BIODIVERSITAS ISSN: 1412-033X Volume 21, Number 5, May 2020 E-ISSN: 2085-4722 Pages: 2233-2239 DOI: 10.13057/biodiv/d210552 Feeding selectivity of Holothuria atra in different microhabitat in Panjang Island, Jepara (Java, Indonesia) RETNO HARTATI 1,♥ , MUHAMMAD ZAINURI 2 , AMBARIYANTO AMBARIYANTO 1 , WIDIANINGSIH WIDIANINGSIH 1 1 Department of Marine Science, Faculty of Fisheries and Marine Science, Universitas Diponegoro. Jl. Prof. H. Soedarto, S.H., Tembalang, Semarang 50275, Central Java, Indonesia. Tel.: +62-24-7474698, Fax.: +62-24-7474698,  email: retnohartati.undip@yahoo.com 2 Department of Oceanography, Faculty of Fisheries and Marine Science, Universitas Diponegoro. Jl. Prof. H. Soedarto, S.H., Tembalang, Semarang 50275, Central Java, Indonesia Manuscript received: 17 March 2020. Revision accepted: 26 April 2020. Abstract. Hartati R, Zainuri M, Ambariyanto A, Widianingsih W. 2020. Feeding selectivity of Holothuria atra in different microhabitat in Panjang Island, Jepara (Java, Indonesia). Biodiversitas 21: 2233-2239. Particle selectivity by deposit feeder sea cucumber Holothuria atra was an important concept in its feeding ecology. This species utilized the organic matter that coated sediment and detrital particles as food. Thus, particle size, organic matter, and microalgal biomass had been proposed as variables food resources along which niche separation could occur in optimal foraging strategy. This study was conducted in five microhabitats of different coverage of seagrass bed (P1-P4) up to the rubble area (P5) over a tidally variable depth range of 0,5-5m in Panjang island, Jepara. Twenty samples of sea cucumber H. atra were taken from defined microhabitat, along with samples of sediment underneath the sea cucumber. Granulometry of the particles ingested by sea cucumbers, total organic matter, and microphytobenthic biomass (as chlorophyll-a) found throughout their digestive tract (alimentary canal) and in the sediments was analyzed. Comparison of the contents and the rates of organic matter assimilation of the digestive tract with those of the microhabitat sediment were carried out. The results showed that H. atra fed on sediment underneath their body and it was revealed that there were strong (ƿ=0.833-0.876) to very strong (ƿ=0.945) positive relationship between grain size in the sediment and in their alimentary canal which showed their feeding selectivity of the sediment. H. atra also found to have efficiency in feeding by taking advantage of the high TOM content and high abundance of microphytobenthic organisms (presented as chlorophyll-a) in their natural microhabitats. Keywords: Chlorophyll-a, organic matter, sea cucumber, sediment characteristic INTRODUCTION Holothuria atra was one the most common black Holothurian and the most frequently encountered sea cucumber in Indonesia (Setyastuti 2015), which was commonly known as lollyfish. These common shallow- water species were rarely found in depths of more than 20 m, and mostly on inner and outer reefs flats and back reefs or shallow coastal lagoons. It was abundant on sandy- muddy grounds with rubble or coral patches and in seagrass beds. Inshore shallow-water populations were denser, composed of smaller individuals, while in deeper or outer reef populations, the individuals were more scattered with larger individuals (Dissanayake and Stefansson 2012). This species was found in a variety of habitats over a broad range (Liu et al., 2013). In Panjang Island, Jepara, H. atra was found on the seabed, in shallow waters on reefs and sand flats and in seagrass meadows at depths of up to 10 meters (Hartati et al. 2019a,b). It also occupied pools of water from a few centimeters to about one-half meter deep at low tide, and was occasionally entirely exposed. It usually covered itself with a coating of light coral sand held in place by tube feet, although occasionally, it was naked and black. Naturally, the abundance of sea cucumber was very strongly affected by the availability of natural food in the habitat (Hartati et al. 2017). The complex and heterogeneous habitat could provide many diverse food sources for sea cucumbers. H. atra, just like H. arguinensis, might prefer a more complex habitat that had different microhabitats across small areas, which was able to support varied population density with different size individuals (Domínguez-Godino and González- Wangüemert 2020). Kashio et al. (2016) also stated that sea cucumber showed changing their microhabitat and activity level seasonally and when they found a suitable one, their feeding process continued. Holothuria atra was an omnivore, sifting through the sediment with its tentacles and feeding on detritus and other organic matter (Setyastuti 2014; Hartati et al. 2017). It ingested sand at the same time and digested the biofilm on the sand grains before ejecting them through its anus. Particle selectivity by deposit feeders, such as H. atra was an important concept in its feeding ecology. These species utilized the organic matter that coated sediment and detrital particles as food. Thus, particle size, organic matter, and microalgal biomass had been proposed as variables food resources along which niche separation could occur in optimal foraging strategy. Feeding activity and its relation with feeding selectivity had been discussed in deposit feeders such as H. sanctori (Navarro et al. 2013), Apostichopus japonicus (Sun et al. 2015) and H. scabra