Generalized spectral light scatter models of diverse bacterial colony morphologies

An optical forward‐scatter model was generalized to encompass the diverse nature of bacterial colony morphologies and the spectral information. According to the model, the colony shape and the wavelength of incident light significantly affect the characteristics of a forward elastic‐light‐scattering pattern. To study the relationship between the colony morphology and the scattering pattern, three‐dimensional colony models were generated in various morphologies. The propagation of light passing through the colony model was then simulated. In validation of the theoretical modeling, the scattering patterns of three bacterial genera, Staphylococcus, Exiguobacterium and Bacillus, which grow into colonies having convex, crateriform and flat elevations, respectively, were qualitatively compared to the simulated scattering patterns. The strong correlations observed between simulated and experimental patterns validated the scatter model. In addition, spectral effect on the scattering pattern was studied using the scatter model, and experimentally investigated using Staphylococcus, whose colony has circular form and convex elevation. Both simulation and experiment showed that changes in wavelength affected the overall pattern size and the number of rings.     

The power and efficiency of brood incubation in queenless microcolonies of bumble bees (Bombus terrestris L.)

1. Ground‐nesting colonies of bumble bees incubate their brood at > 30 °C if floral forage provides sufficient energy and the thermogenic power of the colony can counteract cool soil conditions. To explore the basis of incubation, the thermogenic power and sugar consumption of orphaned nests of bumble bee workers (microcolonies) were investigated under laboratory conditions. 2. This study tested experimentally the effect of variation in worker number (ranging from four to 12 adults) on a microcolony's capacity to regulate brood temperature and recover from acute cold exposure. Microcolonies were provided with ad libitum sugar syrup and minimal insulation and maintained at an ambient temperature of c. 25 °C. Energy conversion efficiency was estimated by comparing sugar consumption with the power required for artificial incubation. The joint energetics of foraging and incubation were modelled in wild colonies to explore the effect of colony size and landscape quality on thermoregulation. 3. The results showed that all sizes of microcolonies regulated brood temperature at c. 31 °C under laboratory conditions, which required 96 mW of thermogenic power. It was estimated that individual workers of B. terrestris generated an incubatory power of 35 mW. The smallest microcolonies had the highest conversion efficiency (57%), apparently because few workers were required for incubation. 4. Modelling indicated that small microcolonies of three to seven adult workers have the capacity for normal brood incubation in the wild, but that the minimum viable colony size increases as floral forage becomes poorer or more distant. 5. These preliminary findings suggest the feasibility of identifying the minimum conditions (forage quality, soil temperature, and colony size) necessary for brood incubation by queenright colonies in the wild.     

In vitro and In vivo Effects of Some Fungicides against the Chickpea Blight Pathogen, Ascochyta rabiei

The effects of various fungicides on mycelial growth and spore germination of Ascochyta rabiei were determined by incorporating them into potato dextrose agar and measuring colony diameter and observing colony growth and spore germination at 20 ± 2°C. Eight fungicides prevented spore germination of the pathogen at concentrations of 0.125–2 μg/ml, three hindered mycelial growth at 2–4 μg/ml and seven failed to inhibit mycelial growth even at 128 μg/ml. The reference fungicide for the pathogen, chlorothalonil, stopped conidial germination at low rates but did not prevent mycelial growth at 128 μg/ml. Thirteen fungicides were tested against seed infections of the pathogen, and benomyl + thiram, carbendazim and carbendazim + chlorothalonil seed treatments gave more than 85% inhibition on both vacuum‐infiltrated and naturally infected seeds. Coating the seeds with polymers did not increase the effectiveness of fungicides. Three fungicides; (azoxystrobin, chlorothalonil and mancozeb), gave the highest protection in the field but protection decreased with increased inoculum pressure. Addition of humic acid to fungicide suspensions did not affect their performance.     

