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C-reactive protein (CRP) binds to phosphocholine (PCh)-containing substances and subsequently activates the complement system to eliminate the ligand. The PCh- binding function of CRP has been conserved throughout evolution from arthropods to humans. Human CRP, in its structurally altered conformation at acidic pH, also binds to amyloid-β (Aβ) and prevents the formation of Aβ fibrils. It is unknown whether the Aβ-binding function of CRP has also been evolutionarily conserved. The aim of this study was to determine whether CRP isolated from American horseshoe crab Limulus polyphemus was also anti-amyloidogenic and whether this function required structural alteration of Limulus CRP (Li-CRP). Two CRP species Li-CRP-I and Li-CRP-II were purified from hemolymph by employing PCh-affinity chromatography and phosphoethanolamine-affinity chromatography, respectively. Both Li-CRP-I and Li-CRP-II bound to immobilized Aβ at physiological pH. Unlike human CRP, Li-CRP did not require any changes in its overall structure to bind to Aβ. Both Li-CRP-I and Li-CRP-II bound to Aβ in the fluid phase also and prevented the fibrillation of Aβ. Additionally, ion-exchange chromatography of purified Li-CRP indicated that a variety of Li-CRP molecules of different subunit compositions were present in Limulus hemolymph, raising the possibility that the presence of various Li-CRP species in hemolymph facilitates the recognition of a range of proteins with differing amyloidogenicity. We conclude that the binding of CRP to Aβ is an ancient function of CRP. In invertebrates, the Aβ-binding function of CRP can protect the host from toxicity caused by amyloidogenic and pathogenic proteins. In humans, the Aβ-binding function of CRP can protect against inflammatory diseases in which the host proteins are ectopically deposited on either host cells or foreign cells in an inflammatory milieu since immobilized proteins may expose Aβ-like structures after deposition at places where they are not supposed to be. [ABSTRACT FROM AUTHOR]

The timing of American horseshoe crab (Limulus polyphemus) spawning behavior along the coast of Florida (United States) is generally associated with the highest tides during the spring and fall lunar cycles. All Florida estuaries support horseshoe crab populations, but tidal characteristics vary markedly among locations, which may influence the timing of horseshoe crab spawning behavior. The Indian River Lagoon is a large microtidal estuary on Florida's east coast. Given the microtidal nature of the lagoon, it is unclear which environmental factors affect horseshoe spawning. In 2019, volunteers of Florida Horseshoe Crab Watch conducted daily surveys at two sites in the northern Indian River Lagoon during peak spawning months (February–April). During each survey, volunteers counted all spawning horseshoe crabs and recorded environmental variables, including water temperature, air temperature, wind speed, wind direction, salinity, and tide height. We developed a suite of negative-binomial regression models to quantify relationships between the number of spawning horseshoe crabs and environmental factors. Modeling results indicated a positive relationship between onshore wind speed and number of spawning horseshoe crabs. Our study suggests that in the absence of tidal cues, onshore wind speed may be an important driver of horseshoe crab spawning activity in microtidal estuarine systems. [ABSTRACT FROM AUTHOR]

While considered ecological generalists in most aspects of their life history, horseshoe crabs (Limulus polyphemus) have traditionally been regarded as reproductive habitat specialists, given that spawning is thought to occur primarily on beaches where conditions for embryonic development are considered optimal. Observations of horseshoe crabs spawning in other habitats were deemed isolated and the behavior non‐adaptive. Here, we used spawning and egg surveys to compare the use of beach and salt marsh habitats for spawning by the horseshoe crab in three US states along the Atlantic coast. We found similar spawning and egg densities in both habitats but were more likely to find eggs in marsh habitats, indicating that spawning in marsh habitats is common and geographically widespread. These results suggest that the conservation of salt marshes may be critical for the protection of this species and that management strategies should be revised to incorporate this generalist behavior. [ABSTRACT FROM AUTHOR]

A comparative study of reagents obtained from hemolymph of Atlantic and Asian horseshoe crabs proved the reliability of bacterial endotoxin determination. It is noted that the enzymatic activity of amebocyte lysate may differ in relation to standard endotoxin and natural endotoxin. [ABSTRACT FROM AUTHOR]

C-reactive protein (CRP) binds to phosphocholine (PCh)-containing substances and subsequently activates the complement system to eliminate the ligand. The PCh-binding function of CRP has been conserved throughout evolution from arthropods to humans. Human CRP, in its structurally altered conformation at acidic pH, also binds to amyloid-β (Aβ) and prevents the formation of Aβ fibrils. It is unknown whether the Aβ-binding function of CRP has also been evolutionarily conserved. The aim of this study was to determine whether CRP isolated from American horseshoe crab Limulus polyphemus was also anti-amyloidogenic and whether this function required structural alteration of Limulus CRP (Li-CRP). Two CRP species Li-CRP-I and Li-CRP-II were purified from hemolymph by employing PCh-affinity chromatography and phosphoethanolamine-affinity chromatography, respectively. Both Li-CRP-I and Li-CRP-II bound to immobilized Aβ at physiological pH. Unlike human CRP, Li-CRP did not require any changes in its overall structure to bind to Aβ. Both Li-CRP-I and Li-CRP-II bound to Aβ in the fluid phase also and prevented the fibrillation of Aβ. Additionally, ion-exchange chromatography of purified Li-CRP indicated that a variety of Li-CRP molecules of different subunit compositions were present in Limulus hemolymph, raising the possibility that the presence of various Li-CRP species in hemolymph facilitates the recognition of a range of proteins with differing amyloidogenicity. We conclude that the binding of CRP to Aβ is an ancient function of CRP. In invertebrates, the Aβ-binding function of CRP can protect the host from toxicity caused by amyloidogenic and pathogenic proteins. In humans, the Aβ-binding function of CRP can protect against inflammatory diseases in which the host proteins are ectopically deposited on either host cells or foreign cells in an inflammatory milieu since immobilized proteins may expose Aβ-like structures after deposition at places where they are not supposed to be.

