Showing papers in "Advances in Marine Biology in 2011"

Biology of deep-water octocorals.

Abstract: Publisher Summary This chapter discusses the taxonomy, phylogeny, biogeography, ecology, and reproductive biology of deep-sea octocorals and also focuses on gorgonian octocorals because they are the predominant octocoral group in the deep sea. The most widely accepted taxonomic scheme for octocorals divides the subclass into four orders: (1) helioporacea, (2) alcyonacea, (3) gorgonacea, and (4) pennatulacea. The distinctions between most orders and suborders are blurred by intermediate taxa that resulted in a continuum of colonial organization and skeletal structure. The major areas of study of deep-sea gorgonians and sources of species descriptions are also summarized. Octocorals have been known from deep water in the North Atlantic, although the Challenger expedition showed that octocorals could be found in the depths of all oceans. Knowledge of deep-water octocorals of the Indo-West Pacific region is meagre and contrasts with the wealth of information on shallow-water taxa. The distribution of the three major deep-sea families' discussed are––chrysogorgiidae, isididae, and primnoidae. Deep-sea octocoral colonies are often large so it offers a wide range of biogenic habitats to other invertebrate species. The chapter also focuses on those invertebrate species that are found most frequently on the octocoral host. Reproduction, growth, age, food habits, and conservation issues are also considered.

Stress Ecology in Fucus: Abiotic, Biotic and Genetic Interactions

Abstract: Stress regimes defined as the synchronous or sequential action of abiotic and biotic stresses determine the performance and distribution of species. The natural patterns of stress to which species are more or less well adapted have recently started to shift and alter under the influence of global change. This was the motivation to review our knowledge on the stress ecology of a benthic key player, the macroalgal genus Fucus. We first provide a comprehensive review of the genus as an ecological model including what is currently known about the major lineages of Fucus species with respect to hybridization, ecotypic differentiation and speciation; as well as life history, population structure and geographic distribution. We then review our current understanding of both extrinsic (abiotic/biotic) and intrinsic (genetic) stress(es) on Fucus species and how they interact with each other. It is concluded that (i) interactive stress effects appear to be equally distributed over additive, antagonistic and synergistic categories at the level of single experiments, but are predominantly additive when averaged over all studies in a meta-analysis of 41 experiments; (ii) juvenile and adult responses to stress frequently differ and (iii) several species or particular populations of Fucus may be relatively unaffected by climate change as a consequence of pre-adapted ecotypes that collectively express wide physiological tolerences. Future research on Fucus should (i) include additional species, (ii) include marginal populations as models for responses to environmental stress; (iii) assess a wider range of stress combinations, including their temporal fluctuations; (iv) better differentiate between stress sensitivity of juvenile versus adult stages; (v) include a functional genomic component in order to better integrate Fucus' ecological and evolutionary responses to stress regimes and (vi) utilize a multivariate modelling approach in order to develop and understand interaction networks.

Tipping points, thresholds and the keystone role of physiology in marine climate change research.

Abstract: The ongoing and future effects of global climate change on natural and human-managed ecosystems have led to a renewed interest in the concept of ecological thresholds or tipping points. While generalizations such as poleward range shifts serve as a useful heuristic framework to understand the overall ecological impacts of climate change, sophisticated approaches to management require spatially and temporally explicit predictions that move beyond these oversimplified models. Most approaches to studying ecological thresholds in marine ecosystems tend to focus on populations, or on non-linearities in physical drivers. Here we argue that many of the observed thresholds observed at community and ecosystem levels can potentially be explained as the product of non-linearities that occur at three scales: (a) the mechanisms by which individual organisms interact with their ambient habitat, (b) the non-linear relationship between organismal physiological performance and variables such as body temperature and (c) the indirect effects of physiological stress on species interactions such as competition and predation. We explore examples at each of these scales in detail and explain why a failure to consider these non-linearities – many of which can be counterintuitive – can lead to Type II errors (a failure to predict significant ecological responses to climate change). Specifically, we examine why ecological thresholds can occur well before concomitant thresholds in physical drivers are observed, i.e. how even small linear changes in the physical environment can lead to ecological tipping points. We advocate for an integrated framework that combines biophysical, ecological and physiological methods to generate hypotheses that can be tested using experimental manipulation as well as hindcasting and nowcasting of observed change, on a spatially and temporally explicit basis.

