Species belonging to the toxic dinoflagellate Alexandrium tamarense complex can cause Paralytic Shellfish Poisoning, have a global distribution, but their occurrence in the tropics has never been established. In this study, the morphology, phylogeny, and toxicity of A. pacificum (Group IV) were examined using cultures established from two different geographic locations in the Philippines. Our analyses were based on light microscopy, confocal laser scanning microscopy, high-performance liquid chromatography (HPLC), and molecular phylogeny inferred from LSU and SSU rDNA. Cellular and thecal plate morphology of the Philippine strains showed characters typical of the species complex such as an isodiametric cell shape, chain formation (maximum of two cells), absence of ventral pore, isodiametric posterior sulcal plate, although these characters were not enough to assign a species designation. Phylogenetic analyses however revealed the well-supported placement of the Philippine strains in the A. pacificum (Group VI) and thus confirm their species identification. Paralytic shellfish toxins (PSTs) were detected in our two tested cultures, with N-sulfocarbamoyl C1/C2 as the most abundant toxin component and toxicity level ranging from 32.70–38.18 fmol of STX eq cell-1. The present study confirmed the occurrence of A. pacificum (Group IV) in the tropics.
Tree species serve as phorophytes for many epiphytic pteridophytes as they support their existence and survival. This study was conducted to investigate the host tree preferences of epiphytic pteridophytes in the montane forest formation of Mt. Apo Natural Park (MANP), Cotabato Province, Philippines. Sixteen 20 m x 20 m plots were established in each of the two sites, namely the Energy Development Corporation – Long Term Ecological Research area (EDC-LTER) and the Makalangit Trail. Within the sampling plots, all potential phorophytes were sampled and categorized for the presence of epiphytic ferns. Leaf and bark structural characteristics and bark chemical constituents were analyzed in determining the phorophyte preference of epiphytic pteridophytes. A total of 1,474 individual phorophytes were documented belonging to 46 species, predominantly tree ferns (Cyatheaceae) which serve as substrate for 79 species of pteridophytes. In terms of leaf characteristics, 547 individual phorophytes in Makalangit and 225 in EDC-LTER, were characterized as nanophyllous. Most phorophytes had barks characterized as hard, rough, and not scaly. The result of regression analysis showed that the bark thickness of the tree substrates was determined to be the best predictor of the number of phorophytes (p≤0.001), abundance (p≤0.001), species richness (p≤0.004), and diversity p≤0.018). Moreover, the number of phorophytes is also significantly influenced by light intensity (p≤0.037) and DBH (p≤0.041). Additionally, the analysis of bark chemistry and its relation to epiphytic pteridophyte abundance at the EDC-LTER site unveiled significant correlations with %Mg (r = 0.674; p-value = 0.016) and total K (r = 0.715; p-value = 0.009) content of the bark.
The spread of both invasive and endemic parasites in the Philippines particularly through the co-introduction of invasive alien fish species (IAFS) poses potential threats to local fauna. However, the limited research and data on fish parasites in the country make it difficult to accurately assess the extent and seriousness of these threats. This study documents the presence of several IAFS within the Marikina River system and explores their endoparasitic diversity. From the 187 IAFS collected, only seven IAFS individuals are found to be infected. Four species were identified from 177 isolated individual parasites. These were cestode Bovienia serialis (Bovien, 1926), trematode Masenia bangweulensis (Beverley-Burton, 1962), and nematodes Camallanus sonaiensis Lebanan and Mohilal, 2021, and a Contracaecum Railliet and Henry, 1912 species. Clarias gariepinus (Linnaeus, 1758) represents a new host record for B. serialis. This study contributes to future research and management of the Marikina River with environmental, socioeconomic, and public health implications.
