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Rare earth element fractionation and distribution in the coastal ecosystem have been of significant concern and are recognized worldwide as emerging micro-pollutants. However, unlike other metals such as trace elements, little is known about their uptake by aquatic plants such as the mangrove Avicennia marina, especially in the central Red Sea. We investigated the fractionation of rare earth elements in six mangrove ecosystems in the central Red Sea and bioavailability in mangrove A. marina. The concentrations of rare earth elements, sediment grain sizes, multi-elemental ratios, geo-accumulation index (Igeo) and bioconcentration factor (BCF) vary significantly (p< 0.05) across the six mangrove ecosystems. Higher concentrations of rare earth elements were recorded at Al Lith (LT) (101.53 mg/kg) and South Jeddah (SJ) (73.38 mg/kg) mangrove ecosystems. However, multi-elemental ratio R(M/L) reveals positive values. In contrast, multi-elemental ratio R(H/M) reveals negative values corresponding to fractionation patterns enriched with medium rare earth elements and heavy rare earth elements depletion across the six mangrove ecosystems. BCF values for rare earth elements were <1, but Lutetium (0.32) had the highest BCF among the rare earth elements, suggesting an efficient accumulation of Lutetium than any other rare earth elements. The scale of Igeo revealed strong contamination (4 ≤ Igeo ≥ 5) of sediment with Lanthanum, Cerium, Praseodynium, Samarium, Godolinium, Holmium, Erbium, Ytterbium, and moderate contamination with Thulium, Terbium, and Dysprosium (1 ≤ Igeo ≤ 3). Principal component analysis showed that clay silt sediment grain size influences rare earth element concentrations in the central Red Sea. Our results provide new evidence for rare earth element fractionation and accumulation in sediment and the potential use of mangrove A. marina for rare earth element monitoring in mangrove ecosystems in the central Red Sea.
Abdullahi Bala Alhassan; Mohammed Othman Aljahdali. Fractionation and Distribution of Rare Earth Elements in Marine Sediment and Bioavailability in Avicennia marina in Central Red Sea Mangrove Ecosystems. Plants 2021, 10, 1233 .
AMA StyleAbdullahi Bala Alhassan, Mohammed Othman Aljahdali. Fractionation and Distribution of Rare Earth Elements in Marine Sediment and Bioavailability in Avicennia marina in Central Red Sea Mangrove Ecosystems. Plants. 2021; 10 (6):1233.
Chicago/Turabian StyleAbdullahi Bala Alhassan; Mohammed Othman Aljahdali. 2021. "Fractionation and Distribution of Rare Earth Elements in Marine Sediment and Bioavailability in Avicennia marina in Central Red Sea Mangrove Ecosystems." Plants 10, no. 6: 1233.
Anthropogenic activities have been on the increase in the urban environment and have led to contamination of the environment with toxic metals. However, mangrove plants’ response to heavy metal stress due to anthropogenic activities explains the metal bioavailability and its potential ecotoxicological effect. We carried out a multi-approach study to investigate i) if the concentrations of metals (Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Cd, Pb, Sr, and V) in mangroves at the central Red Sea are due to the anthropogenic influence and are above the sediment quality guidelines and ii) if an increase in metal concentration influences height and antioxidant enzyme (catalase, CAT; glutathione S-transferase, GST; and superoxide dismutase, SOD) activities in Avicennia marina. There were significant variations (p < 0.05) in metal concentrations and antioxidants across the six mangrove ecosystems with higher concentrations at Al Lith (LT) and south Jeddah (SJ). Even though the concentrations of metals in mangrove leaves are slightly higher in LT than SJ, principal component analysis showed that higher concentrations of Cr, Co, Zn, Cd, and Pb in mangrove leaves from SJ influence higher antioxidant enzyme activities and the lowest average mangrove height (2.01 m). This suggests that higher metal concentrations be factors for the biggest stress in these mangrove ecosystems. However, among the 13 metals, Cr (82.07 mg/kg), Cu (41.29 mg/kg), and As (10.30 mg/kg) in sediments have values within the ERL range of probable effect, while Ni (53.09 mg/kg) was above the ERM threshold. Hence, there is need to focus on monitoring these metals in mangrove sediments and their anthropogenic sources.
Abdullahi Bala Alhassan; Mohammed Othman Aljahdali. Sediment Metal Contamination, Bioavailability, and Oxidative Stress Response in Mangrove Avicennia marina in Central Red Sea. Frontiers in Environmental Science 2021, 9, 1 .
AMA StyleAbdullahi Bala Alhassan, Mohammed Othman Aljahdali. Sediment Metal Contamination, Bioavailability, and Oxidative Stress Response in Mangrove Avicennia marina in Central Red Sea. Frontiers in Environmental Science. 2021; 9 ():1.
Chicago/Turabian StyleAbdullahi Bala Alhassan; Mohammed Othman Aljahdali. 2021. "Sediment Metal Contamination, Bioavailability, and Oxidative Stress Response in Mangrove Avicennia marina in Central Red Sea." Frontiers in Environmental Science 9, no. : 1.
