Ontogeny Studies On Several Representative Taxa In Myxogastria

The true slime molds(Myxomycetes or Myxogastria)compose a unique group of eukaryotic organisms with a special life cycle consisting of microscopic uninucleate amoeboflagellates,creeping multinucleate plasmodia and macroscopic stationary sporangia.This study based on 5 species belong to Stemonitales,Trichiales,Physarales.The individual development of this 5 myxogastria was studied by using solid microscopy,microscopy and laser confocal scanning microscopy,which revealed the common rules in the process of individual growth.The developmental process of Stemonitis herbatica,S.splendens,Collaria arcyrionema,Physarum flavicomum,and Metatrichia vesparia from spore germination to plasmodium formation and sporulation was studied.The results showed that all the myxomycetes produced swarm cells or myxamoebae during the developmental stage of spore germination.Swarm cells and myxamoebae are similar in morphology,structure and habits.However,the germination patterns of five kinds of myxomycetes were different: the spores of S.herbatica and S.splendens germinated by a “V” shape spolit.,the spores of C.arcyrionema,P.flavicomum,and M.vesparia germinated by a pore.In the plasmodium stage,three species of stemonitales all develop a typical aphanoplasmodium,which have similar morphology and structure.The aphanoplasmodium with a translucent and delicate structure,visible only under transmission light with unaided eyes.The plasmodium of the genus Physarales and Trichiales is a typical pheneroplasmodium,the pheneroplasmodium is thick and produces pigment,which is easy to observe.It can form large fan shape structure.Rhythmic protoplasm streaming in veins was observed both in two types of plasmodium.In the sporulation of P.flavicomum and M.vesparia,Sporocarp development type is Suprahypothallic.Sporulation characterized by the development of an exterior stalk.In the sporulation of S.herbatica and S.splendens,Sporocarp development type is Subhypothallic.Sporulation characterized by the development of an interior stalk,continuous with the hypothallus,but not with the peridium.In the sporulation of C.arcyrionema,although there are transparent membranous substance in the upside of the stalk connected with the inmatured peridia,however C.arcyrionema produces a brown hypothallus underneath the sprangial primordia prior to stalk formation which is the character of subhypothallic sporocarp development.Although the spores germination type is split,but it develops typical phaneroplasmodium.Collaria is a genus belonging to Stemonitales but have a closer relationship to physarales from ontogeny study.In general,there are characteristics of distinct species in the ontogeny of Myxogastria,but there are still general rules.The humidity,temperature and light conditions are the main factors that affect the sporulation of Myxogastria.