The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Nicholas Santangelo - One of the best experts on this subject based on the ideXlab platform.
-
accumulation of nonessential trace elements ag as cd cr hg and pb in atlantic horseshoe crab Limulus polyphemus early life stages
Science of The Total Environment, 2017Co-Authors: Aaron K. Bakker, Jessica Dutton, Matthew Sclafani, Nicholas SantangeloAbstract:During early development, benthic organisms can accumulate nonessential trace elements through aqueous and particulate sources. This study investigated the accumulation of Ag, As, Cd, Cr, Hg and Pb in Atlantic horseshoe crab (Limulus polyphemus) pre-spawned eggs, embryos, and developing larvae collected from 5 sites on Long Island, NY and compared these concentrations to that found in sediment, pore water, and overlying water. All investigated elements were detected in embryos and larvae at all sites. Arsenic was found at the highest concentration in each life stage across all 5 sites, followed by Ag, whereas Cd, Hg and Pb concentrations varied between sites. Chromium was not detected in pre-spawned eggs, but was present in embryos and larvae at all sites, however, along with Hg, significantly increased from embryo to larvae at most sites. We conclude that observed accumulation patterns are likely a result of abiotic factors, differences in uptake pathways between life stages and the rate of excretion. Future laboratory studies are required to understand the factors influencing the aqueous and dietary uptake of nonessential trace elements in the early life stages of Atlantic horseshoe crabs.
-
Maternal transfer of trace elements in the Atlantic horseshoe crab (Limulus polyphemus)
Ecotoxicology, 2017Co-Authors: Aaron K. Bakker, Jessica Dutton, Matthew Sclafani, Nicholas SantangeloAbstract:The maternal transfer of trace elements is a process by which offspring may accumulate trace elements from their maternal parent. Although maternal transfer has been assessed in many vertebrates, there is little understanding of this process in invertebrate species. This study investigated the maternal transfer of 13 trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, and Zn) in Atlantic horseshoe crab (Limulus polyphemus ) eggs and compared concentrations to those in adult leg and gill tissue. For the majority of individuals, all trace elements were transferred, with the exception of Cr, from the female to the eggs. The greatest concentrations on average transferred to egg tissue were Zn (140 µg/g), Cu (47.8 µg/g), and Fe (38.6 µg/g) for essential elements and As (10.9 µg/g) and Ag (1.23 µg/g) for nonessential elements. For elements that were maternally transferred, correlation analyses were run to assess if the concentration in the eggs were similar to that of adult tissue that is completely internalized (leg) or a boundary to the external environment (gill). Positive correlations between egg and leg tissue were found for As, Hg, Se, Mn, Pb, and Ni. Mercury, Mn, Ni, and Se were the only elements correlated between egg and gill tissue. Although, many trace elements were in low concentration in the eggs, we speculate that the higher transfer of essential elements is related to their potential benefit during early development versus nonessential trace elements, which are known to be toxic. We conclude that maternal transfer as a source of trace elements to horseshoe crabs should not be overlooked and warrants further investigation.
-
environmental exposure of atlantic horseshoe crab Limulus polyphemus early life stages to essential trace elements
Science of The Total Environment, 2016Co-Authors: Aaron K. Bakker, Jessica Dutton, Matthew Sclafani, Nicholas SantangeloAbstract:This study investigated the accumulation Co, Cu, Fe, Mn, Ni, Se, and Zn in Atlantic horseshoe crab (Limulus polyphemus) early life stages (egg, embryo and larvae) and compared the concentrations to the concentration of each element in sediment, pore water and overlying water for 5 sites across Long Island, NY. For the majority of the sites, all essential trace elements accumulated in the embryos and larvae. However, many of the embryos and larvae at specific sites presented different concentration patterns which had no apparent relationship with the local habitat sediment and water values. Generally, Cu, Fe, and Se sequentially increased from egg stage through larval stages for the majority of sites, while Co, Mn, and Ni only did for a few sites. Zinc also showed an increase across sites from embryo to larval stage, however was the only one to show a decrease in concentration from egg to embryo stage at all sites. Interestingly, Mn at Manhasset Bay presented embryo and larval stages to be 50 fold greater than all other sites while the egg stage showed similar values to other sites; this high degree of uptake could be due to a high concentration in the overlying water. All essential trace elements can be accumulated from the environment but greater concentrations may be influenced by abiotic factors and the predominant uptake route (aqueous versus diet) at each life stage. Future laboratory experiments are required to investigate factors that influence essential trace element accumulation and loss in horseshoe crab early life stages.