Lagoons along the Red Sea are socio-economically important but most vulnerable ecosystems. Strong evaporation, strengthened due to global warming, leads to high salinity and high temperature in surface water, which exacerbate physiological stress in mangroves. Rabigh Lagoon is characterized by unusually large spatial differences in nutrient dynamics and physicochemical parameters. We conducted a multi-approach study to demonstrate how environmental factors cause growth retardation and stress in mangroves. There were significant variations (P < 0.05) in water salinities and temperatures, nitrogen and phosphorus abundance in sediments, and antioxidants in mangroves among 8 sites across the lagoon. Salinity and water temperature rapidly increased from the northern where Red Sea seawater enters to the southern end, but dissolved oxygen declined. High salinity (44.9), high surface water temperature (28.8°C) and relatively high nutrients at the southern end of the lagoon (S8) corresponded to high concentrations of antioxidants. High δ13C (−12.4‰) and δ15N (4.9‰) in the sediments at S8 also reveal relatively high nutrient level due to stagnant water, camel grazing, and runoff bringing in fertilizer from agriculture activities in the catchments during seasonal flooding events. Principal component analyses showed that N and P limitation at the lagoon entrance is the leading cause for mangrove stress, while high salinity, temperature, and low dissolved oxygen are the predominant factors for high antioxidants concentrations at the southern end of the lagoon.
Mohammed O. Aljahdali; Abdullahi B. Alhassan; Zhaohui Zhang. Environmental Factors Causing Stress in Avicennia marina Mangrove in Rabigh Lagoon Along the Red Sea: Based on a Multi-Approach Study. Frontiers in Marine Science 2021, 8, 1 .
AMA StyleMohammed O. Aljahdali, Abdullahi B. Alhassan, Zhaohui Zhang. Environmental Factors Causing Stress in Avicennia marina Mangrove in Rabigh Lagoon Along the Red Sea: Based on a Multi-Approach Study. Frontiers in Marine Science. 2021; 8 ():1.
Chicago/Turabian StyleMohammed O. Aljahdali; Abdullahi B. Alhassan; Zhaohui Zhang. 2021. "Environmental Factors Causing Stress in Avicennia marina Mangrove in Rabigh Lagoon Along the Red Sea: Based on a Multi-Approach Study." Frontiers in Marine Science 8, no. : 1.
Tilapia (Oreochromis spp.) have significant potential for aquaculture production around the world. There is an increasing demand among tilapia producers for strains with higher yields and for fish that can survive in highly saline water. Novel strains and consistent seedstock are critically important objectives for sustainable aquaculture, but for these required targets there is still not enough progress. Therefore, this study describes the genome sequence of Oreochromis spilurus to support the seawater culture of tilapia. The draft genome is 0.768 Gb (gigabases), with a scaffold N50 (the genome (50%) is in fragments of this length) of 0.22 Mb (megabases). The GC content is 40.4%, the heterozygosity rate is 0.35%, and the repeat content is 47.97%. The predicted protein-coding peptide encoded 51,642 and predicted 10,641 protein-coding genes in the O. spilurus genome. The predicted antimicrobial peptides were 262, bringing new hope for further research. This whole genome sequence provides new insights for biomedical and molecular research and will also improve the breeding of tilapia for high yields, resistance to disease, and adaptation to salt water.
Mohammed Aljahdali; Mohammad Molla; Wessam Filfilan. Whole Genome Sequence of the Newly Prescribed Subspecies Oreochromis spilurus saudii: A Valuable Genetic Resource for Aquaculture in Saudi Arabia. Journal of Marine Science and Engineering 2021, 9, 506 .
AMA StyleMohammed Aljahdali, Mohammad Molla, Wessam Filfilan. Whole Genome Sequence of the Newly Prescribed Subspecies Oreochromis spilurus saudii: A Valuable Genetic Resource for Aquaculture in Saudi Arabia. Journal of Marine Science and Engineering. 2021; 9 (5):506.
Chicago/Turabian StyleMohammed Aljahdali; Mohammad Molla; Wessam Filfilan. 2021. "Whole Genome Sequence of the Newly Prescribed Subspecies Oreochromis spilurus saudii: A Valuable Genetic Resource for Aquaculture in Saudi Arabia." Journal of Marine Science and Engineering 9, no. 5: 506.
Walleye dermal sarcoma virus (WDSV) is a type of retrovirus, which affects most of the adult walleye fishes during the spawning time. The virus causes multiple epithelial tumors on the fish’s skin and fins that are liable for more than 50% of the mortality rate of fish around the world. Till now, no effective antiviral drug or vaccine candidates have been developed that can block the progression of the disease caused by the pathogen. It was found that the 582-amino-acid (aa) residues long internal structural gag polyprotein of the virus plays an important role in virus budding and virion maturation outside of the cell. Inhibition of the protein can block the budding and virion maturation process and can be developed as an antiviral drug candidate against the virus. Therefore, the study aimed to identify potential natural antiviral drug candidates from the tropical mangrove marine plant Avicennia alba, which will be able to block the budding and virion maturation process by inhibiting the activity of the gag protein of the virus. Initially, a homology modeling approach was applied to identify the 3D structure, followed by refinement and validation of the protein. The refined protein structures were then utilized for molecular docking simulation. Eleven phytochemical compounds have been isolated from the marine plant and docked against the virus gag polyprotein. Three compounds, namely Friedlein (CID244297), Phytosterols (CID12303662), and 1-Triacontanol (CID68972) have been selected based on their docking score −8.5 kcal/mol, −8.0 kcal/mol and −7.9 kcal/mol, respectively, and were evaluated through ADME (Absorption, Distribution, Metabolism and Excretion), and toxicity properties. Finally, molecular dynamics (MD) simulation was applied to confirm the binding stability of the protein-ligands complex structure. The ADME and toxicity analysis reveal the efficacy and non-toxic properties of the compounds, where MD simulation confirmed the binding stability of the selected three compounds with the targeted protein. This computational study revealed the virtuous value of the selected three compounds against the targeted gag polyprotein and will be effective and promising antiviral candidates against the pathogen in a significant and worthwhile manner. Although in vitro and in vivo study is required for further evaluation of the compounds against the targeted protein.
