Horseshoe Crab Carcinoscorpius Rotundicauda Research Articles

Modeling potential habitats of threatened horseshoe crabs in Indo-Pacific Asia: Suggestions for conservation management

Identifying critical habitats of threatened marine species is key to area-based management measures, while it can be of great challenge for those species that distribute continentally. Asian horseshoe crabs, including tri-spine horseshoe crab Tachypleus tridentatus, coastal horseshoe crab T. gigas, and mangrove horseshoe crab Carcinoscorpius rotundicauda, are globally threatened marine chelicerates, which are largely distributed in developing countries in Indo-Pacific Asia with limited baseline information. Here, we performed the maximum entropy model (MaxEnt), a widely used correlative species distribution model, to explore potential habitats of the Asian horseshoe crabs. Presence-only data of the adult Asian horseshoe crabs and the seven sea benthic environmental predictors, which included temperature, salinity, chlorophyll a concentration, dissolved oxygen, current velocity, bathymetry, and slope, were input into the MaxEnt. The Cloglog output format was adopted to estimate the presence probability of these three species under species-specific regularization multipliers. Our results showed that all three species have potential habitats in Southeast Asia. The range of potential habitats is the most widespread for T. tridentatus, but the most restricted for T. gigas. Bathymetry, temperature, and chlorophyll a concentration are the main contributing environmental predictors for the projected distribution of T. tridentatus, while for T. gigas and C. rotundicauda, temperature and bathymetry have contributed the most. Temperature of the potential habitats is the lowest for T. tridentatus (25.6 ± 4.4 °C), compared to the more tropically distributed T. gigas and C. rotundicauda (around 29 °C). Core habitats of the estuary-bound C. rotundicauda have shallower bathymetry of 5.8 ± 3.5 m in depth. Overall, Asian horseshoe crab species share similar niches, with the common characteristics of shallow bathymetry (<15 m in depth), high temperature (>25 °C), and relatively higher chlorophyll a concentration in coastal waters. We conclude that the projected habitats serve as a critical reference for the conservation management of threatened Asian horseshoe crabs under extensive baseline gaps. Generalized conservation strategies are suggested, depending on the sufficiency of baseline data, to facilitate the formation of specific decision-making.

Central composite design‐based response surface methodology for optimization of tetrodotoxin extraction from the horseshoe crab Carcinoscorpius rotundicauda

AbstractTetrodotoxin analogues (TTXs) used in research and development were originated from biological sources for the last decades. Among TTXs‐bearing aquatic animals, horseshoe crab Carcinoscorpius rotundicauda from Vietnam's Coast was reported to contain a high level of TTXs, indicating a promising source for extraction and purification of TTXs. In this work, horseshoe crab C. rotundicauda collected from Can Gio Coast, Vietnam was used for TTX extraction using homogenization‐assisted method with acetic acid solvent. The extraction process was analysed and optimized by single‐factor investigation and response surface methodology (RSM). Single‐factor investigation pointed out that the optimal conditions for TTX recovery yield from C. rotundicauda's soft tissues were homogenization time of 20 min, acetic acid concentration of 1.0%, solvent/matrix ratio of 4 mL/g, extraction temperature of 70°C, extraction time of 30 min and number of extraction of two times. The most significant factors including acetic acid concentration, solvent/matrix ratio and extraction temperature were utilized for constructing the RSM model to predict TTX recovery yield. The maximal TTX recovery yield predicted from RSM model was 97.3% under solvent/matrix ratio of 4 mL/g, extraction temperature of 70°C and acetic acid concentration of 1% (v/v). The RSM model displayed a high stability and precision for prediction of TTX recovery yield from experiments of 1–10 kg C. rotundicauda's soft tissues/batch extractions producing low errors (−1.95% to 1.85%). TTXs in C. rotundicauda's soft tissues were elucidated by HPLC‐MS/MS, revealing the presence of three analogues TTX, 4epi‐TTX and Anh‐TTX with their contents of 43.02, 22.54 and 45.07 μg/g, respectively.

Transcriptomic Signature of Horseshoe Crab Carcinoscorpius rotundicauda Hemocytes' Response to Lipopolysaccharides.