Mark L. Botton - One of the best experts on this subject based on the ideXlab platform.
-
Effects of copper and cadmium on development and superoxide dismutase levels in horseshoe crab (Limulus polyphemus) embryos
SpringerPlus, 2015Co-Authors: Mary G. Hamilton, Christopher Esposito, Mia Malin, Lucas Cusumano, Mark L. BottonAbstract:Pollution by metals may adversely affect organisms through the generation of reactive oxygen species (ROS). In this study, we examined the sublethal effects of two metals, copper and cadmium, on horseshoe crab ( Limulus polyphemus ) embryos. Exposure to copper or cadmium at concentrations of 0.01–10 mg/L for periods of 4, 8, 16 and 24 h had minimal effect on embryo survival except at 100 mg/L Cu. However, metal-exposed embryos took significantly longer to hatch into first instar (“trilobite”) larvae than seawater controls. Levels of superoxide dismutase (SOD), believed to be important in the response to oxidative stress, were determined by Western blotting. Both the Cu/Zn and Mn cofactor forms of SOD tended to be somewhat elevated in metal-exposed embryos, but the increases were neither dose nor time-dependent. Likewise, SOD enzymatic activity showed no significant differences comparing embryos exposed to metals with seawater controls. We conclude that the protective role of SOD’s against ROS produced in response to metal exposure appears to be limited in horseshoe crab embryos, at least under our experimental conditions.
-
Physiological responses of horseshoe crab (Limulus polyphemus) embryos to osmotic stress and a possible role for stress proteins (HSPs)
Marine Biology, 2011Co-Authors: Morgan P. Greene, Mary G. Hamilton, Mark L. BottonAbstract:We tested the effects of osmotic stress on survival, developmental rate, and level of HSPs on American horseshoe crab ( Limulus polyphemus ) embryos. Animals were maintained in the laboratory at an ambient salinity of 20 ppt and then exposed to 4-h osmotic shocks at salinities of 10, 30, 40, 50, and 60 ppt, with a control group at 20 ppt. Horseshoe crab embryos had 100% developmental success (defined as individuals reaching the first instar or trilobite larval stage) at all salinities. However, osmotic stresses, especially hyperosmotic conditions, slowed the rate of development. Embryos subjected to osmotic stress showed higher levels of HSP70 and HSP90 than control animals kept at a salinity of 20 ppt. HSPs are of value to horseshoe crab embryos in surviving the fluctuating salinities that are typical of estuarine beach habitats.
-
Temporal and spatial patterns of organic carbon are linked to egg deposition by beach spawning horseshoe crabs (Limulus polyphemus)
Hydrobiologia, 2011Co-Authors: Mark L. Botton, Robert E LovelandAbstract:The spring spawning by the American horseshoe crab ( Limulus polyphemus L.) results in temporally and spatially discrete inputs of eggs onto sandy beaches in Delaware Bay, USA. We tested the hypothesis that seasonal patterns of sediment organic carbon on Delaware Bay beaches is linked to this pulsed input of horseshoe crab eggs. At a location with minimal horseshoe crab spawning activity (Higbee Beach), there was little seasonal variation in sediment organic carbon, no distinction between organic carbon levels as a function of shoreline position or sediment depth, and no significant correlation between the abundance of crab eggs and percent organic carbon. Conversely, at a prime horseshoe crab spawning habitat (North Beach), organic carbon levels were seasonally pulsed and were correlated with egg abundance. Moreover, the strongest evidence of seasonality was seen at the middle foreshore location at the 15–20 cm depth, consistent with the highest input of horseshoe crab eggs. Although some of the organic carbon contributed by horseshoe crab eggs in May–June leaves the beach in the form of hatched larvae later in the year, there is a net input of organic carbon to the system in the form of unfertilized and/or dead eggs, egg membranes, and embryonic molts. We suggest that the inputs of eggs from horseshoe crabs and other beach spawning animals, such as grunion and capelin, make significant contributions to the energy budget of sandy beaches.
