Principles of early ontogeny in the rugose corals: a critical review

It has been suggested that septal furrows in the Palaeozoic rugose corals are secondary in comparison both to growth lines and to the septal blades inside calices. The leading role of furrows as an indicator of septal increase is thus questioned. Septa are always grouped in quadrants but their increase is generally towards the cardinal septum. The arrangement of the contratingent minor septa seems to be independent of the increase in septal furrows. Hence, the growth of the polyp's skeleton may have started from an aseptal cup.     

Vassiljukia,a new colonial rugose coral from the Early Visean (Mississippian) of the Donets Basin (Ukraine) and NW Turkey

The cerioid colonial coral previously described as Lithostrotion columnariformis from the Early Visean of the Donets Basin (Ukraine) is here reattributed to the new genus Vassiljukia. This genus is introduced for colonial amygdalophylloid developing a stable cerioid habitus. It differs from amygdalophylloid proto-colonies by its ability to produce second generation offsets. This ability is proposed here as a definition to differentiate proto-colonial stages from genuine colonies within the rugose corals. Vassiljukia columnariformis is also known from equivalent strata of northwestern Turkey where it occurs with the oldest cerioid Lithostrotion and Ceriodotia. The origin and affinity of Vassiljukia columnariformis within the Amygdalophyllidae are also discussed.     

Paleoecology of a Pennsylvanian encrusting colonial rugose coral in south Guizhou, China

The well-preserved Pennsylvanian encrusting colonial rugose coral Ivanovia is widespread and easily observed in south Guizhou, China. There are three common types of hard substrate encrusted by Ivanovia: in situ carbonate hardgrounds, carbonate hardground clasts, and calcareous bioclasts. Thin, spreading sheets are the most common growth form of Ivanovia in the study region. Ivanovia employed peripheral, medial and mixed growth strategies to occupy a sufficient living space on the substrate. It favored a shallow, warm, and clear marine environment within the photic zone and had a high tolerance of water movement. Ivanovia was generally smothered and covered by mud in the studied area. The Ivanovia fossil communities in south Guizhou are characterized by a low species diversity conforming to the typical evolutionary pattern of hard substrate marine communities in the Carboniferous.     

Extinctions and migrations of Devonian rugose corals in the Eastern Americas Realm

Oliver, W. A., Jr. 1990 04 15: Extinctions and migrations of Devonian rugose corals in The Eastern Americas Realm. Lethaia , Vol. 23 , pp. 167–178. Oslo. ISSN 0024–1164.
Detailed plotting of the stratigraphic ranges of Devonian rugose coral genera within the Eastern Americas Realm reveals new information about the extinctions and migrations of this largely endemic fauna. There were significant faunal turnovers in the Lochkovian, middle Eifelian and late Givetian. as well as in the often discussed late Frasnian. The late Givetian turnover was nearly as great as the Frasnian one. Inward migration was principally from western North America, and the greatest influxes were during the carly Givetian and Frasnian. It seems likely that there were several separate incursions and that some genera were introduced to the east two, or even three times.     

Lucky rugose corals on crinoid stems: unusual examples of subepidermal epizoans from the Devonian of Morocco

Berkowski, B & Klug, C. 2011: Lucky rugose corals on crinoid stems: unusual examples of subepidermal epizoans from the Devonian of Morocco. Lethaia, Vol. 45, pp. 24–33. In the fossil record, evidence for true epizoans, i.e. living animals inhabiting other living host‐animals, is rather rare. A host reaction is usually needed to proof the syn vivo‐settling of the epizoan. Herein, we provide a first report of such an epizoan biocoenosis from various strata of the Early Devonian of Hamar Laghdad, the world‐renowned Moroccan mud‐mound locality. In this case, solitary rugose corals settled as larvae on crinoid stems, perhaps at a spot where the epidermis was missing for some reason (injury, disease). Both the crinoid and the coral began to grow around each other. By doing so, the affected crinoid columnals formed a swelling, where ultimately only an opening slightly larger than the coral orifice remained. We discuss both macroecological and small‐scale synecological aspects of this biocoenosis. The coral profited from its elevated home because it reached into more rapid currents providing the polyp with more food than at the densely populated seafloor, which was probably covered by a coral‐meadow around the mounds and hydrothermal vents. □Corals, crinoids, Early Devonian, epizoans, Morocco, Rugosa.     

