'Cand. Actinochlamydia clariae' gen. nov., sp. nov., a Unique Intracellular Bacterium Causing Epitheliocystis in Catfish (Clarias gariepinus) in Uganda

Background and Objectives: Epitheliocystis, caused by bacteria infecting gill epithelial cells in fish, is common among a large range of fish species in both fresh-and seawater. The aquaculture industry considers epitheliocystis an important problem. It affects the welfare of the fish and the resulting gill disease may lead to mortalities. In a culture facility in Kampala, Uganda, juveniles of the African sharptooth catfish (Clarias gariepinus) was observed swimming in the surface, sometimes belly up, showing signs of respiratory problems. Histological examination of gill tissues from this fish revealed large amounts of epitheliocysts, and also presence of a few Ichthyobodo sp. and Trichodina sp. Methods and Results: Sequencing of the epitheliocystis bacterium 16S rRNA gene shows 86.3% similarity with Candidatus Piscichlamydia salmonis causing epitheliocystis in Atlantic salmon (Salmo salar). Transmission electron microscopy showed that the morphology of the developmental stages of the bacterium is similar to that of members of the family Chlamydiaceae. The similarity of the bacterium rRNA gene sequences compared with other chlamydia-like bacteria ranged between 80.5% and 86.3%. Inclusions containing this new bacterium have tubules/channels (termed actinae) that are radiating from the inclusion membrane and opening on the cell surface or in neighbouring cells. Conclusions: Radiation of tubules/channels (actinae) from the inclusion membrane has never been described in any of the other members of Chlamydiales. It seems to be a completely new character and an apomorphy. We propose the name Candidatus Actinochlamydia clariae gen. nov., sp. nov. (Actinochlamydiaceae fam. nov., order Chlamydiales, phylum Chlamydiae) for this new agent causing epitheliocystis in African sharptooth catfish

Gonadal development and intersex condition of marbled lungfish, Protopterus aethiopicus (Heckel, 1851), in contaminated sites in Lake Victoria, Uganda

The first evidence of the impact of environmental contamination on populations of Protopterus aethiopicus (Heckel, 1851) in terms of body indices, cellular development (histology) and intersex condition in Lake Victoria, Uganda is provided. Specimens were obtained from the more polluted swampy areas receiving wastes from residential and industrial settings (Ggaba, n = 11; Port Bell, n = 10; and Jinja, n = 7), and rural, less polluted areas (Bukakata, n = 3; Kasensero, n = 4; and Bale, n = 2), and gonadosomatic indices, growth condition factor and the morphometric body characteristics were determined. Fish specimens in less polluted sites had better condition and shapes, regardless of sex, compared with those in more polluted sites of the lake. Most lungfish collected had a total length of 45–55 cm. Irrespective of sex of fish and level of pollution at collection sites, samples (n = 26) collected inshore (1 063.42 g ± 109.32 SE) were heavier than those collected (n = 11) offshore (680.09 g ± 108.85 SE), F(1, 35) = 6.288, p = 0.019. Mean values of gonadosomatic indices were significantly higher in less polluted sites, compared with chemically contaminated urban sites (F(5, 31) = 2.783, p = 0.034), suggesting better growth performance in the former. Spermatogenic cell development progressed as spermatogonia, spermatocytes, spermatids and spermatozoa among males. For oogenic cells, development was through chromatin nucleolar, perinucleolar, cortical alveolar, early vitellogenic and late vitellogenic oocytes. Histological examinations revealed group asynchronous gonadal development and intersex condition among P. aethiopicus populations in Lake Victoria. Keywords: asynchronous gonadal development, environmental contamination, gonadosomatic indices, lake pollutio

A critical review of macroinvertebrate-based bioassessment approaches in Africa’s lotic systems: developments, challenges, and legal requirements

