Search

The American lobster (Homarus americanus) is a commercially important crustacean with an unusual long life span up to 100 years and a comparative animal model of longevity. Therefore, research into its immune system and physiology is of considerable importance both for industry and comparative immunology studies. Peptidylarginine deiminases (PADs) are a phylogenetically conserved enzyme family that catalyses post-translational protein deimination via the conversion of arginine to citrulline. This can lead to structural and functional protein changes, sometimes contributing to protein moonlighting, in health and disease. PADs also regulate the cellular release of extracellular vesicles (EVs), which is an important part of cellular communication, both in normal physiology and in immune responses. Hitherto, studies on EVs in Crustacea are limited and neither PADs nor associated protein deimination have been studied in a Crustacean species. The current study assessed EV and deimination signatures in haemolymph of the American lobster. Lobster EVs were found to be a poly-dispersed population in the 10-500 nm size range, with the majority of smaller EVs, which fell within 22-115 nm. In lobster haemolymph, 9 key immune and metabolic proteins were identified to be post-translationally deiminated, while further 41 deiminated protein hits were identified when searching against a Crustacean database. KEGG (Kyoto encyclopedia of genes and genomes) and GO (gene ontology) enrichment analysis of these deiminated proteins revealed KEGG and GO pathways relating to a number of immune, including anti-pathogenic (viral, bacterial, fungal) and host-pathogen interactions, as well as metabolic pathways, regulation of vesicle and exosome release, mitochondrial function, ATP generation, gene regulation, telomerase homeostasis and developmental processes. The characterisation of EVs, and post-translational deimination signatures, reported in lobster in the current study, and the first time in Crustacea, provides insights into protein moonlighting functions of both species-specific and phylogenetically conserved proteins and EV-mediated communication in this long-lived crustacean. The current study furthermore lays foundation for novel biomarker discovery for lobster aquaculture.

The physiological consequences of exposing marine organisms to predicted future ocean scenarios, i.e. simultaneous increase in temperature and p CO 2 , have only recently begun to be investigated. Adult American lobster ( Homarus americanus ) were exposed to either current (16 °C, 47 Pa p CO 2 , pH 8.10) or predicted year 2300 (20 °C, 948 Pa p CO 2 , pH 7.10) ocean parameters for 14–16 days prior to assessing physiological changes in their hemolymph parameters as well as whole animal ammonia excretion and resting metabolic rate. Acclimation of lobster simultaneously to elevated p CO 2 and temperature induced a prolonged respiratory acidosis that was only partially compensated for via accumulation of extracellular HCO 3 – and ammonia. Furthermore, acclimated animals possessed significantly higher ammonia excretion and oxygen consumption rates suggesting that future ocean scenarios may increase basal energetic demands on H. americanus . Enzyme activity related to protein metabolism (glutamine dehydrogenase, alanine aminotransferase, and aspartate aminotransferase) in hepatopancreas and muscle tissue were unaltered in future ocean scenario exposed animals; however, muscular citrate synthase activity was reduced suggesting that, while protein catabolism may be unchanged, the net energetic output of muscle may be compromised in future scenarios. Overall, H. americanus acclimated to ocean conditions predicted for the year 2300 appear to be incapable of fully compensating against climate change-related acid-base challenges and experience an increase in metabolic waste excretion and oxygen consumption. Combining our study with past literature on H. americanus suggests that the whole lifecycle from larvae to adult stages is at risk of severe growth, survival and reproductive consequences due to climate change.

Fishery-dependent monitoring programs provide valuable information for the assessment and management of fishery stocks. The quality of the data and subsequent stock assessment are largely influenced by sampling design and sample size. The Lobster Sea Sampling Program in the Gulf of Maine yields critical information for the assessment of American lobster ( Homarus americanus ). To facilitate the use of an on-boat tablet-based data entry system, which will replace the current voice recording system, the sampling program requires development of a subsampling procedure to account for a decrease in the data recording speed after the new data entry system is implemented. We evaluated the performance of four potential subsampling strategies, including possible combinations of simple random vs. systematic subsampling with fixed subsample size vs. subsample size in proportion to reference data. Proportional subsampling showed lower relative estimation error and relative bias compared to subsampling with fixed subsample size. Within the two proportional subsampling strategies, systematic subsampling showed similar precision and accuracy compared to random subsampling, but systematic subsampling is more feasible to be conducted onboard. We concluded that the systematic subsampling of 50% of reference data could reduce current sampling effort but still capture the temporal trend of reference data. The simulation approach developed in this study can also be applied to optimize other fisheries-dependent monitoring programs.

The American lobster (Homarus americanus) is the most commercially important crustacean species in Eastern Canada. Fishery landings in Placentia Bay, Newfoundland have decreased steadily following the cod moratorium in 1992, with another noticeable drop in 2002 when the first invasion of the European green crab (Carcinus maenas) was likely to have happened. The effect of green crabs on the food consumption and catchability of lobsters was quantified in relation to crab density (n = 0, 1, 5, 25) and water temperature (4 °C, 12 °C). Food acquisition and behavioural responses of lobsters were unaffected by the water temperature or crab densities of 1 to 25 animals. However, when a lobster was pitted against 150 crabs they were unable to obtain any food and the crabs consumed all the food within 8 min. In contrast to lobsters, the green crabs consumed more food at the higher temperature because they were more active. As crab density increased the number of agonistic interactions and retreat behaviours increased at both temperatures, and crabs were more likely to retreat from a lobster than vice versa. The effects of green crabs on the catchability of lobsters around a baited trap was also investigated when crabs were freely mobile outside the trap or contained within the trap. Lobsters were more likely to approach and enter the trap at 12 °C than at 4 °C, however, they were also more likely to escape. Lobsters were less likely to approach or enter a trap if they interacted with crabs outside the trap. The present results suggest that interactions between green crabs and adult lobsters may influence lobster catch rates in Newfoundland.

The American lobster supports the most economically valuable fishery in the Gulf of Maine and Atlantic Canada. Across much of its range, ocean temperatures have increased at rates faster than almost anywhere in the world. Studies of warming effects on larvae have largely focused on survival and development, but rarely have examined sub-lethal effects that could influence settlement and subsequent recruitment to the fishery. We explored how warming influences rate of development, survival, stress, and developmental stability of larval lobsters reared under four nominal temperatures: 14, 16, 18, and 22 °C. Our study is the first to evaluate the use of fluctuating asymmetry as a biomarker for developmental instability in larval American lobster. We also recorded total hemocyte counts in postlarvae as an indicator of stress, a novel technique for work in larval lobster. Development proceeded significantly faster as temperature increased, and cumulative survival was significantly positively correlated with temperature. However, postlarvae reared under temperature extremes exhibited elevated hemocyte counts and had significantly lower levels of variance in midline asymmetry compared to intermediate temperature groups. Together, this suggests that warmer temperatures may facilitate faster growth at the expense of increased physiological stress and a loss of genetic diversity, potentially affecting the species’ ability to adapt to changing environmental conditions. Fluctuating asymmetry could prove to be a useful bioindicator for population resilience.

This paper provides the first record of ingestion of plastic debris by American lobster, Homarus americanus. Plastics particles, identified as rubber pieces, were found in the stomachs of 3 from 17 individuals of lobsters kept in laboratory conditions. Debris had evidence of cuts, what suggest they were actively consumed.