Horseshoe crabs represent the most ancestral chelicerate lineage characterized by marine ecology and the possession of lateral compound eyes. While considered living fossils, recent studies reported an unusual number of Pax6 genes in the Atlantic horseshoe crab Limulus polyphemus. Pax genes encode ancient metazoan transcription factors, which comprise seven subfamilies. Among these, the members of the Pax6 subfamily confer critical functions in the development of the head, the visual system, and further body plan components. Arthropods are generally characterized by two Pax6 subfamily homologs that were discovered in Drosophila and named eyeless (ey) and twin of eyeless (toy). However, whole genome sequence searches uncovered three homologs of ey and two homologs of toy in L. polyphemus. These numbers are explained by the occurrence of likely three whole genome duplications in the lineage to the last common ancestor of L. polyphemus and the three additional members of the extant horseshoe crab species cluster. Here, we report that all five L. polyphemus Pax6 paralogs are conserved in the approximately 135-million-year-old horseshoe crab species cluster and that they evolve under strong purifying selection. Largely homogenous protein sequence diversification rates of ey and toy paralogs suggest subfunctionalization as the likeliest preservation trajectory. However, our studies further revealed evidence that the horseshoe crab ey1 and ey2 paralogs share a derived splice isoform that encodes a unique five amino acid-long insertion in helix 3 of the homeodomain. This suggests that the exceptional expansion of the horseshoe crab Pax6 gene family repertoire was also associated with regulatory diversification and possibly innovation. [ABSTRACT FROM AUTHOR]

Gram-negative bacterial endotoxins can cause pathophysiological effects such as high fever when introduced into the bloodstream. Therefore, endotoxin testing is necessary when producing injectable pharmaceuticals. The pharmaceutical industry has widely used Limulus amebocyte lysate (LAL) to certify product quality. However, ethical concerns have been raised and the increasing scarcity of Limulus polyphemus necessitates the development of novel testing techniques. Recombinant factor C (rFC) was developed using genetic engineering techniques. The aim of this study was to investigate the validity of rFC testing and compare it with the LAL method. The specificity, linearity, accuracy, precision, and robustness of the rFC assay were evaluated. After validation, the rFC assay was found to be suitable for endotoxin detection. We compared the accuracy of the rFC and LAL assays using reference standard endotoxin. The rFC assay was as accurate as the LAL assay. We also compared the two assays using biopharmaceuticals. Greater interference occurred in some samples when the rFC assay was used than when the LAL assay was used. However, the rFC assay overcame the interference when the samples were diluted. Overall, we suggest that rFC can be applied to test biopharmaceuticals. [ABSTRACT FROM AUTHOR]

Aim: Adult body size often exhibits patterns across large‐scale environmental gradients, creating ecogeographic clines. However, the form of body size clines varies across taxonomic groups, with linear and non‐linear patterns in body size observed in nature. Non‐linear body size clines have received less study, and questions remain about how environmental gradients interact to produce non‐linear clines. We examined the body size of the American horseshoe crab (Limulus polyphemus), a widely distributed marine arthropod, and evaluated the hypothesis that temperature and active season length can interact multiplicatively to result in a dome‐shaped distribution. Location: Fourteen states in the United States of America and three Mexican states, representing the entire geographic range of the species. Methods: We compiled environmental data and body size measurements from more than 49,000 individual horseshoe crabs. For each location, we extracted from the literature or calculated from raw data the mean male prosoma width and the mean female prosoma width. We applied a general additive modelling (GAM) approach to characterize the body size cline, test a hypothesis regarding temperature and season length, and explore evidence for the influence of additional environmental factors. Results: Model results indicate temperature and season length could act multiplicatively to produce dome‐shaped clines, and these findings align with and quantify previous anecdotal reports of a strong dome‐shaped body size cline across latitude for horseshoe crabs. Main Conclusions: Active season length appears to become relatively more influential on horseshoe crab body size in the northern part of their range, while temperature effects per se appear to dominate in southern latitudes. For horseshoe crabs, the pattern of size variation is consistent with the predictions of Optimal Resource Allocation models, but more study is needed to elucidate mechanistic underpinnings. Considering climate change projections, results from our study suggest future shifts in horseshoe crab body sizes. [ABSTRACT FROM AUTHOR]

Horseshoe crab Factor G is a heterodimeric serine protease zymogen that is activated by (1→3)-β-D-glucans (BDG) from fungal cell walls. This reaction is used in diagnostic agents for deep-seated mycosis. At present, functional analysis using Factor G from Tachypleus tridentatus has been performed, and genetic information has been published, but reconstitution using recombinant proteins has not yet been achieved. In this study, we cloned the genes for Factor G α and β from Limulus polyphemus; two gene sequences were obtained for Factor G α and seven for β. The obtained L. polyphemus Factor G α was used to specifically remove BDG from the culture medium for eliminating the activator BDG. The optimal combination for each sequence was examined with BDG removal medium, and a combination was found that featured BDG-dependent activity. These results indicate that a BDG assay system using recombinant Factor G is feasible in reconstitution. This research will support future reagent development that does not require natural horseshoe crab resources. Key points: • Cloned novel Factor G α subunit and β subunit genes from L. polyphemus • Proposed a method of removing BDG without reducing culture medium performance • Identified combination of recombinant α and β subunits for BDG-dependent activation [ABSTRACT FROM AUTHOR]

Bleeding of horseshoe crabs (Limulus polyphemus) for the biomedical industry can have both sublethal and lethal impacts. Bleeding induces a significant drop in the concentration of hemolymph hemocyanin, as well as decreased levels of activity. Furthermore, horseshoe crabs with low hemocyanin prior to being bled have been found to be more likely to die after the procedure. The goal of this project was to determine whether feeding horseshoe crabs after bleeding them could enhance the recovery of their hemocyanin levels and, in doing so, improve their physiological status. The feeds tested in separate experiments included (1) natural forage items, blue mussels (Mytilus edulis) or softshell clams (Mya arenaria); (2) a formulated diet containing green crabs (Carcinus maenas) and Limulus hemolymph; and (3) a modified commercially available shrimp (Litopenaeus vannamei) broodstock aquafeed. Horseshoe crabs (n = 63) were bled and then either fed or not fed, and their hemolymph hemocyanin concentrations were measured before they were bled and for the following 6–14 days. An additional 25 horseshoe crabs were treated in the same manner but not bled. In three experiments, horseshoe crabs that were fed consistently showed significantly higher hemolymph hemocyanin concentrations compared to those that were not fed. These data suggest that relatively simple modifications of the industrial bleeding procedure, such as feeding horseshoe crabs after bleeding them, may improve their physiological status prior to release. [ABSTRACT FROM AUTHOR]

