Pilobolus

Pilobolus belonging Zygomycota

1. ZYGOMYCOTA

2. Zygospore All are terrestrial Saprobes – Saprophytes or Coprophilous Parasites – Pin mold - Attack Fungi, insect or protozoa

3. Zygomycetes - features Cell wall – Chitin- chitosan Motile cells are completely absent Asexual reproduction by means of non – motile sporangiospores Sexual reproduction by gametangial copulation Zygospore is a resting structure Zygospore germinate to produce promycelium with terminal sporangium

4. Pilobolus

5. The family Pilobolaceae is characterized by the explosive shooting of the entire sporangium . 25 species (10 from India) P. Kleinii

6. Pilobolus   (‘Shot Gun’ Fungus or the ‘Hat-Thrower’) ‘ coprophilous ’ fungus, i.e., it is found on the dung of herbivore animals (horse, cow, sheep, rabbit, etc .) Requires cow dung decoction

7. Thallus : Eucarpic The hyphae are coenocytic , aseptate and much branched; Hyaline remain submerged in the dung characteristic sporangiophores arise from the hyphae .

8. Asexual Reproduction: Aplanospores with in sporangium Sporangiophores may be terminal or intercalary in position on the mycelium . If it arises terminally, the sporangiophore initially is cut off by a single septum, and by two septa if intercalary. The sporangiophores , 0.5 to 1 cm high, are strongly phototropic.

9. It consists of a bulbous basal cell ( trophocyst ) embedded in the dung; a straight stalk - Sporangiophore , which enlarges apically to form a crystal-clear sub- sporangial vesicle, A comparatively small, black sporangium.

10. The sporangium is separated from the sporangiophore by a columella . The sporangium contains 15,000 to 30,000 spores. The entire sporangium is thrown off violently with a speed of 14 metres per second towards light up to a distance of about 2 metres . This forceful discharge gives the fungus names such as the ‘shot-gun fungus’ and ‘hat-thrower’.

11. Subsporangial vescicle helps in dispersal of spores Sap inside vesicle has high presssure (7atm) The vesicle below the sporangium explodes transversely just beneath the columella . Accompanied by contraction of the walls of sporangiophores Resulting in squirting out of the cell sap from the open mouth.

12. The sporangia fall on grasses, and along with the grasses reach the alimentary canal of herbivore animals. The spores pass undamaged through the alimentary canal, where they receive the pre- treatment stimulation for their germination later in the deposited dung. The periodicity of sporangial production in Pilobolus is a rhythmic phenomenon. Successive crops of sporangia appear each morning at a definite interval of 24 hours and are discharged in the afternoon. Such rhythmic phenomena (which are several and occur in many organisms other than fungi) are called circadian rhythms or 24 hour ‘biological clock’. https://blog.mycology.cornell.edu/2006/12/14/pilobolus-and-the-lungworm/ https://www.youtube.com/watch?v=iOanDmeVn3c https://av.tib.eu/media/10374

13. Sexual Reproduction: The genus has both heterothallic and homothallic species. Fusion of two multinucleate gametangia of opposite strains leads to the formation of a thick, smooth-walled zygospore . The suspensors are twisted around each other and then separated like the jaws of a pair of tongs. The zygospore is held by their tips.

14. After a period of dormancy, the zygospore germinates and forms a sporangiophore and sporangium. Meiosis occurs and haploid spores are produced in the sporangium. The germination of the zygospore , however, has been infrequently seen. It can germinate directly producing a mycelium.