Quantifying the impacts of abrasion and bacterial transfer when fish are exposed to sand during a catch-and-release event:
- Authors: Foster, Ryan M , Childs, Amber-Robyn , Brooks, Margot , Farthing, Matthew W , Butler, Edward C , Potts, Warren M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160427 , vital:40445 , https://doi.org/10.2989/1814232X.2020.1792982
- Description: Best-practice guidelines to improve recreational fishers’ handling during catch-and-release (CandR) events are critical to improve the conservation and management of fish stocks worldwide. While best-practice research is growing, there are knowledge gaps, with the effects of sand exposure on fish mucous membranes understudied. This study aimed to determine the effects of exposing a fish to sand during a CandR event. A total of 360 juvenile (48–137 mm TL) Cape stumpnose Rhabdosargus holubi were subjected to a simulated CandR event during which they were either held: (i) with wet hands, or (ii) dry hands; or with wet hands and then placed on either (iii) wet sterilised sand, (iv) dry sterilised sand, (v) wet unsterilised sand, or (vi) dry unsterilised sand. Fish were maintained in a recirculating system for two weeks, euthanised and subjected to an examination of their mucous layer (bacterial counts, abrasion counts and percentage of abrasion area) and an internal biological assessment. Bacteria fro m fish mucous layers were cultivated on agar plates to count bacterial colonies.
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- Date Issued: 2020
Synergistic effects of temperature and plant quality, on development time, size and lipid in Eccritotarsus eichhorniae
- Authors: Ismail, Mohannad , Brooks, Margot , Van Baaren, Joan , Albittar, Loulou
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/426078 , vital:72312 , xlink:href="https://doi.org/10.1111/jen.12841"
- Description: Body size is an important biotic factor in evolutionary ecology, since it affects all aspects of insect physiology, life history and, consequently, fitness in ectothermic insects and how species adapt with their environment. It has been linked to tem-perature, with lower temperatures resulting in larger size. In this study, we tested the combined impact of temperature and plant quality on the body size, and de-velopment time from egg to adult of Eccritotarsus eichhorniae (Hemiptera: Miridae), an herbivorous insect used as a biological control agent against the invasive aquatic weed, water hyacinth Eichhornia crassipes (Pontederiaceae). We quantified insect size in individuals exposed to three temperatures (20, 25 and 30°C) combined with three qualities of host plant (high, medium and low) by calculating development time and measuring four traits: tibia length, forewing length, dry body mass and lipid con-tent, and we also determined the wing loading index. The development time, dry body mass and lipid content decreased linearly with increasing temperature and de-creasing plant quality. The decrease in size was the greatest when high temperature interacted with low plant quality. Smaller individuals had proportionately less lipid content. Wing loading decreased significantly with lower quality of host plant, result-ing in individuals likely to have theoretically higher flight ability. The results support the temperature-size rule (TSR) and that plant quality could influence the relationship between development time and the TSR. Results also provide novel evidence for a possible food quality-size rule for both sexes.
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- Date Issued: 2020
Distribution and ecological assessment of heavy metals in irrigation channel sediments in a typical rural area of south China
- Authors: Gu, Chiming , Liu, Yi , Li, Zhiguo , Mohamed, Ibrahim , Zhang, Ronghua , Brooks, Margot , Chen, Fang
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66924 , vital:29000 , ISSN 0925-8574 , https://doi.org/10.1016/j.ecoleng.2016.01.054
- Description: Publisher version , Elevated levels of heavy metals in sediments of irrigation channels can pose risks for crops and livestock, as well as for human health. In this study sediment samples were collected from the irrigation channel in a typical rural area of south China, and digested, in order to analyze their contents for the presence of heavy metals Cu, Zn, Pb, Cr, Cd, and Ni, as well as the non-metal As, to assess total concentrations and pollution levels. The pollution load index and potential ecological risk index of these elements were utilized to assess contamination levels and ecotoxicity. Our results showed that the concentrations of the 7 elements were in the order of Zn > Ni > Cr > Cu > As > Pb > Cd. With the exception of Cr and Pb, concentrations of elements were higher than their background in soil, especially for Cd (1.79 mg kg−1), As (99.61 mg kg−1) and Ni (142.62 mg kg−1), which were 18.49, 8.89 and 5.30 times their background concentrations, respectively. The whole sampled zone was characterized by medium pollution and had a very high potential ecological risk. The area of arable land presented a medium pollution risk, while areas near to the path or road showed high risk of pollution. The predominant contributors to elevated ecological risk for the whole zone were Cd and As.
