The diversity of relationships between Antarctic sponges and diatoms: the case of Mycale acerata Kirkpatrick, 1907 (Porifera,Demospongiae)

The diatom assemblage associated with the Antarctic sponge Mycale acerata was studied through an analysis of the diatom frustule and pigment concentrations in both the sponge ectosome and choanosome. Sponges were sampled weekly from November 2001 to February 2002 at Terra Nova Bay, Antarctica, at a depth of 25–35 m. The most abundant diatoms were Porannulus contentus, Fragilariopsis curta, Thalassiosira cf. gracilis, T. perpusilla and Plagiotropis sp. High abundances of P. contentus were found on the sponge ectosome up to the beginning of November, before the ice melted, while later frustules were incorporated inside, indicating that P. contentus lives epibiontically on M. acerata and represents a potential food source for the sponge. The presence of other diatom species was mainly related to the summer phytoplankton bloom. The sponge incorporates diatoms from the water column and utilises them as a food source, accumulating frustules inside the choanosome. The lack of planktonic diatom frustules at the beginning of the summer indicates that they are expelled or dissolved during the cold season.     

Florida reef sponges harbor coral disease-associated microbes

Sponges can filter large volumes of seawater and accumulate highly diverse and abundant microbial communities within their tissue. Culture-independent techniques such as fluorescent in situ hybridization (FISH), 16S small subunit (SSU) rRNA gene analyses, and transmission electron microscopy (TEM) were applied to characterize the presence and distribution of microbes within sponges abundant on south Florida reefs. This study found that coral disease-associated bacteria (CDAB) are harbored within Agelas tubulata and Amphimedon compressa. FISH probes detected several potential bacterial pathogens such as Aurantimonas coralicida, Cytophaga sp., Desulfovibrio spp, Serratia marcescans, and Vibrio mediterranei within A. compressa and A. tubulata host sponges. Spatial differences in the distribution of targeted bacteria were seen within sponge hosts. Transmission electron microscopy of A. compressa indicated there was a higher concentration of bacteria in the choanosome compared to the ectosome. These observed spatial distributions support the presence of internal sponge niches, which could play a role in the location of the CDAB within the sponges.     

Non-rigid cryptic sponges in oyster patch reefs (Lower Kimmeridgian, Langenberg/Oker, Germany)

Summary Two patch reefs which predominately consist of the oysterNanogyra nana (Sowerby 1822) are exposed in Lower Kimmeridigian strata of the Langenberg hillrange, central Germany. Left oyster valves making up the frame-work of the reefs formed small abundant cavities that were inhabited by a unique sponge community. The excellent preservation of non-rigid sponges was related to early organomineralization within the decaying sponge tissue. As a process of sponge taphonomy, different types of microbially induced carbonates precipitated preserving spicule aggregates. Organomineralization within sponge soft tissues is especially favored with the Langenberg patch reefs due to the closed or semi-closed system conditions with the cavities. The δ¹³C values ofin situ formed microbialities reveal that carbonate precipitation was in equilibrium with Jurassic seawater. The carbon of the microbialites does not derive from the bacterial remineralization of organic matter, but is of a marine source. Likewise, organomineralization is probably related to bacterial EPS or decaying sponge tissues providing an organic matrix for initial carbonate precipitation. Biomarker analyses revealed, that the patch reef microbialites contain terminally branched fatty acids (iso-andanteiso-pentadecanoic acid) in significant concentrations. These fatty acids, like hopanoid hydrocarbons, are most likely of a bacterial source. This is in agreement with sulfate-reducing bacteria remineralizing the decaying sponges as further indicated by the occurrence of framboidal pyrite in sponge microbialites.     

Evidence for spicule homology in calcareous and siliceous sponges: biminerallic spicules in Lenica sp. from the Early Cambrian of South China