While several marine species exhibit biological rhythms of heart rate, gill ventilation, or locomotion, the relationship between these three measures in any species remains unexplored. The American horseshoe crab, Limulus polyphemus Linnaeus, 1758 , expresses circalunidian locomotor rhythms and circadian eye sensitivity rhythms, but it is not clear if either heart and ventilation rates are controlled on a circadian, or circatidal basis or the nature of the relationship between these three measures. We aimed to determine the extent to which the heart and ventilation rates of L. polyphemus are coordinated with its endogenous rhythms of locomotion. We recorded rhythmic beating of the heart and movements of the gill plates in freely moving horseshoe crabs. Most individuals exhibited robust circatidal rhythms of locomotion, heart rate, and ventilation that were highly correlated with each other over three weeks of continuous recording. These results are the first showing long-term rhythms of all three measures in any marine species and suggest that heart rate and ventilation rhythms are coordinated in L. polyphemus , both with each other, and with locomotion, and thus are all modulated on a tidal basis. [ABSTRACT FROM AUTHOR]

The elements in blood normally reflect the levels in prey, indicating a recent exposure. Laughing gulls (Leucophaes atricilla) eat mainly horseshoe crab eggs (Limulus polyphemus) in the spring in Delaware Bay, New Jersey. The levels of arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), mercury (Hg), and selenium (Se) in the blood of laughing gulls foraging on crab eggs were examined in Delaware Bay to provide information on a species that is normally a generalist, and to determine if the levels of these elements were similar in 2019 and 2022/2023, were intercorrelated, and were related to those in crab eggs. Hg increased from 2019 (136 ± 31 ng/g) to 2022/2023 (473 ± 75 ng/g), while Cd and Se decreased. There were some significant correlations among elements and a close relationship between the element levels in blood and those in crab eggs collected in the same month (except for As). The levels differed between laughing gulls and three species of shorebirds for As and Cd. The elements in the blood of gulls and shorebirds should be similar because they eat mainly the same eggs in the same places. A significant proportion of laughing gull blood samples had levels of Hg and Se that were above the levels associated with adverse effects, which requires further examination. [ABSTRACT FROM AUTHOR]

According to an International Union for Conservation of Nature (IUCN) Red List assessment (RLA), the American horseshoe crab (Limulus polyphemus), an iconic coastal species, is at risk of extirpation in some regions within its range where small and vulnerable populations occur. However, the RLA does not consider future status beyond viability and does not attempt to identify the conservation necessary to effectively mitigate threats and recover the species to full ecological functionality. To aid in conservation planning for vulnerable species, the IUCN developed the Green Status of Species assessment (GSA) process to complement the RLA.This paper describes the application of the GSA process to assess the recovery potential of the American horseshoe crab. First, specific Limulus populations within spatial units for conservation were delineated, and their statuses were defined based on viability and ecological functionality. Then conservation actions were identified that would promote recovery and affect their near‐ and long‐term population status under different conservation scenarios.Horseshoe crab conservation has relied on, and will continue to depend on, effective harvest regulation. However, as currently conceived, conservation is not expected to mitigate habitat loss at the scale required to restore range‐wide ecological functionality, primarily because habitat loss is widespread and affected by climate change. Thus, the GSA results, while indicating that there is potential for near‐term recovery gains, reveal that long‐term recovery is in doubt owing to expected loss of habitat.To conserve critical habitats for spawning and early life stages and achieve ecological functionality, it is imperative to identify and develop conservation plans at appropriate spatial scales. Unfortunately, such plans do not currently exist and need to be established. The GSA Green Score can then serve as a metric for monitoring recovery and gauging the effectiveness of conservation implementation. [ABSTRACT FROM AUTHOR]

Objective: This paper applies a catch multiple survey analysis (CMSA) to Atlantic horseshoe crabs Limulus polyphemus in the Delaware Bay to generate robust population estimates for harvest management. Currently, horseshoe crabs along the U.S. Atlantic coast are harvested as bait for other fisheries and collected for their blood, which is used in a biomedical industry. The Delaware Bay is home to the largest population of horseshoe crabs and is a significant stopover for shorebirds to rebuild energy by consuming horseshoe crab eggs prior to completing their northward migration. To address this interrelationship, the Adaptive Resource Management (ARM) Framework has been used since 2013 to ensure that horseshoe crab harvest within the region takes into account the forage needs of migratory birds. Since its inception, the ARM Framework has used a single trawl survey's swept area‐based population estimates of horseshoe crab relative abundance and a theoretical population model developed primarily from literature‐derived values. With more data collected in the region in recent years and other sources of mortality that can now be quantified, a catch survey model can provide horseshoe crab population estimates going forward. Methods: A CMSA was used to estimate male and female horseshoe crab population size for 2003–2021 using all quantifiable sources of mortality and three fishery‐independent indices of abundance. Result: The CMSA results indicated that adult abundance of male and female horseshoe crabs was stable from 2003 to 2013 and then began to increase through 2017, a result that is consistent with stock rebuilding following a period of harvest restrictions as recommended by the ARM Framework. Population estimates were lower in recent years but remained above the levels estimated before implementation of the ARM Framework. In 2021, the CMSA estimated that there were over 6 million mature females and nearly 16 million mature male horseshoe crabs in the region. Conclusion: The CMSA provides the best and most comprehensive population estimates of horseshoe crabs in Delaware Bay and will improve modeling efforts within the ARM Framework going forward. Impact statementBeing able to estimate the size of the Atlantic horseshoe crab population in the Delaware Bay will help managers set appropriate harvest levels that will support its fisheries while also ensuring there are enough horseshoe crab eggs to feed migrating shorebirds. [ABSTRACT FROM AUTHOR]

Parasitic infections can have profound implications on host fitness, yet there is minimal information on parasites of the American horseshoe crab (Limulus polyphemus), a species that has experienced recent population declines. Therefore, we aimed to quantify the prevalence, intensity, and gill surface area coverage of the ectoparasite Bdelloura candida in adult (n = 58), sub-adult (n = 7) and juvenile (n = 32) horseshoe crabs (HSCs) collected from coastal waters of Long Island, NY in 2019 and 2022. Sub samples of horseshoe crab gill tissue (10%) were collected from live specimens and B. candida cocoon intensities from individual lamellae were enumerated microscopically. B. candida was present in all adult and sub-adult crabs (100%), whereas juveniles exhibited 6.2% prevalence. 4.0–94.0% of gill lamellae harbored cocoons, with intensities ranging from 0 to 805 cocoons per sub sample. Cocoon covered between 0.06%–14.51% of the gill sub sample surface area, with higher cocoon intensities observed in the ventral-most gill quartiles relative to the dorsal-most regions. Sex was strongly supported as a primary driver behind B. candida infection intensities with adult females harboring higher intensities. These results provide novel insight into B. candida infection dynamics across HSC demographics, but further research is necessary to quantify the physiological impacts of the infection on L. polyphemus. [ABSTRACT FROM AUTHOR]

