Vent and mound rugose coral associations from the Middle Devonian of Hamar Laghdad (Anti-Atlas, Morocco)

Peculiar associations of small, solitary, deep-water rugose corals are described from the Middle Devonian buildups situated in the easternmost part of Hamar Laghdad area of southern Morocco. The most of them are monospecific and consist of simplified taxon “Amplexus” florescens but one is polyspecific and composed of specimens belonging to four different species representing three families. These rugosan associations form isolated nest-like aggregations where numerous densely packed specimens are arranged mostly in life position. The polyspecific and two monospecific associations are interpreted as growing in close proximity to venting fields. They reveal a unique “calice-in-calice” recolonization pattern expressed by successive settlement of juvenile specimens in the calice of dead individuals. This pattern was presumably a consequence of selective survival of coral larvae settling in extreme vent habitats. Although, the “calice-in-calice” pattern is common in both, mono- and polyspecific associations, there are differences expressed in the character of larval attachments and various types of the calice fillings. The trophic interaction between corals and ostracods is discussed. Additionally, associations of “Amplexus” florescens, not displaying “calice-in-calice” pattern of growth have been found within the mound where polyspecific association occurs. These are interpreted as growing away from venting fields. Comparisons of Amplexus-type coral faunas with the other North African and European corals allow the classification of these ampleximorph rugosan taxa as characteristic biotic components of the Middle Devonian mound environments influenced by venting activity. Two new genera and species, Weyeraia prima and Vesiculolasma erfoudi, are introduced.     

Succession of rudistid lithosomes along the western coastal margin of the Iberian Basin (Coniacian,Castrojimeno Section,central Spain)

Rudistid lithosomes cropping out near Castrojimeno, at the northern margin of the Central System in north-central Spain, provide detailed information on their composition and structure, on their development and succession, and about their relationship with the Coniacian sequence stratigraphy framework of the Iberian Basin. Most rudist assemblages are oligospecific, with a dominant species, or monospecific. The radiolitids Biradiolites angulosus, Praeradiolites requieni, and Radiolites sauvagesi and the hippuritids Hippurites incisus and Vaccinites giganteus were identified. Radiolitids demonstrate wide intraspecific morphological variability. The following Riding’s structural categories of organic reefs are represented: segment reefs, spaced and close cluster reefs, and close cluster/frame reefs. Bioclastic beds of reworked rudist fragments occur below or in between the rudist reefs. The vertical succession of all five types of rudistid lithosomes distinguished evidences a shallowing-upward trend. Rudistid lithosomes developed on the coastal margin during the superposition of the highstand sea-level stage of third- and fourth-order depositional sequences.     

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.     

Space partitioning by stony corals soft corals and benthic algae on the coral reefs of the northern Gulf of Eilat (Red Sea)

The major faunistic and floristic components occupying space on the coral reefs of the northern Gulf of Eilat (Red Sea) are stony corals, soft corals and benthic algae. The percent living coverage of the three components and the relative abundance of the different species of each component were studied by line transects, on the reef flats and the upper forereef zones of nine localities. A wider and higher range of living coverage values of stony corals were recorded at the upper fore-reef zones (18.30–49.09%) compared with the reef flats (5.50–31.66%) at the different stations. The most abundant stony corals on the reef flats areCyphastrea microphthalma, Stylophora pistillata, Favia favus, Porites lutea, Platygyra lamellina and the hydrozoanMillepora dichotoma. The fire coralM. dichotoma dominates the upper fore-reef zone in most of the stations. The average percent living coverage of soft corals on the reef flats ranged between 0.20 and 17.06%, and on the upper fore-reef zones between 1.68 and 15.13%. Seventy percent of the total living coverage of the soft coral community is contributed by 2 to 3 species. They tend to form large monospecific carpets, such as those composed ofSinularia sp.,Sarcophyton glaucum andLobophytum pauciflorum. The common benthic algae on the coral reef studied occur as turfs or macroscopic noncalcareous algae. They play a significant role in occupying space, especially on the reef flats. The most abundant algae recorded in all localities are the turfsSphacelaria tribuloides, Jania sp. and the macroscopic non-calcareous algaeTurbinaria elatensis andColpomenia sinuosa. Comparison between reef flats and upper fore-reef zones, in terms of average living cover of stony corals, shows that the variation among the reef flats is grater than the variation among the upper fore-reef zones. However, there is no significant variation in the average living coverage of soft corals between these two zones. Annual living-coverage values of algae on the reef flats are significantly higher than those of the upper fore-reef zones. Extremely low tides occurring periodically but unpredictably at Eilat cause mass mortality of the benthic communities on the reef flats reopening new spaces for settlement. The coexistence of stony corals, soft corals and algae on the reef ecosystem is due to different biological properties of each component. Opportunistic life histories of certain stony corals and most algae enable quick colonization of newly opened spaces. Lack of predators, high tolerance against abiotic factors and ability to form large aggregates of colonies are suggested as possible factors supporting the existence of soft corals in shallow water. Biological factors such as competition, predation and grazing pressure play an increasingly important role in controlling space utilization by the components studied with the advancement of succession.     