Botting, J.P., Muir, L.A., Xiao, S., Li, X. & Lin, J.‐P. 2012: Evidence for spicule homology in calcareous and siliceous sponges: biminerallic spicules in Lenica sp. from the Early Cambrian of South China. Lethaia, Vol. 45, pp. 463–475. The relationships of the extant sponge classes, and the nature of the last common ancestor of all sponges, are currently unclear. Early sponges preserved in the fossil record differ greatly from extant taxa, and therefore information from the fossil record is critical for testing hypotheses of sponge phylogenetic relationships that are based on modern taxa. New specimens of the enigmatic sponge Lenica sp., from the Early Cambrian Hetang Biota of South China, exhibit an unusual spicule structure. Each spicule consists of a siliceous core with an axial canal, an organic outer layer and a middle layer interpreted to have been originally calcium carbonate. This finding confirms previous work suggesting the existence of biminerallic spicules in early sponges. Combined with data from other early sponges, the new findings imply that the two fundamental spicule structures of modern sponges were derived from a compound, biminerallic precursor. Spicules are therefore homologous structures in Calcarea and Silicea, and if sponges are paraphyletic with respect to Eumetazoa, then spicules may also have been a primitive feature of Metazoa. □Calcarea, Early Cambrian, Hetang Biota, phylogeny, Silicea, taphonomy.     

Can a sponge feeder be a herbivore? Tylodina perversa (Gastropoda) feeding on Aplysina aerophoba (Demospongiae)

Feeding biology in mollusks has important biological, ecological and evolutionary implications because many of the characteristics we observe in mollusks arise from their co-evolution with diet organisms. We investigated the relationship between the opisthobranch Tylodina perversa and the sponges Aplysina aerophoba and Aplysina cavernicola in order to ascertain the trophic interactions between them. The opisthobranch preferred specimens of Aplysina aerophoba inhabiting shallow overdeep waters, ectosome of Aplysina aerophoba over choanosome, and showed no preference for Aplysina cavernicola . The sponge Aplysina cavernicola lacks the cyanobacteria abundant in the ectosome of Aplysina aerophoba . Our study shows that the opisthobranch Tylodina perversa actively selects for sponges or sponge zones with high concentration of cyanobacteria, i.e. only a fraction of the ingested material is of animal origin. Addition of cyanobacteria to symbiont-free sponge material induced a shift in mollusk preference. Our results cast doubt over the widely recognized qualification of Tylodina perversa as a carnivorous sponge feeder and show evidence that cyanobacteria determine the opisthobranch food selection. Whether this is an isolated example of how symbionts may determine trophic interactions between hosts and predators or it is widespread in benthic organisms remains an open question that requires further investigation.  © 2003 The Linnean Society of London . Biological Journal of the Linnean Society , 2003, 78 , 429–438.     

Plectroninia celtica n. sp. (Calcarea, Minchinellidae), a new species of “pharetronid” sponge from bathyal depths in the northern Porcupine Seabight, NE Atlantic

Recent pharetronid sponges were regarded as relict species in tropical and subtropical waters, inhabiting cryptic habitats on coral reefs and in caves. More recent findings of a new species of the genus Plectroninia off northern Norway, with an inner fused skeleton have changed that view. Recent investigations on the sponge fauna of the “Propeller Mound”, northern Porcupine Seabight, focusing on sponges growing on the azooxanthellate cold-water coral Lophelia pertusa (Linné 1758) and Madrepora oculata Linné 1758, established the presence of a species of Plectroninia new to science. Its status as a common species within this deep-water coral habitat and the general status of the genus Plectroninia are discussed.     

Allocation of chemical and structural defenses in the sponge Melophlus sarasinorum

Sponges have evolved a variety of chemical and structural defense mechanisms to avoid predation. While chemical defense is well established in sponges, studies on structural defense are rare and with ambiguous results. We used field and laboratory experiments to investigate predation patterns and the anti-predatory defense mechanisms of the sponge Melophlus sarasinorum, a common inhabitant of Indo-pacific coral reefs. Specifically, we aimed to investigate whether M. sarasinorum is chemically or structurally defended against predation and if the defenses are expressed differently in the ectosomal and choanosomal tissue of the sponge. Chemical defense was measured as feeding deterrence, structural defense as feeding deterrence and toughness. Our results demonstrated that chemical defense is evenly distributed throughout the sponge and works in conjunction with a structurally defended ectosome to further reduce predation levels. The choanosome of the sponge contained higher protein levels, but revealed no structural defense. We conclude that the equal distribution of chemical defenses throughout M. sarasinorum is in accordance with Optimal Defense Theory (ODT) in regards to fish predation, while structural defense supports ODT by being restricted to the surface layer which experiences the highest predation risks from mesograzers.     

