Ontogenetic resource use and trophic dynamics of endangered juvenile Tachypleus tridentatus among diversified nursery habitats in the northern Beibu Gulf,China     

Kit Yue KWAN  Justin BOPP  Shuyan HUANG  Qiao CHEN  Chun-Chieh WANG  Xueping WANG  Wenquan ZHEN  Junhua ZHU  Xing HUANG 《Integrative zoology》2021,16(6):908-928

Horseshoe crabs, the most well-known example of “living fossils”, are iconic and ecologically important macroinvertebrates in coastal and estuarine ecosystems. Their blood is a crucial resource for manufacturing Limulus or Tachypleus amebocyte lysate to detect bacterial endotoxins or fungal contamination in drug and medical devices. An enhanced understanding of their ecological roles and trophic interactions in the food webs is fundamental to facilitate resource management for the declining populations in Asia. Foraging information of the Asian species, however, is mainly derived from preliminary, scattered reports from a limited number of study locations. In this study, resource utilization, trophic niche dynamics, and trophic interaction of the juvenile tri-spine horseshoe crab, Tachypleus tridentatus (instars 1–12, approximately 0.5–8 years old) across ontogeny was assessed in diversified nursery habitats along the northern Beibu Gulf, China, using carbon and nitrogen stable isotopes. Our results suggest that: (i) T. tridentatus are ecological generalists given the vast range of carbon isotopic values and trophic niche width estimates exhibited between multiple instar groups; (ii) juvenile T. tridentatus across most habitat types predominantly assimilated energy from a variety of basal production sources in the food web, but primarily depended on sedimentary organic matter and seagrass resource pools; (iii) ontogenetic shifts in juvenile dietary proportions were evident, with decreased reliance on sedimentary organic matter, coupled with increased reliance on benthic macroinvertebrate grazers, detritivores, and omnivores with age; and (iv) nearly all juvenile instars occupied similar trophic positions in the food web with slight shifts in trophic position present with increasing size. Our findings indicate that resource availability and ontogenetic diet shifts strongly influence horseshoe crab trophic dynamics, and age should be accounted when formulating habitat conservation measures based on resource use for Asian horseshoe crabs.  相似文献   

Why testing improves memory: mediator effectiveness hypothesis     

Pyc MA  Rawson KA 《Science (New York, N.Y.)》2010,330(6002):335

A wealth of research has established that practice tests improve memory for the tested material. Although the benefits of practice tests are well documented, the mechanisms underlying testing effects are not well understood. We propose the mediator effectiveness hypothesis, which states that more-effective mediators (that is, information linking cues to targets) are generated during practice involving tests with restudy versus during restudy only. Effective mediators must be retrievable at time of test and must elicit the target response. We evaluated these two components of mediator effectiveness for learning foreign language translations during practice involving either test-restudy or restudy only. Supporting the mediator effectiveness hypothesis, test-restudy practice resulted in mediators that were more likely to be retrieved and more likely to elicit targets on a final test.  相似文献   

Release kinetics of tocopherol and quercetin from binary antioxidant controlled-release packaging films     

Chen X  Lee DS  Zhu X  Yam KL 《Journal of agricultural and food chemistry》2012,60(13):3492-3497

This paper investigated the feasibility of manipulating packaging polymers with various degrees of hydrophobicity to release two antioxidants, tocopherol and quercetin, at rates suitable for long-term inhibition of lipid oxidation in food. For example, one antioxidant can be released at a fast rate to provide short-term/intermediate protection, whereas the other antioxidant can be released at a slower rate to provide intermediate/long-term protection of lipid oxidation. Controlled-release packaging films containing tocopherol and quercetin were produced using ethylene vinyl alcohol (EVOH), ethylene vinyl acetate (EVA), low-density polyethylene (LDPE), and polypropylene (PP) polymers; the release of these antioxidants to 95% ethanol (a fatty food simulant) was measured using UV-vis spectrophotometry, and Fickian diffusion models with appropriate initial and boundary conditions were used to fit the data. For films containing only quercetin, the results show that the release of quercetin was much faster but lasted for a much shorter time for hydrophilic polymers (EVOH and EVA) than for hydrophobic polymers (LDPE and PP). For binary antioxidant films containing tocopherol and quercetin, the results show that tocopherol released more rapidly but for a shorter period of time than quercetin in LDPE and EVOH films, and the difference is more pronounced for LDPE films than EVOH films. The results also show the presence of tocopherol can accelerate the release of quercetin. Although none of the films produced is acceptable for long-term lipid oxidation inhibition, the study provides encouraging results suggesting that acceptable films may be produced in the future using polymer blend films.  相似文献   

