PROTISTOLOGY

Thecamoeba onigiri n. sp. (Amoebozoa, Discosea, Thecamoebida) was isolated from a moss sample collected in the surroundings of Lake Baikal (Russia). The amoebae of this species belong to the striate morphotype and have a single rounded nucleus. The nucleolar material of T. onigiri can be organized in different ways depending on the age of the culture. The most common was a nucleus with a nearly spherical eccentric nucleolus, sometimes located very close to the nuclear envelope. The surface of such a nucleolus was rough and uneven. This type of nucleolar organization was observed in one- to two-week-old cultures. In contrast, a centrally located rounded nucleolus with smooth surface predominated in three- to four-week-old cultures. This type of the nucleolus corresponds to the classical “vesicular” nucleus and is similar to that found in amoebae of “T. quadrilineata species group”, but differs in having lacunae that are more peripheral. Molecular phylogenetic analysis based on 18S rRNA gene sequences showed that T. onigiri forms a clade with T. astrologa as part of a larger group that also includes the “T. quadrilineata species group” and T. aesculea. Meanwhile, two species of Thecamoeba demonstrate polymorphism of the nucleolar material arrangement, and both these species are phylogenetically close.

Although the global distribution of eumycetozoans in terrestrial ecosystems with varying vegetation types has been a subject of a number of investigations during the past decade, there is still scarce to no available data from the mangrove forests, particularly in the Philippines. Hence, this study assesses and compares the occurrence and distribution of protosteloid amoebae inhabiting the mangrove ecosystem of San Fernando City, La Union, with the villages Biday and Catbangen as representatives. Aerial (AL) and ground (GL) leaf litter samples were used as substrates in isolating protosteloid amoebae and were subjected to moist chamber cultures. The 17 species belonging to 12 genera, from a total of 125 records, were described and reported in this study, with Protostelium mycophagum being the most often occurring species. Further results indicate that the ground microhabitat and the Biday site exhibited higher species diversity and abundance than the aerial microhabitat and the Catbangen site. Regarding species richness in the two leaf litters, GL hosted higher species richness than AL. The current research is one of the few that has assessed and surveyed the eumycetozoan distribution, occurrence, and ecology in the Philippine mangrove ecosystem. Furthermore, it demonstrates the potential for a mangrove forest to support diverse protosteloid amoebae growth.