Life Histories in an Epifaunal Community: Coupling of Adult and Larval Processes

Marine invertebrates growing epifaunally on red mangrove (Rhizophora mangle) prop roots in the Indian River, Florida, USA, were studied in a small mangrove island (Jim Island) through which a number of channels had been cut. Roots hanging down into the water supported diverse epifaunal communities including sponges, oysters, barnacles, bryozoans, and ascidians. To determine what factors control species\u27 population dynamics and contribute to the high degree of spatial heterogeneity characteristic of communities in this unique habitat, two hypotheses were tested: (1) Distributions of species on the roots are controlled by differential growth and mortality due to physical features; and (2) Recruitment, as influenced by larval supply, structures the community. Four channels of the island were chosen for comparison and experimentation. Distributions and abundances of epifauna in the channels were determined and physical parameters (i.e., temperature, pH, salinity, flow, turbidity) were measured over a 13-mo period. Adult and early juvenile organisms were transplanted among channels and growth and survival were monitored. Patterns of water flow in the island were studied, and plankton samples were taken to determine how larval supply varied among channels in different parts of the island. General patterns of recruitment were measured for 9 mo and patterns were compared to adult distributions. Epifaunal cover differed among the study channels, with dramatic differences in abundance and species diversity. Except for flow, physical factors did not differ significantly among channels. Flow rate, per se, was not responsible for disjunct distributions since neither adult nor juvenile survival (processes expected to be most affected by flow) differed among channels. Plankton samples and recruitment measurements revealed that the importance of larval supply depended on the life history of the individual species. Those producing short-lived lecithotrophic larvae showed patchy distributions that were strongly affected by the location of source populations and prevailing patterns of water flow. Species with long-lived planktotrophic larvae were more evenly distributed and post-settlement processes played a more important role in their population dynamics. On large temporal or spatial scales, the effects of physical factors on juvenile and adult organisms are probably quite important in controlling epifaunal distributions. However, in this study, the distributions of organisms on Rhizophora mangle root within Jim Island were best explained by differential larval input, with larval life history determining the strength of coupling between adult populations, larval supply, and patterns of recruitment

Adolescent Development Determines the Effects of Agonistic Social Stress on Rat Behavior and Locus Coeruleus Physiology

Stress is a causal factor in the development of many psychological disorders such as depression, anxiety, drug addiction, and conduct disorder. The degree to which stress affects the development of these disorders depends on several factors including the nature of the stressor, it’s timing with respect to critical periods in brain development, and genetic predispositions towards resilience or vulnerability. Adolescence is a period of development during which stress can have an enduring impact on behavior and susceptibility for affective disorders. The experiments in this thesis used the rat resident-intruder stress to model the interaction between adolescent development and the consequences of social stress on behavior and brain physiology. Rats representing 3 stages of adolescent development, early adolescent (EA, p28-p35), Mid-adolescent (MA, p42-p49) and adult (p63-p70), were placed in the cages of aggressive Long-Evans retired breeder rats daily for 7 days and tested in behavioral models of affective disorders 24-72h later. In EA rats selectively, social stress increased active coping behaviors in the defensive burying and forced swim tests. Because the locus coeruleus (LC)-norepinephrine system has been implicated in these active behaviors, LC neuronal activity was also quantified. Socially stressed EA rats had elevated LC spontaneous discharge rates and diminished phasic responses to sensory stimuli compared to controls, similar to the effects produced by the stress-related neuropeptide, corticotropin-releasing factor (CRF). Moreover, microinjection of a CRF antagonist into the LC selectively inhibited neurons of stressed EA rats, suggesting that exposure to social stress during early adolescence induces tonic CRF release onto LC neurons, shifting the mode of discharge to a high tonic state that may promote active coping. Interestingly, opposing behavioral and neuronal consequences were seen in adults as well as in EA rats exposed to social stress but tested in adulthood. Taken together, these results demonstrate that social stress interacts with adolescent development to alter coping strategies to novel challenges, with both immediate and long-lasting effects. The data also reinforce the fact that adolescence is physiologically and behaviorally distinct from adulthood and that treatments for stress-induced psychopathologies should reflect those differences

