canescens), or on both. Climate did not contribute significantly to an explanation of variation in R. conicus damage to wavyleaf thistle. However, climate did influence weevil synchrony with wavyleaf flower head initiation, and phenological synchrony was important in determining R. conicus oviposition levels on wavyleaf thistle. The earlier R. conicus was active, the less it oviposited on wavyleaf thistle, even when weevils were abundant. Neither weevil abundance nor availability of wavyleaf flower heads predicted R. conicus egg load. Instead, the strongest predictor of R. conicus egg load on wavyleaf thistle was the availability of flower heads on Platte thistle, the more common, earlier flowering native thistle in the sand prairie. Egg load on wavyleaf thistle decreased as the number of Platte thistle flower heads at a site increased. Thus, wavyleaf thistle experienced associational defense in the presence of flowering by its now declining native congener, Platte thistle. These results demonstrate that prediction of damage to a native plant by an exotic insect may require knowledge of both likely phenological synchrony and total resource availability to the herbivore, including resources provided by other nontarget native species.     

Firmground crustacean burrow systems (Glossifungites ichnofacies) in marine shelf deposits,Paleocene Clayton Formation,Alabama, USA

The Paleocene (Danian) Clayton Formation of western Alabama, USA, includes multiple marine shelf parasequences, each comprising a relatively thick marl, capped by a thin limestone, the latter variably reflecting marine flooding episodes. The marls host relatively large firmground burrow systems that penetrate 50–60 cm beneath, and are cast by, superjacent limestones. Excavation of two partially exposed burrow systems – one beneath a highstand parasequence-bounding flooding surface and the other beneath an overlying coplanar sequence boundary/transgressive surface (SB/TS) – reveals complex, primarily horizontal, irregularly branching networks. The former, allied with Thalassinoides paradoxicus, lacks wall bioglyphs, whereas the latter, allied with Spongeliomorpha iberica, is characterized by pervasive, mainly rhombohedral wall bioglyphs that reflect a relatively more firm substrate. Contrasts between these burrow systems are consistent with sequence stratigraphical context and inferred differences in the mechanism and magnitude of depositional hiatuses responsible for firmground development. Both excavated burrow systems likely represent cumulative structures produced by multiple organisms over extended periods of time. The cumulative nature and potential taphonomic biases associated with these and comparable burrow systems in the stratigraphical record preclude confident interpretation of tracemakers and their behaviours. The Clayton burrow systems likely were produced by one or more species of decapod crustacean that engaged in suspension-feeding, surface detritus feeding, gardening or some combination thereof.     

A versatile laboratory stream with examples of its use in the investigation of invertebrate behaviour

A versatile and simple laboratory stream was designed and used to investigate the burrowing activity of two insects in response to changes in water velocity and substrate type.Aphelocheirus aestivalis adults were unable to burrow into sand, however, a small proportion of juveniles did burrow in this substrate. The presence of sand in gravel reduced the burrowing success of adults. Steady increases in flow stimulated the burrowing response of both adults and juveniles on gravel and sandy gravel.Ephemera danica was unable to burrow in sand alone at the velocities used in the experiment. The presence of particles greater than 2 mm in diameter in the substrate appeared to be essential for successful burrowing under the test conditions. An increase in flow from 3 to 8 cm s^–1 resulted in an increase in burrowing. The time taken for each specimen to burrow varied widely within replicate tests but most specimens had penetrated the substrate within 150 seconds of introduction. The implications of these observations in influencing the microdistribution of these species are discussed.     

