Reproductive biology and the life cycle of the diatom alga Nitzschia cf. Thermaloides inhabiting mud volcanoes of the Crimea

Abstract

Nitzschia cf. thermaloides Hustedt was found in large quantity in samples taken from puddles and lakes formed in the areas of action of mud volcanoes of the Bulganak volcano field (Kerch Peninsula, Republic of Crimea). The aim of this work was to study the reproductive biology and life cycle of the algae from a biotope with extremely high levels of illumination, temperature, and salinity. Individual clones were isolated from the samples by micropipette method and introduced into culture, crossing of which made it possible to initiate heterothallic sexual reproduction. For the first time for this species, a description of the sexual process corresponding to type IB2a according to Heitler's classification is given. The cardinal points (the critical sizes of cells that determine the transition from one phase of the life cycle to another) have been determined. The full range of cell sizes from the initial ones that appeared as a result of sexual reproduction to the smallest ones observed when kept in culture is given. The main postulates of the theory of the life cycle are considered, which make it possible to analyze the natural population. It has been found that the population of N. cf.  thermaloides exists in the sampling site for a long time and is represented by cells in all phases of the life cycle.

Keywords: diatoms, Nitzschia cf. thermaloides, mud volcanoes, sexual reproduction, life cycle