Unravelling the moons: review of the genera Paratetilla and Cinachyrella in the Indo-Pacific (Demospongiae, Tetractinellida, Tetillidae)

Abstract Paratetillabacca (Selenka, 1867) and Cinachyrellaaustraliensis (Carter, 1886) occur in a broad range of marine environments and are allegedly widely distributed species in the Indo-Pacific. We coin the term ‘moon sponges’ for these species as they are spherical in shape with numerous porocalices resembling the lunar surface. Both species have a complex taxonomic history with high synonymization, in particular by Burton (1934, 1959). An examination of the junior synonyms proposed by Burton (1934, 1959) was conducted to establish the validity of the names. More than 230 specimens from Naturalis Biodiversity Center were reviewed that belong to the genera Paratetilla and Cinachyrella from marine lakes, coral reefs, and mangroves in Indonesia. The aim of the current study was to untangle the taxonomic history, describe the collection of moon sponges from Indonesia, and develop a key. We extensively reviewed the taxonomic literature as well as holotypes of most of the species synonymized by Burton. The taxonomic history of Paratetilla spp. and Cinachyrellaaustraliensis showed some cases of misinterpreted synonyms, misidentifications, and lack of detailed descriptions for some species. The conclusion of the revision is that there are three valid species of Paratetilla (P.arcifera, P.bacca, and P.corrugata) and four valid species of Cinachyrella (C.australiensis, C.porosa, C.paterifera, and C.schulzei) in Indonesia. This is furthermore corroborated by molecular work from previous studies. ParatetillaarciferaWilson 1925 and C.porosa (Lendenfeld, 1888) are resurrected. A full review of taxonomic history is provided as well as a key for identification of moon sponges from Indonesia. All species are sympatric and we expect that there are undescribed species remaining within the Tetillidae from the Indo-Pacific. Our current review provides the framework from which to describe new species in the genera Paratetilla and Cinachyrella from the Indo-Pacific.


Introduction
Moon sponges include two good examples of allegedly widely distributed species in the Indo-Pacific: Paratetilla bacca (Selenka, 1867) and Cinachyrella australiensis (Carter, 1886). They are conspicuous dwellers of a broad range of marine environments, including coral reefs, rocky shores, and coastal mangroves, as well as landlocked marine systems called marine lakes (e.g. Hooper et al. 2000, de Voogd and Cleary 2008, de Voogd et al. 2009, Becking et al. 2011. We use the term 'moon sponges' as these species are spherical in shape with numerous porocalices resembling the lunar surface and colored various shades of yellow, orange and brown. This common name has now been adopted by different authors (e.g., Szitenberg et al. 2013). Naturalis Biodiversity Center houses hundreds of moon sponges with a great diversity in morphology that were collected in Indonesia from 2006-2011 with the aim to survey the sponge biodiversity.
The genera Paratetilla and Cinachyrella, belong to the family Tetillidae, suborder Spirophorina, order Tetractinellida, class Demospongiae. As spirophorids, they are characterized by the presence of rugose sigmaspires . Similar to most tetillids, their globular shape is composed of triaenes and oxeas arranged in a radiate skeleton. Recent revisions of the order and the family have been compiled in the Systema Porifera by van  and van Soest and Rützler (2002), respectively. Although 26 nominal genera have been described, only ten valid genera are recognized, which are differentiated by the presence of cortical structures, specialized pore-sieves (porocalices) and composition of the complementary spicules (Rützler 1987, van Soest and Rützler 2002, Carella et al. 2016 (Table  1). The principal types of spicules of this family are: 1. Megascleres, oxeas and triaenes (pro-, plagio, ortho, and anatriaenes), and 2. Microscleres, microxeas and sigmaspires. Identification at species level is mainly based on the geometry and size range of all spicule types and presence/absence of triaenes (van Soest 1977, Rützler 1987, Rützler and Smith 1992, Lazoski et al. 1999, de Voogd and van Soest 2007, Carella et al. 2016).
The species P. bacca and C. australiensis share an obscure taxonomic history, including incomplete descriptions, intermingled identifications, and tens of different species synonymized (see synonyms of C. australiensis in Burton 1934: 523, andP. bacca in Burton 1959: 200). Therefore, we expected that a detailed revision would reveal species lumped together under both taxonomic entities. The aims of this paper are two-fold: (1) to review the taxonomic history of the genus Paratetilla and the species Cinachyrella australiensis, and (2) to identify and describe the different Paratetilla and Cinachyrella species from Indonesia in the Naturalis Biodiversity Center collection.

Taxonomic revision
Literature from 1867 to date was reviewed in order to compile the descriptions of the 11 nominal species for the genus Paratetilla Dendy, 1905. The Cinachyrella species revision was based on the literature cited by Burton (1934), who lumped together 16 nominal species as synonyms of Cinachyrella australiensis (Carter, 1886). The World Porifera Database WPD ) was used as a valuable guide for consulting the valid species and addressing the literature review. Type material and reference collections deposited at the American Natural History Museum (AMNH) in New York, at the Smithsonian Institution National Museum of Natural History (NMNH) in Washington D.C., the Natural History Museum (NHMUK, formerly BMNH) in London, and the Naturalis Biodiversity Center in Leiden (RMNH), were examined. The majority of the holotypes were studied for the current research; the ones we did not review were either unavailable or the description of the text was clear and comprehensive.