Understanding variations in metal levels in biota geographically and under different environmental conditions is essential to determining risk to organisms themselves and to their predators. It is often difficult to determine food chain relationships because predators may eat several different prey types. Horseshoe crab (Limulus polyphemus) eggs form the basis for a complex food web in Delaware Bay, New Jersey, USA. Female horseshoe crabs lay thumb-sized clutches of eggs, several cm below the surface, and often dislodge previously laid eggs that are brought to the surface by wave action, where they are accessible and critical food for migrant shorebirds. This paper compares metal and metalloid (chromium [Cr], cadmium [Cd], lead [Pb], mercury [Hg], arsenic [As] and selenium [Se]) concentrations in horseshoe crab eggs collected on the surface with concentrations in eggs from clutches excavated from below the sand surface, as well as examining metals in eggs from different parts of the Bay. The eggs were all collected in May 2019, corresponding to the presence of the four main species of shorebirds migrating through Delaware Bay. These migrating birds eat almost entirely horseshoe crab eggs during their stopover in Delaware Bay, and there are differences in the levels of metals in blood of different shorebirds. These differences could be due to whether they have access to egg clutches below sand (ruddy turnstones, Arenaria interpres) or only to eggs on the surface (the threatened red knot [Calidris canutus rufa] and other species of shorebirds). Correlations between metals in clutches were also examined. Except for As and Cd, there were no significant differences between the metals in crab egg clutches and eggs on the surface that shorebirds, gulls, and other predators eat. There were significant locational differences in metal levels in horseshoe crab eggs (except for Pb), with most metals being highest in the sites on the lower portion of Delaware Bay. Most metals in crab eggs have declined since studies were conducted in the mid-1990s but were similar to levels in horseshoe crab eggs in 2012. The data continue to provide important monitoring and assessment information for a keystone species in an ecosystem that supports many species, including threatened and declining shorebird species during spring migration. [ABSTRACT FROM AUTHOR]

The American horseshoe crab (Limulus polyphemus) is an economically and ecologically important species, which is currently categorized as endangered in Mexico. L. polyphemus, one of four extant horseshoe crab species that constitute the class Merostomata, is distributed along the Atlantic coastline of the USA from Alabama to Maine and has another population on the coastline of Campeche, Yucatan, and Quintana Roo in the Yucatan Peninsula, Mexico. In the present study, we evaluated the genetic diversity and genetic structure of four separated localities along the coast of the Yucatan peninsula (Champoton, CH; Isla Arena, IA; Rio Lagartos, RL; and Holbox Island, HI), using nine microsatellite-type molecular markers for this species. The aim of this study is to obtain a baseline of the current level of genetic diversity, which would allow the monitoring of important changes over time. Multilocus analyses revealed moderate levels of genetic diversity (He, 0.5230 to 0.6389) and genetic structure within the whole study area (FST 0.025). The population from RL showed limited gene flows, differing significantly from the other sampling sites. The genetic information obtained in this study can support the implementation of management and conservation programs for this species in Mexico. [ABSTRACT FROM AUTHOR]

In this study trilobite larvae and early juvenile stages of Limulus polyphemus (Linnaeus, 1758) are examined using light microscopy and scanning electron microscopy to examine the mechanoreceptors present on the cuticle. Three forms of mechanoreceptors were described on the trilobite larvae of L. polyphemus, (1) tactile sensilla, (2) peg sensilla and (3) helical sensilla. Tactile sensilla are adapted to detect touch. Peg sensilla are adapted to detect water currents and near field sound. The helical sensilla are new to science and their function is not known. The genus Limulus Müller 1785 has a fossil record from the Jurassic era, 148 million years. Before the Common Era (BCE) to the present. Having survived through the mass extinction at the end of the Mesozoic era, it is referred to as a "Stabilomorph". As a Stabilomorph the morphology of mechanoreceptors, specifically sensilla capable of sensing particle motions, found on trilobite larva of L. polyphemus may shed some light on the mechanisms of near field sound or particle motion detection in Jurassic seas. To detect particle motion, near-field sound energy, the sensory organ must extend through the boundary layer. The thickness of the boundary layer (δ) for particle motion in water is equal to [kinematic viscosity/sound wave frequency]1/2, less than 200 μm in the range of human hearing. The value of δ in air is 2.54 [kinematic viscosity/sound wave frequency]1/2, about 1 to 2 millimeters in the range of human hearing. Therefore, the mechanoreceptors active in the detection of particle motion are typically shorter in aquatic animals compared to terrestrial animals. Near field sound energy is the dominant sound energy at a distance less than or equal to the wavelength.

The American Horseshoe crab, Limulus polyphemus, a species considered a phylogenetic relict, has been widely studied in its distribution in the United States due to its relevance in the fishing and biomedical industry. However, there is little information on the genetic status of the Mexican population which is relevant for the conservation of this endangered species. Here, using nuclear microsatellites markers, we evaluate the genetic diversity and structure of L. polyphemus in different localities of its Mexican distribution in the Yucatán Peninsula. A total of 103 individuals from four Mexican localities from the Gulf of Mexico (Champotón and Ría Celestún), northern coast of Yucatán (Yum Balam), to Caribbean coast (Sian Ka'an), were analyzed. Our results show low to moderately low values of different genetic diversity parameters and possible inbreeding processes for the two localities situated at the disttibution extremities (Champotón and Sian Ka'an). Also, we detected a strong genetic structure with two clusters, one pooling the Ría Celestún, Yum Balam and Sian Ka'an samples, and the other corresponding to Champotón, the most isolated population in the southern Gulf of Mexico. These patterns of genetic diversity could be related to anthropogenic activities (contamination, illegal fishing) that have impacted these populations for decades, resulting in a decrease in their populations.The observed genetic structure seems to be related to the dispersal behavior of the species and the circulation pattern on the Yucatán Shelf and the Campeche Bank. Our results highlighted the existence of two management units that should be considered in proposing management and conservation strategies for this species, especially focused on localities at critical risk. [ABSTRACT FROM AUTHOR]

