Lack of information on the daily activity patterns of Litopenaeus vannamei (Boone 1931) might result in inadequate feed management strategies in shrimp farms. In order to provide information to improve feed management in shrimp farms, the daily activity of juvenile shrimp reared in glass aquaria was studied, using L. vannamei (7.57±1.01 g), equivalent to 33 shrimp m?2. Thirty‐two shrimp were observed, half in light and half in dark phase, over 280 h in 15 min h?1 windows. Feed was provided once a day, at 10% of tank biomass. Swimming, exploration of substrate, inactivity and cleaning were recorded through instantaneous focal sampling. During the dark phase, swimming was predominant and alternated with exploration. In the light phase, inactivity was predominant, and again alternated with exploration. Cleaning occurred evenly in both the light and the dark. Substrate exploration, which characterizes the search for food, occurred in both dark and light phases, with a most intense peak 7 h after light phase onset, indicating this as the optimal feed offer. 相似文献
Even though sediments may represent a reservoir for antimicrobial agents, little is known about the persistence of these molecules
over time or their accumulation. In this study, six antimicrobial agents, oxolinic acid, flumequine, nalidixic acid, norfloxacin,
sulphamethoxazole and trimethoprim, were investigated in a sediment core from the Seine River. This work aimed to (1) measure
antimicrobial agent contamination levels in the sediment and identify their origins, (2) obtain information on the persistence
of these compounds in sediment over long periods (>4 years) and (3) show the existence of a historical record in sediment
of river contamination by antimicrobial agents. 相似文献
Ninety-three (93) horses were investigated for serum antibodies to Theileria equi (T. equi) and Babesia caballi (B. caballi) using the immunofluorescent antibody test (IFAT). Seventy-seven (82.8%) horses were seropositive; 31 (33.3%) were positive to T. equi compared to 64 (68.8%) to B. caballi while 18 (19.4%) horses were seropositive to both parasites. No significant differences in antibody frequencies among females and males for either T. equi or B. caballi were noted. Differences in seropositivity to B. caballi among age groups were not significant. Antibodies to T. equi were more frequent than to B.caballi in the age group 5 years and over than in the 1-2 and 2-4 years age groups (p<0.05). Unlike T. equi antibodies, B. caballi antibodies in horses in the county of Caroni were significantly less frequent when compared to other counties (p<0.05). Of 18 (19.4%) clinically ill horses, seven (42.9%) had clinicopathological evidence of anemia. Only one-third (6 of 18) horses were positive for the parasite on Wright-Giemsa stained blood smears and anemia was present in only 2. We report here that B. caballi and not T. equi may be the more common agent of piroplasmosis in Trinidad. 相似文献
The peatland carbon store is threatened by climate change and is expected to provide positive feedback on air temperature. Most studies indicate that enhanced temperature and microbial activities result in a rise of dissolved organic carbon (DOC) as a consequence of higher peat decomposition. Few of them, however, have investigated the impact of in situ experimental warming on DOC response.
Material and methods
We studied the response of DOC, dissolved organic nitrogen (DON), phenol oxidase, and fluorescein diacetate activities (FDA) to a 3-year in situ experimental warming using open-top chambers (OTCs) in a Sphagnum-dominated peatland.
Results and discussion
No significant warming of soil was recorded, implying that the simultaneous decrease in DOC and DON and the rise in FDA at the depths of 25 and 40 cm were not caused by the direct effect of OTCs on water temperature, but might instead have been mediated by plant root exudates. The water chemistry suggests that DOC production was compensated by in situ mineralization. We hypothesize that an increased hydrolysis of organic matter (OM) was counterbalanced by the mineralization of dissolved organic matter (DOM) and that microorganisms preferentially used labile compounds originating from increased root exudates.