Mohammed Aljahdali; Mohammad Molla; Foysal Ahammad. Compounds Identified from Marine Mangrove Plant (Avicennia alba) as Potential Antiviral Drug Candidates against WDSV, an In-Silico Approach. Marine Drugs 2021, 19, 253 .
AMA StyleMohammed Aljahdali, Mohammad Molla, Foysal Ahammad. Compounds Identified from Marine Mangrove Plant (Avicennia alba) as Potential Antiviral Drug Candidates against WDSV, an In-Silico Approach. Marine Drugs. 2021; 19 (5):253.
Chicago/Turabian StyleMohammed Aljahdali; Mohammad Molla; Foysal Ahammad. 2021. "Compounds Identified from Marine Mangrove Plant (Avicennia alba) as Potential Antiviral Drug Candidates against WDSV, an In-Silico Approach." Marine Drugs 19, no. 5: 253.
Rabigh Lagoon, located on the eastern coast of the Red Sea, is an ecologically rich zone in Saudi Arabia, providing habitat to Avicennia marina mangrove trees. The environmental quality of the lagoon has been decaying since the 1990s mainly from sedimentation, road construction, and camel grazing. However, because of remedial measures, the mangrove communities have shown some degree of restoration. This study aims to monitor mangrove health of Rabigh Lagoon during the time it was under stress from road construction and after the road was demolished. For this purpose, time series of EVI (Enhanced Vegetation Index), MSAVI (Modified, Soil-Adjusted Vegetation Index), NDVI (Normalized Difference Vegetation Index), and NDMI (Normalized Difference Moisture Index) have been used as a proxy to plant biomass and indicator of forest disturbance and recovery. Long-term trend patterns, through linear, least square regression, were estimated using 30 m annual Landsat surface-reflectance-derived indices from 1986 to 2019. The outcome of this study showed (1) a positive trend over most of the study region during the evaluation period; (2) most trend slopes were gradual and weakly positive, implying subtle changes as opposed to abrupt changes; (3) all four indices divided the times series into three phases: degraded mangroves, slow recovery, and regenerated mangroves; (4) MSAVI performed best in capturing various trend patterns related to the greenness of vegetation; and (5) NDMI better identified forest disturbance and recovery in terms of water stress. Validating observed patterns using only the regression slope proved to be a challenge. Therefore, water quality parameters such as salinity, pH/dissolved oxygen should also be investigated to explain the calculated trends.
Mohammed Othman Aljahdali; Sana Munawar; Waseem Razzaq Khan. Monitoring Mangrove Forest Degradation and Regeneration: Landsat Time Series Analysis of Moisture and Vegetation Indices at Rabigh Lagoon, Red Sea. Forests 2021, 12, 52 .
AMA StyleMohammed Othman Aljahdali, Sana Munawar, Waseem Razzaq Khan. Monitoring Mangrove Forest Degradation and Regeneration: Landsat Time Series Analysis of Moisture and Vegetation Indices at Rabigh Lagoon, Red Sea. Forests. 2021; 12 (1):52.
Chicago/Turabian StyleMohammed Othman Aljahdali; Sana Munawar; Waseem Razzaq Khan. 2021. "Monitoring Mangrove Forest Degradation and Regeneration: Landsat Time Series Analysis of Moisture and Vegetation Indices at Rabigh Lagoon, Red Sea." Forests 12, no. 1: 52.
The outbreak of COVID-19 has spread globally affecting human activities but with improvement in ambient air quality. The first case of the virus in the Kingdom of Saudi Arabia was on the 2nd of March, 2020. The impact of COVID-19 lockdown on the ambient air quality of the Kingdom of Saudi Arabia for the first time using data from nine cities was determined in this study. Hourly air quality data, based on concentrations of carbon monoxide (CO), particulate matter (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2) and ozone (O3), and meteorological conditions (atmospheric temperature, relative humidity, and wind speed) of the nine cities studied were obtained from Saudi Arabian General Authority of Meteorology and Environmental Protection (GAMEP) for the period between January 2019 to May 2020. Significant variation (p<0.05) was recorded for the five atmospheric pollutants across the cities before and during the lockdown with lower concentrations during the lockdown except for the concentration of O3 in Tabuk, Al Qasim, and Haql. This can be as a result of NO and O3 reaction, causing the inability of effective O3 depletion. The percentage change in concentration for CO (33.60%) and SO2 (44.16%) was higher in Jeddah and PM10 (91.12%) at Riyadh, while NO2 (44.35%) and O3 (18.98%) was highest in Makkah. However, even though there was a decrease in pollutants concentration during the lockdown, the concentrations for CO, PM10, SO2, NO2, and O3 were still above WHO 24 hours and annual mean limit levels. The COVID- 19 lockdown in the Kingdom of Saudi Arabia revealed the possibility of significant atmospheric pollutant reduction by controlling traffic, activities by industries, and environmentally friendly transportation programs such as green commuting programs.
Mohammed Othman Aljahdali; Abdullahi Bala Alhassan; Mutaz N. Albeladi. Impact of novel coronavirus disease (COVID-19) lockdown on ambient air quality of Saudi Arabia. Saudi Journal of Biological Sciences 2020, 28, 1356 -1364.
AMA StyleMohammed Othman Aljahdali, Abdullahi Bala Alhassan, Mutaz N. Albeladi. Impact of novel coronavirus disease (COVID-19) lockdown on ambient air quality of Saudi Arabia. Saudi Journal of Biological Sciences. 2020; 28 (2):1356-1364.
Chicago/Turabian StyleMohammed Othman Aljahdali; Abdullahi Bala Alhassan; Mutaz N. Albeladi. 2020. "Impact of novel coronavirus disease (COVID-19) lockdown on ambient air quality of Saudi Arabia." Saudi Journal of Biological Sciences 28, no. 2: 1356-1364.