Sampling
Individuals of Cinachyrella spp. and Paratetilla spp. were collected by snorkelling and SCUBA diving during expeditions to Bali (2003), Bunaken (Sulawesi, 2006), Pulau Seribu (Java, 2005), Raja Ampat (Papua, 2007), Berau (East Kalimantan, 2008), and Ternate (Moluccas, 2009). Sampling was systematically achieved in marine habitats such as coral reefs and mangroves, and within marine lakes (Raja Ampat and Berau). Specimens were photographed in situ and notes made on morphological and ecological features such as color, size, depth, and substrate. A total of 237 specimens were collected and preserved in ethanol 70%; an additional 11 specimens from the Naturalis Biodiversity Center collection from Indonesia and elsewhere were reviewed as well as 20 type specimens. Table 2 provides an overview of sample numbers per species and Suppl. material 1 (Table S1) provides full collection details per sample.  Sollas, 1888 and principal characteristics used to distinguish them. (+) present, (-) absent. (AN) Antarctic, (AT) Atlantic, (CA) Caribbean, (IP) Indo-Pacific. Modified from Rützler (1987), van Soest and Rützler (2002), Carella et al. (2016). Number of valid species consulted at the World Porifera Database accessed 04 Jun 2018 Table 2. Number of samples reviewed per taxon. The column "Indonesia" refers to all samples recently collected in Indonesia (years 2006Indonesia (years -2011, "other material" to older specimens in museum collections from Indonesia or other countries; "types" refer to type specimens of valid species and junior synonyms.

Morphology
Radial and superficial histological sections of sponges were hand cut with a surgical blade; tissue sections were dried on a heat-plate more than 1 hour, mounted in Durcupan ACR resin and examined using light microscopy. Spicule preparations were made by dissociation of a fragment of sponge in sodium hypochlorite and consecutive washing steps, three times in distilled water, twice in 70% ethanol, and suspending in 95% ethanol. The dissociated spicules were dropped onto glass microscope slides, dried and mounted in Durcupan for light microscopy. Spicule preparations for Scanning Electron Microscopy (SEM) were made after two extra washing steps with 95% ethanol. Spicule dimensions and character definitions follow Rützler (1987), Rützler and Smith (1992) and van Soest and Rützler (2002). Spicule dimensions are based on 25 measurements for type specimens and for reference material. Data are given as minimum-mean-maximum in the text.
Recent checklists and biodiversity studies in the Indo-Pacific have only recorded P. bacca, following Burton's taxonomic decision in 1959 to synonymize all nominal Paratetilla species except P. lipotriaena. Two exceptions were found in the literature, the review by Desqueyroux-Faundez (1981) of Topsent's material (1897) from Amboina Island, who identified it as Paratetilla merguiensis, and the inventory of sponges from South China Sea by Hooper et al. (2000), where P. arcifera was listed in addition to P. bacca.  (Selenka, 1867), P. amboinensis (Kieschnick, 1898), P. cineriformis (Dendy, 1905) and P. eccentrica (Row, 1911). However, he also commented that P. bacca is a comprehensive variable species, as previously proposed by Thiele (1903) and later established by . Establishment of Cinachyrella genus. Validation of the genus Amphitethya Lendenfeld, . 1954 de Laubenfels Description of Paratetilla lipotriaena from Micronesia (West-Central Pacific), characterized by variable calthrop-like spicules and the absence of triaenes, and relatively similar to P. eccentrica Row, 1911Row, . 1959 Burton

van Soest and Rützler
Review of the eight genera included within family Tetillidae. Although Paratetilla characters were a combination of two descriptions, a paragraph in the discussion included the size differences between both Selenka's and Carter's material (Stelletta bacca and Tethya merguiensis, respectively). The origin of calthrop-like spicules was also discussed as probably modified plagiotriaenes resembling some Cinachyrella species, arguing the possibility of the inclusion of the widespread species Paratetilla bacca within Cinachyrella genus.

