Search

While several studies have documented the large-scale, seasonal movements of horseshoe crabs, little is known about their fine-scale, daily movement patterns. In this study we used a fixed array ultrasonic telemetry system to track the movements of 12 male and 16 female horseshoe crabs in the Great Bay estuary, New Hampshire. Data were obtained during the mating season, as well as during the remainder of the summer and fall, in the years 2005-2008. During the mating season animals were often, but not always, active during the high tides when they were approaching and leaving the spawning beaches. On average, both males and females approached mating beaches during 33% of the high tides they experienced and they most often made the transition from being inactive to active during the last two hours of an incoming tide. From April-October horseshoe crabs were significantly more active during high tide periods vs low tide periods, with no clear preference for diurnal vs nocturnal activity. After the mating season ended horseshoe crabs continued to move into shallower water at high tide and then return to deeper water at low tide. Observations by SCUBA divers suggest that during these excursions into the mudflats horseshoe crabs were digging pits in the sediment while foraging for food. Thus, the tidal rhythm of activity that has been so well documented during the mating season probably persists into the fall, and primarily involves foraging activities. [ABSTRACT FROM AUTHOR]

Adult horseshoe crabs Limulus polyphemus have long served as models for the study of vision in marine arthropods. Yet, little is known about the ability of early life history stages to detect and respond to visual cues. We examined the visually directed movements of larvae and first stage juveniles to horizons containing dark visual targets of different sizes. The study tested the hypotheses that (1) larval and juvenile crabs can detect and respond to visual targets and (2) the direction of orientation varies with the presence of chemical cues associated with settlement habitats. Orientation of larval and juvenile crabs to rectangles subtending angles from 30-330° was tested in a circular arena containing water that either lacked estuarine chemical cues (offshore water) or contained odors from aquatic vegetation or known predators. In the absence of chemical odors, larvae oriented toward and juveniles moved away from dark horizons subtending angles > 60°. When placed in water containing chemical odors from potential nursery habitats, including the seagrasses Halodule wrightii and Syringodium filiforme, crabs reversed their direction of orientation relative to their responses in offshore water. Odors from two known predators, the mummichug Fundulus grandis and blue crab Callinectes sapidus, had no affect on the orientation of larvae. Yet, juveniles responded to both odors by moving toward the visual target. Results support the hypothesis that the visual orientation of larval and juvenile horseshoe crabs changes upon exposure to habitat and predator cues and that the direction of the response undergoes an ontogenetic shift following metamorphosis. [ABSTRACT FROM AUTHOR]

To study horseshoe crab Limulus polyphemus spawning behavior and migration over a large-spatial extent (>100 km), we arrayed fixed station radio receivers throughout Delaware Bay and deployed radio transmitters and archival tags on adult horseshoe crabs prior to their spawning season. We tagged and released 160 females and 60 males in 2004 and 217 females in 2005. The array covered approximately 140 km of shoreline. Recapture rates were >70% with multi-year recaptures. We categorized adult age by carapace wear. Older females tended to spawn earlier in the season and more frequently than young females, but those tendencies were more apparent in 2004 when spawning overall occurred earlier than in 2005 when spawning was delayed possibly due to decreased water temperatures. Timing of initial spawning within a year was correlated with water temperature. After adjusting for day of first spring tide, the day of first spawning was 4 days earlier for every 1 degree (°C) rise in mean daily water temperature in May. Seventy nine % of spawning occurred during nighttime high tides. Fifty five % of spawning occurred within 3 d of a spring tide, which was slightly higher than the 47% expected if spawning was uniformly distributed regardless of tidal cycle. Within the same spawning season, males and females were observed spawning or intertidally resting at more than one beach separated by >5 km. Between years, most (77%) did not return to spawn at the same beach. Probability of stranding was strongly age dependent for males and females with older adults experiencing higher stranding rates. Horseshoe crabs staging in the shallow waters east of the channel spawned exclusively along the eastern (NJ) shoreline, but those staging west of the channel spawned throughout the bay. Overall, several insights emerged from the use of radio telemetry, which advances our understanding of horseshoe crab ecology and will be useful in conserving the Delaware Bay horseshoe crab population and habitats. [ABSTRACT FROM AUTHOR]

Abstract: The scanning electron microscope (SEM) was used to study the development of the opisthosomal appendages and book gills of the horseshoe crab, Limulus polyphemus. Later embryonic stages were examined as well as the first and second instars. The observations are compared with a much earlier light microscopic description of book gill development in the horseshoe crab and with book lung development in scorpion embryos and first and second instars in a recent study with SEM. After the third embryonic molt in the horseshoe crab, the opisthosomal appendages are of sufficient size so they could be fractured or dissected open so internal cells and other structures could be examined. The opisthosomal appendages and book gill lamellae of first and second instars were also opened. The observations support the earlier histological report that the gill lamellae are a hypodermal outgrowth from the posterior surface of the preceding branchial appendages. The genital operculum, branchial appendages and gill lamellae are very thin and consist of external cuticle, hypodermis and space holders. The latter help hold the cuticle walls in place so hemolymph can flow through the narrow channels. The space holders are formed from cell processes that extend into the lumen from the hypodermis just inside the external cuticle. In the recent SEM study in scorpion embryos and in some histological investigations in spider embryos, the book lung lamellae are formed by alignment of cells from an invaginated sac or mass of cells. This clearly differs from the mode of formation of gill lamellae as observed in this and earlier investigations. These reports of differences in embryology refine but do not preclude hypotheses about book gill/book lung homology since addition, deletion or modification of ancestral features often occur for the benefit of the embryos and larvae. [Copyright &y& Elsevier]

Populations of the American horseshoe crab, Limulus polyphemus, have declined, but neither the causes nor the magnitude are fully understood. In order to evaluate historic demography, variation at 12 microsatellite DNA loci surveyed in 1218 L. polyphemus sampled from 28 localities was analysed with Bayesian coalescent-based methods. The analysis showed strong declines in population sizes throughout the species' distribution except in the geographically isolated southern-most population in Mexico, where a strong increase in population size was inferred. Analyses suggested that demographic changes in the core of the distribution occurred in association with the recolonization after the Ice Age and also by anthropogenic effects, such as the past overharvest of the species for fertilizer or the current use of the animals as bait for American eel ( Anguilla rostrata) and whelk ( Busycon spp.) fisheries. This study highlights the importance of considering both climatic changes and anthropogenic effects in efforts to understand population dynamics-a topic which is highly relevant in the ongoing assessments of the effects of climate change and overharvest. [ABSTRACT FROM AUTHOR]