The pursuit of a good candidate to biomonitor environmental pollutants has been on the increase. In this study, the concentrations of Fe, Mn, Cu, Zn, Cd, Cr, Pb and Ni in sediment, seawater and seagrass Cymodocea serrulata compartments and antioxidant enzymes activities in C. serrulata were determined. Our results revealed that bioconcentration factors for all the metals were less than 1 (BCF < 1) and concentrations in seagrass compartments were in the order root > leaf > rhizome for Fe and Mn, leaf > root > rhizome for Cu, Zn, Pb and Ni, and root > rhizome > leaf for Cd and Cr. Effect range low concentrations (ER-L) revealed that Cu, Zn, Cd, Pb and Ni concentrations were above ER-L values and Cr concentration was below ER-L values while concentrations in seawater for all the heavy metals were above the estimate average element concentrations in seawater (ECS). Significant variation (p < 0.05) was recorded for heavy metals in sediment, seawater, seagrass compartments and heavy metal concentrations across stations. Influence of heavy metals on antioxidant enzymes activities; catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST) and acetylcholinesterase (AChE) were recorded, and high activities of the antioxidants were recorded in station S8 corresponding to high concentrations of heavy metals in the same station. There is a need for the promotion of biomonitoring networks across the marine environment using C. serrulata and antioxidant enzymes as biomarkers of oxidative stress caused by environmental pollutants.
Mohammed Othman Aljahdali; Abdullahi Bala Alhassan. Heavy Metal Accumulation and Anti-Oxidative Feedback as a Biomarker in Seagrass Cymodocea serrulata. Sustainability 2020, 12, 2841 .
AMA StyleMohammed Othman Aljahdali, Abdullahi Bala Alhassan. Heavy Metal Accumulation and Anti-Oxidative Feedback as a Biomarker in Seagrass Cymodocea serrulata. Sustainability. 2020; 12 (7):2841.
Chicago/Turabian StyleMohammed Othman Aljahdali; Abdullahi Bala Alhassan. 2020. "Heavy Metal Accumulation and Anti-Oxidative Feedback as a Biomarker in Seagrass Cymodocea serrulata." Sustainability 12, no. 7: 2841.
Contamination of mangrove ecosystems, including those of the Red Sea area, has caused serious concern globally. Spatial distribution of heavy metals and their bioaccumulation in one of the common mangrove plants of Saudi Arabia, Avicennia marina L., was evaluated in 8 stations at the Rabigh lagoon to assess the ecological risks due to heavy metal contamination. Among all the heavy metals, Fe concentration was recorded highest (8939.38 ± 312.63 mg/kg) at station S4. Contamination factor (CF) values for all heavy metals determined in this study were recorded in ascending order as Cu < Cr < Mn < Zn < Fe < Ni < Pb < Cd, with the pollution load index pattern recorded in descending order as S6 > S4 > S3 > S5 > S7 > S1 > S8 > S2. Bio-concentration factor (BCF) was <1 for all the heavy metals and there was a positive correlation between the antioxidants and lead (Pb), which can be a result of the ability of A. marina to exclude or detoxify this metal by its mechanism of exclusion or detoxification. A significant correlation existed between the heavy metals concentration in sediment and A. marina leaves at one combination or the other, except for Cu and Cd, which do not correlate with any other metal concentration. The information provided in the present study can be used in the monitoring and measurement of heavy metal pollution in marine ecosystems or other aquatic environments, to prevent several ecological risks to the mangrove ecosystem.
Mohammed O. Aljahdali; Abdullahi Bala Alhassan. Ecological risk assessment of heavy metal contamination in mangrove habitats, using biochemical markers and pollution indices: A case study of Avicennia marina L. in the Rabigh lagoon, Red Sea. Saudi Journal of Biological Sciences 2020, 27, 1174 -1184.
AMA StyleMohammed O. Aljahdali, Abdullahi Bala Alhassan. Ecological risk assessment of heavy metal contamination in mangrove habitats, using biochemical markers and pollution indices: A case study of Avicennia marina L. in the Rabigh lagoon, Red Sea. Saudi Journal of Biological Sciences. 2020; 27 (4):1174-1184.
Chicago/Turabian StyleMohammed O. Aljahdali; Abdullahi Bala Alhassan. 2020. "Ecological risk assessment of heavy metal contamination in mangrove habitats, using biochemical markers and pollution indices: A case study of Avicennia marina L. in the Rabigh lagoon, Red Sea." Saudi Journal of Biological Sciences 27, no. 4: 1174-1184.
Heavy metal pollution has been on the rise with serious implications for the wellbeing of aquatic ecosystems. Benthic sediments and freshwater mollusk (snail): Mellanoides tuberculata were sampled from five stations for determination of heavy metals concentrations and measurement of antioxidant enzyme activities. The spatial variation was studied using an enrichment factor, potential ecological risk index, and mean probable effect limit quotient (mPELq). From the results, Cu, Zn, Cd, Cr, Pb, Ni, and Co contamination levels were high at stations S3, S4, and S5 with an mPEL quotient of 94.40%. The variation of metal concentration and Enrichment factor were in the order S5 > S3 > S4 > S2 > S1, which was attributed to anthropogenic influences at the catchment due to industrial activities and atmospheric deposition of metals. Station five in this study is downstream and requires the most monitoring and management to prevent several ecological risks of metal pollutants in River Kaduna.
Mohammed Othman Aljahdali; Abdullahi Bala Alhassan. Spatial Variation of Metallic Contamination and Its Ecological Risk in Sediment and Freshwater Mollusk: Melanoides tuberculata (Müller, 1774) (Gastropoda: Thiaridae). Water 2020, 12, 206 .