Highly stable symbioses among western Atlantic brooding corals

The reproductive mode of corals largely determines how zooxanthellae (Symbiodinium spp.) are acquired. Typically, broadcast spawning corals obtain symbionts from the surrounding environment, whereas most brooders transfer symbionts from maternal parent to offspring. Brooding corals are therefore predicted to harbor stable communities of Symbiodinium. This study documents the associations between Symbiodinium spp. and brooding corals in response to seasonal environmental fluctuations. Between March 2002 and December 2005, endosymbiont identity was determined seasonally from replicate colonies (n = 6) of three brooding species, Agaricia agaricites, Porites astreoides and Siderastrea radians, from shallow environments (1–4 m) of the Florida Keys and Bahamas. Symbionts were identified via denaturing gradient gel electrophoresis (DGGE) of the internal transcribed spacer 2 (ITS2) region. No change was detected in the Symbiodinium communities harbored within these brooding colonies. Additionally, no change in symbiosis was observed through a moderate bleaching event, thereby demonstrating that some bleached corals recover without changing symbionts.     

Estimating bark thickness in natural stands of Eucalyptus

Information on bark thickness at various heights is sought to predict damage to trees by forest fires. A procedure which for natural stands of some smooth bark eucalyptus species enables the estimation of bark thickness at different heights from a single girth measurement at one metre height is discussed. The method utilizes the relationships of average girth, average bark thickness, and the regression coefficients of girth and bark thickness at given height positions, with height at one metre. The height positions are determined on a calibrating sample of about thirty trees of different sizes. Furthermore it is shown how the above information can be used to estimate bark volume, and hence bole volume, for Eucalyptus species of some commercial importance such as E. viminalis. Four species are considered: E. viminalis, E. pauciflora, E. mannifera and E. radiata.     

Habitats of colonial rugose corals: the Mississippian of western Europe as example for a general classification

Aretz, M. 2010: Habitats of colonial rugose corals: the Mississippian of western Europe as example for a general classification. Lethaia, DOI: 10.1111/j.1502‐3931.2010.00218.x. Colonial rugose corals are a major constituent of shallow‐water marine benthic communities in Mississippian times. The study of western European rugose coral habitats from the base of the Tournaisian stage to the Serpukhovian stage allows the recognition of four basic habitat types, which can be divided into a total of 11 subtypes. The classification is mainly based on field data, and thus rapidly applicable. Level‐bottom communities in which large colony distances are characteristic (type A) represent the most basic community type; polyspecific (subtype A1) and monospecific (subtype A2) subtypes occur. Reduced colony distances result in the formation of coral meadows (type B), which either show homogenous coral distribution (subtype B1) or the development of patches (subtype B2). Coral biostromes (type C) represent a spectrum between hydrodynamically controlled biostromes (nothing in place, subtype C1) and biologically constructed and controlled biostromes (subtype C2). The bulk of the biostromes represent mixtures of those two subtypes (subtype C3). Colonial rugose corals are widely encountered in Mississippian bioherms where they are dwellers (subtype D1), form capping beds (subtype D2), support framework building along with other organisms (subtype D3) and form coral framework (subtype D4). The latter is probably the most uncommon of all subtypes in Mississippian times. The classification is widely applicable to other groups. □Classification, habitats, Mississippian, palaeoecology, palaeoenvironment, rugose corals.     