On the sensitivity of forward scattering patterns from bacterial colonies to media composition

Morphology of colonies is important for taxonomy and diagnostics in microbiology where the response to environmental factors is sensitive enough to support discrimination. In this research, we analyzed the forward scattering patterns of individual Escherichia coli K12 colonies when agar hardness and nutrition levels were varied from the control sample. As the agar concentration increased from 1.2% to 1.8%, the diameter of the forward scattering patterns also increased for the same experimental condition which reflects that the colony thickness at the apex is greater for increased agar concentrations. Regarding nutrition, increasing dextrose resulted in smaller mean colony diameters while the mean diameters of the colonies were proportional to the yeast extract concentration up to 0.5%. The result reveals that ±0.3% agar concentration from the control sample is sufficient to create variations in the scattering patterns. For nutrition –0.25% of yeast extract showed significant variations while +0.25% from control sample showed minimal variations. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Large-scale phytogeographical patterns in East Asia in relation to latitudinal and climatic gradients

Aim This paper aims at determining how different floristic elements (e.g. cosmopolitan, tropical, and temperate) change with latitude and major climate factors, and how latitude affects the floristic relationships between East Asia and the other parts of the world. Location East Asia from the Arctic to tropical regions, an area crossing over 50° of latitudes and covering the eastern part of China, Korea, Japan and the eastern part of Russia. Methods East Asia is divided into forty‐five geographical regions. Based on the similarity of their world‐wide distributional patterns, a total of 2808 indigenous genera of seed plants found in East Asia were grouped into fourteen geographical elements, belonging to three major categories (cosmopolitan, tropical and temperate). The 50°‐long latitudinal gradient of East Asia was divided into five latitudinal zones, each of c. 10°. Phytogeographical relationships of East Asia to latitude and climatic variables were examined based on the forty‐five regional floras. Results Among all geographical and climatic variables considered, latitude showed the strongest relationship to phytogeographical composition. Tropical genera (with pantropical, amphi‐Pacific tropical, palaeotropical, tropical Asia–tropical Australia, tropical Asia–tropical Africa and tropical Asia geographical elements combined) accounted for c. 80% of the total genera at latitude 20°N and for c. 0% at latitude 55–60°N. In contrast, temperate genera (including holarctic, eastern Asia–North America, temperate Eurasia, temperate Asia, Mediterranean, western Asia to central Asia, central Asia and eastern Asia geographical elements) accounted for 15.5% in the southernmost latitude and for 80% at 55–60°N, from where northward the percentage tended to level off. The proportion of cosmopolitan genera increased gradually with latitude from 5% at the southernmost latitude to 21% at 55–60°N, where it levelled off northward. In general, the genera present in a more northerly flora are a subset of the genera present in a more southerly flora. Main conclusions The large‐scale patterns of phytogeography in East Asia are strongly related to latitude, which covaries with several climatic variables such as temperature. Evolutionary processes such as the adaptation of plants to cold climates and current and past land connections are likely responsible for the observed latitudinal patterns.     