AMA StyleMohammed Othman Aljahdali, Abdullahi Bala Alhassan. Spatial Variation of Metallic Contamination and Its Ecological Risk in Sediment and Freshwater Mollusk: Melanoides tuberculata (Müller, 1774) (Gastropoda: Thiaridae). Water. 2020; 12 (1):206.
Chicago/Turabian StyleMohammed Othman Aljahdali; Abdullahi Bala Alhassan. 2020. "Spatial Variation of Metallic Contamination and Its Ecological Risk in Sediment and Freshwater Mollusk: Melanoides tuberculata (Müller, 1774) (Gastropoda: Thiaridae)." Water 12, no. 1: 206.
Industrial and domestic discharges of effluent is one of the major causes of heavy metal pollution in aquatic ecosystems. Samples of benthic sediment and freshwater mollusc Bellamya unicolor were collected from 5 sites in the River Kaduna to determine heavy metal concentration, their ecological risk, and antioxidant enzymes activities in Bellamya unicolor. The results revealed the level of pollution based on heavy metal concentrations across the sites in the order S5 > S3 > S4 > S1 > S2. The ecological risk factor (ErF) revealed that Cd made the highest contribution to pollution, recording the highest ErF (2206.41). Moreover, the results of correlation base multivariate analysis showed that urban and industrial waste were the sources of Cu and Pb in the River Kaduna. The significant positive correlation between metal concentration and antioxidants catalase (CAT) and superoxide dismutase (SOD) was established, with maximum activities of antioxidants at site S5. Results from this study have revealed potential ecological risk as a result of heavy metals pollution in the River Kaduna. Hence the need for approaches and policies be put in place to prevent the discharge of untreated industrial and domestic waste into this aquatic ecosystem.
Mohammed Othman Aljahdali; Abdullahi Bala Alhassan. Metallic Pollution and the Use of Antioxidant Enzymes as Biomarkers in Bellamya unicolor (Olivier, 1804) (Gastropoda: Bellamyinae). Water 2020, 12, 202 .
AMA StyleMohammed Othman Aljahdali, Abdullahi Bala Alhassan. Metallic Pollution and the Use of Antioxidant Enzymes as Biomarkers in Bellamya unicolor (Olivier, 1804) (Gastropoda: Bellamyinae). Water. 2020; 12 (1):202.
Chicago/Turabian StyleMohammed Othman Aljahdali; Abdullahi Bala Alhassan. 2020. "Metallic Pollution and the Use of Antioxidant Enzymes as Biomarkers in Bellamya unicolor (Olivier, 1804) (Gastropoda: Bellamyinae)." Water 12, no. 1: 202.
In hermaphroditic helminth parasites, infrapopulation size or mating group size mostly affects some processes acting within the infrapopulation. Here, 30 natural infrapopulations (12-154 individuals) of the intestinal trematode Gyliauchen volubilis Nagaty, 1956 from the fish Siganus rivulatus consisting of newly excysted juveniles, immature and mature worms were found distributed in a well-defined fundamental niche (anterior 40 % of the intestine). In small infrapopulations, all stages of the parasite were alive. In larger infrapopulations, differential mortality was only and consistently observed among newly excysted juveniles, and gradually increased to include most or all juveniles in the largest infrapopulations. Among mature worms, the mean worm length seemed unaffected by the infrapopulation size. However, the ratio mean testis size-mean ovary size, a reliable indicator of resource allocation to the male function and of opportunities for crossfertilization, significantly increased with mating group size. In small infrapopulations, all stages of the parasite were scattered along the niche, and never seen in mating pairs (possibly reproduced by selffertilization). In larger infrapopulations, newly excysted juveniles and immature worms were scattered along the anterior two thirds of the niche, while mature worms were constantly found aggregated in its posterior third (narrow microhabitat), where some were arranged in mating pairs. The probability of mating reciprocally or unilaterally was dependent on body size. The mean number of uterine eggs per worm significantly decreased and their mean sizes significantly increased with mating group size. The results are statistically significant and suggest that infrapopulation self-regulation is greatly associated with its size.
M.O. Al-Jahdali. Infrapopulations of Gyliauchen volubilis Nagaty, 1956 (Trematoda: Gyliauchenidae) in the rabbitfish Siganus rivulatus (Teleostei: Siganidae) from the Saudi coast of the Red Sea. Parasite 2012, 19, 227 -238.
AMA StyleM.O. Al-Jahdali. Infrapopulations of Gyliauchen volubilis Nagaty, 1956 (Trematoda: Gyliauchenidae) in the rabbitfish Siganus rivulatus (Teleostei: Siganidae) from the Saudi coast of the Red Sea. Parasite. 2012; 19 (3):227-238.
Chicago/Turabian StyleM.O. Al-Jahdali. 2012. "Infrapopulations of Gyliauchen volubilis Nagaty, 1956 (Trematoda: Gyliauchenidae) in the rabbitfish Siganus rivulatus (Teleostei: Siganidae) from the Saudi coast of the Red Sea." Parasite 19, no. 3: 227-238.
