Crayfish Burrows Research Articles

Strong Site Fidelity and a Variety of Imaging Techniques Reveal Around-the-Clock and Extended Activity Patterns in Crawfish Frogs (Lithobates areolatus)

Crawfish frogs (Lithobates areolatus) base their nonbreeding activities in and around the entrances of crayfish burrows. This site preference allows individual crawfish frogs to be monitored using still and video imaging techniques. We used three camera types offering different continuities, scales, and resolutions of data to observe the frogs' activity patterns and nonbreeding behaviors. Together, these techniques allowed us to observe two behaviors in crawfish frogs previously unreported for amphibians: (1) circumdiel activity patterns, and (2) long periods (days) of surface activity. Although these behavioral findings are at this time specific to crawfish frogs, we suspect that they may not be unusual activity patterns for other frogs, as well. The use of imaging techniques that take advantage of these frogs' dependence on burrows and use of burrow entrances has allowed us to observe these patterns for the first time.

Ecology ofCambarus dubius(Upland Burrowing Crayfish) in North-Central West Virginia

The ecology of primary burrowing crayfishes is poorly understood, especially for high-elevation species. An ecological study of Cambarus (Jugicambarus) dubius (Upland Burrowing Crayfish) was conducted at Terra Alta, Preston County, WV (elevation 781 m). The study sought life-history information including size at sexual maturity, age cohort designation, and age estimation. The density and distribution of burrow portals of C. dubius were examined within and near seeps in forested and disturbed habitats. Data were also collected on intraspecific usage of burrows by commensal species. Size at maturity did not differ significantly for males and females. The average age of C. dubius was 1.5 years, and the oldest individuals were estimated at 7 years. Form change of C. dubius occurred synchronously within the population, a phenomenon not previously documented with primary burrowing Cambarus. Burrow portals had highest densities within 5 m of the center of seeps in forested habitats, but reached highest densities between 10 and 25 m from the center of seeps in disturbed habitats. Many commensal species of invertebrates and vertebrates used C. dubius burrows, data that demonstrates a community-level contribution of C. dubius. Information from this study represents most of the available ecological data from the northern range of this species, and is directly relevant for management and conservation of high-elevation populations of C. dubius.

Crayfishes of Western Maryland: Conservation and Natural History

Abstract Conservation concerns for imperiled crayfish faunas have recently increased among resource management agencies. In Maryland, major concerns include the introduction of nonnative crayfishes and their impacts on native species. This study documented the species distribution and conservation standing of native and nonnative crayfishes of western Maryland. Native species include Orconectes (Crockerinus) obscurus (Allegheny Crayfish), Cambarus (Jugicambarus) dubius (Upland Burrowing Crayfish), Cambarus (Cambarus) bartonii bartonii (Common Crayfish), and Cambarus (Cambarus) carinirostris (Rock Crawfish). Introduced species are Orconectes (Gremicambarus) virilis (Virile Crayfish), Procambarus (Ortmannicus) acutus (White River Crawfish), and Cambarus (Tubericambarus) thomai (Little Brown Mudbug). Nonnative species were found primarily in areas of high anthropogenic activity, with populations of O. virilis and P. acutus isolated to impoundments. The presence of C. thomai in Maryland was first documented t...

Transient dwarfism of soil fauna during the Paleocene-Eocene Thermal Maximum.

Soil organisms, as recorded by trace fossils in paleosols of the Willwood Formation, Wyoming, show significant body-size reductions and increased abundances during the Paleocene-Eocene Thermal Maximum (PETM). Paleobotanical, paleopedologic, and oxygen isotope studies indicate high temperatures during the PETM and sharp declines in precipitation compared with late Paleocene estimates. Insect and oligochaete burrows increase in abundance during the PETM, suggesting longer periods of soil development and improved drainage conditions. Crayfish burrows and molluscan body fossils, abundant below and above the PETM interval, are significantly less abundant during the PETM, likely because of drier floodplain conditions and lower water tables. Burrow diameters of the most abundant ichnofossils are 30-46% smaller within the PETM interval. As burrow size is a proxy for body size, significant reductions in burrow diameter suggest that their tracemakers were smaller bodied. Smaller body sizes may have resulted from higher subsurface temperatures, lower soil moisture conditions, or nutritionally deficient vegetation in the high-CO(2) atmosphere inferred for the PETM. Smaller soil fauna co-occur with dwarf mammal taxa during the PETM; thus, a common forcing mechanism may have selected for small size in both above- and below-ground terrestrial communities. We predict that soil fauna have already shown reductions in size over the last 150 years of increased atmospheric CO(2) and surface temperatures or that they will exhibit this pattern over the next century. We retrodict also that soil fauna across the Permian-Triassic and Triassic-Jurassic boundary events show significant size decreases because of similar forcing mechanisms driven by rapid global warming.