Ontogeny and phyletic size change in living and fossil lemurs

Lemurs are notable for encompassing the range of body‐size variation for all primates past and present—close to four orders of magnitude. Benefiting from the phylogenetic proximity of subfossil lemurs to smaller‐bodied living forms, we employ allometric data from the skull to probe the ontogenetic bases of size differentiation and morphological diversity across these clades. Building upon prior pairwise comparisons between sister taxa, we performed the first clade‐wide analyses of craniomandibular growth allometries in 359 specimens from 10 lemuroids and 176 specimens from 8 indrioids. Ontogenetic trajectories for extant forms were used as a criterion of subtraction to evaluate morphological variation, and putative adaptations among sister taxa. In other words, do species‐level differences in skull form result from the differential extension of common patterns of relative growth? In lemuroids, a pervasive pattern of ontogenetic scaling is observed for facial dimensions in all genera, with three genera also sharing relative growth trajectories for jaw proportions (Lemur, Eulemur, Varecia). Differences in masticatory growth and form characterizing Hapalemur and fossil Pachylemur likely reflect dietary factors. Pervasive ontogenetic scaling characterizes the facial skull in extant Indri, Avahi, and Propithecus, as well as their larger, extinct sister taxa Mesopropithecus and Babakotia. Significant interspecific differences are observed in the allometry of indrioid masticatory proportions, with variation in the mechanical advantage of the jaw adductors and stress‐resisting elements correlated with diet. As the growth series and adult data are largely coincidental in each clade, interspecific variation in facial form may result from selection for body‐size differentiation among sister taxa. Those cases where trajectories are discordant identify potential dietary adaptations linked to variation in masticatory forces during chewing and biting. Although such dissociations highlight selection to uncouple shared ancestral growth patterns, they occur largely via transpositions and retention of primitive size‐shape covariation patterns or relative growth coefficients. Am. J. Primatol. 72:161–172, 2010. © 2009 Wiley‐Liss, Inc.     

Patterns and drivers of Araucaria araucana forest growth along a biophysical gradient in the northern Patagonian Andes: Linking tree rings with satellite observations of soil moisture

Araucaria araucana (Araucaria) is a long‐lived conifer growing along a sharp west–east biophysical gradient in the Patagonian Andes. The patterns and climate drivers of Araucaria growth have typically been documented on the driest part of the gradient relying on correlations with meteorological records, but the lack of in situ soil moisture observations has precluded an assessment of the growth responses to soil moisture variability. Here, we use a network of 21 tree‐ring width chronologies to investigate the spatiotemporal patterns of tree growth through the entire gradient and evaluate their linkages with regional climate and satellite‐observed surface soil moisture variability. We found that temporal variations in tree growth are remarkably similar throughout the gradient and largely driven by soil moisture variability. The regional spatiotemporal pattern of tree growth was positively correlated with precipitation (r = 0.35 for January 1920–1974; P < 0.01) and predominantly negatively correlated with temperature (r = ?0.38 for January–March 1920–1974; P < 0.01) during the previous growing season. These correlations suggest a temporally lagged growth response to summer moisture that could be associated with known physiological carry‐over processes in conifers and to a response to moisture variability at deeper layers of the rooting zone. Notably, satellite observations revealed a previously unobserved response of Araucaria growth to summer surface soil moisture during the current rather than the previous growing season (r = 0.65 for 1979–2000; P < 0.05). This new response has a large spatial footprint across the mid‐latitudes of the South American continent (35°–45°S) and highlights the potential of Araucaria tree rings for palaeoclimatic applications. The strong moisture constraint on tree growth revealed by satellite observations suggests that projected summer drying during the coming decades may result in regional growth declines in Araucaria forests and other water‐limited ecosystems in the Patagonian Andes.     

The Impact of Annual and Seasonal Rainfall Patterns on Growth and Phenology of Emergent Tree Species in Southeastern Amazonia,Brazil

Understanding tree growth in response to rainfall distribution is critical to predicting forest and species population responses to climate change. We investigated inter‐annual and seasonal variation in stem diameter by three emergent tree species in a seasonally dry tropical forest in southeast Pará, Brazil. Annual diameter growth rates by Swietenia macrophylla demonstrated strong positive correlation with annual rainfall totals during 1997–2009; Hymenaea courbaril growth rates demonstrated weak positive correlation, whereas Parkia pendula exhibited weak negative correlation. For both Swietenia and Hymenaea, annual diameter growth rates correlated positively and significantly with rainfall totals during the first 6 mo of the growing year (July to December). Vernier dendrometer bands monitored at 4‐wk intervals during 3–5 yr confirmed strong seasonal effects on stem diameter expansion. Individuals of all three species expanded in unison during wet season months and were static or even contracted during dry season months. Stems of the deciduous Swietenia contracted as crowns were shed during the early dry season, expanded slightly as new crowns were flushed, and then contracted further during 3–5 wk flowering periods in the late dry season by newly mature crowns. The three species’ physiographic distribution patterns at the study site may partially underlie observed differences in annual and seasonal growth. With most global circulation models predicting conditions becoming gradually drier in southeast Amazonia over the coming decades, species such as Swietenia that perform best on the ‘wet end’ of current conditions may experience reduced growth rates. However, population viability will not necessarily be threatened if life history and ecophysiological responses to changing conditions are compensatory.     

