Learned recognition of novel predator odour by convict cichlid embryos

Predation exerts tremendous selection pressure on all organisms. In this study, we exposed embryos of convict cichlids (Amatitlania siquia) twice daily to one of the following: (1) chemical alarm cues of damaged conspecifics + odour of a novel predator (Polypterus endlicheri), (2) chemical alarm cues of damaged conspecifics + water or (3) blank water. No chemical cues were presented after the eggs hatched. When the larvae were 9 days old (mean total length?=?5.7 mm), they were exposed to either predator odour or water. Those larvae that had been conditioned as embryos on alarm cues + predator odour showed a significant reduction in activity (i.e. anti-predator behavioural response) to predator odour relative to the other treatments. This is the first demonstration of acquired predator recognition by fish embryos.     

Reproductive interference via interspecific pairing in an amphipod species complex

Many species experience reproductive interference defined as interspecific mating interactions that reduce the fitness of individuals in at least one of the species. We examined reproductive interference among three cryptic amphipod species that co-occur in the vegetated zone of lakes. Because these animals form precopulatory pairs and males commonly have indiscriminant mating behavior, we predicted that (1) there would be interspecific pairing, (2) interspecific pairing would be more common when conspecifics were rare, and (3) interspecific pairing would be more common in species combinations where males are larger than females. Using color phenotypes to distinguish species, a novel discovery reported here, we conducted experiments to evaluate patterns of interspecific pairing. In a no-choice experiment (i.e., amphipods had access to mates of only one species), we observed a low rate (5 %) of interspecific pairing and 80 % of these cases involved males that were larger than females. In a second experiment where individuals had access to conspecific mates at varying relative abundance, only 0.04 % of the pairs observed were between heterospecifics, suggesting that the interspecific pairing observed in the no-choice experiment was an artifact of not having access to conspecific mates. Our results suggest that at least one sex has sufficient species-recognition abilities to circumvent the formation of interspecific pairs; therefore, reproductive interference may be minimal in these species.     

Future ocean acidification will be amplified by hypoxia in coastal habitats

Ocean acidification is elicited by anthropogenic carbon dioxide emissions and resulting oceanic uptake of excess CO₂ and might constitute an abiotic stressor powerful enough to alter marine ecosystem structures. For surface waters in gas-exchange equilibrium with the atmosphere, models suggest increases in CO₂ partial pressure (pCO₂) from current values of ca. 390 μatm to ca. 700–1,000 μatm by the end of the century. However, in typically unequilibrated coastal hypoxic regions, much higher pCO₂ values can be expected, as heterotrophic degradation of organic material is necessarily related to the production of CO₂ (i.e., dissolved inorganic carbon). Here, we provide data and estimates that, even under current conditions, maximum pCO₂ values of 1,700–3,200 μatm can easily be reached when all oxygen is consumed at salinities between 35 and 20, respectively. Due to the nonlinear nature of the carbonate system, the approximate doubling of seawater pCO₂ in surface waters due to ocean acidification will most strongly affect coastal hypoxic zones as pCO₂ during hypoxia will increase proportionally: we calculate maximum pCO₂ values of ca. 4,500 μatm at a salinity of 20 (T = 10 °C) and ca. 3,400 μatm at a salinity of 35 (T = 10 °C) when all oxygen is consumed. Upwelling processes can bring these CO₂-enriched waters in contact with shallow water ecosystems and may then affect species performance there as well. We conclude that (1) combined stressor experiments (pCO₂ and pO₂) are largely missing at the moment and that (2) coastal ocean acidification experimental designs need to be closely adjusted to carbonate system variability within the specific habitat. In general, the worldwide spread of coastal hypoxic zones also simultaneously is a spread of CO₂-enriched zones. The magnitude of expected changes in pCO₂ in these regions indicates that coastal systems may be more endangered by future global climate change than previously thought.     

Biological impacts of ocean acidification: a postgraduate perspective on research priorities

Research into the effects of ocean acidification (OA) on marine organisms has greatly increased during the past decade, as realization of the potential dramatic impacts has grown. Studies have revealed the multifarious responses of organisms to OA conditions, indicating a high level of intra- and interspecific variation in species’ ability to accommodate these alterations. If we are to provide policy makers with sound, scientific input regarding the expected consequences of OA, we need a broader understanding of these predicted changes. As a group of 20 multi-disciplinary postgraduate students from around the globe, with a study focus on OA, we are a strong representation of ‘next generation’ scientists in this field. In this unique cumulative paper, we review knowledge gaps in terms of assessing the biological impacts of OA, outlining directions for future research.     