-
Horseshoe crabs (Limulus polyphemus) in an urban estuary (Jamaica Bay, New York) and the potential for ecological restoration
Estuaries and Coasts, 2006Co-Authors: Mark L. Botton, Robert E Loveland, John T. Tanacredi, Tomio ItowAbstract:We assessed the suitability of intertidal habitats for spawning by horseshoe crabs ( Limulus polyphemus ) at 12 proposed restoration sites identified by the United States Army Corps of Engineers along the shore of Jamaica Bay, a highly developed estuary in New York City. Based on beach geomorphology, we chose to quantify horseshoe crab activity at five of the sites during the May–July 2000 breeding season. Horseshoe crabs spawned intensively on small patches of suitable sand within larger areas of eroding shoreline with bulkheads and rubble fill. Small areas of sand behind grounded barges at Brant Point and Dubos Point had densities of over 100,000 eggs m^−2, which was equal to or greater than the egg densities on longer, more natural appearing beaches at Spring Creek and Dead Horse Bay, or at a sand spit at Bayswater State Park. There were no significant differences in the percentage of Jamaica Bay horseshoe crab eggs that completed development when cultured using water from Jamaica Bay or lower Delaware Bay, a less polluted location. Only 1% of the embryos from Jamaica Bay exhibited developmental anomalies, a frequency comparable to a previously studied population from Delaware Bay. We suggest that the distribution and abundance of horseshoe crabs at our study areas in Jamaica Bay is presently limited by the availability of suitable shoreline for breeding, rather than by water quality. Restoration efforts that increase the amount of sandy beach in this urban estuary have a good likelihood of benefiting horseshoe crabs and providing additional value to migrating shorebirds that use horseshoe crab eggs as food.
-
distribution abundance and survivorship of young of the year in a commercially exploited population of horseshoe crabs Limulus polyphemus
Marine Ecology Progress Series, 2003Co-Authors: Mark L. Botton, Robert E Loveland, Athena TiwariAbstract:Horseshoe crab Limulus polyphemus eggs are laid on sandy estuarine beaches, and subsequently develop into first instar (trilobite) larvae that emerge into the plankton before settle- ment. To obtain estimates of early survival, we collected data on the densities of trilobite larvae within intertidal sediments on a beach in Delaware Bay, New Jersey, and the densities of post-settle- ment juveniles, through the first 4 instar stages, on the adjacent tidal flats. Over the course of the spawning season in 1999, there were some 761 000 live trilobites produced within a 1 × 3 m band of intertidal beach. Losses (mortality + emigration) were highest during the brief planktonic phase or shortly after settlement to the benthos; we estimated that about 97.5% of the live trilobites on the beaches were lost during their transition to epibenthic trilobites on the intertidal flats. Newly settled horseshoe crab juveniles were not dependent on a specific sediment type, but tended to be more abundant close to shore. After settlement, there was about a log-fold decrease in juvenile density with each molt from the second through the fourth instar. Overall, only about 3 larvae per 100 000 re- mained as fourth instar juveniles on the tidal flats at the end of their first summer. Our ability to ex- trapolate future adult year-class strengths based on young-of-the-year densities is limited, because 9 to 10 yr are required for horseshoe crabs to reach sexual maturity.
Jane H Brockmann - One of the best experts on this subject based on the ideXlab platform.