Carcinoscorpius rotundicauda (C. rotundicauda) is one of the four species of horseshoe crabs (HSCs). The HSC hemocytes store defense molecules that are released upon encountering invading pathogens. The HSCs rely on this innate immunity to continue its existence as a living fossil for more than 480 million years. To gain insight into the innate mechanisms involved, transcriptomic analysis was performed on isolated C. rotundicauda hemocytes challenged with lipopolysaccharides (LPS), the main components of the outer cell membrane of gram-negative bacteria. RNA-sequencing with Illumina HiSeq platform resulted in 232,628,086 and 245,448,176 raw reads corresponding to 190,326,253 and 201,180,020 high-quality mappable reads from control and LPS-stimulated hemocytes, respectively. Following LPS-stimulation, 79 genes were significantly upregulated and 265 genes were downregulated. The differentially expressed genes (DEGs) were related to multiple immune functional categories and pathways such as those of the cytoskeleton, Toll and Imd, apoptosis, MAP kinase (MAPK), inositol phosphate metabolism, phagosome, leucocyte endothelial migration, and gram-negative bacterial infection, among others. This study provides important information about the mechanisms of response to LPS, which is relevant for the understanding the HSCs' immune response.

Plant produced endotoxin binding recombinant proteins effectively remove endotoxins from protein samples

Lipopolysaccharides (LPS) are highly toxic compounds, even at a trace amount. When recombinant proteins are produced in E. coli, it is inevitable that LPS contaminates. However, LPS removal is still technically challenging and costly due to the high degree of solubility in a wide range of solvents. In this study, we explored the possibility of using the N-terminal region containing cysteine-rich, EGF-like, and sushi1–3 domains (CES3) of Factor C from the horseshoe crab Carcinoscorpius rotundicauda to develop a platform to remove LPS from recombinant proteins. We expressed CES3 as part of a recombinant protein, BiP:NT:CBM3:SUMO:CES3:His:HDEL, in Nicotiana benthamiana and found that purified or microcrystalline cellulose (MCC) bead-immobilised CES3 showed strong binding to LPS-containing E. coli. To produce CES3:CBM3 in an LPS-free environment, we generated Arabidopsis transgenic plants harbouring a recombinant gene, BiP:NT:SUMO:CES3:CBM3:HDEL, and found that transgenic plants mainly produce CES3:CBM3:His:HDEL, a truncated version of BiP:NT:SUMO:CES3:CBM3:HDEL via endogenous protease-mediated proteolytic processing in vivo. CES3:CBM3:HDEL purified from Arabidopsis plant extracts and immobilised onto MCC beads removed LPS contamination from protein samples. We propose that the CES3:CBM3 fusion protein produced in plants and immobilised on MCC beads can be a robust and easy platform for LPS removal from recombinant proteins.

A preliminary investigation of epibiotic macrofauna on the mangrove horseshoe crab Carcinoscorpius rotundicauda (Latreille, 1802) in Singapore

ABSTRACT Horseshoe crabs may act as mobile substrata for communities of sessile marine organisms on intertidal mudflats. In Singapore, the mangrove horseshoe crabs, Carcinoscorpius rotundicauda (Latreille, 1802) were surveyed for the diversity of epibiotic macrofauna. The most common epibiota observed was the barnacles belonging to Amphibalanus spp., along with other organisms: slipper snails Crepidula walshi and anemones (species undetermined). We also report the first account of an invasive American brackish mussel, Mytella strigata on C. rotundicauda in Singapore. Adult horseshoe crabs, particularly the males, have the highest prevalence and abundance of epibionts. A distinct distribution of epibionts was observed across horseshoe crab gender, age class and between the dorsal and ventral planes. Barnacles were found to be the dominant fouling on dorsal planes, while M. strigata and slipper snails occurred mainly on the ventral planes.

Antibacterial and Antifouling Properties of the Horseshoe Crab Carcinoscorpius rotundicauda.

