Biogeographic patterns and phylogeography of dwarf chameleons (Bradypodion) in an African biodiversity hotspot

The southern African landscape appears to have experienced frequent shifts in vegetation associated with climatic change through the mid-Miocene and Plio-Pleistocene. One group whose historical biogeography may have been affected by these fluctuations are the dwarf chameleons (Bradypodion), due to their associations with distinct vegetation types. Thus, this group provides an opportunity to investigate historical biogeography in light of climatic fluctuations. A total of 138 dwarf chameleons from the Cape Floristic Region of South Africa were sequenced for two mitochondrial genes (ND2 and 16S), and resulting phylogenetic analyses showed two well-supported clades that are distributed allopatrically. Within clades, diversity among some lineages was low, and haplotype networks showed patterns of reticulate evolution and incomplete lineage sorting, suggesting relatively recent origins for some of these lineages. A dispersal-vicariance analysis and a relaxed Bayesian clock suggest that vicariance between the two main clades occurred in the mid-Miocene, and that both dispersal and vicariance have played a role in shaping present-day distributions. These analyses also suggest that the most recent series of lineage diversification events probably occurred within the last 3-6 million years. This suggests that the origins of many present-day lineages were founded in the Plio-Pleistocene, a time period that corresponds to the reduction of forests in the region and the establishment of the fynbos biome.     

THE EXPRESSION OF APELIN AND ITS RECEPTOR APJ DURING DIFFERENT PHYSIOLOGICAL STAGES IN THE BOVINE OVARY

Recent studies implicate that apelin and its receptor APJ may have important role for the modulation of angiogenesis. The aim of this study was to further characterise the regulation of apelin/APJ system in bovine ovary. Experiment 1: corpora lutea (CL) were assigned to the following stages: days 1-2, 3-4, 5-7, 8-12, 13-16, >18 (after regression) of oestrous cycle and of gravidity (month <3, 3-5, 6-7 and >8). Experiment 2: Follicles during maturation were divided into granulosa cells (GC) and theca interna (TI) and were examined separately. Classification of follicles occurred by follicle size and oestradiol-17β (E2) concentration in the follicular fluid (FF) (<0.5 ng/ml, 0.5-5 ng/ml; 5-40 ng/ml; 40-180 ng/ml; >180 ng/ml). Real-time RT-PCR (qPCR) was applied to investigate mRNA expression of examined factors. In general, the expression level of apelin during the oestrous cycle was significantly higher compared to the one during pregnancy. Apelin mRNA levels were always high during the cycle with a tendency of decrease after CL regression. The APJ mRNA in the CL was significantly up regulated on days 5-7 and 8-12 followed by a decrease on days 13-16, and further on days >18. The expression of APJ does not show any significant regulation in the CL throughout pregnancy. The expression of apelin and APJ was not statistically regulated in GC, but was significantly up regulated in follicles with an E2 concentration of more than 5 ng/ml and showed an increase according to growth and maturation of follicles. In conclusion, our data suggest that apelin/APJ system is involved in the mechanism regulating angiogenesis during follicle maturation as well as during CL formation and function in the bovine ovary.     

Brood care in freshwater crayfish and relationship with the offspring's sensory deficiencies

Prolonged brood care is one of the evolutionary clues for the successful colonization of freshwater habitats by freshwater crayfish (Astacida). By means of macrophotography, light microscopy, and scanning electron microscopy we investigated all phases of brood care in freshwater crayfish, with particular emphasis on the morphological structures involved. We selected the recently discovered parthenogenetic marbled crayfish (species identity not yet known) as a model organism due to its fast reproduction and high resistance to handling stress. In order to examine if there is a causal relationship between brood care and the developmental status of the offspring's sensory apparatus, we additionally investigated major sense organs of juvenile Stages 1-5 in comparison with those of the adults. Brood care in the marbled crayfish is characterized by initial and final "active" phases dominated by specific maternal or juvenile behavior and a medial "passive" phase based more on the action of temporarily developed structures rather than on behavior. The most remarkable feature of this period, which includes permanent carrying of the eggs and the first two juvenile stages under the mother's abdomen, is safeguarding of hatching by a telson thread that keeps the helpless newborn hatchlings linked to the egg cases on the maternal pleopods and thus prevents them from being lost. Further important transient structures are the recurved hooks on the first pereiopods of Stage 1 and 2 juveniles that are used to firmly attach these nonfeeding stages to the mother's abdomen. In hatchlings all sense organs necessary for an independent life, such as eyes, olfactory aesthetascs, gustatory fringed setae, hydrodynamic receptor hairs, and statocysts are not developed or are underdeveloped, making brood care indispensable. Most of these sense organs appear in Stage 2 juveniles, but only from Stage 3, the first freelancing and feeding stage, are all sense organs well developed and operating, thus reducing brood care in this final period to temporary provisioning of shelter. Brooding of the eggs and postembryonic brood care are to some extent also found in other freshwater Decapoda like freshwater crabs and aeglid anomurans, but safeguarding of hatching is confined to the Astacida only. This sophisticated mode of passive brood care is unique in the animal kingdom and is apparently related to the sensory deficiencies of the first juvenile stage.     

