Driven by speculation, not by impact - the effects of plastic on fish species.

Plastic products have facilitated the daily lives of an exponentially increasing world population for over 70 years, whilst inadvertently creating one of the most topical environmental issues of the 21st Century: the plastic pollution crisis. Since the mid-20th Century, plastic production has expanded continuously to global production levels of over 350 million tons in 2018 (Thompson et al. 2009; Plastics Europe, 2019). Articles surrounding the presence and impacts of plastic pollution on aquatic animals including fish species have become a regular occurrence on media platforms (Kramm et al. 2018) and scientific publications (Henderson & Green, 2020); however, while iconic pictures of individual fish and other taxa with variously attached or ingested plastics might make headlines, they do not of themselves prove impacts, absolute or relative, at population levels

Larval Transport Modeling of Deep-Sea Invertebrates Can Aid the Search for Undiscovered Populations

Background: Many deep-sea benthic animals occur in patchy distributions separated by thousands of kilometres, yet because deep-sea habitats are remote, little is known about their larval dispersal. Our novel method simulates dispersal by combining data from the Argo array of autonomous oceanographic probes, deep-sea ecological surveys, and comparative invertebrate physiology. The predicted particle tracks allow quantitative, testable predictions about the dispersal of benthic invertebrate larvae in the south-west Pacific. Principal Findings: In a test case presented here, using non-feeding, non-swimming (lecithotrophic trochophore) larvae of polyplacophoran molluscs (chitons), we show that the likely dispersal pathways in a single generation are significantly shorter than the distances between the three known population centres in our study region. The large-scale density of chiton populations throughout our study region is potentially much greater than present survey data suggest, with intermediate 'stepping stone' populations yet to be discovered. Conclusions/Significance: We present a new method that is broadly applicable to studies of the dispersal of deep-sea organisms. This test case demonstrates the power and potential applications of our new method, in generating quantitative, testable hypotheses at multiple levels to solve the mismatch between observed and expected distributions: probabilistic predictions of locations of intermediate populations, potential alternative dispersal mechanisms, and expected population genetic structure. The global Argo data have never previously been used to address benthic biology, and our method can be applied to any non-swimming larvae of the deep-sea, giving information upon dispersal corridors and population densities in habitats that remain intrinsically difficult to assess.Irish Research Council for Science, Engineering and TechnologyScience Foundation Irelan

High Abundances of Microplastic Pollution in Deep-Sea Sediments: Evidence from Antarctica and the Southern Ocean.

Plastic pollution in Antarctica and the Southern Ocean has been recorded in scientific literature since the 1980s; however, the presence of microplastic particles (<5 mm) is less understood. Here, we aimed to determine whether microplastic accumulation would vary among Antarctic and Southern Ocean regions through studying 30 deep-sea sediment cores. Additionally, we aimed to highlight whether microplastic accumulation was related to sample depth or the sediment characteristics within each core. Sediment cores were digested and separated using a high-density sodium polytungstate solution (SPT) and microplastic particles were identified using micro-Fourier-transform infrared spectroscopy (μFTIR). Microplastic pollution was found in 93% of the sediment cores (28/30). The mean (±SE) microplastics per gram of sediment was 1.30 ± 0.51, 1.09 ± 0.22, and 1.04 ± 0.39 MP/g, for the Antarctic Peninsula, South Sandwich Islands, and South Georgia, respectively. Microplastic fragment accumulation correlated significantly with the percentage of clay within cores, suggesting that microplastics have similar dispersion behavior to low density sediments. Although no difference in microplastic abundance was found among regions, the values were much higher in comparison to less remote ecosystems, suggesting that the Antarctic and Southern Ocean deep-sea accumulates higher numbers of microplastic pollution than previously expected

The Aquatic Symbiosis Genomics Project: probing the evolution of symbiosis across the Tree of Life

We present the Aquatic Symbiosis Genomics Project, a global collaboration to generate high quality genome sequences for a wide range of eukaryotes and their microbial symbionts. Launched under the Symbiosis in Aquatic Systems Initiative of the Gordon and Betty Moore Foundation, the ASG Project brings together researchers from across the globe who hope to use these reference genomes to augment and extend their analyses of the dynamics, mechanisms and environmental importance of symbioses. Applying large-scale, high-throughput sequencing and assembly technologies, the ASG collaboration will assemble and annotate the genomes of 500 symbiotic organisms – both the “hosts” and the microbial symbionts with which they associate. These data will be released openly to benefit all who work on symbioses, from conservation geneticists to those interested in the origin of the eukaryotic cell. The Aquatic Symbiosis Genomics Project is a worldwide effort to find the genome sequences of a variety of organisms and their microbial partners living in water. Supported by the Gordon and Betty Moore Foundation, this project involves scientists from around the world. The genome sequences will help scientists to better understand how these organisms interact with each other and their environment. The project will use advanced technology to map out the genes of 500 pairs of host organisms and their microbial symbionts. This information will be freely available, helping everyone from researchers studying species conservation to those exploring the beginnings of complex cell life