The transition from the last pelagic larval stage to the first benthic juvenile stage in the complex life cycle of marine invertebrates, such as the American lobster Homarus americanus, a species of high economic importance, represents a delicate phase in these species development. Under future elevated pCO2 conditions, ocean acidification and other elevated pCO2 events can negatively affect crustaceans. This said their effects on the benthic settlement phase are virtually unknown. This study aimed to identify the effects of elevated seawater pCO2 on stage V American lobsters exposed to seven pCO2 levels. The survival, development time, metabolic and feeding rates, carapace composition, and energy metabolism enzyme function were investigated. Results suggested an increase in mortality, slower development and an increase in aerobic capacity with increasing pCO2. Our study points to potential reduction in juvenile recruitment success as seawater pCO2 increases, thus foreshadowing important socio-economic repercussions for the lobster fisheries and industry.

We report on the characterization of the native form of an American lobster, Homarus americanus, β-defensin-like putative antimicrobial peptide, H. americanus defensin 1 (Hoa-D1), sequenced employing top-down and bottom-up peptidomic strategies using a sensitive, chip-based nanoLC-QTOF-MS/MS instrument. The sequence of Hoa-D1 was determined by mass spectrometry; it was found to contain three disulfide bonds and an amidated C-terminus. The sequence was further validated by searching publicly-accessible H. americanus expressed sequence tag (EST) and transcriptome shotgun assembly (TSA) datasets. Hoa-D1, SYVRS c SSNGGD c VYR c YGNIINGA c SGSRV cc RSGGGYamide (with c representing a cysteine participating in a disulfide bond), was shown to be related to β-defensin-like peptides previously reported from Panulirus japonicas and Panulirus argus. We found Hoa-D1 in H. americanus hemolymph, hemocytes, the supraoesophageal ganglion (brain), eyestalk ganglia, and pericardial organ extracts, as well as in the plasma of some hemolymph samples. Using discontinuous density gradient separations, we fractionatated hemocytes and localized Hoa-D1 to hemocyte sub-populations. While Hoa-D1 was detected in semigranulocytes and granulocytes using conventional proteomic strategies for analysis, the direct analysis of cell lysates exposed evidence of Hoa-D1 processing, including truncation of the C-terminal tyrosine residue, in the granulocytes, but not semigranulocytes. These measurements demonstrate the insights regarding post-translational modifications and peptide processing that can be revealed through the MS analysis of intact peptides. The identification of Hoa-D1 as a widely-distributed peptide in the lobster suggests the possibility that it may be pleiotropic, with functions in addition to its proposed role as an antimicrobial molecule in the innate immune system.

Utilization and interpretation of fishery-dependent data such as fishing effort, although important in quantifying the dynamics of a fishery, tend to be challenging due to non-random sampling and the complexity of quantifying a species’ interaction with complex effects of environmental factors. We developed a framework for estimating effective fishing effort from fishery-dependent sampling data for the coastal Maine American lobster (Homarus americanus) fishery, where a lack of high resolution effort data does not permit sufficient understanding of fishery dynamics. This framework incorporates environmental covariates in a bootstrapped two-stage generalized additive model to standardize lobster catch per unit effort (CPUE) from 2006 to 2013. Estimated confidence intervals (CIs) of sub-regional standardized CPUE were combined with congruent resolution landings data to estimate CIs of effective effort. Both effort and landings varied seasonally, with the peak of effective effort consistently preceding the peak of landings. Coast-wide from 2006 to 2013, effective effort increased modestly (4.6%) while landings increased dramatically (69.6%), suggesting assessment of spatiotemporal fishery dynamics may provide important insights for future management. Characteristic northeast-southwest differences in catch and effort suggest spatial non-stationarity of biological, temporal, and geographic processes in the Maine coastal American lobster fishery. The approach developed in this study has utility in situations in which a fishery may be data-limited, or with a surplus of fishery-dependent data.

Jonah crabs (Cancer borealis) have been caught as incidental bycatch for over 80 years, but in recent years they have become a targeted fishery, especially in Southern New England where the American lobster ( Homarus americanus) population has declined, and harvesters have begun seeking alternative fisheries. This shift has prompted the need for more biological data for Jonah crabs so that this expanding fishery can be managed more effectively. For example, in some areas of its range males have both of their claws removed at sea and only the claws are landed; however, little is known about what happens to the crabs that survive this practice. The focus of this study was to evaluate the impacts of claw removal on Jonah crab mating success, feeding ability and locomotion. In mating trials, all males, regardless of claw status, managed to successfully mate with females that molted while they were paired together (clawed n = 4, claws removed n = 8). When Jonah crab activity was measured in the laboratory, crabs with intact claws were significantly more active than crabs with both claws removed (clawed: 25.0 ± 8.0% of each hour active, 1 claw removed: 18.1 ± 7.3% of each hour active, clawless: 13.6 ± 9.04% of each hour active, mean ± SD). Similarly, based on data from a tag/recapture experiment, crabs with both claws missing moved about half the distance per day as control crabs, between the time they were released and first recaptured (clawed: 117 ± 43.1 m/day, clawless: 50 ± 11.3 m/day, mean ± SE), although the difference was not significant. These changes in locomotion could be the result of the blood loss associated with claw removal. We found that hemocyanin levels dropped significantly after the removal of both claws and remained so for up to two weeks. Finally, crabs with no claws were able to feed, but they had difficulty opening mussel shells, which might influence their diet in their natural habitat. These data suggest that those Jonah crabs that do survive the claw removal process might be impaired, but should be able to forage, mate, and help sustain the population.

Chlorpyrifos is an organophosphate that is currently used to reduce arthropod pests for the protection of agricultural crops. Coastal marine ecosystems may be exposed to agricultural pesticides via runoff and pesticide exposure can impact the health and survival of non-target species such as the American lobster (Homarus americanus). In the current study, the gene expression changes of H. americanus stage IV larvae were evaluated to understand the physiological mechanisms affected by exposure to sublethal concentrations of chlorpyrifos. After 48 h chlorpyrifos exposure, surviving lobsters were processed for Illumina RNA sequencing (RNA-seq). Genes of interest that showed significant changes using RNA-seq were verified using reverse transcriptase quantitative polymerase chain reaction (RT-qPCR). Analysis of RNA-seq and the confirmation of gene expression patterns via RT-qPCR found altered expression in genes related to stress response (glutathione peroxidase 3 and heat shock protein 60), hypoxia response (hairy, astakine 2, hemocyanin), moulting (cytochrome P450 307a1 and chitinase), and immunity (astakine 2) pathways. Changes to gene expression were most notable in lobsters exposed to 0.57 μg/L chlorpyrifos.

Southwest Nova Scotia (SWNS) is Canada's most productive lobster (Homarus americanus) fishing region. Abandoned, lost, and discarded fishing gear (ALDFG) is widespread. This baseline study provides the first preliminary assessment of environmental and economic impacts of ALDFG on the commercial lobster industry in SWNS. Fishers conducted 60 retrieval trips, searched ~1523 km2 of the seafloor and removed 7064 kg of ALDFG (comprising 66% lobster traps and 22% dragger cable). Results showed that lost traps continued to capture target and non-target species until gear degraded. A total of 15 different species were released from retrieved ALDFG, including 239 lobsters (67% were market-sized) and seven groundfish (including five species-at-risk). The present findings, combined with information on regional fishing effort and market prices, estimate that commercial losses from ALDFG can exceed $175,000 CAD annually. This baseline assessment provides useful data for government and commercial fishing stakeholders to improve ALDFG management.