Paleoclimatic Implications of Crayfish-Mediated Prismatic Structures in Paleosols of the Paleogene Willwood Formation, Bighorn Basin, Wyoming, U.S.A.

Abstract Paleosols at Polecat Bench, northern Bighorn Basin, Wyoming, show prismatic structures not previously described in the Paleogene Willwood Formation. Prisms are densely spaced 15–50 mm diameter cylinders with vertical to slightly sinuous paths up to 400 mm long, subangular to rounded vertical faces, and slightly concave to convex tops. Prism exteriors are coated commonly by < 1-mm-thick clay films; exteriors also commonly show knobby and striated surficial morphologies. Prismatic structures are nearly exclusive to thin-bedded (< 1 m thick) compound paleosols composed of red to red-purple sandy mudrock overlying gray to green-gray heterolithic units composed chiefly of fine-grained sandstone. In addition to prismatic structures, these paleosols are characterized by large gray mottles, slickensides, and calcareous rhizocretions which crosscut or more typically follow prism exteriors. The architectural and surficial morphology of the soil prisms suggest strongly that these are pedogenically modified freshwater crayfish burrows of the ichnospecies Camborygma litonomos. At Polecat Bench, an ~ 40 m interval of the Willwood Formation records a transient episode of global warming known as the Paleocene–Eocene Thermal Maximum (PETM). The PETM interval is characterized by a series of predominantly red, cumulative paleosol profiles and increased soil carbonates. Prismatic soil structures and crayfish burrows are rare or absent in cumulic paleosols typical of the PETM, whereas they are locally abundant in red compound paleosols outside the PETM interval. The changes in paleosol morphology and a sharp decrease in crayfish burrows within the PETM interval suggest significantly improved soil-drainage conditions and lower water tables on the Willwood floodplain during the global warming event.

Seasonal Variation and Ecological Effects of Camp Shelby Burrowing Crayfish (Fallicambarus Gordoni) Burrows

ABSTRACT Foam casts and burrow excavations were used to examine Fallicambarus gordoni burrow occupancy rates, seasonal variation in burrow morphology, correlation between crayfish abundance and burrow abundance and potential ecological effects of burrowing through soil disturbance and the creation of fossorial habitat. Burrow occupancy rates were high (75%) and consistent between active and inactive seasons, although several burrow metrics differed significantly between seasons. Crayfish abundance was strongly correlated with burrow abundance. Estimates of annual soil disturbance (82 metric tons/ha/y) and fossorial habitat created (29–49 km/ha) suggest F. gordoni serves important ecological functions within the greater habitat.

Evaluating the non-consumptive, positive effects of a predator in the persistence of an endangered species

Failure to consider both the consumptive and non-consumptive effects of predators on prey can lead to erroneous conclusions about the net effect of the relationship. The predatory devil crayfish, Cambarus diogenes Girard functions as an ecosystem engineer constructing extensive burrow systems through aquatic habitats. Despite crayfish posing a serious predation threat, preliminary data indicate that the federally endangered Hines Emerald dragonfly larvae, Somatochlora hineana Williamson regularly inhabit crayfish burrows. During late summer, S. hineana larval habitat dries up; leaving crayfish burrows as some of the only wetted habitats. Thus, C. diogenes can affect S. hineana through both direct, negative and indirect positive effects. We examined the positive role of crayfish burrows as drought refuges, and the threat of predation by C. diogenes on S. hineana larvae. Monthly field sampling indicated that S. hineana use open channel areas in spring and early summer moving into burrow systems in mid summer when channel areas normally dry. Laboratory experiments and field observations confirmed that crayfish prey on S. hineana larvae. Adult crayfish were a larger predation threat than juvenile crayfish. Despite their negative predatory impact, removal of crayfish from burrows in the field did not enhance densities of S. hineana larvae. Although S. hineana may face the threat of predation in burrows, they face a greater risk of desiccation if they remain in the open channel. These results lead to the counterintuitive conclusion that the maintenance of a predator is important for conserving an endangered prey species.