Horseshoe crab haemolymph contains a single type of cells, granular haemocytes, which are extremely sensitive to bacterial lipopolysaccharides (LPS) and lead to haemolymph coagulation. Sadaaki Iwanaga isolated protease zymogens from the haemocytes and reconstituted LPS and β-1,3-d-glucans-mediated haemolymph coagulation. This led to the first discovery of a proteolytic cascade triggered by pathogen-associated molecular patterns, an important milestone for studies on invertebrate innate immunity. Moreover, he separated components derived from haemocyte granules and haemolymph plasma, and consequently identified unique defense molecules, such as lectins, serpins, cystatins, antimicrobial substances and substrates for transglutaminase. Through steady and persistent studies on the horseshoe crab host defense system, he made great progress in the field. Now we know that LPS-induced haemocyte exocytosis leads not only to coagulation but also activates a sophisticated immune response network that coordinately induces pathogen recognition, elimination and wound healing. [ABSTRACT FROM PUBLISHER]

Horseshoe crabs (Limulus polyphemus) are bled for biomedical purposes to produce Limulus Amebocyte Lysate (LAL), a valuable material used to detect endotoxins in medical devices and implants. Previous studies generally found mortality from the bleeding process of 5-15% with one study reporting 29% for females; the 15% value is now used for management purposes. However, most of these studies looked only at males, did not mimic handling practices typical of the biomedical facility in Massachusetts, or harvested females after the spawning season when much of the actual biomedical harvest occurs. Female mortality is of particular concern because they have greater importance than males for population dynamics, are preferentially harvested, and are more likely to be physiologically stressed than males because of energy outlay for egg production. We examined the mortality of unbled female horseshoe crabs versus that of crabs bled by the local biomedical company and either returned directly to water, or held overnight as is the current practice. Mortality of Control (unbled) crabs was low (3%) and differed significantly (p < 0.001) from that of either bled group (22.5% and 29.8% mortality, respectively); the two bled groups did not differ significantly from each other (p = 0.31). Mortality rates in bled treatment groups were double those used in current management of the biomedical fishery. The bait and biomedical fisheries are managed differently because biomedical is considered a low-mortality “catch and release” fishery. States and interstate management agencies may want to re-examine policies surrounding biomedical horseshoe crab harvest based on these results. [ABSTRACT FROM AUTHOR]

The article presents a study which compared the amount of shorebird sign in quadrats centered on Horshoe Crab nest depressions with the amount of sign in paired beach areas without Horshoe crab nests. It was found that Horshoe Crab nest depressions had more pecks, probes, and digit marks and had a greater coverage by shorebird sign than paired beach plots without Horshoe Crab nests. Horshoe crab egg monitoring estimates indicate egg abundance per beach.

Mabel Boyden was a biologist, active in the field of immunochemical research and also a custodian of the Serological Museum at Rutgers University between 1948 and 1974. Her recollection of a trip to obtain the blood of the horseshoe crab is revealing: it contains figures of speech that give a glimpse into the immunological discourse of the mid-1960s; it shows how her thinking was torn between different ways of doing biology; and it offers an insight into the transition of biology into the modern, molecular era. [Copyright &y& Elsevier]

The central coast of Tamil Nadu, Andaman and Nicobar Islands, along with other regions, was severely hit by the tsunami on 26 December 2004. A strange spawning behaviour of the Indian horseshoe crabs (Tachypleus gigas, Muller) was observed after the tsunami disturbance. Along the northeast coast of India, the horseshoe crabs normally migrate towards the shore in large numbers coinciding with the tidal height and grain size of the sediment and spawn in nests made in sand. The spawning behaviour was normal until November 2004 and throughout that period about 35 to 45 nests in 200 m2 of area of the breeding beach were examined. However, no nesting was observed from December 2004 to March 2005, i.e. after the occurrence of tsunami. The number of nests per 200 m2of area (∼82) and the number of eggs per nest (750-1000 eggs) were increased considerably when the normal conditions were restored in April 2005. The absence of spawning migration, from December 2004 to March 2005, is totally an unusual behaviour and this happened for the first time during the past several years of the study period. [ABSTRACT FROM AUTHOR]

The National Marine Fisheries Service has encouraged regional management councils to develop fisheries ecosystem plans that, among other things, identify the bycatch species within each fishery and describe each species' spatial and temporal distribution. Horseshoe crabs Limulus polyphemus have been harvested along the eastern coast of the USA since the 1800s; however, a fishery management plan was only recently created for this species, and bycatch in the horseshoe crab trawl fishery has not been quantified. We identified species likely to be caught as bycatch in the commercial fishery by using species composition data from a fishery-independent horseshoe crab trawl survey conducted in 2005 and 2006. Seventy-six taxa were caught, including 47 finfish species from 33 families. Skates (family Rajidae) comprised more than one-half of the total biomass caught, and horseshoe crabs comprised one-third of the total biomass. Catch per unit effort (kg/km towed) was greatest for little skate Leucoraja erinacea, winter skate Leucoraja ocellata, horseshoe crab, and clearnose skate Raja eglanteria. We also caught species that are currently on the World Conservation Union's Red List (e.g., Atlantic sturgeon Acipenser oxyrinchus) and unmanaged within U.S. waters (e.g., cownose ray Rhinoptera bonasus and smooth dogfish Mustelus canis). Nonmetric multidimensional scaling was used to cluster sites based on species abundance. The sites strongly clustered into two distinct groups, suggesting that species composition differs between northern and southern sites. Bottom water temperature was a significant factor in determining species composition, explaining almost 70% of the variation in species composition among sites. The results of this study provide managers with a better understanding of which nontarget populations may be affected by the horseshoe crab trawl fishery, a first step in understanding the broader ecosystem-level effects of this fishery. [ABSTRACT FROM AUTHOR]

Abstract: C-reactive protein (CRP) from the American horseshoe crab, Limulus polyphemus, exhibits complex membrane activities. Here, we describe the behavior of protein and lipid as CRP interacts with model liposomes and bacterial membranes. Limulus C-reactive protein (L-CRP) forms extended fibrilar structures that encapsulate liposomes in the presence of Ca2+. We have observed structures consistent in size and shape with these fibers bound to the surface of Gram-negative bacteria. The membranes of Limulus CRP-treated bacteria exhibit significantly different mechano-elastic properties than those of untreated bacteria. In vitro, bilayer lipids undergo a rigidification and reorganization of small domains. We suggest that these interactions reflect the protein’s role as a primary defense molecule, functioning in the entrapment and killing of potential pathogens. [Copyright &y& Elsevier]

Abstract: The serum-amyloid-P-component-like pentraxin from Limulus polyphemus, a recently discovered pentraxin species and important effector protein of the hemolymph immune system, displays two distinct doubly stacked cyclic molecular aggregations, heptameric and octameric. The refined three-dimensional structures determined by X-ray crystallography, both based on the same cDNA sequence, show that each aggregate is constructed from a similar dimer of protomers, which is repeated to make up the ring structure. The native octameric form has been refined at a resolution of 3 Å, the native heptameric form at 2.3 Å, and the phosphoethanolamine (PE)-bound octameric form at 2.7 Å. The existence of the hitherto undescribed heptameric form was confirmed by single-particle analysis using cryo-electron microscopy. In the native structures, the calcium-binding site is similar to that in human pentraxins, with two calcium ions bound in each subunit. Upon binding PE, however, each subunit binds a third calcium ion, with all three calcium ions contributing to the binding and orientation of the bound phosphate group within the ligand-binding pocket. While the phosphate is well-defined in the electron density, the ethanolamine group is poorly defined, suggesting structural and binding variabilities of this group. Although sequence homology with human serum amyloid P component is relatively low, structural homology is high, with very similar overall folds and a common affinity for PE. This is due, in part, to a “topological” equivalence of side-chain position. Identical side chains that are important in both function and fold, from different regions of the sequence in human and Limulus structures, occupy similar space within the overall subunit fold. Sequence and structure alignment, based on the refined three-dimensional structures presented here and the known horseshoe crab pentraxin sequences, suggest that adaptation and refinement of C-reactive-protein-mediated immune responses in these ancient creatures lacking antibody-based immunity are based on adaptation by gene duplication. [Copyright &y& Elsevier]

