Constraints on the formation of colonies of the extant azooxanthellate scleractinian coral Dendrophyllia arbuscula

Sentoku, A. & Ezaki, Y. 2011: Constraints on the formation of colonies of the extant azooxanthellate scleractinian coral Dendrophyllia arbuscula. Lethaia, Vol. 45, pp. 62–70. Scleractinia display a variety of growth forms, whether zooxanthellate or azooxanthellate, as the consequence of the combined effects of both intrinsic and extrinsic factors. New modules arise in colonial corals through asexual reproduction, including budding and division. The azooxanthellate, branching dendrophylliid Dendrophyllia arbuscula van der Horst 1922 , is a good species to investigate intrinsic regularities in budding, because: (1) the lateral corallites always occur in the vicinity of four primary septa, excluding the two directive primary septa; (2) the two directive septa in lateral corallites tend to be oriented almost perpendicular to the growth orientation of parental corallites; (3) the lateral corallites grow more‐or‐less diagonally upwards; and (4) these regularities are retained from the axial to the derived lateral corallites during colony growth. Accordingly, a colony of apparently complex dendroid corals is formed according to certain universal rules that apply to successive generations of corallites. The presence of two opposite sectors in which budding do not occur seems to be common to other azooxanthellate scleractinian families. Regularities, other than the orientation of the directive septa, are also commonly found at least in other azooxanthellate dendrophylliid genera. These regularities suggest the presence of strict developmental constraints on the asexual reproduction of the Scleractinia, both extant and extinct. These regularities by azooxanthellate scleractinians, as one of the representative colonial metazoan groups, provide us with fundamental data with which we can understand how colonies are constructed. □Azooxanthellate coral, budding, colony, Dendrophyllia arbuscula, regularity.     

Regularity and polarity in budding of the colonial scleractinian Dendrophyllia ehrenbergiana: consequences of radio‐bilateral symmetry of the scleractinian body plan

Sentoku, A. & Ezaki, Y. 2012: Regularity and polarity in budding of the colonial scleractinian Dendrophyllia ehrenbergiana: consequences of radio‐bilateral symmetry of the scleractinian body plan. Lethaia, Vol. 45, pp. 586–593. Regularities and polarity in budding of the azooxanthellate scleractinian Dendrophyllia ehrenbergiana were examined with the aim of understanding the developmental constraints on the formation of colonies. Its mode of budding, in light of the orientations of directive septa of offsets and the inclination angle of budding, is consistent with that of other dendrophyllids; however, the offsets of D. ehrenbergiana only occur near the two primary septa on the convex side of individual corallites, showing a plane of bilateral symmetry with a distinct polarity. These regularities and polarity are seen in the axial and its derived corallites throughout growth. Of note, the polarity at individual corallites is clearly reflected in subsequent colony growth by the branching pattern and corallite number. These characteristics imply the presence of radio‐bilateral symmetrical constraints on the asexual reproduction of the Scleractinia and give us invaluable clues to the understanding of shape‐making mechanisms of marine modular organisms. □Asexual reproduction, azooxanthellate coral, budding, colony, Dendrophyllia ehrenbergiana, polarity.     

Regular budding modes in a zooxanthellate dendrophylliid Turbinaria peltata (Scleractinia) revealed by X‐ray CT imaging and three‐dimensional reconstruction

The zooxanthellate dendrophylliid coral, Turbinaria peltata (Scleractinia), exhibit various growth forms that increase the photoreception area through the development of coenosteum skeletons. Because it is difficult to make detailed observations of the internal structures, we visualized inner skeletal structures using nondestructive microfocus X‐ray computed tomography (CT) imaging. After removal of the coenosteum skeletons from the X‐ray CT images, three‐dimensional 3D‐models were reconstructed for individual corallites. Regular budding was observed from the 3D‐model and cross‐sectional images as follows: 1) lateral corallites occurred only near the two primary septa on one side, apart from a directive primary septum with distinct polarity; 2) the budding occurred upward at acute angles; and 3) these regular structures and polarity were repeated throughout growth with every generation. Even in zooxanthellate dendrophylliids, the same budding modes as observed in azooxanthellate equivalents control the colonial growth. These characteristics provide clues for understanding the mechanisms that regulate the shapes of modular marine organisms. J. Morphol. 276:1100–1108, 2015. © 2015 Wiley Periodicals, Inc.     

