The giant barrel sponge Xestospongiatestudinaria is an ecologically important species that is widely distributed across the Indo-Pacific. Little is known, however, about the precise biogeographic distribution and the amount of morphological and genetic variation in this species. Here we provide the first detailed, fine-scaled (<200 km2) study of the morphological and genetic composition of X . testudinaria around Lembeh Island, Indonesia. Two mitochondrial (CO1 and ATP6 genes) and one nuclear (ATP synthase β intron) DNA markers were used to assess genetic variation. We identified four distinct morphotypes of X . testudinaria around Lembeh Island. These morphotypes were genetically differentiated with both mitochondrial and nuclear markers. Our results indicate that giant barrel sponges around Lembeh Island, which were all morphologically identified as X . testudinaria , consist of at least two different lineages that appear to be reproductively isolated. The first lineage is represented by individuals with a digitate surface area, CO1 haplotype C5, and is most abundant around the harbor area of Bitung city. The second lineage is represented by individuals with a predominantly smooth surface area, CO1 haplotype C1 and can be found all around Lembeh Island, though to a lesser extent around the harbor of Bitung city. Our findings of two additional unique genetic lineages suggests the presence of an even broader species complex possibly containing more than two reproductively isolated species. The existence of X . testudinaria as a species complex is a surprising result given the size, abundance and conspicuousness of the sponge.

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The Indonesian archipelago is a ‘hotspot’ for invertebrate biodiversity (‘Coral Triangle’). In this area of ‘peak’ biodiversity, the origins of this high species diversity have often been debated. Xestospongia testudinaria is one of the sponge species that dominates coral reef sponge communities in this region. The role of the so-called ‘giant barrel sponge’ for the reef ecosystem has been studied repeatedly, as have its various bioactive compounds. However, the genetic variation of this iconic sponge in the region remains unknown. We investigate over 200 barrel sponge samples from Indonesia, and neighbouring as well as more distant localities (Saudi Arabia, Tanzania, Thailand, Taiwan, Java, Sulawesi and the Great Barrier Reef, Australia) using the mitochondrial cytochrome oxidase subunit 1. We compare our results with those from the studies on the congeneric barrel sponges Xestospongia muta from the Caribbean, and Xestospongia bergquistia from the Indo-Pacific, and observe a high degree of overlapping haplotypes between the three barrel sponge species, likely indicating the presence of ancestral polymorphisms. We discuss the implications of these findings to better interpret the phylogeography of barrel sponge taxa in the Indo-Pacific.

Abstract. Muzaki FK, Setiawan E, Insany GFA, Dewi NK, Subagio IB. 2019. Community structure of Echinoderms in seagrass beds of Pacitan beaches, East Java, Indonesia. Biodiversitas 20: 1787-1793. In this study, we attempt to access diversity and community structure of Echinoderms on seagrass beds in each three belt transect (width 2 m, length 100 m) in Tawang and Pidakan beaches, Pacitan, East Java, Java. Observed parameters were species richness, composition, and abundance, as well as diversity indices: Shannon-Wiener's diversity index (H'), Simpson's dominance index (D) and Pielou's evenness index (J). At the end of the study, we identified one species of sea star (Asteroidea), seven species of brittle stars (Ophiuroidea), ten species of sea cucumbers (Holothuroidea) andnine species of sea urchins (Echinoidea). The most dominant species were Ophiocoma dentata (F. Ophiocomidae), Diadema setosum (F. Diadematiidae), Ophiomastix annulosa (F. Ophiocomidae) and Echinometra mathaei (F. Echinometridae). Value of H’ ranged from 0.538 to 1.252 in Tawang and 1.041 to 1.704 in Pidakan; which showing higher species richness and diversity in Pidakan. Echinoderm in the study area was not evenly distributed; D. setosum was very dominant in Tawang beach, while those three other species were more common in Pidakan. Furthermore, most of Holothuroid and Ophiuroid were found only in Pidakan which have relatively more complex habitat.

Sponge species are infamously difficult to identify for non-experts due to their high morphological plasticity and the paucity of informative morphological characters. The use of molecular techniques certainly helps with species identification, but unfortunately it requires prior reference sequences. Holotypes constitute the best reference material for species identification, however their usage in molecular systematics and taxonomy is scarce and frequently not even attempted, mostly due to their antiquity and preservation history. Here we provide case studies in which we demonstrate the importance of using holotype material to answer phylogenetic and taxonomic questions. We also demonstrate the possibility of sequencing DNA fragments out of century-old holotypes. Furthermore we propose the deposition of DNA sequences in conjunction with new species descriptions.

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Abstract. Setiawan E, Muzaki FK, Nurhayati APD, Maulidina N. 2019. Record of shallow-water sponges in Simeulue Island, Aceh Province, Indonesia. Biodiversitas 20: 3246-3257. The first and present study on shallow water sponges in Simeulue islands, Aceh Province, Indonesia recorded more than twenty species of marine sponges. This first assessment was also part of Ekpedisi Widya Nusantara X (E-WINN X) coastal chapter 2017 where was conducted in Simeulue islands, Aceh. Most of the recorded sponges are common species that are also recognized inhabiting a broad distribution in the West Indo-Pacific marine ecoregion. All recorded shallow-water sponges are Demospongian sponges. Among the three selected types of shallow water sponge habitats, a number of sponges are achieved mostly in shallow reefs in comparison to sandy and mangrove lagoons. The current study on species recorded also documents general characteristic enriches and highlights the importance of filling the gaps in distributional patterns of sponges on the west coast of Sumatra.

Abstract. Setiawan E, Chodiantoro MR, Insany GF, Subagio IB, Dewi NK, Muzaki FK. 2021. Short Communication: Diversity of sponges associated in seagrass meadows at coastal area of Pacitan District, East Java, Indonesia. Biodiversitas 22: 3105-3112. Sponges are sessile organisms and aquatic filter feeders that play an important role in marine ecosystems. They are also secondary metabolite compounds that exhibit promising novel properties. Indonesia has been categorized as a hot spot for sponge diversity. Despite this fact, some Indonesian coastal areas, especially in the southern area of East Java, have not yet been comprehensively explored to understand its diversity and potential value. For this reason, we investigated species richness of sponges associated with seagrass meadows in the southern coastal area of Pacitan District, in East Java. Seagrass meadows are important coastal areas that have been recognized as buffer zones for sustainable marine conservation because it provides safe shelter and acts as a nursery for many fishes and other invertebrates, including sponges. We identified 16 genera out of 12 families from two selected beaches in Pacitan. Boring sponges belonging to the Clionaidea family were dominant in those areas, covering more than 20 percent of the total recorded specimens. Moreover, conspicuous boring sponges in this study can be used for further environment alert since this group plays a vital role and negatively impacts destroying the calcium carbonate of marine organisms.