The Collembolan,oudemansia Esakii,an Intertidal Marine Insect in Hong Kong,with Emphasis on the Floatation Method of Collection

Summary Oudemansia esakii is shown to be a truly marine insect as all stages of the life cycle are found in intertidal sand in Hong Kong. The motile stages migrate vertically and forage during low tide, but burrow into the sand with incoming tidal conditions. An air bubble often forms around them while in the soil. Total forced immersion for 75 hours showed no harmful effects. The greatest burrowing depth is 36 cm and the optimal littoral position is three feet above low water. A floatation method using graded sieves is superior to MacFadyen's high gradient technique. Pertinent hydrographic data are included, as are biological relationships.Marine Science Laboratory, the Chinese University of Hong Kong     

Behavior of the burrowing shrimp Alpheus macellarius in varying gravel substrate conditions

The behavior of the male snapping shrimp, Alpheus macellarius (Decapoda: Alpheidae), was studied in tank experiments with four levels of gravel content for five consecutive days. Markov-chain type analyses identified significant behavioral states that were grouped into six behavioral classes (Wandering, Surveying, Grooming and Foraging, Resting, Hidden). Significant trends in the durations and frequencies of the classes were found across days and periods, with shrimps mainly wandering and burrowing during the first day. Grooming, foraging and resting became more frequent during succeeding days. Shrimps built burrows in the morning and then groomed and foraged mostly in the afternoon. This periodicity implies a greater priority for the shrimp to construct and maintain a burrow rather than forage. Gravel content did not significantly influence burrowing behavior, but marked variations were noted in burrowing success, burrow structure and stability. Animals in 15% and 25% gravel substrates produced more burrows of greater complexity, which lasted longer than those of the shrimps in 0% and 5% gravel setups. Feeding was mainly sediment scavenging suggesting the predominance of a deposit-feeding trophic mode. Modifications in burrow construction and adaptations in burrowing and feeding indicate the ability of A. macellarius to respond to different environmental conditions.     

Burrowing behavior and burrowing energetics of a bioindicator under human disturbance

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Alteration of burrow‐related behaviour of the norway lobster,nephrops norvegicus during infection by the parasitic dinoflagellate hematodinium

This study has used time‐lapse video recordings to analyze the burrow‐related behaviour of N. norvegicus under a 12 h light: dark regime in aquarium conditions, and compared this with the behaviour of lobsters infected by the parasitic dinoflagellate Hematodinium. Uninfected lobsters performed a higher number of burrow departures, of longer duration, during the hours of darkness than during the light. Infected lobsters performed a relatively constant number of departures of similar‐duration in the light and the dark periods. However, the mean number of departures per day performed by infected lobsters (70 day^‐1) was more than double that of uninfected lobsters (30.1 day^‐1), while the mean duration of burrow departures performed by infected lobsters (258.5s departure^‐1) was more than six times greater than in uninfected lobsters (38.7s ? departure^‐1). This led to a more than ten‐times increase (from 1.7 to 19.4%) in the percentage of the day spent out of the burrow by infected lobsters. This altered burrow‐related behaviour could be due to the nutritional demands of the parasites on infected lobsters, causing an increased requirement to forage, or alternatively to a ‘functional hypoxia’, due to the additional respiratory demands of the parasite, causing the host to emerge from the burrow onto the sediment surface to seek oxygen. Implications for the increased time spent out of the burrow are discussed in relation to availability of infected lobsters by trawlers and predators, and to the use of infection prevalence data from trawl‐caught samples in stock assessment models for N. norvegicus.     

The effects of conspecifics on burrow selection in juvenile spotted salamanders (<Emphasis Type="Italic">Ambystoma maculatum)</Emphasis>

Spotted salamanders (Ambystoma maculatum) are pond-breeding amphibians that disperse into terrestrial habitat from natal wetlands after undergoing metamorphosis, relying on small-mammal burrows and coarse woody debris for refugia. The effect of conspecifics on burrow use in juvenile salamanders is poorly understood. Determining how the presence of conspecifics influences the settlement decisions of juvenile salamanders can increase our understanding of amphibian dispersal and our ability to predict population dynamics. We conducted behavioral laboratory trials using 58 recently metamorphosed salamanders to examine how salamanders selected burrows in the presence of conspecifics. Salamanders were more likely to settle in a burrow that was occupied by a conspecific versus an unoccupied burrow. Our results indicate that juvenile salamanders may show conspecific attraction and/or trailing behavior during the dispersal phase.