Worldwide, water resources have an impact on all forms of life as lotic systems are networks that interconnect water resources and land. They are important for navigation, water supplies, agriculture, recreation, and industrial development and help to regulate changes in climate and support social, spiritual, educational, and ecosystem health services. These ecosystems are, however, facing both natural and anthropogenic threats. Anthropogenic threats are driven by population increase, economic development, and catchment degradation. They are now the most threatened resources worldwide, and in Africa in particular. To design proper management strategies, the causes and impacts of the threats must be properly diagnosed. Monitoring and assessment approaches that show degradation and integrate it over time are essential to generate data and information required by water managers for decision making. Biomonitoring using macroinvertebrates is an effective tool in this regard, because it integrates causes of degradation and aquatic biotic responses to the impacts thereof. This review summarises the needs, challenges, and legal implications of biomonitoring in Africa using lessons from countries with successful biomonitoring as benchmarks

Diversity of benthic macroinvertebrates in anthropogenically disturbed Aturukuku River, Eastern Uganda

Biodiversity conservation has focused on large vertebrates and plants with pronounced economic value, compared with smaller organisms such as benthic macroinvertebrates that play a particular role in freshwater ecosystems. The increasing loss and degradation of  freshwater habitats, coupled with low taxonomic and ecological knowledge and limited conservation efforts in the tropical regions,  threaten macroinvertebrate biodiversity. This study investigated spatial and seasonal variability in benthic macroinvertebrate diversity and the underlying environmental variables within the Aturukuku River in Tororo, Uganda. Benthic macroinvertebrates were evaluated by  comparing their composition at a reference site in the upstream rural area with two urban midstream sites and one rural downstream site during dry and wet seasons in 2018. Benthic macroinvertebrate diversity in the Aturukuku River was lower than that reported from least disturbed small rivers within the same region; with moderate to high pollution tolerant taxa, dominating. Chironomidae, Oligochaeta and Simulium sp. predominated at the urban sites receiving sewage and abattoir effluent. The Shannon–Wiener diversity index, species  richness and species evenness in the river were generally low. Prosobranch (Thiaridae) snails and bivalves (Sphaeridae) were among the taxa with low tolerance to changes in the river. Canonical Correspondence Analysis revealed that total nitrogen, dissolved oxygen,  temperature and streambed substrate were predominant in structuring benthic macroinvertebrate assemblages. There was no potential species-rich area for macroinvertebrate conservation, given the poor environmental conditions and diversity in the entire river. However, specific mitigation measures against the declining quality of the river are recommended, to boost conservation of macroinvertebrates and the entire riverine ecosystem. Keywords: environmental stress, macroinvertebrate conservation, pollutants, promoting awareness, self-purification, small ecosystem

Determination of the Connectedness of Land Use, Land Cover Change to Water Quality Status of a Shallow Lake: A Case of Lake Kyoga Basin, Uganda

Catchments for aquatic ecosystems connect to the water quality of those waterbodies. Land use land cover change activities in the catchments, therefore, play a significant role in determining the water quality of the waterbodies. Research on the relationship between land use and land cover changes and water quality has gained global prominence. Therefore, this study aimed at determining land use, land cover changes in the catchments of L. Kyoga basin, and assessing their connectedness to the lake’s water quality. The GIS software was used to determine eight major land use and land cover changes for 2000, 2010, and 2020. Meanwhile, water quality data was obtained through both secondary and primary sources. Spearman correlation statistical tool in SPSS was used to correlate the land use, land cover changes, and water quality changes over the two-decade study period. The results showed that different land use and land cover activities strongly correlated with particular water quality parameters. For example, agriculture correlated strongly with nutrients like TP, TN, and nitrates and turbidity, TSS, BOD, and temp. The correlation with nitrates was statistically significant at 0.01 confidence limit. The findings of this study agreed with what other authors had found in different parts of the world. The results show that to manage the water quality of L. Kyoga, management of land use, land cover activities in the catchment should be prioritized. Therefore, the results are helpful to decision and policy makers and relevant stakeholders responsible for water management