Comparison of Two Burrowing Crayfish Trapping Methods

A new non-destructive method of sampling burrowing crayfish, the burrowing crayfish net, was compared to the Norrocky burrowing crayfish trap. The new sampling method captured significantly more crayfish than did the trap. Captured crayfish sizes were similar and sex ratios were not biased in the two methods. Sixteen species of crayfish have been captured with the burrowing crayfish net.

Association between burrow densities of two Australian freshwater crayfish (Engaeus sericatus andGeocharax gracilis: Parastacidae) and four riparian land uses

1. Freshwater crayfish that burrow into river banks are likely to be affected by riparian land uses that affect soil conditions and vegetation cover. The aim of this research was to determine whether burrow densities of two crayfish species (Engaeus sericatus Clark and Geocharax gracilis Clark) were associated with riparian land use and vegetation type in three streams in south-west Victoria, Australia. 2. Four riparian land-use categories were studied on each stream: native forest blocks; thin strips of mature native vegetation, fenced, with pasture adjacent; riparian pasture areas, fenced, with no cattle access to the stream; pasture and cattle access to the water's edge. Crayfish burrows were counted and a range of water quality and riparian condition variables were measured. 3. Native forest areas were found to have more than twice the densities of freshwater crayfish burrows than other land uses, which did not differ. Native forest areas also had higher mean burrow mound heights but lower burrow activity levels. Riparian characteristics also differed between land uses. In particular, soil compaction was the lowest in native forest areas, which also had better riparian condition scores and water quality than pasture areas. 4. This study suggests that cattle grazing may have reduced populations of burrowing crayfish in these streams, and that subsequent fencing and the presence of remnant native vegetation may be insufficient to ameliorate these effects. Blocks of native forest that remain on these streams may act as an important refuge for these species in agricultural areas. Copyright © 2005 John Wiley & Sons, Ltd.

Low aggression in juvenile burrowing crayfish, Fallicambarus fodiens (Cottle, 1863) (Decapoda, Cambaridae)

