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The annual Postdoctoral Symposium will be hosted on Tuesday March 11th, 2025, in the Speck Auditorium, followed by a poster session in Swope Center. Everyone is welcome to attend! And all postdocs, graduate students, research assistants, and post-bacs are welcome to present their research. This is a great opportunity to share your research with the whole MBLcommunity and a friendly audience.

Meals and coffee breaks will be provided for all registered attendees - registration is now closed.

Organizing committee: Beverly Naigles, Emeline Vidal, Nicole Dames, and Nancy Yang

Click here for full schedule.

Long Talk Sessions

Session 1

9:15 - 9:30 Deciphering high-level A-to-I RNA recoding in the cephalopod brain
Presenter: Gjenni Voss

9:35 - 9:50 Single cell transcriptomics reveals the pre-chordate origins of conserved ovarian cell types and regulatory systems
Presenter: Periklis Paganos

9:55 - 10:10 Morphogenetic, cellular, and molecular characterization of neural development in squid
Presenter: Jess Stock

The foundation of complex brain function is laid during embryonic development. Much of our understanding of neurodevelopmental processes is derived from studies in vertebrates and a few relatively simple model invertebrates. However, massive brains have evolved twice: in vertebrates and the coleoid cephalopods (including squid and octopus). Indeed, cephalopods present a unique model system to investigate the development of a complex nervous system outside of the vertebrate lineage. The coleoid brain rivals that of vertebrates in size and complexity and is by far the most elaborate among invertebrates. While cephalopods have been a prominent model system to investigate the anatomical attributes of the adult nervous system, its embryonic origins have yet to be understood. Recent progress in tool development has now made it possible to dive into cephalopod embryogenesis and dissect the nervous system development, not only anatomically, but also on a molecular level. Comparisons between the convergently evolved brains found in vertebrates and coleoid cephalopods has the potential to reveal fundamental principles underlying the development and evolution of complex nervous systems, as well as novel mechanisms unique to both clades. Harnessing a combination of in situ hybridization chain reaction, diverse imaging approaches, RNA sequencing and Crispr-mediated gene manipulation, we provide a description of nervous system development in the squid, Doryteuthis pealeii. Starting with the establishment of the neurectodermal domain and culminating in the birth of mature neurons, we shed light onto the spatial, temporal, and morphogenetic organization of the developing squid nervous system. By identifying conserved and novel regulators we can dissect networks driving cephalopod neurogenesis and provide insights into developmental mechanisms that build the squid nervous system.

10:15 - 10:30 How to build an ovarian follicle – lessons from the sea star
Presenter: Beverly Naigles

Session 2

10:45 -11:00 Iron and sulfur dynamics in coastal marshes
Presenter: Zhaoxun (Nancy) Yang

Coastal marsh ecosystems are highly productive, contribute to carbon sinks and useful against shoreline erosion. However, fluctuating environmental conditions could influence the carbon storage capacity of these marshes. Tidal oscillations and plant activities affect the water movement in the coastal marshes, leading to changes in the redox dynamics associated with carbon, iron, and sulfur. Some processes of iron and sulfur dynamics remain cryptic and in need of investigations, particularly in a rapidly oscillating environment with many hydro-biogeochemical variables. With long-term established coastal marshes surrounding Plum Island Sound in northeastern Massachusetts, we hope to understand how iron and sulfur influence the soil redox status over different time scales and the roles of iron and sulfur cycles in microbial carbon mineralization and carbon fixation within sediments. Our proposed approaches include quantifications of short-term turnovers of iron and sulfur over a diel cycle as well as bulk monthly and yearly changes. With porewater measurements at two distinct locations, we found that marsh interiors had different depth patterns of reduced iron and sulfide from those of creek banks. Ongoing work with diffusive gradient/equilibrium thin films as visualizations for reduced iron and sulfide concentration gradients aim to identify the “hot spots” of these species in marsh sediments. Eventually, our work provides information for a larger project effort in a mechanistic understanding of how a coastal marsh ecosystem function in an oscillating environment. 