Reconstruction of the unusual late Cretaceous hexactinellid spongeAphrocallistes alveolites (Roemer, 1841)

The hexactinellid spongeAphrocallistes alveolites (Roemer, 1841) from Campanian calcareous to marly rocks of the Hannover area is redescribed. Based on well preserved larger fragments of the sponge body, its generai growth-form is reconstructed. It is shown that this species consists of stolon-like, ramified branches running parallel to the sediment-water interface. Initially, they scatter in all directions in a star-like manner, with presumably four to five branches giving the sponge body an almost radially spreading shape. Structures for anchoring, e. g., root-like appendices, are not developed. The branches are interspersed by bowl-like offspings with an osculum covered by a diaphragm at their distal ends. Thus, mature specimens resemble a rambling “chandelier“. This external morphology represents a special “bauplan“ of sponges that was heretofore unknown. Morphologically,A. alveolites shows adaptations both to soft-bottom sediments and calm, non-disturbed (neritic) offshore shelf environments. Specimens attained a stable position by building an extended skeleton of stellate branches resting laterally on the soft-bottom sediment or are partly burried in the sediment (snowshoe strategy). Functional morphological analysis indicates that the mode of interposition and spatial distribution of oscula within branches ensure the nutrition ofA. alveolites in a calm environment.      

Growth and Survival of Early Juveniles of the Marine Sponge Hymeniacidon perlevis (Demospongiae) Under Controlled Conditions

To resolve “the supply problem” in sponge-derived drug development and other biotechnological applications, current research is exploring the possibility of obtaining an alternative sustainable supply of sponge biomass through intensive aquaculture of sponges utilizing artificial seed rearing. This study aimed to investigate the technology of early juvenile sponge cultivation under controlled conditions. The effects of food, temperature, water flow, and light on the growth and survival of early juveniles of the marine sponge Hymeniacidon perlevis were examined. The concentrations of four types of food elements [microalgae (Isochrysis galbana), photosynthetic bacteria (Rhodopseudomonas), Fe³⁺ (FeCl₃), and Si (Na₂SiO₃)] were investigated for early H. perlevis juvenile growth. Interestingly, temperature changes have striking effects on juvenile growth. Juvenile sponges grow faster when they are shifted to higher temperatures (18°C to 23°C) than when they are shifted to lower temperatures (18°C to 4°C to 23°C) or kept at a constant temperature (18°C). Periodic water flow and light cycles favor early juvenile sponge growth. Light was found to be a key factor in the color loss of early H. perlevis juveniles. Overall, size (area) increased as much as 29 times for H. perlevis juveniles under the tested controlled conditions.     

Development of In Vivo Sponge Cultures: Particle Feeding by the Tropical Sponge Pseudosuberites aff. andrewsi

The rate of food particle uptake of the tropical sponge Pseudosuberites aff. andrewsi was studied in relation to particle concentrations and particle size. A range of different concentrations of either the marine microalga Dunaliella tertiolecta (∼5–8 μm) or the marine cyanobacterium Synechococcus sp. (∼1 μm) was supplied to the sponges. D. tertiolecta had a pronounced effect on the filtration activity of the sponges: at concentrations higher than approximately 4 × 10⁵ cells/cm³, the filtration rates dropped dramatically. Such a clear effect was not found for Synechococcus sp. The results further showed that the maximal amount of food (when expressed in organic carbon) that can be taken up per cubic centimeter of sponge volume per unit of time should in principle be sufficient to enable growth (irrespective of the food particle type). At the maximal food particle concentration that did not affect the filtration rates, the uptake of organic carbon is already highly in excess of the amount of organic carbon that the sponges need to cope with their respiratory demand. Based on these findings, a series of growth experiments was carried out in which the sponges were subjected to a constant concentration of different types of food particles (Synechococcus sp. and the microalgae Chlorella sorokiniana and Nannochloropsis sp). Although initial growth was sometimes observed, continuous growth at a constant rate could not be obtained. It is concluded that qualitative aspects of feeding rather than quantitative aspects are the key to successful in vivo sponge culture. Received December 20, 2000; accepted March 26, 2001     

Skeletal response of <Emphasis Type="Italic">Lophelia pertusa</Emphasis> (Scleractinia) to bioeroding sponge infestation visualised with micro-computed tomography