Each May, red knots (Calidris canutus rufa) congregate in Delaware Bay during their northward migration to feed on horseshoe crab eggs (Limulus polyphemus) and refuel for breeding in the Arctic. During the 1990s, the Delaware Bay harvest of horseshoe crabs for bait increased 10-fold, leading to a more than 90% decline in the availability of their eggs for knots. The proportion of knots achieving weights of more than 180 grams by 26-28 May, their main departure period, dropped from 0.6-0.8 to 0. 14-0.4 over 1997-2007. During the same period, the red knot population stopping in Delaware Bay declined by more than 75%, in part because the annual survival rate of adult knots wintering in Tierra del Fuego declined. Despite restrictions, the 2007 horseshoe crab harvest was still greater than the 1990 harvest, and no recovery of knots was detectable. We propose an adaptive management strategy with recovery goals and annual monitoring that, if adopted, will both allow red knot and horseshoe crab populations to recover and permit a sustainable harvest of horseshoe crabs. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we report the cloning, heterologous expression, and characterization of two novel astacin proteases from the chelicerate Limulus polyphemus (horseshoe crab), designated as LAST (Limulus astacin) and LAST_MAM (Limulus astacin containing a MAM domain), respectively. The expression pattern showed ubiquitous occurrence of LAST_MAM, while LAST was predominantly restricted to the eyes and brain, indicating a function in the nervous system. Both enzymes contain the characteristic metzincin-type zinc-binding region and Met turn. While LAST is made up only of the typical prodomain and astacin-like protease domain, LAST_MAM contains an additional MAM (meprin A5 protein tyrosine phosphatase μ) domain, which so far only has been found in few astacins such as the vertebrate meprin Hydra and squid enzymes, and in a number of other extracellular proteins such as A5 protein and tyrosine phosphatase μ. These gave rise to the designation MAM for this protein module. MAM domains have been shown to be responsible for protein oligomerization in meprin proteases and tyrosine phosphatase μ. Since the horseshoe crab has kept its body plan for almost half a billion years, it is therefore a privileged organism for the study of protease evolution. In this context, we could show by phylogenetic analysis that this protease is not related to the other MAM-domain-containing astacins indicating different evolutionary origins of these proteins. Moreover, we clearly demonstrated the divergent evolvement of the MAM module itself, and not only with regard to proteases. However, there are some unique functional features that are not shared by other members of this protein family. For example, LAST_MAM is the only astacin protease known so far that is active in its zymogen form, indicating that the presence of the N-terminal propeptide does not prevent proteolytic activity. [Copyright &y& Elsevier]

The article discusses the increasing prominence of reports citing the potential environmental risks associated with rising sea levels. Driven by greenhouse gas emissions, global warming and the melting of icecaps, sea-level rise has attracted the interests of governmental agencies, nongovernmental organizations, and academicians. A multiagency study involving the U.S. Environmental Protection Agency (EPA) and the U.S. Climate Change Science Program (USCCSP) discussing the encroachment of sea level onto the nation's mid-Atlantic coastline is presented. The implications of this process for creatures such as horseshoe crabs is discussed, and Delaware state biologist Stewart Michaels is quoted.

Abstract: The cDNA and deduced amino acid sequences for arginine kinase (AK) from the deep-sea clam Calyptogena kaikoi have been determined revealing an unusual two-domain (2D) structure with molecular mass of 80 kDa, twice that of normal AK. The amino acid sequences of both domains contain most of the residues thought to be required for substrate binding found in the horseshoe crab Limulus polyphemus AK, a well studied system for which several X-ray crystal structures exist. However, two highly conserved residues, D62 and R193, that form a salt bridge thereby stabilizing the substrate-bound structure have been replaced by G and N in domain 1, and G and P in domain 2, respectively. The present effort probes whether both domains of Calyptogena AK are catalytically competent. Recombinant constructs of the wild-type enzyme of both single domains, and of selected mutants of the Calyptogena AK have been expressed as fusion proteins with the maltose-binding protein. The wild-type two-domain enzyme (2D[WT]) had high AK activity (k cat =23 s− 1, average value of the two domains), and the single domain 2 (D2[WT]) showed 1.5-times higher activity (k cat =38 s− 1) than the wild-type 2D[WT]. Interestingly, the single domain 1 (D1[WT]) showed only a very low activity (k cat ∼0.016 s− 1). Introduction of a Y68A mutation in both domains virtually abolished catalytic activity. On the other hand, significant residual activity was observed (k cat =2.8 s− 1), when the Y68A mutation was introduced only into domain 2 of the two-domain enzyme. A similar mutation in domain 1 of the two-domain enzyme reduced activity to a much lower extent (k cat =11.1 s− 1). Although the domains of this “contiguous” dimeric AK each have catalytic capabilities, the presence of domain 2 strongly influences the stability and activity of domain 1. [Copyright &y& Elsevier]

In the laboratory, horseshoe crabs express a circadian rhythm of visual sensitivity as well as daily and circatidal rhythms of locomotion. The major goal of this investigation was to determine whether the circadian clock underlying changes in visual sensitivity also modulates locomotion. To address this question, we developed a method for simultaneously recording changes in visual sensitivity and locomotion. Although every animal (24) expressed consistent circadian rhythms of visual sensitivity, rhythms of locomotion were more variable: 44% expressed a tidal rhythm, 28% were most active at night, and the rest lacked statistically significant rhythms. When exposed to artificial tides, 8 of 16 animals expressed circatidal rhythms of locomotion that continued after tidal cycles were stopped. However, rhythms of visual sensitivity remained stable and showed no tendency to be influenced by the imposed tides or locomotor activity. These results indicate that horseshoe crabs possess at least two biological clocks: one circadian clock primarily used for modulating visual sensitivity, and one or more clocks that control patterns of locomotion. This arrangement allows horseshoe crabs to see quite well while mating during both daytime and nighttime high tides. [ABSTRACT FROM AUTHOR]