[Informal observation suggested that Fallicambarus fodiens, which lives in close aggregations of mud burrows, exhibits less aggression than related epigean Cambarus spp. Interactions between size-matched, same sex pairs of F. fodiens were analysed in the laboratory. The analysis shows that these crayfish use behaviours similar to those used by Cambarus spp. in initiating agonistic interactions. However, approximately 84% of such interactions never proceed to the point of physical contact between the two opponents, whereas almost all comparable interactions in Cambarus spp. involve physical contact (fights). F. fodiens gather sufficient information for conflict resolution in a number of bouts of interaction comparable to that of other crayfish (differences not significant), but without physical interaction. Thus, these burrowing crayfish seem to have lower levels of aggression in comparison to more solitary, surface water crayfish species. This may be an adaptation for living in aggregations, where close co-habitation would be compromised by physical fighting and the subsequent extreme avoidance. Certaines observations ont suggere que Fallicambarus fodiens, qui habite dans des terriers vaseux agreges, est moins agressive que des especes epigees Cambarus proches. Les interactions entre paires de meme taille et meme sexe de F. fodiens ont ete analysees au laboratoire. Les analyses montrent que ces ecrevisses utilisent des comportements similaires a ceux de Cambarus spp. en debut d'interactions. Cependant, environ 84% de ces interactions n'arrivent pas jusqu'au contact physique entre les deux adversaires, alors que, au contraire, toutes les interactions comparables chez Cambarus spp. comprennent des contacts physiques (combats). F. fodiens rassemble assez d'information pour la resolution des conflits au cours d'un nombre d'assauts comparable au cas d'autres especes (difference non significative), mais sans contact physique. Donc, ces ecrevisses fouisseuses semblent presenter un niveau d'agressivite comparativement plus faible que celui d'ecrevisses plus solitaires, d'eaux de surface. Ce pourrait etre une adaptation leur permettant de vivre en groupes au niveau desquels la cohabitation serait compromise par des combats corporels et les comportements d'evitement qui en decouleraient., Informal observation suggested that Fallicambarus fodiens, which lives in close aggregations of mud burrows, exhibits less aggression than related epigean Cambarus spp. Interactions between size-matched, same sex pairs of F. fodiens were analysed in the laboratory. The analysis shows that these crayfish use behaviours similar to those used by Cambarus spp. in initiating agonistic interactions. However, approximately 84% of such interactions never proceed to the point of physical contact between the two opponents, whereas almost all comparable interactions in Cambarus spp. involve physical contact (fights). F. fodiens gather sufficient information for conflict resolution in a number of bouts of interaction comparable to that of other crayfish (differences not significant), but without physical interaction. Thus, these burrowing crayfish seem to have lower levels of aggression in comparison to more solitary, surface water crayfish species. This may be an adaptation for living in aggregations, where close co-habitation would be compromised by physical fighting and the subsequent extreme avoidance. Certaines observations ont suggere que Fallicambarus fodiens, qui habite dans des terriers vaseux agreges, est moins agressive que des especes epigees Cambarus proches. Les interactions entre paires de meme taille et meme sexe de F. fodiens ont ete analysees au laboratoire. Les analyses montrent que ces ecrevisses utilisent des comportements similaires a ceux de Cambarus spp. en debut d'interactions. Cependant, environ 84% de ces interactions n'arrivent pas jusqu'au contact physique entre les deux adversaires, alors que, au contraire, toutes les interactions comparables chez Cambarus spp. comprennent des contacts physiques (combats). F. fodiens rassemble assez d'information pour la resolution des conflits au cours d'un nombre d'assauts comparable au cas d'autres especes (difference non significative), mais sans contact physique. Donc, ces ecrevisses fouisseuses semblent presenter un niveau d'agressivite comparativement plus faible que celui d'ecrevisses plus solitaires, d'eaux de surface. Ce pourrait etre une adaptation leur permettant de vivre en groupes au niveau desquels la cohabitation serait compromise par des combats corporels et les comportements d'evitement qui en decouleraient.]

VERTICAL REDISTRIBUTION OF PEBBLES BY CRAYFISH IN MOLLISOL CATENAS OF CENTRAL ILLINOIS

Soil mixing by organisms (bioturbation) has an important influence on the distribution of rock fragments in soils. In east-central Illinois, pebbles were observed on the surfaces of loessal catenas. We hypothesized that surface pebbles are brought to the surface from the underlying glacial drift by burrowing crayfish. We predicted that (i) the spatial distribution of surface pebbles on catenas reflects crayfish habitat, (ii) pebbles are at least as abundant in crayfish chimneys (surface mound structures) as in the surrounding topsoil, (iii) pebbles are no larger than the cross-sectional diameter of crayfish burrows, (iv) the distribution of pebbles with regard to size class and material type does not differ between chimneys and surface soil samples, and (v) the vertical distribution of pebbles in the soil will reflect vertical mixing rather than a concentration at the soil surface. To test these predictions, surface pebbles were compared among catena members and crayfish chimneys and soil cores were collected and analyzed for pebble content and characteristics at multiple sites. The vertical distribution of pebbles in the soil profile was also studied at one site, and results were largely consistent with the hypothesis. However, the vertical distribution of pebbles suggested that near-surface pebbles subside at a greater rate than they are vertically mixed by crayfish, presumably due to bioturbation by other soil organisms. The study underscores the need to consider the influence of biota in addition to physical factors in interpreting the typically complex pathways of pedogenesis.