Globally, lobsters are one of the most economically valuable wild species caught in capture fisheries. Catches are dominated by American lobster (Homarus americanus) landed entirely in Atlantic Canada and northeastern United States. In Atlantic Canada, lobster fishing and marine finfish aquaculture take place in the same coastal waters creating the potential for negative environmental, as well as social, interactions. We review the state of knowledge of environmental interactions between American lobster, their habitat and fishery, and marine finfish aquaculture. We first provide a brief overview of key biological, behavioural, and ecological processes and environmental stressors of American lobster at different life-history stages followed by an overview of the pathways of effects of marine finfish aquaculture on coastal ecosystems in general and on American lobster. Our review found that certain finfish aquaculture-lobster interactions have received considerable study (e.g., chemical use), whereas knowledge of other interactions are either limited (e.g., net pens, waste discharges) or lacking (e.g., disease, noise, lights, and odours). An ecosystem-based approach to aquaculture has been proposed for managing these interactions but implementing this approach has proven to be a challenge in part because of complex multi-sector, multi-stakeholder and multi-agency governance issues. While governance solutions await development, practical measures based on the results of scientific research identified in this review, such as better use of existing oceanographic and bathymetric data, habitat and human impact assessment tools, and toxicity information offer regulators ample information and management tools, at least at the farm- and bay-scale, to avoid negative finfish aquaculture-lobster interactions in Atlantic Canada. Bridging the governance gap will likely require new community-based management models that more effectively identify, generate, and integrate local community and fisher knowledge and concerns.

Fishery-independent ventless trap surveys are an integral component to assessing American lobster (Homarus americanus) population trends, as they can sample complex, heavily fished habitats where most survey gear has difficulty accessing. U.S. American lobster stocks have been assessed within state waters using a standardized ventless trap survey since 2006. However, confounding survey attributes that may contribute to catch variability have not been investigated and some discontinuity in sampling has resulted in missing estimates of abundance. We constructed sex- and stock-specific generalized linear mixed models to discern the dynamics between lobster catch and individual survey factors and removed these sources of variability when producing continuous abundance indices. Soak time, day of year, and unique site had measurable contributions to the variability in lobster catch per ventless trap. Generally, sex- and stock-specific abundance indices from this model-based approach and a traditional design-based approach exhibited similar trends. The two approaches’ magnitudes and trends for the Gulf of Maine were nearly identical. For Southern New England, model-based index trends were smoother and lower in magnitude than the design-based estimates. The greatest difference in the two approaches’ trends for the Southern New England indices were in the early and terminal years. This work serves as an example of how variability associated with fixed and random effects of a survey can be accounted for when producing abundance indices used in stock assessments.

Green crabs (Carcinus maenas) are an invasive species documented as having negative impacts on the biota of marine and estuarine communities. However, their impact on the American lobster (Homarus americanus) is not well understood. During a two-year trap study (2013–2014) in The Great Bay Estuary, NH, we captured 1229 green crabs and 144 lobsters in 248 individual trap hauls (average catch per unit effort = 10.98 ± 1.51 for green crabs and 0.49 ± 0.08 for lobsters), or ∼8.5 times more green crabs than lobsters. In general, green crabs were more abundant in areas furthest from the coast (up-estuary), which also tended to be warmer, while lobsters were more abundant in areas closer to the coast (down-estuary). Nevertheless, there was still considerable overlap between the two species. We evaluated the competitive interactions between green crabs and lobsters in the laboratory using a behavioral assay and found that in 31% of the trials, large lobsters (>80 mm in carapace length) killed (and consumed) green crabs of varying sizes that failed to escape or move to safe areas of the enclosure. These results suggest that adult lobsters are not likely vulnerable to green crabs. While there may be reasons why lobsters did not select specific sizes of green crabs to prey on, some crabs may have an impact on juvenile lobsters. These data provide some insight into the distribution and abundance of green crabs and their impact on the lobster population in a large New England estuary that supports a commercial lobster fishery.

Abundance index (AI), used to establish the suitability index (SI), provides critical information in habitat suitability index (HSI) modeling. The distributions of AIs derived from fisheries-independent surveys tend to be right skewed because of heterogenous distributions of fishes. The existence of large AI values and failure to consider it might result in underestimation of HSI values for most sampling areas. We compared the performance of HSI models based on original AIs (without any transformation) versus rescaled AIs (i.e., log-transformed AIs) using American lobster ( Homarus americanus ) along the coast of Gulf of Maine as an example. Impacts of weighting environmental variables on HSI modeling based on boosted regression tree (BRT) were also evaluated. Both cross-validation and predicted habitat suitability maps suggested that the weighted HSI model based on log-scaled AI data tended to yield a more reliable prediction of optimal habitats for American lobster. The unweighted HSI model based on the original AI data, however, tended to underestimate optimal habitats and overestimate suboptimal habitats. We recommend using log-transformed AIs and determining the weights of different environmental variables based on the BRT method in HSI modeling, especially when AI data are highly skewed.

Like most ectothermic species, American lobster growing in warmer environments mature at smaller sizes. A formal quantification of this pattern at multiple spatiotemporal scales has not been developed, impeding the development of tools to predict the impacts of climate change on American lobster life-history and fishery. In this study, data from sea sampling programs from southern New England to the Bay of Fundy are used to estimate female lobster size at maturity, and to quantify the effects of water temperature on maturity at three spatial scales: i) regional (∼1000 km), ii) stock (100 s km), and iii) Statistical Area (10 s km). Results show that female lobsters living in warmer waters mature at smaller sizes and that other factors, likely fishing, also contributed to the observed decrease in length at 50% maturity. This study suggests that adaptive management plans need to consider temperature-induced trends in size at maturity to ensure sustainability of the valuable American lobster fisheries. Additionally, this study provides a maturity function for use in models that aim to project effects of climate change on American lobster populations and fisheries dynamics.

Male American lobsters have a well-defined reproductive cycle in which almost all mating activity occurs in the prolonged intermolt period when they remain in molt stage early D 0 for 1–3 yrs. In a study that followed 19 males through 2–4 mating seasons, 97% of the 733 inseminations occurred at this stage. Males mated with as many as 54 females in a mating season, and there was a strong correlation between the number of females the males inseminated and the availability of molting females. The mean number (±SD) of inseminations in a mating season was 22 (±11), and mean time (±SD) between inseminations was 3.5 (±1) days. The incidence index of males inseminating two females on the same day, if they had the opportunity, was 22%. After 3 days, the incidence of being able to inseminate a second female was 95%. In contrast, in the years the males molted, their mean number of inseminations was only 1 (±2), and 53% of the males did not mate with any females. The weight of extruded spermatophores increased due to hydration, as noted by Francis Herrick over 100 years ago. Mean weight of electroejaculated spermatophores increased 39% within 5 min of being in contact with seawater, and 154% within 30 min. Due to the spermatophore’s contact with seawater when ejaculated, and the water that enters the seminal receptacle during mating, hydration of the spermatophore appears to be a factor in the male’s ability to fill the seminal receptacle. Males that inseminated 30 to 54 females in one mating season showed little indication of being sperm depleted. Almost all the females inseminated by these males near the end of the mating season spawned and carried full clutches of fertilized eggs.