Skeletal response of <Emphasis Type="Italic">Lophelia pertusa</Emphasis> (Scleractinia) to bioeroding sponge infestation visualised with micro-computed tomography

The skeleton morphology of the azooxanthellate cold-water coral Lophelia pertusa can be strongly influenced by invasive boring sponges that infest corallites in the still living part of the colony. Atypically swollen corallites of live Lophelia pertusa from the Galway Mound (Belgica Carbonate Mound Province, Porcupine Seabight, NE Atlantic), heavily excavated by boring organisms, have been examined with a wide range of non-destructive and destructive methods: micro-computed tomography, macro- and microscopic observations of the outer coral skeleton, longitudinal and transversal thin sections and SEM analyses of coral skeleton casts. As a result, three excavating sponge species have been distinguished within the coral skeleton: Alectona millari, Spiroxya heteroclita and Aka infesta. Furthermore, four main coral/sponge growth stages have been recognised: (1) cylindrical juvenile corallite/no sponge cavities; (2) flared juvenile corallite/linear sponge cavities (if present); (3) slightly swollen adult corallites/chambered oval sponge cavities; (4) very swollen adult corallites/widespread cavities. The inferred correlation between corallite morphology and boring sponge infestation has been detected in micro-computed tomography (micro-CT) images and confirmed in sponge trace casts and peculiar features of coral skeleton microstructure. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

STRUCTURE AND DEVELOPMENT OF HYPHAL SEPTA IN ALLOMYCES

Development of hyphal septa (pseudosepta) in Allomyces macrogynus begins with the formation of five or more discontinuous pieces of wall material that project inward from the hyphal wall. Lateral fusion of these projections leaves a central pore in the septum that is later filled in by centripetal deposition of wall material. However, lateral fusion of the projections is not complete; peripheral pores remain in the rim of the mature septum. The position of cytoplasmic microtubules corresponds to the position of actively moving cellular particles and organelles. Allomyces reticulatus and A. arbuscula have similar septa.     

Microstructural characteristics of the stony coral genus Acropora useful to coral reef paleoecology and modern conservation

Identification of fossil corals is often limited due to poor preservation of external skeleton morphology, especially in the genus Acropora which is widespread across the Indo‐Pacific. Based on skeleton characteristics from thin section, we here develop a link between the internal skeleton structure and external morphology. Ten characteristics were summarized to distinguish Acropora and five related genera, including the type and differentiation of corallites, the skeleton nature of corallites (septa, columellae, dissepiments, wall), and calcification centers within septa. Acropora is distinctive for its dimorphic corallites: axial and radial. Isopora is similar to Acropora but possess more than a single axial corallites. Montipora and Astreopora (family Acroporidae) have monomorphic corallites and a synapticular ring wall, with clustered calcification center in the former and medial lines in the latter. Pocillopora and Porties are classified by distinctive dissepiments, columellae and septa. These microstructural skeleton characteristics were effective in the genus identification of fossil corals from drilled cores in the South China Sea. Eighteen detailed characteristics (ten of axial corallites, four of radial corallites, and four of coenosteum) were used in the Acropora species classification. The axial corallites size and structure (including corallite diameter, synapticular rings, and septa), the septa of radial corallites, and the arrangement of coenosteum were critical indicators for species identification. This identification guide can help paleoenvironmental and paleoecological analyses and modern coral reef conservation and restoration.     

Astogenese vonAulopora cf.enodis Klaamann 1966Visby-Mergel, Silur von Gotland

This paper deals with bifurcation angle of a reptant, dichotomously branchingAulopora cf.enodis colony (Silurian, Gotland). It can be demonstrated, that during early astogenetic growth the branching angle between offsetting corallites decreases rapidly from 165° to 100° averagely during later growth stages. This growth pattern resembles development of similar dichotomous branching uniseral bryozoans, e.g. PaleozoicCorynotrypa species or MesozoicStomatopora species.     