p53 Superfamily Proteins in Marine Bivalve Cancer and Stress Biology

Abstract: The human p53 tumour suppressor protein is inactivated in many cancers and is also a major player in apoptotic responses to cellular stress The p53 protein and the two other members of this protein family (p63, p73) are encoded by distinct genes and their functions have been extensively documented for humans and some other vertebrates The structure and relative expression levels for members of the p53 superfamily have also been reported for most major invertebrate taxa The functions of homologous proteins have been investigated for only a few invertebrates (specifically, p53 in flies, nematodes and recently a sea anemone) These studies of classical model organisms all suggest that the gene family originally evolved to mediate apoptosis of damaged germ cells or to protect germ cells from genotoxic stress Here, we have correlated data from a number of molluscan and other invertebrate sequencing projects to provide a framework for understanding p53 signalling pathways in marine bivalve cancer and stress biology These data suggest that (a) the two identified p53 and p63/73-like proteins in soft shell clam ( Mya arenaria ), blue mussel ( Mytilus edulis ) and Northern European squid ( Loligo forbesi ) have identical core sequences and may be splice variants of a single gene, while some molluscs and most other invertebrates have two or more distinct genes expressing different p53 family members; (b) transcriptional activation domains (TADs) in bivalve p53 and p63/73-like protein sequences are 67–69% conserved with human p53, while those in ecdysozoan, cnidarian, placozoan and choanozoan eukaryotes are ≤33% conserved; (c) the Mdm2 binding site in the transcriptional activation domain is 100% conserved in all sequenced bivalve p53 proteins (eg Mya , Mytilus , Crassostrea and Spisula ) but is not present in other non-deuterostome invertebrates; (d) an Mdm2 homologue has been cloned for Mytilus trossulus ; (e) homologues for both human p53 upstream regulatory and transcriptional target genes exist in molluscan genomes (missing are ARF, CIP1 and BH3 only proteins) and (f) p53 is demonstrably involved in bivalve haemocyte and germinoma cancers We usually do not know enough about the molecular biology of marine invertebrates to address molecular mechanisms that characterize particular diseases Understanding the molecular basis of naturally occurring diseases in marine bivalves is a virtually unexplored aspect of toxicoproteomics and genomics and related drug discovery Additionally, increases in coastal development and concomitant increases in aquatic pollutants have driven interest in developing models appropriate for evaluating potential hazardous compounds or conditions found in the aquatic environment Data reviewed in this study are coupled with recent developments in our understanding the molecular biology of the marine bivalve p53 superfamily Taken together, they suggest that both structurally and functionally , bivalve p53 family proteins are the most highly conserved members of this gene superfamily so far identified outside of higher vertebrates and invertebrate chordates Marine bivalves provide some of the most relevant and best understood models currently available for experimental studies by biomedical and marine environmental researchers

Social aggregation in the pelagic zone with special reference to fish and invertebrates.

Abstract: Aggregations of organisms, ranging from zooplankton to whales, are an extremely common phenomenon in the pelagic zone; perhaps the best known are fish schools. Social aggregation is a special category that refers to groups that self-organize and maintain cohesion to exploit benefits such as protection from predators, and location and capture of resources more effectively and with greater energy efficiency than could a solitary individual. In this review we explore general aggregation principles, with specific reference to pelagic organisms; describe a range of new technologies either designed for studying aggregations or that could potentially be exploited for this purpose; report on the insights gained from theoretical modelling; discuss the relationship between social aggregation and ocean management; and speculate on the impact of climate change. Examples of aggregation occur in all animal phyla. Among pelagic organisms, it is possible that repeated co-occurrence of stable pairs of individuals, which has been established for some schooling fish, is the likely precursor leading to networks of social interaction and more complex social behaviour. Social network analysis has added new insights into social behaviour and allows us to dissect aggregations and to examine how the constituent individuals interact with each other. This type of analysis is well advanced in pinnipeds and cetaceans, and work on fish is progressing. Detailed three-dimensional analysis of schools has proved to be difficult, especially at sea, but there has been some progress recently. The technological aids for studying social aggregation include video and acoustics, and have benefited from advances in digitization, miniaturization, motion analysis and computing power. New techniques permit three-dimensional tracking of thousands of individual animals within a single group which has allowed novel insights to within-group interactions. Approaches using theoretical modelling of aggregations have a long history but only recently have hypotheses been tested empirically. The lack of synchrony between models and empirical data, and lack of a common framework to schooling models have hitherto hampered progress; however, recent developments in this field offer considerable promise. Further, we speculate that climate change, already having effects on ecosystems, could have dramatic effects on aggregations through its influence on species composition by altering distribution ranges, migration patterns, vertical migration, and oceanic acidity. Because most major commercial fishing targets schooling species, these changes could have important consequences for the dependent businesses.