Variability in broods of the seastar \u3ci\u3eLeptasterias aequalis\u3c/i\u3e

Enormous variation exists in the reproductive output of marine invertebrates (e.g., in the numbers of em¬bryos produced, the volumes of embryos, and the energy that they contain). It is not clear why there is such great variability or what the population-level consequences are. We sampled a population of the brooding seastar Leptasterias aequalis (Stimpson, 1862) to collect basic information on brood sizes, embryo volume, and embryo energy content with a goal to better understand the reproductive ecology of this species. We collected brooding females in February and again in April. We measured the size of their broods and sampled the broods to estimate volume and energy con¬tent of the embryos. There was great variability in the volume and energy content of embryos produced by individual females and among the embryos in a single female\u27s brood. Larger adults produced larger embryos, which generally had greater energy content and may be of a higher quality. The average energy content of embryos appeared to in¬crease during the brooding period. Larger females produced larger broods but lost a greater proportion of the embryos. The net result is that larger individuals may not produce any more juveniles than smaller individuals, but those that they do produce may be of a higher quality. Originally published in Canadian Journal of Zoologyand used with permission

Structural-acoustic design and control of an integrally actuated composite panel

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1998.Includes bibliographical references (p. 165-170).The need for structural based acoustic control is evident in aircraft, aerospace, and naval systems. A promising approach utilizes active materials to intelligently control the dynamic response of light-weight, modally dense structures suppressing the radiated acoustic power. The basic representative structural element of a single panel offers an analytically tractable basis for examining various control methodologies for mitigating the acoustic response. An electro-mechanical Rayleigh-Ritz structural model is combined with an expression of the acoustic power radiated from a rectangular panel to yield a fully coupled structural-acoustic model. The insight afforded by this model is used to design the sensor and actuator architecture of the active structure for optimal closed-loop acoustic performance. The manufacturing of a composite panel with eight embedded active fiber composite (AFC) actuators and collocated strain sensors is presented in detail. The geometry of the test article is designed to represent the dynamics of the target applications, and the active elements are embedded in the composite panel to demonstrate the capabilities of the technology. Active control methods are explored through simulations and experiments to compare the applicability to active structural-acoustic control (ASAC). To quantify the comparison, designs based on classical low-authority feedback, optimal feedback, and x-filtered LMS feedforward techniques are presented. The results lend insight into the inherent limitations and advantages of each approach to the problem of broadband control. The investigation is application motivated in that the sensing and piezoelectric actuation occur solely at the structure while the performance is measured in the acoustic field. The conclusions consider the analytically predicted performance along with the corresponding experimental achievement to develop an understanding of the key issues necessary to apply the technology to the active structural-acoustic control of complex systems.by Brian S. Bingham.S.M

Precision autonomous underwater navigation

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003.Includes bibliographical references (p. 175-185).Deep-sea archaeology, an emerging application of autonomous underwater vehicle (AUV) technology, requires precise navigation and guidance. As science requirements and engineering capabilities converge, navigating in the sensor-limited ocean remains a fundamental challenge. Despite the logistical cost, the standards of archaeological survey necessitate using fixed acoustic transponders - an instrumented navigation environment. This thesis focuses on the problems particular to operating precisely within such an environment by developing a design method and a navigation algorithm. Responsible documentation, through remote sensing images, distinguishes archaeology from salvage, and fine-resolution imaging demands precision navigation. This thesis presents a design process for making component and algorithm level tradeoffs to achieve system-level performance satisfying the archaeological standard. A specification connects the functional requirements of archaeological survey with the design parameters of precision navigation. Tools based on estimation fundamentals - the Cram6r-Rao lower bound and the extended Kalman filter - predict the system-level precision of candidate designs. Non-dimensional performance metrics generalize the analysis results. Analyzing a variety of factors and levels articulates the key tradeoffs: sensor selection, acoustic beacon configuration, algorithm selection, etc. The abstract analysis is made concrete by designing a survey and navigation system for an expedition to image the USS Monitor. Hypothesis grid (Hgrid) is both a representation of the sensed environment and an algorithm for building the representation. Range observations measuring the line-of-sight distance between two acoustic transducers are subject to multipath errors and spurious returns.The quality of this measurement is dependent on the location of the estimator. Hgrids characterize the measurement quality by generating a priori association probabilities - the belief that subsequent measurements will correspond to the direct-path, a multipath, or an outlier - as a function of the estimated location. The algorithm has three main components: the mixed-density sensor model using Gaussian and uniform probability distributions, the measurement classification and multipath model identification using expectation-maximization (EM), and the grid-based spatial representation. Application to data from an autonomous benthic explorer (ABE) dive illustrates the algorithm and shows the feasibility of the approach.by Brian Steven Bingham.Ph.D