A total inventory of density defined objects of American lobster cuticle was obtained by using high resolution 3D Xray tomography, micro-computed-tomography. Through this relatively unbiased sampling approach several new objects were discovered in intermolt cuticle of the lobster carapace. Using free and open-source software the outlines of density-defined objects were obtained and their locations in 3D space calculated allowing population parameters about these objects to be determined. Nearest neighbor distances between objects allowed interpretations of structural relationships of and between objects. Several organule types are recognized by their structural outlines and density signatures. A hierarchy of organule types and distribution suggests they develop during sequential molts. New objects (stalactites, Bouligand spirals, and basal granules) are described as mineral structures with well defined morphological character, allowing them to be recognized by their descriptive names and distributions. The three new cuticular objects appear to represent forms of calcium carbonate deposition in the sequential layers of exocuticle, endocuticle and membranous layer and may provide signatures of underlying epidermal cells.

American and European lobsters are both high profile and high value animal species that provide significant economic value in the areas where they are landed. As such, it is important to understand the factors that contribute to the health of the animals and their populations, and how these animals can defend against pathogen impacts, especially the components of their immune systems. It is somewhat surprising to see that there is a considerable amount of published information on the immune systems other commercially important crustacean species such as warm-water marine and freshwater shrimp and crayfish, yet the is relatively little published material on the American and European lobsters. This review highlights the key areas of crustacean immune function and the published evidence as it relates to these important species. This includes; pattern recognition receptors, variable immune molecules, clotting factors, prophenoloxidase, hemocytes and anti-bacterial/anti-micorbial components.

Warming generally improves performance of life processes such as moulting and growth in ectotherms, but excessive warming can reduce performance and cause death, which in turn affects their demography. Previous studies of American lobster, Homarus americanus , have considered warming impacts on benthic adults, but little attention has been paid to performance of planktonic larvae at extremely high temperatures. Water column temperatures are expected to increase faster than bottom temperatures, so warming may compromise physiological performance of larvae sooner than that of adults. It is thus important to identify stressful and lethal temperatures for lobster larvae, and include these when estimating climate change impacts. Previous studies that observed survival, development, moulting, growth, and physiological performance of lobster larvae at extreme temperatures were reviewed. Mortality following short-term exposure to 28–36 °C from minutes to hours in duration has been reported, but more ecologically-relevant longer-term high-temperature exposures lasting days or weeks have rarely been tested for larvae of this species. Sub-lethal indicators of stress such as irregular heartbeat were reported in short- and long-term exposures between 20 and 26 °C, suggesting that perhaps extended exposure to these temperatures could be lethal. Over the next 10–50 years, larvae may experience temperatures up to 30 °C, which could negatively impact lobster populations if these temperatures are indeed stressful or lethal to them. Knowledge gaps identified highlight the need for further research into tolerance of lobster larvae to high temperatures.

The first good evidence of the role of intensive commercial fishing in the decline and possible extinction of a marine parasite is presented. The larva of Stichocotyle nephropis Cunningham, 1887 (Aspidogastrea: Digenea) was described in 1887 from the outside of the intestine of the decapod crustacean Nephrops norvegicus (L., 1758) in the North Sea. Similar larvae were found outside the intestine of the American lobster Homarus americanus (Milne-Edwards, 1837) caught off New England in 1895. The adult form was first found in 1898 in the bile ducts of the thornback ray Raja clavata (L., 1758) from the North Sea, then in the barndoor skate Dipturus laevis (Mitchill, 1818) caught off Nantucket. There have been few records of its occurrence since then, with the last records from the northeast and northwest Atlantic published in 1972 and 1986 respectively, despite the recent attempts reported herein to find larvae and adult parasites. Both the elasmobranch final hosts are listed as “near threatened” or “ endangered” and the latest evidence on their population sizes suggests that they may have been fished to below the thresholds required for successful transmission of the parasite.

Homarus americanus, known as American lobster, is fully covered by its exoskeleton composed of rigid cuticles and soft membranes. These soft membranes are mainly located at the joints and abdomen to connect the rigid cuticles and greatly contribute to the agility of the lobster in swimming and preying. Herein, we show that the soft membrane from American lobster is a natural hydrogel (90% water) with exceptionally high toughness (up to 24.98 MJ/m3) and strength (up to 23.36 MPa), and is very insensitive to cracks. By combining experimental measurements and large-scale computational modeling, we demonstrate that the unique multilayered structure in this membrane, achieved through the ordered arrangement of chitin fibers, plays a crucial role in dissipating energy during rupture and making this membrane tough and damage tolerant. The knowledge learned from the soft membrane of natural lobsters sheds light on designing synthetic soft, yet strong and tough materials for reliable usage under extreme mechanical conditions, including a flexible armor that can provide full-body protection without sacrificing limb mobility. Statement of significance A body armor to provide protection to people who are at risk of being hurt is only enabled by using a material that is tough and strong enough to prevent mechanical penetration. However, most modern body armors sacrifice limb protection to gain mobility, simply because none of the existing armor materials are flexible enough and they all inhibit movement of the arms and legs. Herein, we focus on the mechanics and mesoscopic structure of American lobsters’ soft membrane and explore how such a natural flexible armor is designed to integrate flexibility and toughness. The knowledge learned from this study is useful to design a flexible armor for full-body protection under extreme mechanical conditions.

The Gulf of Maine (GOM) ecosystem has experienced significant changes in the last few decades with a great increase in the American lobster Homarus americanus population and substantial reduction in some groundfish populations like Atlantic cod Gadus morhua. This study evaluated and compared the energy flows and trophic structures of the GOM ecosystem in the mid-2000s and mid-2010s. Following an early study, two mass-balance ecosystem models, each of which include 25 functional groups, were updated for the mid-2000s and mid-2010s using Ecopath. Fishing efforts were used as forcing drivers to simulate the variation of the GOM ecosystem in the mid-2000s to mid-2010s. Similar to the GOM ecosystem from the 1980s to 1990s found in a previous study, dominant species in both the mid-2000s and mid-2010s ecosystems were transferred from top predators to crustacean species in the last decade. However, food web structure of the GOM ecosystem became more complex, stable, and flexible to perturbations, indicating that the GOM ecosystem is moving toward a more mature stage. Simulation results indicated that fishing activities were considered to be the main driver to the variations dynamics of most species in the GOM ecosystem, while some species like Atlantic herring Clupea harengus might also suffer from changes in environmental conditions. This study provides a comprehensive overview on the changes in the GOM ecosystem in the last two decades.

Understanding compliance is important for understanding the effectiveness of conservation. This study examines conservation compliance in the American lobster fishery in Maine. In this fishery, an important conservation measure that protects spawning female lobsters, known as v-notching, is considered a norm. This conservation rule is primarily self-enforced, but evidence suggests that its compliance rate may be declining. We analyzed semi-structured and oral history interviews to understand v-notching compliance and lobster fishers' perceptions of v-notching. All lobster fishers interviewed described v-notching as important for the lobster fishery's sustainability, while also reporting that the v-notching practice has been declining in recent years. Conservation compliance changed as the benefits of conservation changed. Because of large lobster catches, lobster fishers have begun to question whether v-notching is as necessary as it was in the past. High catches in recent years also created time constraints on board the vessel that limit the ability to v-notch. Long-term changes in abundance and consequently landings impacted the norm of v-notching. Under new conditions of the lobster resource, v-notching as a norm may be weakened, as there are now conflicting views on the benefits of v-notching. The implications of a reduction in v-notching may be significant for the future sustainability of this fishery given studies that have shown the conservation value of this practice. This study highlights the importance of considering changes in conservation compliance in adaptive management plans due to changes in benefits and costs caused by changing resource conditions.

