Ontogenetic changes in the capacity of the coral Pocillopora damicornis to originate branches

Most colonial corals vary intraspecifically in growth forms, and the diversity in branching morphology is especially striking. While the effects of environmental factors on growth forms have been studied, the genetic control of coral branching patterns has received little attention. The discovery of ontogenetic changes in the capacity to originate branching would set the stage for studies of how branch formation is genetically controlled. During experiments investigating contact reactions in the coral Pocillopora damicornis, we observed that young colonies derived from settled planulae and colonies regenerated from adult branch tips assumed different growth forms. Young colonies formed at least one branch from the central region of the colony, while colonies regenerated from adult branch tips (3-5 mm long) did not form branches during the 9-month observation period. This pattern was invariable, regardless of the types and outcomes of the contact experiments or the orientation of the branch tips. However, some fragments taken from 1- or 2-year-old colonies formed branches. This suggests that the rate of branch formation in P. damicornis colonies decreases with age. These findings will facilitate investigations of the mechanism of coral branch formation at the molecular level.     

Morphogenesis in Trichoderma: Induction of conidiation by narrow-beam illumination of restricted areas of the fungal colony

Trichoderma colonies were illuminated with a narrow light beamhaving a fixed length of 0.5 mm and varing widths. Spot conidiationcould be induced by a beam 0.1 mm or greater in width. Resultsindicated that some kind of joint perception of photoinductiontakes place among adjacent mycelial fields. (Received April 22, 1971; )     

The occurrence of two bill morphs of prions Pachyptila vittata on Gough Island

Prions Pachyptila are abundant seabirds in the Southern Ocean that have been used to infer environmental change, but this relies on an understanding of their morphological diversity. Species limits among prions are largely defined by the size and structure of their bills. The broad-billed prion P. vittata, which breeds at temperate islands in the central South Atlantic Ocean and around New Zealand, is the largest species with adult bill widths averaging 21–22 mm. We report local differences in bill sizes on Gough Island, with typical adults breeding in some areas and narrower-billed birds in other areas (average bill width 18–19 mm, although at one site there was a second mode at bill widths of 16–17 mm). The narrow-billed birds have slightly shorter bills, heads and wings (averaging 1–2 % smaller than typical adult broad-billed prions), but the difference in bill width is much more marked (15 %). The small-billed birds differ from typical broad-billed prions in having blue colouration in the upper mandible and are similar in size to MacGillivray’s prion P. [salvini/vittata] macgillivrayi from Amsterdam and St Paul islands in the temperate Indian Ocean. The occurrence of two prion morphs on Gough Island raises intriguing questions about their ecology and systematics. Small-billed birds breed 3 months later than large-billed birds, suggesting that they are a separate species, not an example of bill polymorphism.     

Leaf-cutting ants as road engineers: the width of trails at branching points in <Emphasis Type="Italic">Atta cephalotes</Emphasis>

We used a simple engineering principle, which suggests that the width of a road needed for a smooth traffic flow is proportional to the peak traffic volume (“engineering hypothesis”), to analyze the adaptive significance of trail width at branching points in the leaf-cutting ant Atta cephalotes. Since the flow of outgoing ants splits at trail bifurcations and merges when ants return to the nest through the same paths, the sum of branch widths should equal the width of the trail section upstream of the bifurcation. We measured the width of branches and their preceding trail section and also performed field measurements and manipulations to analyze ant flow, number of collisions, and ant speed in different trail sectors. Contrary to the prediction of the “engineering hypothesis”, the sum of branch widths was larger than the width of the trail immediately before the bifurcation. Our data contradict the “trail addition hypothesis” and support the “border effect hypothesis” to explain this pattern. First, the width of the widest branch was smaller than the width of the trail upstream of the bifurcation, an unexpected result if one branch is merely the continuation of the basal trail. Second, ants collided with obstacles more often in the margin than in the central portion of the trail, relocated ants from central to margin trail sectors reduced their speed, and ant flow was higher in the central sections of the trail. Since the delaying effect of trail margins increases as the trail width decreases, ants may build branches wider than expected to reduce the border effect. The delaying effect of trail margins should be included in the analysis of costs and benefits to fully understand the adaptive value of the design of ant trail networks.     

