Browsing by Author "Kyewalyanga, Margareth S."

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    Isolation of the Tephrosia vogelii extract and rotenoids and their toxicity in the RTgill-W1 trout cell line and in zebrafish embryos
    (Elsevier, 2020) Said, Aziza H.; Solhaug, Anita; Sandvik, Morten; Msuya, Flower E.; Kyewalyanga, Margareth S.; Mmochi, Aviti J.; Lyche, Jan L.; Hurem, Selma
    This study focused on identifying the rotenoids from the Tephrosia vogelli plant (fish-poison-bean), investigating the toxic potency of a crude T. vogelii extract and individual rotenoids (tephrosin, deguelin and rotenone) in vitro and in vivo and assessing the mode of action. A trout (Onychorynhis mykiss) gill epithelial cell line (RTgill-W1) was used to determine the cytotoxicity of rotenoids and effects on cell metabolism. Zebrafish (Danio rerio) aged from 3 h post fertilization (hpf) to 72 hpf were used for testing the developmental toxicity. The crude T. vogelii plant extract significantly decreased the cellular metabolic activity and was cytotoxic at lower concentrations (5 and 10 nM, respectively), while tephrosin, deguelin and rotenone showed these effects at concentrations ≥ 50 nM. The crude T. Vogelli extract had the highest toxic potency and induced adverse health effects in zebrafish including deformities and mortality at the lowest concentration (5 nM) compared to rotenone (10 nM) and deguelin and tephrosin (50 nM). These results indicate that the crude T. Vogelii extracts are highly potent and the bioactivity of these extracts warrant further investigation for their potential use to treat parasites in human and veterinary medicine and as a natural alternative to pesticides.
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    Spatial variation in the phytoplankton community of the Pemba Channel, Tanzania, during the south-east monsoon
    (Elservier Ltd, 2021) Sekadende, Baraka C.; Michael, Angelina; Painter, Stuart C.; Shayo, Salome; Noyon, Margaux; Kyewalyanga, Margareth S.
    The spatiotemporal distribution of phytoplankton within Tanzanian coastal waters is considered to be poorly known. Improved knowledge of the phytoplankton community, including the spatiotemporal distribution, is desirable for understanding certain aspects of trophic linkages to small pelagic fish, a key marine resource in Tanzania, and for understanding how anthropogenic activities such as terrestrial run-off and effluent discharge may impact the phytoplankton community of these waters. In this study the abundance, diversity and distribution of microphytoplankton was determined throughout the Pemba Channel during the Southeast monsoon and assessed in relation to local environmental parameters. A total of 88 species were identified during this study. Generally, diatoms dominated the microphytoplankton community of the Pemba Channel with 55 identified species (62.5% of total), followed by 31 dinoflagellate species (35.2%) and 2 cyanobacteria species (2.27%). Abundances were low, generally less than 100 cell L−1. Despite a clear dominance by diatoms within the samples, no obvious spatial pattern in their distribution was identified within the channel. Cyanobacteria meanwhile displayed a significant latitudinal gradient being more abundant in the northern half of the channel. Several harmful or potentially harmful phytoplankton species were also identified in this study including Pseudo-nitzschia sp. and Dinophysis sp., although their abundances were below the thresholds of harmful algal bloom warning systems. Nevertheless, to understand whether these species are increasing with time in response to anthropogenic activities, regular phytoplankton monitoring programs are recommended.
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    Spirulina (Arthrospira fusiformis, Gomont 1892) as a high-quality feed ingredient for Nile Tilapia Fingerlings
    (African Journals Online (AJOL), 2023) Michael, Angelina; Kyewalyanga, Margareth S.; Lugomela, Charles V.
    A partially randomized experimental design was conducted to evaluate the effect and potential of spirulina species (Arthrospira fusiformis) isolated from Momela Lakes, Tanzania, on the growth, antioxidant capacity, feed utilization, and body composition of Nile tilapia fingerlings. Five dietary treatments were formulated, including spirulina meal at 5%, 10%, and 15% of the total diets, as well as control diets with freshwater shrimp or Lake Victoria sardine. The protein content of the experimental diets was 25, 28, and 35% for a treatment containing spirulina at 5, 10, and 15% inclusion, respectively, while the control diets had 35% crude protein each. After eight weeks of feeding, fish fed with a lower inclusion level of spirulina showed the best growth performance and feed utilization efficiency, similar to the fish fed with control diets. The group fed with 5% spirulina exhibited excellent protein efficiency ratio compared to all other fish groups. All spirulina-fed fish groups demonstrated higher protein deposition and strong antioxidant activity against free radicals compared to those fed with control diets. In conclusion, spirulina proves to be a superior feed ingredient for high-quality Nile tilapia farming, providing comparable results to control feeds.
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    Spirulina (arthrospira fusiformis, Gomont 1892) as a high-uality feed ingredient for nile tilapia fingerlings
    (African Journals Online (AJOL), 2023) Michael, Angelina; Kyewalyanga, Margareth S.; Lugomela, Charles V.
    A partially randomized experimental design was conducted to evaluate the effect and potential of spirulina species (Arthrospira fusiformis) isolated from Momela Lakes, Tanzania, on the growth, antioxidant capacity, feed utilization, and body composition of Nile tilapia fingerlings. Five dietary treatments were formulated, including spirulina meal at 5%, 10%, and 15% of the total diets, as well as control diets with freshwater shrimp or Lake Victoria sardine. The protein content of the experimental diets was 25, 28, and 35% for a treatment containing spirulina at 5, 10, and 15% inclusion, respectively, while the control diets had 35% crude protein each. After eight weeks of feeding, fish fed with a lower inclusion level of spirulina showed the best growth performance and feed utilization efficiency, similar to the fish fed with control diets. The group fed with 5% spirulina exhibited excellent protein efficiency ratio compared to all other fish groups. All spirulina-fed fish groups demonstrated higher protein deposition and strong antioxidant activity against free radicals compared to those fed with control diets. In conclusion, spirulina proves to be a superior feed ingredient for high-quality Nile tilapia farming, providing comparable results to control feeds.