Browsing by Author "Chauka, Leonard J."
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item Antimicrobial and Cytotoxicity Activity of Clausena Anisata, Acokanthera Shemperii and Olea Europaea Growing in Tanzania(2016) Makirita, Winisia E.; Chauka, Leonard J.; Chacha, MusaAims: To evaluate antimicrobial and cytotoxicity activities of Clausena anisata, Acokanthera shemperii and Olea europaea against seven Gram negative bacteria and fungal species. Study Design: Bioassay of antimicrobial assay was done using 96-well micro-dilution method. Place and Duration of Study: School of Life Science and Bioengineering, Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania, from April 2014 to June 2014. Methodology: 96-well micro dilution method was used in antimicrobial assay. Extracts were loaded in the wells of the first row, followed by serial dilution and 50 µl of the bacterial suspensions (0.5 MacFarland standard turbidity) were added in each well. The first concentration which showed no bacterial growth was considered as minimum inhibition concentration. Method developed by Meyer et al 1982 was adopted in cytotoxicity activities. Results: All extracts indicated antibacterial activity on at least three to five of the tested seven bacteria and two fungi species with MIC value ranging 0.7812 - 12.5 mg/mL. The highest activity was demonstrated by Olea europaea leaf methanolic, Acokanthera shemperii stem bark and Clausena anisata twigs ethyl acetate extracts with MIC value of 0.7812 mg/mL against Pseudomonas aeruginosa while the same MIC value was exhibited by Olea europaea stem bark methanol against Proteus mirabilis. However the Olea europaea root methanolic extract inhibited the growth of Pseudomonas aeruginosa and Salmonella kisarawe with MIC value of 0.7812 mg/mL. Olea europaea leaf methanolic and stem bark methanolic which demonstrated high antimicrobial activity were non toxic against brine shrimp larvae with LC50 value of 369.8272 and 226.1566 µg/mL, while Clausena anisata twigs ethyl acetate, Acokanthera shemperii stem bark ethyl acetate and Olea europaea root methanolic extracts were toxic with LC50 value of 6.21276, 67.4179 and 92.3089 µg/mL respectively. Conclusion: This study has unveiled antimicrobial and cytotoxicity properties of Clausena anisata, Acokanthera shemperii and Olea europaea.Item Blind to Morphology: Genetic Identifies Several Widespread Ecologically Common Species and Few Endemics among Indo-Pacific Cauliflower Corals (Pocillopora, Scleractinia).(2013) Pinzón, Jorge H.; Sampayo, Eugenia M.; Cox, Evelyn F.; Chauka, Leonard J.; Chen, Chaolun A.; Voolstra, Christian R.; LaJeunesse, Todd C.Aim: Using high-resolution genetic markers on samples gathered from across their wide distributional range, we endeavoured to delimit species diversity in reef-building Pocillopora corals. They are common, ecologically important, and widespread throughout the Indo-Pacific, but their phenotypic plasticity in response to environmental conditions and their nearly featureless microskeletal structures confound taxonomic assignments and limit an understanding of their ecology and evolution. Location: Indo-Pacific, Red Sea, Arabian/Persian Gulf. Methods: Sequence analysis of nuclear ribosomal (internal transcribed spacer 2, ITS2) and mitochondrial (open reading frame) loci were combined with population genetic data (seven microsatellite loci) for Pocillopora samples collected throughout the Indo-Pacific, Red Sea and Arabian Gulf, in order to assess the evolutionary divergence, reproductive isolation, frequency of hybridization and geographical distributions of the genus. Results: Between five and eight genetically distinct lineages comparable to species were identified with minimal or no hybridization between them. Colony morphology was generally incongruent with genetics across the full range of sampling, and the total number of species is apparently consistent with lower estimates from competing morphologically based hypotheses (about seven or eight taxa). The most commonly occurring genetic lineages were widely distributed and exhibited high dispersal and gene flow, factors that have probably minimized allopatric speciation. Uniquely among scleractinian genera, this genus contains a monophyletic group of broadcast spawners that evolved recently from an ancestral brooder. Main conclusions: The delineation of species diversity guided by