Effect of temperature on germination and early growth of subterranean clover, capeweed and Wimmera ryegrass     

N. C. Turner  C. J. Thomson  & H. M. Rawson 《Grass and Forage Science》2001,56(2):97-104

Germination of annual pasture species was studied under controlled‐environment conditions in south‐western Australia at temperatures in the range from 4°C to 35°C. Subterranean clover (Trifolium subterraneum) and Wimmera ryegrass (Lolium rigidum) had a germination of 90% between 12°C and 29°C, whereas capeweed (Arctotheca calendula) had a high germination percentage in a much narrower temperature range with an optimum of 25°C. Growth of subterranean clover, capeweed and Wimmera ryegrass between 28 and 49 days after sowing (DAS) was also studied at two photon flux densities, 13 and 30 mol m^?2 d^?1, and at diel temperatures in the range from 15/10°C to 33/28°C. Pasture species grown at a density of 1000 plants m^?2 accumulated at least twice the amount of shoot dry matter when subjected to temperatures of 21/16°C and 27/22°C, compared with a lower temperature of 15/10°C and a higher temperature of 33/28°C. Except at the highest temperature and at high photon flux density, capeweed had lower green area indices (GAI) than the other two species at 28 DAS. Crop growth rates between 28 and 49 DAS were higher in Wimmera ryegrass than in the other two species, whereas subterranean clover had a lower relative growth rate than the other two species at all temperatures and both photon flux densities. Subterranean clover and capeweed intercepted a greater proportion of the incident radiation compared with Wimmera ryegrass. The values of radiation interception and GAI were used to estimate the number of DAS to reach 75% radiation interception [f_(0·75)]. The number of days to reach f_(0·75) decreased with increasing temperature from 15/10°C to reach a minimum at 27/22°C. The time taken to achieve f_(0·75) was always shorter by about 10 d when the photon flux density was 30 mol m^?2 d^?1 in the autumn compared with 13 mol m^?2 d^?1 in the winter. These results are discussed in relation to the early growth of annual pasture in the field.  相似文献   

Clinical presentation,treatment, and outcome of 24 dogs with bacterial meningitis or meningoencephalitis without empyema (2010-2020)     

Faye Rawson  Max Foreman  Thomas Mignan  Jack Galer  Anne Fraser  Abbe Crawford 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2023,37(1):223-229

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Congenital hypothyroidism with goiter in toy fox terriers     

Fyfe JC  Kampschmidt K  Dang V  Poteet BA  He Q  Lowrie C  Graham PA  Fetro VM 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2003,17(1):50-57

Congenital hypothyroidism with goiter was observed to segregate as a simple autosomal recessive trait in Toy Fox Terriers (TFTs). Neonatal affected pups exhibited inactivity, abnormal hair coat, stenotic ear canals, and delayed eye opening. Palpable ventrolateral cervical swellings were evident by 1 week of age. Serum thyroid hormone and thyroid-stimulating hormone concentrations were low and high, respectively. Histologic examination of the cervical masses disclosed cuboidal to columnar follicular epithelial cell hyperplasia with widely varying follicular size, shape, and amount of colloid. Oral thyroid hormone replacement therapy restored near-normal growth and development. At 8 weeks of age, radioiodine uptake and perchlorate discharge testing indicated an iodine organification defect. Biochemical analysis of thyroid tissue from affected dogs demonstrated enzymatic iodine oxidation deficiency and lack of sodium dodecyl sulfate-resistant thyroglobulin dimers, suggesting thyroid peroxidase deficiency. A nonsense mutation in the thyroid peroxidase gene of affected dogs was discovered and demonstrated to segregate with the disease. A DNA-based carrier test was developed and currently is used by TFT breeders to prevent this disorder.  相似文献   

Efficacy of bath vaccination with a live attenuated Vibrio harveyi against vibriosis in Asian seabass fingerling,Lates calcarifer     

Yong Kit Chin  Nurhidayu Al‐saari  Zarirah Zulperi  Aslizah Mohd‐Aris  Annas Salleh  Santha Silvaraj  Aslah Mohamad  JingYie Lee  Mohd Zamri-Saad  Md Yasin Ina-Salwany 《Aquaculture Research》2020,51(1):389-399