Large dwellers of the Silurian Halysites biostrome: rhizosessile life strategies of cystiphyllid rugose corals from the Llandovery of Gotland

An exceptionally well‐preserved, unusual biostrome composed of the framebuilding cateniform tabulate coral Halysites catenularius (Linnaeus, 1767) bears an assemblage of the relatively large solitary cystiphyllid rugosan Cystiphyllum visbyense Wedekind, 1927. The corallites of solitary cystiphyllids are embedded within the ranks of the halysitid colonies, which developed on a soft, muddy substrate and in relatively turbid water. The cystiphyllid larvae successively settled mostly on the ranks of halysitid colonies and on colonies of the tiny phaceloid rugose coral Nanophyllum ramosum Johannessen, 1995, whereas calice‐in‐calice recruitment was not successful for these cystiphyllid corals. Further growth of C. visbyense was supported by rhizoid structures, which were most frequently developed on the cardinal (convex) side of the corallite. The process of formation of the rhizoid structures is here discussed and explained in detail, showing that they were formed by the extension of the basal ectodermal tissue of the polyp. The cystiphyllids, which settled on the walls of living corallites of halysitid colonies, used sweeper tentacles to kill the smaller polyps of the colony to maintain the space around them and expand. Hence, they ultimately used the halysitid colonies only as a hard substrate to stabilize their position on the soft muddy sediment.     

Sediment as a possible source of food for corals

Reef building corals are generally believed to require clear, nutrient-poor water. Yet, paradoxically, coral reefs are among the most productive marine ecosystems in the world. This paradox is commonly explained by the coral's ability to utilize a number of food resources, including zooplankton, phytoplankton, dissolved organic matter and photosynthetic products derived from their endosymbiotic algae, the zooxanthellae. Sedimentation is a known stressor for corals, inhibiting most feeding modes in various ways. However, evidence for enhanced sediment deposition on certain corals, induced by their morphologies, as well as for sediment ingestion by some corals, has led us to examine the use of sediment as a possible source of food for corals in addition to the other, known food sources. Our experiments with fluorescently labelled sediment show transfer of labelled organic matter from the sediment into the cells of the solitary coral Fungia horrida Dana 1846. The results provide the first direct evidence for the ability of a coral to digest the sediment's organic fraction. These results may indicate a positive role of sediment, which up until now was considered to have only deleterious effects on corals.     

Bioluminescence of colonial radiolaria in the western Sargasso Sea

Colonial radiolaria (Protozoa: Spumellarida) were a conspicuous feature in surface waters of the Sargasso Sea during the April (1985) Biowatt cruise. The abundance of colonies at the sea surface at one station was estimated to be 23 colonies · m⁻².Bioluminescence by colonial radiolaria, representing at least six taxa, was readily evoked by mechanical stimuli and measured by fast spectroscopy and photon-counting techniques. Light emission was deep blue in color (peak emissions between 443 and 456 nm) and spectral distributions were broad (average half bandwidth of 80 nm). Single flashes were 1–2 s in duration at ≈23 °C, with species-dependent kinetics which were not attributed to differences in colony morphology, since colonies similar in appearance could belong to different species (even families) and display different flash kinetics. Although the presence of dinoflagellate symbionts was confirmed by the presence of dinoflagellate marker pigments in the colonies, luminescence in the radiolaria examined most likely did not originate from symbiotic dinoflagellates because of (1) differences in the emission spectra, (2) unresponsiveness to low pH stimulation, (3) differences in flash kinetics and photon emission of light emission, and (4) lack of light inhibition.The quantal content of single flashes averaged 1 × 10⁹ photons flash⁻¹, and colonies were capable of prolonged light emission. The mean value of bioluminescence potential based on measurements of total mechanically stimulated bioluminescence was 1.2 × 10¹¹ photons · colony⁻¹. It is estimated that colonial radiolaria are capable of producing ≈2.8 × 10¹² photons · m⁻² of sea surface. However, this represented only 0.5% of in situ measured bioluminescence potential.     

基于相关系数的水文相依性变异分级方法——以自回归模型为例

水文过程演变存在时间相依性,含有相依成分的水文序列无法满足水文计算中的一致性假设,给水问题研究带来诸多困难.针对水文序列相依性变异这一现象,以自相关模型为例,提出基于相关系数的水文相依性变异分级方法.该方法通过计算相依成分与原序列之间的相关系数,并选取合理的相关系数阈值,将相依性变异程度分为无变异、弱变异、中变异、强变异、巨变异.通过推导相关系数与序列各阶自相关系数之间的公式,说明相关系数主要取决于1阶到p阶自相关系数的大小,从而阐明分级方法的理论基础.以一阶和二阶自回归模型为例,利用统计试验验证了公式的合理性,并说明了相关系数和自相关系数的联系.将所提分级方法应用于3个实测径流序列进行分析,结果显示水文过程常常存在相依性与随机性并存的现象.     