- Full Text: false
- Date Issued: 2016
Diversity of bacteria isolated from the flies Musca domestica (Muscidae) andChrysomya megacephala (Calliphoridae) with emphasis on vectored pathogens
- Authors: Brits, Devon , Brooks, Margot , Villet, Martin H
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66904 , vital:28998 , ISSN 1021-3589 , https://doi.org/10.4001/003.024.0365
- Description: Publisher version , We evaluated the bacteria occurring externally on Musca domestica and Chrysomya megacephala, the two most common synanthropic flies which may be found at many refuse sites throughout the world. Bacteria cultured from 10 specimens of each species were isolated, Gram-stained and examined microscopically, and divided into morphologically distinct ‘pseudospecies', to avoid excessive duplication of genetic identification. About 350 bp of the 16S ribosomalRNAgene was amplified from genomicDNAextracted from each ‘pseudospecies', sequenced, and bacteria identified using BLASTn. Nineteen different types of colony were identified from M. domestica, with Pseudomonas sp. and Swine Manure Bacterium SP14 being most abundant. Chrysomya megacephala yielded 15 distinct pseudospecies with total colony counts approximating to 10 000 from 10 plates, where 80 % of colonies were non-pathogenic Bacillus pumilus. A total of 18 species were identified genetically: three shared by the fly species; four unique to C. megacephala, and 13 unique to M. domestica. Half of these 18 species were pathogenic, two or three others were food spoilers and the rest were environmental or commensal bacteria from soil or plant matter. This study added three new pathogenic strains of bacteria and one new environmental strain to the list of bacteria reported to be vectored by these flies.
- Full Text: false
- Date Issued: 2016
Dynamic changes of soil surface organic carbon under different mulching practices in citrus orchards on sloping land
- Authors: Gu, Chiming , Liu, Yi , Mohamed, Ibrahim , Zhang, Runhua , Wang, Xiao , Nie, Xinxin , Jiang, Min , Brooks, Margot , Chen, Fang , Li, Zhiguo
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/${Handle} , vital:28997 , ISSN 0168384 , https://doi.org/10.1371/journal.pone.0168384
- Description: Publisher version , Mulching management has been used in many places all over the world to improve agricultural sustainability. However, the cycling of carbon in the soil under applications of mulch on sloping arable land is not yet fully understood. A four-year field experiment was carried out in Xiaofuling watershed of Danjiangkou reservoir in China. The object was to evaluate the effects of the application of straw mulch (ST) and grass mulch (GT) on dynamic changes in soil organic carbon and its fractions. Results showed that mulch applied on the soil surface increased the contents of SOC and its active fractions in the soil. Compared to the control without cover (CK), ST and GT treatments increased the contents of SOC, LOC, DOC, POC and EOC by 14.73%, 16.5%, 22.5%, 41.5% and 21%, respectively, in the 0–40 cm soil layer, and by 17%, 14%, 19%, and 30%, respectively, in the 0–100 cm soil layer. The contents of organic carbon and its active fractions decreased with increasing soil depth in all of the treatments. SOC was accumulated in the period of December to the following March. The contents of soil DOC and LOC were high in January to March, while the contents of soil POC and EOC were high in June to September. The relative contents of soil organic carbon fractions were POC > EOC > LOC > DOC over the four years. Straw mulching had no significant effect on the changes in soil organic carbon active fractions during the different periods. Based on this long-term field experiment in Danjiangkou reservoir, we found that straw mulching had a significant effect on soil, increasing SOC content and stock in slopping arable land, and that live grass mulching was more effective than rice straw mulching. We discuss possible optimal periods for the implementation of mulching practices on sloping land.
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- Date Issued: 2016
The impact of geographical origin of two strains of the herbivore, Eccritotarsus catarinensis, on several fitness traits in response to temperature
- Authors: Ismail, Mohannad , Brooks, Margot
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66914 , vital:28999 , ISSN 0306-4565 , https://doi.org/10.1016/j.jtherbio.2016.07.008
- Description: Publisher version , Adaptation to temperature changes is vital to reduce adverse effects on individuals, and some may present phenotypic changes, which might be accompanied with physiological costs in fitness traits. The objective of this study was to determine whether the two strains of the herbivore Eccritotarsus catarinensis, a biological control agent against water hyacinth in South Africa, differ in their responses to temperature according to their geographical origin. We experimentally quantified the responses of the two strains, at three constant temperatures: 20 °C, 25 °C and 30 °C, using laboratory cultures that originated from Brazil and Peru, where climates differ. Reproductive output, egg hatching rate, sex ratio and longevity were recorded at each temperature. Fitness traits for both strains were significantly reduced at 30 °C compared with 25 °C and 20 °C in two successive generations. Nonetheless, Peruvian individuals continued their development at 30 °C, whereas Brazilian individuals that succeeded in emerging did not continue their development. In contrast, sex ratio was unaffected by temperature. The Peruvian strain of E. catarinensis presented different phenotypes depending on temperature and was more adapted to extreme high temperature than the Brazilian strain. The tropical origin of the population induces the insect to tolerate the extreme high temperature. We suggest that the Peruvian strain could be better suited for release to control water hyacinth in nature, particularly in regions where temperature is high.
- Full Text: false
- Date Issued: 2016