genetics fundamentally advances our understanding of Pocillopora geographical distributions, ecology and evolution. Because traditional diagnostic features of colony and branch morphology are proving to be of limited utility, the identification of Pocillopora species for future ecological and experimental work should rely on genetic characters that will improve research and aid in conservation strategies for these and other reef-building corals, including the detection of real and mistaken endemic populations.Item Comparison of Endosymbiotic and Free-Living Symbiodinium (Dinophyceae) Diversity a Hawaiian Reef Environment. J Phycol(2010) Pochon, Xavier; Stat, Michael; Takabayashi, Misaki; Chasqui, Luis; Chauka, Leonard J.; Logan, Daniel D. K.; Gates, Ruth D.Many scleractinian corals must acquire their endosymbiotic dinoflagellates (genus Symbiodinium) anew each generation from environmental pools, and exchange between endosymbiotic and environmental pools of Symbiodinium (reef waters and sediments) has been proposed as a mechanism for optimizing coral physiology in the face of environmental change. Our understanding of the diversity of Symbiodinium spp. in environmental pools is poor by comparison to that engaged in endosymbiosis, which reflects the challenges of visualizing the genus against the backdrop of the complex and diverse micro-eukaryotic communities found free-living in the environment. Here, the molecular diversity of Symbiodinium living in the waters and sediments of a reef near Coconut Island, O‘ahu, Hawai‘i, sampled at four hourly intervals over a period of 5 d was characterized using a Symbiodinium-specific hypervariable region of the chloroplast 23S. A comparison of Symbiodinium spp. diversity recovered from environmental samples with the endosymbiotic diversity in coral species that dominate the adjacent reef revealed limited overlap between these communities. These data suggest that the potential for infection, exchange, and ⁄ or repopulation of corals with Symbiodinium derived from the environment is limited at this location, a finding that is perhaps consistent with the high proportion of coral species in this geographic region that transmit endosymbionts from generation to generation.Item Diversity of symbiotic algae in the genus Symbiodinium in Scleractinian corals of Tanzania(Western Indian Ocean Marine Science Association, 2013-05-17) Chauka, Leonard J.With the current increase in frequency of coral bleaching events, knowledge on the genetic diversity of symbiotic algae in the genus Symbiodinium harboured by reef-building corals is important to understand how coral reefs will respond to global climate change. This study was undertaken as very little is known about the subject in reef-building corals in Tanzania and yielded information on the genetic diversity of Symbiodinium in 66 scleractinian coral species from 19 common genera. The internal transcribed spacer two (ITS-2) region in nuclear ribosomal DNA (rDNA) was used to identify the symbiont types following polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and sequencing. ITS-2 Symbiodinium types from clades A, C and D, previously reported in corals from other regions, were detected. While ITS-2 sequences from Symbiodinium clade C varied significantly, those from clades D and A did not. Most reef-building corals were found to be poor at forming symbioses with multiple symbiotic algae, indicating low adaptability to environmental change. This study followed ten years after the 1998 coral bleaching event and thus provided information needed for studies on temporal changes in Symbiodinium diversity in Tanzanian corals, especially in relation to large-scale bleaching events.Item Influence of local environmental conditions and bleaching histories on the diversity and distribution of Symbiodinium in reef-building corals in Tanzania(2016-04) Chauka, Leonard J.; Steinert, G.; Mtolera, M. S. P.Pollution, turbidity and coral bleaching history, as well as coral diversity, vary along the Tanzanian coastline. Prior to this study, it was not known whether exposure to such environmental variation might have influenced the diversity and distribution of Symbiodinium along this coastline. Such information can provide insight into whether Tanzanian reef-building corals develop adaptation to current trends of climate change. Here, 10 reef-building coral samples were collected