Reconfiguration as a Prerequisite for Survival in Highly Unstable Flow-Dominated Habitats

Unstable and mechanically demanding habitats like wind-exposed open fields or the wave-swept intertidal require rapid adaptive processes to ensure survival. The mechanism of passive reconfiguration was analyzed in two plant models exposed to irregular flow of water or air, two species of the brown seaweed Durvillaea and the giant reed Arundo donax. Irrespective of the surrounding media and the subsequent Reynolds numbers (Re ~ 10⁵ - 10⁷), reconfiguration seems to be the key strategy for streamlining to avoid overcritical drag-induced loads. This passive mechanism is also discussed in the context of the requirement of a maximized surface area for light interception, so that morphological adaptations to rapid reconfiguration represent at least a bifactorial optimization. Both tested plant models exhibited the same principles in streamlining. At a specific threshold value, the proportionality between drag forces and flow velocity can be reduced from the second power close to an almost linear relation. This empirically derived relation could be characterized by a figure of merit or Vogel number (B). A value close to B = -1, resulting in a linear increase of drag force with velocity, was found at higher velocities for both the seaweeds and the giant reed, as well as for a variety of plants described in the literature. It is therefore concluded that the ability to reduce velocity-dependent drag force to a linear relation is a potentially important adaptation for plants to survive in unstable flow-dominated habitats.     

The Fractal Dimension as a Measure of the Quality of Habitats

Habitat fragmentation produces isolated patches characterized by increased edge effects from an originally continuous habitat. The shapes of these patches often show a high degree of irregularity: their shapes deviate significantly from regular geometrical shapes such as rectangular and elliptical ones. In fractal theory, the geometry of patches created by a common landscape transformation process should be statistically similar, i.e. their fractal dimensions and their form factors should be equal. In this paper, we analyze 49 woodlot fragments ( Pinus sylvestris L. ) in the Belgian Kempen region to study the direct relationship between a transformation process and the concomitant patch geometry. Although the fractal dimension of the woodlots is scattered (i.e. they are not statistically similar), the perimeter-area relation of the fragments is characterized by a single, 'dimension-like' exponent. This exponent suggests a certain shape homogeneity among the patches, which is confirmed by the absence of hierarchical levels associated with sharp increases of the fractal dimension at scale transitions. The interaction of different natural (soil factor, vegetation type) and anthropogenic (afforestation, urbanization) processes during patch development is assumed to have generated this feature. Comparison of the area and perimeter fractal dimension with an ecological index for habitat quality, the interior-to-edge ratio, shows that the fractal dimension is suitable for predicting interior habitat presence, which is more likely for patches with smooth perimeters and compact areas. The ratio of the area to the perimeter fractal dimension confirms this observation, with high values for high interior-to-edge ratios, characteristic for regularly shaped patches.     

Identification of the endostyle as a stem cell niche in a colonial chordate

Stem cell populations exist in "niches" that hold them and regulate their fate decisions. Identification and characterization of these niches is essential for understanding stem cell maintenance and tissue regeneration. Here we report on the identification of a novel stem cell niche in Botryllus schlosseri, a colonial urochordate with high stem cell-mediated developmental activities. Using in vivo cell labeling, engraftment, confocal microscopy, and time-lapse imaging, we have identified cells with stemness capabilities in the anterior ventral region of the Botryllus' endostyle. These cells proliferate and migrate to regenerating organs in developing buds and buds of chimeric partners but do not contribute to the germ line. When cells are transplanted from the endostyle region, they contribute to tissue development and induce long-term chimerism in allogeneic tissues. In contrast, cells from other Botryllus' regions do not show comparable stemness capabilities. Cumulatively, these results define the Botryllus' endostyle region as an adult somatic stem cell niche.     

Palaeoenvironmental analysis based on rugose corals and microfacies: a case study at La Cornuda section (early Serpukhovian, Guadiato Area, SW Spain)

Combined analysis of microfacies and rugose coral features provides a useful tool for palaeoenvironmental studies in areas where outcrops are not appropriate for field observations. A detailed study of Serpukhovian rugose corals from La Cornuda section (Guadiato Area, SW Spain) by means of thin sections allowed the identification of environments where they lived. All corals were collected in unit 1 of the section where three different but intimately connected environments have been identified. Corals developed mainly in small mounds built jointly by microbial communities, algae and corals. Some corals also lived in calcareous shoals mainly composed of echinoderm plates. Finally, some corals occur in Oncoidal limestone that represents a shallow ramp, but they were mainly transported from shoals and mounds.     

Rugose corals and associated carbonate microfossils from the Brigantian (Mississippian) of Castelsec (Montagne Noire, southern France)

The disused quarry east of Castelsec offers a view of shallow-marine carbonates of the poorly known Uppermost Mississippian of the Montagne Noire. At Castelsec, sections are studied in two characteristic facies types (bioclastic wackestone and microbial dominated boundstone) of the Upper Mississippian. The succession is rich in rugose corals and carbonate microfossils. Six genera with seven species belonging to a rugose coral fauna consisting of at least eight genera with several species are described herein; Dibunophyllum castelsecensis sp. nov. is described as new. Twenty-seven carbonate microfossils of different groups have been identified. The Castelsec succession is Brigantian in age, based on the stratigraphic occurrence of rugose corals, foraminifers, and calcareous algae observed in both sections. The rugose coral fauna shows relationships with the well-known fauna of northwestern Europe and the Ouralian-Asian Province. Typical elements of northwestern Europe are missing at Castelsec and vice versa. This differentiation between north and south is interpreted as responses to different palaeolatitudes and tectonic settings.