Determinate growth and modularity in a gorgonian octocoral

Growth rates of branches of colonies of the gorgonian Pseudopterogorgia elisabethae were monitored for 2 years on a reef at San Salvador Island, Bahamas. Images of 261 colonies were made at 6-month intervals and colony and branch growth analyzed. Branch growth rates differed between colonies and between the time intervals in which the measurements were made. Colonies developed a plumelike morphology through a pattern of branch origination and determinate growth in which branch growth rates were greatest at the time the branch originated and branches seldom grew beyond a length of 8 cm. A small number of branches had greater growth rates, did not stop growing, and were sites for the origination of subsequent "generations" of branches. The rate of branch origination decreased with each generation of branching, and branch growth rates were lower on larger colonies, leading to determinate colony growth. Although colonial invertebrates like P. elisabethae grow through the addition of polyps, branches behave as modules with determinate growth. Colony form and size is generated by the iterative addition of branches.     

Comparison of radial increment and volume growth in stems and roots of Quercus petraea

Dendrochronological studies dealing with roots, stems and branches are very rare or often take the form of short notes. The difficulties of detecting rings and of quantifying the radial growth in roots have already been described for various species. In oak the anatomical root structure differs from stemwood. The roots are radial-porous or diffuse-porous, and there is often no clear distinction between individual rings. In our study visual and radiographic techniques were used to examine radial increment in roots of sessile oak (Quercus petraea L.) which was compared with radial growth in branches and along the stem. Coarse roots were cut from four 30- to 34-year-old trees that had been uprooted mechanically and disks were taken at different distances from the stem-root base. Ring widths were measured in the stem at height of 0.3 m, at breast height (1.3 m), beneath the crown, in branches of the crown, and in roots every 20 cm. The ring widths were cross-dated, and the heterogeneity of growth within a root and within the root system were analysed. Asymmetric growth frequently occurred in roots so that ovals, I-beam and T-beam shapes were developed. With the method used in our study the annual growth layers close to the central cylinder could be distinguished as well as beneath the bark. Pointer years were detected in all sections of the tree and permitted correction of ring widths in roots. Root system, stem and branch showed a basic similarity in their radial sequence of ring width. The annual biomass increment was weaker and more variable with several consecutive changes in the roots than in the stems. The root/shoot ratio reached a minimum rather early, beginning at the cambial age of 20 years. This revised version was published online in June 2006 with corrections to the Cover Date.     

Branch junctions and the flow of water through xylem in Douglas-fir and ponderosa pine stems

Water flowing through the xylem from the roots to the leaves of most plants must pass through junctions where branches have developed from the main stem. These junctions have been studied as both flow constrictions and components of a hydraulic segmentation mechanism to protect the main axes of the plant. The hydraulic nature of the branch junction also affects the degree to which branches interact and can respond to changes in flow to other branches. The junctions from shoots of two conifer species were studied, with particular emphasis on the coupling between the downstream branches. Flow was observed qualitatively by forcing stain through the junctions and the resulting patterns showed that flow into a branch was confined to just part of the subtending xylem until a considerable distance below the junction. Junctions were studied quantitatively by measuring flow rates in a branch before and after flow was stopped in an adjacent branch and by measuring the hydraulic resistance of the components of the junction. Following flow stoppage in the adjacent branch, flow into the remaining branch increased, but considerably less than predicted based on a simple resistance analogue for the branch junction that assumes the two branches are fully coupled. The branches downstream from a junction, therefore, appear to be limited in their interconnectedness and hence in their ability to interact.     