from different reefs along the Tanzanian coast with different micro-environments and bleaching histories. The ITS-2 region of ribosomal DNA was employed in the characterisation of Symbiodinium harboured by reef-building corals. DGGE fingerprints and DNA sequences showed that most coral species host a single Symbiodinium type, which is maintained throughout the coast regardless of local environmental differences. We present polymorphic symbioses in Acropora spp., Millepora sp. and Galaxea fascicularis in mainly turbid and warm environments as a sign of adaptation to harsh conditions. However, such adaptation may not provide marked resistance to bleaching because Acropora is a bleaching-susceptible genus.Item Larvicidal Activity of Clausena Anisata Fruits and Leaves Extracts against Anopheles Gambiae Giless.S, Culex Quinquefasciatus Say and Aedes Egyptiae(2015) Makirita, Winisia E.; Chauka, Leonard J.; Chacha, JumaAim: The study aimed to evaluate larvicidal efficacy of Clausena anisata fruits and a leaf extracts against the 3rd instar Anopheles gambiae Giles s.s, Culex quinquefasciatus Say and Aedes egyptiae larvae. Methods: The protocol developed by the World Health Organisation was adopted with minor modifications. Results: The larvicidal activity study of Clausena anisata has revealed the selectivity of plant parts against the mosquito larvae. The leaf extracts displayed high potency against the 3rd instar Anopheles gambiae in which ethyl acetate leaf extract demonstrated high activity at LC50 of 0.0977 µg/mL followed by methanolic (LC50 0.9362 µg/mL) and chloroform (LC50 4.2384 µg/mL) extracts. The fruit ethyl acetate selectively exhibited the highest activity against A. egyptiae with LC50 of 5.3346 µg/mL. Culex quinquefasciatus larvae exhibited more resistance compared to A. gambiae and A. egyptiae larvae in which LC50 range of 78.658 – 178.895 µg/mL after 72 hours was displayed. Conclusion: The leaves and fruits of C. anisata are potential source of botanical mosquito repellants and thus employed for the management of mosquito borne diseases. Leaves extracts selectively exhibited activity against A. gambiae indicating its potential use in the control of malaria. Fruits ethyl acetate extract had better activity against A. egyptiae larvae suggesting its use in the management of dengue fever, chikungunya and yellow fever viruses. It is apparently evident that C. anisata leaf extracts possess high potency against A. gambiae larvae compared to Bacillus Thuringiensis, subsp. Israeliensis (BTI®) which is the larvicidal product with high specificity against mosquito larva.Item Molecular Ecology and Photo-Physiology of Symbiodinium Harboured by Tanzanian Reef Building Corals(2012-10) Chauka, Leonard J.Establishment of symbiosis with thermal tolerant Symbiodinium type is widely believed to be amongst the functional adaptation mechanism employed by reef-building corals (RBCs) to bleaching. In this study, Symbiodinium types found in 66 most common RBC species have been studied together with photo-physiology of the selected corals and their respective Symbiodinium with a view to evaluate Tanzanian reefs’ capacity to adapt to current trends of climate change. Internal transcribed spacer two (ITS-2) region of nuclear ribosomal DNA genes (rDNA) was used to identify the symbiont types. In addition, changes in photosynthetic pigment concentrations and ratios, synthesis of ultra violet absorbing substances, changes in Symbiodinium types and abundances, maximum quantum yield (Fv/Fm) and excitation pressure on PS II (Qm) were used to assess responses of corals and/or their associated Symbiodinium types to both thermal and photo-radiations in situ and/or ex-situ. It was found that, Symbiodinium cells harboured by RBC from Tanzania do not constitute a distinct genetic group from those in other parts of the world. Although they were found to be thermal and irradiance susceptible, Symbiodinium C3u and C3z dominate in Tanzanian reef-building corals. Shuffling of algal symbionts that hypothetically provide corals with thermal resistance is limited to few Tanzanian RBCs. The renown high bleaching resistance of Porites cylindrica as compared with other species was found to be contributed by its Symbiodinium C15’s ability to synthesize significantly higher concentrations of both carotenoids and UV-absorbing compounds. Besides, this study recognizes the contribution