Life History of Basidiobolus ranarum (Entomophthoraceae)

Access this item (login required):

Description: This film describes the asexual and sexual reproduction of Basidiobolus ranarum in vitro and includes step by step growth and mitosis, conidia formation and discharge, formation of gametangia and gametangiogamy, with subsequent zygote formation. Released in 1984
Duration: 12 mins 03 secs
Director: Prof. Dr. Ch. Thielke
Credits: Author: Prof. Dr. Ch. Thielke, Institut für Pflanzenphysiologie und Zellbiologie der Freien Universität Berlin. Produced by Dr. T. Hard, E. Poloczek, C. Ludwig, Institut für den Wissenschaftlichen Film, Göttingen.
Year: 1982
Subjects: Plant genetics, Fungi, Plant physiology, Cell biology
Segment 1: IWF credit title. Main title in German. Intertitle in German: 'Stepwise growth and mitosis'. The commentary states that the mycelium of basiobolus ranarum develops a stepwise growth, which is shown in time-lapse. During this special type of growth the protoplast creeps apically. The viewer is told that the hyphal segment left by the moving protoplast is periodically cut off by septi, which occurs in hourly (approximately) cycles. A chain of empty cell chambers remains. The next shot illustrates that each protoplast contains an unusually large nucleus which follows the growing apex. The commentary states that this type of septation of hyphal compartments has been developed by only a few fungi. A new shot shows that in phase contrast the nucleus can be recognised more clearly. It contains a large dark nucleolus. The viewer is told that periodically a mitosis interrupts the stepwise growth. In the shot two daughter nuclei appear, separated by a septum. The nucleolus is shown dispersing during prophase. The commentary states that polar caps are formed. The next shot illustrates that during telophase both daughter nuclei separate. The viewer is told that once more the nucleolus and the nuclear membrane fade away during prophase. A new shot shows that the spindle axis and the later metaphase plate are oriented at an oblique angle to the cell wall. The polar caps appear dark. Between them the very small chromosomes form the metaphase plate and separate quickly during anaphase. The commentary continues by explaining that as a result of this mitosis both daughter nuclei are separated by a septum. The next shot illustrates that the septum is formed centripetally. The left cell is now branching, which is shown, while the distal one proceeds according to the stepwise growth. The viewer is told that the nucleus migrates into the branching hyphal tip. Branching in this way the mycelium is able to colonise a larger area. Fades to black.
Segment 2: Intertitle in German: 'Conidia formation and discharge'. The first shot of this sequence illustrates that, induced by light, conidiophores develop on the surface of an agar block within about 40 minutes. The commentary states that their conidia are discharged by a tergal mechanism, which is shown. The direction of shooting is determined by the light. The viewer is told that at the tip of each aerial hypha first a swelling and later the conidium itself are differentiated. The next shot shows the conidium developing as a bud at the tip of a vesicle. The commentary continues by explaining that during this process the cytoplasm streams acropetally as is the case in the vegetative hypha. The viewer is told that the conidiophorous cell is emptied, leaving behind the vacuole, which follows the cytoplasm. The rest of the cytoplasm streams in the form of a central strand. The commentary states that the streaming stops when the septum at the basis of the conidium is complete. The viewer is told that now the turgid pressure inside the vesicle increases and four to six minutes later it ruptures and the conidium is discharged. The next shot illustrates that if explosion is prevented, the cell sap escapes and the vesicle shrinks. A new shot shows that the preformed rim marks the spot where the vesicle will rupture. The viewer is told that animated graphics will now be used to elucidate this phenomenon. At high tergal the vesicle is separated from its stipe. Vacuole fluid escapes. The commentary continues by explaining that the elastic energy of the turgescent vesicle has become a kinetic one. Simultaneously the cell walls are shrinking. The viewer is told that the ballistic phenomenon is also illustrated by use of animated graphics. The carrier system stabilises the flight path and separates from the conidium, and the conidium flies 1 to 2 centimetres before landing. A new image illustrates that sometimes a shrunken carrier vesicle is seen on the substrate and at a greater distance a conidium is shown. The commentary explains that the conidium germinates if conditions are favourable. The next shot shows that nuclear divisions proceed and septi are formed. The viewer is told that a new mycelium develops on the principle of stepwise growth. The next image illustrates that at low nutrient levels the conidium develops directly into a new conidiophore. The commentary explains that within 2 to 3 hours this again forms a conidium which will be discharged after a few minutes. This process is shown. From the surface of an agar block, on the left of the picture, conidiophores are shooting towards the direction of the light, coming from the right. Several generations of conidia are shown spreading out to the right. The viewer is told that within 28 hours up to 7 generations were registered. They have covered a distance of several centimetres. Fade to black.
Segment 3: Intertitle in German: 'Formation of zygotes'. The commentary states that normally the mycelium of basidiobolus ranarum develops gametangia and zygospores after 2 days, and this development is illustrated. The viewer is told that it is probable that a sexual reaction is induced by a low nutrient level. A new shot illustrates that the production of zygotes, which takes place in most of the vegetative cells, proceeds on the same pattern of stepwise growth. The next image shows that the gametangia are derived from adjacent somatic cells. Their complete protoplast is absorbed by the fusion. The commentary continues by stating that the differentiation of the gametangia is characterized by the fact that both cells form beak-like projections which are entered by the nuclei. This process is shown. The viewer is told that later gametangiogamy occurs with the transit of the protoplasm. The septum below the beaks is broken. The commentary explains that the cytoplasm grows denser and streams into the right gametangium, which has now become a macro-gametangium. The adjacent hyphal segments empty and are cut off by new septi. The commentary continues by stating that while the nuclei in the beaks are dividing synchronously, the plasmatic movement decreases. Of the four resulting nuclei, two remain in the beaks where they degenerate and the other two fuse. The viewer is told that they are not visible inside the dense protoplasm. During maturation, a thick cell wall is developed protecting the zygote. The commentary ends by stating that these resistant zygospores enable the organism to survive unfavourable environmental conditions. Closing credits. IWF credit title.
Persistent URL: http://edina.ac.uk/purl/isan/0014-0000-2835-0000-0-0000-0000-0
Written and compiled by the British Universities Film & Video Council © BUFVC 2005
Subject classification by University of Edinburgh Library © 2006