Biology subjects

Conaco, C.

Publications and source records attributed to Conaco, C..

8 recordsLinked to original sources

bioRxiv2026

Host and environment shape the giant clam-associated photosymbiont community

Giant clams are some of the largest bivalve molluscs. They form a vital partnership with Symbiodiniaceae dinoflagellates that supply most of their energetic requirements. However, the factors that shape giant clam-associated photosymbiont communities remain unknown. Here, we profiled Symbiodiniaceae communities using ITS2 metabarcoding in eight giant clam species (Hippopus hippopus, H. porcellanus, Tridacna crocea, T. derasa, T. gigas, T. maxima, T. noae and T. squamosa) from 11 sites across the Philippine archipelago. Symbiodiniaceae community structure was shaped by an interplay between giant clam host and environment. Most giant clams were dominated by members of a single symbiont genus, with Cladocopium as the most prevalent, followed by Durusdinium and Symbiodinium. However, giant clam hosts also exhibited flexibility in their symbiotic partners that was evident across sites. Differences in giant clam-associated symbiont communities may contribute to differences in holobiont function and adaptability to variable environments. These findings deepen our understanding of giant clam-Symbiodiniaceae associations, offering a framework for predicting how giant clams may be affected by increasingly stressful reef conditions and, more importantly, informing strategies to improve mariculture and conservation practices.

ecology↗

bioRxiv2026

Influence of ocean warming and acidification on juveniles of the true giant clam, Tridacna gigas, and its microalgal symbionts

Uncontrolled carbon dioxide emissions from human activities contribute to ocean warming and acidification. These alterations in ocean chemistry threaten marine organisms, such as the true giant clam, Tridacna gigas, which is already imperiled due to overharvesting and habitat destruction. To gain an understanding of the physiological and molecular responses of T. gigas and its symbiotic dinoflagellates to ocean warming and acidification, we subjected juvenile individuals to different treatments simulating predicted seawater pH (7.6 and 8.0) and temperature (28{degrees}C, 30{degrees}C, 32{degrees}C and 34{degrees}C) levels for the next century. Juvenile giant clams were able to tolerate sustained exposure to temperatures of up to 32{degrees}C and pH as low as 7.6, while exposure to higher temperature (34{degrees}C), regardless of pH level, resulted in total mortality after a week. However, symbiosis was compromised even in the sublethal treatments, as indicated by the decrease in Symbiodiniaceae density and changes in symbiont gene expression. Symbionts significantly upregulated genes involved in splicing, translation, fatty acid metabolism, and DNA repair, which may constitute an adaptive response, while downregulating genes involved in photosynthesis and transmembrane transport, suggests impaired transfer of photosynthates to the host. These findings demonstrate the vulnerability of the juvenile T. gigas holobiont to heat stress, highlighting the critical importance of continued conservation and management alongside efforts to mitigate global changes in ocean conditions to safeguard this iconic marine bivalve. Summary StatementThis study investigates physiological and molecular responses of Tridacna gigas to seawater warming and acidification, providing insights into the potential future of endangered giant clam populations in a changing ocean.

zoology↗

bioRxiv2025

Phytoplankton and giant virus dynamics during different monsoon seasons, a fish kill, and a toxic bloom in a eutrophic mariculture area

