Possible occurrence of the sea cucumber Actinopyga spinea (Cherbonnier 1980) in Arreceffi Island, Honda Bay, Puerto Princesa City, Palawan, Philippines

Abstract

Sea cucumbers under the genus Actinopyga are among the commonly exploited species in the Philippines. At present, there are five species belonging to this genus in the country namely, A. echinites, A. lecanora, A. mauritiana, A. miliaris and A. obesa (Schoppe 2000, Akamine 2005, Kerr et al. 2006, Olavides et al. 2010, Purcell et al. 2012, Jontila et al. 2014). Recent surveys in different sites in Palawan did not show the occurrence of other Actinopyga species (Dolorosa and Jontila 2012, Collantes 2013, Pitong 2013, Sabay 2013, Saclet 2013, Dolorosa 2015). During the monthly monitoring of sea cucumbers in Arreceffi Island Resort and Spa on June 5, 2015, one individual of Actinopyga, suspected to be A. spinea was documented. The Island is located in Honda Bay (9°54’47.66″N, 118°52’35.64″E) about 16 km away from Sta. Lourdes Wharf, Puerto Princesa City (part of the mainland Palawan). It has approximately 20 ha land area, 30 ha mangrove forest and 170 ha intertidal and shallow subtidal areas, serving as safe habitats for diverse wildlife. Since its establishment in 1991, the island resort implemented no fishing or hunting activities that enabled the once overharvested species to recover. The substrate where the specimen was collected is mainly composed of sand and rubble, but patches of seagrasses (Cymodocea rotundata, Enhalus acoroides and Thalassia hemprechii) and stands of Rhizophora stylosa were also present in the area. The site is around 80 m away from the drop off and is exposed to moderate to strong wave action during high tide. The specimen was encountered during low tide in waters between 0.1 to 0.2 m deep. The specimen was first identified as A. miliaris due to its resemblance in external appearance and similarity in habitat with A. spinea (Figure 2). However, further examination of its external features based on the photos revealed that it is more likely to be A. spinea. Both species have brown to dark brown or blackish brown coloration, but A. miliaris has a lighter ventral part whereas A. spinea is entirely uniform in color. Similarly, the papillae of both species are long and slender but such are numerous on the dorsal of A. miliaris while it is only moderate in A. spinea (Figure 2) (Purcell et al. 2012). In addition, A. miliaris’ anal teeth are generally simple and conical in shape. In contrast, the specimen’s anal teeth are triangular with distinct nodules (Figure 3) that is a key feature of A. spinea (Conand 1998, Purcell et al. 2012). Actinopyga spinea is also similar in color with A. palauensis but the latter has textured dorsal surface with bumpy appearance, and the mouth is often projected as trunk-like (Purcell et al. 2012). Also, the papillae of A. palauensis on the dorsal are small and conical while they are long and slender in A. spinea. Furthermore, the anus of A. palauensis is more terminal while that of A. spinea is sub terminal. However, this feature of A. spinea was not noted when the specimen was collected. Further visual examination of the mouth position was also done on the specimen, which was collected and frozen for future studies, but such was difficult to determine for the sample has already collapsed after ejecting its internal organs during transport in 2015. Further search was made then in the area to look for other individuals of A. spinea but none was encountered. The specimen measured only 9 cm. This is far below the mean length of A. spinea that is 25 cm (Purcell et al. 2012). Thus, the individual could be in its juvenile or sub adult stage. However, this is difficult to ascertain due to lack of information on its growth and maturity (Purcell et al. 2012). Information on its distribution and population trend is also limited (Conand 1998). In fact, A. spinea is classified as a least concern species (Conand et al. 2013, IUCN 2016). Despite of the resemblance of A. spinea to A. miliaris and A. palauensis, the nodular anal teeth, the uniformly colored body, and the sparse conical papillae on the dorsal strongly suggest that the specimen is A. spinea. These characteristics were assumed to be sufficient for reasonable certitude but to complete the identification, ossicles examination is being undertaken for further examination of experts. If needed, DNA testing could also be done for the sample is kept viable for such procedure.