Factors regulating gastrointestinal nematode infrapopulations are to a great extent density-dependent. Here, 23 natural infrapopulations (41–281 individuals) of the viviparous nematodeProcamallanus elatensis(Camallanidae) from the fishSiganus rivulatuswere found distributed in a well-defined fundamental niche (posterior 55% of the intestine). Immature worms were mostly found in the anterior third of this niche, while mature worms were found in aggregations posterior to them and followed by gravid females in the posterior 20% of the intestine. This distribution strongly suggests that worms migrate towards the posterior intestine while they mature, copulate and reproduce. In small infrapopulations, the sex ratios were distinctly female-biased and the number of gravid females was low. In large infrapopulations, the sex ratios were distinctly male-biased and the number of gravid females was high. However, the mean lengths of both immature males and females and mature females decreased dramatically as the infrapopulation size increased, while those of mature males increased significantly. These results strongly suggest intraspecific competition and density-dependent regulation of mean worm length, and the increase in the mean length of mature males strongly suggests intense sexual selection and competition between mature males. Production of larvae by female worms decreased significantly as the infrapopulation size increased, suggesting a density-dependent reduction in female worm fertility. The results are statistically significant and strongly suggest that infrapopulation self-regulation is through density-dependent mechanisms, in which development of immature worms, infrapopulation size, sex ratio, sexual selection and carrying capacity of the fundamental niche play essential roles in shaping and regulating the infrapopulations.
Mohammed Aljahdali. Infrapopulations ofProcamallanus elatensisFusco & Overstreet, (Nematoda: Camallanidae) in the rabbitfishSiganus rivulatus(Teleostei, Siganidae) from the Saudi coast of the Red Sea. Journal of Helminthology 2011, 86, 378 -385.
AMA StyleMohammed Aljahdali. Infrapopulations ofProcamallanus elatensisFusco & Overstreet, (Nematoda: Camallanidae) in the rabbitfishSiganus rivulatus(Teleostei, Siganidae) from the Saudi coast of the Red Sea. Journal of Helminthology. 2011; 86 (3):378-385.
Chicago/Turabian StyleMohammed Aljahdali. 2011. "Infrapopulations ofProcamallanus elatensisFusco & Overstreet, (Nematoda: Camallanidae) in the rabbitfishSiganus rivulatus(Teleostei, Siganidae) from the Saudi coast of the Red Sea." Journal of Helminthology 86, no. 3: 378-385.
Although nothing is known about gyliauchenid life cycles, molecular phylogenetic studies have placed the Gyliauchenidae Fukui, 1929 close to the Lepocreadiidae Odhner, 1905. The gyliauchenidGyliauchen volubilisNagaty, 1956 was found in the intestine of its type-host,Siganus rivulatus, a siganid fish permanently resident in a lagoon within the mangrove swamps on the Egyptian coast of the Gulf of Aqaba. Larval forms of this trematode (mother sporocysts, rediae and cercariae) were found in the gonads and digestive gland ofClypeomorus clypeomorus(Gastropoda: Cerithiidae), a common snail in the same lagoon. So, this life cycle ofG. volubiliswas elucidated under natural conditions: eggs are directly ingested by the snail; mother sporocysts and rediae reach their maturity 3–6 and 11–13 weeks post-infection; rediae contain 23–29 developing cercariae; fully developed cercariae are gymnocephalus, without penetration glands, emerge from the snail during the night 16–18 weeks post-infection and rapidly encyst on aquatic vegetation (no second intermediate host); encysted metacercariae are not progenetic; 4-day-old metacercariae encysted on filamentous algae fed toS. rivulatusdeveloped into fully mature worms 6–8 weeks post-infection. The cycle was completed in about 26 weeks and followed one of the three known patterns of lepocreadiid life cycles, and except for the gymnocephalus cercariae, the other larval stages are very similar to those of lepocreadiids. Generally, the life cycle ofG. volubilisimplicitly supports the phylogenetic relationship of Gyliauchenidae and Lepocreadiidae inferred from molecular phylogenetic studies.
M.O. Al-Jahdali; R.M. El-Said Hassanine. The life cycle ofGyliauchen volubilisNagaty, (Digenea: Gyliauchenidae) from the Red Sea. Journal of Helminthology 2011, 86, 165 -172.
AMA StyleM.O. Al-Jahdali, R.M. El-Said Hassanine. The life cycle ofGyliauchen volubilisNagaty, (Digenea: Gyliauchenidae) from the Red Sea. Journal of Helminthology. 2011; 86 (2):165-172.
Chicago/Turabian StyleM.O. Al-Jahdali; R.M. El-Said Hassanine. 2011. "The life cycle ofGyliauchen volubilisNagaty, (Digenea: Gyliauchenidae) from the Red Sea." Journal of Helminthology 86, no. 2: 165-172.
In infrapopulations of helminth parasites, density-dependent effects, through some form of intra- and interspecific competition, play an important role in shaping and regulating the infrapopulations. The mechanisms responsible for these processes have often been observed in laboratory studies and rarely studied under natural conditions. Here, 24 natural infrapopulations (77–447 individuals) of the acanthocephalanSclerocollum saudiiAl-Jahdali, 2010 from the fishSiganus rivulatusconsisted of cystacanths, newly excysted juveniles, immature and mature worms, distributed in a well-defined fundamental niche (anterior 60% of the intestine). Each of these stages exhibited a significantly different longitudinal distribution within this niche. In small infrapopulations, cystacanths and newly excysted juveniles were found in the sixth 10% of the intestine, immature worms in the fifth 10% and mature worms in the anterior 40% of the intestine. However, their proportions followed a clear ascending order in each infrapopulation, and the female–male ratios of both immature and mature worms were distinctly female-biased. In large infrapopulations, mature worms existed partially in the site of immature ones, where a differential mortality among immature females was constantly observed. However, the proportions of immature worms increased significantly and those of mature worms decreased significantly, the mean lengths of immature and mature females decreased dramatically and the female–male ratios were distinctly male-biased. The mean sizes of immature and mature males seemed stable through all infrapopulations. The distribution of mature males and females suggests intense male–male competition for access to females, and reveals that larger females are copulated prior to the smaller ones. The results are statistically significant and suggest that infrapopulation self-regulation is through density-dependent mechanisms, in which immature females may play a key role.