The skeleton morphology of the azooxanthellate cold-water coral Lophelia pertusa can be strongly influenced by invasive boring sponges that infest corallites in the still living part of the colony. Atypically swollen corallites of live Lophelia pertusa from the Galway Mound (Belgica Carbonate Mound Province, Porcupine Seabight, NE Atlantic), heavily excavated by boring organisms, have been examined with a wide range of non-destructive and destructive methods: micro-computed tomography, macro- and microscopic observations of the outer coral skeleton, longitudinal and transversal thin sections and SEM analyses of coral skeleton casts. As a result, three excavating sponge species have been distinguished within the coral skeleton: Alectona millari, Spiroxya heteroclita and Aka infesta. Furthermore, four main coral/sponge growth stages have been recognised: (1) cylindrical juvenile corallite/no sponge cavities; (2) flared juvenile corallite/linear sponge cavities (if present); (3) slightly swollen adult corallites/chambered oval sponge cavities; (4) very swollen adult corallites/widespread cavities. The inferred correlation between corallite morphology and boring sponge infestation has been detected in micro-computed tomography (micro-CT) images and confirmed in sponge trace casts and peculiar features of coral skeleton microstructure. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

Effects of dissolved oxygen levels on survival and growth in vitro of <Emphasis Type="Italic">Haliclona pigmentifera</Emphasis> (Demospongiae)

In vitro sponge cultures are considered as legitimate alternatives for utilizing marine sponges (Porifera) to yield bioactive molecules. Optimization of culture methodologies for enhancing sponge survival is in progress for the identification of the factors regulating sponge survival in vitro. Dissolved oxygen (DO) is an essential factor promoting sponge survival. However, the effects of variable DO levels on the in vitro survival responses of sponges are not fully understood. Hence, we have investigated the effects of variable DO levels on the survival of the marine sponge, Haliclona pigmentifera (Demospongiae), with no external nutritional supplementation in closed type incubator chambers. Our results indicate that, under hypoxic conditions (1.5-2.0 ppm DO), H. pigmentifera with intact ectodermal layers and subtle oscula show adherent growth for 42±3 days. Sponges with prominent oscula, foreign material, and damaged pinacoderm exhibit poor survival under similar conditions. Complete mortality occurs within 2 days under anoxia (<0.3 ppm DO), and survival for a few days has been observed at >4.0 ppm DO without adhesion. Cellular differences between the outer and inner zones and collagen-like extracellular matrix have been identified in adherent sponges. Based on the hypothesis that hypoxia-inducible factor1-α (HIF-1α) is a ubiquitous protein promoting hypoxic survival in animals, we have detected, by Western blot, a protein band corresponding to human HIF-1α-like protein from sponges exposed to hypoxia and to hypoxia-mimicking agents. We thus report, for the first time, adhesive growth and a protein band corresponding to human HIF-1α-like protein in sponges surviving hypoxia in vitro. This work was supported by the “Task Force Network Programme (CMM-004)” of the Council of Scientific and Industrial Research (CSIR), Government of India and by the Department of Ocean Development. CSIR is also acknowledged for providing a Senior Research Fellowship to V.G.G.     

Bacterial Uptake by the Marine Sponge <Emphasis Type="Italic">Aplysina aerophoba</Emphasis>

Sponges (Porifera) are filter feeders that take up microorganisms from seawater and digest them by phagocytosis. At the same time, many sponges are known to harbor massive consortia of symbiotic microorganisms, which are phylogenetically distinct from those in seawater, within the mesohyl matrix. In the present study, feeding experiments were performed to investigate whether phylogenetically different bacterial isolates, hereafter termed “food bacteria,” microbial seawater consortia, and sponge symbiont consortia are taken up and processed differently by the host sponge. Aplysina aerophoba retained high numbers of bacterial isolates and microbial seawater consortia with rates of up to 2.76 × 10⁶ bacteria (g sponge wet weight)^–1 h^–1, whereas the retention of sponge symbionts was lower by nearly two orders of magnitude [5.37 × 10⁴ bacteria (g sponge wet weight)⁻¹ h^–1]. In order to visualize the processing of a food bacterium within sponge tissues, the green fluorescent protein-labeled Vibrio strain MMW1, which had originally been isolated from A. aerophoba, was constructed. Incubation of this strain with A. aerophoba and subsequent visualization in tissue cryosections showed its presence in the choanocytes and/or endopinacocytes lining the canals but, unlike latex beads, not in deeper regions of the mesohyl, which suggests digestion of the bacteria upon contact with the host. Denaturing gradient gel electrophoresis (DGGE) was performed on the incubation seawater to monitor the changes in phylogenetic composition after incubation of the sponge with either seawater or sponge symbiont consortia. However, the DGGE experiment provided no evidence for selective processing of individual lineages by the host sponge. In conclusion, this study extends early studies by Wilkinson et al. (Proc R Soc London B 220:519–528, 1984) that sponges, here A. aerophoba, are able to differentiate between food bacteria and their own bacterial symbionts.     