Reconnaissance of Upper Jurassic Morrison Formation ichnofossils, Rocky Mountain Region, USA: paleoenvironmental, stratigraphic, and paleoclimatic significance of terrestrial and freshwater ichnocoenoses

Seventy-five types of ichnofossils documented during a four-year reconnaissance study in the Upper Jurassic Morrison Formation demonstrate that highly diverse and abundant plants, invertebrates, and vertebrates occur throughout most of the Morrison or equivalent strata. Invertebrate ichnofossils, preserving the most environmentally and climatically sensitive in situ behavior of Morrison organisms, are in nearly all outcrops. Terrestrial ichnofossils record biotic processes in soil formation, indicating soil moisture and water-table levels. Freshwater ichnofossils preserve evidence of water depth, salinity, and seasonality of water bodies. Ichnofossils, categorized as epiterraphilic, terraphilic, hygrophilic, and hydrophilic (new terms), reflect the moisture regime where they were constructed. The ichnofossils are vertically zoned with respect to physical, chemical, and biological factors in the environment that controlled their distribution and abundance, and are expressed as surficial, shallow, intermediate, and deep. The sedimentologic, stratigraphic, and geographic distribution of Morrison ichnofossils reflects the environmental and climatic variations across the basin through time. Marginal-marine, tidal to brackish-water ichnofossils are mainly restricted to the Windy Hill Member. Very large to small termite nests dominate the Salt Wash Member. Similar size ranges of ant nests dominate the Brushy Basin Member. Soil bee nests dominate in the Salt Wash, decreasing in abundance through the Brushy Basin. Deeper and larger insect nests indicate more seasonal distribution of precipitation and rainfall. Shallower and smaller insect nests indicate either dry or wet substrate conditions depending on the nest architecture and paleopedogenic and sedimentologic character of the substrate. Trace–fossil indicators of flowing or standing water conditions are dominant in the Tidwell Member and in fluvial sandstones of the Salt Wash and Brushy Basin Members. Large communities of perennial, freshwater bivalve traces are abundant in the Tidwell and Brushy Basin Members but to a lesser extent in the Salt Wash Member. Shallow crayfish burrows, indicating a water-table level close to the surface (<1 m), are restricted to channel bank and proximal alluvial deposits in the Salt Wash, Recapture, and Brushy Basin Members. Sauropod, theropod, pterosaur, and other vertebrate tracks occur throughout the Morrison Formation associated with alluvial, lacustrine, and transitional-marine shoreline deposits. Ichnofossils and co-occurring paleosols in the Morrison reflect the local and regional paleohydrologic settings, which record the annual soil moisture budget and were largely controlled by the climate in the basin. Contributions to near-surface biologic systems by groundwater from distant sources were minor, except where the water table perennially, seasonally, or ephemerally intersected the ground-surface. The Jurassic Morrison Formation in the southern portion of the basin experienced a mosaic of seasonal climates that varied from a drier (Tidwell/Windy Hill deposition) to a wetter (lower and middle Salt Wash deposition) and slightly drier (upper Salt Wash deposition) tropical wet–dry climate, returning to a wetter tropical wet–dry climate near the end of Morrison deposition (Brushy Basin deposition). The northern part of the basin experienced similar trends across a mosaic of Mediterranean climate types. The range and mosaic pattern of wet–dry Morrison climates is analogous to the range of climates (and their seasonal variability) that dominates the African savanna today.

Thermoregulatory behavior of the crayfish Procambarus clarki in a burrow environment

The behavioral thermoregulation of the red swamp crayfish, Procambarus clarki, was investigated in its burrow environment. In the field, air and water temperatures within crayfish burrows fluctuated less compared with surface temperatures in the Mojave Desert. However, crayfish could still experience sub-optimal temperature regimes inside burrows. In the laboratory, P. clarki heated and cooled more rapidly in water than in air. In a thermal gradient, the crayfish selected a water temperature of 22 °C and avoided water temperatures above 31 °C and below 12 °C. Observations of behavior in an artificial burrow showed that P. clarki displayed three main shuttling behaviors between water and air in response to temperature. The number of bilateral emersions and emigrations, as well as the amount of time spent in air (in a 24 h period), were significantly greater at 34 °C than at 12, 16, 22 or 28 °C. This reflected an increased use of the behavioral thermoregulation at temperatures approaching the critical thermal maximum of this species. Upon migrating from 34 °C water into 38 °C air, crayfish body temperature decreased significantly. These periods of emersion were interspersed with frequent dipping in the water, allowing the crayfish to gain the benefits of evaporative cooling, without the physiological costs incurred by long-term exposure to air.