Mitochondrial DNA sequence variation and phylogeographic patterns in harbour porpoises (Phocoena phocoena) from the North Atlantic

The harbour porpoise (Phocoena phocoena)experiences high rates of incidental mortalityin commercial fisheries, and in some areasthese rates are sufficiently high to justifyconcern over population sustainability. Giventhe high incidental mortality, the resolutionof population structure will be important toconservation and management, but in the NorthAtlantic the relationships among many of theputative populations remain unclear. Aprevious genetic study demonstrated substantialgenetic differences between eastern and westernNorth Atlantic populations, however thelocation of this break remained unresolved. Inthe present study, we addressed this issue byincluding new samples from Iceland. Toinvestigate population structure, variation inthe mitochondrial DNA of 370 porpoises wascompared among six locations corresponding toseveral of the putative populations (Gulf ofMaine, Gulf of St. Lawrence, Newfoundland, WestGreenland, Iceland, Norway). The first 342base pairs of the control region were sequencedand genetic variation investigated by analysisof molecular variance (F _ST and _ST ) and ² withpermutation. Although some fine scalepopulation structure was detected, porpoisesfrom Iceland were found to be more similar tothe western populations (W. Greenland, Gulf ofSt. Lawrence, Newfoundland, Gulf of Maine) thanto Norway. Furthermore, porpoises from Norwaywere different from all other regions. Thesepatterns suggest the existence of adiscontinuity between Iceland and Norway,possibly the result of isolating events causedby repeated range contractions and expansionsthroughout Quaternary glaciation events withinthe North Atlantic. These results suggest thatharbour porpoise populations within the NorthAtlantic are distinguishable, but patterns mustbe interpreted in light of their historicalbiogeography.     

Dusts causing pneumoconiosis generate .OH and produce hemolysis by acting as Fenton catalysts

Silicates causing pneumoconiosis function as Fenton catalysts to generate hydroxyl radicals (.OH) when incubated with hydrogen peroxide and a reducing substance. In contrast, silicates which do not cause pneumoconiosis demonstrate no Fenton activity. Catalytic activity is decreased by pretreatment of silicates with the iron chelators deferoxamine or transferrin. Hemolysis from silicates is decreased by interventions which remove superoxide anion or hydrogen peroxide from the medium, or by pretreatment of dusts with iron chelators. Thus, asbestos and nonfibrous silicates may cause pneumoconiosis through a common oxidant mechanism by catalyzing production of toxic .OH radicals in the lung.     

Ancient forest fragmentation or recent radiation? Testing refugial speciation models in chameleons within an African biodiversity hotspot

Aim East Africa is one of the most biologically diverse regions, especially in terms of endemism and species richness. Hypotheses put forward to explain this high diversity invoke a role for forest refugia through: (1) accumulation of new species due to radiation within refugial habitats, or (2) retention of older palaeoendemic species in stable refugia. We tested these alternative hypotheses using data for a diverse genus of East African forest chameleons, Kinyongia. Location East Africa. Methods We constructed a dated phylogeny for Kinyongia using one nuclear and two mitochondrial markers. We identified areas of high phylogenetic diversity (PD) and evolutionary diversity (ED), and mapped ancestral areas to ascertain whether lineage diversification could best be explained by vicariance or dispersal. Results Vicariance best explains the present biogeographic patterns, with divergence between three major Kinyongia clades (Albertine Rift, southern Eastern Arc, northern Eastern Arc) in the early Miocene/Oligocene (> 20 Ma). Lineage diversification within these clades pre‐dates the Pliocene (> 6 Ma). These dates are much older than the Plio‐Pleistocene climatic shifts associated with cladogenesis in other East African taxa (e.g. birds), and instead point to a scenario whereby palaeoendemics are retained in refugia, rather than more recent radiations within refugia. Estimates of PD show that diversity was highest in the Uluguru, Nguru and East Usambara Mountains and several lineages (from Mount Kenya, South Pare and the Uluguru Mountains) stand out as being evolutionarily distinct as a result of isolation in forest refugia. PD was lower than expected by chance, suggesting that the phylogenetic signal is influenced by an unusually low number of extant lineages with long branch lengths, which is probably due to the retention of palaeoendemic lineages. Main conclusions The biogeographic patterns associated with Kinyongia are the result of long evolutionary histories in isolation. The phylogeny is dominated by ancient lineages whose origins date back to the early Miocene/Oligocene as a result of continental wide forest fragmentation and contraction due to long term climatic changes in Africa. The maintenance of palaeoendemic lineages in refugia has contributed substantially to the remarkably high biodiversity of East Africa.     

The effect of sediment redox potential on nitrogen uptake,anaerobic root respiration and growth of Spartina alterniflora loisel

A system developed for growing plants in estuarine sediment at controlled redox potential (Eh) was used to study the effect of Eh on anaerobic root respiration, uptake of added labelled nitrogen and photosynthetic rates of Spartina alterniflora Loisel. Plant growth, estimated by CO₂ fixation and nitrogen uptake, was not affected by sediment redox potential ranging from oxidized (+500 mV) to strongly reducing (?200 mV). Anaerobic root respiration, evident by alcohol dehydrogenase activity, increased with decreasing sediment redox potential. The results suggest that neither redox potential per se nor anaerobic root respiration can account for the growth differences of S. alterniflora observed in Louisiana's coastal marshes.