Kinetoplast DNA in Trypanosoma equinum1

Identification and characterization of kDNA is described in the naturally occurring totally dyskinetoplastic species Trypanosoma equinum. Fluorescence microscopy of live cells, using the highly sensitive and specific probe DAPI (4,6,-diamidino-2-phenyl-indole), showed the presence of a diversity of extranuclear fluorescent bodies scattered along the length of the organism. Transmission electron microscopic studies revealed a close similarity between the distribution of these DAPI-fluorescing particles and of dense aggregates of nonfibrillar material resembling the kDNA of dyskinetoplastic strains of other species. Variable sized remnants of kDNA, occurring singly or in clusters, were found scattered throughout the mitochondrion. Analytical cesium chloride ultracentrifugation of total cellular DNA extracts showed a kDNA banding profile at a buoyant density equal to 1.691 gm/cm³, representing approximately 11% of the total cellular DNA content. Molecular spreads of isolated kDNA revealed a population of open circular molecules ranging in contour length from 0.11–9.69 μm.     

A test for Allee effects in the self‐incompatible wasp‐pollinated milkweed Gomphocarpus physocarpus

It has been suggested that plants that are good colonizers will generally have either an ability to self‐fertilize or a generalist pollination system. This prediction is based on the idea that these reproductive traits should confer resistance to Allee effects in founder populations and was tested using Gomphocarpus physocarpus (Asclepiadoideae: Apocynaceae), a species native to South Africa that is invasive in other parts of the world. We found no significant relationships between the size of G. physocarpus populations and various measures of pollination success (pollen deposition, pollen removal and pollen transfer efficiency) and fruit set. A breeding system experiment showed that plants in a South African population are genetically self‐incompatible and thus obligate outcrossers. Outcrossing is further enhanced by mechanical reconfiguration of removed pollinaria before the pollinia can be deposited. Self‐pollination is reduced when such reconfiguration exceeds the average duration of pollinator visits to a plant. Observations suggest that a wide variety of wasp species in the genera Belonogaster and Polistes (Vespidae) are the primary pollinators. We conclude that efficient pollination of plants in small founding populations, resulting from their generalist wasp‐pollination system, contributes in part to the colonizing success of G. physocarpus. The presence of similar wasps in other parts of the world has evidently facilitated the expansion of the range of this milkweed.     

Pilgrimella, a promitive Asiatic perissodactyl

The genus Pilgnmella , known from the medial Eocene of Pakistan and northwest India, is a primitive perissodactyl, not an artiodactyl as previously identified. Upper cheek teeth of Pilgrimella , when compared with those of primitive representatives of the Equoidea, Brontotherioidea, Chalicotherioidea, Tapirioidea and Rhinocerotoidea, suggest, however, that Pilgnmella cannot on present evidence be referred to any of the five accepted perissodactyl superfamilies. Pilgrimella may represent a short-lived and hitherto unknown perissodactyl lineage.     

The Products and Pathways of Glucose Catabolism in Herpetomonas muscarum ingenoplastis and Herpetomonas muscarum muscarum

ABSTRACT. The products and pathways of glucose catabolism in the insect trypanosomatids Herpetomonas muscarum ingenoplastis and Herpetomonas muscarum muscarum have been studied with the aim of elucidating how both organisms are able to proliferate well under aerobic and anaerobic conditions. When incubated in medium containing glucose as the only exogenous carbon source, catabolism was found to be fermentative in both cases. Acetate was a major product of both organisms while H. m. ingenoplastis produced more ethanol and propionate and less succinate than H. m. muscarum . Ethanol production by H. m. ingenoplastis decreased both under anaerobic conditions and in the presence of elevated CO₂ concentrations, whereas succinate and propionate release by this organism were greater in high CO₂ and anoxia, respectively. Succinate production by H. m. muscarum was greatest under anaerobic conditions in elevated CO₂ whereas propionate was only a minor product. The same four products were released during growth of the organisms in complex medium, but the relative proportions differed suggesting that other substrates were being used. Both organisms contained enzymes of the glycolytic and pentose phosphate pathways, but while all activities of the TCA cycle were present in H. m. muscarum . NAD-linked isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, succinate CoA synthase and succinate dehydrogenase were not detected in H. m. ingenoplastis . Fumarate reductase activity was present in both organisms. The data presented suggest that CO₂-fixation and reverse flux through the TCA cycle may be important factors that enable the organisms to undergo anaerobiosis.     

The Morphology and Evolution of the Ear in Actinopterygian Fishes

SYNOPSIS. In this paper we consider various aspects of the anatomyand ultrastructure of the actinopterygian ear and make a numberof suggestions on the possible adaptive significance of thestructural specializations. The focus of the arguments is basedupon the substantial inter-specific variation in teleost auditorysystems as measured anatomically, behaviorally, and physiologically.It is potentially of considerable significance that the majorpoints of inter-specific variation in the teleost ear are associatedwith the gross morphology and ultrastructure of the otolithicorgan most often implicated in sound detection, the sacculus.Analysis of patterns of sacculus ultrastructure has led to theconclusion that there are, in effect, only about five differentsaccular ultrastructural patterns but that these patterns arebroadly found throughout the teleost fishes. Based upon patternsof inter-specific variation in the sacculus and in other aspectsof the ear and more peripheral auditory structures (e.g., swimbladder),it is argued that adaptations encountered in the teleost auditorysystem cannot be used as reliable taxonomic indicators amongfishes. Rather, it is proposed that the teleost auditory systemis quite maleable in the evolutionary sense, and that interspecificsimilarities in many features of the auditory system reflectconvergent evoluuon, rather than phylogenetic affinities. Theactual selective pressures operating in the evoluuon of thefish auditory system are still essentially unknown. In addition,we cannot be certain that similar ear patterns in differentspecies reflect convergent evolution (or common ancestry), orthat conversely, different ear patterns among species reflectdifferences in auditory function.