Crustaceans, such as crab and lobster, comprise an important global food commodity. They are captured in traps using primarily forage fish (e.g. anchovies, herring, and menhaden), as bait. Approximately 18 million tons of these fish are used annually to bait traps, worldwide (U. Nations, 2014). In addition to natural predators dependent on forage fish (Pikitch et al., 2012), myriad other factors are further intensifying demand and collectively threatening stocks (e.g. Omega-3 supplements, pet food, livestock feed,–in addition to direct human consumption). Forage fish capture methods pose collateral environmental risks from by-catch (e.g. seals, dolphins, turtles) indiscriminately killed in nets. Sustainable alternatives to stem further depletion are desperately needed, and toward this end, a synthetic crustacean bait has been developed. The technology mimics molecules released from forage fish by employing a formulation that is dispersed at a controlled rate from a soluble matrix. The synthetic bait reliably caught stone crab, blue crab, and American lobster in field trials. This technology addresses major ecological threats, while providing economic and operational benefits to the crustacean fishing industry.One Sentence Summary: A synthetic crustacean bait has been developed to obviate the need for forage fish capture and depletion.

A bioclimate envelope model was developed to evaluate the potential impacts of climate variability on American lobster ( Homarus americanus ). Bioclimate envelopes were defined by season-, sex-, and stage- specific Habitat Suitability Indices (HSI) based on (1) bottom temperature, (2) bottom salinity, and (3) depth. The species’ association to each of these three environmental attributes was expressed using Suitability Indices (SIs) calibrated by standardized lobster abundance derived from 14 years of fishery independent survey. A regional ocean model (Finite-Volume Community Ocean Model) was integrated with the HSI to hindcast spatiotemporal variability of bioclimate envelopes for American lobster in coastal waters of Maine and New Hampshire from 1978 to 2013. The model predictions indicated higher habitat suitability in inshore waters for both adult and juvenile lobsters. A statistically significant increasing trend in habitat suitability was observed for both sexes and stages (juvenile and adult) during the spring (April–June), while no significant trend in habitat suitability was observed in the fall (September–November). This study provides a modeling framework to reconstruct climatically suitable lobster ranges that can be used to formulate climate-based hypotheses for future studies of this species.

Commercial fisheries contribute to a number of non-localized environmental and resource depletion problems, such as climate change, through the provision and use of fossil fuels, vessels, gear, refrigeration, and bait, and during post-capture processes. Here, we investigate the degree to which different management regimes may affect two fisheries’ contributions to a suite of non-localized environmental concerns. Life cycle assessment (LCA) is used to quantify the contributions made by the 2006 Maine and 2005–2006 southwest Nova Scotia fisheries for American lobster ( Homarus americanus ) to a suite of global environmental problems. The lobster fishery phase was the primary driver of resource and environmental impacts as characterized in the selected impact categories. Direct diesel use by the lobster boat was the primary source of impacts at the fishery phase, but the provision and use of bait was also a substantial contributor, particularly in the Maine fishery. Post-capture transportation of live lobster by air was a major contributor in the LFA 34 model. Lobstermen in both fisheries reported using approximately one liter of fuel per kilogram of lobster landings, but Maine lobstermen reported using three kilograms of bait per kilogram of lobster landings, while LFA 34 lobstermen reported using only one kilogram of bait per kilogram landings. The difference in bait use per unit landings resulted in the Maine lobster fishery having slightly higher global environmental impacts, when measured by the chosen impact categories, than the Nova Scotia fishery. However, the two fisheries’ contributions to the selected environmental impact categories were broadly similar, despite their different management regimes, and an obvious influence of management was not identified. The findings for the lobster fisheries are placed into context with other food production systems.

The American lobster (Homarus americanus) fishery is the most economically significant fishery in Canada; although comparatively little is known about the lobsters' response to pathogenic challenge. This is the first study to investigate the expression of immune genes in tissues outside of the lobster hepatopancreas in response to challenges by the Gram-positive bacteria, Aerococcus viridans var. homari or the scuticociliate parasite, Anophryoides haemophila. The hepatopancreas has been regarded as the major humoral immune organ in crustaceans, but the contribution of other organs and tissues to the molecular immune response has largely been overlooked. This study used RT-qPCR to monitor the gene expression of several immune genes including three anti-lipopolysaccharide isoforms (ALF) Homame ALF-B1, Homame ALF-C1 and ALFHa-1, acute phase serum amyloid protein A (SAA), as well as thioredoxin and hexokinase, in antennal gland and gill tissues. Our findings indicate that the gene expression of the SAA and all ALF isoforms in the antennal gland and gill tissues increased in response to pathogenic challenge. However, there was differential expression of individual ALF isoforms that were dependent on both the tissue, and the pathogen used in the challenge. The gene expression changes of several immune genes were found to be higher in the antennal gland than have been previously reported for the hepatopancreas. This study demonstrates that increased immune gene expression from the gill and antennal gland over the course of pathogen induced disease contributes to the immune response of H. americanus.

North Atlantic right whales (Eubalaena glacialis) feed and migrate in areas of the inshore and offshore trap fishery for American lobster (Homarus americanus) in the Northeast U.S. In addition to a recent increase in lethal and sub-lethal interactions with Canadian snow crab gear, entanglement in both Canadian and U.S. lobster trap gear threatens the continued existence of this endangered species. The U.S. National Marine Fisheries Service is considering a number of measures to prevent right whale entanglement bycatch that could impact lobster fishing effort. The U.S. lobster fishery in Maine expends approximately 7.5 times as much effort as the Canadian fishery in Lobster Fishing Area 34, where Canadian fishers catch about 3.7 times more lobster per trap than their counterparts in Maine. From 2007 to 2013 in Maine, lobster landings doubled as the number of traps fell 10.5% and landings per trap increased by about 125%. The state of Massachusetts has achieved record high landings since trap/pot seasonal closures have been implemented to protect right whales, especially within the Statistical Reporting Areas most affected by the closures. Therefore, a negative economic impact should not be assumed with effort reduction. In fact, reducing effort may serve to increase fishing profits while supporting the protection of endangered North Atlantic right whales and the long-term sustainability of the lobster fishery.

A bleached kraft pulp mill operating in Nova Scotia, Canada has discharged effluent into a former tidal estuary known as Boat Harbour since 1967. After treatment in Boat Harbour, effluent is discharged into Northumberland Strait. Contaminated sediments in Boat Harbour are slated for remediation following cessation of effluent discharge. A review of historical documents to identify contaminants in marine biota in Northumberland Strait found insufficient data to properly assess baseline conditions prior to remediation. This study measured metal, methylmercury, dioxin and furan concentrations in surficial sediments and American lobster (Homarus americanus), rock crabs (Cancer irroratus) and blue mussels (Mytilus edulis) in Northumberland Strait. When compared to Canadian Council of Ministers of the Environment sediment quality guidelines and Canadian Food Inspection Agency tissue guidelines results indicated limited contamination in sediments and biota, posing low risk to marine biota. Long-term monitoring is recommended to verify effectiveness of remediation.

Ventless (escape vents blocked) trap surveys are becoming increasingly common and provide data that are useful for making well-informed management decisions. The purpose of this study was to conduct ventless and standard trap surveys, in parallel with SCUBA surveys, to determine how lobster catch in both types of traps relates to the size structure and abundance of lobster populations on the bottom. Because trap saturation may affect catch-per-unit-effort, we also quantified how catch changed over time by pulling traps after a period of 10 distinct soak times, ranging from 2 to 96 h. All surveys were carried out in 2010 and 2011, at a study site along the coast of New Hampshire, USA. Ventless traps collectively captured ∼10 times as many lobsters as standard traps, but the mean size of the lobsters captured did not differ between the trap types. Catch in standard traps changed little over time and thus the time to saturate was difficult to assess. However, ventless traps saturated between 16 and 24 h. Ventless traps saturated at all lobster densities, but had higher final catch values at times when lobsters were most abundant (as determined by SCUBA surveys). These data indicate that ventless traps provide valuable information about natural lobster populations, which can be useful in the assessment of this valuable fishery.