Abiotic–biotic controls on the origin and development of spicular sinter: in situ growth experiments, Champagne Pool, Waiotapu, New Zealand

Abiotic–biotic mechanisms of microstromatolitic spicular sinter (geyseritic) initiation and development were elucidated by in situ growth experiments at Champagne Pool (75 °C, pH 5.5). Siliceous sinter formed subaerially on glass slides placed along the margin of the hot spring. Environment–silica–microbe interactions were revealed by periodic collections of incremental sinter growth that formed under a range of environmental conditions including quiescence vs. wave turbulence, and wind–evaporation vs. steam–condensation. Sinter surfaces were intermittently colonized by voluminous networks of filamentous micro‐organisms, with submicron diameters, that provided an extensive surface area for silica deposition. The subaerial distribution of sinter and its textures reflected micron‐ to centimetre‐scale differences in environmental conditions, particularly relating to the balance between wave‐supplied dissolved silica and its precipitation, forced by cooling and evaporation. A continuum of sinter textures formed, representing rates of silica precipitation that either out‐paced biofilm growth or regulated the structural development of biofilms, and hence also the nature of microbially templated sinter. Massive laminae of porous, filamentous‐network sinter and/or fenestrae (up to 10's of microns in thickness and diameter) formed at relatively low rates of silica deposition (approximately 0.2 mg slide^?1 day^?1). At high rates (>1.9 mg slide^?1 day^?1), densely packed, granular or nonporous sinter formed, with filament networks disappearing into the siliceous matrix and becoming imperceptible under scanning electron microscopy (SEM). Furthermore, spicules were nucleated by filamentous microcolonies, where their discrete conical morphologies were preserved by accretion of thin sinter laminae. Microstromatolitic spicular growth ensued at fluctuating low to high rates of silica precipitation. Greater apical sinter build‐up, and hence upward polarity, resulted from focused microbial recolonization and progressively greater subaerial exposure at microspicule tips. The biogenic origin of spicular sinter at Champagne Pool clearly demonstrates that micron‐scale biofilms, displaying self‐organization patterns common to both biofilms and microbial mats, can be an essential factor in shaping characteristic centimetre‐scale sinter macrostructures. These findings suggest that a biogenic origin for geyserites elsewhere should also be considered. Moreover, results corroborate the supposition that microbially generated surface roughness may be significant for stromatolite morphogenesis in cryptic Precambrian carbonates.     

Molecular systematics of Brassica and allied genera in subtribes Brassicinae, Raphaninae, Moricandiinae, and Cakilinae (Brassicaceae, tribe Brassiceae); the organization and evolution of ribosomal gene families