Life‐history strategies of Manipora amicarum Sinclair, 1955 (Tabulata; Upper Ordovician; southern Manitoba,Canada)

Based on detailed study of transverse serial sections, we recognize various modes of corallite increase in a multichain cateniform coral, Manipora amicarum from the Selkirk Member, Red River Formation, in Manitoba. One type of axial increase and four types of lateral increase involve normal, undamaged corallites, and one type of axial increase and one type of lateral increase occur during recovery processes of corallites damaged by sediment or bioclast influx. All but one of these types of increase are comparable to those in a single‐chain coral, Catenipora foerstei, which we previously documented from the same stratigraphic unit and locality. In M. amicarum, the formation of double ranks and agglutinated patches of corallites by normal corallites, and by recovery processes following corallite damage, is common and presumably genetically controlled. Agglutinated patches originate differently in C. foerstei, occurring sporadically or temporarily in only some coralla. Average annual vertical corallum growth in M. amicarum, as indicated by cyclic fluctuations of tabularial area, is higher than in C. foerstei, which has comparatively smaller corallites. In general, annual growth in M. amicarum is positively correlated with average tabularial area, negatively correlated with frequency of damaged corallites, and is not related to the frequency of corallite increase. In C. foerstei, however, there is a positive association between annual growth rate and the frequency of increase by damaged corallites, related to episodes of sediment or bioclast influx probably generated by storms. In comparison with C. foerstei, M. amicarum has a low frequency of corallite termination and extensive partial mortality is rare. It seems that the relatively rapid overall vertical corallum growth in M. amicarum was effective for protecting the coral from unfavourable situations, possibly by maintaining the growth surface higher above the substrate than in C. foerstei. Although these two species show many similarities in the types of corallite increase, their reactions and strategies in relation to physical disturbance were quite different.     

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.     

Skeletal growth, ultrastructure and composition of the azooxanthellate scleractinian coral Balanophyllia regia

The biomineralization process and skeletal growth dynamics of azooxanthellate corals are poorly known. Here, the growth rate of the shallow-water dendrophyllid scleractinian coral Balanophyllia regia was evaluated with calcein-labeling experiments that showed higher lateral than vertical extension. The structure, mineralogy and trace element composition of the skeleton were characterized at high spatial resolution. The epitheca and basal floor had the same ultrastructural organization as septa, indicating a common biological control over their formation. In all of these aragonitic skeletal structures, two main ultrastructural components were present: “centers of calcification” (COC) also called rapid accretion deposits (RAD) and “fibers” (thickening deposits, TD). Heterogeneity in the trace element composition, i.e., the Sr/Ca and Mg/Ca ratios, was correlated with the ultrastructural organization: magnesium was enriched by a factor three in the rapid accretion deposits compared with the thickening deposits. At the interface with the skeleton, the skeletogenic tissue (calicoblastic epithelium) was characterized by heterogeneity of cell types, with chromophile cells distributed in clusters regularly spaced between calicoblasts. Cytoplasmic extensions at the apical surface of the calicoblastic epithelium created a three-dimensional organization that could be related to the skeletal surface microarchitecture. Combined measurements of growth rate and skeletal ultrastructural increments suggest that azooxanthellate shallow-water corals produce well-defined daily growth steps.     

Reciprocal transplantation of the heterotrophic coral Tubastraea coccinea (Scleractinia: Dendrophylliidae) between distinct habitats did not alter its venom toxin composition

Tubastraea coccinea is an azooxanthellate coral species recorded in the Indian and Atlantic oceans and is presently widespread in the southwestern Atlantic with an alien status for Brazil. T. coccinea outcompete other native coral species by using a varied repertoire of biological traits. For example, T. coccinea has evolved potent venom capable of immobilizing and digesting zooplankton prey. Diversification and modification of venom toxins can provide potential adaptive benefits to individual fitness, yet acquired alteration of venom composition in cnidarians is poorly understood as the adaptive flexibility affecting toxin composition in these ancient lineages has been largely ignored. We used quantitative high‐throughput proteomics to detect changes in toxin expression in clonal fragments of specimens collected and interchanged from two environmentally distinct and geographically separate study sites. Unexpectedly, despite global changes in protein expression, there were no changes in the composition and abundance of toxins from coral fragments recovered from either site, and following clonal transplantation between sites. There were also no apparent changes to the cnidome (cnidae) and gross skeletal or soft tissue morphologies of the specimens. These results suggest that the conserved toxin complexity of T. coccinea co‐evolved with innovation of the venom delivery system, and its morphological development and phenotypic expression are not modulated by habitat pressures over short periods of time. The adaptive response of the venom trait to specific predatory regimes, however, necessitates further consideration.     

