New branched Porolithon species (Corallinales, Rhodophyta) from the Great Barrier Reef, Coral Sea, and Lord Howe Island.

Porolithon is one of the most ecologically important genera of tropical and subtropical crustose (non-geniculate) coralline algae growing abundantly along the shallow margins of coral reefs and functioning to cement reef frameworks. Thalli of branched, fruticose Porolithon specimens from the Indo-Pacific Ocean traditionally have been called P. gardineri, while massive, columnar forms have been called P. craspedium. Sequence comparisons of the rbcL gene both from type specimens of P. gardineri and P. craspedium and from field-collected specimens demonstrate that neither species is present in east Australia and instead resolve into four unique genetic lineages. Porolithon howensis sp. nov. forms columnar protuberances and loosely attached margins and occurs predominantly at Lord Howe Island; P. lobulatum sp. nov. has fruticose to clavate forms and free margins that are lobed and occurs in the Coral Sea and on the Great Barrier Reef (GBR); P. parvulum sp. nov. has short (<2 cm), unbranched protuberances and attached margins and is restricted to the central and southern GBR; and P. pinnaculum sp. nov. has a mountain-like, columnar morphology and occurs on oceanic Coral Sea reefs. A rbcL gene sequence of the isotype of P. castellum demonstrates it is a different species from other columnar species. In addition to the diagnostic rbcL and psbA marker sequences, the four new species may be distinguished by a combination of features including thallus growth form, margin shape (attached or unattached), and medullary system (coaxial or plumose). Porolithon species, because of their ecological importance and sensitivity to ocean acidification, need urgent documentation of their taxonomic diversity.

Settlement cue selectivity by larvae of the destructive crown-of-thorns starfish.

Population irruptions of crown-of-thorns starfish (COTS) cause extensive degradation of coral reefs, threatening the structure and function of these important ecosystems. For population irruptions to initiate and spread, large numbers of planktonic larvae have to successfully transition into their benthic life-history stage (i.e. settlement), whereby larval behaviour and the presence of settlement cues may shape spatial patterns of recruitment and adult densities. Our results demonstrate that a wide range of coralline algae species induce COTS larvae to settle; however, the capacity to promote settlement success varied manyfold among algal species, ranging from greater than 90% in Melyvonnea cf. madagascariensis to less than 2% in Lithophyllum cf. kotschyanum and two Porolithon species at 24 h. Because many coralline algae species that promote high settlement success are prevalent in shallow reef habitats, our findings challenge the hypothesis that COTS larvae predominantly settle in deep water. Considering both larval behaviour and algal ecology, this study highlights the ecological significance of coralline algae communities in driving recruitment patterns of COTS. More specifically, the local abundance of highly inductive coralline algae (especially, Melyvonnea cf. madagascariensis) may explain some of the marked spatial heterogeneity of COTS populations and the incidence of population irruptions.

Microbes from Mum: symbiont transmission in the tropical reef sponge Ianthella basta.

Most marine sponge species harbour distinct communities of microorganisms which contribute to various aspects of their host's health and physiology. In addition to their key roles in nutrient transformations and chemical defence, these symbiotic microbes can shape sponge phenotype by mediating important developmental stages and influencing the environmental tolerance of the host. However, the characterisation of each microbial taxon throughout a sponge's life cycle remains challenging, with several sponge species hosting up to 3000 distinct microbial species. Ianthella basta, an abundant broadcast spawning species in the Indo-Pacific, is an emerging model for sponge symbiosis research as it harbours only three dominant symbionts: a Thaumarchaeotum, a Gammaproteobacterium, and an Alphaproteobacterium. Here, we successfully spawned Ianthella basta, characterised its mode of reproduction, and used 16S rRNA gene amplicon sequencing, fluorescence in situ hybridisation, and transmission electron microscopy to characterise the microbial community throughout its life cycle. We confirmed I. basta as being gonochoric and showed that the three dominant symbionts, which together make up >90% of the microbiome according to 16S rRNA gene abundance, are vertically transmitted from mother to offspring by a unique method involving encapsulation in the peri-oocytic space, suggesting an obligate relationship between these microbes and their host.

In situ responses of the sponge microbiome to ocean acidification.

Climate change is causing rapid changes in reef structure, biodiversity, and function, though most sponges are predicted to tolerate conditions projected for 2100. Sponges maintain intimate relationships with microbial symbionts, with previous studies suggesting that microbial flexibility may be pivotal to success under ocean acidification (OA). We performed a reciprocal transplantation of the coral reef sponges Coelocarteria singaporensis and Stylissa cf. flabelliformis between a control reef site and an adjacent CO2 vent site in Papua New Guinea to explore how the sponge microbiome responds to OA. Microbial communities of C. singaporensis, which differed initially between sites, did not shift towards characteristic control or vent microbiomes, even though relative abundances of Chloroflexi and Cyanobacteria increased and that of Thaumarchaeota decreased 7 months after transplantation to the control site. Microbial communities of S. cf. flabelliformis, which were initially stable between sites, did not respond specifically to transplantation but collectively exhibited a significant change over time, with a relative increase in Thaumarchaeota and decrease in Proteobacteria in all treatment groups. The lack of a community shift upon transplantation to the vent site suggests that microbial flexibility, at least in the adult life-history stage, does not necessarily underpin host survival under OA .

Larval settlement: the role of surface topography for sessile coral reef invertebrates.