DNA restriction endonuclease fragment analysis was used to obtain new information on the genomic organization of ribosomal DNA (rDNA) of Brassica and allied genera. The total genomic DNA of 95 accessions of 52 species representing 16 genera was restricted with six enzymes, and the restriction fragments were probed with three ribosomal clones (pTA71, Ver 18‐6, and Ver 6‐5). Eleven repeat unit length classes were recognized. The repeat unit size classes of 8.9 kb and 9.5 kb were observed most commonly, being represented in 17 and 14 species, respectively. The restriction enzyme SacI produced three to six (generally three) bands with detectable hybridization to the probe pTA71. This probe–enzyme combination indicated a remarkable uniformity amongst Brassica and allied genera in the coding region of repeat units. By contrast, an extensive size variation in the restriction fragments could be localized in the intergenic spacer (IGS) region. Eleven IGS‐containing length variants were detected. Complex hybridization patterns, resulting from extensive repeat unit heterogeneity and taxon‐specific methylation of one or more cleavage sites, were obtained with the EcoRI + pTA71 combination. The relative homologies between the coding regions were evident from the presence of 1.5 kb in all the taxa, and 0.4‐, 1.3‐, and 1.7‐kb fragments in 33, 27, and 24 species, respectively. The SacI + pTA71 and EcoRI + pTA71 combinations were generally able to distinguish taxa both within and between genera. Three restriction endonuclease digests probed with three ribosomal clones yielded essentially identical fragmentation patterns across all the accessions within the cultivated species Brassica campestris, B. oleracea, and B. juncea. In B. napus, three and seven accessions exhibited restriction profiles similar to one and both diploid progenitor species, respectively. Overall, rDNA repeat unit length polymorphism showed good correlation with the cytodeme‐based classification of Brassica and allied genera. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157 , 545–557.     

Comparative growth and metabolism of gelatinous colonies of three cyanobacteria,Nostoc commune,Nostoc pruniforme and Nostoc zetterstedtii,at different temperatures

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Early development and allometric shifts during the ontogeny of a marine catfish (Cathorops spixii‐Ariidae)

This study assessed whether the developmental series of the ariid Cathorops spixii (Agassiz, 1829) is related to growth patterns during its early ontogeny. The main morphological events of C. spixii were studied from the newly neurula embryo (6.99±0.69 mm TL) to juveniles (53.38±14.43 mm TL) in order to characterize and corroborate patterns of ontogenetic allometries. Prior to hatching, embryos were well‐developed, with an ossified axial and appendicular skeleton. Embryos grew slowly, but positive allometric growth was observed in head width (β₁ = 1.65) and eye diameter (β₁ = 1.59). This seems to be related to the fast development of sensory organs such as otoliths, Weberian apparatus, lenses, nostrils and barbels during the embryonic period when eggs are under the care of adult males. After hatching, mouth‐brooding free‐embryos grew horizontally isometric, except for the snout length that presented quick growth related to the end of endogenous feeding (β₁ = 1.73). Slow growth was observed in head width (β₁ = 0.44) and eye diameter (β₁ = 0.26), taking into account that sensory organs are formed in free‐embryos. The end of the yolk‐sac period was characterized by a direct change from free‐embryo to juvenile, without a true larval period. Juveniles are characterized by growth patterns nearly isometric in all body regions, suggesting that they already bear most of characteristics of adult fish. The quick growth of morphometric variables that are related to sensorial organs before hatching and the increase in horizontal growth after the first 6 weeks (hatched free‐embryos) reflect developmental priorities during the earliest stages where important sensorial organs are being developed for juvenile survival strategies.     

Production of cell–cell signalling molecules by bacteria isolated from human chronic wounds

Aim: To (i) identify chronic wound bacteria and to test their ability to produce acyl‐homoserine‐lactones (AHLs) and autoinducer‐2 (AI‐2) cell–cell signalling molecules and (ii) determine whether chronic wound debridement samples might contain these molecules. Methods and Results: Partial 16S rRNA gene sequencing revealed the identity of 46 chronic wound strains belonging to nine genera. Using bio‐reporter assays, 69·6% of the chronic wound strains were inferred to produce AI‐2, while 19·6% were inferred to produce AHL molecules. At least one strain from every genus, except those belonging to the genera Acinetobacter and Pseudomonas, were indicated to produce AI‐2. Production of AI‐2 in batch cultures was growth‐phase dependent. Cross‐feeding assays demonstrated that AHLs were produced by Acinetobacter spp., Pseudomonas aeruginosa and Serratia marcescens. Independent from studies of the bacterial species isolated from wounds, AHL and/or AI‐2 signalling molecules were detected in 21 of 30 debridement samples of unknown microbial composition. Conclusion: Chronic wound bacteria produce cell–cell signalling molecules. Based on our findings, we hypothesize that resident species generally produce AI‐2 molecules, and aggressive transient species associated with chronic wounds typically produce AHLs. Both these classes of cell–cell signals are indicated to be present in human chronic wounds. Significance and Impact of the Study: Interbacterial cell–cell signalling may be an important factor influencing wound development and if this is the case, the presence of AHLs and AI‐2 could be used as a predictor of wound severity. Manipulation of cell–cell signalling may provide a novel strategy for improving wound healing.     

