Publisher Correction: Tidal and diel orchestration of behaviour and gene expression in an intertidal mollusc.

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Tidal and diel orchestration of behaviour and gene expression in an intertidal mollusc.

Intertidal inhabitants are exposed to the 24-hour solar day, and the 12.4 hour rising and falling of the tides. One or both of these cycles govern intertidal organisms' behaviour and physiology, yet little is known about the molecular clockworks of tidal rhythmicity. Here, we show that the limpet Cellana rota exhibits robust tidally rhythmic behaviour and gene expression. We assembled a de-novo transcriptome, identifying novel tidal, along with known circadian clock genes. Surprisingly, most of the putative circadian clock genes, lack a typical rhythmicity. We identified numerous tidally rhythmic genes and pathways commonly associated with the circadian clock. We show that not only is the behaviour of an intertidal organism in tune with the tides, but so too are many of its genes and pathways. These findings highlight the plasticity of biological timekeeping in nature, strengthening the growing notion that the role of 'canonical' circadian clock genes may be more fluid than previously thought, as exhibited in an organism which has evolved in an environment where tidal oscillations are the dominant driving force.

Differential gene expression in Symbiodinium microadriaticum clade B following stress.

Coral bleaching is caused by the loss of symbiont zooxanthellae and/or decrease in their pigments. Since the algal symbionts provide the energy basis for corals and whole reefs, their loss or impairment of function leads to widespread mortality. This phenomenon has been documented numerous times in recent years, and has extensively damaged coral reefs all over the world. Temperature has been found to be the major cause of bleaching, and rising sea temperatures have increased the frequency of these catastrophic episodes. To characterize the response of zooxanthellae to temperature stress at the molecular level, we used the mRNA differential display technique to monitor changes in the abundance of specific mRNA species in the cell under different temperature conditions. Axenically grown zooxanthellae were exposed to a range of temperatures (21.7, 17, 26 degrees C) before extraction of their mRNA. Of numerous differentially expressed sequences, seven mRNA species were amplified by the polymerase chain reaction (PCR) and sequenced. One of those sequences was positively identified as encoding a multifunction cell surface aminopeptidase, dipeptidyl peptidase IV, which is active in cell matrix adhesion. Our work illustrates the power of the differential display technique as a useful tool to study the response of zooxanthellae to stressors.

Phylogeny of coral-inhabiting barnacles (Cirripedia; Thoracica; Pyrgomatidae) based on 12S, 16S and 18S rDNA analysis.

The traditional phylogeny of the coral-inhabiting barnacles, the Pyrgomatidae, is based on morphological characteristics, mainly of the hard parts. It has been difficult to establish the phylogenetic relationships among Pyrgomatidae because of the apparent convergence of morphological characteristics, and due to the use of non-cladistic systematics, which emphasize ancestor-descendant relationships rather than sister-clade relationships. We used partial sequences of two mithochondrial genes, 12S rDNA and 16S rDNA, and a nuclear gene, 18S rDNA, to infer the molecular phylogeny of the pyrgomatids. Our phylogenetic results allowed us to reject previous classifications of Pyrgomatidae based on morphological characteristics. Our results also suggested the possibility of paraphyly of the Pyrgomatidae. The hydrocoral barnacle Wanella is not found on the same clade as the other pyrgomatids, but rather, with the free-living balanids. The basal position of Megatrema and Ceratoconcha is supported. The archeaobalanid Armatobalanus is grouped with Cantellius at the base of the Indo-Pacific pyrgomatines. Fusion of the shell plate and modification of the opercular valves are homoplasious features that occurred more than three times on different clades. The monophyly of the "Savignium" group, comprising four nominal genera, is also not supported, and the different taxa are placed on different clades.