Discordant coral–symbiont structuring: factors shaping geographical variation of Symbiodinium communities in a facultative zooxanthellate coral genus,Oculina

Understanding the factors that help shape the association between corals and their algal symbionts, zooxanthellae (Symbiodinium), is necessary to better understand the functional diversity and acclimatization potential of the coral host. However, most studies focus on tropical zooxanthellate corals and their obligate algal symbionts, thus limiting our full comprehension of coral–algal symbiont associations. Here, we examine algal associations in a facultative zooxanthellate coral. We survey the Symbiodinium communities associated with Oculina corals in the western North Atlantic and the Mediterranean using one clade-level marker (psbA coding region) and three fine-scale markers (cp23S–rDNA, b7sym15 flanking region, and b2sym17). We ask whether Oculina spp. harbor geographically different Symbiodinium communities across their geographic range and, if so, whether the host’s genetics or habitat differences are correlated with this geographical variation. We found that Oculina corals harbor different Symbiodinium communities across their geographical range. Of the habitat differences (including chlorophyll a concentration and depth), sea surface temperature is better correlated with this geographical variation than the host’s genetics, a pattern most evident in the Mediterranean. Our results suggest that although facultative zooxanthellate corals may be less dependent on their algal partners compared to obligate zooxanthellate corals, the Symbiodinium communities that they harbor may nevertheless reflect acclimatization to environmental variation among habitats.

     

Contribution to the scleractinian corals of Hanifa Formation,Upper Jurassic,Jabal Al-Abakkayn,central Saudi Arabia

Eighteen scleractinian coral species belonging to 13 genera, 8 families and 4 suborders have been identified from the lower and upper parts of the Upper Jurassic (Oxfordian) Hanifa Formation at Jabal Al-Abakkayn, central Saudi Arabia. Actinastrea bernensis, A. crassoramosa, Coenastraea hyatti, Stylina kachensis, Cryptocoenia slovenica, C. wegeneri, Isastrea hemisphaerica, I. bernensis, Montlivaltia cornutiformis, M. frustriformis, Collignonastraea jumarensis, Ovalastrea michelini and Vallimeandropsis davidsoni are believed to be recorded for the first time from the Jurassic rocks of central Arabia. Most corals have massive hemispherical and globular forms, and few corals have dendroid and conical growth forms. They occur as small, isolated patches, about 0.5 m thick and about 10–30 m wide, in argillaceous reefal limestones. The identified corals show Africa, north America, northern, southern and western Europe, and southern or eastern Asia corals. The low diversity and abundance as well as the small size of colonies are attributed to inimical palaeoecological factors throughout the reefoids formation such as muddy substratum, water turbidity, high rate of sedimentation.     

Variation in the skull morphometry of four taxonomic units of Thrichomys (Rodentia: Echimyidae), from different Neotropical biomes

The echimyid rodents of the genus Thrichomys vary considerably in their behavior and feeding ecology, reflecting their occurrence in environments as different as the Caatinga, Cerrado, Pantanal, and Chaco biomes. While the genus was originally classified as monospecific, a number of Thrichomys species have been recognized in recent decades, based on morphometric, cytogenetic, and molecular analyses. While Thrichomys is well studied, the variation found in its cranial morphology is poorly understood, given the taxonomic and ecological complexities of the genus. Using a geometric morphometric approach, we characterized the differences found in the cranial morphology of four Thrichomys taxonomic units, including three established species, Thrichomys apereoides, Thrichomys fosteri, and Thrichomys laurentius, and one operational taxonomic unit (OTU), Thrichomys aff. laurentius. No significant differences were found among these units in cranium size, but significant variation was found in skull shape. The Procrustes distances provided a quantification of the differences in the shape of the skull, with the largest distances being found between T. aff. laurentius and T. fosteri in the dorsal view, and between T. aff. laurentius and T. apereoides in the ventral view. A Discriminant Function Analysis (DFA) with cross-validation determined that the pairings with the highest correct classification were T. aff. laurentius vs. T. apereoides and T. aff. laurentius vs. T. fosteri, in both views. The principal variation in skull shape was found in the posterior region and the zygomatic arch, which may be related to differences in diet.     

Bathymetric zonation of modern microborers in dead coral substrates from New Caledonia—Implications for paleodepth reconstructions in Holocene corals