Isolation and Molecular Identification of Colletotrichum gloeosporioides Causing Brown Spot Disease of Camellia oleifera in Hainan of China

Colletotrichum gloeosporioides is an important pathogen that causes widespread brown spot disease on the leaves of the tea‐oil tree (Camellia oleifera) in China. This study was designed to isolate, identify and characterize this fungal pathogen, based on morphology, molecular characteristics and pathogenicity. One pathogenic fungus, named CCG4, was isolated from wild‐type Camellia oleifera of Hainan Province. Colonies were regular circular in shape with 50–60 mm diameter after 5 days of incubation at 28°C on potato dextrose agar (PDA) medium, and woolly with a small amount of jacinth pigment; the colony colour changed from white to black during later stages of infection. The mycelium produced was branched and septate. Conidia were cylindrical‐truncate, oblong‐obtuse to doliform, colourless with 1–2 hyaline oil globules and 4.5–5.3 μm × 7.7–17.5 μm. The sporodochia were cushion‐shaped. The pathogen was identified as Colletotrichum gloeosporioides on the basis of morphological characteristics and internal transcribed spacer sequence, which showed 100% query cover and 99% similarity to the sequence Colletotrichum gloeosporioides JN887341.1 , from a pathogenic fungus known to cause brown spot disease of Camellia oleifera.     

The structured diversity of specialized gut symbionts of the New World army ants

Symbiotic bacteria play important roles in the biology of their arthropod hosts. Yet the microbiota of many diverse and influential groups remain understudied, resulting in a paucity of information on the fidelities and histories of these associations. Motivated by prior findings from a smaller scale, 16S rRNA‐based study, we conducted a broad phylogenetic and geographic survey of microbial communities in the ecologically dominant New World army ants (Formicidae: Dorylinae). Amplicon sequencing of the 16S rRNA gene across 28 species spanning the five New World genera showed that the microbial communities of army ants consist of very few common and abundant bacterial species. The two most abundant microbes, referred to as Unclassified Firmicutes and Unclassified Entomoplasmatales, appear to be specialized army ant associates that dominate microbial communities in the gut lumen of three host genera, Eciton, Labidus and Nomamyrmex. Both are present in other army ant genera, including those from the Old World, suggesting that army ant symbioses date back to the Cretaceous. Extensive sequencing of bacterial protein‐coding genes revealed multiple strains of these symbionts coexisting within colonies, but seldom within the same individual ant. Bacterial strains formed multiple host species‐specific lineages on phylogenies, which often grouped strains from distant geographic locations. These patterns deviate from those seen in other social insects and raise intriguing questions about the influence of army ant colony swarm‐founding and within‐colony genetic diversity on strain coexistence, and the effects of hosting a diverse suite of symbiont strains on colony ecology.     

Behavior ofPseudomonas fluorescens within the hydrodynamic boundary layers of surface microenvironments