Limulus polyphemus, the American horseshoe crab, has an endogenous clock that drives circatidal rhythms of locomotor activity. In this study, we examined the ability of artificial tides to entrain the locomotor rhythms of Limulus in the laboratory. In experiments one and two, the activity of 16 individuals of L. polyphemus was monitored with activity boxes and "running wheels." When the crabs were exposed to artificial tides created by changes in water depth, circatidal rhythms were observed in animals exposed to 12.4-h "tidal" cycles of either water depth changes (8 of 8 animals) or inundation (7 of 8 animals). In experiment three, an additional 8 animals were exposed to water depth changes under cyclic conditions of light and dark and then monitored for 10 days with no imposed artificial tides. Most animals (5) clearly synchronized their activity to the imposed artificial tidal cycles, and 3 of these animals showed clear evidence of entrainment after the artificial tides were terminated. Overall, these results demonstrate that the endogenous tidal clock that influences locomotion in Limulus can be entrained by imposed artificial tides. In the laboratory, these tidal cues override the influence of light/dark cycles. In their natural habitat, where both tidal and photo-period inputs are typically always present, their activity rhythms are likely to be much more complex. [ABSTRACT FROM AUTHOR]

The pentraxins are a family of highly conserved plasma proteins of metazoans known to function in immune defence. The canonical members, C-reactive protein and serum amyloid P component, have been identified in arthropods and humans. Mammalian pentraxins are known to bind lipid bilayers, and a pentraxin representative from the American horseshoe crab, Limulus polyphemus, binds and permeabilizes mammalian erythrocytes. Both activities are Ca2+-dependent. Utilizing model liposomes and planar lipid bilayers, in the present study we have investigated the membrane-active properties of the three pentraxin representatives from Limulus and show that all of the Limulus pentraxins permeabilize lipid bilayers. Mechanistically, Limulus C-reactive protein forms transmembrane pores in asymmetric planar lipid bilayers that mimic the outer membrane of Gram-negative bacteria and exhibits a Ca2+-independent form of membrane binding that may be sufficient for pore formation. [ABSTRACT FROM AUTHOR]

The cuticle of the American horseshoe crab, Limulus polyphemus, is largely free of the macroscopic epibionts that rapidly colonize most solid surfaces exposed to sea water. Here, we describe a viscous surface secretion that coats the carapace of the horseshoe crab. We report methods for stimulating production of the substance, identify hemolytic and liposome-permeabilizing activities and provide a partial biochemical characterization. We propose that this secretion functions as an anti-fouling agent protecting the chitinized epithelium of the cuticle from colonization by deleterious epibionts. [ABSTRACT FROM AUTHOR]

The article discusses the pharmacokinetics of intravascular itraconazole in the American horseshoe crab (Limulus polyphemus). It features a pilot study to establish a dose and sampling for itraconazole in American horseshoe crab. Drug administration were tested on cardiac sinus. The results are discussed.

Class III unconventional myosins are critical for the normal function of auditory hair cells and the function and maintenance of photoreceptors; however, the roles of class III myosins in these sensory cells are unknown. Class III myosins are unique in that they have a kinase domain at their N-terminus; thus, they may have both signaling and motor functions. In the horseshoe crab Limulus polyphemus, enhanced phosphorylation of an abundant, photoreceptor specific class III myosin at night correlates with well-characterized circadian changes in photoreceptor structure and function. Thus, the Limulus visual system may be particularly useful for investigating the properties, modulation, and functions of a class III myosin. Previously, we showed that two sites within the actin interface of full-length Limulus myosin III expressed in baculovirus are substrates for both cyclic AMP-dependent protein kinase and autophosphorylation. In the current study, mass spectrometry was used to show that these same sites are phosphorylated in the endogenous protein extracted from Limulus lateral eye, and that enhanced phosphorylation at these sites occurs in vivo in response to natural circadian clock input to these eyes. These findings demonstrate in vivo changes in myosin Ill phosphorylation in response to a natural stimulus. This phosphorylation may modulate myosin Ill-actin interactions. [ABSTRACT FROM AUTHOR]

The complete mitochondrial genome (15,034 bp) of a Chinese scorpion Mesobuthus martensii (Buthidae) was sequenced and characterized in detail. The genome contains 13 protein-coding genes, 21 transfer RNA genes, two ribosomal RNA genes and a large non-coding region ( = CR). Its gene arrangement pattern is identical to that of Limulus polyphemus (Chelicerata, Xiphosura), with the exceptions of the tRNAGlu-tRNAIle-tRNAMet (Q-I-M) arrangement and tRNAAsp-loss. Additional interesting features are found and discussed: high frequency of Leu(UUG) codon use, low A+T content of the genome (66.75%), and six repeat units (five 60-nt-long and one 58-nt-long repeats) in the 998-nt CR. Bayesian analysis based on amino acid sequences of the 12 proteincoding genes (excluding ATP8) reveals that the family Buthidae (Order Scorpiones) and the class Arachnida form strong monophyletic groups within Chelicerata, respectively. It indicated that the scorpions are the most ancestral arachnids. [ABSTRACT FROM AUTHOR]

Knowledge of resource-use and movement patterns is a missing component in the development of horseshoe crab (Limulus polyphemus) management strategies. Available evidence indicates the potential for a variety of possible migratory behaviors, but the lack of high-resolution, spatial-temporal data has hindered development of a year-round profile of ranging behavior. This need was addressed in the present study by using acoustic telemetry to track the movements of adult horseshoe crabs in two subembayments (Egypt and Hog Bays) of the Taunton Bay Estuary, Maine, from June 2003 to June 2005. Estimated mean total home range sizes were 64.1 and 61.4 ha for breeding crabs tagged in Egypt and Hog Bays, respectively. We observed no horseshoe crab dispersal to areas outside of the subembayments where they were tagged, so no mixing was observed between Egypt and Hog Bay individuals despite a < 4-km separation. Observed shifts in movement patterns, resource use (subtidal versus intertidal), and vagility facilitated a profile of seasonally partitioned horseshoe crab activity, which included late April to early May post-wintering, June-July breeding, August-September pre-wintering, and October-April wintering, where space usage represented about 10% of the mean total home range size. The apparent isolation of these resident populations implies a heightened vulnerability to overexploitation and large-scale habitat alteration that might be more easily sustained by larger, more vagile populations. This work underscores the need to apply horseshoe crab conservation, research, and management efforts at scales that are appropriate to the ranging patterns of crabs, which first requires application of high-resolution methods to identify those patterns. [ABSTRACT FROM AUTHOR]

The American horseshoe crab, Limulus polyphemus, is regularly cultured and maintained in research laboratories and public aquaria. Rising concerns over the health of these captive animals makes the diagnosis and treatment of pathological conditions in L. polyphemus essential. This study investigated the kinetics of oxytetracyline following either intravascular or oral dosing. Oxytetracylcine is a broad-spectrum antibiotic used in the treatment of various bacterial diseases of aquatic animals. A noncompartmental model was developed to describe the pharmacokinetics of oxytetracycline (OTC) in the horseshoe crab. The following parameters were determined for a single intravascular bolus of 25 mg/kg OTC: AUC = 9524.60 μg·h/mL, MRT = 443.65 h, Clb = 0.044 mL/min/kg, Vd(ss) = 1.164 L/kg, t1/2 = 128.3 h, Cmax = 55.90 μg/mL, Cave = 27.39 μg/mL. Following a single oral bolus of 25 mg/kg, these parameters were calculated: AUC = 5861.81 μg·h/mL, MRT = 395.89 h, Clb = 0.071 mL/min/kg, Vd(ss) = 1.688 L/kg, t1/2 = 210.0 h, Cmax = 7.83 μg/mL, Cave = 2.89 μg/mL, F = 61.56%. [ABSTRACT FROM AUTHOR]