Microboring endoliths were studied in dead modern corals collected at various depths and in growth position on La Surprise atoll in New Caledonia. Eight taxa of microborers were regularly observed: three cyanobacteria (Hyella caespitosa, Mastigocoleus testarum, and Plectonema terebrans), two chlorophytes (Ostreobium quekettii and Phaeophila dendroides) and three fungal forms (Dodgella priscus, and two unidentified fungi). The relative abundance of each taxon was determined in the modern corals throughout the studied sampling interval (from 0 down to 40 m water depth). This allowed us to propose for the first time a bathymetric model based on microendolith assemblages colonizing in situ hard-substrates of corals. In this model, the occurrence of the cyanobacteria Hyella and Mastigocoleus indicates a bathymetric range from 0 down to a water depth of 3 and 6 m respectively. The chlorophyta O. quekettii, associated with the cyanobacterium P. terebrans and fungi, is dominant from 10 to 40 m depth, which is the lower limit of our sampling. The distribution ranges of individual taxa observed in the dead coral substrates from New Caledonia are much narrower than those reported in the literature for other substrates.The bathymetric model based on distribution of microborers in modern corals was then applied to interpret the trace assemblages of microborers observed in Holocene corals collected by drilling on two reef sites of New Caledonia : La Surprise islet, in the vicinity of the sampling sites of the modern corals, and the barrier reef of Bayes, on the NE coast of Grande Terre. The paleodepth interpretations performed at various levels along the cores allow identification of several shallowing-upward sequences during the last 7000 years of reef growth in New Caledonia. Differences in the thickness of these sequences between La Surprise and Bayes sites were interpreted as differences in the space available for accommodation between the two sites, in turn related to the differential subsidence that affected New Caledonia during Holocene times. The use of the microendolith trace assemblages in paleodepth reconstructions of Holocene reefs from New Caledonia allowed detection of relative sea level variations finer than those deduced from changes in coralgal assemblages.     

The role of sterility genes (ste and aff) in the initiation of sexual development in Schizosaccharomyces pombe

Summary Haploid homothallic strains of Schizosaccharomyces pombe with mutations in any of nine sterility genes (ste) do not mate with wild-type fertile strains. Those defective in genes ste1 to ste4 and ste7 to ste9 are also deficient in meiosis and sporulation. I found that the ste1, ste3 and ste8 genes act very early in the sexual development, presumably before the pat1-controlled conjugation-specific event. ste5 and ste6 exert their function downstream of pat1 in the initiation of conjugation and do not play any role in the meiotic pathway. ste2, ste4, ste7 and ste9 are involved in both sexual pathways: they seem to act downstream of pat1 in conjugation but upstream of pat1 in the initiation of meiosis. A new gene, aff1, whose defective allele suppresses the pat1-114-provoked haploid sporulation and arrest of vegetative growth is also described. It is supposed that the aff1 ⁺ gene product participates in a cascade of regulatory events, as a factor antagonistic to pat1.     

Juvenile corals can acquire more carbon from high-performance algal symbionts

Algal endosymbionts of the genus Symbiodinium play a key role in the nutrition of reef building corals and strongly affect the thermal tolerance and growth rate of the animal host. This study reports that ¹⁴C photosynthate incorporation into juvenile coral tissues was doubled in Acropora millepora harbouring Symbiodinium C1 compared with juveniles from common parentage harbouring Symbiodinium D in a laboratory experiment. Rapid light curves performed on the same corals revealed that the relative electron transport rate of photosystem II (rETR_MAX) was 87% greater in Symbiodinium C1 than in Symbiodinium D in hospite. The greater relative electron transport through photosystem II of Symbiodinium C1 is positively correlated with increased carbon delivery to the host under the applied experimental conditions (r ² = 0.91). This may translate into a competitive advantage for juveniles harbouring Symbiodinium C1 under certain field conditions, since rapid early growth typically limits mortality. Both symbiont types exhibited severe reductions in ¹⁴C incorporation during a 10-h exposure to the electron transport blocking herbicide diuron (DCMU), confirming the link between electron transport through PSII and photosynthate incorporation within the host tissue. These findings advance the current understanding of symbiotic relationships between corals and their symbionts, providing evidence that enhanced growth rates of juvenile corals may result from greater translocation of photosynthates from Symbiodinium C1. Communicated by Biology Editor Dr. Ruth Gates     