van Soest and Beglinger
Redescription of Paratetilla corrugata based on material from the Gulf of Oman, and giving validity to the variety P. bacca var. corrugata by   Fig. 25 a-e, a', b'. Tetilla bacca ;Lindgren, 1897: 485;Lindgren, 1898: 328;Thiele, 1900: 39, pl. ii, fig 13;Kirkpatrick, 1900: 132 (material seen); Lendenfeld, 1903: 19. Description. External morphology. Globular sponges, size between 1 and 5 cm in diameter. Surface hispid due to the projecting spicules, covered by numerous porocalices ( Figure 1A, B). Porocalices are bowl-shape, with oval to circular apertures, up to 5 mm in diameter and 7 mm deep, numerous, scattered uniformly over the surface of the sponge; in preserved material, some porocalices are closed and only a narrow aperture is visible giving to the sponge a rough appearance. External color generally brown when alive, which turns dark brown in ethanol, choanosome light brown, and has a 'dried out' appearance ( Figure 1B). Numerous small dark brown granules in the tissue ( Figure 1E, F). Consistency compact.
Skeleton. No cortex. Choanosomal skeleton composed by bundles of oxeas and triaenes radiating from a central core, ⅕-⅓ of the diameter of the sponge.
Megascleres. The material from Indonesia and the type of P. merguiensis have oxeas 850-3085.3-4500 mm × 5-41.5-65 mm (Table 4, Figure 1E, D, G). Anatriaenes always present, very abundant, cladi stout, slightly flattened, 20-62.6-100 mm × 12.5-48.3-75 mm, long rhabd up to 6000 × 20 mm, tapering to dimensions much less than 1mm ( Figure 1H, I). Protriaenes scarce in some specimens and absent in the type specimen; when present, they exhibit two different shapes, the first one with stouter and smaller cladi, the second one with thinner and larger cladi (27.5-53.9-100 mm × 37.5-107.4-200 mm × 2.5-6.5-12.5 mm), rhabd up to 5850 × 15 mm, tapering to dimensions of < 1 mm. Calthrop-like short shafted triaenes, three types are distinguished with a wide range of sizes, from which measurements are shown as a general summary (Table 4). In the first type, four rays can be recognized ( Figure 1L), three of them large, up to 400-600 mm, and a short one up to 100 mm long, usually pointing down to the centre of the body; the second one with three rays, almost the same length up to 400 mm; and the third one with three rays as well, two of them in an angle of 180° and the other one perpendicular, 50-100 mm. The calthrops are located immediately below the surface, constituting more or less a homogeneous layer.
Ecology. Inhabiting all studied environments in Indonesia, including coral reefs, mangroves, and marine lakes. Specimens more common in mangroves and marine lakes, and shallow reef flats where they are usually found on dead coral skeletons or coral rubble, typically ranging in depth from 0-5m. No specimens collected from deeper coral reefs in Indonesia.
Remarks. We did not succeed in locating the holotype of Paratetilla bacca, despite concerted effort. At this time, we assume that the type is no longer available. The description by Selenka of the type specimen does not mention the occurrence of any type of sigmaspires. It is a matter of speculation whether Lindgren (1897) actually examined Selenka's material to propose Carter's species Paratetilla merguensis as a junior synonym to Paratetilla bacca, or whether he based his conclusion merely on the literature. It is possible that sigmaspires may have been overlooked by Selenka in his original description and drawings, yet the arrangement of the megascleres in the skeleton shows a clear similarity with Carter's species P. merguensis (Suppl. material 2, Figure S1). In contrast to Selenka's description, Carter (1883) included a complete and detailed account of P. merguiensis, which was verified through examination of two slides deposited in the NHM collection (NHMUK 1894.11.16-17); few oxeas are complete in these slides (most broken), therefore limited variation of this character was observed. For most of spicule types enough measurements were possible. Although we did not succeed finding Selenka's type, we did examine one specimen and its associated slide preparation from Samoa identified as P. bacca (ZMA.POR.13029), which has all the characteristic spicules, including sigmaspires, that are present in our specimens from Indonesia . This material is designated here with the status of neotype following the rules of the International Code of Zoological Nomenclature, article 75. Therefore, we conclude that P. bacca is a valid species, and subsequent species should be designed as junior synonyms. In all of our Paratetilla samples, we have furthermore not encountered one specimen without sigmaspires. Here, we show the measurements of the holotype of P. merguiensis, as well as specimens from different localities in Indonesia (Table  4). Although there is a large variation in spicules sizes among the different localities, there was also great intra-specific variation and we did not find any reason to declare the validity of any junior synonym included in this revision. In general, populations from marine lakes (Kakaban and Haji Buang) exhibit smaller spicules in comparison with their reefal counterparts at the same localities (Table 4). This variation could be a response to different environmental conditions within the marine lakes (Becking et al. 2011), or a consequence of genetic selection after isolation of these populations about 8000-10000 years ago (Dawson and Hamner 2005, Becking et al. 2016, or a synergistic effect between environmental and genetic factors. According to the WPD (van Soest et al. 2018), other four valid Paratetilla species are P. amboinensis (Kieschnick, 1898), P. lipotriaena de Laubenfels, 1954, P. corrugata P. aruensis Hentschel, 1912. Based on the description of P. amboinensis (Kieschnick, 1898), the shape and skeleton features exhibited by this species fit within the current diagnosis of P. bacca, therefore we recommend that these two species should be synonymized. The species P. lipotriaena was erected by de Laubenfels based on the absence of triaenes. Our examination of the type specimen (USNM 23049) revealed the presence of triaenes and the same characters as P. bacca, therefore we have synonymized this species with P. bacca. On the other hand, P. bacca can be distingished from P. corrugata , because of the abundant trichodragmata exhibited by the latter species. Consequently, P. corrugata can still be considered a valid species. Finally, the status of P. aruensis Hentschel, 1912 within this genus should be reconsidered. After examination of two slides available at the NHMUK, no calthrops were found, only the typical amphitriaenes originally described for this species. Amphitriaenes make this species more similar to the genus Amphitethya instead of Paratetilla. Further examination of specimens would corroborate our preliminary conclusion.
In a molecular phylogenetic study, which was based in part on specimens that we review in the current study (see Suppl. material 1, Table S1 for corresponding Gen-Bank numbers), Schuster et al. (2017) distinguishes P. bacca as a monophyletic clade in the Tetillidae. Due to the wide distribution of this species and large intraspecific Table 4. Spicule measurements of six specimens of Paratetilla bacca and five specimens of P. arcifera from different regions (n = 10 per spicule type and dimension with minimum-mean-maximum). Asterisk (*) indicate that rhabds of spicules were broken and no measurement was possible.  12.5-14-17.5 7. 5-12.5-17.5 12.5-15.4-17.5 15-16.3-20 12.5-15.3-17.5 12.5-14-17.5 morphological variability we recommend further molecular studies, particularly of P. bacca from its type locality (American Samoa). This would allow a more detailed description of the genetic variation of P. bacca and verify our initial taxonomic proposal based on morphology. Wilson, 1925 Figs 3, 4, 5 Paratetilla arcifera Wilson, 1925: 380    Description. External morphology. Globular sponges, size from 3 to 6 cm in diameter (Figs 3A, 4A). Surface hispid due to the projecting spicules, covered by numerous porocalices. Porocalices are bowl-shape, with oval apertures, up to 10 × 5 mm and 6 mm deep, few, mainly on the top surface of the sponge; in preserved material, most porocalices remained open (Figs 3A, 4A). Color generally bright orange when alive, which turns darker or even brown in ethanol. No granules in choanosome. Fleshy consistency.