Culturable heterotrophic bacteria from the marine sponge <Emphasis Type="Italic">Dendrilla</Emphasis> <Emphasis Type="Italic">nigra</Emphasis>: isolation and phylogenetic diversity of actinobacteria

Culturable heterotrophic bacterial composition of marine sponge Dendrilla nigra was analysed using different enrichments. Five media compositions including without enrichment (control), enriched with sponge extract, with growth regulator (antibiotics), with autoinducers, and complete enrichment containing sponge extract, antibiotics, and autoinducers were developed. DNA hybridization assay was performed to explore host specific bacteria and ecotypes of culturable sponge-associated bacteria. Enrichment with selective inducers (AHLs and sponge extract) and regulators (antibiotics) considerably enhanced the cultivation potential of sponge-associated bacteria. It was found that Marinobacter (MSI032), Micromonospora (MSI033), Streptomyces (MSI051), and Pseudomonas (MSI057) were sponge-associated obligate symbionts. The present findings envisaged that “Micromonospora–Saccharomonospora–Streptomyces” group was the major culturable actinobacteria in the marine sponge D. nigra. The DNA hybridization assay was a reliable method for the analysis of culturable bacterial community in marine sponges. Based on the culturable community structure, the sponge-associated bacteria can be grouped (ecotypes) as general symbionts, specific symbionts, habitat flora, and antagonists.     

Histological investigation of organisms with hard skeletons: a case study of siliceous sponges

Siliceous and calcareous sponges commonly are treated with acid to remove the spicules prior to embedding and cutting for histological investigations. Histology of spiculated sponge tissue represents a challenging problem in sponge histotechnology. Furthermore, fluorescence in situ hybridization (FISH), a key method for studying sponge-associated microbes, is not possible after acid treatment. For a broad range of siliceous sponge species, we developed and evaluated methods for embedding in paraffin, methylmethacrylate resins, LR White resin and cryomatrix. Different methods for cutting tissue blocks as well as mounting and staining sections also were tested. Our aim was to enable histological investigations and FISH without prior removal of the spicules. To obtain an overview of tissue and skeleton arrangement, we recommend embedding tissue blocks with LR White resin combined with en bloc staining techniques for large specimens with thick and numerous spicules, but paraffin embedding and subsequent staining for whole small specimens. For FISH on siliceous sponges, we recommend Histocryl embedding if the spicule content is high, but paraffin embedding if it is low. Classical histological techniques are used for detailed tissue examinations.     

Morphological plasticity in the tropical sponge Anthosigmella varians: responses to predators and wave energy

The goal of the research presented here was to examine phenotypic plasticity exhibited by three morphotypes of the common Caribbean sponge Anthosigmella varians (Duchassaing & Michelotti). We were interested in examining the biotic (and, to a lesser extent, abiotic) factors responsible for branch production in this species. We also tested the hypothesis that the skeleton may serve an antipredator function in this sponge, focusing on vertebrate fish predators (i.e., angelfish) in this work. In transplant and caging experiments, unprotected forma varians replicates were immediately consumed by angelfish, while caged replicates persisted on the reef for several months. These findings support the hypothesis that predators (and not wave energy) restrict forma varians to lagoonal habitats. Branch production was not observed in A. varians forma incrustans when sponges were protected from predators or placed in predator-free, low-wave-energy environments. It is not clear from our work whether forma incrustans is capable of producing branches (i.e., whether branch production is a plastic trait in this morph). Additional field experiments demonstrated that A. varians forma varians increased spicule concentrations, compared to uninjured sponges, in response to artificial predation events, and A. varians forma rigida reduced spicule concentrations, compared to uncaged controls, when protected from predators. These findings indicate that spicule concentration is a plastic morphological trait that can be induced by damage, and that A. varians may be able to reduce spicule concentrations when environmental conditions change (e.g., in the absence of predators). The potential significance of inducible defenses and structural anti-predator defenses in sponges is discussed in relation to recent work on sponge chemical defenses.     

