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Ranjiv D. Alibon

  • Biodiversity Journal, 12 (2): 0301-0311

    Shehada I. Tawasil, Ranjiv D. Alibon & Sophia L. Bensali
    Species diversity of Echinoderms in Manubul Island, Sulu Province, Southern Philippines
    https://doi.org/10.31396/Biodiv.Jour.2021.12.2.301.311

    ABSTRACT
    Echinoderms, often the most common marine organisms in the intertidal areas, are one of the target organisms in commercial fishing in Sulu Province, Southern Philippines. Proper regulation of Echinoderm harvesting requires a baseline data on its species diversity. Thus, we conducted a rapid survey of Echinoderms in the intertidal areas of Manubul Island, Sulu Province for three months to assess its species diversity using the Belt Transect Method. We identified 14 Echinoderm species through morphology-based identification with Tripneustes gratilla as the most frequently recorded species, comprising 17.94% of the total sightings. The recorded Echinoderms in Manubul Island is moderately diverse (H’= 2.089), possibly due to habitat heterogeneity (seagrass, mangrove, and beach ecosystems), and normal water conditions of the island (water temperature, pH, salinity and dissolved oxygen). Although most of the identified Echinoderm species in Manubul Island are common to other areas, the island was found to be a habitat of one data deficient species (Holothuria arenicola) and one endangered species (Holothuria scabra), and this has important implications on effective regulation of Echinoderm harvesting in the island in order to protect and conserve them as well as to attain its sustainable utilization.

  • Biodiversity Journal, 11 (3): 703-715

    Ranjiv D. Alibon, Alea Ester T. Ordoyo, Jessa Mae P. Gonzales, Melbert C. Sepe, Mark Anthony J. Torres & Genelyn G. Madjos
    Shell shape variation in populations of common cockle Anadara oceanica (Lesson, 1831) (Bivalvia Arcidae) from the intertidal areas of Margosatubig, Zamboanga del Sur (Philippines)
    https://doi.org/10.31396/Biodiv.Jour.2020.11.3.703.715

    ABSTRACT
    The advent of geometric morphometrics opened an area to study morphological variations in organisms. Thus, the aim of this study is to use outline-based geometric morphometrics to describe variations in the shell shapes of the left and right valves of Anadara oceanica (Lesson, 1831) (Bivalvia Arcidae) populations from the two neighbouring intertidal zones of Margosatubig, Zamboanga del Sur, Philippines. Herein, there were two levels of analyses that were employed: first, the shell shapes of the outer left and right valves between populations were compared; second, the shell shapes within population were quantitatively determined in terms of its symmetry. Results revealed significant variations both in the left and right valves of A. oceanica between populations. The variations observed are characterized by the deformations in the umbonal and anteroventral angles and in the dorsal, anterior and ventral margins of the outer shell both in the left and right valves. Although further studies are necessary in order to elucidate these variations, the second analysis revealed that the detected asymmetry in the shell shapes within A. oceanica populations was the cause of variation within populations that contributed to the significant variations between populations. Considering that the two sites are not geographically isolated, the results herein clearly proved that shell shape variation could also occur in neighbouring populations. The variations in the shell shapes of A. oceanica populations may have implications to habitat adaptation which aid in understanding the nature of this species especially those dwelling in the intertidal areas of Margosatubig, Zamboanga del Sur, Philippines.