Journal of Sustainability Science and Management eISSN: 2672-7226 Volume 14 Number 4, August 2019: 25-37 © Penerbit UMT COMPARISON ON NATURAL DIETS DIETARY COMPOSITION AND FOREGUT FULLNESS BETWEEN SEXES OF CRENATE SWIMMING CRAB, Thalamita crenata (RÜPPELL, 1830) FROM SETIU WETLANDS, TERENGGANU COASTAL WATERS, MALAYSIA ADNAN AMIN-SAFWAN1, AZMAN NURAZIRA2, KHAIRUL SALLEH SYAFIQAH-NURAIN2, MOHD PAUZI MARDHIYYAH1, HARMAN MUHD-FAROUK1,3, HAIRUL HAFIZ MAHSOL1,4, MOHAMAD SYAHNON1 AND MHD IKHWANUDDIN*1 1Institute of Tropical Aquaculture and Fisheries Reseach, 2 Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, Kuala Nerus, Terengganu, Malaysia. 3Fisheries Research Institute Batu Maung, Department of Fisheries, Batu Maung, Pulau Pinang, Malaysia. 4Institute of Tropical Biology and Conservation, Universiti Malaysia Sabah, Kota Kinabalu, Malaysia. *Corresponding author: [email protected] Abstract: This study describes the natural diets of the crenate swimming crab, Thalamita crenata through observation on parameters for dietary composition between different sexes. A total of 30 pairs of T. crenata males and females were sampled from Setiu Wetlands, Terengganu, Malaysia. A significant difference ρ( < 0.001) was observed between body weight and the sex of T. crenata. Foregut fullness analysis revealed that males have a higher percentage of index score 4 than females (36.66% and 26.67%, respectively). A total of 12 different dietary items were identified in both sexes of T. crenata. Fish (male: 18.8%; female: 16.7%) and bivalve (male: 14.6%; female: 16.7%) were recorded as the most abundant in foregut content of both sexes of T. crenata. Gut content analysis reveals that T. crenata is a generalistic predator, cannibalistic and omnivorous as its diet is mainly composed of fishes, bivalves, slow-moving crustaceans and plants like seagrass and thus indicates their main food source. Overall, males possessed higher mean frequency of BW compared to females with 78.47 ± 17.66 g and 55.86 ± 14.48 g, respectively. No significant difference of food preferences was noted between the different genders and between the size of the crab (BW) with the mean fullness and dietary composition of T. crenata. This finding helps in understanding the dietary composition of different sexes ofT. crenata and thus can be a reference focusing on this species population dynamics and ecology study mainly for management purposes and artificial diet development for the near future. Keywords: Body weight, crenate swimming crab, dietary composition, foregut fullness, Thalamita crenata. Introduction 2011; Amin-Safwan et al., 2016) and other Crenate swimming crab, Thalamita crenata swimming crabs of the Indo-Pacific region also known as rocky spiny crab (Songrak et al., (Cannicci et al., 1996). T. crenata can be found 2009) is commonly found in mangrove creeks in South Africa, Madagascar, the Red Sea, the (Muhd-Farouk et al., 2017) and shallow waters Persian Gulf, India, China, Indonesia, Malaysia, of the Indo-Pacific region (Cannicci et al., Singapore, Korea, Japan, Australia, Tuamotu, 1996). These crabs inhabit the rocky and muddy Tonga, Hawaii and French Polynesia (Wee intertidal platform in front of the Sonneratia- & Ng, 1995). This species is fished mainly in fringe and swim in the swamps during their the Southeast and East Asian countries and are activity period (Vezzosi et al., 1995; Songrak frequently caught by trawlers, traps, seines and et al., 2009; Muhd-Farouk et al., 2017). Such nets. Collapsible traps are also widely used by behaviour was also observed in mud crab, genus fisherman for collecting mud crab, especially Scylla (Hill, 1979; Ikhwanuddin et al., 2010; in Malaysia (FAO, 2001). Although T. crenata Adnan Amin-Safwan et al. 26 is one of the most common and widespread and Mckillup (1996) have investigated on T. swimming crab species, little research has been crenata natural diets and feeding habits, while, done on this species or others within the genus Songrak et al. (2009) focused on fishery biology (Vezzosi et al., 1995), mainly due to lower of T. crenata. Susanto and Irnawati (2014) and market value as it is small in size compared to Muhd-Farouk et al. (2017) studied on size at the other commercial swimming crabs (Muhd- maturity and length-weight and width-weight Farouk et al., 2017). However, due to its flesh relationship, while Kannupandi et al. (1997) quality and more abundant compared to mud focused on water parameter (salinity) on crab (Muhd-Farouk et al., 2017), this species larvae and Sigana (2002) conducted a study is favoured by the local community as a source on breeding cycle of T. crenata. This species is of protein for their daily meals. As for their common in the Malaysian coastal waters, but landing, there is no data recorded previously, still there is scarce information, thus further thus proven that no in-depth study has been investigations are needed on natural diets of T. done on this species. crenata. Knowledge of natural diet in animal T. crenata can be classified as carnivorous