Philippine Journal of Science
154 (2): 301-318, April 2025
ISSN 0031 – 7683
Date Received: 12 Nov 2024

Kimverly T. Leseguis, Jeremy B. Romero, Arvin U. Pacoma,
Robert Jay N. Ramos, Deo Florence L. Onda, Mitsunori Iwataki,
Koyo Kuwata, and Leni G. Yap-Dejeto

A toxic epibenthic dinoflagellate Coolia malayensis is reported for the first time in Cancabato Bay, Tacloban City, the Philippines. Typically found in tropical and subtropical waters, this genus is observed to often coexist with other ciguatoxigenic dinoflagellates. Two strains of C. malayensis were established into clonal cultures, both producing mucus as a common characteristic of benthic dinoflagellates. Based on LM and SEM, cells were globular with slightly asymmetrical theca, and its apical pore plate and 2ʹ plate ratio shared close morphometrics (0.74 ± 0.02 µm) with C. malayensis. Phylogenetic analysis based on the LSU rDNA and ITS regions placed the Cancabato isolate in the clade of C. malayensis from other areas. The pilot screening of C. malayensis showed hemolytic activity, which might be light-triggered. Its hemolytic activity peaked at its exponential phase. C. malayensis tolerated salinities ranging from 20–35 ppt, and salinity significantly affected its cell sizes across the various treatments. In this study, the complementary identification of C. malayensis isolated from Cancabato Bay expanded its geographical range to include Philippine waters.