11:00 - 11:15 Saltwater intrusion alters soil porewater biogeochemistry along an Arctic coastline 
Presenter: Elizabeth (Liz) Elmstrom

Saltwater intrusion occurs along coastlines worldwide, driving changes in ionic strength, redox conditions, and biogeochemistry in coastal soils. These changes can elevate certain chemical species in porewaters, altering the land-to-sea flux of critical materials, such as nutrients and carbon, through subsurface flows. Along the Arctic coastline, tundra soils experience periodic saltwater inundation; however, compared to lower latitude environments, the influence of salinization on porewater biogeochemistry remains far less explored. Furthermore, sea level rise and increasing wave action due to sea ice loss are accelerating the frequency of saltwater inundation and salinization of tundra soils. In this emerging cross-institutional study, we seek to understand how salinization impacts the physical and biogeochemical properties of coastal tundra, including changes in porewater nutrient and carbon concentrations and their advective fluxes. Here, we present preliminary results from our first field campaign, including measurements of porewater ammonium (NH4+) concentrations taken along salinity gradients in tundra soils along Alaska’s Beaufort Sea coast. Our findings reveal that salinization noticeably alters porewater nutrient composition, with net NH4+ generation observed in salinized soils. Patterns in sulfate (SO4-2) concentrations and oxidation-reduction potential (ORP) further suggest that SO4-2 reduction may be a key driver of NH4+ generation in salinized tundra soils. Ion exchange and physical processes may also contribute to observed patterns in NH4+ concentrations. These results demonstrate the influence of salinization on tundra soil biogeochemistry, while also highlighting the potential role of saltwater intrusion in shaping redox-driven transformations and future nutrient availability along the Arctic coast.

11:20 - 11:35 Methanogen and methanotroph community transition zones between the interior and creek bank of a brackish tidal marsh
Presenter: Joe Vineis

Estuaries are hot spots for biogeochemical processes that transform materials from both terrestrial and aquatic sources. Plants inhabiting coastal estuaries are highly productive and a single plant species can blanket large swaths of the marsh platform. The plants maintain intimate relationships with the resident microbial community and the plant-microbial interplay of nutrients and carbon are central to the carbon storage, nutrient cycling and greenhouse gas fluxes. Although the plants maintain a uniform cover over the marsh, we hypothesized that the different hydrology and nutrient flux between the well-flushed creek bank and less-frequently flooded marsh interior platform, driven by the tidal cycle, should influence the composition of microbial communities. We characterized the microbial community along an interior to creek bank transect in Plum Island LTER, MA to identify shifts in composition and diversity, especially among microbes known to influence the flux of methane and other greenhouse gasses. We identified diverse methanogen communities of Methanothrix and Methanosarchina in the interior (suggesting diverse methanogenic pathways, including potentially methylotrophic methanogenesis), and more abundant oxidizing Nitrosarchaeum in the creek bank where tidal river flushes the sediment more often. Bacterial methanotrophs and ammonia oxidizers with distinct compositional changes were also common along the transect. Our results suggest the presence of a transition zone for microbial communities important to the cycling of methane and nitrogen in these sediments with potential feedback mechanisms on plant-microbial interactions, subsequent carbon storage, and nutrient cycling. 

11:40 - 11:55 Rhizosphere oxygen pool dynamics in Typha angustifolia
Presenter: Ilana Stein

Oxygen released by the roots of wetland plants (radial oxygen loss, or ROL) has important implications for soil biogeochemical cycling. Oxygen pool sizes reflect the balance of ROL and biological oxygen demand, and can be quantified in the lab using planar optodes. Oxygen enters leaves from the atmosphere when stomata are open as well as being generated during photosynthesis, and can diffuse or be moved advectively through aerenchyma tissue to the roots. However, much remains unknown about the spatial patterning, timing, and physiological mechanisms of ROL, and its degree of coordination with photosynthetic gas exchange.

In the lab, we imaged oxygen pools over time in the rhizosphere of Typha angustifolia rooted in live marsh sediment, using an oxygen-sensitive planar optode system. We simultaneously measured net photosynthesis and stomatal conductance over the course of several days, to determine the magnitude and timing of ROL in relation to root growth, day/night cycles, and leaf-level gas exchange. We tested 1) whether root growth occurs during daytime, at night, or both; 2) whether the oxygen pool varies with day/night cycles; and 3) if specific events such as root growth or photosynthetic activity are associated with larger pools of rhizosphere oxygen.

Root and rhizome growth as well as oxygen loss occur both during the day and throughout the night, and oxygen pools develop around newer tissues. Particularly notable was a large plume of oxygen that developed when multiple new lateral roots, located close together on the root axis, erupted through the cortex of a central root. We observed that the oxygen pool in the rhizosphere varies partially as a function of day/night cycles, but in contrast to some findings in the literature, the pattern of O2 release during day/night cycles was more complex than simply responding to stomatal and photosynthetic activity.