-
conservation status of the american horseshoe crab Limulus polyphemus a regional assessment
Reviews in Fish Biology and Fisheries, 2017Co-Authors: David R Smith, Jane H Brockmann, Tim L King, Mark A Beekey, Michael J Millard, Jaime ZaldivarraeAbstract:Horseshoe crabs have persisted for more than 200 million years, and fossil forms date to 450 million years ago. The American horseshoe crab (Limulus polyphemus), one of four extant horseshoe crab species, is found along the Atlantic coastline of North America ranging from Alabama to Maine, USA with another distinct population on the coasts of Campeche, Yucatan and Quintana Roo in the Yucatan Peninsula, Mexico. Although the American horseshoe crab tolerates broad environmental conditions, exploitation and habitat loss threaten the species. We assessed the conservation status of the American horseshoe crab by comprehensively reviewing available scientific information on its range, life history, genetic structure, population trends and analyses, major threats, and conservation. We structured the status assessment by six genetically-informed regions and accounted for sub-regional differences in environmental conditions, threats, and management. The transnational regions are Gulf of Maine (USA), Mid-Atlantic (USA), Southeast (USA), Florida Atlantic (USA), Northeast Gulf of Mexico (USA), and Yucatan Peninsula (Mexico). Our conclusion is that the American horseshoe crab species is vulnerable to local extirpation and that the degree and extent of risk vary among and within the regions. The risk is elevated in the Gulf of Maine region due to limited and fragmented habitat. The populations of horseshoe crabs in the Mid-Atlantic region are stable in the Delaware Bay area, and regulatory controls are in place, but the risk is elevated in the New England area as evidenced by continuing declines understood to be caused by over-harvest. The populations of horseshoe crabs in the Southeast region are stable or increasing. The populations of horseshoe crabs in the Florida Atlantic region show mixed trends among areas, and continuing population reductions at the embayment level have poorly understood causes. Within the Northeast Gulf of Mexico, causes of population trends are poorly understood and currently there is no active management of horseshoe crabs. Horseshoe crabs within Mexico have conservation protection based on limited and fragmented habitat and geographic isolation from other regions, but elevated risk applies to the horseshoe crabs in the Yucatan Peninsula region until sufficient data can confirm population stability. Future species status throughout its range will depend on the effectiveness of conservation to mitigate habitat loss and manage for sustainable harvest among and within regions.
-
between population differences in multi stressor tolerance during embryo development in the american horseshoe crab Limulus polyphemus
Estuaries and Coasts, 2017Co-Authors: Jane H Brockmann, Christina M Vasquez, David JulianAbstract:The American horseshoe crab, Limulus polyphemus, is found along the Atlantic and Gulf of Mexico coasts in genetically isolated populations. Eggs are laid in shoreline beaches that expose developing embryos to combinations of environmental stressors. Whether populations of L. polyphemus differ in multi-stressor tolerance had never been tested. We assessed the multi-stressor tolerance of L. polyphemus embryos from a population in Delaware Bay (DE) and determined whether these differed from the multi-stressor tolerance of embryos from a more southerly Florida Gulf Coast (FGC) population. We monitored the field sediment temperatures and determined multi-stressor tolerance of DE embryos, then compared these to published data for FGC embryos. For multi-stressor tolerance, we assessed development success of embryos in 2-week exposures to 36 full-factorial combinations of temperature (20, 25, 30, 35 °C), salinity (5, 15, and 34 ppt), and ambient O2 (5, 13, and 21% O2), followed by 2 weeks in recovery conditions. Sediment temperatures in the DE site ranged from 9.5 to 46 °C, with extended periods exceeding 35 °C. Development success was similar between the DE and FGC populations in 14 of 26 multi-stressor combinations. The DE embryos were generally more successful in conditions that included high temperature or moderate hyposalinity, whereas the FGC embryos were generally more successful in conditions that included extreme hyposalinity. This suggests that although multi-stressor tolerances are generally similar between the two populations, specific differences exist that correlate more with differences in nest microenvironment than latitude.