Conclusions
This trade-off between production of DOC through hydrolysis and consumption in the process of mineralization shows (1) the limitation of using only DOC as an indicator of the sensitivity of peat decomposition to climate warming and (2) the need to improve our understanding of the indirect impact of root exudates. 相似文献
□ Growth and nutrient acquisition of tomato (Lycopersicon esculentum L.) cv ‘Amani’ were studied under induced salt stress in Hoagland's solution. The plants were treated for 37 days with salinity induced by incorporating different concentrations [0.0 (control), 50, 100, 150, or 200 mM] of sodium chloride (NaCl) to the nutrient solution. Slight reduction was obtained in growth represented by (shoot length and number, leaf number, and dry weight) when seedlings were directly exposed to NaCl stress from 0.0 to 100 mM. At higher concentrations (150 or 200 mM), growth parameters were adversely affected and seedlings died thereafter. Elevated salinity significantly reduced crude protein and fiber in shoots and roots. Tomato shoot and root contents of potassium (K), iron (Fe), and ash were reduced significantly in response to increased levels of salinity. Tissue contents of sodium (Na) and chloride (Cl) increased with elevated salinity treatments. 相似文献
Growth and micronutrient acquisition of some apple (Malus dometsica Borkh) varieties (Galla, MM 111, MM I06, M 26, and M6 York) were studied under gradually in vitro induced NaCl (from 0, 50 to 100 mM) salinity. Microshoot dry weight tended to increase with increasing salinity level in all varieties except in M 26 and M6 York as some decline was obtained at 100 mM NaCl. Shoot proliferation was decreased significantly in Galla at 100 mM NaCl and at both salinity levels in M 26 compared to the control (0 mM). A significant decrease in shoot zinc (Zn) acquisition with increasing salinity level was obtained in all varieties except MM 111. M6 York and MM 111 decreased their copper (Cu) acquisition significantly at 50 mM NaCl and then increased at 100 mM salinity level. Meanwhile, a significant decrease in Cu acquisition with increasing NaCl concentration was obtained in Galla and M 26. Galla, MM 106, and M 26 showed a significant increase in manganese (Mn) acquisition at 50 mM NaCl followed by a decrease at 100 mM salinity level. On the other hand, Mn acquisition continued to decrease significantly in MM 111 while M6 York increased its Mn acquisition with increasing salinity. M 111 and M6 York showed a significant decrease in iron (Fe) acquisition at 50 mMNaCl followed by an increase at 100mM NaCl. Galla and M 26 continued to decrease Fe acquisition with elevated salinity level, whereas Fe in MM 106 increased with salinity. 相似文献
The native plant microbiome is composed of diverse microbial communities that influence overall plant health, with some species known to promote plant growth and pathogen resistance. Here, we show the antibacterial and growth promoting activities of autoclaved culture metabolites (ACM) from native endophytic bacteria (NEB). These NEB were isolated from a papaya cultivar (var. Cariflora) that is tolerant to bacterial crown rot (BCR) caused by Erwinia mallotivora. In this cultivar, bacterial colonization in tissues recovering from the disease was observed before onset of tissue regeneration or ‘regrowth’. We further isolated and characterized these bacteria and were able to identify two culturable stem NEB related to plant endophytic genera Kosakonia sp. (ex. Enterobacter sp., isolate EBW), and to Sphingomonas sp. (isolate EBY). We also identified root NEB under genus Bacillus (isolates BN, BS, and BT). Inhibition assays indicated that ACM from these NEB promptly (within 18-30 h) and efficiently inhibited (60–65% reduction) E. mallotivora proliferation in vitro. When surface-sterilized papaya seeds were soaked in ACM from isolates EBY and EBW, germination was variably retarded (20–60% reduction) depending on plant genotype, but plant biomass accumulation was significantly stimulated, at around two-fold increase. Moreover, greenhouse experiments show that ACM from all isolates, especially isolate EBW, significantly reduced BCR incidence and severity in a susceptible genotype (var. Solo), at around two-fold. In general, our observations of pathogen antagonism and plant growth promotion leading to disease reduction, suggested the influence of native endophytic bacteria to increased fitness in plants, and tolerance against the re-emerging crown rot disease of papaya.
SummaryThe present study was carried out to analyse the activities of several anti-oxidant enzymes at various stages of somatic embryogenesis in Catharanthus roseus. The hypothesis was that anti-oxidant enzymes accumulated as part of a cellular defence mechanism in response to stress. We therefore measured superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities in various in vitro-grown tissues such as embryogenic and non-embryogenic calli, and in embryos at various stages. SOD activity increased gradually from the early embryogenic stage to heart-shaped stage embryos, but declined in the later stages (i.e., torpedo-shaped and cotyledonary embryos). In contrast, APX activity was high in non-embryogenic callus and decreased rapidly during the stage of embryo initiation. This pattern was the same for CAT. The maximum CAT activity was observed in non-embryogenic callus, then it declined almost linearly at the embryonic and post-embryonic developmental stages. The effect of exogenous hydrogen peroxide (H2O2) on in vitro embryogenesis was also evaluated. Lower H2O2 levels (0.025 mM) promoted embryo formation, whereas higher levels (0.10 mM) inhibited embryogenesis in C. roseus. Finally, higher soluble protein, free amino acid, and proline contents were found in embryogenic calli compared to non-embryogenic calli. 相似文献