These findings highlight the importance of root and rhizome development, particularly lateral root production, on rhizosphere oxygenation, and demonstrate that localized oxygen pools can persist throughout the night despite stomatal closure and photosynthetic shutdown.

Session 3

1:15 - 1:30 Pronounced seasonality and distinct clades of Hikarchaeia in warm oceans 
Presenter: Nicole Dames

Little is known about the ecology, genomics and physiology of the Hikarchaeia, a family of Archaea assigned previously as Marine Group IV. Recent work has assigned the Hikarchaeia as being closely related to the Haloarchaea, however the diversity or ecology of these organisms is not as well described. Here, we explored the seasonality of Hikarchaeia at the Bermuda Time-series Study (BATS) through the analysis of 16S rRNA V4 gene amplicons collected across the vertical dimension on a monthly basis, spanning the years 2016 to 2021. At this seasonally stratified subtropical site, these archaea are typically present at <4% of relative abundance of total archaeal ASVs. Based on size fractionated data they appear to be solely free-living. Hikarchaeia are found predominantly between 80-300 m, and at these depths their relative abundances increase during the seasonal transition periods (Spring and Autumn) and peaked during the summer stratification period. Their consistent presence led to the recovery in metagenomic data, resulting in a high-quality, circularized, metagenomic assembled genome (MAG) of Hikarchaeia which has allowed for further investigation into the potential ecology and diversity of these organisms. Through phylogenomic reconstruction of an additional 17 new and known hikarchaeal MAGs, here we propose a separation of Hikarchaeia into seven distinct clades (Group I -VII) which show strong biogeographical or depth-related habitat associations. 

1:30 - 1:35 Plasticity of Invertebrate Cell Division in a Warming Ocean
Presenter: Jamie Mackinnon

1:35 - 1:50 3D feeding currents of the ctenophore Mnemiopsis leidyi
Presenter: Mitchell Ford

Lobate ctenophores such as Mnemiopsis leidyi are voracious predators of marine zooplankton. Mnemiopsis is native to the western Atlantic but has successfully invaded coastal waterways worldwide. Part of this success is likely due to their use of two distinct predatory modes, which allow them to consume small (a few hundred microns) slow-moving prey as well as larger prey capable of active escapes (including copepods and fish larvae). To capture small prey, these ctenophores generate feeding currents that draw prey to the tentillae, where they are immobilized for consumption. For larger prey that can escape from these feeding currents, Mnemiopsis employ a second predatory mode in which they close the oral lobes to physically trap prey. In this study we use 3D particle tracking velocimetry to measure the flow field of the water around Mnemiopsis both with and without large prey present. Based on the flow field data, we propose that current models, which predict maximum clearance rates for lobate ctenophores based on the swimming speed and oral lobe opening area, likely overpredict maximum predation rates on small prey, while providing a reasonable estimate for the maximum encounter rate with large prey. However, copepods are sometimes observed passing between the oral lobes without evoking either a capture response from the ctenophore or an escape response from the copepod. We have begun preliminary work to identify the hydrodynamic signals that elicit predation and escape responses from Mnemiopsis and some of their common prey items, which will also be presented.

1:50 - 1:55 VitelloTag: a tool for high throughput cargo delivery into oocytes and other ovarian cell types
Presenter: Akshay Kane

1:55 - 2:10 Maternal and grandmaternal age influences offspring lifespan, reproduction and gene expression on the marine rotifer Brachionus manjavacas
Presenter: Nelia Luviano Aparicio