Determining the mechanical properties of hazel forks by testing their component parts

The ability to accurately predict the load-bearing capacity of tree forks would improve tree surveying and tree surgery techniques and assist with the biomechanical modelling of a tree’s structure. In this study, the bending strength of forks of hazel (Corylus avellana L.) was investigated by assessing the mechanical contributions from three component parts of each fork. Intact forks and ones in which either central or peripheral xylem lying under the branch bark ridge at the apex of the forks had been removed were subjected to tensile tests. The bending strength of these forks was compared with that of the arising branches by carrying out a three-point bending test on the smaller arising branches of the intact specimens. All forks failed in tension, splitting between the arising branches. By removing the centrally placed xylem, constituting approximately a fifth of the width of the fracture surface, the forks’ bending strength was reduced by around 32 %, while removing the outer four-fifths reduced the forks’ bending strength by 49 %. Intact forks had around 74 % of the maximum bending strength of the smaller arising branch. It is concluded that the tensile strength of the centrally placed xylem at the apex of a tree fork is a critical strengthening component. This helps to explain the weakness of forks with included bark, which lack this component. This study concludes that tree forks should not by default be considered flaws in a tree’s structure.     

Ants,Stem Borers,and Pubescence in Endospermum in Papua New Guinea1

The stems of the ant-plant, Endospermum labios Schodde, serve as colonization sites for the ant, Camponotus quadriceps F. Smith. They are also subject to damage by insect borers. We sampled young E. labios trees in distutbed forest to compare evidence of stem boring insect and stem miner damage in plants with and without colonies of C. quadriceps. Dissections of a subsample of plants showed that dipteran stem borers and stem miner damage were significantly more common in plants lacking C, quadriceps colonies than in plants with established colonies. Evidence from these dissections and from field counts of meristem damage caused by emerging borers suggested that coleopteran stem borers were also more abundant when ants were not present. In addition to the incidence of stem boring insects and ant colonies, we examined relative levels of leaf pubescence by measuring trichome density and leaf size for E. labios trees. We found that trichome density was significantly greater in trees with evidence of prior shoot damage (presumably from stem borer emergence at the meristem) but was not significantly related to the presence or absence of an ant colony. This prompted us to compare trichome density on leaves of nearby small trees and of different branches of the same tree, pairing a stem/branch that appeared damaged with one that appeared healthy. Trichome densities on leaves from damaged stems and branches were significantly greater than were trichome densities on healthy branches and stems. Based on these empirical data, we present several possible explanations for the patterns of association between ants, stem borers, and pubescence. Although feeding preference tests with a common folivore showed no effect of trichome densities on leaves, we suggest further study on how trichomes may affect ovipositing stem borers.     

Spontaneous mutation frequency and molecular mechanisms of Shigella flexneri fluoroquinolone resistance under antibiotic selective stress

The incidence of fluoroquinolone-resistant Shigella strains has risen rapidly, presumably in response to ciprofloxacin antibiotic stress. Understanding the molecular mechanisms underlying this resistance phenotype is critical to developing novel and effective therapeutic strategies. In this study, the frequency of ciprofloxacin-induced mutation was measured in antibiotic resistance genes (gyrA, gyrB, parC, parE, marOR, and marA) of Shigella flexneri. The S. flexneri 2a strain 301 was cultured on Luria–Bertani agar plates containing one of seven different ciprofloxacin concentrations (range: 0.03125–2 μg mL^?1). Resistant colonies were selected for gene-targeted sequencing analysis; the identified point mutations were subsequently confirmed by insertion into antibiotic cassette plasmids and growth under ciprofloxacin stress. The results demonstrated that the seven different ciprofloxacin concentrations produced dose-dependent frequencies of spontaneous mutations: 10^?8 (0.03125 and 0.0625 μg mL^?1), 10^?9 (0.125 μg mL^?1), and <10^?9 (0.25, 0.5, 1, 2 μg mL^?1). PCR sequencing of the ten randomly selected resistant colonies (minimum inhibitory concentrations (MICs) of 0.125 μg mL^?1, n = 5 and 0.25 μg mL^?1, n = 5) revealed that all colonies had mutations in the gyrA gene at either codon 83 (Ser83 → Leu) or 87 (Asp87 → Tyr or → Gly), both of which were confirmed at MIC of 0.125 μg mL^?1. None of the spontaneous mutation colonies exhibited gyrB, parC, parE, marOR, or marA mutations. In conclusion, S. flexneri is normomutable under ciprofloxacin antibiotic stress and fluoroquinolone resistance by spontaneous mutation occurs at a low rate. Codon mutations gyrA 83 and/or gyrA 87 cause a 4-fold increase in the ciprofloxacin MIC, and may represent the natural mechanism of fluoroquinolone resistance.     