M.O. Al-Jahdali; R.M. El-Said Hassanine. Infrapopulations ofSclerocollum saudiiAl-Jahdali, 2010 (Acanthocephala: Cavisomidae) in the rabbitfishSiganus rivulatus(Teleostei, Siganidae) from the Saudi coast of the Red Sea. Journal of Helminthology 2011, 86, 85 -94.
AMA StyleM.O. Al-Jahdali, R.M. El-Said Hassanine. Infrapopulations ofSclerocollum saudiiAl-Jahdali, 2010 (Acanthocephala: Cavisomidae) in the rabbitfishSiganus rivulatus(Teleostei, Siganidae) from the Saudi coast of the Red Sea. Journal of Helminthology. 2011; 86 (1):85-94.
Chicago/Turabian StyleM.O. Al-Jahdali; R.M. El-Said Hassanine. 2011. "Infrapopulations ofSclerocollum saudiiAl-Jahdali, 2010 (Acanthocephala: Cavisomidae) in the rabbitfishSiganus rivulatus(Teleostei, Siganidae) from the Saudi coast of the Red Sea." Journal of Helminthology 86, no. 1: 85-94.
Specimens of the fishes Acanthopagrus bifasciatus Forsskål (Sparidae) and Siganus rivulatus Forsskål (Siganidae) were caught in the Red Sea off the coast of Rabigh, Saudi Arabia. Four (25%) and 24 (80%) of these fishes, respectively, were found to harbour intestinal helminths. Acanthopagrus bifasciatus was parasitised by Neowardula brayi gen. nov., sp. nov. (Trematoda: Mesometridae) and S. rivulatus by Sclerocollum saudii sp. nov. (Acanthocephala: Cavisomidae). Neowardula brayi gen. nov. is similar to Wardula Poche, 1926, but clearly differs from it and from the other four genera of the family Mesometridae Poche, 1926 in having a ventral surface anterior to the intestinal bifurcation greatly modified into a well-developed, relatively deep pouch encircling the genital pore and constantly diagonal testes. Sclerocollum saudii sp. nov. is similar to S. rubrimaris Schmidt et Paprena, 1978 (type species), but clearly differs in having a proboscis only armed with 10 rows of hooks, smaller proboscis hooks, lemnisci much longer than proboscis receptacle and much smaller egg size. The developmental stages of this acanthocephalan (cystacanths, juveniles and immature worms) are also described and figured.
Mohammed O. Al-Jahdali. Helminth parasites from Red Sea fishes: Neowardula brayi gen. nov., sp. nov. (Trematoda: Mesometridae Poche, 1926) and Sclerocollum saudii sp. nov. (Acanthocephala: Cavisomidae Meyer, 1932). Zootaxa 2010, 2681, 57 -65.
AMA StyleMohammed O. Al-Jahdali. Helminth parasites from Red Sea fishes: Neowardula brayi gen. nov., sp. nov. (Trematoda: Mesometridae Poche, 1926) and Sclerocollum saudii sp. nov. (Acanthocephala: Cavisomidae Meyer, 1932). Zootaxa. 2010; 2681 (1):57-65.
Chicago/Turabian StyleMohammed O. Al-Jahdali. 2010. "Helminth parasites from Red Sea fishes: Neowardula brayi gen. nov., sp. nov. (Trematoda: Mesometridae Poche, 1926) and Sclerocollum saudii sp. nov. (Acanthocephala: Cavisomidae Meyer, 1932)." Zootaxa 2681, no. 1: 57-65.
To date, Myxidium elmatboulii Ali, Abdel-Baki et Sakran, 2006 (Myxozoa, Myxosporea) is the only species of the genus known from the Red Sea, and was originally described as a coelozoic parasite in the gall bladder of the belonid fish, Tylosurus choram. A Myxidium sp. closely similar to M. elmatboulii is described herein for the first time as a histozoic parasite in the ovary of the onespot snapper fish, Lutjanus monostigma (Teleostei, Lutjanidae) from the Red Sea coast of Saudi Arabia. The infected ovary was morphologically abnormal, with two protruding digitiform black cysts at its distal end, densely packed with mature plasmodia suspended in a mucoid liquid. Histological examination revealed that the cysts were extended deeply within the ovary, and each was surrounded by a capsule consisting of a relatively thick layer of fibrous connective tissues of host origin (host tissue reaction), and followed internally by a distinct black layer composed of melanomacrophages encircling the parasite mass; this layer clearly indicates the ability of this myxosporean parasite to induce a strong immune inflammatory response in the ovary of L. monostigma. Many small or developing cysts with the same characteristics were seen scattered in the connective tissue between the ovarian follicles. Plasmodia or spores of the parasite were not seen within the oocytes or within its developmental stages. The cysts occupied a considerable part of the ovary, and some areas of the ovarian tissues appeared to be vacuolated or degenerated. Thus, the typical ovarian structure of L. monostigma was greatly affected and lost its normal architecture. Therefore, the infection caused by this Myxidium sp. is presumed to negatively affect the reproductive capacity of the fish host.
Mohammed Aljahdali; Reda M. El-S. Hassanine. Ovarian abnormality in a pathological case caused by Myxidium sp. (Myxozoa, Myxosporea) in onespot snapper fish Lutjanus monostigma (Teleostei, Lutjanidae) from the Red Sea. Acta Parasitologica 2010, 55, 1 -7.
AMA StyleMohammed Aljahdali, Reda M. El-S. Hassanine. Ovarian abnormality in a pathological case caused by Myxidium sp. (Myxozoa, Myxosporea) in onespot snapper fish Lutjanus monostigma (Teleostei, Lutjanidae) from the Red Sea. Acta Parasitologica. 2010; 55 (1):1-7.