American lobster, Homarus americanus, continues to be an ecologically and socioeconomically important species despite a severe decline in catches from Southern New England and Long Island Sound (USA) and a high prevalence of epizootic shell disease in these populations. A better understanding of lobster immune defenses remains necessary. Cuticle material collected from Long Island Sound lobsters was found to be active against a broad spectrum of bacteria, including Gram-negative and -positive species. The antimicrobial activity was characterized by boiling, muffling, and size fractioning. Boiling did not significantly reduce activity, while muffling did have a significant effect, suggesting that the active component is organic and heat stable. Size fractioning with 3 and 10 kDa filters did not significantly affect activity. Fast protein liquid chromatography fractions were also tested for antimicrobial activity, and fractions exhibiting protein peaks remained active. MALDI mass spectrometry revealed peptide peaks at 1.6, 2.8, 4.6, and 5.6 kDa. The data presented suggest that one or several antimicrobial peptides contribute to antimicrobial activity present in the American lobster cuticle.

Throughout the world, several efforts currently exist for restocking clawed lobster ( Homarus sp.) by releasing mass amounts of postlarvae in the wild. Therefore, optimization of hatchery techniques and evaluation of their influence on lobster postlarvae behavior at release time are of interest. This study looked at the effects of light regime (photoperiod and light intensity) on growth, survival, and behavior of American lobster postlarvae (stage IV) at release time. Results showed that photophase length did not induce any significant differences in growth and survival at 100 lx. Light intensity did not affect larval development at 16 h photophase. Results showed a significant interaction between the two factors (photoperiod and light intensity) on larval survival, but not on growth. When compared to other studies, our results indicate that the feeding time (night vs. day) may be of importance for optimizing growth and survival of early larvae. Behavior results clearly demonstrated that the age of the lobster at postlarvae stage IV had more influence than the day length or light intensity, and that the light intensity induced more variability than the day length. The results suggest that a light regime of 16 h photophase at 1000 lx light intensity, both survival and settling behavior at release time.

article i nfo The American lobster, Homarus americanus, is an important benthic consumer in the Gulf of Maine and supports anextremely valuable fishery in New England and eastern Canada. Meanwhile, there issubstantial interest in re- storing large predator fish species to the Gulf of Maine, and these predators may impact lobster populations both by consuming them and by inducing them to alter their behavior. Lobster tethering experiments were used to examine the susceptibility of a range of lobster size classes to predation in Saco Bay, Maine. The most susceptible sizes of lobsters were then exposed to three different fish predators (Atlantic striped bass Morone saxatilis, Atlantic cod Gadus morhua ,a nd sea ravenHemitripterus americanus) separately in experimental mesocosm tanks. Juvenile lobsters moved less and spent more time in shelter when in the presence of cod or sea raven. By contrast, striped bass did not induce lobsters to alter their behavior. Striped bass are highly mobile, active pursuit predators, which are thought to induce weaker behavioral responses in prey than sit-and-pursue predators like sea ravens. Thus, differences in lobster sheltering behavior corresponded with differences in predator foraging behavior. These predator-induced changes in behavior can result in less foraging activity, which may translate into reduced lobster growth and reproduction. Efforts to model marine communities and ecosystems will benefi tf rom am ore holistic understanding of whether predators induced prey to modify their foraging behavior and habitat usage.

Live lobsters are considered a fish product by European laws but no invertebrates welfare reference exists in European legislation. In this work the effect of commercial storage stress considering two different commercial maintenance methods (air exposure vs seawater resubmission) were evaluated. Thirteen different physiological variables of the hemolymph were analyzed: glucose, lactate, total protein, cholesterol, triglycerides, ammonia, chloride, calcium, magnesium, sodium, potassium and urea concentration, total haemocyte counts. Bacteriological analysis of hemolymph was performed in order to determine the possible penetration of microorganisms in the tissues. In this work, for the first time, the urea concentration was determined in these species: at arrival this parameter in hemolymph was 2.74 ± 1.04 mg dl−1, after 12 h in seawater the urea level decreased to 1.17 ± 0.72 mg dl−1. Thanks to this study, a single global parameter useful to measure the distress status was not evidenced, even if the determination of protein concentration was the easiest and cheapest one, although influenced by several factors. Ammonia and urea determination were the most specific parameters for the determination of the air transport distress.

The American lobster (Homarus americanus) is the most important commercially exploited marine species in Canada. Very little is known about the H. americanus molecular humoral immune response or how to determine if a seemingly healthy lobster is infected with a pathogen. The goal of this work is to characterize several important H. americanus immune genes as well as highlight and classify hundreds of others into functional immune groups. The protein sequence of H. americanus acute phase serum amyloid protein A (SAA) was found to be similar to that of vertebrate SAA, and is likely a good clinical marker for immune activation in lobsters and some crustaceans. Additionally, only one gene, Trypsin 1b, was found to be differentially regulated during bacterial, microparasitic and viral challenges in lobster and is likely critical for the activation of the H. americanus immune response. Bioinformatic analysis was used to functionally annotate, 263 H. americanus immune genes and identify the few shared patterns of differential gene expression in lobsters in response to bacterial, parasitic and viral challenge. Many of the described immune genes are biomarker candidates which could be used as clinical indicators for lobster health and disease. Biomarkers can facilitate early detection of pathogens, or anthropomorphic stressors, so that mitigation strategies can be developed in order to prevent the devastating economic losses that have occurred in Southern New England, USA. This work is contributes to further our understanding of how the lobster immune system works and how it can be used to maintain the health and sustainability of the overall American lobster fishery.

The abundance, biomass, diversity, and species composition of the demersal fish and invertebrate community in Rhode Island Sound and Block Island Sound, an area identified for offshore renewable energy development, were evaluated for spatial and seasonal structure. We conducted 58 otter trawls and 51 beam trawls in the spring, summer and fall of 2009–2012, and incorporated additional data from 88 otter trawls conducted by the Northeast Area Monitoring and Assessment Program. We used regionally-grouped abundance, biomass, diversity, and size spectra to assess spatial patterns in the aggregate fish community, and hierarchical cluster analysis to evaluate trends in species assemblages. Our analyses revealed coherent gradients in fish community biomass, diversity and species composition extending from inshore to offshore waters, as well as patterns related to the differing bathymetry of Rhode Island and Block Island Sounds. The fish communities around Block Island and Cox's Ledge are particularly diverse, suggesting that the proximity of hard bottom habitat may be important in structuring fish communities in this area. Species assemblages in Rhode Island and Block Island Sounds are characterized by a combination of piscivores (silver hake, summer flounder, spiny dogfish), benthivores (American lobster, black sea bass, Leucoraja spp. skates, scup) and planktivores (sea scallop), and exhibit geographic patterns that are persistent from year to year, yet variable by season. Such distributions reflect the cross-shelf migration of fish and invertebrate species in the spring and fall, highlighting the importance of considering seasonal fish behavior when planning construction schedules for offshore development projects. The fine spatial scale (10 s of kms) of this research makes it especially valuable for local marine spatial planning efforts by identifying local-scale patterns in fish community structure that will enable future assessment of the ecological impacts of offshore development. As such, this knowledge of the spatial and temporal structure of the demersal fish community in Rhode Island and Block Island Sounds will help to guide the placement of offshore structures so as to preserve the ecological and economic value of the area.

