Food availability drives plastic self-repair response in a basal metazoan- case study on the ctenophore Mnemiopsis leidyi A. Agassiz 1865

Many marine invertebrates including ctenophores are capable of extensive body regeneration when injured. However, as for the invasive ctenophore Mnemiopsis leidyi, there is a constant subportion of individuals not undergoing whole body regeneration but forming functionally stable half-animals instead. Yet, the driving factors of this phenomenon have not been addressed so far. This study sheds new light on how differences in food availability affect self-repair choice and regeneration success in cydippid larvae of M. leidyi. As expected, high food availability favored whole-body regeneration. However, under low food conditions half-animals became the preferential self-repair mode. Remarkably, both regenerating and half-animals showed very similar survival chances under respective food quantities. As a consequence of impaired food uptake after injury, degeneration of the digestive system would often occur indicating limited energy storage capacities. Taken together, this indicates that half-animals may represent an alternative energy-saving trajectory which implies self-repair plasticity as an adaptive trade-off between high regeneration costs and low energy storage capacities. We conclude that self-repair plasticity could lead to higher population fitness of ctenophores under adverse conditions such as in ships’ ballast water tanks which is postulated to be the major vector source for the species’ spreading around the globe

Growth, Injury, and Population Dynamics in the Extant Cyrtocrinid Holopus mikihe (Crinoidea, Echinodermata) near Roatan, Honduras

The crinoid order Cyrtocrinida is known mainly from Mesozoic fossils; its few surviving members, all from bathyal environments, are among the most peculiar living crinoids. Cyrtocrinids attributed to Holopus mikihe Donovan and Pawson, 2008, have been observed in large numbers via submersible off the western coast of Roatán, Honduras, on vertical and overhanging walls at depths between 430 and 640 m. Observations in 2012, 2013, and 2014 have permitted the first estimates of population structure, growth, and regeneration. Two size modes were observed; the flat barnacle-like “juvenile” stage resembles confamilial and co-occurring Cyathidium pourtalesiAméziane, 1999, whereas the larger “adults” elevate the crown on a stumplike calyx. The 99th percentile growth rate was 0.19 cm yr–1, giving a minimum predicted age of 16 yrs for the largest specimen and 8.7 yrs for the median specimen; the median growth rate was 0.04 cm yr–1, corresponding to 72 and 39 yrs. However, the slower rate of growth in juvenile compared to adult specimens means that these ages are underestimates; actual median age may be closer to 50 yrs. Arm regeneration rate is estimated at 0.6 cm yr–1, and 9.8% of adult individuals were visibly injured, giving an interval of about 1.4 yrs between arm loss events. No recruitment or mortality was observed, and aggregations of evenly-sized individuals were prevalent, consistent with sporadic local recruitment and mortality

Science-based restoration monitoring of coastal habitats, Volume Two: Tools for monitoring coastal habitats

Healthy coastal habitats are not only important ecologically; they also support healthy coastal communities and improve the quality of people’s lives. Despite their many benefits and values, coastal habitats have been systematically modified, degraded, and destroyed throughout the United States and its protectorates beginning with European colonization in the 1600’s (Dahl 1990). As a result, many coastal habitats around the United States are in desperate need of restoration. The monitoring of restoration projects, the focus of this document, is necessary to ensure that restoration efforts are successful, to further the science, and to increase the efficiency of future restoration efforts

Marine Evidence-based Sensitivity Assessment (MarESA) – A Guide

The Marine Evidence-based Sensitivity Assessment (MarESA) methodology was developed by the Marine Life Information Network (MarLIN) team at the Marine Biological Association of the UK. The following guide details the approach, its assumptions, and its application to sensitivity assessment. The guide discusses: • key terms used in sensitivity assessment; • the definitions and terms used in the MarESA approach; • its assumptions; • the definition of resistance, resilience and sensitivity; • the definition of pressures and their benchmarks; • the step by step process by which the possible sensitivity of each feature (habitat, biotope or species) to each pressure is assessed; • the interpretation and application of evidence to sensitivity assessments on a pressure by pressure basis; and • limitations in the application of sensitivity assessments in management. The MarESA methodology provides a systematic process to compile and assess the best available scientific evidence to determine each sensitivity assessment. The evidence used is documented throughout the process to provide an audit trail to explain each sensitivity assessment. Unlike other expert-based approaches, this means that the MarESA assessments can be repeated and updated. The resultant 'evidence base' is the ultimate source of information for the application of the sensitivity assessments to management and planning decisions. The MarESA dataset and MarLIN website represent the largest review of the potential effects of human activities and natural events on the marine and coastal habitats of the North East Atlantic yet undertaken

Ecology of Injury in Marine Sedimentary Habitats: Effects of Repeated Injury on Infaunal Condition and Sediment Bioturbation