Consideration of the full annual cycle population dynamics can provide useful insight for conservation efforts, but collecting data needed to estimate demographic parameters is often logistically difficult. For species that breed in remote areas, monitoring is often conducted during migratory stopover or at nonbreeding sites, and the recruitment rate of new breeding adults can be difficult to estimate directly. Here, we present an integrated population model that uses mark‐resight and count data to estimate survival probability, population growth rate, and recruitment rate for an Arctic‐breeding shorebird of conservation concern, the red knot (Calidris canutus rufa), from data collected during spring stopover in Delaware Bay, USA, from 2005 to 2018. At this site, red knots feed primarily on the eggs of spawning horseshoe crabs (Limulus polyphemus), a legally harvested species. We used this model to estimate the relationship between horseshoe crab abundance and red knot demographics, which informed a recent revision to the framework used to establish horseshoe crab harvest regulations. Our analysis indicates that the red knot population was most likely stable from 2005 to 2018 (average λ = 1.03, 95% credible interval [CRI]: 0.961, 1.15) despite low recruitment rates (average ρ = 0.088, 95% CRI: 0.012, 0.18). Adult survival probability was positively associated with horseshoe crab abundance in the same year (β = 0.35, 95% CRI: 0.09, 0.63), but we found no effect of horseshoe crab abundance two years previously on recruitment of new adults (β = −0.08, 95% CRI: −0.41, 0.38). Our approach demonstrates the utility of integrated population models for understanding population dynamics, even when data are only available from migratory stopover monitoring. [ABSTRACT FROM AUTHOR]

Durophagy arose in the Cambrian and greatly influenced the diversification of biomineralized defensive structures throughout the Phanerozoic. Spinose gnathobases on protopodites of Cambrian euarthropod limbs are considered key innovations for shell-crushing, yet few studies have demonstrated their effectiveness with biomechanical models. Here we present finite-element analysis models of two Cambrian trilobites with prominent gnathobases—Redlichia rex and Olenoides serratus—and compare these to the protopodites of the Cambrian euarthropod Sidneyia inexpectans and the modern American horseshoe crab, Limulus polyphemus. Results show that L. polyphemus, S. inexpectans and R. rex have broadly similar microstrain patterns, reflecting effective durophagous abilities. Conversely, low microstrain values across the O. serratus protopodite suggest that the elongate gnathobasic spines transferred minimal strain, implying that this species was less well-adapted to masticate hard prey. These results confirm that Cambrian euarthropods with transversely elongate protopodites bearing short, robust gnathobasic spines were likely durophages. Comparatively, taxa with shorter protopodites armed with long spines, such as O. serratus, were more likely restricted to a soft food diet. The prevalence of Cambrian gnathobase-bearing euarthropods and their various feeding specializations may have accelerated the development of complex trophic relationships within early animal ecosystems, especially the 'arms race' between predators and biomineralized prey. [ABSTRACT FROM AUTHOR]

Horseshoe crabs (Limulus polyphemus) exhibit ontogenetic and geographic variability in migratory patterns, yet the implications of movement on their resource use dynamics remain poorly understood. Here, we evaluate horseshoe crab resource use across ontogeny (instars 14–18 and adults), sex, seasons, and between two spatially distinct populations that exhibit different migratory patterns. Multi-tissue stable isotope analyses of carbon, nitrogen, and sulfur were used to examine (1) ontogenetic and sex-specific variability in the reliance of resource pools; (2) variation in isotopic niche breadth within and among populations; and (3) seasonal variability in resource use within juvenile life stages. We found evidence for subtle ontogenetic shifts in resource use, with increased contributions of phytoplankton with ontogeny, but all age groups predominantly relied on sedimentary organic matter (SOM) pools. Sex-specific differences in resource use were observed with SOM serving as the predominant source assimilated in males, while females exhibited a higher dependence on phytoplankton resource pools, indicating foraging or spatial preferences may be different between sexes. Low trophic niche overlap between adult and juvenile horseshoe crabs was evident, likely arising from differences in migratory patterns and size constraints. Within juveniles, no seasonal differences in resource use were observed, indicating that dietary patterns may remain static across temporal scales, consistent with limited dispersal of that life stage. Spatial differences in resource use were, however, observed between adult crabs likely reflecting the migratory strategies of different populations. Our results are consistent with previous evidence that horseshoe crabs are dietary generalists but provide novel insights into the linkages between movement and trophic patterns. [ABSTRACT FROM AUTHOR]

Pioneering molecular work on chelicerate visual system development in the horseshoe crab Limulus polyphemus surprised with the possibility that this process may not depend on the deeply conserved retinal determination function of Pax6 transcription factors. Genomic, transcriptomic, and developmental studies in spiders now reveal that the arthropod Pax6 homologs eyeless and twin of eyeless act as ancestral determinants of the ocular head segment in chelicerates, which clarifies deep gene regulatory and structural homologies and recommends more unified terminologies in the comparison of arthropod visual systems. Following this phylotypic stage, chelicerate visual system development differs fundamentally from other arthropods during the compartmentalization of the ocular segment in that eye and optic neuropil primordia originate independently from each other. Comparative analyses of this phase identified further gene regulatory homologies but also major differences, most notably the possibly compensatory replacement of Pax6 by Pax2 in lateral eye specification. Also see the video abstract here: https://youtu.be/Hdfr3z5kEXU [ABSTRACT FROM AUTHOR]

The largest aggregation of spawning American horseshoe crabs in the world occurs in Delaware Bay and supports one of the largest concentrations of shorebirds in the western hemisphere where the birds feed on horseshoe crab eggs during migration. Unregulated harvest in the 1990s is associated with the decline of shorebird populations using the bay, but corresponding baseline information on the horseshoe crab egg food supply that supported peak shorebird populations has been lacking.Past and current measurements of horseshoe crab eggs in the bay indicate that abundance in the 1980s was an order of magnitude greater (x̄ = 156,600/m2) than present‐day estimates (2015–2021 x̄ = 10,243/m2). An additional egg prevalence index, which characterizes the timing and magnitude of horseshoe crab egg output, revealed a similar pattern of higher prevalence in the 1980s (0.89, 95% confidence interval 0.81–0.94) compared with the recent 2015–2021 interval (0.52, 95% confidence interval 0.43–0.60).Declines of egg and shorebird abundance occurred shortly after horseshoe crab harvest reached its peak. Red knot aerial survey counts have stabilized at 30% of the baseline population while ruddy turnstone counts are 40% of baseline estimates. Initially these species were evenly distributed between the New Jersey and Delaware coasts but both species have trended toward predominately occupying New Jersey beaches.A lack of recovery of horseshoe crab egg and shorebird abundance suggests that horseshoe crab harvest management has stabilized populations but progress toward population recovery has been limited. Impacts from bycatch, the pharmaceutical industry and other potential population impacts must be better quantified and mitigated, if necessary, to promote the recovery of horseshoe crab populations. Measurements of horseshoe egg prevalence and abundance are essential metrics for tracking the progress toward management goals for improving shorebird habitat quality. [ABSTRACT FROM AUTHOR]