Adult horseshoe crabs (Limulus polyphemus) are the preferred bait in the U.S. east coast whelk pot fishery, but their harvest is being restricted because of severe population declines in the Chesapeake and Delaware bays. To identify other baits, the activity in the pallial nerve of whelks was determined during exposure of the osphradium to odorant solutions prepared from horseshoe crab eggs, horseshoe crab hemolymph, and hard clam (Mercenaria mercenaria) tissue. All three elicited significant responses; bait based on them may provide an alternative to the use of adult horseshoe crabs, although extensive behavioral testing remains to be done. Channeled whelk did not respond to molecular weight fractions (>3 kDa and <3 kDa) prepared from horseshoe crab egg odorant solutions but did respond when the molecular weight fractions were recombined. Whelks appear to have broadly tuned chemoreceptors and manufactured baits may need to mimic the complex mixture of odorants derived from natural sources. [ABSTRACT FROM AUTHOR]

Satellite male horseshoe crabs form spawning groups around some nesting pairs (female plus attached male) while leaving others to nest alone. Furthermore, females of pairs that attract satellites are larger and lay more eggs than females of pairs that do not attract satellites. We experimentally tested whether satellite males use visual cues to discriminate among large and small females and if satellites use chemical cues from eggs to distinguish among females. We conducted experiments in the field in the northern Gulf of Mexico at Seahorse Key, FL, U.S.A. in which we observed the behaviour of satellite males as they approached cement models of horseshoe crab pairs. Satellites were significantly more likely to approach and join model pairs with large females than with small females. However, there was no difference in the length of time satellites remained joined to the models. When chemical cues were examined, there was no difference in the number of males that approached or joined identical female models with and without eggs. However, once a satellite joined, it remained attached significantly longer to the model pair with eggs underneath. This study shows that satellite male horseshoe crabs use multiple cues, first visual to locate nesting pairs, then chemical to decide whether to remain with a nesting female. Our results show that males that are approaching from the water use visual cues from the amount of exposed carapace to distinguish the size of females nesting on land, even when those females are well buried in the sand. [Copyright &y& Elsevier]

Abstract: This field study evaluates the effect of nourishing an estuarine beach with gravel to enhance spawning rates by horseshoe crabs. A total of 564 m3 of coarse sand and gravel were emplaced in two 90 m-long treatment segments at Bowers Beach, Delaware, USA from 9 to 11 April 2002. Field data were gathered between 6 April and 24 May 2002 to characterize the two fill segments and the un-nourished segments between them as well as two control segments at the adjacent Ted Harvey Beach. Sediment samples were taken from the foreshore surface and at depth before and after the nourishment. Bay water levels, wave heights, and beach ground water characteristics were monitored over a 12-hour tidal cycle at one of the nourished (15 May 2002) and the unnourished segment (16 May 2002) at Bowers Beach and at one of the control segments at Ted Harvey Beach (21 May 2002) using piezometers and pressure transducers inserted in wells. The beaches were cored to estimate the density of horseshoe crab eggs deposited during the spawning season. Horseshoe crab eggs were buried in pouches at 0.15 to 0.20 m depth for 30 to 40 days to evaluate their survival in developing into embryo or larval stage. Bulk sediment samples were taken to evaluate moisture characteristics near locations where egg pouches were buried. Density of spawning females at Bowers Beach was 1.04 m−2 in 2001 and 1.20 m−2 in 2002. These rates are lower than at Ted Harvey Beach but reveal an increase in spawning while Ted Harvey Beach underwent a considerable decrease (2.63 m−2 to 1.35 m−2). Sediments low on the foreshore remained nearly saturated throughout the tidal cycle at both beaches. The average hydraulic conductivity on the upper foreshore at the non-treatment section at Bowers Beach (0.19 cm s−1) was less than at Ted Harvey Beach (0.27 cm s−1), and the finer, better sorted sediments at depth at Bowers Beach resulted in a higher porosity, creating greater moisture retention potential. Egg development was greatest at mid foreshore at all sites. Eggs at the lower foreshore elevation remained viable, but did not develop to the embryo stage. Between-beach differences were limited to high elevations where higher mortality occurred at Ted Harvey Beach due to desiccation. Adding small amounts of gravel to a sand beach may change the appearance of the surface but may not appreciably increase mean grain size and sorting at depth or the hydraulic conductivity over the spawning season. The pebble fraction may be important for site selection, but finer sizes may be more important for egg survival because of moisture retention. [Copyright &y& Elsevier]

On the basis of formerly investigated peptides corresponding to the endotoxin-binding domain from LALF [Limulus anti-LPS (lipopolysaccharide) factor], a protein from Limulus polyphemus, we have designed and synthesized peptides of different lengths with the aim of obtaining potential therapeutic agents against septic shock syndrome. For an understanding of the mechanisms of action, we performed a detailed physicochemical and biophysical analysis of the interaction of rough mutant LPS with these peptides by applying FTIR (Fourier-transform infrared) spectroscopy, SAXS (small-angle X-ray scattering), calorimetric techniques [DSC (differential scanning calorimetry) and ITC (isothermal titration calorimetry)] and FFTEM (freeze-fracture transmission electron microscopy). Also, the action of the peptides on bacteria of different origin in microbial assays was investigated. Using FTIR and DSC, our results indicated a strong fluidization of the lipid A acyl chains due to peptide binding, with a decrease in the endothermic melting enthalpy change of the acyl chains down to a complete disappearance in the 1:0.5 to 1:2 [LPS]:[peptide] molar ratio range. Via ITC, it was deduced that the binding is a clearly exothermic process which becomes saturated at a 1:0.5 to 1:2 [LPS]:[peptide] molar ratio range. The results obtained with SAXS indicated a drastic change of the aggregate structures of LPS into a multilamellar stack, which was visualized in electron micrographs as hundreds of lamellar layers. This can be directly correlated with the inhibition of the LPS-induced production of tumour necrosis factor α in human mononuclear cells, but not with the action of the peptides on bacteria. [ABSTRACT FROM AUTHOR]