Breakdown of phylogenetic signal: a survey of microsatellite densities in 454 shotgun sequences from 154 non model Eukaryote species

Microsatellites are ubiquitous in Eukaryotic genomes. A more complete understanding of their origin and spread can be gained from a comparison of their distribution within a phylogenetic context. Although information for model species is accumulating rapidly, it is insufficient due to a lack of species depth, thus intragroup variation is necessarily ignored. As such, apparent differences between groups may be overinflated and generalizations cannot be inferred until an analysis of the variation that exists within groups has been conducted. In this study, we examined microsatellite coverage and motif patterns from 454 shotgun sequences of 154 Eukaryote species from eight distantly related phyla (Cnidaria, Arthropoda, Onychophora, Bryozoa, Mollusca, Echinodermata, Chordata and Streptophyta) to test if a consistent phylogenetic pattern emerges from the microsatellite composition of these species. It is clear from our results that data from model species provide incomplete information regarding the existing microsatellite variability within the Eukaryotes. A very strong heterogeneity of microsatellite composition was found within most phyla, classes and even orders. Autocorrelation analyses indicated that while microsatellite contents of species within clades more recent than 200 Mya tend to be similar, the autocorrelation breaks down and becomes negative or non-significant with increasing divergence time. Therefore, the age of the taxon seems to be a primary factor in degrading the phylogenetic pattern present among related groups. The most recent classes or orders of Chordates still retain the pattern of their common ancestor. However, within older groups, such as classes of Arthropods, the phylogenetic pattern has been scrambled by the long independent evolution of the lineages.Emese Meglécz, Gabriel Nève, Ed Biffin and Michael G. Gardne

Do chitons have a brain? New evidence for diversity and complexity in the polyplacophoran central nervous system

Molluscs demonstrate an astonishing degree of morphological diversity, and the relationships among molluscan clades have been debated for more than a century. Molluscan nervous systems range from simple 'ladder-like' arrangements of nerve cords to the complex brains of cephalopods. Chitons (Polyplacophora) are assumed to retain many molluscan plesiomorphies, lacking neural condensation and ganglionic structure, and therefore a brain. We reconstructed three-dimensional anatomical models of the nervous system in eight species of chitons in an attempt to clarify chiton neuroarchitecture and its variability. The specimen material incorporated both new data and digitised historic slide material originally used in the work of malacologist Johannes Thiele (1860-1935). Reconstructions of whole nervous systems in Acanthochitona fascicularis, Callochiton septemvalvis, Chiton olivaceus, Hemiarthrum setulosum, Lepidochitona cinerea, Lepidopleurus cajetanus, and Leptochiton asellus, and the anterior nervous system of Schizoplax brandtii, demonstrated a consistent and substantial anterior concentration of nervous tissue in the circumoesophageal nerve ring. This neural mass is further organised into three concentric tracts, corresponding to the paired lateral, ventral, and (putatively) cerebral nerve cords. These represent homologues to the three main pairs of ganglia found in other molluscs. The relative size, shape and organisation of these components is highly variable among the examined taxa, but consistent with previous studies of select species, and we formulated a set of neuroanatomical characters for chitons. These characters are parsimony-informative for reconstructing chiton phylogeny at the ordinal and subordinal levels; the identification of robust detailed homologies in neural architecture will be central to future comparisons among all molluscs, and more broadly in Lophotrochozoa. Modern evolutionary thinking, and modern tomographic technology, bring new light to an old problem. Contrary to almost all previous descriptions, the size and structure of the chiton anterior nerve ring unambiguously qualify it as a true brain with cordal substructure

Mollusca: Caudofoveata, Monoplacophora, Polyplacophora, Scaphopoda, And Solenogastres

Molluscs are the second most speciose metazoan phylum, and arguably molluscs demonstrate the largest morphological disparity. The dramatic body-plan modifications and changes among the molluscan clades leave few consistent characters that can be directly compared across all eight living classes. The five groups covered here—Caudofoveata (chaetoderms), Monoplacophora (headless deep-sea limpets), Polyplacophora (chitons), Scaphopoda (tusk shells), and Solenogastres (neomeniomorphs)—are all exclusively marine, and live as benthic or infaunal species. They are less commercially exploited than the other more speciose and edible groups of molluscs, but nonetheless demonstrate extensive diversification within each clade, and many are locally abundant and exert significant ecosystem control. They also possess fascinating specialized sensory structures, from the sensory shell ‘eyes’ or aesthetes within the shells of chitons, to the inordinate elastic sensory tentacles that scaphopods use for feeding. Neuroanatomy has long been crucial to the study of molluscs and molluscan phylogeny. Indeed, aplacophorans (Caudofoveata and Solenogastres) as well as scaphopods were historically considered to be worms, but the organization of their nervous systems helped early comparative anatomists to recognize these animals as molluscs. This assessment of the nervous systems across diverse body plans may prove essential to resolving larger questions about molluscan and metazoan evolutionary dynamics