Paratetilla arcifera
Skeleton. No cortex. Skeleton composed by bundles of oxeas and triaenes radiating from a central core, and spaced between each other, giving a softer consistency (Figs 3C, D, 4C).
Ecology. Coral reef habitats at depths from 1-20/30 m. Absent from marine lakes, mangroves and other localities with higher sedimentation and/or variable salinity.
Distribution. Occur in coral reefs of Berau, Bunaken, Ternate, and Raja Ampat. An additional record from its type locality, Philippines (Wilson, 1925) could be inferred from the literature (see Longakit et al. 2005: Figure 9 as P. bacca), and collections from Taiwan ( Figure 5).
Remarks. Spicule sizes for most Indonesian specimens vary within the holotype ranges, except for the Ternate population, which exhibits smaller sizes and lack of protriaenes (Table 4). The typical orange color and 'fleshy' soft consistency are easy distinctive characters of this species ( Figure 4A). The differences between P. arcifera and its congener P. bacca lie in the stark orange coloring, the fleshy consistency, the lack of granules, the larger porocalices, and thin microxeas generally longer than in P. bacca. P. arcifera specimens are typically larger than P. bacca. We, furthermore, deem P. arcifera a distinct species from P. bacca, based on recent molecular phylogenetic analyses that included P. arcifera (genbank accession number LT628349) and P. bacca (LT628350) specimens reviewed in our current study and support the hypothesis of two species (Schuster et al. 2017).  (Lamarck, 1815) sensu Burton (1959). Originally, Wilson (1925) grouped certain species of the genera Tetilla and Cinachyra under the subgenus Cinachyrella based on the presence of porocalices (poriferous pits) and the absence of cortex. Subsequently, a complete review of Caribbean species by Rützler and Smith (1992) included four valid Cinachyrella species and it was recently complemented with the description of two new species from Brazilian deep waters (Fernández et al. 2018). The most recent review of the Indo-Pacific species was attempted by Burton (1934). In his monograph, Burton established that 16 nominal species were synonyms of the widespread and variable species Cinachyrella australiensis (Carter, 1886) (see Table 5). However, the validity of Burton's conclusion was not accepted by van Soest and Rützler (2002) in the Systema Porifera. Therefore, a further examination of the junior synonyms proposed by Burton (1934) was needed and became one of the principal aims that guide this revision. A general review of the historic events about species descriptions and synonyms is provided in Table 5. Emphasis was given to species described based on Indo-Pacific specimens. Remarks were added to clarify the early confusion introduced by Lindgren (1898) when he identified some Cinachyrella specimens as Tetilla ternatensis (=Paratetilla bacca), although his specimens have conspicuos acanthose microxea and lack of calthrop-like spicules, misleading later descriptions for both genera.
Cinachyrella australiensis has been recorded from a wide geographic area from the Gulf of Oman (van Soest and Beglinger 2008), Thailand (Kritsanapuntu et al. 2001ab, Putchakarn 2007, Vietnam (Azzini et al. 2007), Singapore (Lim et al. 2008), North Australia (McDonald et al. 2002), the Great Barrier Reef in Australia (Burton 1934), Southeast Australia (Carter, 1886), and Indonesia (e.g. Becking et al. 2006, de Voogd and Cleary 2008, de Voogd et al. 2009, inhabiting coastal mangroves, reefs, and marine lakes. Ecological studies on the morphological plasticity of C. australiensis from North Australia (McDonald et al. 2002) and Thailand (Kritsanapuntu et al. 2001) have concluded that this species can adapt to extreme sedimentation and water current regimes through the variation of the body shape and reinforcement of spicules. Although these surveys showed interesting data on the individual sizes, porocalices, silica/organic content, both of them lack robust taxonomic data (type of spicules and their dimensions). It is therefore unclear whether the observed plasticity can be attributed to natural variation within the same species or may possibly be explained by different species inhabiting different habitats.  (1891). Three other Tetilla species with "Vierstrahler" (= calthrops) spicules were described (see Table 3).