Chicago/Turabian StyleMohammed Aljahdali; Reda M. El-S. Hassanine. 2010. "Ovarian abnormality in a pathological case caused by Myxidium sp. (Myxozoa, Myxosporea) in onespot snapper fish Lutjanus monostigma (Teleostei, Lutjanidae) from the Red Sea." Acta Parasitologica 55, no. 1: 1-7.
During June and July of 2007, a total of 130 specimens of the fish Rastrelliger kanagurta Cuvier (Teleostei, Scombridae), ranging between 19–31 cm in total length, were caught in the Red Sea off the coast of Sharm El-Sheikh, South Sinai, Egypt, and examined for infections by acanthocephalans (65 fish/month). Of this number, 29 (22.30%) were slightly or heavily parasitized by the acanthocephalan Diplosentis nudus (Harada, 1938) Pichelin et Cribb, 2001 (Cavisomidae); no other helminth parasites were found in the intestine of R. kanagurta. Twenty-nine infrapopulations of D. nudus, ranging from 23–218 individuals were collected from the infected fishes. These infrapopulations were distributed in a well-defined fundamental niche along the intestine of R. kanagurta, where the distribution of male worms was not random with respect to female worms size and position and suggests that the male-male competition for access to female may be intense and may select for large males. No correlation between fish size and infrapopulation size was observed. Correlations between female-to-male sex ratio and infrapopulation size, numbers of females and their mean lengths, numbers of males and their mean lengths, mean female length and mean male length within infrapopulation were very strong, and clearly suggest that as the infrapopulation size increased, the number of females and their mean lengths decreased and the number of males and their mean lengths increased. Combination of these results strongly suggests density-dependent effects and competition between male worms. The relationship between the mean female length or size and the number of eggs within its pseudocoel was strongly positive; egg production by female worm significantly decreases as the infrapopulation size increases, suggesting density-dependent reduction in female worm fecundity. Tendency for the variability in male testes size was not significant in infrapopulations of D. nudus. All of these results are discussed.
Reda M. El-S. Hassanine; Mohammed Aljahdali. Intraspecific density-dependent effects on growth and fecundity of Diplosentis nudus (Harada, 1938) Pichelin et Cribb, 2001 (Acanthocephala, Cavisomidae). Acta Parasitologica 2008, 53, 289 -295.
AMA StyleReda M. El-S. Hassanine, Mohammed Aljahdali. Intraspecific density-dependent effects on growth and fecundity of Diplosentis nudus (Harada, 1938) Pichelin et Cribb, 2001 (Acanthocephala, Cavisomidae). Acta Parasitologica. 2008; 53 (3):289-295.
Chicago/Turabian StyleReda M. El-S. Hassanine; Mohammed Aljahdali. 2008. "Intraspecific density-dependent effects on growth and fecundity of Diplosentis nudus (Harada, 1938) Pichelin et Cribb, 2001 (Acanthocephala, Cavisomidae)." Acta Parasitologica 53, no. 3: 289-295.
Between May and September 2006, 640 specimens of the rabbitfish Siganus rivulatus Forsskål (Teleostei, Siganidae) were examined for infections with intestinal helminths. These fishes were caught in the Red Sea off the coast of Sharm El-Sheikh, South Sinai, Egypt, examined in a field laboratory and separated into three size groups of regular length intervals. Only three species of helminths were recovered: the trematode Gyliauchen volubilis Nagaty, 1956 (Gyliauchenidae Fukui, 1929), the acanthocephalan Sclerocollum rubrimaris Schmidt et Paperna, 1978 (Cavisomidae Meyer, 1932) and the nematode Procamallanus elatensis Fusco et Overstreet, 1979 (Cucullanidae Cobbold, 1864). The distribution of these helminths along the intestine of S. rivulatus, in all patterns of single and concurrent infections and the corresponding prevalences and intensities of infection in the different size groups of the fish were recorded. In single infections, each parasite species was found distributed in a well-defined fundamental niche along the intestine of Siganus rivulatus, and a distinct partial overlap between the niches of G. volubilis and Sclerocollum rubrimaris was observed. In concurrent infections with these two species, their fundamental niches were significantly reduced, probably being affected by interactive site segregation and individuals of each species were found segregated in a restricted realised niche. In all other patterns of concurrent infections, each parasite species was normally found in its original fundamental niche. The prevalences of these parasites in the fish examined were relatively low and somewhat similar. In all patterns of single and concurrent infections, the intensity of infection was directly related to fish size. In concurrent infection with G. volubilis and S. rubrimaris, a significant decline was observed in the intensities of both species in the different size groups of the fish, but, in all other patterns of concurrent infections, no significant change in intensity was observed. These observations suggest that the interaction between G. volubilis and S. rubrimaris is probably a negative and symmetrical one. The mode of transmission of these parasites to the fish is also discussed.
Reda M. El -S. Hassanine; Mohammed Aljahdali. Ecological comments on the intestinal helminths of the rabbitfish Siganus rivulatus (Teleostei, Siganidae) from the northern Red Sea. Acta Parasitologica 2007, 52, 1 .
AMA StyleReda M. El -S. Hassanine, Mohammed Aljahdali. Ecological comments on the intestinal helminths of the rabbitfish Siganus rivulatus (Teleostei, Siganidae) from the northern Red Sea. Acta Parasitologica. 2007; 52 (3):1.
Chicago/Turabian StyleReda M. El -S. Hassanine; Mohammed Aljahdali. 2007. "Ecological comments on the intestinal helminths of the rabbitfish Siganus rivulatus (Teleostei, Siganidae) from the northern Red Sea." Acta Parasitologica 52, no. 3: 1.