1. Millions of shorebirds migrate each year through a small number of highly productive staging areas where they often conflict with fisheries interests. Delaware Bay, USA, is a major shorebird stopover site where, in spring, many thousands of shorebirds undergo rapid mass gain by feeding on the eggs of commercially harvested horseshoe crabs Limulus polyphemus. 2. Environmental factors may cause deviations from the best migration schedule. We used within-year mass gain data from red knot Calidris canutus caught in Delaware Bay between 1998 and 2005 to determine the degree of flexibility individuals have to vary migration speed. 3. Mass gain by birds below 133 g was shown to comprise 15·3% fat (39 kJ g−1), the remainder being lean mass (6 kJ g−1). Above this critical level, fat comprised 83·9% of mass deposition. The rates of energy deposition (kJ d−1) were therefore fundamentally different between the two states but were among the highest ever recorded among vertebrates (5–7 × basic metabolic rate). 4. A total of 36–62% of the variation in observed rates of energy deposition between 1998 and 2002 was explained by a year factor, date and mass at initial capture and interaction terms, such that light-weight birds at the end of May had rates of mass gain or energy deposition two to three times higher than birds of similar mass in mid-May, indicating that birds were attempting to achieve a certain mass by a certain date. In 2003 and 2005, this relationship broke down as a result of lower densities of eggs. 5. Synthesis and application. The maintenance of high densities of crab eggs required for high rates of mass gain in red knot requires severe cuts in, or the complete cessation of, the crab harvest, reduced human and raptor-related disturbance as well as management of beaches to provide sufficient crab-spawning habitat. These findings are widely applicable to other systems where harvesting activities come into conflict with migrating animals and show that certain sections of the population, in this case the long-distance migrants from South America, will be impacted more than short-distance migrants whose physiology may give them access to alternative food resources. [ABSTRACT FROM AUTHOR]

Abstract: American horseshoe crabs (Limulus polyphemus) exhibit clear circadian rhythms of visual sensitivity in the laboratory and in the field they exhibit seasonal patterns of mating behavior that are closely associated with the tides. Recent reports suggest that Limulus locomotor activity may be controlled by endogenous circadian and/or circatidal clocks and that light:dark (LD) cycles may affect the rhythmic output of both of these clocks. In this study, we examined locomotor behavior in the laboratory to determine the extent of this endogenous activity and to examine the influence of LD cycles on these rhythms. Thirty-three L. polyphemus were captured during the breeding season and their activity was monitored with activity boxes and “running wheels” in seawater kept at constant temperature and salinity. Activity patterns were analyzed using visual inspection of actograms and Chi-square and Lomb–Scargle periodograms. Overall, 36% of the animals was significantly more active during L, while only 12% was more active during D (52% showed no preference). Circatidal rhythms were observed in LD in 67% of the horseshoe crabs. Surprisingly, LD cycles appeared to synchronize these rhythms at times. In DD, the majority of animals tested (63%) exhibited circatidal rhythms that persisted for at least seven days. Overall, the results demonstrate that an endogenously controlled tidal rhythm of locomotion operates during, and significantly after, the breeding season in this species. In addition, the present results are consistent with the presence of circalunidian oscillators controlling these rhythms. [Copyright &y& Elsevier]

Digestive tract contents were examined from 297 Loggerhead Sea Turtles (Caretta caretta) in Virginia during 1983-2002. Analyses revealed a shift from predominantly Atlantic Horseshoe Crab (Limulus polyphemus) during the early to mid-1980s to predominantly Common Blue Crab (Callinectes sapidus) during the late 1980s and early 1990s. Diet in the mid-1990s and in 2000-2002 was dominated by finfish, particularly Atlantic Menhaden (Brevoortia tyrannus) and Atlantic Croaker (Micropogonias undulatus). These diet shifts suggest that horseshoe crab and blue crab population declines have caused loggerheads to forage in nets or on discarded fishery bycatch. [ABSTRACT FROM AUTHOR]

We used stable isotope (SI) methods in combination with pen feeding trials to determine the importance of eggs of the Atlantic horseshoe crab Limulus polyphemus to migratory fattening of red knots Calidris canutus rufa and ruddy turnstones Arenaria interpres morinella during spring stopover in Delaware Bay. By manifesting measurable fractionation (ca +3‰) and rapid turnover, blood plasma δ15 nitrogen proved a functional marker for SI diet tracking during the short 3-week stopover. Blood samples from free-ranging knots (3 data sets) and turnstones (1 data set) produced similar convergence of plasma δ15N signatures with increasing body mass that indicated highly similar diets. Asymptotes deviated slightly (0.3‰ to 0.7‰) from that of captive shorebirds fed a diet of only crab eggs during stopover, thus confirming a strong crab egg-shorebird linkage. The plasma δ15N crab-egg diet asymptote was enriched ca +4.5‰ and therefore readily discriminated from that of either blue mussels Mytilus edulis or coquina clams Donax variabilis, the most likely alternative prey of knots in Delaware Bay. Crab eggs were highly palatable to captive knots and turnstones which achieved rates of mass gain (3–11 g/d) comparable to that of free-ranging birds. Peak consumption rates during hyperphagic events were 23,940 and 19,360 eggs/bird/d, respectively. The empirical conversions of eggs consumed to body mass gained (5,017 eggs/g for knots and 4,320 eggs/g for turnstones) indicate the large quantities of crab eggs required for the maintenance of these shorebird populations during stopover. [ABSTRACT FROM AUTHOR]

The objective of this simulation study was to create an age-structured population model for horseshoe crabs (Limulus polyphemus) in the Delaware Bay region using best available estimates of age-specific mortality and recent harvest levels. Density dependence was incorporated using a spatial model relating egg mortality with abundance of spawning females. Combinations of annual female harvest (0, 50, 100, and 200 thousand), timing of female harvest (before or after spawning), and three levels of density-dependent egg mortality were simulated. The probability of the population increasing was high (>80%) with low and medium egg mortality and harvest less than 200 thousand females per year. Under the high egg mortality case, the probability of the population increasing was < 50% regardless of harvest. Harvest occurring after spawning increased the probability of population growth. The number of eggs available to shorebirds was highest when egg mortality was lowest and female abundance was at its highest levels. Although harvest and egg mortality influenced population growth and food availability to shorebirds, sensitivity and elasticity analyses showed that early-life stage mortality, age 0 mortality in particular, was the most important parameter for population growth. Our modeling results indicate areas where further research is needed and suggest effective management will involve a combination of harvest management and actions to increase early juvenile survival. [ABSTRACT FROM AUTHOR]

Because the Delaware Bay horseshoe crab (Limulus polyphemus) population is managed to provide for dependent species, such as migratory shorebirds, there is a need to understand the process of egg exhumation and to predict eggs available to foraging shorebirds. A simple spatial model was used to simulate horseshoe crab spawning that would occur on a typical Delaware Bay beach during spring tide cycles to quantify density-dependent nest disturbance. At least 20% of nests and eggs were disturbed for levels of spawning greater than one third of the average density in Delaware Bay during 2004. Nest disturbance increased approximately linearly as spawning density increased from one half to twice the 2004 level. As spawning density increased further, the percentage of eggs that were disturbed reached an asymptote of 70% for densities up to 10 times the density in 2004. Nest disturbance was heaviest in the mid beach zone. Nest disturbance precedes entrainment and begins the process of exhumation of eggs to surface sediments. Model predictions were combined with observations from egg surveys to estimate a snap-shot exhumation rate of 5–9% of disturbed eggs. Because an unknown quantity of eggs were exhumed and removed from the beach prior to the survey, cumulative exhumation rate was likely to have been higher than the snap-shot estimate. Because egg exhumation is density-dependent, in addition to managing for a high population size, identification and conservation of beaches where spawning horseshoe crabs concentrate in high densities (i.e., hot spots) are important steps toward providing a reliable food supply for migratory shorebirds. [ABSTRACT FROM AUTHOR]

