The role of fish-poultry integration on fish growth performance,yields and economic benefits among smallholder farmers in sub-Saharan Africa,Tanzania

Aquaculture practices from sub-Saharan Africa are characterised by low production, owing to improper technology. Production can be increased through integrating fish farming with other existing on-farm activities, particularly livestock husbandry. We assessed the role of fish-poultry integration on all male Nile tilapia, Oreochromis niloticus growth performance, yields and economic benefits among smallholder farmers in sub-Saharan Africa, Tanzania. The study also compared phytoplankton species composition, abundance and biomass between the fish-poultry integration and non-integrated system. After 180 days of the experiment, all male O. niloticus cultured under fish-poultry integration exhibited significantly higher growth rates than those in the non-integrated system (p < 0.05). Gross fish yield (GFY), net fish yield (NFY) and net annual yields (NAY) obtained from fish-poultry integration were significantly higher than those from non-integrated system (p < 0.05). Partial enterprise budget analysis revealed that fish-poultry integration was more profitable than the non-integrated system. Moreover, fish-poultry integrated system produced significantly higher phytoplankton abundance and biomass than those from the non-integrated system. Results demonstrate that rural smallholder farmers can achieve higher growth rate, farm net yields and income by integrating all male O. niloticus with other on-farm activities than practising a stand-alone fish culture system.     

Nuclear gene trees and the phylogenetic relationships of the mangabeys (Primates: Papionini)

Phylogenetic relationships of mangabeys within the Old World monkey tribe Papionini are inferred from analyses of nuclear DNA sequences from five unlinked loci. The following conclusions are strongly supported, based on congruence among trees derived for the five separate gene regions: (1) mangabeys are polyphyletic within the Papionini; (2) Cercocebus is the sister taxon to the genus Mandrillus; and (3) Lophocebus belongs to a clade with Papio and Theropithecus, with Papio as its most likely sister taxon. Morphologically based phylogenies positing mangabey monophyly were evaluated by mapping the sequences for each locus on these trees. The data seem to fit these trees poorly in both maximum-parsimony and likelihood analyses. Incongruence among nuclear gene trees occurred in the interrelationships among Lophocebus, Papio, and Theropithecus. Several factors that may account for this incongruence are discussed, including sampling error, random lineage sorting, and introgression.      

Independent Neuronal Origin of Seizures and Behavioral Comorbidities in an Animal Model of a Severe Childhood Genetic Epileptic Encephalopathy

The childhood epileptic encephalopathies (EE’s) are seizure disorders that broadly impact development including cognitive, sensory and motor progress with severe consequences and comorbidities. Recently, mutations in DNM1 (dynamin 1) have been implicated in two EE syndromes, Lennox-Gastaut Syndrome and Infantile Spasms. Dnm1 encodes dynamin 1, a large multimeric GTPase necessary for activity-dependent membrane recycling in neurons, including synaptic vesicle endocytosis. Dnm1^Ftfl or “fitful” mice carry a spontaneous mutation in the mouse ortholog of DNM1 and recapitulate many of the disease features associated with human DNM1 patients, providing a relevant disease model of human EE’s. In order to examine the cellular etiology of seizures and behavioral and neurological comorbidities, we engineered a conditional Dnm1^Ftfl mouse model of DNM1 EE. Observations of Dnm1 ^Ftfl/flox mice in combination with various neuronal subpopulation specific cre strains demonstrate unique seizure phenotypes and clear separation of major neurobehavioral comorbidities from severe seizures associated with the germline model. This demonstration of pleiotropy suggests that treating seizures per se may not prevent severe comorbidity observed in EE associated with dynamin-1 mutations, and is likely to have implications for other genetic forms of EE.     

A chromatographic tool for preparing combinatorial quinone-thiol conjugate libraries

Quinones are well established as key players in the production of reactive oxygen species within cellular environments. Many factors govern their cytotoxicity but most studies have been restricted to a few, core, derivatives. A new strategy for the in situ production of quinone derivatives has been developed such that libraries of diverse functionality can be rapidly created without recourse to extensive synthetic procedures. The approach relies upon nucleophilic addition by reduced thiol derivatives to the quinone core within a pre-culture assay mixture and provides a generic strategy that exploits the large reservoir of commercial thiols currently available. A readily accessible chromatographic method has been developed that allows the derivatisation process to be easily monitored and the purity of the resulting one pot preparation to be assessed. The viability of the combinatorial approach has been fully validated through comparison with a range of quinone-S-conjugates prepared using conventional bench synthesis. The latter have been fully characterised.     

Haemolytic activity of live Phaeocystis pouchetii during mesocosm blooms

Chemical defence is a potential mechanism contributing to the success of Phaeocystis species that repeatedly dominate the phytoplankton in coastal areas. Species within the genus Phaeocystis have long been suspected of imposing negative effects on co-occurring organisms. Recently a number of toxins have been extracted and identified from Phaeocystis samples, but it is not clear if they do enhance the competitive advantage of Phaeocystis species. In the present study the cytotoxic impact of live Phaeocystis pouchetii to human blood cells in close proximity, regardless of the nature of the responsible mechanism, was quantified using a bioassay. Haemolytic activity was measured during blooms of P. pouchetii in mesocosms. These environments were chosen to mimic natural conditions including chemically mediated interactions that could trigger defensive and/or allelopathic responses of Phaeocystis. Haemolytic activity correlated with P. pouchetii numbers and was absent during the preceding diatom bloom. Samples containing live P. pouchetii cells showed the highest activity, while filtered sea water and cell extracts were less haemolytic or without effect. Dose-response curves were linear up to 70% lysis, and haemolysis in samples containing live P. pouchetii cells reached EC₅₀ values comparable to known toxic prymnesiophytes (1.9 * 10⁷ cells l⁻¹). Haemolytic activity was enhanced by increased temperature and light. The results indicate that unprotected and thus presumably vulnerable cells present in a P. pouchetii bloom may lyse within days.