A new species of Polymastia (Porifera, Hadromerida, Polymastiidae) from the Aleutian Islands, Alaska, USA

Polymastia fluegeli n. sp. is described from deep water off the Aleutian Islands (Alaska, USA). P. fluegeli is disc-shaped and lives partly buried in the sediment, with only the papillae protruding above the surface. This new species has a basal layer of agglutinated sediment particles occurring between the choanosome and the ectosomal lower layer. This conspicuous sediment layer is not described for other species of Polymastia. Occurring spicule types and sizes are different from known species of the area.     

Effect of wound size on the growth and regeneration of two temperate subtidal sponges

Physical and biological disturbances can damage and remove biomass from marine invertebrates such as sponges. To determine the effect of wound size on sponge recovery, individuals of the Demospongiae Latrunculia wellingtonensis (Alvarez, Berqguist and Battershill) and Polymastia croceus (Kelly-Borges and Bergquist) had 50%, 75%, 90% or none (control) of their volume removed. Regeneration (measured by oscule development), growth (percent and volume change), biofouling and survival were monitored often over 203 days using in situ photographs. The rate of regeneration and growth varied between the two sponges, being greatest for L. wellingtonensis. Interspecific variation may result from differences in choanosome structure: the choanosome in L. wellingtonensis is poorly differentiated but is well developed in P. croceus. For each species, recovery rates were similar between 50%, 75% and 90% removed sponges. All damaged L. wellingtonensis and P. croceus survived, demonstrating the remarkable ability of some sponge species to recovery from massive injuries. L. wellingtonensis and P. croceus are often found in exposed habitats. Good recovery after injury may therefore be an adaptation to reduce the damaging effects of storms and strong water movement.     

Tissue sloughing in the sponge Halichondria panicea: a fouling organism prevents being fouled

Summary Specimens of the sponge Halichondria panicea Pallas kept in running sea-water aquaria at 15° C slough off their complete outer tissue layer in regular intervals of three weeks. Sloughing starts at the rim of the oscula and extends over the whole surface within two weeks. Microscopic inspection of the tissue flakes shows them to harbour large numbers of different live organisms, as well as biogenic debris such as pieces of copepod carapaces and diatom frustules. No such community is found on freshly sloughed sponge tissue. After sloughing, the surface skeletal structure of H. panicea is markedly altered, as the characteristic halichondroid reticulum has been replaced by the irregular spicule array typical for the inner sponge tissue. When H. panicea is kept in closed aquaria filled with 0.2 m filtered sea-water, no sloughing occurs during 3 months of maintenance. As those sponges shedding their outer tissue grow steadily at the same time, the tissue sloughing can be regarded as a reaction to sedimentation of organic material and settlement of small organisms on the sponge surface. The sponge thus counteracts clogging of its ostia and prevents the establishment of a micro fouling community on its surface, inhibiting further fouling processes.     

Silicatein Genes in Spicule-Forming and Nonspicule-forming Pacific Demosponges

Silicatein genes are known to be involved in siliceous spicule formation in marine sponges. Proteins encoded by these genes, silicateins, were recently proposed for nanobiotechnological applications. We studied silicatein genes of marine sponges Latrunculia oparinae collected in the west Pacific region, shelf of Kuril Islands. Five silicatein genes, LoSilA1, LoSilA1a, LoSilA2, and LoSilA3 (silicatein-α group), LoSilB (silicatein-β group), and one cathepsin gene, LoCath, were isolated from the sponge L. oparinae for the first time. The deduced amino acid sequence of L. oparinae silicateins showed high-sequence identity with silicateins described previously. LoCath contains the catalytic triad of amino acid residues Cys-His-Asn characteristic for cathepsins as well as motifs typical for silicateins. A phylogenetic analysis places LoCath between sponge silicateins-β and L-cathepsins suggesting that the LoCath gene represents an intermediate form between silicatein and cathepsin genes. Additionally, we identified, for the first time, silicatein genes (AcSilA and AcSilB) in nonspicule-forming marine sponge, Acаnthodendrilla sp. The results suggest that silicateins could participate also in the function(s) unrelated to spiculogenesis.