A Robotics Engineering Certificate for Students Across the Navy

The article of record may be found at https://www.onr.navy.mil/-/media/Files/ONR-Publications/Future-Force-22-Vol-6-No-4-2020.ashx?la=e

Seasonal Stability of a Flexible Algal-Cnidarian Symbiosis in a Highly Variable Temperate Environment

We evaluated the seasonal stability of two algal symbiont populations in the temperate intertidal sea anemone Anthopleura elegantissima on San Juan Island, Washington, where the relatively thermally tolerant dinoflagellate Symbiodinium muscatinei coexists with the less thermally tolerant chlorophyte Elliptochloris marina. Random collection of anemones along repeatedly sampled transects over four seasons and three shore heights revealed S. muscatinei to be the dominant symbiont, with E. marina mostly limited to anemones in the lower intertidal zone. At the lowest shore height sampled (+0.2 m), the proportion of E. marina was between 40% and 50% of the total symbiont population throughout the year. Symbiont distribution patterns persisted despite considerable seasonal variation in aerial exposure, temperature, irradiance, nutrients, and phytoplankton concentration, as well as a high potential for symbiont shuffling, with mixed-symbiont assemblages occurring in 51% of all anemones sampled. Symbiont density in anemones also changed little despite three- to fourfold-higher division frequencies of both symbionts during July and November. Although the intertidal zonation of these symbionts was stable over an annual period, we predict that their spatial distributions will be responsive to longer-term environmental change, and anticipate that this anemone symbiosis will be a useful and highly tractable barometer for future climate change, with this study serving as a baseline

The Earliest Farmers of Northwest China Exploited Grain-fed Pheasants not Chickens

Though chickens (Gallus gallus domesticus) are globally ubiquitous today, the timing, location, and manner of their domestication is contentious. Until recently, archaeologists placed the origin of the domestic chicken in northern China, perhaps as early as 8,000 years ago. Such evidence however complicates our understanding of how the chicken was domesticated because its wild progenitor – the red jungle fowl (Gallus gallus) – lives in tropical ecosystems and does not exist in northern China today or in the recent past. Increasingly, multiple lines of evidence suggest that many of the archaeological bird remains underlying this northern origins hypothesis have been misidentified. Here we analyze the mitochondrial DNA of some of the earliest purported chickens from the Dadiwan site in northern China and conclude that they are pheasants (Phasianus colchicus). Curiously, stable isotope values from the same birds reveal that their diet was heavy in agricultural products (namely millet), meaning that they lived adjacent to or among some of the earliest farming communities in East Asia. We suggest that the exploitation of these baited birds was an important adaptation for early farmers in China’s arid north, and that management practices like these likely played a role in the domestication of animals – including the chicken – in similar contexts throughout the region.The original isotopic analyses of these remains were conducted in collaboration with Seth Newsome (then at the Carnegie Institution of Washington) and Chen Fahu (Lanzhou University), with funding from the Wenner-Gren Foundation (awarded to L.B.). The University of Oklahoma provided funding for all molecular analyses (through B.M.K.). Open Access fees paid for in whole or in part by the University of Oklahoma LibrariesYe

Epibiotic Sponges on the Scallops Chlamys Hastata and Chlamys Rubida: Increased Survival in a High-Sediment Environment

The small free-swimming scallops, Chlamys hastata and Chlamys rubida, are frequently encrusted by the sponges Mycale adhaerens and Myxilla incrustans. It is unclear why this association exists. We hypothesized that living on scallop valves increases sponge survival by reducing the effects of sediment accumulation. Scallops were collected to measure correlations between sediment load and encrusting sponge mass. In the laboratory, the survival of sponges on living scallops and empty scallop valves was measured. Time-lapse video was used to quantify spontaneous swimming and clapping of C. hastata. In the field, both scallop size and sponge mass were significantly greater in high turbidity sites. In the laboratory, sponges on empty scallop valves experienced near complete mortality after five weeks. Manually clearing sediments increased survival but did not duplicate the high survival of sponges on living scallops, which regularly swam or clapped their valves