Phorid fly parasitism rates vary between individual colonies of the leaf-cutting ant Atta laevigata

1. Phorid flies are important natural enemies of leaf-cutting ants. Female phorids lay eggs in the worker ants' bodies and the parasitoid larvae feed on the host's internal tissues.
2. Here we investigated the parasitism rates by four species of phorids when attacking individual Atta laevigata colonies at three different field sites in order to further understand the host-parasitoid relationship.
3. There were distinct variations in parasitism rates when comparing phorid species attacking individual colonies. In 13 of the colonies sampled, parasitism by Apocephalus attophilus or Eibesfeldtphora erthali was predominant. However, in four of the colonies, Myrmosicarius grandicornis and Apocephalus vicosae were the predominant species.
4. Variations in parasitism rates by the four phorid species were investigated in relation to the size of the potential hosts that had been collected from the foraging trails of each colony.
5. When correlating the size of potential hosts to phorid species, ants with head capsule widths of >2 mm were predominantly parasitized by A. vicosae and E. erthali. Smaller ants, with head capsule widths of 2 mm or less, were predominantly parasitized by A. attophilus and M. grandicornis.
6. The highest parasitism rates by E. erthali were observed in individual colonies that had the highest proportions of large workers on the trails.
7. Although almost half the size of E. erthali, A. attophilus parasitized both large (head capsule width > 2 mm) and small workers (<2 mm). This was related to the fact that between 1 and 16 larvae can develop within an individual host, depending on host size.
8. M. grandicornis parasitized smaller workers (mean head capsule width = 2 mm) as these phorids are themselves small and only one larva develops within each host.
9. This study demonstrated that the parasitism profiles of individual A. laevigata colonies were related to the size of foragers on the trails.

     

Critical Evaluation of Branch Polarity and Apical Dominance as Dictators of Colony Astogeny in a Branching Coral

The high morphological resemblance between branching corals and trees, can lead to comparative studies on pattern formation traits, best exemplified in plants and in some cnidarians. Here, 81 branches of similar size of the hermatypic coral Stylophora pistillata were lopped of three different genets, their skeletons marked with alizarin red-S, and divided haphazardly into three morphometric treatment groups: (I) upright position; (II) horizontal position, intact tip; and (III) horizontal position, cut tip. After 1 y of in-situ growth, the 45 surviving ramets were brought to the laboratory, their tissues removed and their architectures analyzed by 22 morphological parameters (MPs). We found that within 1 y, isolated branches developed into small coral colonies by growing new branches from all branch termini, in all directions. No architectural dissimilarity was assigned among the three studied genets of treatment I colonies. However, a major architectural disparity between treatment I colonies and colonies of treatments II and III was documented as the development of mirror structures from both sides of treatments II and III settings as compared to tip-borne architectures in treatment I colonies. We did not observe apical dominance since fragments grew equally from all branch sides without documented dominant polarity along branch axis. In treatment II colonies, no MP for new branches originating either from tips or from branch bases differed significantly. In treatment III colonies, growth from the cut tip areas was significantly lower compared to the base, again, suggesting lack of apical dominance in this species. Changes in branch polarity revealed genet associated plasticity, which in one of the studied genets, led to enhanced growth. Different genets exhibited canalization flexibility of growth patterns towards either lateral growth, or branch axis extension (skeletal weight and not porosity was measured). This study revealed that colony astogeny in S. pistillata is a regulated process expressed through programmed events and not directly related to simple energy trade-off principles or to environmental conditions, and that branch polarity and apical dominance do not dictate colony astogeny. Therefore, plasticity and astogenic disparities encompass a diversity of genetic (fixed and flexible) induced responses.     