1900
Kieschnick Additional record of Tetilla schulzei from Ambon Islands, including description of the specimens, with microxea from 198 to 220 µm × 4 µm.

1900* Kirkpatrick
Extension of geographical range of T. bacca and T. ternatensis to Christmas Island. T. bacca specimens were described with identical spicules to Lindgren's material from Java. T. ternatensis also similar to Lindgren's material of T. ternatensis, this is having microxeas and missing calthrops.

Sollas
Description of Cinachyra malaccensis from Malaysia. Cup-shaped porocalices are described together with different spicules, except for microxea. In the available figures, no microxeas are shown.

1903* Lendenfeld
Designation of a new species Tetilla lindgreni based on T. ternatensis material described by Lindgren (1898) and Kirkpatrick (1900), excluding the original description of Kieschnick (1896), because the latter one has calthrop-like spicules. Two Spiretta species, S. raphidiophora and S. porosa, transferred to genus Tetilla.

Row
Description of Chrotella ibis from the Red Sea. Species with smooth microxea (150 × 2.1 µm), sharing this character with Tetilla poculifera, and Paratetilla species P. merguiensis, P. eccentrica and P. cineriformis. In his description, Row clearly differentiated his species from T. australiensis due to the latter having acanthose microxea.

Hentschel
Description of Cinachyra mertoni and Cinachyra nuda from Aru-and Kei-Islands (Indonesia). Both species contain microxea, the first one smooth 250 µm, whereas in the second one they are acanthose, from 200-280 µm, and no anatriaenes were found. A third species, Tethya clavigera, with oscula (similar to porocalices) and no microxea was also described.

Dendy
Description of Cinachyra vaccinata and C. providentiae from the Indian Ocean. Both of them with microxea (no mention whether acanthose or not), being 200 × 4 µm in the former, and 220 × 5.5 µm in the latter one. C. vaccinata characterized by small hair-like protri-and prodiaenes, terminating in an elongated oval swelling tip unique to this species. C. providentiae with bottle-shaped porocalices.