-
multiple stressor interactions influence embryo development rate in the american horseshoe crab Limulus polyphemus
The Journal of Experimental Biology, 2015Co-Authors: Christina M Vasquez, Jane H Brockmann, Andrea Murillo, David JulianAbstract:Fertilized eggs of the American horseshoe crab, Limulus polyphemus , are buried in shallow nests above the high tide line, where they are exposed to variations in abiotic conditions during early development. Using a multiple-stressors approach, we examined whether the rate of embryonic development is affected by exposure to combinations of three factors: temperature (25, 30 and 35°C), salinity (5, 15 and 34 ppt) and ambient O2 (5%, 13% and 21% O2). Newly fertilized eggs were incubated under 27 fully factorial stressor combinations for 14 days, then allowed to recover in control conditions (30°C, 34 ppt, 21% O2) for an additional 14 days. Growth rate was measured every 2 days throughout the experiment ( N =1289). We found that the effect of isolated stressors (high temperature, low salinity or low O2) reduced developmental success by up to 72% (low salinity), and that stressor combinations showed stronger effects and evidence of complex interactions. For example, low O2 had little effect individually but was lethal in combination with high temperature, and low temperature in isolation slightly decreased the rate of development but reduced the negative effects of low salinity and low O2. Development was delayed under exposure to low O2 but resumed upon return to control conditions after a 10 day lag. These data demonstrate that complex, synergistic interactions among abiotic stressors can substantially alter the development of a coastal invertebrate in ways that may not be predicted from the effects of the stressors in isolation.
-
nest site selection minimizes environmental stressor exposure in the american horseshoe crab Limulus polyphemus l
Journal of Experimental Marine Biology and Ecology, 2015Co-Authors: Christina M Vasquez, Sheri L. Johnson, Jane H Brockmann, David JulianAbstract:Abstract The American horseshoe crab, Limulus polyphemus, migrates to beaches at Seahorse Key, FL, on the highest-high tides to mate and deposit clutches of fertilized eggs. By nesting at high beach elevations, females may increase hatching success by minimizing exposure of the developing eggs to hypoxia and hydrogen sulfide, although at the potential added cost of increased exposure to harmful high temperatures. To test this, we took a two-fold approach: 1) we determined microclimate conditions experienced by developing horseshoe crab eggs at a nesting site on the Gulf Coast of Florida, and 2) in laboratory-rearing experiments we determined whether developmental success was affected by exposure to temperature, ambient O2 and sulfide conditions modeled on values from potential nesting sites. We found that most horseshoe crabs nested in the high and extreme-high tidal height zones above the high tide line. These high-tidal areas were characterized by normoxia, temperatures exceeding 35 °C, and minimal exposure to hydrogen sulfide. When fertilized eggs and larvae were exposed to similar “control” conditions in the laboratory, eggs and larvae exhibited 80–90% developmental success. The mid-tidal height zone was characterized by temperatures exceeding 35 °C, 21–17% ambient O2, and minimal exposure to hydrogen sulfide. When exposed to similar mid-tidal conditions in the laboratory, development success was equivalent to eggs exposed to control conditions. In contrast, the low tidal height zone was characterized by temperatures never exceeding 35 °C, ambient O2 as low as 5.9%, and significantly greater exposure to hydrogen sulfide. In the laboratory, exposure to conditions similar to low-tidal zone resulted in developmental success that was reduced by up to 25% compared to the eggs and larvae exposed to control conditions. We conclude that horseshoe crabs choose nesting sites that maximize developmental success by avoiding sites containing hypoxia and hydrogen sulfide, although this increases exposure to high temperature.
-
mating tactics of the american horseshoe crab Limulus polyphemus
2015Co-Authors: Jane H Brockmann, Sheri L. Johnson, Matthew D Smith, Daniel A. SassonAbstract:The reproductive behavior of horseshoe crabs (Limulus polyphemus) is easily observed, yet until recently, little was known about their unusual mating habits. Fertilization is external and occurs beneath the female as her eggs are being laid in the sand. Spawning is often synchronized to the highest spring tides of the year, so the time available for breeding is limited. Males have alternative mating tactics, some search and pair with a female offshore and migrate inshore to spawn, while others search onshore for nesting pairs and engage in sperm competition in group spawning. Females also have alternative tactics such that some spawn with a single attached male and others spawn with multiple males, which results in multiple male paternity of their offspring. Both male and female tactics are condition and context-dependent and are affected by breeding density, operational sex ratio, and the interplay between male and female tactics. To better understand horseshoe crab reproductive behavior, we review studies conducted during the past 25 years in one Gulf of Mexico population in northern Florida at Seahorse Key. We discuss the costs, benefits, and tradeoffs of alternative tactics for males and females. We synthesize the recent literature on mating tactics, resolve some conflicting results, and point to the future by identifying the questions that remain.