Maternal age influences offspring lifespan, reproduction, and gene expression across generations in the rotifer Brachionus manjavacas. Offspring of older mothers and grandmothers have reduced lifespans, but an extended reproductive period compared to those of younger mothers and grandmothers. To uncover mechanisms driving maternal and grandmaternal effects, we compared the age-specific gene expression of offspring from old and young maternal lineages. Expression profiles cluster strongly by age, with further sub-clustering within each cohort based on maternal and grandmaternal age. Gene expression profiles of 1-day-old rotifers differ markedly from older age cohorts, reflecting significant early-life differences where maternal and grandmaternal age effects are most pronounced, gradually diminishing with age. In 1-day-old rotifers born to older mothers and grandmothers, upregulated genes are enriched in cell cycle regulation, cell proliferation, apoptosis, DNA replication, oocyte meiosis, digestion, and purine metabolism compared to offspring of younger mothers and grandmothers. Changes in pathways related to oocyte meiosis and digestion suggest that maternal age alters development and metabolism. These findings indicate a trade-off in the offspring of old mothers, where resources are allocated to early-life survival and reproduction at the expense of longevity. Additionally, we found increased expression of histone-modifying enzymes, including histone deacetylases (HDACs) and the histone methyltransferase SETDB1, with age and maternal age. Testing HDAC inhibitors β-hydroxybutyrate and sodium butyrate, and the SETDB1 inhibitor mithramycin A, revealed potential therapies for aging. Mithramycin A significantly extended lifespan and enhanced heat stress resistance, whereas β-hydroxybutyrate improved only lifespan, and sodium butyrate improved only heat stress resistance. Together, our results highlight transgenerational effects of aging, where maternal and grandmaternal age influence offspring lifespan, health, and early-life gene expression.

Poster Session and Flash-Talks

Flash-Talks Only

11:15 - 11:20 Zostera marina in vitro cultivation techniques as a novel approach to seagrass restoration 
Presenter: Sarah Merolla

Zostera marina is a species of seagrass that acts as a vital ecosystem engineer in coastal areas. Z. marina meadows in Cape Cod, Massachusetts are rapidly disappearing due to a reduction in water quality and rising temperatures in the area. Many restoration efforts have been attempted with low success rates, prompting the need for new restoration approaches. Our study evaluated Z. marina cultivation techniques through a series of experiments. The first experiment assessed optimal conditions for Z. marina seedling cultivation in vitro. We tested the effects of media composition (biphasic vs. liquid media) and aeration techniques (bubbling vs. shaking) over four weeks. Biomass accumulation was used as the primary indicator of seedling performance. A second experiment examined how cultivation environments (in vitro vs. natural conditions) and donor populations (seeds collected from different sites in southeastern MA) impact Z. marina seed germination and development. Seeds collected from 13 sites were cultivated in culture chambers under sterile conditions or in seawater aquaria for six weeks. Seed cultivation success was evaluated based on germination rates and seedling survivability. The third experiment focused on the acclimatization potential of in vitro-cultivated Z. marina seedlings, comparing their survival rates in sterile culture and non-sterile seawater aquaria after 8 weeks. Results from these studies will contribute to the optimization of Z. marina cultivation protocols and inform seagrass restoration strategies.

11:35 - 11:40 Developing callus induction methods for Zostera marina: a biotechnical approach to seagrass restoration
Presenter: Grace Dixon

Zostera marina is a flowering seagrass vital to fisheries and coastal ecosystems. Population assessments over the past four decades have documented significant declines attributed primarily to thermal stress and cultural eutrophication. Current restoration initiatives aim to re-establish seagrass beds through both transplantation and direct seed dispersal methods. Restoration success remains constrained by limited seed availability and variable recruitment rates. This study aims to develop protocols for callus induction and somatic embryogenesis in Z. marina to enable the production of somatic embryos from a single seed, thereby scaling up restoration efforts. Experimental protocols have been designed for wild explant sterilization, aseptic seedling culture, in-vitro germination and callus induction, with eventual transfer to studies on somatic embryogenesis. In comparison to other liquid media prepared for germination of seeds, rates in culture reached up to 85% with basal f/2 media. Seedlings grew up to three leaves with a maximum leaf height of 4.5 cm after 4 weeks in culture. Varying types and concentrations of growth hormones in agar media were used in callus induction trials, as well as axenic and wild explant tissue from seagrass. Preliminary results demonstrate potential callus development in root structures and immature seeds. These findings represent a crucial step towards large-scale propagation of Z. marina for ecosystem restoration purposes.

Posters Only

1) Adenosine Deamination and Protein Recoding in Cephalopods: Characterizing the Role of sqADAR1 in the Euprymna berryi
Presenter: Paula Diaz Sanchez

2) Sucker attachment and local recruitment patterns of Octopus bimaculoides
Presenter: Ashley Gendreau