Propagation of the threatened staghorn coral Acropora cervicornis: methods to minimize the impacts of fragment collection and maximize production

Coral reef restoration methods such as coral gardening are becoming increasingly considered as viable options to mitigate reef degradation and enhance recovery of depleted coral populations. In this study, we describe several aspects of the coral gardening approach that demonstrate this methodology is an effective way of propagating the threatened Caribbean staghorn coral Acropora cervicornis: (1) the growth of colonies within the nursery exceeded the growth rates of wild staghorn colonies in the same region; (2) the collection of branch tips did not result in any further mortality to the donor colonies beyond the coral removed for transplantation; (3) decreases in linear extension of the donor branches were only temporary and donor branches grew faster than control branches after an initial recovery period of approximately 3–6 weeks; (4) fragmentation did not affect the growth rates of non-donor branches within the same colony; (5) small branch tips experienced initial mortality due to handling and transportation but surviving tips grew well over time; and (6) when the growth of the branch tips is added to the regrowth of the fragmented donor branches, the new coral produced was 1.4–1.8 times more than new growth in undisturbed colonies. Based on these results, the collection of small (2.5–3.5 cm) branch tips was an effective propagation method for this branching coral species resulting in increased biomass accumulation and limited damage to parental stocks.     

Colony growth responses of the Caribbean octocoral, Pseudopterogorgia elisabethae, to harvesting

Abstract. Colonies of the branching Caribbean gorgonian Pseudopterogorgia elisabethae were subjected to partial mortality at 2 sites in the Bahamas to study how colony growth responds to disturbances such as harvesting, grazing, and storm damage. Colonies were clipped so that either 4 branches or 10 branches remained. Growth rates of branches were then monitored over 1 year and compared with nearby unclipped colonies. No significant differences were found between branch extension rates among the 3 treatments. Extension rates of newly formed branches were significantly greater in all treatments than among branches present at the start of the experiment. Per capita branching rates were greater on the more severely clipped colonies and were smallest on control colonies. The absolute number of branches that became mother branches did not differ among treatments. Colonies clipped so that 4 and 10 branches remained had the same average number of mother branches per colony, and there was no significant difference between treatments in the average number of new branches formed on the colonies. Per capita branching rates were significantly different among treatments only because the relative proportion of branches that became mother branches was higher in colonies with four branches than in treatments with more initial branches. Total growth (cumulative growth on all branches) was not significantly different between the 2 clipped treatments. Many of the control colonies suffered extensive damage, which may have obscured the comparison of clipped and unclipped treatments; however, within the range of these clipping treatments, differing levels of partial mortality did not lead to different recovery rates. The lack of treatment effects is particularly relevant to assessing the effects of harvest techniques on the recovery and productivity of harvested, naturally occurring, colonies.     

The possible roles of nutrient deprivation and auxin repression in apical control

Apical control is the suppression of growth in lower branches by a higher dominant branch or leader shoot. We investigated possible mechanisms involved in this developmental response in three widely diverse species (Japanese morning glory, Ipomoea nil, hybrid poplar, Populus trichocarpa, × P. deltoides, and Douglas-fir, Pseudotsuga menziesii). The following two hypotheses were tested: (1) the mineral nutrient-deprivation hypothesis, which is that the continued growth of the lower branches is repressed by the diversion of nutrients to the upper dominating branch or shoot, and (2) the auxin-repression hypothesis, which is that auxin produced in the upper dominating branch or shoot moves down to the lower branches where continued growth is repressed. The results of experiments involving the manipulation of available nutrients by dominant branch removal and fertilization were consistent with the first hypothesis for morning glory, poplar, and for second- or third flushing of lateral branches in Douglas-fir. The results of the experiments involving auxin (NAA, 1-naphthalene acetic acid) replacement treatments on decapitated shoots bearing growing lateral branches were inconsistent with the second hypothesis in morning glory, poplar and in first-flushing Douglas-fir. However, despite concerns about possible NAA toxic effects, there was evidence of auxin repression of second flushing in Douglas-fir. Overall, the data supported a significant role for nutrient availability but not for auxin repression in apical control of morning glory and poplar. In Douglas-fir, apical control in first-flushing lateral branches from over-wintered buds was largely insensitive to both nutrient availability and auxin repression; however, second flushing was sensitive to both.     