Tumor formations in scleractinian corals

A highly localized incidence of skeletal malformations (tumors) in the scleractinian coralsPlatygyra pini andP. sinensis on an inshore fringing reef at Cockle Bay, Magnetic Island within the Great Barrier Reef province is reported. These tumors are typified by a localized area of increased growth rate resulting in roughly circular protuberances extending up to 4.5 cm above the colony's surface. In both species, similar proportions of their populations carried tumors (24.1 % inP. pini and 18.7 % inP. sinensis). Larger colonies (>80 cm in diameter) are at least 7 times more likely to possess tumors than smaller colonies (<40 cm in diameter). X-radiographs of the skeletal malformations indicate a point of origin, presumably from a single budded polyp with subsequent, localized, accelerated growth. The mean radial growth rate of the tumorous area was 29 % greater than that of the surrounding normal regions. In contrast to the normal tissue, the tumorous tissue exhibited proliferation of cells, atrophied gastrodermal cells and mesenterial filaments which were larger and disordered in structure. The environmental conditions at Cockle Bay are relatively extreme with high turbidity, periodic exposure of the reef flat, abrupt changes in salinity during the wet season and mechanical damage to corals caused by unpredictable cyclonic storms. It is suggested that a combination of environmental stresses coupled with an injury inflicted on the corals are possible stimuli that initiate the development of these abnormal growth through either bacterial attack or the development of an aberrant polyp during tissue repair.     

Upper Cretaceous rudist biostratigraphy of the Bey Da?lar? Carbonate Platform, Western Taurides, SW Turkey

The Upper Cretaceous (Middle Cenomanian-Coniacian) successions of the Bey Da?lar? Carbonate Platform (Western Taurides, SW Turkey) are represented by rudist-bearing shallow-water limestones. Four rudist lithosomes are distinguished for the first time from the Eastern, Northern and Southern Areas of the Bey Da?lar? Autochthon. The oldest rudist assemblages dominated by caprinids are observed in the Eastern (Katran Da?) Area (caprinid lithosomes) and suggest a Middle-Late Cenomanian age. The uppermost part of the platform carbonates in the Northern Area is characterized by an association of hippuritid and radiolitid rudist bivalves dominated by Vaccinites praegiganteus (Toucas) (hippuritid lithosomes). The rudist fauna indicates the Late Turonian age, which is confirmed by the previously obtained ⁸⁷Sr/⁸⁶Sr values of well-preserved low-Mg calcite of Vaccinites praegiganteus (Toucas) shells. The rudist associations of the Southern (Susuzda?) Area are represented by two rudist formations. The lower lithosomes are mainly made up of hippuritids and radiolitids (hippuritid-radiolitid lithosomes). The stratigraphical distributions of the species of the assemblage indicate a Santonian-Early Campanian age. The rudist associations of the upper lithosomes are dominated by species of Joufia and Gorjanovicia (Joufia-Gorjanovicia lithosomes), which suggest a Late Campanian-Maastrichtian age. Identification of the rudist lithosomes yields information on the palaeobiogeographic distribution of the rudist species in the eastern Mediterranean region and also on the biostratigraphic frame of the Upper Cretaceous successions of the Bey Da?lar? Carbonate Platform.     

The growth of juvenile snails in water conditioned by snails of a different species

Summary Two species of freshwater snails, Physa acuta and Lymnaea sp. aff. columella, were collected from Asabata marsh, Shizuoka Japan. Individuals of both species inhabit the same plants. Individuals of P. acuta are more abundant than those of L. sp. aff. columella. Experiments were conducted to examine the effect of water conditioned by snails on the growth of 10-day-old juvenile P. acuta snails. Juvenile snails in water conditioned by L. sp. aff. columella grew faster than those in water conditioned by P. acuta or only lettuce. The effects of water conditioned by P. acuta differed among the litters. The results suggest that juvenile P. acuta snails experience accelated growth in the presence of L. sp. aff. columella. The freshwater snails interacted through resource competition as well as through substances disolved in the water.     

Corals in the hottest reefs in the world exhibit symbiont fidelity not flexibility

Reef‐building corals are at risk of extinction from ocean warming. While some corals can enhance their thermal limits by associating with dinoflagellate photosymbionts of superior stress tolerance, the extent to which symbiont communities will reorganize under increased warming pressure remains unclear. Here we show that corals in the hottest reefs in the world in the Persian Gulf maintain associations with the same symbionts across 1.5 years despite extreme seasonal warming and acute heat stress (≥35°C). Persian Gulf corals predominantly associated with Cladocopium (clade C) and most also hosted Symbiodinium (clade A) and/or Durusdinium (clade D). This is in contrast to the neighbouring and milder Oman Sea, where corals associated with Durusdinium and only a minority hosted background levels of Cladocopium. During acute heat stress, the higher prevalence of Symbiodinium and Durusdinium in bleached versus nonbleached Persian Gulf corals indicates that genotypes of these background genera did not confer bleaching resistance. Within symbiont genera, the majority of ITS2 rDNA type profiles were unique to their respective coral species, confirming the existence of host‐specific symbiont lineages. Notably, further differentiation among Persian Gulf sites demonstrates that symbiont populations are either isolated or specialized over tens to hundreds of kilometres. Thermal tolerance across coral species was associated with the prevalence of a single ITS2 intragenomic sequence variant (C3gulf), definitive of the Cladocopium thermophilum group. The abundance of C3gulf was highest in bleaching‐resistant corals and at warmer sites, potentially indicating a specific symbiont genotype (or set of genotypes) that may play a role in thermal tolerance that warrants further investigation. Together, our findings indicate that co‐evolution of host–Symbiodiniaceae partnerships favours fidelity rather than flexibility in extreme environments and under future warming.     