Sheri L. Johnson - One of the best experts on this subject based on the ideXlab platform.
-
Reproductive tactics and mating contexts affect sperm traits in horseshoe crabs (Limulus polyphemus)
Behavioral Ecology and Sociobiology, 2015Co-Authors: Daniel A. Sasson, Sheri L. Johnson, H. Jane BrockmannAbstract:In systems with male alternative reproductive tactics, discrete behavioral patterns often lead to unequal levels of sperm competition across tactics. In many of these systems, the disadvantaged tactic shows adaptations to sperm traits that increase the competitive ability of its sperm. However, many studies have found that not all sperm traits differ across tactics, and in some systems no sperm trait adaptations are found. Why some systems and some sperm traits display tactic-specific differences and others do not is not always clear. Here, we investigate three sperm traits—ejaculate size, sperm concentration, and sperm velocity—in the American horseshoe crab, Limulus polyphemus , a system where males have condition-dependent reproductive tactics and females influence the amount of sperm competition males face during spawning. Contrary to our predictions that the disadvantaged tactic would show sperm trait adaptations, we found that horseshoe crabs of the tactic that faces the least amount of sperm competition had more concentrated sperm than the males of the other tactics. We propose a number of hypotheses to explain this result and suggest that future studies of alternative reproductive tactics might benefit from considering the role of females in influencing tactic-specific sperm trait adaptations.
-
nest site selection minimizes environmental stressor exposure in the american horseshoe crab Limulus polyphemus l
Journal of Experimental Marine Biology and Ecology, 2015Co-Authors: Christina M Vasquez, Sheri L. Johnson, Jane H Brockmann, David JulianAbstract:Abstract The American horseshoe crab, Limulus polyphemus, migrates to beaches at Seahorse Key, FL, on the highest-high tides to mate and deposit clutches of fertilized eggs. By nesting at high beach elevations, females may increase hatching success by minimizing exposure of the developing eggs to hypoxia and hydrogen sulfide, although at the potential added cost of increased exposure to harmful high temperatures. To test this, we took a two-fold approach: 1) we determined microclimate conditions experienced by developing horseshoe crab eggs at a nesting site on the Gulf Coast of Florida, and 2) in laboratory-rearing experiments we determined whether developmental success was affected by exposure to temperature, ambient O2 and sulfide conditions modeled on values from potential nesting sites. We found that most horseshoe crabs nested in the high and extreme-high tidal height zones above the high tide line. These high-tidal areas were characterized by normoxia, temperatures exceeding 35 °C, and minimal exposure to hydrogen sulfide. When fertilized eggs and larvae were exposed to similar “control” conditions in the laboratory, eggs and larvae exhibited 80–90% developmental success. The mid-tidal height zone was characterized by temperatures exceeding 35 °C, 21–17% ambient O2, and minimal exposure to hydrogen sulfide. When exposed to similar mid-tidal conditions in the laboratory, development success was equivalent to eggs exposed to control conditions. In contrast, the low tidal height zone was characterized by temperatures never exceeding 35 °C, ambient O2 as low as 5.9%, and significantly greater exposure to hydrogen sulfide. In the laboratory, exposure to conditions similar to low-tidal zone resulted in developmental success that was reduced by up to 25% compared to the eggs and larvae exposed to control conditions. We conclude that horseshoe crabs choose nesting sites that maximize developmental success by avoiding sites containing hypoxia and hydrogen sulfide, although this increases exposure to high temperature.
