Novel reference transcriptomes for the sponges Carteriospongia foliascens and Cliona orientalis and associated algal symbiont Gerakladium endoclionum

Transcriptomes from sponges are important resources for studying the stress responses of these ecologically important filter feeders, the interactions between sponges and their symbionts, and the evolutionary history of metazoans. Here, we generated reference transcriptomes for two common and cosmopolitan Indo-Pacific sponge species: Carteriospongia foliascens and Cliona orientalis. We also created a reference transcriptome for the primary symbiont of C. orientalis – Gerakladium endoclionum. To ensure a full repertoire of transcripts were included, clones of each sponge species were exposed to a range of individual stressors: decreased salinity, elevated temperature, elevated suspended sediment concentrations, sediment deposition and light attenuation. RNA extracted from all treatments was pooled for each species, using equal concentrations from each clone. Sequencing of pooled RNA yielded 409 and 418 million raw reads for C. foliascens and C. orientalis holobionts (host and symbionts), respectively. Reads underwent quality trimming before assembly with Trinity. Assemblies were filtered into sponge-specific or, for G. endoclionum, symbiont-specific assemblies. Assemblies for C. foliascens, C. orientalis, and G. endoclionum contained 67,304, 82,895, and 28,670 contigs, respectively. Contigs represented 15,248-37,344 isogroups (∼genes) per assembly, and N50s ranged 1,672-4,355 bp. Gene ortholog analysis verified a high level of completeness and quality for sponge-specific transcriptomes, with an average 93% of core EuKaryotic Orthologous Groups (KOGs) and 98% of single-copy metazoan core gene orthologs identified. The G. endoclionum assembly was partial with only 56% of core KOGs and 32% of single-copy eukaryotic core gene orthologs identified. These reference transcriptomes are a valuable resource for future molecular research aimed at assessing sponge stress responses.

The excavating sponge Cliona orientalis as a coral reef competitor’s on Krakatau Islands colonisation, Indonesia

The recovery of coral reefs on Krakatau Islands after the destructive eruption in 1883 has been reported in very limited study. Coral reefs began to grow on all islands in the Krakatau volcanic complex, including the highly active volcano island i.e. Anak Krakatau (north to west coast). Survival of coral reefs in the Krakatau Islands influenced by several factors such as predation, diseases, soft coral overgrowth, and also sediment covers. Somehow, sponges as one of killer-competitor of coral reefs have never been reported in the Krakatau Islands.

The excavating sponge Cliona orientalis as a coral reef competitor’s on Krakatau Islands colonisation, Indonesia

The recovery of coral reefs on Krakatau Islands after the destructive eruption in 1883 has been reported in very limited study. Coral reefs began to grow on all islands in the Krakatau volcanic complex, including the highly active volcano island i.e. Anak Krakatau (north to west coast). Survival of coral reefs in the Krakatau Islands influenced by several factors such as predation, diseases, soft coral overgrowth, and also sediment covers. Somehow, sponges as one of killer-competitor of coral reefs have never been reported in the Krakatau Islands.

Importance of philopatry and hydrodynamics in the recruitment of bioeroding sponges on Indonesian coral reefs

Increasingly frequent large-scale coral mortality events are occurring across the globe, leading to a rise in available reef substrata and promoting an increase in the abundance of other benthic taxa. One such group are bioeroding sponges, which can benefit considerably from reef degradation. However, the occupation of new substrates is partially reliant upon larval recruitment, and currently little is known about the factors affecting bioeroding sponge recruitment. In this study we investigated the potential drivers of bioeroding sponge recruitment using a 2-year deployment of experimental calcareous substrates across seven reefs in the Wakatobi region of Indonesia. Recruitment was observed for five bioeroding sponge species, namely Cliona orientalis, Cliothosa cf. aurivillii, Cliothosa hancocki and two presently unidentified brown clionaids, Cliona aff. viridis sp. A and Cliona aff. viridis sp. B. Recruits were present on 69% of the experimental substrates but had a low mean (±s.e.m.) spatial coverage of just 0.42±0.13%. Total recruitment and species assemblage structure were correlated with local adult abundance, water flow and substrate cues. Our results suggest that any proliferation of bioeroding sponges on newly available substrate following coral mortality is likely to be conditional on local adult abundance and hydrodynamics.

Integrating a thermistor flowmeter and time lapse imagery to monitor sponge (Porifera) behaviour

A digital, four-channel thermistor flowmeter was developed as an experimental tool for measuring pumping rates in marine sponges, particularly those with small excurrent pores (oscula). The flowmeter is integrated with time lapse cameras and has an accuracy of ±5 mm s-1 over the range of 5–200 mm s-1, a spatial resolution of 1.4 mm, and an adjustable temporal resolution of 5 seconds. Combining flowmeters with time lapse imagery yielded valuable insights into the contractile behaviour of oscula in Cliona orientalis, revealing four distinct oscula states: (1) osculum open with extended papilla, (2) osculum closed with extended papilla, (3) osculum closed with papilla retracted, and (4) osculum closed with papilla retracted and contraction of region surrounding osculum. Osculum area was positively correlated to measured excurrent velocities, indicating that sponge pumping and osculum contraction are coordinated behaviours. Diel trends in pumping activity and osculum contraction were also observed, with sponges increasing their pumping activity to peak at midday and decreasing pumping and contracting oscula at night. Short-term elevation of the suspended sediment concentration within the seawater initially decreased pumping rates by up to 90%, ultimately resulting in closure of the oscula and cessation of pumping. The thermistor flowmeter developed here will be a valuable tool to monitor behaviour, physiology and ecophysiology of sponges.

Integrating a thermistor flowmeter and time lapse imagery to monitor sponge (Porifera) behaviour

A digital, four-channel thermistor flowmeter was developed as an experimental tool for measuring pumping rates in marine sponges, particularly those with small excurrent pores (oscula). The flowmeter is integrated with time lapse cameras and has an accuracy of ±5 mm s-1 over the range of 5–200 mm s-1, a spatial resolution of 1.4 mm, and an adjustable temporal resolution of 5 seconds. Combining flowmeters with time lapse imagery yielded valuable insights into the contractile behaviour of oscula in Cliona orientalis, revealing four distinct oscula states: (1) osculum open with extended papilla, (2) osculum closed with extended papilla, (3) osculum closed with papilla retracted, and (4) osculum closed with papilla retracted and contraction of region surrounding osculum. Osculum area was positively correlated to measured excurrent velocities, indicating that sponge pumping and osculum contraction are coordinated behaviours. Diel trends in pumping activity and osculum contraction were also observed, with sponges increasing their pumping activity to peak at midday and decreasing pumping and contracting oscula at night. Short-term elevation of the suspended sediment concentration within the seawater initially decreased pumping rates by up to 90%, ultimately resulting in closure of the oscula and cessation of pumping. The thermistor flowmeter developed here will be a valuable tool to monitor behaviour, physiology and ecophysiology of sponges.