Phase, darkfield, and computer-enhanced microscopy were used to observe the surface microenvironment of flow cells during bacterial colonization. Microbial behavior was consistent with the assumptions used previously to derive surface colonization kinetics and to calculate surface growth and attachment rates from cell number and distribution. Surface microcolonies consisted of closely packed cells. Each colony contained 2ⁿ cells, where n is the number of cell divisions following attachment. Initially, cells were freely motile while attached, performing circular looping movements within the plane of the solid-liquid interface. Subsequently, cells attached apically, maintained a fixed position on the surface, and rotated. This type of attachment was reversible and did not necessarily lead to the formation of microcolonies. Cells became irreversibly attached by progressing from apical to longitudinal attachment. Longitudinally attached cells increased in length, then divided, separated, moved apart laterally, and slid next to one another. This resulted in tight cell packing and permitted simultaneous growth and adherence. After approximately 4 generations, individual cells emigrated from developing microcolonies to recolonize the surface at new locations. Surface colonization byPseudomonas fluorescens can thus be subdivided into the following sequential colonization phases: motile attachment phase, reversible attachment phase, irreversible attachment phase, growth phase, and recolonization phase.     

Staphylococcus aureus SigB activity promotes a strong fibronectin–bacterium interaction which may sustain host tissue colonization by small‐colony variants isolated from cystic fibrosis patients

Genes encoding cell‐surface proteins regulated by SigB are stably expressed in Staphylococcus aureus small‐colony variants (SCVs) isolated from cystic fibrosis (CF) patients. Our hypothesis is that CF‐isolated SCVs are locked into a colonization state by sustaining the expression of adhesins such as fibronectin‐binding proteins (FnBPs) throughout growth. Force spectroscopy was used to study the fibronectin–FnBPs interaction among strains varying for their SigB activity. The fibronectin–FnBPs interaction was described by a strength of 1000 ± 400 pN (pulling rate of 2 μm s^?1), an energetic barrier width of 0.6 ± 0.1 Å and an off‐rate below 2 × 10^?4 s^?1. A CF‐isolated SCV highly expressed fnbA throughout growth and showed a sustained capacity to bind fibronectin, whereas a prototypic strain showed a reduced frequency of fibronectin‐binding during the stationary growth phase when its fnbA gene was down‐regulated. Reduced expression of fnbA was observed in sigB mutants, which was associated with an overall decrease adhesion to fibronectin. These results suggest that the fibronectin–FnBPs interaction plays a role in the formation of a mechanically resistant adhesion of S. aureus to host tissues and supports the hypothesis that CF‐isolated SCVs are locked into a colonization state as a result of a sustained SigB activity.     

Growth characteristics of Protoheliolites norvegicus (Tabulata; Upper Ordovician; Estonia)

Protoheliolites is an early heliolitine coral characterized by closely spaced corallites separated in places by sparse coenenchyme. Growth characteristics in the type species, P. norvegicus, are revealed by detailed analysis based on serial peels and thin sections of coralla from the uppermost Katian of north‐western Estonia. Colonies of this species had a strong ability to recover from damage and partial mortality, resulting in various forms of rejuvenation, regeneration, fusion and reorganization of corallites; in some cases, this involved relatively large areas of undifferentiated soft parts. The shells of commensal cornulitids became enclosed in host coralla during colony growth. Coralla of P. norvegicus exhibit distinctive growth cycles due to responses to seasonal changes. The production of new corallites by coenenchymal increase usually occurred in low‐density bands, in which corallites generally display round to subrounded transverse outlines. In high‐density bands, the corallites became crenulated, their wall thickness increased, septal development was more pronounced, and the amount of coenenchyme increased. In addition to these cyclomorphic changes, there were significant astogenetic changes during growth. Compared with the early stage of colony development, distinctive characteristics in the late astogenetic stage include a decrease in the growth rate of the colony, better coordination among corallites, maximum development of corallite crenulations and septa in high‐density bands, more numerous coenenchymal tubules and a greater proportion of corallum area occupied by coenenchyme. In general, the role of polyps in determining morphological characteristics of individual corallites, such as tabularium area, corallite crenulations and wall thickness, was subordinate to the astogeny of the colony. Growth characteristics including colony‐wide coordination of polyp behaviour and subjugation of individuals to restore the colony following damage suggest a strong astogenetic control and high level of colony integration. Protoheliolites probably arose from a heliolitine genus rather than from a nonheliolitine group as some authors have proposed.