Using Morphology and a Molecular Barcode to Characterize the Potentially Toxigenic Diatom Pseudo-Nitzschia (Bacillariophyceae) from Luzon Island Mariculture Zones
Date of Award
12-1-2023
Document Type
Thesis
Degree Name
Master of Science in Biology
First Advisor
Janice A. Ragaza, PhD
Abstract
Harmful algal blooms are a major concern for the environment and industries like fisheries, healthcare, and tourism in coastal countries such as the Philippines. Blooms of diatoms (Bacillariophyceae) seldom cause harm, but half of the species under the cosmopolitan genus Pseudo-nitzschia produce the neurotoxin domoic acid. The Philippines only has two published Pseudo-nitzschia surveys. Both based their species identification on morphological characters alone. Since then, molecular taxonomy has revealed a high level of cryptic diversity corresponding to minute morphological differences that can be overlooked. This study sought to explore and characterize the genus Pseudo-nitzschia in mariculture zones within Luzon Island using morphological and molecular information. Ten culture strains of Pseudo-nitzschia isolated from shellfish farms in Pagbilao and Bacoor Bay were used for morphological and molecular-based species identification. The secondary structure of the internal transcribed spacer 2 region revealed five strains from Pagbilao to be most similar to P. brasiliana, perhaps the first record of this species in Luzon. Meanwhile, four Bacoor isolates and one from Pagbilao clustered within a monophyletic clade representing P. pungens, previously found in Manila Bay. Morphological characters, specifically cell shape, apex shape, and poroid density confirmed both species identities. Based on cingular band poroids, all P. pungens strains were of the nominal variety, P. pungens var. pungens. Both P. pungens and P. brasiliana can produce domoic acid. This study represents the first integration of molecular barcoding for diatom taxonomy in the Philippines, further confirming the presence of potentially toxin-producing microalgae in our coastal ecosystems.
Recommended Citation
Botavara, Lorenzo A., (2023). Using Morphology and a Molecular Barcode to Characterize the Potentially Toxigenic Diatom Pseudo-Nitzschia (Bacillariophyceae) from Luzon Island Mariculture Zones. Archīum.ATENEO.
https://archium.ateneo.edu/theses-dissertations/848
