Health and chemical burdens of fish species from polluted and hyper-eutrophic freshwater ecosystems in South Africa

Three aquatic ecosystems in South Africa, the Hartbeespoort, Klipvoor and Bospoort Dams, are classified as hyper-eutrophic, because of high nutrient loads and chemical pollution. Water and two fish species, Clarias gariepinus and Cyprinus carpio, were collected from these dams to assess the impact of eutrophication and chemical pollutants on their health status. Water and muscle samples were analysed for organic and inorganic chemicals. Condition factor was determined and a necropsy performed to note any macroscopic abnormalities. A histology-based fish health assessment was done on the liver, kidney, gills and gonads. A number of fish from the three dams exhibited livers with fatty change and focal discoloration, skin lesions and parasites within the visceral cavity. The prevalence and severity of histopathology in the liver resulted in higher liver index values than the index values for kidneys and gills. Aluminium, silicon and chromium were detected in the water and muscle tissue. The DDT metabolite p,p’-DDE was present in both species, as well as in fish from the reference site, Marico-Bosveld Dam. Only C. gariepinus from Hartbeespoort Dam had p,p’-DDD levels higher than 5 µg g^?1 per edible portion. Water from hyper-eutrophic dams adversely affects the health of freshwater fish.     

Non-secretory solitary plasmacytoma of the spleen

A case of primary nonsecretory plasmacytoma of the spleen is reported. On laparotomy and splenectomy a 920 g spleen was removed, measuring 16×14×6 cm. The cut surface of the entire spleen showed that the tumour occupied most of the splenic tissue. A bone marrow aspirate and trephine, skeletal survey showed no signs of myeloma. Biopsy of the liver and regional lymph nodes was normal. Immunocytochemistry of the splenic tumour showed positivity for pan-B and plasma cell markers. After splenectomy the patient was treated with chemotherapy according to protocol VBCMP (M2).     

The Flexibility of Bacterial Cell Walls

S ummary . There are considerable differences in the extensibility of the cell walls of bacteria in different genera. Gram negative spp. examined were more flexible than the Gram positive ones.     

Not going with the flow: a comprehensive time‐calibrated phylogeny of dragonflies (Anisoptera: Odonata: Insecta) provides evidence for the role of lentic habitats on diversification

Ecological diversification of aquatic insects has long been suspected to have been driven by differences in freshwater habitats, which can be classified into flowing (lotic) waters and standing (lentic) waters. The contrasting characteristics of lotic and lentic freshwater systems imply different ecological constraints on their inhabitants. The ephemeral and discontinuous character of most lentic water bodies may encourage dispersal by lentic species in turn reducing geographical isolation among populations. Hence, speciation probability would be lower in lentic species. Here, we assess the impact of habitat use on diversification patterns in dragonflies (Anisoptera: Odonata). Based on the eight nuclear and mitochondrial genes, we inferred species diversification with a model‐based evolutionary framework, to account for rate variation through time and among lineages and to estimate the impact of larval habitat on the potentially nonrandom diversification among anisopteran groups. Ancestral state reconstruction revealed lotic fresh water systems as their original primary habitat, while lentic waters have been colonized independently in Aeshnidae, Corduliidae and Libellulidae. Furthermore, our results indicate a positive correlation of speciation and lentic habitat colonization by dragonflies: speciation rates increased in lentic Aeshnidae and Libellulidae, whereas they remain mostly uniform among lotic groups. This contradicts the hypothesis of inherently lower speciation in lentic groups and suggests species with larger ranges are more likely to diversify, perhaps due to higher probability of larger areas being dissected by geographical barriers. Furthermore, larger range sizes may comprise more habitat types, which could also promote speciation by providing additional niches, allowing the coexistence of emerging species.