Tetrapod and Large Burrows of Uncertain Origin in Triassic High Paleolatitude Floodplain Deposits, Antarctica

Abstract Two types of large diameter burrows, recognized by non-overlapping size distributions, occur in high paleolatitude floodplain deposits of the Lower Triassic Fremouw Formation, Shackleton Glacier area, Antarctica. Type G (giant) burrows are gently dipping tunnels 8 to 19 cm in diameter. Type L (large) burrows are 2 to 6.5 cm in diameter, curved or subhorizontal tunnels that rarely branch; scratch markings on both burrow types generally are parallel or tangential to the long axis of the burrows. Type G burrows are interpreted as produced by tetrapods based on similarity in size, architecture, and surface markings to Permian burrows from South Africa that contain complete skeletons of therapsids. These are the first tetrapod burrows described from Antarctica. Type L burrows have characteristics of both fossil tetrapod and crayfish burrows, precluding identification of an unique producer. Triassic tetrapods, including therapsids, that lived in high southern latitudes probably burrowed to dampen the e...

Paleohydrologic and Stratigraphic Significance of Crayfish Burrows in Continental Deposits: Examples from Several Paleocene Laramide Basins in the Rocky Mountains

ABSTRACT Paleocene crayfish burrows are present locally in great abundance in the Greater Green River, Hanna, Wind River, and Piceance basins of Wyoming and Colorado. In the Washakie sub-basin of the Greater Green River Basin, burrows are found in (1) lenticular, cross-bedded sandstones of fluvial-channel origin, (2) massive sandstones and mudrocks of floodplain origin that surround and interfinger with the cross-bedded sandstones, and (3) thin, sandy ironstone beds of overbank and crevasse-splay origin. The burrows, which represent crayfish activity in proximal to distal floodplain settings, are assigned to Camborygma symplokonomos, C. eumekenomos, and C. litonomos on the basis of their architectural morphologies. C. araioklados is not present. Crayfish burrows are part of pedogenically modified channel and overbank deposits. In all the basins studied, burrows are abundant only in non-coal-bearing rocks. The presence of elongate burrows indicates that the landscape was imperfectly drained (on a seasonal basis), and the burrow depths suggest the paleo-water table was 1-4+ m below the paleosurface. Swampy conditions prevailed in areas where carbonaceous shales and coals formed, and thus crayfish did not construct deep burrows. The crayfish burrows and associated lithologies suggest a warm, humid, wet-seasonal climate. In the eastern Washakie Basin, the vertical and lateral distribution of burrows and their abundance reflect changes in the paleohydrologic regime over space and time. Burrow depth and overall abundance decreases towards local basin lowlands, where they are rare. The paleohydrologic regime coupled with a progressively less seasonal climate through time allowed the formation of the Cherokee coal zone in the late Paleocene. In an otherwise lithologically homogeneous, non-variegated deposits, stratigraphically significant surfaces may be indicated only by the tops of burrowed intervals and by other types of paleosols. The tops of burrowed intervals represent paleosurfaces of varying environmental stability on which there are different frequency and magnitude of sedimentation events. Immature cumulative paleosols characterized by less intensely burrowed beds or bedsets record higher sedimentation rates. More intensely burrowed beds or bedsets reflect the activity of many generations of crayfish; hence, the tops of these layers record longer durations of exposure and pedogenic modification with infrequent or no sedimentation. Paleosols represented by burrowed intervals, in conjunction with sandstone and mudrock stacking patterns, can be used to identify significant stratigraphic surfaces, such as parasequences and sequence boundaries, in fully continental environments.