Distribution and Abundance of Fauna on Living Tissues of Two Brazilian Hermatypic Corals (Mussismilia hispida (Verril 1902) and Siderastrea stellata Verril, 1868)

This study describes the distribution and abundance patterns of the associate fauna on the living surface of the corals Siderastrea stellata Verril, 1868 and Mussismilia hispida (Verril 1902) using a non-destructive method, on the northern coast of Rio de Janeiro State. For each coral species, infestation density and proportions of infested colonies, colonies attached and unattached to the substrate were estimated. A total of 474 colonies of S. stellata and 452 colonies of M. hispida were examined. The barnacle Ceratoconcha floridana (Pilsbry, 1931) was the dominant coral associate found, followed by gall-crabs of the family Cryptochiridae Paulson, 1875 and the bivalve Lithophaga bisulcata (d’Orbigny, 1842). Both coral species presented similar patterns of infestation dominance. S. stellata colonies were more commonly infested and showed a greater mean infestation density of 0.62 ind/cm² at Armação dos Búzios, whereas M. hispida colonies had infestation densities of only 0.20 ind/cm². Infestation density does not appear to impact negatively on corals of Armação dos Búzios. A clear negative relationship between the number of associates in the coral colony and coral size was found. Evidently abundance and frequency of occurrence of associated fauna is highly related to coral community structure and composition and the results highlight the importance of local scale studies.     

Nest relocation in the ant Pheidole dentata

We studied nest relocation in the ant Pheidole dentata, a common species in the southern US, by following colonies for 6 weeks. We correlated probability of relocation with several abiotic and biotic environmental factors, such as air temperature, humidity, leaf litter depth (LLD), nest type and presence of phorid fly parasitoids. Colonies moved often, on average every 16.2 days. By the end of our study, fewer than 5 % of colonies marked at the start remained in their original nests. Only 3.1 % of colonies returned to a previously used nest. The mean distance of relocation was 0.76 ± 0.73 m. Colonies nested in a variety of locations, such as in the ground, by tree trunks, under rocks and inside wood. Several factors affected probability of relocation. Higher LLD and vapor pressure deficit (VPD) increased probability of relocation. Probability of relocation varied by nest type, by plot and week of study. We found no evidence that surface cover or rain affected relocation behavior. Colonies appear to avoid nests that become dry by nesting against tree trunks. Phorid fly abundance correlated negatively with VPD, yet it had no effect on colonies’ likelihood of relocation. We discuss other implications of frequent nest relocations.     

Skeletal development in <Emphasis Type="Italic">Acropora palmata</Emphasis> (Lamarck 1816): a scanning electron microscope (SEM) comparison demonstrating similar mechanisms of skeletal extension in axial versus encrusting growth