&lt;b&gt;Background and Objective:&lt;/b&gt; Horseshoe crabs are widely used in both traditional and modern pharmaceutical applications. Most of the previous studies on horseshoe crabs focused on their blood which contains hemolymph and amoebocyte lysate. This study aimed to determine the potential antibacterial and antifouling properties of different extracts from the carapace and the book gills of &lt;i&gt;Carcinoscorpius rotundicauda&lt;/i&gt;. &lt;b&gt;Materials and Methods:&lt;/b&gt; The crude extracts were subjected to the bioactivity tests using the disc-diffusion and the inhibition of biofilm-formation measurement assays, for both the antibacterial and antifouling activities respectively. &lt;b&gt;Results:&lt;/b&gt; The results obtained indicated that the carapace extracts had stronger antibacterial and antifouling effects compared to the book gills extracts. Extracts obtained from the male displayed more activity compared to the extracts from the female with a few exceptions. Methanol and acetone carapace crude extracts showed the best overall performance. A sterol compound was isolated from the carapace acetone extracts of the male of &lt;i&gt;C. rotundicauda&lt;/i&gt;. However, the compound did not display strong activity compared to the crude extract. The compound might be contributing to the observed activity with other components through a synergistic effect. &lt;b&gt;Conclusion:&lt;/b&gt; The presence of antibacterial and antifouling activities in the carapace and book gills extracts could be added to the complexity of the defence mechanisms of horseshoe crabs. The results of this study, therefore, may contribute to the knowledge of the defence mechanisms of &lt;i&gt;C. rotundicauda&lt;/i&gt;. Further research is needed to determine the bioactivities of other parts of the animal and to explore their potential applications.

Horseshoe crab genomes reveal the evolution of genes and microRNAs after three rounds of whole genome duplication

Whole genome duplication (WGD) has occurred in relatively few sexually reproducing invertebrates. Consequently, the WGD that occurred in the common ancestor of horseshoe crabs ~135 million years ago provides a rare opportunity to decipher the evolutionary consequences of a duplicated invertebrate genome. Here, we present a high-quality genome assembly for the mangrove horseshoe crab Carcinoscorpius rotundicauda (1.7 Gb, N50 = 90.2 Mb, with 89.8% sequences anchored to 16 pseudomolecules, 2n = 32), and a resequenced genome of the tri-spine horseshoe crab Tachypleus tridentatus (1.7 Gb, N50 = 109.7 Mb). Analyses of gene families, microRNAs, and synteny show that horseshoe crabs have undergone three rounds (3R) of WGD. Comparison of C. rotundicauda and T. tridentatus genomes from populations from several geographic locations further elucidates the diverse fates of both coding and noncoding genes. Together, the present study represents a cornerstone for improving our understanding of invertebrate WGD events on the evolutionary fates of genes and microRNAs, at both the individual and population level. We also provide improved genomic resources for horseshoe crabs, of applied value for breeding programs and conservation of this fascinating and unusual invertebrate lineage.

Chromosome-level assembly of the horseshoe crab genome provides insights into its genome evolution

The evolutionary history of horseshoe crabs, spanning approximately 500 million years, is characterized by remarkable morphological stasis and a low species diversity with only four extant species. Here we report a chromosome-level genome assembly for the mangrove horseshoe crab (Carcinoscorpius rotundicauda) using PacBio reads and Hi-C data. The assembly spans 1.67 Gb with contig N50 of 7.8 Mb and 98% of the genome assigned to 16 chromosomes. The genome contains five Hox clusters with 34 Hox genes, the highest number reported in any invertebrate. Detailed analysis of the genome provides evidence that suggests three rounds of whole-genome duplication (WGD), raising questions about the relationship between WGD and species radiation. Several gene families, particularly those involved in innate immunity, have undergone extensive tandem duplication. These expanded gene families may be important components of the innate immune system of horseshoe crabs, whose amebocyte lysate is a sensitive agent for detecting endotoxin contamination.

Influence of environmental variability on the body condition of the mangrove horseshoe crab Carcinoscorpius rotundicauda from Banyuasin Estuarine, South Sumatra, Indonesia

The body conditions indices were useful to determine an individual's well-being, and favorable food availability indicating a good environmental condition. The conditions of the mangrove horseshoe crab (Carcinoscorpius rotundicauda) might be related to several environmental parameters. The study's aim was to analyze the key environmental parameters affecting the body condition of C. rotundicauda found in Banyuasin Estuary Waters. The sampling was conducted in July 2019 in Banyuasin Estuary Waters. The data of weight and prosomal width for C. rotundicauda were used to estimate the body conditions indices (relative condition factor). While the environmental parameters data were recorded for each sampling site. The backward stepwise regression was used to determine the key environmental parameters affecting the body condition indices. The best-fitted model (adjusted R2 = 91.9%; F = 60.102; p &lt; 0.05) indicated several environmental parameters (salinity, pH, seafloor temperature, clay and silt contents) significantly affecting the body condition indices. Changes in the key environmental parameters could generate changes in the availability of favorable food for C. rotundicauda. The result also can be used as baseline data for determining the marine conservation areas as well as horseshoe crab management plan.