The lateral eyes of the horseshoe crab, Limulus polyphemus, are the largest compound eyes within recent Arthropoda. The cornea of these eyes contains hundreds of inward projecting elongated cuticular cones and concentrate light onto proximal photoreceptor cells. Although this visual system has been extensively studied before, the precise mechanism allowing vision has remained controversial. Correlating high‐resolution quantitative refractive index (RI) mapping and structural analysis, it is demonstrated how gradients of RI in the cornea stem from structural and compositional gradients in the cornea. In particular, these RI variations result from the chitin‐protein fibers architecture, heterogeneity in protein composition, and bromine doping, as well as spatial variation in water content resulting from matrix cross‐linking on the one hand and cuticle porosity on the other hand. Combining the realistic cornea structure and measured RI gradients with full‐wave optical modeling and ray tracing, it is revealed that the light collection mechanism switches from refraction‐based graded index (GRIN) optics at normal light incidence to combined GRIN and total internal reflection mechanism at high incident angles. The optical properties of the cornea are governed by different mechanisms at different hierarchical levels, demonstrating the remarkable versatility of arthropod cuticle. [ABSTRACT FROM AUTHOR]

The horseshoe crab Limulus polyphemus is one of few extant Limulus species, which date back to ∼250 million years ago under the conservation of a common Bauplan documented by fossil records. It possesses the only proteolytic blood‐coagulation and innate immunity system outside vertebrates and is a model organism for the study of the evolution and function of peptidases. The astacins are a family of metallopeptidases that share a central ∼200‐residue catalytic domain (CD), which is found in >1000 species across holozoans and, sporadically, bacteria. Here, the zymogen of an astacin from L. polyphemus was crystallized and its structure was solved. A 34‐residue, mostly unstructured pro‐peptide (PP) traverses, and thus blocks, the active‐site cleft of the CD in the opposite direction to a substrate. A central 'PP motif' (F35‐E‐G‐D‐I39) adopts a loop structure which positions Asp38 to bind the catalytic metal, replacing the solvent molecule required for catalysis in the mature enzyme according to an 'aspartate‐switch' mechanism. Maturation cleavage of the PP liberates the cleft and causes the rearrangement of an 'activation segment'. Moreover, the mature N‐terminus is repositioned to penetrate the CD moiety and is anchored to a buried 'family‐specific' glutamate. Overall, this mechanism of latency is reminiscent of that of the other three astacins with known zymogenic and mature structures, namely crayfish astacin, human meprin β and bacterial myroilysin, but each shows specific structural characteristics. Remarkably, myroilysin lacks the PP motif and employs a cysteine instead of the aspartate to block the catalytic metal. [ABSTRACT FROM AUTHOR]

The American horseshoe crab, Limulus polyphemus, is a member of the phylum Arthropoda, subphylum Chelicerata, and class Merostomata. Although there are four horseshoe crab species worldwide, the American horseshoe crab is primarily found in the Atlantic Ocean along the East Coast of North America. The species ranges from Maine to Mexico, but is absent between Texas in the United States and Tabasco in Mexico. They mainly inhabit estuarine areas; however, juveniles and adults can venture into the shallow oceanic environments. Embryo development occurs in the intertidal zone of sandy beaches. Sandy or muddy bottom habitats are necessary for burrowing and benthic feeding. This publication will cover their natural history, aquaculture techniques, common diseases, and their uses and markets.

Sexual reproduction represents a fundamental aspect of animal biology, but the diversity of reproductive strategies among early Paleozoic metazoans remains obscure. Direct evidence of reproductive strategies comes from exceptionally preserved egg masses in Cambrian and Ordovician euarthropods such as waptiids and trilobites, but anatomical or behavioral adaptations for mating in these taxa are all but unknown. We demonstrate the presence of functionally specialized appendages in the mid-Cambrian (Wuliuan) Burgess Shale trilobite Olenoides serratus. New material of O. serratus preserves significantly modified and reduced endopodites underneath the seventh thoracic and first pygidial tergites. Comparison with extant euarthropods indicates that these specialized limbs are functional analogs to claspers, which are used by sexually mature males to grasp females prior to or during mating. The claspers in O. serratus were most likely used by the male to hold onto the posterior pygidial spines of the female during amplex, similar to the strategy observed in the horseshoe crab Limulus polyphemus. The new appendicular data from O. serratus provide the first direct evidence for trilobite sexual dimorphism based on the non-biomineralized ventral anatomy. Our findings illuminate the reproductive biology of trilobites and indicate that complex mating behaviors observed in extant euarthropods originated during the Cambrian explosion. [ABSTRACT FROM AUTHOR]

The document titled "News from The Crustacean Society for January 2024" provides information on upcoming meetings and opportunities for members of The Crustacean Society (TCS). The TCS will be holding a mid-year summer meeting in Taipei, Taiwan from May 27 to June 1, 2024, and a winter meeting in Atlanta, GA, USA from January 3 to 7, 2025. The TCS also offers research fellowships, travel grants, and graduate studies fellowships to its members. Additionally, the document announces the winners of the 2023 TCS Photo Competition and pays tribute to two individuals who made significant contributions to the field of crustacean biology. [Extracted from the article]