Octopuses have a complex and partly decentralized nervous system, enabling precise neural control and coordination of their suckers. While evidence of sucker coordination suggests neural connection between individual suckers, the exact connections are unknown. To explore this, we developed a whole-live-animal behavioral protocol using Octopus bimaculoides that allowed us to film the suckers on individual arms as they interacted with agarose disks embedded with prey extract. Videos were used to identify sucker dynamics and recruitment patterns, granting insight into how sensory information may be transmitted between suckers. Results indicated three recruitment patterns occurred most frequently: 1) i-i-i-i-i, 2) i-i-i-i-c, 3) i-i-i-c-i. Ipsilateral recruitments occurred more often than contralateral recruitments, suggesting neuronal signals are sent in a straight line more often than crossing to suckers on the other side of the arm. Additionally, sucker recruitment on distal arm segments had a faster average attachment time than proximal recruitments implying that signals move faster in the distal direction than the proximal direction. Our results provide baseline behavioral evidence for the existence of neuronal connections between individual suckers and emphasize the need for further research to determine the nature of these connections.

3) Simulating particle export from the base of the mixed layer to the deep ocean
Presenter: Rachele Spezzano

4) High-resolution diel time series reveals viral-induced metabolic reprogramming of bacteria in a microbial mat
Presenter: Jaden Hansen

5) Non-Destructive Sampling of Sediment Microbial Community Structure and Function
Presenter: Quincy Dowling

Brackish-marsh environments are crucial to understanding global biogeochemical cycling, and yet key players in these cycles, microbial communities, are vastly understudied in their diversity, composition, and, particularly, their dynamics. Sampling of sediment microbial communities has generally been conducted via sediment coring, a highly destructive and labor-intensive process requiring a large volume extraction of sediment. We aimed to identify an alternative sampling method by which microbial composition and function could be rapidly and repeatedly assessed while greatly reducing the field labor and destruction required. Such an approach holds particular promise for pairing identity, function, and dynamics of major microbial groups with measurements of dynamic, ecosystem-scale processes. Here, we assessed a nylon-flocked swabbing method as an alternative to sediment coring. Two sediment columns were sampled via both nondestructive swabbing and traditional sediment coring. Samples were taken in 5-10cm increments starting from 5cm below the marsh surface down to 80 cm in a Typha angustifolia marsh at the Plum Island Ecosystems LTER north of Boston. Diverse microbial taxa were identified via 16S rRNA gene sequencing. Major groups detected by swabs were similar in identity and proportion to major groups detected by coring. Our results indicate that sediment swabbing is an effective method for assessing diversity and community composition major microbial groups, even at depth, in brackish marsh environments. Further exploration and adoption of this new method could enable researchers to capture dynamics in microbial structure and function in a convenient and accurate way without largescale disruption of the ecosystem.

6) Identifying major sources of terrigenous organic matter in south Florida seawater using dissolved lignin
Presenter: Chase A. Glatz

Understanding sources of organic matter in coastal ecosystems is crucial for assessing carbon cycling, ecosystem health, and impacts of terrestrial inputs on marine productivity. Lignin is an effective biomarker for terrigenous organic matter due to its primary land plant source and unique composition of phenolic subunits, which can reveal characteristics of its source such as plant type or degradation state. The main goal of this study was to examine dissolved lignin phenols from Biscayne Bay to the Florida Straits to determine whether they could distinguish surface water that receives largely local terrigenous input (Biscayne Bay) to surface water comprised of distal terrigenous material (Florida Straits). To accomplish this, a cupric oxide oxidation method was developed to in order to analyze by gas chromatography-mass spectrometry, using red mangrove leaves from South Florida as test samples. Phenol ratios obtained from this method correctly identified the red mangrove leaves as non-woody angiosperm tissue. The oxidation method was combined with solid phase extraction cartridges to collect and analyze dissolved lignin from seawater samples obtained from 5 m depth along 4 transects from Biscayne Bay to Florida Straits. Seawater samples ranged from 119 to 380 ng/L of total phenol concentrations, with a general decrease away from South Florida coastline. Vanillyl acid-to-aldehyde ratio, syringic acid concentration, and syringyl-to-vanillyl ratio increased with distance away from the coastline. These results were expected due to larger terrigenous input in local Biscayne Bay waters compared to distal waters of Florida Straits. The higher syringyl-to-vanillyl ratio in the Florida Strait could be explained by angiosperm association with smaller soil sizes that are easier to advect and solubilize farther from the initial continental source. Overall, this study shows that lignin phenols present a promising biomarker for determining the major sources of terrigenous organic matter from local or distal input.