Population study of the mangrove horseshoe crab Carcinoscorpius rotundicauda (Lattreille 1802) in Kuala Tungkal, Tanjung Jabung Barat, Jambi, Indonesia

Population and morphological data of the mangrove horseshoe crab Carcinoscorpius rotundicauda was collected off the coast of Kuala Tungkal, Tanjung Jabung Barat, Jambi, Indonesia from November 2011 to January 2012. The study site was divided into two areas: Station I (Parit 10) and Station II (Boyar), where the water was 4–8 m and 15–25 m deep, respectively. Four belt transects (5 m × 1000 m), 100 m apart, were set parallel with the shoreline in each area. Shrimp nets (5 m × 20 m), towed along the seabed by a fishing boat were used to capture crabs. The crabs were enumerated and measurements were taken of their carapace size and body weight. Abiotic factors were also measured, including water temperature, salinity, depth, and visibility. The population density of the crabs was 0.62 ± 0.23 individuals/100 m2, and their distribution pattern was random. We found correlations between depth, visibility, and crab density only at Station I.

The morphometric variability of the mangrove horseshoe crab (Carcinoscorpius rotundicauda) from Banyuasin estuarine of South Sumatra, Indonesia

The allometric analysis was applied to record the morphometric variability in different sex of the mangrove horseshoe crab (Carcinoscorpius rotundicauda) collected from Banyuasin estuarine of South Sumatra, Indonesia during July 2019. The body parameter measurement of body weight (BW), total length (TL), prosoma width (PW), carapace length (CL), and telson length (TL) were recorded then pooled refer to the sex. The differences in each body parameter between the males and females were observed through the Student's t-test. The length/width-weight relationship for both sexes was analyzed using the power equations while the width/length-length relationship was analyzed using the linear equations. The Student’s t-test was used to determine significant differences from the isometric value. The females of C. rotundicauda were significantly heavier and larger in size than males except for telson length (p &lt; 0.05). Both sexes revealed a negative allometric growth for the TL/CL-BW relationships while the males indicated a negative allometric growth but the females indicated an isometric growth for the PW-BW relationships. Both sexes also indicated the isometric growth for the CL-PW relationship. The TL-PW/TEL relationship also revealed a negative allometric growth for both sexes. The study results were expected to be used as baseline data for the horseshoe crab management plan and action.

Toxin and toxicity identification of mangrove horseshoe crab Carcinoscorpius rotundicauda collected from South China

The presence of paralytic shellfish poisoning (PSP), diarrhetic Shellfish Poisoning (DSP), tetrodotoxin (TTX) and its analogues (11-oxoTTX, 4.9-anhydro-11-oxoTTX, 4.9-anhydroTTX, 5-deoxyTTX, 5.11-dideoxyTTX, 5.6.11-trideoxyTTX and 4.9-anhydro-5.6.11-trideoxy TTX) were initially investigated in Carcinoscorpius rotundicauda collected from south China with Liquid chromatography-tandem mass spectrometry (LC–MS–MS) and mouse bioassay. The TTX toxicity was 10.8 ± 3.9 MU/g muscle, 6.3 ± 0.6 MU/g viscera and 6.3 ± 0.6 MU/g eggs in mean value. Merely dcGTX2 and dcSTX were detected in ten Specimens, ranging from 0.01 to 0.77 μg/g. Analyses suggested that these Carcinoscorpius rotundicauda contain TTX and its analogues as the major toxin and PSPs as the minor, respectively. Besides, no DSPs were found.