Understanding factors that influence a species' distribution and abundance across the annual cycle is required for range-wide conservation. Thousands of imperiled red knots (Calidris cantus rufa) stop on Virginia's barrier islands each year to replenish fat during spring migration. We investigated the variation in red knot presence and flock size, the effects of prey on this variation, and factors influencing prey abundance on Virginia's barrier islands. We counted red knots and collected potential prey samples at randomly selected sites from 2007–2018 during a two-week period during early and peak migration. Core samples contained crustaceans (Orders Amphipoda and Calanoida), blue mussels (Mytilus edulis), coquina clams (Donax variabilis), and miscellaneous prey (horseshoe crab eggs (Limulus polyphemus), angel wing clams (Cyrtopleura costata), and other organisms (e.g., insect larvae, snails, worms)). Estimated red knot peak counts in Virginia during 21–27 May were highest in 2012 (11,959) and lowest in 2014 (2,857; 12-year peak migration x¯ = 7,175, SD = 2,869). Red knot and prey numbers varied across sampling periods and substrates (i.e., peat and sand). Red knots generally used sites with more prey. Miscellaneous prey (x¯ = 2401.00/m2, SE = 169.16) influenced red knot presence at a site early in migration, when we only sampled on peat banks. Coquina clams (x¯ = 1383.54/m2, SE = 125.32) and blue mussels (x¯ = 777.91/m2, SE = 259.31) affected red knot presence at a site during peak migration, when we sampled both substrates. Few relationships between prey and red knot flock size existed, suggesting that other unmeasured factors determined red knot numbers at occupied sites. Tide and mean daily water temperature affected prey abundance. Maximizing the diversity, availability, and abundance of prey for red knots on barrier islands requires management that encourages the presence of both sand and peat bank intertidal habitats. [ABSTRACT FROM AUTHOR]

Spiders are among the most varied terrestrial predators, with highly diverse morphology, ecology, and behavior. Morphological and molecular data have greatly contributed to advances in the phylogeny and evolutionary dynamics of spiders. Here, we performed comprehensive mitochondrial phylogenomics analysis on 78 mitochondrial genomes (mitogenomes) representing 29 families; of these, 23 species from eight families were newly generated. Mesothelae retained the same gene arrangement as the arthropod ancestor (Limulus polyphemus), while Opisthothelae showed extensive rearrangement, with 12 rearrangement types in transfer RNAs (tRNAs) and control region. Most spider tRNAs were extremely truncated and lacked typical dihydrouridine or TΨC arms, showing high tRNA structural diversity; in particular, trnS1 exhibited anticodon diversity across the phylogeny. The evolutionary rates of mitochondrial genes were potentially associated with gene rearrangement or truncated tRNAs. Both mitogenomic sequences and rearrangements possessed phylogenetic characteristics, providing a robust backbone for spider phylogeny, as previously reported. The monophyly of suborder, infraorder, retrolateral tibial apophysis clade, and families (except for Pisauridae) was separately supported, and high-level relationships were resolved as (Mesothelae, (Mygalomorphae, (Entelegynae, (Synspermiata, Hypochilidae)))). The phylogenetic positions of several families were also resolved (e.g., Eresidae, Oecobiidae and Titanoecidae). Two reconstructions of ancestral web type obtained almost identical results, indicating that the common ancestor of spiders likely foraged using a silk-lined burrow. This study, the largest mitochondrial phylogenomics analysis of spiders to date, highlights the usefulness of mitogenomic data not only for providing efficient phylogenetic signals for spider phylogeny, but also for characterizing trait diversification in spider evolution. [ABSTRACT FROM AUTHOR]

Glyphosate is the most used herbicide in the world. Unfortunately, contamination of water bodies by this herbicide has been reported. A severe concern has been triggered given its detrimental impact on the environment and wildlife. The American horseshoe crab (Limulus polyphemus) is a benthic arthropod that inhabits the Yucatan Peninsula in Southeast Mexico. This study evaluates the glyphosate concentration in 34 recently dead specimens of L. polyphemus from four localities of the Ria Lagartos Biosphere Reserve in Yucatan, Mexico. The analysis was carried out using High-Performance Liquid Chromatography coupled with a Triple Quadrupole Mass Spectrometer. All the samples showed residues of glyphosate in the range from 0.08 to 2.38 ng g−1. These records constitute the first evidence of glyphosate bioaccumulation in this species. Although the scope might be limited, the results demonstrate a potentially prejudicial exposition of the marine biota to glyphosate-based herbicides, given its use in the region. [ABSTRACT FROM AUTHOR]

Horseshoe crabs are xiphosuran chelicerates, the sister group to arachnids. As such, they are important for understanding the most recent common ancestor of Euchelicerata and the evolution and diversification of Arthropoda. Limulus polyphemus is the most investigated of the four extant species of horseshoe crabs, and the structure and function of its visual system have long been a major focus of studies critical for understanding the evolution of visual systems in arthropods. Likewise, studies of genes encoding Limulus opsins, the protein component of the visual pigments, are critical for understanding opsin evolution and diversification among chelicerates, where knowledge of opsins is limited, and more broadly among arthropods. In the present study, we sequenced and assembled a high quality nuclear genomic sequence of L. polyphemus and used these data to annotate the full repertoire of Limulus opsins. We conducted a detailed phylogenetic analysis of Limulus opsins, including using gene structure and synteny information to identify relationships among different opsin classes. We used our phylogeny to identify significant genomic events that shaped opsin evolution and therefore the visual system of Limulus We also describe the tissue expression patterns of the 18 opsins identified and show that transcripts encoding a number, including a peropsin, are present throughout the central nervous system. In addition to significantly extending our understanding of photosensitivity in Limulus and providing critical insight into the genomic evolution of horseshoe crab opsins, this work provides a valuable genomic resource for addressing myriad questions related to xiphosuran physiology and arthropod evolution.

Sea scorpions (Euchelicerata: Eurypterida) explored extreme limits of the aquatic euchelicerate body plan, such that the group contains the largest known marine euarthropods. Inferences on eurypterid life modes, in particular walking and eating, are commonly made by comparing the group with horseshoe crabs (Euchelicerata: Xiphosura). However, no models have been presented to test these hypotheses. Here, we reconstruct prosomal appendages of two exceptionally well-preserved eurypterids, Eurypterus tetragonophthalmus and Pentecopterus decorahensis , and model the flexure and extension of these appendages kinematically in three dimensions (3D). We compare these models with 3D kinematic models of Limulus polyphemus prosomal appendages. This comparison highlights that the examined eurypterid prosomal appendages could not have moved prey items effectively to the gnathal edges and would therefore not have emulated the motion of an L. polyphemus walking leg. It seems that these eurypterid appendages were used primarily to walk or grab prey, and other appendages would have moved prey for mastication. Such 3D kinematic modelling highlights how eurypterid appendage morphologies placed substantial limits on their function, suggesting a high degree of specialization, especially when compared with horseshoe crabs. Such three-dimensional kinematic modelling of these extinct groups therefore presents an innovative approach to understanding the position of these animals within their respective palaeoecosystems. [ABSTRACT FROM AUTHOR]