7) Tracking Mixoplanktonic Grazing and Carbon Flow Using Natural Abundance Radiocarbon
Presenter: So Hyun (Sophia) Ahn

Many protistan plankton species are capable of both photosynthesis and phagocytosis and therefore have dual roles as primary producers and consumers. This trophic flexibility complicates biochemical fluxes and can potentially transfer more carbon and nutrients to upper trophic levels than currently accounted for. Advances over the last decade have greatly improved our understanding of protistan mixoplankton activities, but most studies have focused on identifying the organisms and conditions that lead to mixotrophic behavior. In contrast, fewer studies have quantified the impact on carbon and material flow through the aquatic food web. The goal of our study is to quantify the integrated contributions of autotrophy (photosynthesis) and heterotrophy (phagocytosis) during the mixoplanktonic growth and determine the impact on nutrient transfer to higher trophic levels. Our approach is to exploit the large dynamic range of natural abundance of radiocarbon (F¹⁴C) to track source contributions, in conjunction other existing method, flow cytometric quantification of grazing rates. The mixotrophic Ochromonas CCMP 1391 was grown under photosynthesis-favored conditions with a F¹⁴C-free inorganic carbon source. For grazing-favored treatment, bacterial prey was labeled with a modern F¹⁴C signature by providing organics. The F¹⁴C signature of the Ochromonas will be used to determine how much carbon is incorporated by phagocytosis pathways. Ultimately, photoautotrophically and mixoplanktonically grown Ochromonas sp. will be provided as prey to protozooplankton and the growth and ingestion rates of grazers will be calculated to determine the transfer of carbon up trophic levels.

Combined Posters and Flash-Talks

8) The relationship between a unique, intrinsically disordered domain of cephalopod ADAR1 and high-order mRNA recoding
Presenter: Noah Martin
Flash-talk in Session 1 (10:10 - 10:15)

9) VitelloTag: a tool for high throughput cargo delivery into oocytes and other ovarian cell types
Presenter: Akshay Kane
Flash talk in Session 3 (1:50 – 1:55)

Developmental and reproductive biology research broadly relies upon the delivery of molecular and genetic tools into oocytes to perform perturbations and study various biological processes. In diverse model organisms, including mouse, zebrafish, xenopus, and echinoderms, this is achieved through microinjection. Microinjection, while highly effective, has challenges in terms of cost of setup, the technical skill required, and the limited numbers of injected oocytes obtainable. It also proves challenging in organisms with delicate oocytes or restricted spawning seasons. To overcome these limitations, we have developed VitelloTag, a simple, cost effective, and high throughput method of delivery into oocytes, comparable in terms of technical difficulty to transfection. Vitellogenesis is a yolk-protein uptake pathway, highly conserved across many animal phyla. It involves the yolk protein precursor vitellogenin, which is recognized by vitellogenin receptors on the oocyte cell surface, triggering its endocytosis and ultimately resulting in the formation of yolk platelets in the developing oocyte. Here, we present a delivery system that employs conserved regions of vitellogenin, recombinantly fused with the protein of interest for delivery via receptor-mediated endocytosis and endosome escape. We demonstrate this tool’s utility and cross-taxa applicability by delivering GFP and Cas9/sgRNA complexes, with successful gene knockout phenotypes, in two distantly related species. We also show VitelloTag can deliver cargo to multiple cell types within the ovary and that it can be used to study the process of vitellogenesis in diverse species.

10) Understanding Body Axis Development Using the sea star Patiria miniata and the sea cucumber Leptosynapta tenuis
Presenter: Talia Marc
Flash-talk in Session 1 (9:30 – 9:35)

Establishing the major body axes during embryogenesis is necessary for the overall development of the body and the placement of organs. Failure in axis development causes incorrect organ morphology and impacts organ function. How do animals form their body axes? To tackle this question we investigate axes formation in a group of animals with the unique ability to make their body plans twice, the echinoderms. Echinoderms include sea urchins, sea stars, and sea cucumbers, animals that transition from a larval bilateral body plan to pentameral body plan for adult form. In the sea star, metamorphosis is initiated by the rudiment, a thick tissue located at the posterior region of the larva. During metamorphosis, sea star larvae are reabsorbed into the rudiment where the body is destroyed and reorganized to form the pentameral body plan. My primary project focuses on understanding how new organs are formed during metamorphosis of Patiria miniata. We hypothesize that sea stars require activation of transcription factors during metamorphosis in the rudiment which reorganizes the anterioposterior axis of the larvae to develop their pentametal body plan. Using differential RNAseq (deRNAseq) of anterior versus posterior on Patiria miniata larvae, we identified critical genes enriched in the rudiment, such as Hox genes. Using Hybridized Chain Reaction (HCR), we examined Hox gene expressions during development. We discovered the expression of Hox genes in a group of mesenchymal cells, migratory cells with multiple roles. We think that this means stem cells contribute to the development of the new body plan. Additionally, I work to develop protocols to establish Leptosynpata tenuis, the local sea cucumber, as a model system at the MBLto understand mechanisms behind body axis development and skin regeneration. Unlike the sea stars, sea cucumber's metamorphosis does not rely on a rudiment, and their pentameral symmetry is distinct because it is the only echinoderm that shows both bilateral and pentameral features. Using echinoderms to understand biological questions in developmental biology can provide further insight into the mechanism of body patterning, organogenesis, and regeneration. 