基于MAXENT模型评估北部湾潮间带中国鲎和圆尾鲎稚鲎的潜在地理分布及种群保育对策

PDF HTML阅读 XML下载 导出引用 引用提醒 基于MAXENT模型评估北部湾潮间带中国鲎和圆尾鲎稚鲎的潜在地理分布及种群保育对策 DOI: 10.5846/stxb201805161079 作者: 作者单位: 1水产科学国家级实验教学示范中心(上海海洋大学) 201306 2海洋生物科学国际联合研究中心(上海海洋大学)，中国科学技术部 201306 3上海水产养殖工程技术研究中心(上海海洋大学) 201306,广西壮族自治区水产科学研究院,天津市一瑞生物工程有限公司,上海海洋大学信息学院,1水产科学国家级实验教学示范中心(上海海洋大学) 201306 2海洋生物科学国际联合研究中心(上海海洋大学)，中国科学技术部 201306 3上海水产养殖工程技术研究中心(上海海洋大学) 201306,1水产科学国家级实验教学示范中心(上海海洋大学) 201306 2海洋生物科学国际联合研究中心(上海海洋大学)，中国科学技术部 201306 3上海水产养殖工程技术研究中心(上海海洋大学) 201306 作者简介: 通讯作者: 中图分类号: 基金项目: 香港海洋公园保育基金（OT03.1617）；2017北海市"十三五"海洋经济创新发展示范项目（Bhsfs006） Prediction of potential distribution areas of Chinese horseshoe crab and mangrove horseshoe crab in the Beibu Gulf of Guangxi based on MAXENT model and their population conservation strategies Author: Affiliation: National Demonstration Center for Experimental Fisheries Science Education,Shanghai Ocean University,Shanghai,,,,National Demonstration Center for Experimental Fisheries Science Education,Shanghai Ocean University,Shanghai,National Demonstration Center for Experimental Fisheries Science Education,Shanghai Ocean University,Shanghai Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:鲎具有极高的经济价值和科研意义。近年来由于过度捕捞和栖息地受损等原因，亚洲鲎种群数量正急剧下降。鲎漫长的生命周期使得鲎资源的保护和增殖迫在眉睫。生态位模型已经广泛应用于物种的潜在地理分布预测。基于实地调研数据和公开发表的北部湾中国海域中国鲎和圆尾鲎地理分布数据，运用MAXENT模型得到中国鲎和圆尾鲎在广西北部湾（中国部分）的栖息地适宜度指数（Habitat suitability index，HSI），确定了这两种稚鲎在北部湾中国海域潜在适生区。模型分析结果表明，潮间带坡度和地形指数是影响中国鲎分布的主要环境因子，而潮间带底质的有机物含量和植被指数是影响圆尾鲎分布的主要环境因子，根据研究结果建议在两种稚鲎适生区建立保护区，进行人工放流稚鲎，加强对海草和红树林的生态建设，进而促进鲎资源种群恢复和发展。 Abstract:Horseshoe crab has high economic and scientific values. In recent years, because of overfishing and habitat degradation, the population of horseshoe crabs in China is decreasing rapidly. However, their long life cycle makes it extremely urgent to protect horseshoe crabs. Ecological niche models have been widely applied to predict the potential geographic distribution of species. The habitat suitability index of the Chinese horseshoe crab Tachypleus tridentatus and mangrove horseshoe crab Carcinoscorpius rotundicauda in the Beibu Gulf (Chinese part) was determined by using the maximum entropy model and the distribution of habitat suitability of the two types of juvenile horseshoe crab in the Beibu Gulf was determined based on field survey data and published data on the geographical distribution of two horseshoe crab species in the Beibu Gulf. The model analysis results showed that the slope of the intertidal zone and topographic index were the main environmental factors affecting the distribution of the Chinese horseshoe crab, while the organic content and vegetation index of intertidal sediment were the main environmental factors affecting the distribution of the mangrove horseshoe crab. According to the results, to promote the recovery and development of horseshoe crab resources, protected areas should be established, artificial release of juvenile horseshoe crabs in habitat suitability areas of horseshoe crab should be conducted, and the ecological construction of seagrasses and mangroves in these areas should be strengthened. 参考文献 相似文献 引证文献

Tracked mangrove horseshoe crab Carcinoscorpius rotundicauda remain resident in a tropical estuary