17Beta-hydroxysteroid dehydrogenase (17beta-HSD) in scleractinian corals and zooxanthellae

Steroid metabolism studies have yielded evidence of 17β-hydroxysteroid dehydrogenase (17β-HSD) activity in corals. This project was undertaken to clarify whether there are multiple isoforms of 17β-HSD, whether activity levels vary seasonally, and if zooxanthellae contribute to activity. 17β-HSD activity was characterized in zooxanthellate and azooxanthellate coral fragments collected in summer and winter and in zooxanthellae cultured from Montipora capitata. More specifically, 17β-HSD activity was characterized with regard to steroid substrate and inhibitor specificity, coenzyme specificity, and Michaelis constants for estradiol (E₂) and NADP⁺. Six samples each of M. capitata and Tubastrea coccinea (three summers, three winters) were assayed with E₂ and NADP⁺. Specific activity levels (pmol/mg protein) varied 10-fold among M. capitata samples and 6-fold among T. coccinea samples. There was overlap of activity levels between summer and winter samples. NADP⁺ / NAD⁺ activity ratios varied from 1.6 to 22.2 for M. capatita, 2.3 to 3.8 for T. coccinea and 0.7 to 1.1 for zooxanthellae. Coumestrol was the most inhibitory of the steroids and phytoestrogens tested. Our data confirm that corals and zooxanthellae contain 17β-HSD and are consistent with the presence of more than one isoform of the enzyme.     

Growth characteristics in co‐occurring Upper Ordovician species of the tabulate Catenipora from southern Manitoba,Canada

Four species of the tabulate coral Catenipora are present in the Selkirk Member of the Red River Formation at Garson, Manitoba. They provide an opportunity to compare the growth characteristics of multiple, co‐occurring species that produced cateniform coralla. Corallite increase, cyclomorphism and other growth features show high variability within and/or among the species. A total of five types of lateral increase and two types of axial increase are recognized. Lateral increase accounts for over 80% of all occurrences of corallite increase in each species, with the four species differing significantly in the relative frequency of the various types of lateral increase. The type of axial increase, megacorallites and agglutinated patches of corallites that developed from normal, undamaged corallites in C. foerstei are species specific. In all species, cyclic fluctuations in the tabularial area of corallites are considered to be annual, and the variable growth rates within colonies and species are attributed to differences in astogenetic stages or environmental conditions. Average annual vertical growth was positively correlated with average tabularial area in C. foerstei, C. cf. robusta and C. rubra. Catenipora cf. agglomeratiformis, however, which had the lowest average tabularial area and greatest sensitivity to sediment influx, had a high average growth rate comparable to that of C. rubra, which had the largest average tabularial area. The formation of ranks or lacunae by certain types of lateral increase seems to have been the most effective strategy for maintaining and/or expanding the colony growth surface in all four species, and was most common in C. cf. agglomeratiformis. A reptant growth pattern, characterized by creeping ranks, permitted effective recovery of damaged parts as well as quick formation of new ranks or lacunae. The growth surface of these species was situated near the sediment–water interface. □Growth characteristics, intraspecific variation, interspecific variation, palaeobiology, tabulate corals.     

Septum formation is regulated by the RHO4‐specific exchange factors BUD3 and RGF3 and by the landmark protein BUD4 in Neurospora crassa

Rho GTPases have multiple, yet poorly defined functions during cytokinesis. By screening a Neurospora crassa knock‐out collection for Rho guanine nucleotide exchange factor (GEF) mutants that phenocopy rho‐4 defects (i.e. lack of septa, slow growth, abnormal branching and cytoplasmic leakage), we identified two strains defective in homologues of Bud3p and Rgf3 of budding and fission yeast respectively. The function of these proteins as RHO4‐specific GEFs was determined by in vitro assays. In vivo microscopy suggested that the two GEFs and their target GTPase act as two independent modules during the selection of the septation site and the actual septation process. Furthermore, we determined that the N. crassa homologue of the anillinrelated protein BUD4 is required for septum initiation and that its deficiency leads to typical rho4 defects. Localization of BUD4 as a cortical ring prior to septation initiation was independent of functional BUD3 or RGF3. These data position BUD4 upstream of both RHO4 functions in the septation process and make BUD4 a prime candidate for a cortical marker protein involved in the selection of future septation sites. The persistence of both BUD proteins and of RHO4 at the septal pore suggests additional functions of these proteins at mature septa.     