For sessile marine invertebrates with complex life cycles, habitat choice is directed by the larval phase. Defining which habitat-linked cues are implicated in sessile invertebrate larval settlement has largely concentrated on chemical cues which are thought to signal optimal habitat. There has been less effort establishing physical settlement cues, including the role of surface microtopography. This laboratory based study tested whether surface microtopography alone (without chemical cues) plays an important contributing role in the settlement of larvae of coral reef sessile invertebrates. We measured settlement to tiles, engineered with surface microtopography (holes) that closely matched the sizes (width) of larvae of a range of corals and sponges, in addition to surfaces with holes that were markedly larger than larvae. Larvae from two species of scleractinian corals (Acropora millepora and Ctenactis crassa) and three species of coral reef sponges (Luffariella variabilis, Carteriospongia foliascens and Ircinia sp.,) were used in experiments. L. variabilis, A. millepora and C. crassa showed markedly higher settlement to surface microtopography that closely matched their larval width. C. foliascens and Ircinia sp., showed no specificity to surface microtopography, settling just as often to microtopography as to flat surfaces. The findings of this study question the sole reliance on chemical based larval settlement cues, previously established for some coral and sponge species, and demonstrate that specific physical cues (surface complexity) can also play an important role in larval settlement of coral reef sessile invertebrates.

Microwave purification of large-area horizontally aligned arrays of single-walled carbon nanotubes.

Recent progress in the field of single-walled carbon nanotubes (SWNTs) significantly enhances the potential for practical use of this remarkable class of material in advanced electronic and sensor devices. One of the most daunting challenges is in creating large-area, perfectly aligned arrays of purely semiconducting SWNTs (s-SWNTs). Here we introduce a simple, scalable, large-area scheme that achieves this goal through microwave irradiation of aligned SWNTs grown on quartz substrates. Microstrip dipole antennas of low work-function metals concentrate the microwaves and selectively couple them into only the metallic SWNTs (m-SWNTs). The result allows for complete removal of all m-SWNTs, as revealed through systematic experimental and computational studies of the process. As one demonstration of the effectiveness, implementing this method on large arrays consisting of ~20,000 SWNTs completely removes all of the m-SWNTs (~7,000) to yield a purity of s-SWNTs that corresponds, quantitatively, to at least to 99.9925% and likely significantly higher.

Using nanoscale thermocapillary flows to create arrays of purely semiconducting single-walled carbon nanotubes.

Among the remarkable variety of semiconducting nanomaterials that have been discovered over the past two decades, single-walled carbon nanotubes remain uniquely well suited for applications in high-performance electronics, sensors and other technologies. The most advanced opportunities demand the ability to form perfectly aligned, horizontal arrays of purely semiconducting, chemically pristine carbon nanotubes. Here, we present strategies that offer this capability. Nanoscale thermocapillary flows in thin-film organic coatings followed by reactive ion etching serve as highly efficient means for selectively removing metallic carbon nanotubes from electronically heterogeneous aligned arrays grown on quartz substrates. The low temperatures and unusual physics associated with this process enable robust, scalable operation, with clear potential for practical use. We carry out detailed experimental and theoretical studies to reveal all of the essential attributes of the underlying thermophysical phenomena. We demonstrate use of the purified arrays in transistors that achieve mobilities exceeding 1,000 cm(2) V(-1) s(-1) and on/off switching ratios of ∼10,000 with current outputs in the milliamp range. Simple logic gates built using such devices represent the first steps toward integration into more complex circuits.

Electrostatic dimension of aligned-array carbon nanotube field-effect transistors.

Accurate electrostatics modeling of nanotubes (NTs)/nanowires (NWs) has significant implications for the ultimate scalability of aligned-array NT/NW field-effect transistors (FETs). The analysis to date has focused on limits of capacitive coupling between the 1D channel and 2D gate that is strictly relevant only in the linear response operation of NT/NW-FETs. Moreover, the techniques of electrostatic doping by independent gates that cover only part of the channel are widely used, but the nature of its electrostatic coupling has not been explored. In this paper, we use a three-dimensional, self-consistent model for NT/NW-FETs to interpret the essence of electrostatic coupling with complex configuration of electrode geometries. The interplay between 3D electric fields and its 1D termination onto the NTs/NWs suggests surprising complexity of electrostatic interaction not captured in simpler models. This coupling can change the performance metrics such as ON and OFF currents by orders of magnitude depending on (1) NT/NW density, (2) bias voltage, and (3) gate overlap length. Remarkably, this parasitic coupling persists regardless of the gate oxide thickness, changes in dielectric constant, and/or the width of the diameter distribution of NTs/NWs. The predictions of the model are systematically validated by a series of experiments.

Electroluminescence in aligned arrays of single-wall carbon nanotubes with asymmetric contacts.

High quantum efficiencies and low current thresholds are important properties for all classes of semiconductor light emitting devices (LEDs), including nanoscale emitters based on single wall carbon nanotubes (SWNTs). Among the various configurations that can be considered in SWNT LEDs, two terminal geometries with asymmetric metal contacts offer the simplest solution. In this paper, we study, experimentally and theoretically, the mechanisms of electroluminescence in devices that adopt this design and incorporate perfectly aligned, horizontal arrays of individual SWNTs. The results suggest that exciton mediated electron-hole recombination near the lower work-function contact is the dominant source of photon emission. High current thresholds for electroluminescence in these devices result from diffusion and quenching of excitons near the metal contact.

Calciphylaxis after parathyroidectomy in chronic renal failure.

A 33-year-old man, who was maintained on hemodialysis for more than 9 years, was diagnosed to have secondary hyperparathyroidism with a nodule in a parathyroid gland revealed with ultrasound and CT scan. He underwent parathyroidectomy and presented with bilateral lower limb painful ulcers two months later. Skin biopsy from these ulcers was consistent with calciphylaxis.