Harmful algal blooms (HABs) pose a significant public health concern and can cause severe economic losses. In Bolinao, Philippines, intensive mariculture has led to diatom- or dinoflagellate-dominated HABs since the 2000s, raising risks of paralytic shellfish poisonings and fish kills. In the context of ongoing HAB monitoring and mitigation efforts, we investigated the phytoplankton and associated giant viruses during two seasons (Nov-Dec 2021 and Apr-May 2022). Our sampling encompassed a saxitoxin episode lasting 2.5 months (April-June 2022), and a fish kill (May 15-16, 2022). We used a low-cost flow-through camera (PlanktoScope) and 18S rRNA gene amplicon sequencing to identify the dominant phytoplankton. We detected the presence of Alexandrium sp., a known saxitoxin-producing alga, coincident with a toxin alert that resulted in a shellfish ban, even though it was not the dominant taxon. Using electron microscopy, we observed diverse morphologies of virus-like particles (VLPs), including "giant" icosahedral VLPs (~200 nm capsids). We assembled giant virus genomes from metagenomic data collected at different bloom phases. Phylogenetic and functional analyses suggest that the recovered genomes are primarily from viruses in the orders Imitervirales and Algavirales, encoding diverse auxiliary metabolic genes involved in nutrient transport and carbohydrate metabolism. The diversity and spatiotemporal dynamics of plankton and their viruses described in this study contributed to our understanding of the broader microbial context of HABs. ImportanceHABs are widespread phenomena that can be detrimental to livelihoods and health in coastal communities. Understanding what drives their formation, maintenance, and crash could aid in predicting, and potentially alleviating these events. Here, we report on the diversity and temporal dynamics of phytoplankton and giant viruses during a HAB event. Our findings revealed a diverse array of giant viruses belonging to thirteen families in a eutrophic coastal environment. We found evidence of associations between several phytoplankton-giant virus pairs and found a temporal/seasonal influence on phytoplankton-giant virus community structure. While future research is needed to establish definitive links between the giant viruses and HABs species succession, this study lays the groundwork for future mechanistic studies.

microbiology↗

bioRxiv2024

Microbiome stability is linked to coral thermotolerance

Corals associate with a diverse community of prokaryotic symbionts that provide nutrition, antioxidants, and other protective compounds to their host. However, the influence of microbes on coral thermotolerance remains understudied. Here, we examined the prokaryotic microbial communities associated with colonies of Acropora cf. tenuis that exhibit high or low thermotolerance upon exposure to 33{degrees}C (heated) relative to 29{degrees}C (control). Using 16S rRNA sequencing, we show that the microbial community structure of all A. cf. tenuis colonies were similar at control temperature. Thermotolerant colonies, however, had relatively greater abundance of Endozoicomonas, Arcobacter, Bifidobacterium and Lactobacillus. At elevated temperature, only thermosensitive colonies showed a distinct shift in their microbiome, with an increase in Flavobacteriales, Rhodobacteraceae, and Vibrio, accompanying a marked bleaching response. Functional prediction indicated that prokaryotic communities associated with thermotolerant corals were enriched for genes related to metabolism, while microbiomes of thermosensitive colonies were enriched for cell motility and antibiotic compound synthesis. These differences may contribute to the variable performance of thermotolerant and thermosensitive corals under thermal stress. Identification of microbial taxa correlated with thermotolerance provides insights into beneficial bacterial groups that could be used for microbiome engineering to support reef health in a changing climate.

microbiology↗

bioRxiv2024

Ultrastructural and transcriptional changes during a giant virus infection of a green alga

The complete genome sequence of the Oceanusvirus kaneohense strain (Tetraselmis virus 1; TetV-1) was previously reported, but little is known about the virus infection cycle. Using a permissive Tetraselmis isolate (UHM1315), we estimated the eclipse period (4-8 hours), latent period (16 hrs), and burst size (800-1000) of the virus and documented ultrastructural and transcriptional changes in the host during infection. Putative viral factories and electron-dense inclusion bodies appeared in the cytoplasm of infected cells by 8 and 16 h post-infection, respectively. The nucleus and chloroplasts appeared to remain intact but reduced in size after 8 h. Transcriptome sequencing suggests that the viral genome codes for 830 transcripts. Those expressed early in infection (eclipse period at 0.25 and 4 hr) were related to the initiation of transcription, DNA synthesis, translation, and host immune repression. During the later, post-eclipse period (8, 12, 16 hr), virus structural genes were expressed. For the algal host, transcripts related to lipid metabolism and endocytosis were upregulated during the early phase, while those for protein modification/ turnover/ transport were downregulated. In the later period, host transcripts associated with basic cellular processes were upregulated, while genes related to morphogenesis/development were downregulated. Many of the most highly expressed virus and host genes were of unknown function, highlighting a need for additional functional studies.

