INTRODUCTION

.In view of the growing importance of fish for native consumption, the resources of the African lakes are sure to be exploited in the near future, but it is essential to have a sound understanding of the fish and other fauna and flora in each lake before exploitation is started. This paper places on record the available data for Lake Rudolf and Lake Baringo, on which no previous ecological work had been attempted.
Lake Rudolf is characterized by a high temperature and very alkaline water, and contains a variety of environments inhabited by different fish-associations. The fauna has pronounced nilotic affinities, except that there is only one member of the family Mormyridae. Several species, however, have come to differ from their nilotic ancestors, and the comparison of the fauna with that of other waters can be used as evidence for past changes in the drainage systems of East Africa.
The fish fauna of Lake Rudolf is roughly divisible into three main associations of species–one in the inshore waters, one in the open water, and one near the bottom. Prom data supplied by large numbers of stomach examinations, the food-chains for each of these habitats can be reconstructed.
Lake Baringo is less warm, the water has a relatively low alkalinity, and is uniformly shallow and muddy. The fish fauna consists of few species, and shows affinities with that of the East African rivers which flow to the Indian Ocean.
Owing to the shallowness of Lake Baringo, there is no differentiation into species-associations, and the food-chains are complicated by the presence of food from the bottom in all the species of fish.
The bulk of this paper contains analyses of field-observations on the size, feeding and breeding habits of each of the species found in the lakes,     

Food web changes associated with drought and invasive species in a tropical semiarid reservoir

Hydrobiologia - Fish and invertebrates are introduced in freshwaters around the world for commercial purposes, despite widely known impacts on food webs and biological invasions. As a proxy for...     

Non-native fish species in Neotropical freshwaters: how did they arrive,and where did they come from?

The invasion of aquatic ecosystems by introduced invasive alien species (IAS) has become a worldwide phenomenon, and often leads to competitive interactions with native species. At high-nutrient levels, native species mostly are outcompeted by the introduced species. We performed an outdoor competition experiment between IAS free-floating Lemna minuta and native Lemna minor in a eutrophicated pond to examine whether the invasive species is the better competitor. We additionally performed an indoor experiment resembling mesotrophic phosphorus (P) conditions to investigate both species’ competitiveness in low P availability and compared with previous experiments at high-nutrient levels. Our results showed that in field conditions, the alien L. minuta was the better competitor. In the mesotrophic indoor condition, however, the native L. minor was the better competitor. Both species produced longer roots in the indoor experiment compared to field conditions. The species’ relative growth rates were also lower in the indoor experiment. A P reduction to mesotrophic condition in the water column thus might reduce invasive L. minuta growth and competitive performance. Additionally, introduction and recovery of L. minor could reduce L. minuta cover, but only following P reduction. Field experiments in mesotrophic ponds are needed to confirm these indoor findings.     

Dynamical study,hydrogen bond analysis,and constant pH simulations of the beta carbonic anhydrase of Methanobacterium thermoautotrophicum

Within the five classes (α, β, γ, δ, and ζ) of carbonic anhydrases (CAs) the first two, containing mammal and plant representatives, are the most studied among all CAs. In this study, we have focused our investigation on the beta-class carbonic anhydrase of Methanobacterium thermoautotrophicum. We investigated both the importance of the Asp-Arg dyad near the catalytic zinc-bound water and the possible roles that water molecules within the active site and residues near the entrance of the catalytic cleft have on the first step of the enzyme’s reaction mechanism. Hydrogen-bonding analysis of selected residues within the active site and constant pH replica exchange molecular dynamics constant pH replica exchange simulations were performed. The latter was done in order to evaluate the pK_a values of possible proton acceptors. We found an intricate hydrogen-bonding network involving two acidic residues within the active site, Asp16 and Asp34, and the catalytic water molecule. We also observed a very strong interaction between the zinc-bound water and residues Asp34 and Arg36. This interaction was not significantly affected by the change in the protonation state of both the catalytic water and aspartate residue 34. The pK_a analysis show that the effect of the R36A mutation affects not only the possible proton acceptors, but also the catalytic water itself.     

Comparative egg morphology of six Meccus species and Triatoma recurva (Stål, 1868) Hemiptera: Reduviidae

We investigated the morphology and morphometry of eggs from the colonies of the Entomology Laboratory at ENCB‐IPN belonging to six species of the genus Meccus and Triatoma recurva, using both light and scanning electron microscopy. Egg ornamentation is an important parameter to consider in the differentiation of species. Samples were observed under a scanning electron microscope. Measurements of fifty eggs per species included length, width, and opercular diameter, which were used for the morphometric analysis. The results showed that the seven species display a polygonal ornamentation dominated by hexagons; the operculum shows also a polygonal ornamental characteristic in each species. Morphometry provided valuable information for discriminating between closely related species of the genus Meccus and Triatoma recurva, a species akin to this group, thereby facilitating the complete discrimination of these species.