Burton
Taxonomic revision of Cinachyra australiensis. In his compilation, Burton grouped 16 nominal species described in 32 references and designated them as junior synonyms of the widespread species C. australiensis. Three different groups were recognized: the australiensisgroup characterized by the presence of acanthose microxea; the schulzei-group with smooth microxea; and the porosa-group without microxea. Description of genus Raphidotethya.
Skeleton. No cortex. Skeleton composed by bundles of oxeas and triaenes radiating from a central core.
Megascleres. Holotype and Indonesian specimens' measurements are shown in Table 6. Holotype, oxeas 3375-4135.5-5500 mm × 15-24.7-37.5 mm ( Figure 6D, K); no triaenes were observed in the type specimen; in Carter's description, protriaenes are described (135 mm long) and the absence of anatriaenes was explained as their heads  four specimens of C. paterifera from different regions (n = 10 per spicule type and dimension with minimum-mean-maximum). Asterisk (*) indicate that rhabd of spicules were broken and no measurement was possible.
Ecology. Cinachyrella australiensis occurs in reefs, mangroves, and marine lakes, ranging in depths from 0 to at least 30 m, possibly deeper. Specimens can be covered by sand and mud; or in symbiosis with algae, resulting in green external color. This species produces 1-2 mm sized buds ( Figure 8) and buds are extensively observed in specimens collected from marine lake habitats.
Remarks. In the type description of C. australiensis Carter (1886), the author did not observe anatriaenes as it can be interpreted from his statement: "I saw no anchors (smaller tetractinellids with recurved arms); but as their heads when exposed are generally broken off (for they catch in everything that they touch), it does not follow that they do not form part of the spiculation, particularly as they are present in most of the other species that I have been described (sic)". We examined the holotype kept at the Natural History Museum (NHMUK 1886.12.15.367) and found neither anatriaenes nor protriaenes. In addition, most of the oxeas were broken in the type specimen. Within all the examined material there is a high variability in the presence or absence of triaenes without a distinct geographic pattern. This variation may be related to where the sponge was cut, as it seems that triaenes are particularly abundant around the porocalices compared to other parts of the sponge. These fragile spicules are also easily broken off. We still assign our specimens to the species C. australiensis due to the characteristic presence of acanthose microscleres. It is furthermore one of the most common names used in the literature since its description and without further evidence we do not want to cause more confusion. Further examination of Cinachyrella specimens from Australia, in particular from the type locality of C. australiensis, will shed more light in this situation. It is quite possible that after a review of specimens from Southern Australia, it will be evident that the Indonesian specimens that we assign to C. australiensis should in fact be assigned to another species. In that case one of the junior synonyms should be used, e.g. C. raphidiophora or C. hirsuta.
Although our focus was on Indonesian species, it was unavoidable to attempt, for the first time after Burton's review (1934), check the status of his large list of junior synonyms, because some of them were described or later found in Indonesian localities. We gathered as many type specimens as possible, most of them repositories of the NHMUK (London) and NMNH (Washington DC). The main criteria we used to suggest a species as junior synonym of C. australiensis were the presence of acanthose microxea and that the mega-and micro-scleres have the same size range of the species. Therefore, here we include as junior synonyms the following species from Burton's list: Spiretta raphidiophora Lendenfeld, 1888;Tetilla hirsuta Dendy, 1889;Cinachyra isis Lenfenfeld, 1907;Tetilla cinachyroides Hentschel, 1911;Cinachyra nuda Hentschel, 1912;Cinachyra vaccinata Dendy, 1922; Cinachyra providentiae . They all fulfill the C. australiensis description.
Here we provide further remarks on the following species, in chronologic order: Tetilla lindgreni  was described as a new species to separate it from T. ternatensis Kieschnick, 1896, as T. ternatensisis is a Paratetilla based on the presence of calthrop-like spicules. Lendenfeld noticed that both, Lindgren's (1898) and subsequently Kirkpatrick's (1900) material, lack such calthrop-like spicules, and instead, they have acanthose microxea similar to other Tetilla specimens described in his monograph . From that material, we checked Kirkpatrick's specimens and suggest that T. lindgreni is a junior synonym of C. australiensis.
Tethya hebes  has acanthose microxea and it has most of C. australiensis characters, yet it was excluded from Lendenfeld's Cinachyrinae-group (with porocalices) because he did not observe porocalices. The type specimens of T. hebes examined at the NHM (NHMUK 1908.9.24.66) are two small fragments, about 1.2 × 1 cm, and it is not possible to observe neither discard the presence of porocalices. Apart from that, the general skeletal arrangement and spicule configuration suggest that T. hebes fulfil all other morphological characteristics of C. australiensis. Therefore, we suggest that T. hebes is a junior synonym of C. australiensis.
We exclude from C. australiensis some junior synonyms that are part of the schulzeigroup species proposed by Burton (1934). These species have smooth microxea and include Keller's (1891) species from the Red Sea, Cinachyra schulzei and Cinachyra trochiformis. The taxonomic case of C. schulzei becomes more complicated as Kieschnick (1898Kieschnick ( , 1900) described a new species named Tetilla schulzei from material collected in Amboine islands of Indonesia with porocalices and spicules diagnostic of Cinachyrella, including microxea. However, Kieschnick did not mention any observation whether or not the microxea of T. schulzei have acanthose surface. The set of characters of Cinachyra schulzei Keller, 1891 and Tetilla schulzei Kieschnick, 1898 correspond to Cinachyrella. However, we consider that both species should be treated as homonyms because they were described under two different genera, from different and distant localities and we were not able to find their type material to verify if they could be synonymized. Other species within the schulzei-group are Cinachyra mertoni Hentschel, 1912 from Kei island in Indonesia; Tetilla poculifera Dendy, 1905 from Sri Lanka;and Chrotella ibis Row, 1911 from the Red Sea. Special attention and a further revision is proposed for the schulzei-group of species, as we did not observe any specimen of the genus Cinachyrella with smooth microxea within the Indonesian material examined in this study. It is important to mention that thin smooth microxea were observed in both Paratetilla species, P. bacca and P. arcifera, but they also have calthrops as a diagnostic character of the genus.
We also exclude from C. australiensis two of the junior synonyms still present in the WPD . First, Tethya armata Baer, 1906, because it is clear from the description that this species has a proteinous cortex reinforced by microxeas, resembling other Craniella species. Second, we exclude the junior synonym Cinachyra malaccensis Sollas, 1902, as the description does not mention the presence of microxea, therefore we suggest to synonymise it with C. porosa. In our view, the recently erected species of Cinachyrella anatriaenilla is junior synonym of C. australiensis, because the oxea and the microscleres fall within the size range of the type species of C. australiensis as well as the specimens we have included in this review. The authors distinguish their species from C. australiensis on the basis of having only one category of oxeas versus two categories in C. anatriaenilla. However, we do not recognize size classes in oxea in any of the Cinachyrella specimens and types, but rather a continuos range in size (1000-5500 mm for C. australiensis). The oxea of C. anatriaenilla fall within the size range of the type specimen of C. australiensis as well as the other reviewed material of C. australiensis. In addition, the authors based their statements on the revision of the type specimen of C. kuekenthali, which is from the west Atlantic, but they did not review the type specimen of C. australiensis nor any of the other species with acanthose microxea from the Indo-Pacific.