Recent Climate Change in the Lake Kyoga Basin, Uganda: An Analysis Using Short-Term and Long-Term Data with Standardized Precipitation and Anomaly Indexes

Climate change (CC) is now a global challenge due to uncertainties on the drivers and the multifaceted nature of its impacts. It impacts many sectors such as agriculture, water supply, and global economies through temperature and precipitation, affecting many livelihoods. Although there are global, regional, and national studies on CC, their application to determine local CC occurence mitigation and adaptation measures is not ideal. Therefore, this study aimed to determine climate change trends in Lake Kyoga Basin using standardized precipitation and anomaly indexes. Short-term (39 years, 1981–2020) and long-term (59 years, 1961–2020) monthly data from eight strategic meteorological stations were acquired from the Uganda National Meteorological Authority and supplemented with satellite and model reanalysis climate datasets. Change in precipitation was determined by SPI-6, while SAI determined change in temperature. The Mann–Kendall test was used to determine the trend significance. Whereas two (Serere and Lira) long-term data stations showed significant changes in precipitation, all the short-term data stations showed a significant increasing trend. Decadal relative rainfall anomaly increased from 85.6–105 in 1981–1990 to 92.0–120.9 in 2011–2020, while mean temperature anomaly increased from 0.2–0.6 °C to 1.0–1.6 °C in the same period. The frequency of severe wet weather events was more than for dry weather events in many stations, indicating an increase in precipitation. Maximum, mean, and minimum temperatures increased, with resultant warmer nights. The findings showed that the Lake Kyoga basin is experiencing climate change, with both temperature and rainfall increasing spatially and temporarily. Climate change affects agriculture, which is the main economic activity, and causes the destruction of infrastructure from floods, landslides, and mudslides. The results of this study are helpful in pointing out climate change-affected areas, and hence for designing mitigation and adaption strategies for local communities by policy and decision-makers from relevant stakeholders

Semi-thin sections of infected primary lamellas from African sharptooth catfish.

<p>Pictures of semi-thin sections of the primary gill lamellas from African sharptooth catfish infected with <i>Candidatus</i> Actinochlamydia clariae. Arrows point to cysts of variable sizes. The majority of the cysts are located towards the apical part of the primary lamellas. A) Bar = 60.0 µm. B) Bar = 30.0 µm.</p

Paraffin sections from gill tissues.

<p>The sections of gill tissue from <i>Clarias gariepinus</i> have been processed for <i>in situ</i> hybridization or stained with HES. A) Primary filament showing dark-blue stained <i>Candidatus</i> Actinochlamydia clariae inclusions, stained with antisense DIG-labelled RNA-probe against <i>Ca.</i> A. clariae 16S rRNA. Cells with inclusions are particularly frequent at the filament tip. Bar = 100.0 µm. B) Same primary filament stained with a sense probe, demonstrating absence of staining in the inclusions (examples indicated by arrows). Bar = 100.0 µm. C) HES stained section of the same filament tip. Bar = 100.0 µm. D) Magnification of an IHC stained inclusion, where the actiniae are discernible (arrowhead). Bar 10.0 = µm.</p

Phylogenetic tree.

<p>The phylogenetic tree shows the relationship between <i>Candidatus</i> Actinochlamydia clariae from African sharptooth catfish and selected members of other families within the order Chlamydiales. The best-fitting nucleotide substitution model was used during maximum likelihood analysis and the tree was bootstrapped (50 000 quartet puzzling steps) in TREE_PUZZLE. The scale bar shows the number of nucleotide substitutions as a proportion of branch lengths.</p

Nucleotide similarity of <i>Ca</i>. Actinochlamydia clariae (Accession nos: JQ480299, JQ480300, JQ480301) compared to other members of the order Chlamydiales.

<p>Nucleotide similarity of <i>Ca</i>. Actinochlamydia clariae (Accession nos: JQ480299, JQ480300, JQ480301) compared to other members of the order Chlamydiales.</p