Spatial distribution of calcification and photosynthesis in the scleractinian coral Galaxea fascicularis

The spatial heterogeneity of photosynthesis and calcification of single polyps of the coral Galaxea fascicularis was investigated. Photosynthesis was investigated with oxygen microsensors. The highest rates of gross photosynthesis (Pg) were found on the tissue covering the septa, the tentacles, and the tissues surrounding the mouth opening of the polyp. Lower rates were found on the tissues of the wall and the coenosarc. Calcification was investigated by radioactive tracers. The incorporation pattern of ⁴⁵Ca and ¹⁴C in the corallites was imaged with use of a Micro-Imager. The -images obtained showed that the incorporation of the radioactive tracers coincided with the Pg distribution pattern with the highest incorporation rates found in the corallite septa. Thus, the high growth rate of the septa is supported by the high rates of Pg by the symbiont in the adjacent tissues. The total incorporation rates were higher in light than in dark, however, the distribution pattern of the radioisotope incorporation was not affected by illumination. This further emphasizes the close relation between calcification and photosynthesis.     

Proliferation of the hyperthermophilic archaeon Pyrobaculum islandicum by cell fission

Pyrobaculum islandicum is a hyperthermophilic archaeon. P. islandicum cells have been suggested to multiply by constriction, budding and branching, as no septa were observed in cells by phase-contrast light microscopy. In this study, we observed the cells using transmission electron microscopy, scanning electron microscopy, and light microscopy with dark-field image analyses, and we report binary fission via septum formation to be the main mode of P. islandicum’s proliferation. “Long cells” reported previously were found to comprise several cylindrical cells that align in tandem.     

模拟长期大风对木本猪毛菜表观特征的影响

风是一个重要的生态因子,对植物地上部分的生长和构型有重要影响。植物表观特征对植物获取光能、抵抗外界机械压力有着重要作用。木本猪毛菜(Salsola arbuscula Pall.)是新疆达坂城大风区植被的共建种,也是该区植被恢复潜在的先锋植物。为了研究木本猪毛菜在长期大风环境中形成的独特适应机制,以盆栽实验为手段,设置3个风速(小风:3 m/s,中风:7 m/s,大风:12 m/s),持续吹风105d,定量分析长期大风作用下木本猪毛菜地上部分的生长和空间构型的变化。结果表明:(1)风胁迫减小了木本猪毛菜的株高,增大了其顺风向的基径;大风减小了木本猪毛菜的叶片长度,中风和小风对其叶片长度没有影响;大风和中风增加了木本猪毛菜的叶片数,小风对叶片数没有影响。(2)木本猪毛菜植冠的空间构型在迎风面和背风面出现明显的不对称性;风胁迫减小了木本猪毛菜的主茎弯曲角度、叶倾角;大风和小风减小了木本猪毛菜的冠幅,中风没有影响;大风和中风减小了木本猪毛菜的枝倾角,小风没有影响;木本猪毛菜在大风和中风作用下出现了二级分枝,在小风作用下没有出现二级分枝。木本猪毛菜主要通过减小自身的扩大生长,增加空间构型的不对称性,减小枝与叶的受力面积等方式来降低风的阻力,以适应长期大风。     

Soil disturbance,vegetation cover and the establishment of the exotic shrub <Emphasis Type="Italic">Pyracantha coccinea</Emphasis> in southern France

We evaluate the mechanisms that determine the establishment of the non-indigenous shrub Pyracantha coccinea (Rosaceae) in the Montpellier region of southern France. P. coccinea establishes in abandoned agricultural fields in this region; yet, despite its high propagule pressure, it has not become a widespread invasive. We hypothesized that the disturbance conditions prevailing in abandoned agricultural fields right after abandonment may enhance the emergence, survival and growth of P. coccinea, but that shortly after abandonment colonizing vegetation prevents further establishment of this species. We conducted a field experiment to evaluate this hypothesis, studying the response of seedling emergence and growth of P. coccinea to soil and vegetation disturbance. Our results show that both lack of vegetation cover and soil disturbance promote the emergence of seedlings of P. coccinea. Thus, the disturbance conditions prevailing in abandoned agricultural fields seem crucial to allow establishment of this species. However, other factors such as lack of summer dormancy and seed predation might explain why this species has not become a widespread invasive.     