Recent molecular studies (Szitenberg et al. 2013, Schuster et al. 2017 show that Cinachyrella is a polyphyletic genus. It is beyond the scope of the current study to review the taxonomic status of the genus Cinachyrella. Within C. australiensis there are different genotypes (Schuster et al. 2017) that possibly represent morphologically cryptic species. Among the high morphological variation observed within our Indonesian specimens, some trends could be highlighted among the different populations. For instance, specimens from reefs of Berau were generally larger (up to 8 cm in diameter) and their porocalices had a bottle-shape with a small aperture (1 to 4 mm) and the cavity was often occupied by a shrimp. Although these characteristics resemble C. providentiae, the latter is one of the junior synonyms that we propose for C. australiensis based on spicule dimensions and forms. Specimens from Raja Ampat generally had smaller acanthose microxeas (Table 6), while in some specimens collected in marine lakes few abnormal spicules were observed. Yet, in all cases we could not detect consistent, quantifiable morphological differences.  Color generally yellow when alive ( Figure 10A, B), which turns paler or even white-grey after preservation in ethanol ( Figure 9A).
Skeleton. No cortex. Skeleton composed by bundles of oxeas and triaenes radiating from a central core (Figs 9C, 10C).
Ecology. Occurs in reefs, mangroves, and marine lakes. Predominantly in shallow areas. Notably, a large population inhabit the marine lake of Tanah Bambam, where C. porosa was the dominant representative of moon sponges. This species produces 1-2 mm sized buds ( Figure 8) and buds extensively in marine lakes habitats.
Distribution. According to the material examined in this revision, we observed that this species is widely distributed in the Indo-Pacific, from the Chagos archipelago, Sri Lanka, Australia, and Tonga Islands. In Indonesia, C. porosa has been collected in East Kalimantan, Java, Ternate, and West Papua.
Remarks. Cinachyrella porosa is distinguished from C. australiensis by the absence of acanthose microxea and smaller size of sigmaspires. The first species described with these two diagnostic characteristics was Spiretta porosa Lendenfeld, 1888, subsequently transferred to the genus Tetilla ) and included as a junior synonym of C. australiensis in both, Burton (1934) and WPD (2018). The detailed examination of the holotype of C. porosa suggests that this species should therefore be resurrected. Based on the careful examination of the holotypes of C. albabidens  and C. albaobtusa , and the descriptions and plates of C. malaccensis (Sollas, 1902) and C. clavigera (Hentschel, 1912), we coincide with the porosagroup recognized by Burton (1934). However, we disagree with the statement that intermediate forms can be found within the wide range of variation of C. australiensis, and therefore we consider C. porosa as a valid species clearly differentiated from C. australiensis.  recognized the difficulties to separate the three species of the alba-group, and his decision to discriminate them as different species was based on distant localities and slight differences on the abundance of triaenes. After the morphological analysis of the C. albatridens holotype, we consider that this species could also be a junior synonym of C. porosa because neither microxea nor other characters to separate this species were found. Although Burton (1934) did not consider C. anomala (Dendy, 1905) within the porosa-group, we suggest that a similar decision could be  Lendenfeld, 1907, Anachoreten (=Keniet) Islands, Papua New Guinea 5 Cinachyra albabidens , Tonga Islands 6 Tethya clavigera Hentschel, 1912, Aru Island, Indonesia. made based on our observations of the type specimen. Some of the Indonesian specimens have silica micro-spherules. Similar spherules have been described for species C. anomala and C. hirsuta (Dendy, 1905), as well as Tetilla cinachyroides (Hentschel 1911). Because C. hirsuta and T. cinachyroides contain acanthose microxea, they are synonimized with C. australiensis. The nature of these spherules has been discussed by Dendy (1905) and . Dendy (1905) suggests that the spherules are associated with mother cells, which probably would give origin to sigmaspires, or they can be considered as anomalous or incidental spicules. On the other hand,  estimated that spherules are the earlier stages of oxeas as described for Tethya cranium (see Lendenfeld 1907, plate 14 figs 11-15). Silica spherules are very variable within populations of the same species and among different genera in Tetillidae, suggesting that this character has no taxonomic value.
Cinachyrella paterifera (Wilson, 1925 Description. External morphology. Globular sponges, size from 5 to 7 cm in diameter attached to the substrate by a large peduncle/shaft 3 × 2.5 cm (Figure 12 A,  B). Surface smooth to hispid due to the projecting spicules, covered by porocalices. Porocalices are bowl or pocket-shape, with rounded apertures, up to 5 × 7 mm and 2-4 mm deep; a central cloaca is located on the top, 15 × 12 mm in diameter and 10 mm deep. Color bright pink when alive, which turns slightly paler in ethanol. Skeleton composed by bundles of oxeas and triaenes radiating from a central core. No cortex.
Ecology. The species occurs mainly in reefs, and it is rare in marine lakes and mangroves. It usually inhabits sand bottoms, in which the penduncle serves as a support structure.
Distribution. Indonesia, including East Kalimantan and West Papua. It is also known from Sibutu Island in Philippines (Wilson 1925). Although it is found in a variety of habitats, C. paterifera is the least common species of Cinachyrella from Indonesia.
Remarks. Cinachyrella paterifera has a characteristic elongated peduncle, it is pink to violet colored, and it contains abnormal anatriaenes. Interestingly, Wilson (1925) described rare microxeas (250 × 2 µm) in one specimen of the type series, whilst they were very abundant in the other two types. After a detailed examination of the type specimen USNM 21314 and preparations from different parts of the individual sponge, no microxeas were observed, suggesting that this character is not diagnostic of the species. Although C. tenuiviolacea (Pulitzer-Finali 1982) from the Great Barrier Reef resembles C. paterifera in the distinctive pink to violet color and presence of abnormal anatriaenes, it remains to be investigated if these two species could be synonymized. We could not access type material from C. tenuiviolacea, and from the bad conditions of preservation noted by Pulitzer-Finali (1982) in his type specimen, it is not possible to determine whether the specimen has or does not have the peduncle characteristic of C. paterifera. The large numbers of hair-like protri-and prodiaenes around the porocalices of C. paterifera, resemble those described for C. vaccinata (Dendy, 1905), yet the C. vaccinata type contains acanthose microxea characteristic of C. australiensis. Cinachyrella paterifera share with C. porosa the absence of microxea, but they differ by the larger sigmaspires and abnormal protriaenes of C. paterifera. Indonesian specimens vary within the morphological range of the species. Specimens of this species belong to the same phylogenetic clade supporting its monophyly (Szitenberg et al. 2013;Schuster et al. 2017).