Loggerhead sea turtles (Caretta caretta) are opportunistic carnivores that feed primarily on benthic invertebrates and fish. Sea turtle rehabilitation requires provision of a species‐specific, balanced diet that supplies nutrition similar to that of a wild diet; this can be challenging because free‐ranging loggerheads' diets vary depending on their life stage and geographic location, with predominant prey species dictated by local availability. The goal of this study was to better understand the nutritional needs of subadult and adult loggerheads in rehabilitation. This was accomplished by conducting a retrospective survey of stomach contents identified during gross necropsy of 153 deceased loggerheads that stranded in coastal Georgia, USA. A total of 288 different forage items were identified; the most frequently observed prey items belong to the subphylum Crustacea (N = 131), followed by bony fish (Osteichthyes; N = 45), gastropod mollusks (N = 40), bivalve mollusks (N = 23), and Atlantic horseshoe crabs (Limulus polyphemus; N = 15). The proportions of certain prey items differed significantly with turtle size; adult turtles ate proportionately more gastropods (p = 0.001), and subadults ate proportionately more fish (p = 0.01). Stomach contents information was used to determine common local prey items (blue crab, cannonball jellyfish, horseshoe crab, whelk), which were evaluated for nutritional content. Additionally, we compared hematology and plasma biochemistry profiles (including proteins, trace minerals, and vitamins) between four cohorts of loggerhead turtles, including free‐ranging subadults and adults, nesting females, and loggerheads undergoing rehabilitation. This information was applied to inform a regionally specific, formulated diet for tube feeding, and a supplement containing vitamins and minerals for captive loggerheads, to more closely approximate the nutritional content of their natural diet. Assessing the regional and temporal variability in loggerhead diets is an important component in their effective conservation because resultant data can be used to help understand the impacts of environmental perturbations on benthic food webs. [ABSTRACT FROM AUTHOR]

In 2018 we evaluated at 48 h and 96 h, the gene expression profile of larvae of Limulus polyphemus exposed to 10% and 100% of water-accommodated fraction (WAF) of light crude oil (API 35), and 10% and 100% of a chemically enhanced WAF (CEWAF) with the dispersant Nokomis 3-F4® in a static-acute (96 h) bioassay. Alkanes and PAHs concentrations were higher in CEWAF than in WAF stock solutions. Under the proved conditions, the expression profile of genes associated to detoxification processes (glutathione S-transferase and glutathione peroxidase), stress (heat shock protein), innate immunity (tumor necrosis factor receptor-associated factor 4 traf4), cell death (apoptosis inhibitor 5) and DNA repairing (E3 ubiquitin protein ligase), showed a deregulation at 48 h followed by an upregulation at 96 h, with exception of glutathione peroxidase, heat shock protein and innate immunity that remained low in CEWAF. In conclusion, by using genes that have been proposed as biomarkers to pollutants exposure, L. polyphemus larvae showed an early activation of genes related to the immune system, antioxidant, heat shock and NER. [ABSTRACT FROM AUTHOR]

An exceptionally preserved specimen of the horseshoe crab Euproops danae (Xiphosurida, Belinurina) in a siderite concretion from the Carboniferous (Upper Pennsylvanian, Virgilian) Lawrence Formation, Kansas, shows anatomical details of the prosomal musculature. The extrinsic appendicular muscles are comparable to those of Limulus polyphemus (the modern American horseshoe crab), demonstrating anatomical conservatism within Xiphosurida that spans two morphologically disparate subgroups, Belinurina and Limulina. The three‐dimensional preservation of muscles highlights how siderite concretion fossils (including those of the Mazon Creek Konservat‐Lagerstätte) have better preservational fidelity than previously realized and the potential to reveal new anatomical information, especially with regard to the labile tissues of euarthropods. [ABSTRACT FROM AUTHOR]

This document provides summaries of four different articles related to fisheries. The first article discusses the use of sterile fish for enhancing sport fisheries in regions with few native sport fish. The second article describes the behavior and movement patterns of Lake Trout in the Great Lakes, providing valuable information for the management of fish populations. The third article applies a catch multiple survey analysis to estimate the population of Atlantic horseshoe crabs in the Delaware Bay, which is important for harvest management and the needs of migratory birds. The fourth article focuses on the population status and recovery of Yelloweye Rockfish in the Puget Sound, using data-limited fishery assessment methods to estimate their exploitation history and current status. [Extracted from the article]

Identifying mechanisms that underpin animal migration patterns and examining variability in space use within populations is crucial for understanding population dynamics and management implications. In this study, we quantified the migration rates, seasonal changes in migratory connectivity, and residency across population demographics (age and sex) to understand the proximate cues of migration timing in American horseshoe crabs (Limulus polyphemus). Juvenile (n = 25) and adult (n = 70) horseshoe crabs were tracked with acoustic telemetry techniques for a 3‐yr period in Moriches Bay, NY. Connectivity metrics and residency probability were quantified through spatial network analysis and empirically derived Markov Chain models (EDMC), respectively. The migratory probability of adult horseshoe crabs between Moriches Bay and the Atlantic Ocean was estimated to be 41.0% (95% CI: 34.0–59.8); in contrast, only 8% (95% CI: 1.2–31.6) of juveniles migrated into the ocean. Migration timing was influenced by the interaction of photoperiod and temperature, revealing seasonal differences in migration timing and a 50% narrower range of photoperiod and temperature over which fall migrations occurred compared to spring. Sex‐specific differences in space use and connectivity within each season were largely absent; however, centralized habitats were important for maintaining connectivity across all seasons. EDMC results revealed that when standardized to the number of horseshoe crab detections on each receiver, the centrally located habitats in Moriches Bay and Inlet accounted for >50% of the total relative residency probability within most seasons, indicating these areas may be preferred by adult horseshoe crabs. Ontogenetic differences in maximum spatial extent, space use, and connectivity were observed in the bay, as juveniles exhibited lower linkages between locations (n = 4) relative to adults (n = 13) during the same temporal period. Our work highlights the application of novel quantitative approaches for addressing the movement dynamics of horseshoe crabs that can be readily applied to other taxa in the context of wildlife conservation. [ABSTRACT FROM AUTHOR]