Philippine Journal of Science 150 (S1): 281-297, Special Issue on Biodiversity ISSN 0031 - 7683 Date Received: 22 Sep 2020 Diversity of Echinoderms in Intertidal and Shallow-water Areas of Samal Island, Philippines Maybelle A. Fortaleza*, Joemarie J. Lanutan, Junissa M. Consuegra, and Cleto L. Nañola Jr. Coral Reef Resiliency and Ecology Studies Laboratory College of Science and Mathematics, University of the Philippines Mindanao Mintal, Davao City, Davao del Sur 8000 Philippines Echinoderms are immediately observable around the coastal shores of Samal Island. Unfortunately, studies on echinoderm diversity are lacking despite its relevance to coastal and marine ecosystems management. This study attempts to update the existing records of echinoderms in Samal Island, however, limited to the intertidal and shallow-water areas. Field surveys from January 2018 to January 2019 yielded a total of 30 echinoderm species belonging to 17 families. Most of the echinoderms encountered belonged to Classes Asteroidea (sea stars, nine species) and Ophiuroidea (brittle stars, nine species), followed by Echinoidea (regular and irregular urchins, six species) and Holothuroidea (sea cucumbers, six species). Of the 1,015 individuals, sea urchins comprised the majority of the total individuals recorded (43.15%), succeeded by sea stars (30.44%), brittle stars (18.04%), and sea cucumbers (8.37%). Richest diversity was observed in Catagman with 23 echinoderm species recorded. This was followed by Camudmud (14 species), Pangubatan (eight species), Balet (seven species), Aundanao (six species), and Kaputian (three species). The five most commonly occurring species were the Echinometra mathaei (Blainville, 1825), Archaster typicus (Müller and Troschel, 1840), Ophiocoma scolopendrina (Lamarck, 1816), Diadema setosum (Leske, 1778), and Linckia laevigata (Linnaeus, 1758). Differences in distribution and abundance may be attributed to the variability of habitats available across sites. An intensive biodiversity assessment is recommended to evaluate how the physicochemical parameters and extent of anthropogenic activities shape the diversity and distribution of echinoderms on the island. The current work also provides the first documentation of ophiuroid diversity and the first record of the brittle stars, Breviturma krohi (Stöhr, Boissin & Hoareau, 2013) and Ophiocoma cf. cynthiae (Benavides- Serrato and O’Hara, 2008) in Samal Island, Philippines. Keywords: diversity, echinoderms, intertidal areas, Samal Island INTRODUCTION unsurprising given that holothuroids and asteroids are highly regarded for their economic and aesthetic values. Echinoderms from Classes Holothuroidea and Asteroidea In contrast, studies related to Crinoidea, Echinoidea, are among the well-studied taxa in Mindanao, particularly and Ophiuroidea are relatively few. Crinoids are popular in Davao Gulf (Gamboa et al. 2004; Bos et al. 2008a) subjects in underwater photography; however, taxonomic and Sarangani Bay (Pitogo et al. 2018). This comes works concerning feather stars in the Philippines are *Corresponding Author: [email protected] limited (Clark 1909; Messing 2003; Arguelles et al. 281 Philippine Journal of Science Fortaleza et al.: Echinoderms of Samal Island Vol. 150 No. S1, Special Issue on Biodiversity 2010). Philippine studies on echinoids have focused eTrex20). Each site was characterized in terms of mostly on economically important sea urchins such as monsoonal exposure (Matsumoto et al. 2020), slope the gracious sea urchin Tripneustes gratilla (Linnaeus, (Emery 1961), relief (Benkendorff and Thomas 2007), 1758) (Juinio-Meñez et al. 2008; Casilagan et al. 2013), and substrate type (Table 1). whereas ophiuroid studies date back to Domantay and Domantay (1966) and Domantay and Conlu’s (1968) Macro-invertebrate surveys consisted of day and night works. Although echinoderms are among the most observations conducted once every full moon week conspicuous components of intertidal and shallow-water of the month. Two 50-m belt transects with two-meter areas, it is evident that reports on biodiversity or species observation width were laid on the intertidal (high, mid, composition are lacking (Bos et al. 2008a). and low) and shallow-water areas parallel to the shore. Sampling for the echinoderms included low tide reef Published works that provided diversity information walks, snorkeling in shallow-water areas, and inspection on some echinoderms in Davao Gulf include Bos et al. of the underside of rocks and crevices. All echinoderms (2008a) who documented 11 asteroid species from Samal encountered every 5 m were recorded and photographed. and Talikud Islands, Davao del Norte, and Sonico (2018) The corresponding habitat type where they were seen was who reported five regular