The diversification of South American murid rodents: evidence from mitochondrial DNA sequence data for the akodontine tribe

Phylogenetic relationships based on 801 base pairs (bp) of the mitochondrial cytochrome b gene are examined for eight genera and 28 species of the akodontine tribe of South American murid rodents. The akodontine tribe comprises some 35% of the total diversity of the subfamily Sigmodontinae, but the current taxonomy at virtually all levels is uncertain because of inadequate generic diagnoses and assessments of variation and trends in traditional morphological characters. Monophyly of the tribe cannot be resolved by the sequence data, based on comparisons to outgroup taxa in three other tribes (Oryzomyini, Phyllotini, and Thomasomyini). However, highly corroborated monophyletic units within the group are obtained in a variety of both parsimony and distance analyses. These include a redefined and numerically dominant genus Akodon (with Microxus and Hypsimys as synonyms), Bolomys, Lenoxus, Oxymycterus, and a strongly supported assemblage that includes the central Andean Chroeomys and 'Akodon' andinus and the southern Abrothrix, 'Akodon' olivaceus, and the long-clawed mice of the genera Notiomys, Geoxus, and Chelemys. Sequence divergence within species is typically less than 5%, although levels can reach 10% for some highly polytypic forms. Divergence among genera within the tribe reaches 35% in corrected estimates, a level that is as great as that among representatives of different tribes. Changes in the current classification of akodontines are suggested based on these data, and the timing and place of origin of the tribe and its radiation is discussed.     

Aminopeptidases from Plasmodium falciparum, Plasmodium chabaudi chabaudi and Plasmodium berghei

ABSTRACT. Using fluorogenic substrates and polyacrylamide gels we detected in cell-free extracts of Plasmodium falciparum, Plasmodium chabaudi chabaudi and Plasmodium berghei only a single aminopeptidase. A comparative study of the aminopeptidase activity in each extract revealed that the enzymes have similar specificities and kinetics, a near-neutral pH optima of 7.2 and are moderately thermophilic. Each has an apparent molecular weight of 80,000 ± 10,000, determined by high performance liquid chromatography on a calibrated SW500 column. Whilst the P. c. chabaudi and P. berghei activity co-migrate in native polyacrylamide gels, that of P. falciparum migrates more slowly. The three enzymes can be selectively inhibited by ortho -phenanthroline and are thus metallo-aminopeptidases; however, in contrast to other aminopeptidases the metal co-factor does not appear to be Zn²⁺.     

Trypanosoma Manulis N. Sp. From the Russian Pallas Cat Felis Manul

ABSTRACT. The morphology of Trypanosoma manulis n. sp. is described from living and stained specimens obtained from the blood of a Pallas cat, Felis manul , from Kazakhstan. the cat was also infected with a Hepatozoon sp. and feline immunodeficiency virus. the morphology of the trypanosome most closely resembles that of Trypanosoma mpapuense Reichenow and Trypanosoma heybergi Rodhain found in bats. Trypanosoma manulis does not grow well in conventional media, but co-culture with African green monkey kidney cells in Eagle's Minimum Essential Medium supplemented with 10% fetal calf serum at approximately 27° C resulted in luxuriant growth of trypanosomes. Under these growth conditions, epimastigotes adhered to the surface of the culture flask and to African green monkey kidney cells, as well as forming large rosettes. At 37° C, although growth was poor, transformation of the epimastigotes into the bloodstream forms occurred. This represents the first report of a trypanosome of the subgenus Megatrypanum in a felid.     

Effects of variation in ear temperature on growth and yield of spring wheat

Wheat plants were kept in a growth room at 15 ^oC from 7 days after an-thesis until maturity and their ears were warmed to 20 or 25 ^oC for various periods. Continuous warming initially increased the growth rate of the ear and decreased that of the stem, but hastened senescence of the ear and decreased final grain yield by decreasing dry weight per grain. Warming the ears increased the movement of ¹⁴C and nitrogen to them from the leaves and stem during the early stages of grain growth but decreased it later. Warming the ears for only the first 10 or 20 days also hastened ear senescence; grain yield decreased progressively with increase in duration of the warm period. All effects were greater at 25 than at 20 ^oC. The effects of changing ear temperature from 15 to 20 ^oC were independent of the temperature of the rest of the plant. Altering the humidity of the air around the ears by 4–7 mb at constant temperature had no effect on ear growth or senescence. Warming all of the plant except the ears from 15 to 20 ^oC increased ear growth slightly during early grain growth and decreased it later, irrespective of ear temperature: stem dry weight, leaf area and net photosynthetic rate of flag leaves and green stems were decreased and dark respiration rate of stems was increased.     

The Structure and Development of Himanthalia lorea (L.) Lyngb1

The development of H. lorea has been followed in detail andcomparisons made between comparable stages of development ofplante from exposed and from sheltered habitats. The origin and course of the longitudinal hyphae ie traced,and it is found that the distance behind the apex at which theyarise varies at different stages of development. The very pronounced surface growth leads to extreme elongationof the medullary cells which also develop characteristic dilationsat the horizontal septa. In the receptacles the production of the horizontally runninghyphae appears to be connected with the formation of centralair-spaces. In the older receptacles the cells of these hyphaebecome extremely swollen and form irregular blocks of pseudo-parenchymatoustissue. The production of longitudinal hyphae is more marked in plantsfrom more exposed habitats, and the inner cortex has thickerwalled cells where the plants have to endure longer periodsof intertidal exposure.     

Flag Leaf Anatomy of Triticum and Aegilops Species in Relation to Photosynthetic Rate

Quantitative anatomical and other measurements were made onfully expanded flag leaves of a series of diploid, tetraploidand hexaploid Triticum and Aegilops species, and photosyntheticrates per unit leaf area were measured at light saturation (P_max). Diploids had the highest P_max, hexaploids the lowest with tetraploidsbeing intermediate. The anatomical features of tetraploids andhexaploids were generally similar, but different from the diploids.The diploids had thinner leaves with less dry matter and chlorophyllper unit area. The surface area of the mesophyll cells per unitvolume of mesophyll tissue was similar for all ploidy levels,as was the ratio mesophyil cell surface area per unit leaf area.It is argued that while these anatomical features are unlikelyto account for the observed variation in Pmax, it is possiblethat other structural factors with which they are correlatedmay causally influence P_max. One such feature is the averagediffusion path length from the plasmalemma at the cell surfaceto the sites of carboxylation. Anatomy, photosynthesis, mesophyll, cell size, Triticum, Aegilops, polyploidy