The majority of the ocean floor is sedimentary, and marine sediments play a key role in the flux of nutrients and organic matter in the ocean. Via their feeding and other activities, organisms living in marine sediments influence benthic-pelagic coupling by processing and redistributing organic matter supplied from the water column and influencing the supply of nutrients. These activities also influence recruitment and competitive interactions. Thus, factors that impact infaunal activity can secondarily impact sediment biogeochemistry and benthic communities. Non-lethal loss of body tissue is a common event for marine infauna such as polychaetes, and numerous studies have investigated the immediate effects of injury on individuals and predicted indirect effects on ecological interactions in marine soft-sediment habitats. Accurate predictions of the effect injury has on marine infaunal communities require knowing the frequency at which infaunal organisms are injured, whether injured individuals can regenerate and the speed at which they do so. But comprehensive, accurate assessments of injury rates among soft-bodied infauna are difficult because current methods underestimate injury rates by counting only individuals that are visibly regenerating lost tissue. Past injury may be masked by rapid regeneration in some species.RESEARCH SUMMARY & INTELLECTUAL MERIT: This project will use a novel approach using a histological stain in conjunction with field surveys to answer several important ecological questions: How frequently are marine worms injured? How variable is the incidence of injury in space and time? Are there species differences in the frequency of injury? Surveys of infaunal injury will be repeated during the spring and summer months over three years at two sites in Maine. This project will also investigate the effect of repeated injury on infauna, an aspect of injury that has been largely ignored. Comprehensive measurements relating sediment activity, regeneration status and nutritional condition of infauna are rare. Laboratory experiments will compare the effect of repeated injury on survival, growth, fecundity, nutritional condition and sediment disturbance by different functional groups such as spionid polychaetes (shallow tube-dwelling interface deposit feeders with rapid regeneration rates), maldanid polychaetes (head-down tube-dwelling conveyor-belt feeders), and arenicolid polychaetes (head-down burrowers that subduct surface sediments to depth to feed). This project will then use the data gathered in the proposed experiments and surveys to create a more realistic model of the interacting effects injury has on infaunal populations, sediment bioturbation, recruitment, and predator populations. Effects of predation intensity on bioturbation and infaunal populations will be explored.BROADER IMPACTS: The project includes a significant effort to improve ocean science literacy across the nation by collaborating with the Centers for Ocean Sciences Education Excellence-Ocean Systems team (COSEE-OS) to develop educational resources describing the ways marine infauna link sediment and water column processes in the ocean. Two graduate students and three undergraduates will receive diverse training in marine organismal biology, physiology and ecology. All participants will work with COSEE-OS educational experts to develop content and educational activities that will be added to interactive concept maps of Oceans and Climate and Ocean Diversity. Undergraduate and graduate students will be introduced to the process of translating the knowledge and experience they gain during their research into larger key concepts to be presented to a general audience. Educational activities will be tested in the PI\u27s marine science class and interactive concept maps and ocean science educational activities will be widely distributed by COSEE-OS via the internet. Materials will align with Ocean Literacy Essential Principles and National Science Education Standards. After internal evaluation at the University of Maine to evaluate student learning, the materials will then be widely distributed by COSEE-OS and evaluated using standard evaluation protocols for technology usability and end-user effectiveness. By working directly with both a national network (COSEE) and a national ocean literacy campaign with proven success, we can ensure that our deliverables will reach a broad spectrum of learners, including those traditionally underrepresented in ocean sciences

The impact of deep-sea fisheries and implementation of the UNGA Resolutions 61/105 and 64/72. Report of an international scientific workshop

The scientific workshop to review fisheries management, held in Lisbon in May 2011, brought together 22 scientists and fisheries experts from around the world to consider the United Nations General Assembly (UNGA) resolutions on high seas bottom fisheries: what progress has been made and what the outstanding issues are. This report summarises the workshop conclusions, identifying examples of good practice and making recommendations in areas where it was agreed that the current management measures fall short of their target

Self-repairing symmetry in jellyfish through mechanically driven reorganization

What happens when an animal is injured and loses important structures? Some animals simply heal the wound, whereas others are able to regenerate lost parts. In this study, we report a previously unidentified strategy of self-repair, where moon jellyfish respond to injuries by reorganizing existing parts, and rebuilding essential body symmetry, without regenerating what is lost. Specifically, in response to arm amputation, the young jellyfish of Aurelia aurita rearrange their remaining arms, recenter their manubria, and rebuild their muscular networks, all completed within 12 hours to 4 days. We call this process symmetrization. We find that symmetrization is not driven by external cues, cell proliferation, cell death, and proceeded even when foreign arms were grafted on. Instead, we find that forces generated by the muscular network are essential. Inhibiting pulsation using muscle relaxants completely, and reversibly, blocked symmetrization. Furthermore, we observed that decreasing pulse frequency using muscle relaxants slowed symmetrization, whereas increasing pulse frequency by lowering the magnesium concentration in seawater accelerated symmetrization. A mathematical model that describes the compressive forces from the muscle contraction, within the context of the elastic response from the mesoglea and the ephyra geometry, can recapitulate the recovery of global symmetry. Thus, self-repair in Aurelia proceeds through the reorganization of existing parts, and is driven by forces generated by its own propulsion machinery. We find evidence for symmetrization across species of jellyfish (Chrysaora pacifica, Mastigias sp., and Cotylorhiza tuberculata)

Coelomic transport and clearance of durable foreign bodies by starfish (<i>Asterias rubens</i>)

Echinoderms have excellent healing and regeneration abilities, but little is known about how they deal with the related challenge of durable foreign bodies that become lodged within their bodies. Here we report a novel mechanism for foreign body elimination in starfish. When injected into the arm of a starfish, passive integrated transponder tags and magnets of similar dimensions are eliminated at a rate approximating 10% per day. These objects are forcefully ejected through the body wall at the distal tip of an arm. Ultrasound images reveal that foreign bodies are moved within the body cavity, and tracking of magnets injected into starfish suggests that the movements are haphazard rather than directed. Constrictions of the body wall near the foreign object are the likely mechanism for this transport process. Open questions include the ecological relevance of this behavior, why clearance occurs through the distal tips of the arms, the neurological and muscular control of this behavior, what other animals use this mechanism, and the range of objects starfish can eliminate in this way.</p