sea urchin species from Punta also noted. Dumalag, Davao City. Other studies that were related to echinoderms of Davao Gulf have focused on the The list of echinoderms, common names, pooled relative population dynamics of the horned sea star Protoreaster abundance, and conservation status is reported in Table 2. nodosus (Linnaeus, 1758) (Bos et al. 2008b), population Following the criteria of Pearse (2009), the pooled relative biology of the sand-sifting sea star Archaster typicus abundance of echinoderms was considered “scarce” (Müller and Troschel, 1840) (Bos et al. 2011), spatio- when only 1–4 individuals were found. “Common” was temporal distribution of the crown-of-thorns starfish assigned to echinoderms with 5–25 individuals present (COTS) Acanthaster planci (Linnaeus, 1758) (Agustin and “abundant” when there were more than 25 individuals and Nañola 2013), and its management during outbreaks observed. The corresponding conservation status of (Bos et al. 2013), documentation of the gleaning, drying, echinoderms listed was based on the International Union and marketing practices of sea cucumbers (Subaldo 2011), for Conservation of Nature (IUCN) Red List of Threatened and the supply chains and cost-benefit analyses of its Species (IUCN 2020). fishery and trade in Davao del Sur (Shuck et al. 2013). All echinoderms were identified using published While there are a number of research efforts concerning literature (see Table 3). Initial species identifications echinoderms of Davao Gulf, most of these were only and those that were unidentified were verified by limited to particular echinoderm taxa. Our knowledge of experts through personal communication. Diagnoses of their overall diversity, including those coming from other the echinoderm species encountered in Samal Island, classes, remains insufficient. Moreover, it is important Philippines are provided in Table 3. Species descriptions to consider that previous works may have been done discuss the morphological characteristics that served as the but have remained unpublished, which unfortunately basis for their identification. Habitat refers to the actual adds to the existing research gap as far as documenting habitat where the echinoderms were observed, including the local marine biodiversity is concerned. The current additional information from published literature. Lastly, work provides a preliminary report on the diversity and the information on local distribution is based on published distribution of echinoderms limited to the intertidal and sources, although most echinoderms listed are commonly shallow-water areas of Samal Island. Documenting the encountered by tourists, recreational divers, or underwater local diversity is of utmost importance to strengthen the enthusiasts anywhere in the country. protection and management efforts in Davao Gulf as one of the marine key biodiversity areas in the country. RESULTS AND DISCUSSION A total of 30 echinoderm species belonging to 17 METHODS families were recorded from six intertidal and shallow- Six rocky intertidal areas located in Barangays Aundanao, water areas of Samal Island, Davao del Norte (Table 2). Balet, Camudmud, Catagman, Kaputian, and Pangubatan Most of the echinoderm species recorded came from the in the Island Garden City of Samal, Davao del Norte Classes Asteroidea (Figure 2) and Ophiuroidea (Figure 3) were visited monthly from January 2018 to January 2019 with nine species, followed by Echinoidea (Figure 4) and (Figure 1). The geographic coordinates of each site Holothuroidea (Figure 5) with six species. Of the 1,015 were recorded using a handheld GPS device (Garmin individuals observed, echinoderms from Class Echinoidea 282 Philippine Journal of Science Fortaleza et al.: Echinoderms of Samal Island Vol. 150 No. S1, Special Issue on Biodiversity Figure 1. Map showing the six study sites in Samal Island, Davao del Norte, Philippines where the macro-invertebrate surveys were conducted. Map was created in R software (R Core Team 2018) using the shape file downloaded from the Philippine GIS Data Clearinghouse (retrieved on 10 Sep 2020 from http://philgis.org). Table 1. Description of the six intertidal and shallow-water areas studied in Samal Island, Davao del Norte, Philippines. Habitat characteristics such as monsoonal exposure (Matsumoto et al. 2020), relief (Benkendorff and Thomas 2007), and substrate types are indicated. Study areas Coordinates Monsoonal exposure Site description Aundanao 7° 5' 24" N, 125° 46' 58.08" E Northeast Medium relief; slope is steep relative to other study areas; sandy, coral rubble. The upper intertidal zone is a creviced rock wall descending into boulders, rocks, and sandy-coral debris substrate in the lower intertidal and shallow-water area. Balet 7° 9' 54" N, 125°