Vibrio harveyi causes vibriosis in various marine aquaculture fish species, especially when they are young. The infection subsequently leads to significant economic losses for aquaculture farms. Vaccination is recommended to control this disease. This study describes the efficacy of a live attenuated V. harveyi strain MVh_vhs (LAVh) as a vaccine candidate in controlling infection by wild‐type V. harveyi (WTVh) in Lates calcarifer. A total of 240 fingerlings were divided into four groups. Group 1 was not vaccinated and was not challenged, Group 2 was vaccinated with a formalin‐killed V. harveyi (FKVh), Group 3 was vaccinated with the LAVh before challenge and Group 4 was not vaccinated and was challenged. Bath vaccination was employed for one hour before the LAVh distribution was determined in the fish mucus, gill, liver, gut, kidney and spleen. The gills, livers, kidneys and skins were also sampled for gene expression analysis. To challenge the fish, skin abrasion was conducted before the fish were challenged by immersion with WTVh. The results revealed an extensive distribution of the LAVh in the liver and kidneys of the fish in Group 3 for the first 12 hr, resulting in mild lesions compared with Group 1. Similarly, there were significantly (p < .05) higher expressions of the Chemokine ligand 4 and major histocompatibility complex I genes in the skin and liver of the fish in Group 3 in comparison with other groups. Vaccination with LAVh resulted in a significantly high rate of survival (68%) of the fingerlings after being challenged with WTVh.  相似文献   

Visual observations of the sea floor subduction line in the middle-america trench     

Heezen BC  Rawson M 《Science (New York, N.Y.)》1977,196(4288):423-426

Four dives were made to the floor of the Middle-America Trench with the U.S. Navy's deep research submersible DSV Turtle. The area investigated is located between Costa Rica and the Cocos Ridge where the depth of the trench floor does not exceed the 2000-meter capability of the submersible. At the axis of the trench floor a series of steep northeast-facing scarps 10 to 20 meters high lie parallel to the trench axis. Here oceanic crust appears to have been carried down by near-vertical normal vaults of small displacement. Between these small scarps and the landward wall of the trench a narrow line of recent deformation interrupts a smooth apron. Unconsolidated sediments are thrust in sharply serrated piles and cut by sharp-edged chasms. This line of deformation is interpreted as the present sea floor trace of crustal subduction.  相似文献   

Field emission scanning electron microscopy and transmission electron microscopy studies of the chorion, plasma membrane and syncytial layers of the gastrula-stage embryo of the zebrafish Brachydanio rerio: a consideration of the structural and functional relationships with respect to cryoprotectant penetration     

D M. Rawson  T. Zhang  D. Kalicharan  & W L. Jongebloed 《Aquaculture Research》2000,31(3):325-336

The structure of the chorion and plasma membranes of gastrula‐stage zebrafish Brachydanio rerio embryos were studied using field emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM). These studies confirm the outer chorion membrane complex to be 1.5–2.5 μm in thickness and to consist of three layers, electron‐dense outer and innermost layers (0.2–0.3 and 1.0–1.6 μm in thickness respectively) separated by an electron‐lucent middle layer (0.3–0.6 μm in thickness). The middle and inner layers are pierced by pore canals. A granular to farinaceous nature of the thin outer surface of the outer layer of the chorion has been revealed for the first time. The study provides original TEM images of the plasma membrane structures of gastrula‐stage embryos, and FE‐SEM and TEM images showing the plasma membrane to have three morpohologically distinct regions, being prominently ridged and folded at the surface of the blastoderm, smooth over the syncytial layer at the vegetal pole and with an intermediate region between the animal and vegetal pole where folding develops in advance of the expanding blastodermal disc of cells. FE‐SEM and TEM studies reveal details of the syncytial layer (1–4 μm thick) beneath the smooth plasma membrane at the vegetal pole, containing cytoplasmic organelles and small yolk globules. The significance of the structural detail shown in these studies is considered in the light of the difficulties experienced in cryopreservation of the embryo resulting from the inability of achieving cryoprotectant penetration of the yolk mass.  相似文献   

Detection of Serum Agglutinins for Monilia and Other Yeast-like Organisms     

Norris RF  Rawson AJ 《Science (New York, N.Y.)》1947,105(2717):105

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