species is generally essential to study to know and a predator. Its diet is mainly composed of their nutritional requirements, their interactions bivalves and slow-moving crustaceans (Cannicci with other organisms and their culture potential et al., 1996). Nonetheless, it also appears to be (Williams, 1981), besides for evaluation omnivorous as algae, seagrasses and other plant purposes and functioning of the ecosystems materials found in their stomachs (Cannicci et (Krebs, 1989). The knowledge gained can al., 1996). Moreover, cannibalism is common as support the expansion in terms of production the larger crabs feed on the young smaller crabs. and economy for this species in the near future. Though T. crenata is known to be a predator, Therefore, the investigation on natural diet on T. omnivorous and eats almost everything, the diet crenata is critical to understand the behaviour can still be influenced by the habitat that they and food preference between sexes of T. crenata, are living in, gender (sexes), maturity stage, which is important to develop successful seasons and their activity period (Sigana, 2002; aquaculture and farming techniques for this Hajisamae et al., 2015). Songrak et al. (2009) species (Ikhwanuddin et al., 2009). Besides, claimed that T. crenata activity period between the knowledge on the foregut fullness and the sexes were different, where males favoured dietary items found can be used as pioneer burrowing while females preferred swimming research towards in-depth understanding on this to search for their prey and both sexes were particular species. Therefore, the objectives of basically most active during the day (Chen et this study were to determine the natural diets al., 2005). of T. crenata through dietary composition and foregut fullness and to compare the body weight The present study on natural diets of T. and foregut fullness among different sexes of crenata focused on dietary composition and T. crenata from Setiu Wetlands, Terengganu foregut fullness. The data obtained can be Coastal Waters, Malaysia. helpful in understanding the feeding habits between sexes and also for fisheries management of T. crenata. The information on the foregut Materials and Methods fullness and dietary composition relationship Crab samples and sampling technique is important to understand the feeding habit T. crenata samples were from Setiu Wetlands, and nutritional requirement between male Terengganu, Malaysia and obtained at two and female T. crenata. Up to now, only a sampling stations: Sampling Station 1 (S1) and handful studies have been available that have Sampling Station 2 (S2) (Figure 1), from April focused on T. crenata , which were carried until June 2017 and the frequency for sampling out by Cannicci et al. (1996) and Mckillup J. Sustain. Sci. Manage. Volume 14 Number 4, August 2019: 25-37 NATURAL DIETS OF Thalamina crenata 27 Figure 1: The sampling stations at Setiu Wetlands, Terengganu, Malaysia (S1 = Sampling Station 1 (Latitude: 5.69º; Longitude: 102.72º) and S2 = Sampling Station 2 (Latitude: 5.65º; Longitude: 102.75º) was two days every week (Friday and Saturday). and differentiate the dietary items in the foregut Setiu Wetlands is located along the coast facing (Figure 2) using the crab collapsible traps. Crab the South China Sea in the state of Terengganu. collapsible trap is a traditional mud crab trap that It is located 60 km north of Kuala Terengganu. is simple but a very effective equipment which is Setiu Wetlands is one of the most important used to trap mud crabs (Poomikong et al., 2005). wetlands in Malaysia as it has mangrove areas No bait was used during sampling to avoid and salt marsh (Sigana, 2002) that are rich in bias in gut content analysis. Thirty collapsible biodiversity. traps were used during the biosampling of T. A total of 30 males and 30 females of the crenata. The collapsible traps were deployed in crab species T. crenata were sampled to identify the evening between 1600-1800 hours and left Figure 2: The dorsal (left) and ventral (right) view of T. crenata which was sampled from Setiu Wetlands, Terengganu, Malaysia J. Sustain. Sci. Manage. Volume 14 Number 4, August 2019: 25-37 Adnan Amin-Safwan et al. 28 overnight and collected early the next morning was handled in the most delicate way as the (0800-0900 hours). foregut is fragile and easily damaged. The The crabs captured in the collapsible traps fullness of the foregut was observed and were then immediately transferred and frozen recorded using the index of 1 to 4 (1 = 0-25% in an ice-chest (less than 1 hour) for physical foregut fullness, 2 = 25-50% foregut fullness, measurement. The crab body weights (BW) 3 = 50-75% foregut fullness and 4 = 75-100% and carapace width (CW) were measured of foregut fullness) (Ikhwanuddin et al., 2014) using an electronic balance (Shimadzu, Japan, (Figure 4). After the fullness index is completely identified, each foregut was fixed in formalin, in 0.001 g) and digital Vernier calliper (0.01 cm), TM respectively, according to the sexes of the crabs.