Ultraviolet radiation and echinoderms: past, present and future perspectives.

Abstract: There is general consensus that solar ultraviolet radiation (UVR) negatively impacts many marine species. Echinoderms are ubiquitous within the marine environment, with members of the phyla often long-lived and numerically dominant within the benthic macrofauna, consequently the impact of UVR on the population dynamics of these organisms will influence marine communities and ecosystems. Research to date has shown that exposure of echinoderms to solar UVR can, affect reproduction and development, change behaviour, cause numerous biochemical and physiological changes and potentially cause increased mutation rates, by causing DNA damage. There is also considerable evidence that echinoderms utilise several different mechanisms to protect themselves against excessive UVR and subsequent UVR-induced damage. However, these protective mechanisms may pose conflicting selection pressures on echinoderms, as UVR is an additional stressor in oceans subjected to anthropogenic-induced climate change. This review summarises our knowledge of the effects of UVR on the Echinodermata. We outline the research conducted to date, highlight key studies on UVR that have utilised echinoderms and look to the future of UVR research in a rapidly changing ocean.

Learning to read the oceans genomics of marine phytoplankton.

Abstract: The phytoplankton are key members of marine ecosystems, generating about half of global primary productivity, supporting valuable fisheries and regulating global biogeochemical cycles. Marine phytoplankton are phylogenetically diverse and are comprised of both prokaryotic and eukaryotic species. In the last decade, new insights have been gained into the ecology and evolution of these important organisms through whole genome sequencing projects and more recently, through both transcriptomics and targeted metagenomics approaches. Sequenced genomes of cyanobacteria are generally small, ranging in size from 1.8 to 9 million base pairs (Mbp). Eukaryotic genomes, in general, have a much larger size range and those that have been sequenced range from 12 to 57 Mbp. Whole genome sequencing projects have revealed key features of the evolutionary history of marine phytoplankton, their varied responses to environmental stress, their ability to scavenge and store nutrients and their unique ability to form elaborate cellular coverings. We have begun to learn how to read the ‘language’ of marine phytoplankton, as written in their DNA. Here, we review the ecological and evolutionary insights gained from whole genome sequencing projects, illustrate how these genomes are yielding information on marine natural products and informing nanotechnology as well as make suggestions for future directions in the field of marine phytoplankton genomics.

Hydrozoans and the shape of things to come.

Abstract: The physiological mechanisms that regulate adaptive plasticity of clonal organisms are key to their success in changing environments. Here, we review the mechanisms that regulate morphological plasticity of colonial hydrozoans. There is a heritable, genetic basis to colony form, but environmentally-induced plasticity and self-reinforcing developmental physiology explain much of total phenotypic variance. Morphological development of colonial hydrozoans emerges from interactions among (1) behaviors which drive gastrovascular transport, (2) architecture of the gastrovascular system that determines hydrodynamic characteristics of vascular flow, and, (3) gene products that vary in response to physiological signals provided by gastrovascular transport. Several morphogenetic signaling mechanisms have been identified, including, reactive oxygen species and nutrient concentrations in the hydroplasm, and hydromechanical forces associated with gastrovascular transport. We present a conceptual model of the interacting forces that drive hydrozoan morphological development. Several avenues for future research are suggested by the synthesis of information from prior studies of hydrozoans. Elucidating the morphogenetic signaling pathways responsive to metabolites or hydromechanical forces and the epigenetic effect of vascular architecture on colony form may give new insight into the self-maintenance of indeterminately growing and continuously developing vascular systems.