Abstract: The blue copper protein hemocyanin from the horseshoe crab Limulus polyphemus is among the largest respiratory proteins found in nature (3.5 MDa) and exhibits a highly cooperative oxygen binding. Its 48 subunits are arranged as eight hexamers (1×6mers) that form the native 8×6mer in a nested hierarchy of 2×6mers and 4×6mers. This quaternary structure is established by eight subunit types (termed I, IIA, II, IIIA, IIIB, IV, V, and VI), of which only type II has been sequenced. Crystal structures of the 1×6mer are available, but for the 8×6mer only a 40 Å 3D reconstruction exists. Consequently, the structural parameters of the 8×6mer are not firmly established, and the molecular interfaces between the eight hexamers are still to be defined. This, however, is crucial for understanding how allosteric transitions are mediated between the different levels of hierarchy. Here, we show the 10 Å structure (FSC1/2-bit criterion) of the oxygenated 8×6mer from cryo-electron microscopy (cryo-EM) and single-particle analysis. Moreover, we show its molecular model as obtained by DNA sequencing of subunits II, IIIA, IV and VI, and molecular modelling and rigid-body fitting of all subunit types. Remarkably, the latter enabled us to improve the resolution of the cryo-EM structure from 11 Å to the final 10 Å. The 10 Å structure allows firm assessment of various structural parameters of the 8×6mer, the 4×6mer and the 2×6mer, and reveals a total of 46 inter-hexamer bridges. These group as 11 types of interface: four at the 2×6mer level (II–II, II–IV, V–VI, IV–VI), three form the 4×6mer (V–V, V–VI, VI–IIIB/IV/V), and four are required to assemble the 8×6mer (IIIA–IIIA, IIIA–IIIB, II–IV, IV–IV). The molecular model shows the amino acid residues involved, and reveals that several of the interfaces are intriguingly histidine-rich and likely to transfer allosteric signals between the different levels of the nested hierarchy. [Copyright &y& Elsevier]

Abstract: Although having highly similar primary to tertiary structures, the different guanidino kinases exhibit distinct quaternary structures: monomer, dimer or octamer. However, no evidence for communication between subunits has yet been provided, and reasons for these different levels of quaternary complexity that can be observed from invertebrate to mammalian guanidino kinases remain elusive. Muscle creatine kinase is a dimer and disruption of the interface between subunits has been shown to give rise to destabilized monomers with slight residual activity; this low activity could, however, be due to a fraction of protein molecules present as dimer. CK monomer/monomer interface involves electrostatic interactions and increasing salt concentrations unfold and inactivate this enzyme. NaCl and guanidine hydrochloride show a synergistic unfolding effect and, whatever the respective concentrations of these compounds, inactivation is associated with a dissociation of the dimer. Using an interface mutant (W210Y), protein concentration dependence of the NaCl-induced unfolding profile indicates that the active dimer is in equilibrium with an inactive monomeric state. Although highly similar to muscle CK, horse shoe crab (Limulus polyphemus) arginine kinase (AK) is enzymatically active as a monomer. Indeed, high ionic strengths that can monomerize and inactivate CK, have no effect on AK enzymatic activity or on its structure as judged from intrinsic fluorescence data. Our results indicate that expression of muscle creatine kinase catalytic activity is dependent on its dimeric state which is required for a proper stabilization of the monomers. [Copyright &y& Elsevier]

A decline in red knots (Calidris canutus rufa) has been attributed to horseshoe crab (Limulus polyphemus) egg shortages on the Delaware Bay, an important foraging area for migrating knots. We studied the movements and distribution of 65 radiotagged red knots on Delaware Bay from May to June 2004 and related movements to the distribution and abundance of horseshoe crab eggs and other prey and to other habitat characteristics. The number of horseshoe crab eggs was the most important factor determining the use of Delaware Bay beaches by red knots (logistic regression cumulative Akaike's Information Criterion adjusted for small sample size [AICc} w = 0.99). The knots shifted from emergent marsh and peat-beaches to sandy Delaware Bay beach when crab eggs became abundant, which also suggested the importance of crab eggs. While red knots used sandy beach zones more than expected, given their availability, 44% of red knot low tide locations were in bay and coastal emergent marsh. The abundance of Donax variabilis (AICc w = 0.95) and Mytilus edulis (AICc w = 0.94) spat, both food for red knots, had a relationship with red knot use of sandy beaches. Levels of disturbance and the abundance of laughing gulls (Larus atricilla) also were important factors in red knot sandy beach use, although secondary to prey resources (AICc w < 0.4). These results are consistent with the hypothesis that the abundance of horseshoe crab eggs on sandy beaches is driving movement and distribution of red knots and that there is little alternative food during the migratory stopover in Delaware Bay. Our findings that red knots disproportionately use Delaware Bay sites with abundant eggs and that there is a lack of surplus eggs at areas used and unused by red knots support the continuation of management for sustained yield of horseshoe crabs and other food resources at this stopover. [ABSTRACT FROM AUTHOR]

Abstract: The American horseshoe crab, Limulus polyphemus (Linnaeus), typically inhabits estuaries and coastal areas with pronounced semi-diurnal and diurnal tides that are used to synchronize the timing of spawning, larval hatching, and emergence. Horseshoe crabs spawn in the intertidal zone of sandy beaches and larval emergence occurs when the larvae exit the sediments and enter the plankton. However, L. polyphemus populations also occur in areas that lack significant tidal changes and associated synchronization cues. Endogenous activity rhythms that match predictable environmental cycles may enable larval horseshoe crabs to time swimming activity to prevent stranding on the beach. To determine if L. polyphemus larvae possess a circatidal rhythm in vertical swimming, larvae collected from beach nests and the plankton were placed under constant conditions and their activity monitored for 72 h. Time-series analyses of the activity records revealed a circatidal rhythm with a free-running period of ≈12.5 h. Maximum swimming activity consistently occurred during the time of expected falling tides, which may serve to reduce the chance of larvae being stranded on the beach and aid in seaward transport by ebb currents (i.e., ebb-tide transport). To determine if agitation serves as the entrainment cue, larvae were shaken on a 12.4 h cycle to simulate conditions during high tide in areas with semi-diurnal tides. When placed under constant conditions, larval swimming increased near the expected times of agitation. Thus, endogenous rhythms of swimming activity of L. polyphemus larvae in both tidal and nontidal systems may help synchronize swimming activity with periods of high water and inundation. [Copyright &y& Elsevier]