Many Acropora palmata colonies consist of an encrusting basal portion and erect branches. Linear growth of the skeleton results in extension along the substrate (encrusting growth), lengthening of branches (axial growth) and thickening of branches and crust (radial growth). Scanning Electron Microscopy is used to compare the mechanisms of skeletal extension between encrusting growth and axial growth. In encrusting growth, the distal margin of the skeleton lacks corallites (which develop about 1 mm from the edge); in contrast, in axial growth, axial corallites along the branch tip form the distal portion of the skeleton. In both locations, the distal margin of the skeleton consists of a lattice-like structure composed of rods that extend from the body of the skeleton and bars that connect these rods. An actively extending skeleton is characterized by sharply pointed rods and partially developed bars. Distal growth of rods (and formation of bars) is effected by the formation of new sclerodermites. Each sclerodermite begins with the deposition of fusiform crystals (that range in length from 1 to 5 μm). These provide a surface for nucleation and growth of spherulitic tufts, clusters of short (<1 μm long) aragonite needles. The needles that are oriented perpendicular to the axis of the skeletal element (rod or bar), and perpendicular to the overlying calicoblastic epithelium, continue extension to appear on the surface of the skeleton as 10–15 μm wide bundles (of needle tips) called fasciculi. However, some crusts that abut competitors for space have a different morphology of skeletal elements (rods and bars). The distal edge of these crusts terminates in blunt coalescing rods, and bars that are fully formed. Absence of fusiform crystals, lack of sharply pointed rods and bars, and full development of sclerodermites characterize a skeletal region that has ceased, perhaps only temporarily, skeletal extension.     

A radicle solution: morphology and biomechanics of the Eucalyptocrinites ‘root’ system

Eucalyptocrinites is one the most common and familiar mid‐Palaeozoic crinoids and is the exemplar of a form with dendritic radicular holdfasts. American museums have hundreds of specimens of Eucalyptocrinites holdfasts from the Silurian Waldron Shale of Indiana and Kentucky, USA. The radix (‘root’) system of Eucalyptocrinites can be described as comprised of links (branches) that meet at nodes. Measured values include the x‐ and y‐coordinates of the nodes, the distances of the nodes from the stem, the angles between branches, branch length and branch width. Rose diagrams show clearly that the root systems are not isotropic but have preferred orientations. Branch angles are highly variable, but cluster around 60 degrees. Branch lengths and distal branch widths are relatively constant, but branch width increases variably towards the column. The branching pattern can be modelled as a self‐similar (‘fractal’) structure. Several specimens labelled as Eucalyptocrinites show a distinct fivefold symmetry without branching and very likely represent a different taxon. The Eucalyptocrinites radix system, along with the probably stiff dististele, most likely functioned as a rigid plate that resisted rotational forces due to currents acting on the crown. Upstream radicles experienced tension, whereas downstream roots were compressed. This force distribution may explain the observed anisotropies in radix morphology. The ‘roots’ of Eucalyptocrinites and other crinoids have long been compared with the root systems of plants. Although there are superficial similarities, there are fundamental differences.     

Estimating density of a forest-dwelling bat: a predictive model for Rafinesque’s big-eared bat

Data on species distribution and abundance are the foundation of population ecology. However, due to difficulties in surveying bats, abundance estimates for tree-roosting microchiropterans are non-existent. Therefore, our objective was to develop methods for estimating colony abundance and density, taking as our model Rafinesque’s big-eared bat Corynorhinus rafinesquii, a species of conservation concern found in cypress-gum swamps of the southeastern United States. We searched 123 transects at eight study sites in the Coastal Plain of Georgia, USA to locate and characterize diurnal summer roosts of C. rafinesquii. We modeled the relationship between the number of bat colonies and landscape-scale habitat variables with zero-inflated negative binomial regression and used Akaike’s information criterion to select the most parsimonious models. We generated a predictive density map to identify areas of high colony density and to estimate overall abundance. Colony density was predicted by the duration of wetland flooding, wetland width, and study site. Application of the regression model to a GIS indicated there were 3,734 colonies containing 6,910 adult bats on the eight study sites. Predicted density ranged from 0.07 colonies/ha and 0.07 adult bats/ha in saturated wetlands to 0.47 colonies/ha and 1.18 adult bats/ha in semi-permanently flooded wetlands. This study is the first to estimate density and abundance of forest-dwelling microchiropterans over a large area. Such data can serve as a baseline for future work on population trends in C. rafinesquii. In addition, our approach could be replicated for other bat species with moderately cryptic roosts.