The integument of arthropods is an important first-line defence against the invasion of parasites and pathogens. Once damaged, this can be subject to colonisation by microbial agents from the surrounding environment, which in crustaceans can lead to a condition termed shell disease syndrome. This condition has been reported in several crustacean species, including crabs and lobsters. The syndrome is a progressive condition where the outer cuticle becomes pitted and eroded, and in extreme cases is compromised, leaving animals susceptible to septicaemia. This study examined the susceptibility of juvenile American (Homarus americanus) and European (Homarus gammarus) lobsters to shell disease, as a result of mechanical damage. Scanning electron microscopy was used as a method to identify differences in the cuticle structure and consequences of mechanical damage. Claw regions were aseptically punctured, whilst carapaces were abraded using sterile sandpaper, to mimic natural damage. After a period of between 10 and 12 weeks, lobsters were sacrificed, fixed and stored for later examination. The carapace and claws of juvenile American lobsters were shown to be thinner and more vulnerable to abrasion damage than their European counterparts. In addition, the number and distribution of setal pits and pore canal openings also differed between the two species of lobster. Mechanical damage resulted in the formation of shell disease lesions on the claw and carapace of both lobster species. However, American lobsters, unlike their European counterparts, had extensive bacterial colonisation on the margins of these lesions. Overall, it is concluded that the cuticle of the American lobster is more susceptible to damage and resulting microbial colonisation. This may have implications for susceptibility of both species of lobster to shell disease syndrome.

The release of hatchery-reared American lobster ( Homarus americanus ) is used, on some occasions, as a tool to enhance depleted lobster stocks. Current Canadian lobster enhancement programs rely on the release of postlarvae (stages IV and V), which are still vulnerable to high mortality. We hypothesized that larvae enriched in triglycerides (TAG) and polyunsaturated fatty acids (PUFA) during their development from stage I to stage IV have higher survival and growth rates. We assessed the condition, growth and survival of lobster postlarvae (stage IV) fed during their larval stages with live natural zooplankton, to maximise TAG and PUFA enrichment, compared to those fed a standard Artemia diet. Stage I larvae obtained from ovigerous wild females were cultured in the hatchery on either an Artemia or a zooplankton diet until stage IV (7 d old), when they were transferred to the field (i) individually in small boxes for 3 months or (ii) communally in large enclosures for 3–4 months to assess survival and growth in situ. Our results show that a diet of natural zooplankton significantly increases the TAG and PUFA content of larvae compared to a diet of live Artemia . Stage IV lobsters fed natural zooplankton had a better condition index (TAG/ST) and a higher activity of the enzyme regulating osmoregulation than those fed Artemia . Larvae fed zooplankton had a significantly higher growth rate than larvae fed Artemia , (655 vs 507 μm dry mass d − 1 , respectively). Despite these differences, survival was similar for both diets, in the hatchery as well as in situ, in predator-free situations. Nevertheless, a higher growth rate may be a potential survival advantage for newly released lobsters, allowing them to reach a size refuge from predation more rapidly. We conclude that even if live Artemia remains the best and most reliable source of live food for the production of American lobster larvae, it needs to be considerably enriched with PUFA, at levels comparable to that of natural zooplankton, to increase osmoregulation potential and growth.

Agricultural pesticide runoff has been suspected as the cause of numerous fish kills in rivers throughout Prince Edward Island but the impact on the surrounding marine environment is unknown. Endosulfan, an organochlorine pesticide, is a potent neurotoxin and molt inhibitor used to combat the Colorado potato beetle however it has the potential to affect non-target organisms including the American lobster (Homarus americanus). Metamorphosis is a critical stage of development and the effects of contaminant exposure during this time are largely unknown in lobster. A 14day endosulfan exposure was performed to identify the effects on survival, development and gene expression in lobster larvae during metamorphosis; all of which were predicted to be negatively impacted. The higher endosulfan concentrations resulted in greater mortality and a significant increase in the number of days required to reach metamorphosis in surviving animals. A custom made H. americanus microarray was used for monitoring the changes in expression of 14,592 genes at the termination of the exposure. Genes with >1.5 fold change and identified as being significant at p

The adult American lobster (Homarus americanus) is susceptible to few naturally occurring pathogens, and no viral pathogen is known to exist. Despite this, relatively little is known about the H. americanus immune system and nothing is known about its potential viral immune response. Hundreds of rural communities in Atlantic Canada rely on the lobster fishery for their economic sustainability and could be devastated by large-scale pathogen-mediated mortality events. The White Spot Syndrome Virus is the most economically devastating viral pathogen to global shrimp aquaculture production and has been proposed to be capable of infecting all decapod crustaceans including the European Lobster. An in vivo WSSV injection challenge was conducted in H. americanus and WSSV was found to be capable of infecting and replicating within lobsters held at 20 °C. The in vivo WSSV challenge also generated the first viral disease model of H. americanus and allowed for the high-throughput examination of transcriptomic changes that occur during viral infection. Microarray analysis found 136 differentially expressed genes and the expression of a subset of these genes was verified using RT-qPCR. Anti-lipopolysaccharide isoforms and acute phase serum amyloid protein A expression did not change during WSSV infection, contrary to previous findings during bacterial and parasitic infection of H. americanus. This, along with the differential gene expression of thioredoxin and trypsin isoforms, provides compelling evidence that H. americanus is capable of mounting an immune response specific to infection by different pathogen classes.

Mussels respond to threats from predators by increasing anti-predator traits, which include a suite of inducible defenses. Blue mussels (Mytilus edulis) can modify the strength, number and attachment site of byssal threads in response to water borne cues from predators and injured conspecifics. We quantified byssal thread production, attachment strength and movement in blue mussels of two size classes in response to effluent from the American lobster Homarus americanus, the rock crab Cancer irroratus, the sea star Asterias rubens, and injured conspecific mussels. In a factorial laboratory experiment, effluent from the predatory crab, C. irroratus, resulted in higher numbers of functional byssal threads compared only to exposure to injured conspecific mussels, and not to any other treatment group. Large mussels produced stronger byssal attachments than small mussels. Over 24 h, small mussels formed and released more byssus bundles than large mussels, an indication of increased movement. Small mussels started producing byssal threads sooner than large mussels. Mussels exposed to effluent from injured conspecific mussels began producing byssal threads earlier, compared to the control and not to any other treatment group. Our results show that byssogenesis was influenced by predator type and mussel size, whereas attachment strength and movement depended on mussel size. This study highlights the ability of two size classes of blue mussels to selectively alter byssal thread production and movement in the presence of injured conspecifics and potential predators.

We examined female American lobsters (Homarus americanus) for evidence of mating activity in selected regions within Gulf of Maine (GOM) and Southern New England (SNE) waters. The presence of a spermatophore in their seminal receptacles was used as an indication of mating activity (spermatophore positive, “SP”). To determine if all presumably-mature females had mated, the proportion of females that were SP was compared to the size-at-maturity data used in the Atlantic States Marine Fisheries Commission (ASMFC) American Lobster Stock Assessment. A total of 1696 females were examined, and in all regions >75% of these females were SP. In most regions, more presumably-immature females (based on pre-existing maturity data) were SP than expected, while in the two SNE regions (Rhode Island) there were more presumably-mature females lacking sperm than expected. We suggest that due to the depleted condition of the SNE lobster stock, the discrepancy between expected maturity and mating activity in SNE females warrants further attention. Additionally, our data suggest that there is a need to re-examine lobster size-at-maturity throughout the GOM lobster stock. It appears as if either the maturity schedules have recently shifted, or sexually immature females are regularly mating in many regions.