of the host to this ability. It is generally concluded that the rate at which Tanzanian RBC develop adaptations to current trends of climate change is not enough to survive from devastating effects of bleaching. Because a reverse of current trends of climate change is not a possibility, this thesis recommends useful management information and an urgent need of alleviating local anthropogenic threats on Tanzanian coral reef ecosystems to enhance their resilienceItem Tanzanian Reef Building Corals May Succumb to Bleaching Events: Evidences from Coral-Symbiodinium Symbioses: In S. Diop et al. (eds.), Estuaries: A Lifeline of Ecosystem Services in the Western Indian Ocean, Estuaries of the World(Springer, 2016-03) Chauka, Leonard J.Coral reefs are among the most vulnerable ecosystems to current trends of climate change. Most of the reef systems along the coast of Tanzania have remained severely damaged following the 1997/1998 El-Nin˜o that caused a massive coral bleaching, resulting into a wide spread of coral death. It is important therefore to find out/establish whether reef building corals develop adaptations to current trends of climate change so as to prioritise their conservation. There are evidences that coral-Symbiodinium-symbioses develop adaptation to current trends of climate change. This review therefore was meant to compare coral-Symbiodinium symbioses that occur along the Tanzanian coast with those occurring in others parts of the world. Like in most parts of the world, reef building corals along the Tanzanian coast are dominated by Symbiodinium clade C3 which is both thermal and irradiance intolerant. In the Tanzanian coast, coral genera that inmost part of the world have been found to host clade D, the Symbiodinium type whose distribution is correlated with warmer environment, host other Symbiodinium clades. Unlike in most part of the world, most of Tanzania’s reef building corals lack polymorphic symbioses, a phenomenon that is hypothetically believed to render environmental tolerance to the holobiont. This is probably due to lowseasonal variation in both temperature and solar radiations. Thus, Tanzanian corals become less advantaged in terms of impacts that may be associated with current trends of climate change.Item Variation in Symbiodinium ITS2 Sequence Assemblages among Coral Colonies. PLoS ONE 6:e15854(2011) Stat, Michael; Bird, Christopher E.; Pochon, Xavier; Pochon, Xavier; Chasqui, Luis; Chauka, Leonard J.; Concepcion, Gregory; Logan, Daniel D. K.; Takabayashi, Misaki; Toonen, Robert J.; Gates, Ruth D.Endosymbiotic dinoflagellates in the genus Symbiodinium are fundamentally important to the biology of scleractinian corals, as well as to a variety of other marine organisms. The genus Symbiodinium is genetically and functionally diverse and the taxonomic nature of the union between Symbiodinium and corals is implicated as a key trait determining the environmental tolerance of the symbiosis. Surprisingly, the question of how Symbiodinium diversity partitions within a species across spatial scales of meters to kilometers has received little attention, but is important to understanding the intrinsic biological scope of a given coral population and adaptations to the local environment. Here we address this gap by describing the Symbiodinium ITS2 sequence assemblages recovered from colonies of the reef building coral Montipora capitata sampled across Kāne'ohe Bay, Hawai'i. A total of 52 corals were sampled in a nested design of Coral Colony(Site(Region)) reflecting spatial scales of meters to kilometers. A diversity of Symbiodinium ITS2 sequences was recovered with the majority of variance partitioning at the level of the Coral Colony. To confirm this result, the Symbiodinium ITS2 sequence diversity in six M. capitata colonies were analyzed in much greater depth with 35 to 55 clones per colony. The ITS2 sequences and quantitative composition recovered from these colonies varied significantly, indicating that each coral hosted a different assemblage of Symbiodinium. The diversity of Symbiodinium ITS2 sequence assemblages retrieved from individual colonies of M. capitata here highlights the problems inherent in interpreting multi-copy and intra-genomically variable molecular markers, and serves as a context for discussing the utility and biological relevance of assigning species names based on Symbiodinium ITS2 genotyping.