microbiology↗

bioRxiv2024

Interspecies differences in the transcriptome response of corals to acute heat stress

Rising sea surface temperatures threaten the survival of corals worldwide, with coral bleaching events becoming more commonplace. However, different coral species are known to exhibit variable levels of susceptibility to thermal stress events. To elucidate genetic mechanisms that may underlie these differences, we compared the gene complement of four coral species, Favites colemani, Montipora digitata, Acropora digitifera, and Seriatopora caliendrum, that were previously demonstrated to have differing responses to acute thermal stress. We found that more tolerant species, like F. colemani and M. digitata, possess a greater abundance of antioxidant protein families and chaperones. Under acute thermal stress conditions, only S. caliendrum showed a significant bleaching response, which was accompanied by activation of DNA damage response network and drastic upregulation of stress response genes (SRGs). This suggests that differences in SRG complement, as well as the mechanisms that control SRG expression response, contribute to the ability of corals to maintain stable physiological functions that is required to survive shifts in seawater temperature.

genomics↗

bioRxiv2024

Trophic niche partitioning in symbiotic marine invertebrates

Fierce competition for food and space underpins coral reefs biodiversity - supported by photosymbiotic foundational species. In contrast to other ecosystems, there is scant evidence that competition is mitigated by niche partitioning. Indeed, the dynamic evolutionary lineages of symbiotic partners and their syntrophy create layers of nutritional complexity that obfuscate patterns that structurn reef communities. As conspicuous members of Indo-Pacific reefs - giant clams co-occur with reef-building corals and similarly associate with algal symbionts. Using a common garden experiment, we analyzed stable isotope values from six giant clam species in the Philippines. These data, along with published data from ten sympatric corals, were used to calculate a novel metric - the Host Evaluation: Reliance on Symbionts (HERS) index - to assess variations in relative trophic strategies. Consistent with trophic niche partitioning - all species fell along an autotrophy-heterotrophy gradient with little overlap. We found a significant phylogenetic signal in clam HERS score, highlighting the role of selection in their nutritional ecology. We conclude that niche partitioning comes with tradeoffs, where predominantly autotrophic species showed higher growth rates but higher susceptibility to stress and consequently - greater conservation concern. TeaserTrophic niche partitioning plays a role in symbiotic marine invertebrate evolution with benefits and costs.

ecology↗

bioRxiv2021

Microbiome diversity and host immune functions may define the fate of sponge holobionts under future ocean conditions

The sponge-associated microbial community contributes to the overall health and adaptive capacity of the sponge holobiont. This community is regulated by the environment, as well as the immune system of the host. However, little is known about the effect of environmental stress on the regulation of host immune functions and how this may, in turn, affect sponge-microbe interactions. In this study, we compared the microbiomes and immune repertoire of two sponge species, the demosponge, Neopetrosia compacta and the calcareous sponge, Leucetta chagosensis, under varying levels of acidification and warming stress. Neopetrosia compacta harbors a diverse bacterial assemblage and possesses a rich repertoire of scavenger receptors while L. chagosensis has a less diverse microbiome and an expanded range of pattern recognition receptors and proteins with immunological domains. Upon exposure to warming and acidification, the microbiome and host transcriptome of N. compacta remained stable, which correlated with high survival. In contrast, the bacterial community of L. chagosensis exhibited drastic restructuring and widespread downregulation of host immune-related pathways, which accompanied tissue necrosis and mortality. Differences in microbiome diversity and immunological repertoire of diverse sponge groups highlight the central role of host-microbe interactions in predicting the fate of sponges under future ocean conditions.

microbiology↗