This is the first transcriptomic study focusing on immunity in the commercially valuable American lobster (Homarus americanus). We have conducted an in vivo infection trial using the Gram-positive bacterium Aerococcus viridans var. homari to determine how H. americanus responds to this naturally occurring lethal-pathogen. A novel H. americanus microarray was used to measure the transcriptomic changes occurring in over 14,000 genes in the lobster hepatopancreas. Hundreds of new immune genes and isoforms were identified and measured for the first time in this species, and our findings highlight 148 genes of interest involved in H. americanus pathogen response. We verified our microarray results using RT-qPCR on three anti-lipopolysaccharide (ALFHa-1, ALFHa-2, ALFHa-4), a thioredoxin, acute phase serum amyloid protein A, hexokinase and two trypsin genes. RT-qPCR and microarray findings show close agreement and highlight the significant increase in gene expression in many lobster immune genes during A. viridans infection. Differential expression of the ALFHa isoforms may indicate that the H. americanus immune response can be tailored to the class of pathogen causing disease.

The European green crab Carcinus maenas is an invasive species in the northwestern Atlantic that has the potential to compete and prey upon endemics such as juvenile American lobster Homarus americanus. Recent laboratory studies have reached opposite conclusions regarding the dominance relationship between these species, even documenting a reversal of roles as predator and prey. Interestingly, these contradicting results involved crab populations from different regions in Atlantic Canada (St. George's Bay in the Northumberland Strait and Passamaquoddy Bay in the Bay of Fundy), which are genetically different and presumed to be the result of different invasion events. In this study we housed juvenile lobsters and adult green crabs together in 3-m diameter flow-through tanks, and monitored their mortality, growth and behaviour from September through December 2009. The experiment involved five treatments, three experimental treatments with 2.5 lobsters/m2 housed with an equal density of green crabs from one of three regions (Passamaquoddy Bay, St. George's Bay or Chedabucto Bay on the Scotian Shelf) and two control treatments with lobsters alone stocked at either 2.5 or 5 individuals/m2. Chedabucto Bay was chosen as a third region as crabs there are genetically similar to conspecifics in St. George's Bay, but experience environmental conditions more similar to Passamaquoddy Bay. Green crabs had a significant and negative impact on lobster survival during the experiment, and the magnitude of this impact varied in relation to the green crabs' geographic origin, as mortality was significantly higher for lobsters paired with St. George's Bay and Chedabucto Bay crabs than Passamaquoddy Bay crabs. These differences in lobster mortality patterns lead to two important conclusions. First, the greater predatory impact of green crabs from St. George's Bay relative to Passamaquoddy Bay is consistent with the contrasting results recently reported in the literature, suggesting that these are of biological significance and not simply the result of procedural differences between studies. Second, the fact that the predatory impact of Chedabucto Bay green crabs was similar to that of conspecifics from St. Georges Bay, but greater than those from Passamaquoddy Bay, suggests that these differences in interspecific dominance patterns are correlated with genetic differences between green crab populations related to their invasion history in Atlantic Canada. The mechanisms underlying the effect of crab geographic origin on its interaction with juvenile lobster remain elusive, however, as no differences in crab behaviour or morphology were found that correlated with the pattern of lobster mortality.

Operant discrimination learning has been extensively utilized in the study on the perceptual ability of animals and their higher order brain functions. We tested in this study whether American lobster Homarus americanus, which was previously found to possess ability of operant learning with claw gripping, could be trained to discriminate light stimuli of different intensities. For the current purpose, we newly developed a PC-controlled operant chamber that allowed the animal under a body-fixed condition to perform operant reward learning with claw gripping. Lobsters were first reinforced when they gripped the sensor bar upon presentation of a light cue. Then they were trained to grip the bar only when the light stimulus of a specific intensity was presented to obtain food reward while the stimuli of three different intensities including the reinforced one were presented in a random order. Finally, they were re-trained to grip the bar only when the light stimulus of another intensity that was not rewarded in the preceding training to obtain food while other intensities including the one that was rewarded previously were not rewarded any more. In these training procedures, the operant behavior occurred more frequently in response to the rewarded cue than to the non-rewarded one. The action latency for the reinforced stimuli showed a significant decrease in the course of training. These data demonstrate that lobsters can be trained with the light cues of different intensity as discriminative stimuli under a restrained condition that would allow application of electrophysiological techniques to the behaving subjects.

In arthropods, ecdysteroids regulate molting by activating a heterodimer formed by the ecdysone receptor (EcR) and retinoid X receptor (RXR). While this mechanism is similar in insects and crustaceans, variation in receptor splicing, dimerization and ligand affinity adds specificity to molting processes. This study reports the EcR and RXR sequences from American lobster, a commercially and ecologically important crustacean. We cloned two EcR splice variants, both of which specifically bind ponasterone A, and two RXR variants, both of which enhance binding of ponasterone A to the EcR. Lobster EcR has high affinity for ponasterone A and muristerone and moderately high affinity for the insecticide tebufenozide. Bisphenol A, diethyl phthalate, and two polychlorinated biphenyls (PCB 29 and PCB 30), environmental chemicals shown to interfere with crustacean molting, showed little or no affinity for lobster EcR. These studies establish the molecular basis for investigation of lobster ecdysteroid signaling and signal disruption by environmental chemicals.

Adult green crabs are highly aggressive predators that exhibit fast population growth in newly invaded areas and potentially compete with juvenile lobsters for limited resources. Previous studies suggest that juvenile lobsters utilize shelter to avoid predation but shelter dependence decreases as they mature and develop predator defense mechanisms. Smaller lobsters must therefore trade-off energetic needs with predation risk. In laboratory experiments we examined how the presence of an adult green crab affects foraging and shelter behavior of juvenile lobsters (25–51 mm CL) by offering juvenile lobsters protective shelter and an adjacent food patch in the presence or absence of a green crab. For each trial we monitored lobster behavior over 8 h. Our results indicate that in the presence of a green crab, small juvenile lobsters (

Analyses of six years of bottom trawl data collected from Northumberland Strait, southern Gulf of St. Lawrence revealed four major fish assemblages, two of which occurred in the same two geographic areas each year. One of the two persistent assemblages occurred in deeper water off northwestern Prince Edward Island and consisted mostly of demersal fishes. The other persistent assemblage contained a mixture of demersal and pelagic fishes and occurred primarily in shallow water of central Northumberland Strait. Analyses of abiotic (depth, bottom temperature, substratum type) and biotic (presence of American lobster Homarus americanus , northern lady crab Ovalipes ocellatus ) factors revealed bottom temperature and catches of lady crab correlate best with the fish assemblage structure each year, but correlation values were low ( ρ w ≤ 0.48). Combinations of all abiotic and biotic variables only marginally improved the strength of the correlations in four of six years (2002, 2003, 2005, 2006). Changes observed in the Northumberland Strait ecosystem over the six years included an increase in the ratio of pelagic to demersal fishes, disappearance of one of the four assemblages, and increased spatial overlap between the two persistent assemblages, which coincided with an increase in bottom temperature. The increasing importance of pelagic fishes, relative to demersal fishes, suggests a shift in food web structure may be occurring in Northumberland Strait.