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 17:235-245 (2012) - DOI: https://doi.org/10.3354/ab00477 Tracked mangrove horseshoe crab Carcinoscorpius rotundicauda remain resident in a tropical estuary Lesley Cartwright-Taylor*, Harn Hua Ng, Ter Yang Goh Nature Society (Singapore) (NSS), 510 Geylang Road, #02-05 The Sunflower, Singapore 389466 *Email: cartwrighttaylor@gmail.com ABSTRACT: Mangrove horseshoe crab Carcinoscorpius rotundicauda were tracked for 6 mo in the tropics using acoustic telemetry to determine whether they either show homing behaviour, remain near the site of capture, or travel to the open sea. Twelve adult horseshoe crabs were caught on the Mandai mudflats at Kranji and acoustic telemetry transmitters attached. Six acoustic receivers were deployed suspended from floating fish farm platforms ~1 km apart along the Strait of Johor, an estuary off the north coast of Singapore. Four individuals, 2 of each sex, were used in each of 3 tests: 4 crabs were released at the site of capture, 4 were released at a second site ~5.7 km away to determine if they exhibited homing, and 4 were caught along the muddy beach at the second site, tagged and released into deep water under one of the receivers. Although there were gaps in detection, 11 of 12 crabs were located intermittently within ~6 km of the point of release. One crab disappeared after 5 d. Homing was not exhibited, and the crabs were detected within the estuary for 6 mo. We concluded that the crabs in the tropical estuary, where there are no seasons or marked changes in water temperature, showed no tendency to travel out to sea and did not exhibit homing behaviour or any synchronized movement pattern to deeper waters. KEY WORDS: Mangrove horseshoe crab · Telemetry · Homing · Movement · Tropics Full text in pdf format PreviousNextCite this article as: Cartwright-Taylor L, Ng HH, Goh TY (2012) Tracked mangrove horseshoe crab Carcinoscorpius rotundicauda remain resident in a tropical estuary. Aquat Biol 17:235-245. https://doi.org/10.3354/ab00477 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 17, No. 3. Online publication date: December 13, 2012 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2012 Inter-Research.

Follow-up study on population structure and breeding pattern of the mangrove horseshoe crab Carcinoscorpius rotundicauda in Singapore

In 2009 Cartwright-Taylor et al. (2009; Aquat Biol 8:61-69) published a paper show- ing the monthly changes in population structure and breeding pattern of the mangrove horseshoe crab Carcinoscorpius rotundicauda over a 1 yr period at the Mandai mud-flats at Kranji in Singa- pore. Although breeding is thought to be year-round, our work demonstrated that the proportion of juveniles in different size groups varied each month, with recruitment into the smallest size classes from November to March with a corresponding decrease in the proportion of adults, and into larger size classes from March to July coupled with an increasing proportion of adults, sug- gesting periods of high and low breeding activity through the year. Follow-up data, collected for a further 3 yr to determine if this pattern was maintained, indicate that this indeed is a feature of the population. Each January a high proportion of the small juveniles was found consistently in the population, while each July the population was dominated consistently by adults with some large juveniles. Mean incremental growth rate at ecdysis (36%) from a further 10 ind. confirmed growth rate findings in the first year. The male:female ratios also confirmed findings from the first year with little change from 1 in the sex ratios for the 3 follow-up yr, suggesting mating activity is not strongly seasonal, as occurs in temperate climates. Pairs in amplexus were seen year-round, but the numbers varied from month to month with no apparent seasonal pattern.

Intraspecific shape variation in horseshoe crabs: The importance of sexual and natural selection for local adaptation

A morphometric analysis of the body shape of three species of horseshoe crabs was undertaken in order to infer the importance of natural and sexual selection. It was expected that natural selection would be most intense, leading to highest regional differentiation, in the American species Limulus polyphemus, which has the largest climatic differences between different populations. Local adaptation driven by sexual selection was expected in males but not females because horseshoe crab mating behaviour leads to competition between males, but not between females. Three hundred fifty-nine horseshoe crabs from nine populations, representing three species, were analyzed using a digitizer to position sixty morphometric landmarks in a three-dimensional space. Discriminant analysis revealed strong regional structuring within a species, which suggests strong philopatry, and showed the existence of geographically-based intraspecific variation. An admixture analysis showed regional intraspecific differentiation for males and females of L. polyphemus and males of the Asian horseshoe crab Carcinoscorpius rotundicauda, but not for females of C. rotundicauda and another Asian horseshoe crab, Tachypleus gigas. Differences in shape variation between sexes were tested with F-tests, which showed lower intrapopulation morphometric variation in males than females. These results indicate a lower degree of local adaptation on body shape in C. rotundicauda and T. gigas than in L. polyphemus and a lower degree of local adaptation in females than in males.