Coral calcification: autoradiography of a scleractinian coral Galaxeafascicularis after incubation in 45Ca and 14C

 The uptake of ⁴⁵Ca and/or ¹⁴C by the skeleton of coral colonies has been commonly used to investigate the processes of calcification. This study reports the differential uptake of these tracers within different regions of the skeleton and tissues of individual corallites and polyps of the hermatypic coral Galaxea fascicularis. Incubation in ⁴⁵Ca in the light resulted in 80 percent of the ⁴⁵Ca taken up being deposited in the skeleton. Autoradiography of transverse and longitudinal slices of freeze-substituted polyps and corallites showed that in the light ⁴⁵Ca was incorporated into the exsert septa, the outside of the thecal walls of the corallite and the inner edges of the septa. Incorporation did not occur in the costae. The radioactivity in the skeleton was considerably greater than in the tissues. In the dark, or in the presence of the photosynthetic inhibitor Diuron, ⁴⁵Ca was taken up by the exsert septa and was patchily distributed in the corallite walls which suggests that it was not a result of isotopic exchange. The differential incorporation of ⁴⁵Ca onto the exsert septa was confirmed by scintillation counting. Negligible radioactivity remained in the extrathecal coelenteron after a brief 5 min rinse in non-radioactive seawater. Only 0.1% of ¹⁴C taken up in the light was incorporated into the skeleton and this was confirmed by autoradiography. In the presence of Diuron or in the dark, very little ¹⁴C was incorporated into tissues or skeleton and in autoradiographs was either not evident in the skeleton or the distribution was similar to that seen in autoradiographs of ⁴⁵Ca uptake. These results show that the deposition of ⁴⁵Ca, and therefore calcium carbonate, occurs at specific loci on the skeleton of a corallite. In the dark, deposition occurs specifically at the growing points of the corallite. Differential deposition of calcium carbonate within individual corallites has not been previously reported. Accepted: 27 May 1997     

Associations of corals and boring bivalves since the late cretaceous

Summary The fossil record of coral and boring mytilid bivalves IS investigated. Middle Miocene associations from Austria, Hungary, and Turkey are described. As host corals,Montastrea, Porites, Siderastrea, Solenastrea, andTarbellastraea can be noted. Eocene (Waschberg Zone) and Upper Cretaceous (Gosau Formation) examples are presented from Austria only. As host corals,Favia andMontastrea, respectivelyAstrocoenia and an unidentified branching coral are recorded. The associated bivalve species are all mytilidLithophaga, includingL. laevigata (Quoy & Gaimard) inTarbellastraea, a new Middle Miocene species inMontastrea, andL. alpina (Zittel) inAstrocoenia, the latter two from Styria, Austria. Thecharacteristic features of the coral-bivalve relationships include (in massive corals): Boreholes more or less in the direction of coral growth, radially arranged, elongate boreholes, produced by keeping pace with coral growth. Bivalves were not only present near the surface, but deep inside the skeleton, representing successive generations in the same host colony. After the death of borers, their tunnels were closed by coral overgrowth. Cup-shaped false floors in the boreholes are correlated to reduced coral growth, indicating individual longevity of bivalves. The spacing of the floors mirrors the growth rate of the host coral (like its density bands), their number representing the minimal age of the respective bivalve. In branching corals, boreholes of the associated smallsizedLithophaga tended to turn into the axes of branchlets, when space was limited. Elongated boreholes and false floors were usually not developed, as bivalve growth obviously exceeded lateral growth of branchlets and specimens were rather short-lived. References to probable associations of coral and mytilid boring bivalves are given. It is quite likely that they have occurred since Jurassic times and probably since the Upper Triassic. So far, they have been ascertained since the Upper Cretaceous in massive and branching corals.