Terrestrial hibernation in the northern cricket frog,Acris crepitans

We used laboratory experiments and field observations to explore overwintering in the northern cricket frog, Acris crepitans, in southern Ohio and Indiana. Cricket frogs died within 24 h when submerged in simulated pond water that was anoxic or hypoxic, but lived 8-10 days when the water was oxygenated initially. Habitat selection experiments indicated that cricket frogs prefer a soil substrate to water as temperature decreases from 8 to 2°C. These data suggested that cricket frogs hibernate terrestrially. However, unlike sympatric hylids, this species does not tolerate extensive freezing: only 2 of 15 individuals survived freezing in the -0.8 to -2.6°C range (duration 24-96 h). Cricket frogs supercooled when dry (mean supercooling point -5.5°C; range from -4.3 to -6.8°C), but were easily inoculated by external ice at temperatures between -0.5 and -0.8°C. Our data suggested that cricket frogs hibernate terrestrially but are not freeze tolerant, are not fossorial, and are incapable of supercooling in the presence of external ice. Thus we hypothesized that cricket frogs must hibernate in terrestrial sites that adequately protect against freezing. Indeed, midwinter surveys revealed cricket frogs hibernating in crayfish burrows and cracks of the pond bank, where wet soils buffered against extensive freezing of the soil.

Effects of Fire, Competition and Soil Disturbances on Regeneration of a Carnivorous Plant (Drosera capillaris)

Abstract Although chronically low soil fertility is widely recognized as an important selection pressure on carnivorous plants, the effects of other potentially important selection pressures, such as natural disturbances, have largely been ignored. In this study, I examined the effects of fire and removal of live plants and litter on seedling establishment of Drosera capillaris (pink sundew), a small insectivorous plant common to wet, nutrient-poor pine savannas of the southeastern United States. I also examined the effects of soil disturbances associated with crayfish burrows on mortality. Fires occurring during the winter of 1996/1997 increased the density, growth and establishment of seedlings during the growing season of 1997. In addition to fires, local removal of established plants and their associated litter greatly increased seedling density and growth within savannas. The proportion of rosettes that flowered at sites not burned recently (>1 year before) was nearly twice that at sites burned more ...

Quantitative ichnology of triassic crayfish burrows (Camborygma eumekenomos): Ichnofossils as linkages to population paleoecology

Analysis of 201 crayfish burrows (Camborygma eumekenomos) from three fluvial beds of the Chinle Formation (Upper Triassic, Utah, U.S.A.) provides results consistent with knowledge of Holocene crayfish ecology. Thus, many aspects of their population ecology may have remained unchanged since the early Mesozoic. A significant increase in crayfish size away from the fluvial channel reflects size (age) segregation along an environmental gradient. The high lateral (within‐bed) variation in burrow density may have been caused by spatial heterogeneity in water table and soil moisture levels. In each of the three analyzed beds, the burrows record a single ecologic generation of a monospecific crayfish population. The three beds differ in terms of the mean burrow diameter (this may reflect differences either in the average size/age of the resident crayfish or in the lateral extent of sampling). However, the overall shape of the burrow‐size distribution is similar for all three beds (unimodal and close‐to‐normal). This reflects similar paleohydrologic and paleoecologic conditions through time, as substantiated by independent ichnologic and sedimentologic evidence.

Paleozoic-Mesozoic crayfish from Antarctica: Earliest evidence of freshwater decapod crustaceans

Discovery of an Early Permian claw from Antarctica extends the fossil record of crayfish by ∼65 m.y. and demonstrates that decapod crustaceans had radiated into freshwater habitats by the late Paleozoic. Burrows in Lower Triassic rocks of Antarctica are among the oldest apparently constructed by crayfish. Their morphology is similar to modern crayfish burrows, and this demonstrates that burrowing behavior was established early in the evolution of this group. The new discoveries show that the earliest Permian crayfish were distributed in high paleolatitudes of southernmost Pangea, where they lived in freshwater lakes fed by glacial meltwater. Modern crayfish habitat, used as a guide to crayfish temperature tolerance, indicates that summer temperatures of streams and lakes near the South Pole that supported the crayfish probably reached 10–20 °C during Permian-Triassic interglacial intervals.

Sun Hats and Ichnofabrics: Fourth International Ichnofabric Workshop, San Salvador Island, Bahamas, March 15-22, 1997

Sun Hats and Ichnofabrics: Fourth International Ichnofabric Workshop, San Salvador Island, Bahamas, March 15-22, 1997