Population structure and breeding pattern of the mangrove horseshoe crab Carcinoscorpius rotundicauda in Singapore

The first year-long survey of the mangrove horseshoe crab Carcinoscorpius rotundi- cauda was conducted at the Mandai mudflats at Kranji in Singapore to determine if breeding is year round or seasonal and to provide qualitative and quantitative baseline data to monitor the health of the population. At spring tide from September 2007 to July 2008, volunteers collected horseshoe crabs along the exposed mudflats as the tide receded. The carapace width was measured, and the sex and breeding status of each individual were determined. The proportion of juveniles in different size groups varied in each month. In November and January, 25 and 30%, respectively, were 2 to 3 cm in width, while in June and July, 8 and 4%, respectively, were in this size group. The size cohorts showed recruitment to the smallest size classes from November to March and recruitment to the larger size classes from March to July. Juveniles less than 2 cm were not found in June, suggesting that there may be a rest period of low or no breeding activity from May to July resulting in none of the smallest sizes mid-year. Ratios of males to females varied from 0.85 to 1.78 throughout the year, and although pairs in amplexus were found year round, no spawning activity was seen. Males mature at about 8 cm while females may mature later at 10 cm. A mean of 33% growth during ecdysis in juveniles was observed, suggesting that juveniles of approximately 2 cm may moult about 5 more times before maturity.

Crystallization of a nonclassical Kazal-typeCarcinoscorpius rotundicaudaserine protease inhibitor, CrSPI-1, complexed with subtilisin

Serine proteases play a major role in host-pathogen interactions. The innate immune system is known to respond to invading pathogens in a nonspecific manner. The serine protease cascade is an essential component of the innate immune system of the horseshoe crab. The serine protease inhibitor CrSPI isoform 1 (CrSPI-1), a unique nonclassical Kazal-type inhibitor of molecular weight 9.3 kDa, was identified from the hepatopancreas of the horseshoe crab Carcinoscorpius rotundicauda. It potently inhibits subtilisin and constitutes a powerful innate immune defence against invading microbes. Here, the cloning, expression, purification and cocrystallization of CrSPI-1 with subtilisin are reported. The crystals diffracted to 2.6 A resolution and belonged to space group P2(1), with unit-cell parameters a = 73.8, b = 65.0, c = 111.9 A, beta = 95.4 degrees . The Matthews coefficient (V(M) = 2.64 A(3) Da(-1), corresponding to 53% solvent content) and analysis of the preliminary structure solution indicated the presence of one heterotrimer (1:2 ratio of CrSPI-1:subtilisin) and one free subtilisin molecule in the asymmetric unit.

Frequent occurrence of the tetrodotoxin-bearing horseshoe crab Carcinoscorpius rotundicauda in Vietnam

Tetrodotoxin (TTX) was detected by HPLC and LC-MS/MS in specimens of the horseshoe crab Carcinoscorpius rotundicauda collected from Tan Hai village, Vung Tau province, Vietnam, where cases of poisoning due to the consumption of horseshoe crab have frequently been reported. The soft tissue from 10 out of the 12 specimens analyzed showed considerable levels of TTX, making them unsafe for human consumption (81.2 ± 50.3 MU/g). Paralytic shellfish poisoning (PSP) toxins were also detected in all of the specimens, but the levels were low. These findings show that the frequency of occurrence of C. rotundicauda specimens with a high level of TTX is significantly high, and that the TTX is responsible for the food poisonings caused by the consumption of C. rotundicauda in this area.

Osmoregulation and acid base regulation of the Asian horseshoe crab Carcinoscorpius rotundicauda

Osmoregulation and acid base regulation of the Asian horseshoe crab Carcinoscorpius rotundicauda