-
mating tactics of the american horseshoe crab Limulus polyphemus
2015Co-Authors: Jane H Brockmann, Sheri L. Johnson, Matthew D Smith, Daniel A. SassonAbstract:The reproductive behavior of horseshoe crabs (Limulus polyphemus) is easily observed, yet until recently, little was known about their unusual mating habits. Fertilization is external and occurs beneath the female as her eggs are being laid in the sand. Spawning is often synchronized to the highest spring tides of the year, so the time available for breeding is limited. Males have alternative mating tactics, some search and pair with a female offshore and migrate inshore to spawn, while others search onshore for nesting pairs and engage in sperm competition in group spawning. Females also have alternative tactics such that some spawn with a single attached male and others spawn with multiple males, which results in multiple male paternity of their offspring. Both male and female tactics are condition and context-dependent and are affected by breeding density, operational sex ratio, and the interplay between male and female tactics. To better understand horseshoe crab reproductive behavior, we review studies conducted during the past 25 years in one Gulf of Mexico population in northern Florida at Seahorse Key. We discuss the costs, benefits, and tradeoffs of alternative tactics for males and females. We synthesize the recent literature on mating tactics, resolve some conflicting results, and point to the future by identifying the questions that remain.
-
a long term study of spawning activity in a florida gulf coast population of horseshoe crabs Limulus polyphemus
Estuaries and Coasts, 2011Co-Authors: Jane H Brockmann, Sheri L. JohnsonAbstract:Populations of the American horseshoe crab (Limulus polyphemus) differ in broad areas of their biology. We observed a non-harvested, marked Florida Gulf coast population during their spring spawning (March–May) in 11 years across a 17-year period (1992–2009). Long-term changes occurred in the number of spawning pairs: the population was stable from 1992 to 2000 but increased markedly after 2000. Short-term variation in numbers of spawning pairs, unpaired females, unpaired males, and operational sex ratios was explained by changes over the season and during each week of spring tides and by differences in actual (not predicted) maximum high tide height. Wind direction strongly affected tidal inundation and the number of spawning horseshoe crabs. Tagging individuals revealed that females returned to the nesting beach less often than males and most females were re-sighted only within 1 week of spring tides. No animals were seen across more than 6 years. Implications for management are discussed.
Christopher C. Chabot - One of the best experts on this subject based on the ideXlab platform.
-
Local tidal regime dictates plasticity of expression of locomotor activity rhythms of American horseshoe crabs, Limulus polyphemus
Marine Biology, 2017Co-Authors: Rebecca L Anderson, Winsor H. Watson, Christopher C. ChabotAbstract:While horseshoe crabs Limulus polyphemus from regions with two daily tides express endogenous circatidal (~12.4 h) activity rhythms, much less is known about locomotor rhythm expression in horseshoe crabs from other tidal regimes. This study investigated whether horseshoe crabs (1) always express activity rhythms consistent with their natural tides and (2) can alter activity rhythm expression in response to novel tide cycles. Activity rhythms of L. polyphemus from environments with two daily tides (Gulf of Maine, 43°6′N/70°52′W, and Massachusetts, 41°32′N/70°40′W), one dominant daily tide (Apalachee Bay, Florida, 29°58′N/84°20′W), and microtides (Indian River Lagoon, Florida, 28°5′N/80°35′W) were recorded in 2011–2013 during three artificial tide conditions: no tides, a 12.4-h tidal cycle, and a 24.8-h tidal cycle. Interestingly, L. polyphemus from the microtidal site ( n = 7) appeared “plastic” in their responses; they were able to express both bimodal and unimodal rhythms in response to different tide cycles. In contrast, the other two populations exhibited more fixed responses: regardless of the tides, they were exposed to, horseshoe crabs from areas with one dominant daily tide ( n = 18) consistently expressed unimodal rhythms, while those from areas with two daily tides ( n = 28) generally expressed bimodal rhythms. Rhythms expressed by L. polyphemus thus appear to be a function of endogenous clocks, the tidal cues to which individuals are exposed, and tidal cues that individuals experience throughout ontogeny.