The <Emphasis Type="Italic">Laluzia armini</Emphasis> (gen. et spec. nov.) ecosystem: understanding a deeper-water rudist lithosome from the Early Maastrichtian of Mexico

In the Lower Maastrichtian Cardenas Formation exposed at La Luz (State of San Luis Potosí, east-central Mexico), a shallowing-upwards mixed-clastic-carbonate sequence is exposed. The sequence passes from marls with thin siltstones, through lower and upper hippuritid-rudist-dominated intervals, and into a Durania-dominated interval. This succession shows an increase in grain size upwards and a progressive reworking of rudists upwards (preserved in life position, other than in distinct tempestites, in the lower part; invariably reworked/toppled in the upper part). Epibionts show a change from a serpulid–bryozoan assemblage in the lower sequence to a red algal–rhodolith assemblage in the upper part. Using these data, we argue that the sequence shows a change from a low-energy, relatively deep-water, nutrient-rich environment with low-light intensity in the lower part, to a high-energy, well-lit environment in the upper part. Two rudist species are present: a new multifold hippuritid rudist with cellular outer shell layer, Laluzia armini, that lacks pallial canals in its free valve and has a unique myocardinal pillar arrangement, in the lower part; and Durania in the upper part. Laluzia was adapted to low-energy, low-light, soft-bottom environments that were abundant within the lower part of the sequence exposed in the La Luz section—a very unusual environment for rudists.     

Guard crabs alleviate deleterious effects of vermetid snails on a branching coral

Stony corals provide important structural habitat for microbes, invertebrates, and fishes, which in some cases has led to the evolution of beneficial interactions that may protect corals from environmental factors such as thermal stress, nutrient limitation, competitors, or predators. For example, guard crabs (Trapezia spp.) protect corals (Pocillopora sp.) from attacks by crown-of-thorn seastar and sedimentation. Here, a field experiment demonstrates that guard crabs (Trapezia serenei) also ameliorate the strong negative effects of the giant vermetid (Dendropoma maximum) on growth of Pocillopora. This experiment highlights the importance of this crab-coral mutualism: guard crabs facilitate the growth of corals in stressful environments (e.g., where vermetids are abundant), thereby preserving the ecological goods and services (e.g., food and shelter) that these corals may provide to other reef-associated species.     

Real-time PCR reveals a high incidence of <Emphasis Type="Italic">Symbiodinium </Emphasis>clade D at low levels in four scleractinian corals across the Great Barrier Reef: implications for symbiont shuffling

Reef corals form associations with an array of genetically and physiologically distinct endosymbionts from the genus Symbiodinium. Some corals harbor different clades of symbionts simultaneously, and over time the relative abundances of these clades may change through a process called symbiont shuffling. It is hypothesized that this process provides a mechanism for corals to respond to environmental threats such as global warming. However, only a minority of coral species have been found to harbor more than one symbiont clade simultaneously and the current view is that the potential for symbiont shuffling is limited. Using a newly developed real-time PCR assay, this paper demonstrates that previous studies have underestimated the presence of background symbionts because of the low sensitivity of the techniques used. The assay used here targets the multi-copy rDNA ITS1 region and is able to detect Symbiodinium clades C and D with >100-fold higher sensitivity compared to conventional techniques. Technical considerations relating to intragenomic variation, estimating copy number and non-symbiotic contamination are discussed. Eighty-two colonies from four common scleractinian species (Acropora millepora, Acropora tenuis, Stylophora pistillata and Turbinaria reniformis) and 11 locations on the Great Barrier Reef were tested for background Symbiodinium clades. Although these colonies had been previously identified as harboring only a single clade based on SSCP analyses, background clades were detected in 78% of the samples, indicating that the potential for symbiont shuffling may be much larger than currently thought.