The physiological and molecular responses of larvae from the reef-building coral Pocillopora damicornis exposed to near-future increases in temperature and pCO2

Given the threats of greenhouse gas emissions and a changing climate to marine ecosystems, there is an urgent need to better understand the response of not only adult corals, which are particularly sensitive to environmental changes, but also their larvae, whose mechanisms of acclimation to both temperature increases and ocean acidification are not well understood. Brooded larvae from the reef coral Pocillopora damicornis collected from Nanwan Bay, Southern Taiwan, were exposed to ambient or elevated temperature (25 or 29 °C) and pCO₂ (415 or 635 μatm) in a factorial experiment for 9 days, and a variety of physiological and molecular parameters were measured. Respiration and rubisco protein expression decreased in larvae exposed to elevated temperature, while those incubated at high pCO₂ were larger in size. Collectively, these findings highlight the complex metabolic and molecular responses of this life history stage and the need to integrate our understanding across multiple levels of biological organization. Our results also suggest that for this pocilloporid larval life stage, the impacts of elevated temperature are likely a greater threat under near-future predictions for climate change than ocean acidification.     

Temporal patterns of settlement, recruitment and post-settlement losses in a rocky reef fish assemblage in the South-Western Mediterranean Sea

Post-settlement events can significantly alter the density distribution of settlers and subsequently the adult population structure. The temporal and inter-annual variability of settlement and the effects of mortality on recruitment were investigated across 2 years in the vicinities of Cabo de Palos–Islas Hormigas Marine Reserve by visual census and light trap sampling. Settlement was seasonal with greater species richness and abundance in summer. Although temporal synchronization was observed between larval supply and settlement, densities of settlers could not be predicted from post-larval abundances. Timing of settlement was consistent between years but with high inter-annual variation in abundance. High mortality (~80 %) and general decoupling between post-larval and settlement stages suggest that early mortality is driving such patterns. Nevertheless, indications of habitat-mediated mortality were found for benthic species such as Symphodus and Diplodus, highlighting the importance of habitat in shaping population demography.     

Novel molecular fingerprinting of marine avian diet provides a tool for gaining insights into feeding ecology

C₂₅ highly branched isoprenoids (HBIs) are produced by a relatively small number of diatom species, yet are common constituents of almost all marine environments. Previously, detection of HBIs in a few aquatic Arctic animals has indicated the potential use of these lipids for providing novel ecological information. In the current study, analysis of lipid extracts of livers from Leach’s storm petrel (Oceanodroma leucorhoa) and Brunnich’s guillemot (Uria lomvia) facilitated identification and quantification of HBI isomers. HBIs were found in the tissues of all specimens with clear differences in the abundances and distributions of individual HBI isomers both between Atlantic as well as Arctic birds. These differences are consistent with contrasting oceanographic regimes and suggests that regional differences in HBIs are reflected in the tissues of consumers. Tissue-specific assessment of HBI distributions has also revealed the presence of these lipids in muscle for the first time. This study represents the first report of HBI lipids in birds and provides evidence that these lipids are transferred across trophic levels and extends their potential use as chemical tracers beyond the ecology of aquatic organisms.     

Efficient preparation of greener N-doped carbon nanotube composites for water treatment by the microwave polyol method

N-doped carbon nanotubes have unique structures and strong interactions with metal nanoparticles due to the presence of nitrogen. There is actually a need for nanoparticles to treat water, without leaching of toxic metals. Here, we synthesized nanocomposites by deposition of Ag and Fe nanoparticles on N-doped carbon nanotubes with a surface area of 52 m²/g and 2 % N content to form nanocomposites. Transmission electron microscopy (TEM) of the nanocomposites revealed that the best dispersion of the deposited nanoparticles was achieved by the microwave-assisted polyol method. The Ag and Fe nanoparticles were indeed monodispersed and uniformly distributed on the surface of the N-doped carbon nanotubes. Deposition could be achieved in 5 min. The wet impregnation and deposition–precipitation methods gave composites with agglomerated nanoparticles. We observed that leaching of Fe and Ag into water was also influenced by the preparation method. No leaching of nanoparticles was observed when the composites were prepared by the microwave polyol method. This synthesis is therefore efficient with less energy and time. The strong metal/N-doped carbon nanotube interactions render these composites suitable for use in water purification.     

Ostrich chick humoral immune responses and growth rate are predicted by parental immune responses and paternal colouration

One of the most important measures of offspring performance is growth rate, which is often traded off against another important survival trait, immune function. A particular feature of ostrich chicks maintained in farmed environments is that cohorts of chicks vary widely in size. As parents can have a profound effect on the phenotype and fitness of their offspring, we investigated whether chick growth and immune defence were related to variation in levels of immune defence in their genetic parents. As secondary sexual traits of sires could serve as indicators of male quality, and be used in female mating decisions, we also investigated whether chick growth rate and immune defence were related to male plumage and integumentary colouration. We found that offspring growth rates and humoral responses were related to the humoral responses of their parents, suggesting that at least some components of humoral immune capacity are heritable. The white colour of male ostrich feathers was correlated to the humoral response and growth rate of their offspring, suggesting that this visual cue involved in the male courtship display could serve as an important signal to females of male quality, thereby forming the basis of mate choice in this species.