-
the draft genome and transcriptome of the atlantic horseshoe crab Limulus polyphemus
Comparative and Functional Genomics, 2017Co-Authors: Stephen Simpson, Winsor H. Watson, Jordan Ramsdell, Christopher C. ChabotAbstract:The horseshoe crab, Limulus polyphemus, exhibits robust circadian and circatidal rhythms, but little is known about the molecular mechanisms underlying those rhythms. In this study, horseshoe crabs were collected during the day and night as well as high and low tides, and their muscle and central nervous system tissues were processed for genome and transcriptome sequencing, respectively. The genome assembly resulted in contigs with N50 of 4,736, while the transcriptome assembly resulted in contigs and N50 of 3,497. Analysis of functional completeness by the identification of putative universal orthologs suggests that the transcriptome has three times more total expected orthologs than the genome. Interestingly, RNA-Seq analysis indicated no statistically significant changes in expression level for any circadian core or accessory gene, but there was significant cycling of several noncircadian transcripts. Overall, these assemblies provide a resource to investigate the Limulus clock systems and provide a large dataset for further exploration into the taxonomy and biology of the Atlantic horseshoe crab.
-
influence of environmental factors on spawning of the american horseshoe crab Limulus polyphemus in the great bay estuary new hampshire usa
Estuaries and Coasts, 2016Co-Authors: Helen Cheng, Christopher C. Chabot, Winsor H. WatsonAbstract:The Great Bay Estuary, New Hampshire, USA is near the northern distribution limit of the American horseshoe crab (Limulus polyphemus). This estuary has few ideal beaches for spawning, yet it supports a modest population of horseshoe crabs. There is no organized monitoring program in the Great Bay Estuary, so it is unclear when and where spawning occurs. In this 2-year study (May through June, 2012 and 2013), >5,000 adult horseshoe crabs were counted at four sites in the estuary. The greatest densities of horseshoe crabs were observed at Great Bay sites in the upper, warmer reaches of the estuary. Peaks of spawning activity were not strongly correlated with the times of the new or full moons, and similar numbers of horseshoe crabs were observed mating during daytime and nighttime high tides. While many environmental factors are likely to influence the temporal and spatial patterns of spawning in this estuary, temperature appears to have the most profound impact.
-
Circalunidian clocks control tidal rhythms of locomotion in the American horseshoe crab, Limulus polyphemus.
Marine and freshwater behaviour and physiology, 2016Co-Authors: Christopher C. Chabot, Nicole Christine Ramberg-pihl, Winsor H. WatsonAbstract:AbstractWhile many intertidal animals exhibit circatidal rhythms, the nature of the underlying endogenous clocks that control these rhythms has been controversial. In this study American horseshoe crabs, Limulus polyphemus, were used to test the circalunidian hypothesis by exposing them to four different tidal regimes. Overall, the results obtained support the circalunidian hypothesis: each of the twice-daily rhythms of activity appears to be controlled by a separate clock, each with an endogenous period of approximately 24.8 h. First, spontaneous “skipping” of one of the daily bouts was observed under several different conditions. Second, the presence of two bouts of activity/day, with different periods, was observed. Lastly, we were able to separately synchronize bouts of activity to two artificial tidal regimes with different periods. These results, taken together, argue in favor of two separate circalunidian clocks in Limulus, each of which controls one of the two bouts of their daily tidal activity r...
-
sublethal behavioral and physiological effects of the biomedical bleeding process on the american horseshoe crab Limulus polyphemus
The Biological Bulletin, 2013Co-Authors: Rebecca L Anderson, Winsor H. Watson, Christopher C. ChabotAbstract:The hemolymph of the American horseshoe crab, Limulus polyphemus, is harvested from over 500,000 animals annually to produce Limulus amebocyte lysate (LAL), a medically important product used to detect pathogenic bacteria. Declining abundance of spawning Limulus females in heavily harvested regions suggests deleterious effects of this activity, and while mortality rates of the harvest process are known to be 10%-30%, sublethal behavioral and physiological effects are not known. In this study, we determined the impact of the harvest process on locomotion and hemocyanin levels of 28 female horseshoe crabs. While mortality rates after bleeding (18%) were similar to previous studies, we found significant decreases in the linear and angular velocity of freely moving animals, as well as changes in their activity levels and expression of circatidal behavioral rhythms. Further, we found reductions in hemocyanin levels, which may alter immune function and cuticle integrity. These previously unrecognized behavioral and physiological deficits suggest that the harvest of LAL may decrease female fitness, and thus may contribute to the current population decline.