Morphological and temporal variation in early embryogenesis contributes to species divergence in Malawi cichlid fishes

The cichlid fishes comprise the largest extant vertebrate family and are the quintessential example of rapid “explosive” adaptive radiations and phenotypic diversification. Despite low genetic divergence, East African cichlids harbor a spectacular intra- and interspecific morphological diversity, including the hyper-variable, neural crest (NC)-derived traits such as coloration and craniofacial skeleton. Although the genetic and developmental basis of these phenotypes has been investigated, understanding of when, and specifically how early, in ontogeny species-specific differences emerge, remains limited. Since adult traits often originate during embryonic development, the processes of embryogenesis could serve as a potential source of species-specific variation. Consequently, we designed a staging system by which we compare the features of embryogenesis between three Malawi cichlid species—Astatotilapia calliptera, Tropheops sp. ‘mauve’ and Rhamphochromis sp. “chilingali”—representing a wide spectrum of variation in pigmentation and craniofacial morphologies. Our results showed fundamental differences in multiple aspects of embryogenesis that could underlie interspecific divergence in adult adaptive traits. First, we identified variation in the somite number and signatures of temporal variation, or heterochrony, in the rates of somite formation. The heterochrony was also evident within and between species throughout ontogeny, up to the juvenile stages. Finally, the identified interspecific differences in the development of pigmentation and craniofacial cartilages, present at the earliest stages of their overt formation, provide compelling evidence that the species-specific trajectories begin divergence during early embryogenesis, potentially during somitogenesis and NC development. Altogether, our results expand our understanding of fundamental cichlid biology and provide new insights into the developmental origins of vertebrate morphological diversity.     

Antitoxic immunity against the so-called lung toxin produced by Escherichia coli.

Cross neutralization test with antisera to crude haemolysins produced by some Escherichia coli strains indicated that there were no antigenic differences among the haemolysins tested. These crude preparates showed definite cytotoxicity which could also be cross neutralized by "antihaemolysin" sera. Neutralization experiments were performed in mouse lung test with homologous and heterologous anti-haemolysin sera, and with O and OK sera to the wild type strain and its toxic R mutant. The results showed that the immunity in the mouse lung model is antitoxic and antibacterial.     

An altered heart-labile enterotoxin (LT') produced by Escherichia coli serogroup O55 strain.

An Escherichia coli serogroup O55 strain produced heat-labile enterotoxin only, which exerted unusual effects on cell cultures; it caused elongation of CHO and HeLa cells but no changes in Y-1 cells. Injection of this substance, designated LT', into mouse foot pad and rabbit skin caused a well-expressed necrotic effect beside the LT-like activity. LT' showed no cytotoxic effect and failed to produce mouse lung oedema. The strain was not haemolytic. According to Sephadex G-100 fractionation, the LT' had a high molecular weight. The LT' and the necrotic activities could not be separated by fractionation. Neutralization experiments suggested an antigenic relationship between LT and LT'. The antigenic deficiency of LT' was closely related to the common antigenic component of LT and choleragen. The necrotic effect caused by crude LT' was neutralized only by the homologous serum.     

Pathogenic effect of enterotoxigenic Escherichia coli and Escherichia coli causing infantile diarrhoea.

Macroscopic, light and electron microscopic alterations in ligated rabbit intestinal loops challenged with five standard enterotoxigenic Escherichia coli (ETEC) and twenty-three enteropathogenic E. coli (EEC-I) strains, freshly isolated from infantile enteritis cases, were investigated. Only two O26 : K60 : H11 strains produced enterotoxin. Their living cultures, sterile filtrates of the fluid medium and ultrasonic lysates of the bacteria resulted in pronounced hypersecretion of the intestinal epithelium followed by fluid accumulation and loop dilatation. These two E. coli strains, similarly as the other loop-negative EEC-I strains, were able to penetrate into the intestinal epithelium. In contrast to the standard ETEC strains, the EEC-I bacteria, adhering to the brush border, intruded into the microvilli, multiplied on the outer epithelial cell membrane making close contact with it and, causing, shedding of microvilli, penetrated into enterocytes becoming enclosed in membrane-bound phagosome-like vacuoles, appeared in the lamina propria and elicited mild focal polymorphonuclear infiltration.     

Microbial tropicalization driven by a strengthening western ocean boundary current

Western boundary currents (WBCs) redistribute heat and oligotrophic seawater from the tropics to temperate latitudes, with several displaying substantial climate change‐driven intensification over the last century. Strengthening WBCs have been implicated in the poleward range expansion of marine macroflora and fauna, however, the impacts on the structure and function of temperate microbial communities are largely unknown. Here we show that the major subtropical WBC of the South Pacific Ocean, the East Australian Current (EAC), transports microbial assemblages that maintain tropical and oligotrophic (k‐strategist) signatures, to seasonally displace more copiotrophic (r‐strategist) temperate microbial populations within temperate latitudes of the Tasman Sea. We identified specific characteristics of EAC microbial assemblages compared with non‐EAC assemblages, including strain transitions within the SAR11 clade, enrichment of Prochlorococcus, predicted smaller genome sizes and shifts in the importance of several functional genes, including those associated with cyanobacterial photosynthesis, secondary metabolism and fatty acid and lipid transport. At a temperate time‐series site in the Tasman Sea, we observed significant reductions in standing stocks of total carbon and chlorophyll a, and a shift towards smaller phytoplankton and carnivorous copepods, associated with the seasonal impact of the EAC microbial assemblage. In light of the substantial shifts in microbial assemblage structure and function associated with the EAC, we conclude that climate‐driven expansions of WBCs will expand the range of tropical oligotrophic microbes, and potentially profoundly impact the trophic status of temperate waters.     

Can the use of zooplankton dormant stages from natural wetlands contribute to restoration of mined wetlands?

Wetlands are among the most diverse environments on the planet and are strongly threatened by human activities. Their restoration and/or mitigation of human impacts, therefore, relies on information that can aid to the management of impacted wetlands so that they return to a (semi-) natural state. We investigate in this study the relationship between dormant stages of zooplankton and clay removal in areas subjected to mining. We evaluate whether a gradual increase in topsoil addition from donor natural wetlands to the sediment of mined wetlands influenced the zooplankton community. Eight wetlands were sampled in the Sinos River floodplain, four natural and four mined. In the laboratory, four field sediment samples were incubated for zooplankton hatching in five treatments comprising sediments from: mined wetlands, natural wetlands, and three treatments containing mined sediments added with low (5%), medium (20%) and high (40%) quantities of sediment from natural wetlands. Hatching consisted of 61 individuals distributed across eight zooplankton taxa. Copepod nauplii were the most abundant (31.1%) followed by Epiphanes sp. (29.5%) and Ovalona glabra (16.4%). While natural wetlands provided 42.6% of the hatched zooplankton, mined wetlands had just 6.5%. Zooplankton richness and abundance were higher in natural wetland sediments compared with mined and added sediment wetlands. To some degree, the sediment soil donation from natural to mined wetlands was considered viable. As long as prior studies are performed to test the size and quality of the dormant banks present in the sediment of candidate donor wetlands, sediment from donor wetlands may aid in the establishment of a more diverse community in disturbed systems.

     

Role of Zinc in Zinc-α2-Glycoprotein Metabolism in Obesity: a Review of Literature

Biological Trace Element Research - Excessive adipose tissue promotes the manifestation of endocrine disorders such as reduction of the secretion of zinc-α2-glycoprotein (ZAG), an adipokine...