11) Impacts of O-GlcNAcylation of α-Synuclein on Synaptic Vesicle Docking and Trafficking at a Vertebrate Synapse 
Presenter: Jaqulin N. Wallace
Flash-talk in Session 1 (9:50 – 9:55)

α-Synuclein is a pre-synaptic vesicle-associated protein that modulates synaptic vesicle (SV) trafficking and clustering. In several neurodegenerative diseases, including Parkinson’s disease, α-synuclein aberrantly aggregates at synapses. Modeling this, we previously showed that acutely increasing excess wild type (WT) α-synuclein to levels observed in disease states induced a severe, activity-dependent inhibition of endocytosis. Many post-translational modifications of α-synuclein have been identified, however, little is known about how these modifications may impact its synaptic functions. In this study, we began to explore the impact of glycosylation, specifically O-GlcNAcylation of α-synuclein at serine 87 (gS87). We acutely delivered precise amounts of chemically synthesized, recombinant gS87 α-synuclein (10-20 µM) into the reticulospinal (RS) axons of sea lamprey (Petromyzon marinus), a vertebrate with particularly large RS synapses (1-2 µm) that are amenable to detailed ultrastructural analyses by light and electron microscopy. We report here that gS87 α-synuclein robustly localized to synapses, as shown by colocalization with the synaptic vesicle marker, SV2, using the novel stage-scanning line confocal. In the absence of stimulation, gS87 caused no appreciable changes to synapses at the ultrastructural level. In contrast, stimulated synapses (20 Hz, 5 min) treated with gS87 showed a severe inhibition of SV trafficking, similar to WT α-synuclein, including a significant 50% loss of SVs and compensatory 3-fold increase in both cisterna (putative endosomes) and clathrin coated intermediates. Interestingly, unlike WT α-synuclein, gS87 induced a drastic 70% reduction in the number of docked SVs present, which predicts an inhibition of neurotransmitter release. This work demonstrates the dramatic impacts that single post-translational modifications have on α-synuclein function and dysfunction at the pre-synapse. 

12) Plasticity of Invertebrate Cell Division in a Warming Ocean
Presenter: Jamie Mackinnon
Flash-talk in Session 1 (1:30 – 1:35)

Sea surface temperatures are forecasted to rise 1-4°C across the next century. It has been shown that ocean warming has devastating impacts on adult marine organisms, which raises another ecological question: will marine embryos be able to adapt? We explore this using sea stars to define the thermal resilience of early cellular events. Live imaging reveals that Patiria miniata embryos from the Pacific are acutely sensitive to temperature; a 2°C increase from their normal temperature causes incomplete cleavage at the first cell division. These failed cytokinesis attempts display a loss of coordination between cell cycle progression and cytokinetic ring constriction as daughter nuclei progress into the next cell cycle before cleavage furrow ingression is completed. This may be due to altered biophysical properties of the cortex, or dysregulation of contractile machinery. However, some embryos recover in the subsequent cell cycle through a plastic, multipolar division. To explore how thermal tolerance is tuned to different environments, we test the resilience of cytokinesis in embryos from Asterias forbesi, a warmer water Atlantic sea star with significantly smaller oocytes. The embryos display similar incomplete cleavage and recovery phenotypes to P. miniata, but at 3°C higher temperatures. Surgically reducing the size of larger P. miniata oocytes towards that of A. forbesi rescues cytokinesis at elevated temperatures where normal-sized oocytes would experience incomplete cleavage. These findings suggest that adult adaptation to warmer waters correlates with embryonic thermal tolerance, and that multipolar compensation during embryonic cell division may be a conserved corrective response to thermal stress.