Abstract: The phototransduction cascade in Limulus ventral photoreceptors involves multiple second messengers, including Ca2+ and cGMP. Light-induced Ca2+ release from intracellular stores is an intermediate step, but the subsequent Ca2+-activated reaction remains to be determined. The possibility that Ca2+/calmodulin (Ca2+/CaM) might be involved is suggested by the high calmodulin content of the transducing lobe. To test whether CaM can excite the transduction cascade we injected a 25μM Ca2+/CaM solution. This produced a rapid, brief depolarization similar to that produced by light, suggesting a role for CaM in the cascade. However, an important caveat is that Ca2+ dissociating from the Ca2+/CaM complex might excite this process. Several control experiments argue against, but do not entirely eliminate this possibility. To test whether endogenous CaM has a function in excitation, trifluoperazine was pressure injected into the rhabdomeric region. The response to brief flashes was not affected, but the response to steady illumination was transiently attenuated by each injection. We conclude that calmodulin should be considered a candidate to couple intermediate and late stages of the transduction cascade. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Aim: To investigate the role of intercellular potassium in tachyplesin-induced HL-60 cells apoptosis. Methods: The concentration of intercellular potassium, cell volume and mitochondrial membrane potential were examined by flow cytometry. Results: The concentration of intercellular potassium reduced in a time-dependent manner in tachyplesin-treated HL-60 cells. In addition, the loss of mitochondrial membrane potential was tightly coupled with the shrinkage of cell volume. Different caspase inhibitors protected against DNA degradation but did not prevent the loss of HL-60 cell viability induced by tachyplesin. Ba2+, which was a kind of blocker of volume-regulatory K+ channels, increased the viability of tachyplesin-treated HL-60 cells and maintained mitochondrial membrane potential and cell volume. Conclusion: Efflux of K+ was an important reason for apoptosis in tachyplesin-treated HL-60 cells. Efflux of K+ affected the viability of tachyplesin-treated HL-60 cells independent of the process of caspase activation. [ABSTRACT FROM AUTHOR]

Beach replenishment has been proposed to increase nesting habitat for horseshoe crabs, but its environmental consequences may compromise the egg development and viability of this declining species. Horseshoe crab habitat requirements were used to build a habitat suitability model in STELLA to predict the potential impacts of beach replenishment on horseshoe crab eggs. A habitat suitability index (H.S.I.) comprised of six variables (dissolved oxygen, sediment grain size, sand temperature, sand moisture, wave energy, and salinity) was developed and compared between replenished and natural beaches. Sediment grain size and dissolved oxygen were higher in the natural beach, whereas sand temperature and moisture were higher in the replenished beach, resulting in significantly higher suitability of the natural beach ( p = 5.39 × 10 -15 , df = 30). The model was most sensitive to air temperature, rainfall, tide, and sediment grain size. This model is useful for understanding the processes affecting horseshoe crabs and predicting impacts of coastal management activities on habitat suitability. Based on the results of this model, beach replenishment is not recommended for increasing or improving horseshoe crab habitat, unless care is taken to match fill sediment to natural grain size and color. [ABSTRACT FROM AUTHOR]

The Atlantic horseshoe crab, Limulus polyphemus, is harvested by the biomedical industry for Limulus Amoebocyte Lysate (LAL) a blood compound used to detect endotoxins, for scientific research on vision, and as bait for the eel and conch fisheries. They are also subject to sources of natural mortality such as consumption of eggs by shorebirds and stranding. Recently there has been growing concern over possible declines in Limulus populations along the east coast of the United States. We have used stage-structured matrix modeling to improve our understanding of Limulus population dynamics in three Cape Cod estuaries (Stage Harbor, Pleasant Bay, and Barnstable Harbor) with differing harvest pressures. The results suggest that a low level of harvest is sustainable, particularly if timing and size-specificity of the harvest are taken into consideration. The model also suggests that efforts should be made to avoid harvesting crabs prior to sexual maturity, as the population growth rate is more sensitive to changes in survival rate of older juveniles than of other stages. The information the model provides could assist local and regional fisheries managers in establishing appropriate regulations for the horseshoe crab fishery. [ABSTRACT FROM AUTHOR]

Estimates of the abundance of American horseshoe crabs (Limulus polyphemus) are important to determine egg production and to manage populations for the energetic needs of shorebirds that feed on horseshoe crab eggs. In 2003, over 17,500 horseshoe crabs were tagged and released throughout Delaware Bay, and recaptured crabs came from spawning surveys that were conducted during peak spawning. We used two release cohorts to test for a temporary effect of tagging on spawning behavior and we adjusted the number of releases according to relocation rates from a telemetry study. The abundance estimate was 20 million horseshoe crabs (90 % confidence interval: 13-28 million), of which 6.25 million (90% CI: 4.0-8.8 million) were females. The combined harvest rate for Delaware, New Jersey, Virginia, and Maryland in 2003 was 4% (90% CI: 3-6%) of the abundance estimate. Over-wintering of adults in Delaware Bay could explain, in part, differences in estimates from ocean-trawl surveys. Based on fecundity of 88,000 eggs per female, egg production was 5.5 x 1011 (90% CI: 3.5 x 1011, 7.7 x 1011), but egg availability for shorebirds also depended on overlap between horseshoe crab and shorebird migrations, density-dependent bioturbation, and wave-mediated vertical transport. [ABSTRACT FROM AUTHOR]

Abstract: In innate immunity, pattern recognition receptors discriminate between self- and infectious non-self-matter. Mammalian homologs of the Drosophila Toll protein, which are collectively referred to as Toll-like receptors (TLRs), recognize pathogen-associated molecular patterns (PAMPs), including lipopolysaccharides (LPS) and lipoproteins, whereas the Drosophila Toll protein does not act as a PAMP receptor, but rather binds to Spätzle, an endogenous peptide. In Drosophila, innate immune surveillance is mediated by members of the peptidoglycan recognition protein (PGRP) family, which recognize diverse bacteria-derived peptidoglycans and initiate appropriate immune reactions including the release of antimicrobial peptides and the activation of the prophenoloxidase cascade, the latter effecting localized wound healing, melanization, and microbial phagocytosis. In the horseshoe crab, LPS induces hemocyte exocytotic degranulation, resulting in the secretion of various defense molecules, such as coagulation factors, antimicrobial peptides, and lectins. Recent studies have demonstrated that the zymogen form of the serine protease factor C, a major granular component of hemocyte, also exists on the hemocyte surface and functions as a biosensor for LPS. The proteolytic activity of activated factor C initiates hemocyte exocytosis via a G protein mediated signal transduction pathway. Furthermore, it has become clear that an endogenous mechanism for the feedback amplification of the innate immune response exists and is dependent upon a granular component of the horseshoe crab hemocyte. [Copyright &y& Elsevier]

Discusses findings of a research which isolated and tested certain elements of the bleeding process to gain information on the potential causes of mortality for horseshoe crabs used in the biomedical industry. Uses of horseshoe crabs by biomedical companies; Factors which necessitate a conservative, risk-averse management approach for horeshoe crabs; Potential stressors of hrosehoe crabs throughout the typical biomedical bleeding process.