Final remarks
Our results contribute to the understanding of the taxonomy and systematics of the Indo-Pacific tetillids. A review of the taxonomic history of the genus Paratetilla and the species Cinachyrella australiensis, showed some cases of misinterpreted synonyms, misidentifications and lack of detailed descriptions for some species. The concept of a single widespread species is refuted for Paratetilla bacca , Burton 1959 as well as for Cinachyrella australiensis (Burton 1934). A wide morphological variation within moon sponges was observed for specimens collected in Indonesia. Among our material, we recognize three Paratetilla and four Cinachyrella species occurring in Indonesia, inhabiting a variety of habitats such as marine lakes, coral reefs, and mangroves. We are resurrecting P. arcifera Wilson 1925 andC. porosa (Lendenfeld, 1888) as valid species. The majority of the holotypes were studied for the current study; the ones we did not review were either unavailable or the description of the text was clear and comprehensive. The species of Paratetilla and Cinachyrella are clearly highly adaptable and widely distributed sponges. All species in the current study are distributed across Indonesia. It is remarkable that they are all sympatric, some species occuring together in the same marine lake. We have reviewed specimens from East Kalimantan, North Sulawesi, and West Papua. It is highly likely that there are more species in Indonesia in regions that have not been sampled as extensively. Further investigations into Paratetilla and Cinachyrella from the Molluccas, Nusa Tenggara, South Kalimantan, Eastern Papua, and also the virtually unexplored deep sea of Indonesia, will likely lead to the discovery of more species within these genera. Most species occur in all studied habitats (marine lakes, mangroves, and reefs) with a high degree of tolerance for high temperature and sedimentation, as has been observed in other families of sponges (Schönberg 2015). The exceptions to this high tolerance were P. arcifera and C. paterifera, which were only seen in reefs with little sedimentation or sediment resuspension. High budding was observed in specimens of Cinachyrella australiensis and C. porosa residing in marine lakes, while no budding was observed in the same species in the reefs. Singh and Thakur (2015) revealed temperature as the most prominent factor regulating the intensity of budding in Cinachyrella cf. cavernosa.
Previous molecular phylogenetic studies indicate that P. bacca, P. arcifera, C. porosa, and C. paterifera are distinct monophyletic species, while Cinachyrella australiensis may consist of a species complex with morphologically cryptic species (Schuster et al. 2017). In the specimens that we identify as C. australiensis we do not find any consistent differences in spiculation to validate distinct species, in spite of the different haplotypes that are found within our specimens. Carella et al. (2016) also found that several well-supported subgroups within the Cinachyrella clade might correspond to subgenera. We were not able to distinguish multiple species with our set of C. australiensis specimens using standard morphological characters. Among the reviewed literature, we also observed that there is a tendency among people making inventories of reef species to name any yellow or yellow-orange tetillid ball C. australiensis. It is clear that the genus Cinachyrella and in particular the species C. australiensis require further analysis using either other molecular markers or morphological characters that go beyond the aims of the current study. We hope that our detailed study, images, and key will ensure that species from Paratetilla and Cinachyrella will be identified correctly based on morphological characters. It is important to understand the distinction between species, as there is a growing interest in natural products and other biobased studies from tetillids (e.g. Cleary et al. 2013, Mokhlesi et al. 2017, Zhang et al. 2017. We expect that the current study can provide a solid basis for subsequent species descriptions of Indo-Pacific species of the genera Cinachyrella and Paratetilla. Fund, the Leiden University Fund (LUF)/Slingelands, Singapore Airlines, the AM Buitendijk Fund and the JJ ter Pelkwijk Fund. Examination of type specimens was possible thanks to EDIT Fellowships for Women Scientists to NS at the NHM and to LB at the NMNH. We are grateful to the Indonesian Institute of Sciences (LIPI) and the Indonesian State Ministry of Research and Technology (RISTEK) for providing research permits in Indonesia.