Clownfish hosting anemones (Anthozoa, Actiniaria) of the Red Sea: new associations and distributions, historical misidentifications, and morphological variability

Background The Red Sea contains thousands of kilometers of fringing reef systems inhabited by clownfish and sea anemones, yet there is no consensus regarding the diversity of host anemone species that inhabit this region. We sought to clarify a historical record and recent literature sources that disagree on the diversity of host anemone species in the Red Sea, which contains one endemic anemonefish, Amphiprion bicinctus Rüppell 1830. Results We conducted 73 surveys spanning ~ 1600 km of coastline from the northern Saudi Arabian Red Sea to the Gulf of Aden and encountered seven species of host anemones, six of which hosted A. bicinctus. We revise the list of symbionts for A. bicinctus to include Stichodactyla haddoni (Saville-Kent, 1893) and Stichodactyla mertensii Brandt, 1835 which were both observed in multiple regions. We describe Red Sea phenotypic variability in Heteractis crispa (Hemprich & Ehrenberg in Ehrenberg, 1834) and Heteractis aurora (Quoy & Gaimard, 1833), which may indicate that these species hybridize in this region. We did not encounter Stichodactyla gigantea (Forsskål, 1775), although the Red Sea is the type locality for this species. Further, a thorough review of peer-reviewed literature, occurrence records, and misidentified basis of record reports dating back to the early twentieth century indicate that it is unlikely that S. gigantea occurs in the Red Sea. Conclusions In sum, we present a new guide for the host anemones of the Red Sea, revise the host specificity of A. bicinctus, and question whether S. gigantea occurs in the central and western Indian Ocean.

The importance and movement of mud bacterial carbon within the symbiosis of the New Zealand sea anemone Anthopleura aureoradiata

<p>A. aureoradiata is New Zealand’s only native cnidarian to form a phototrophic symbiosis with dinoflagellate microalgae. It is of particular interest as it can be found in estuarine mudflat habitats attached to cockles, where it spends a portion of the day submerged under the mud, either partially or completely. This scenario is very different to the situation in the tropics, where comparable symbioses (e.g. those with reef-building corals) live in brightly lit, clear waters. How A. aureoradiata maintains a stable symbiosis is therefore of considerable interest, with one potential mechanism involving the acquisition of carbon from the surrounding mud to counter the reduced availability of light and hence the reduced rate of photosynthesis. In this thesis, I established the extent to which organic carbon in mud (especially bacteria) can be assimilated by A. aureoradiata and to what extent, if any, this carbon contributes to symbiosis nutrition and facilitates symbiosis stability under otherwise sub-optimal conditions. In the first instance, anemones were given access to¹³C glucose-labelled mud for 12 hours, in both the light and dark, and the extent of label incorporation (¹³C enrichment) in both the host and symbiont was measured by mass spectrometry. Subsequently, A. aureoradiata was starved of planktonic food for six weeks in the presence of differing quantities of unlabelled mud (‘no-mud’, ‘low-mud’ and ‘high-mud’), either with or without light, and a range of nutritional and biomass parameters measured. These included symbiont density, host protein content, and the accumulation of host lipid and symbiont starch stores. Both the host anemone and its symbiotic algae showed signs of ¹³C uptake from the mud. Host anemones maintained in the dark assimilated more ¹³C label from the mud than did anemones incubated in the light, while the extent of label assimilation by the symbionts was unaffected by irradiance. Enhanced heterotrophic feeding in the dark is consistent with patterns reported for other symbiotic cnidarians, such as reef corals, where the host must counter the reduced availability of photosynthate from the symbiotic algae. However, the reason for the equal labelling of the symbionts in the light and dark is less clear. Nevertheless, factors such as reverse translocation in the dark (i.e. the transfer of organic carbon from host to symbiont), dark fixation of inorganic carbon, and a higher respiration rate of symbionts in the light than dark, could act either alone or in concert to produce the labelling pattern seen. While the host and symbiont showed evidence of carbon uptake from the surrounding mud, mud quantity had no effect on either the host’s or symbiont’s storage products (% of starch in symbiont biomass, host protein content and lipid content), or on symbiont density. The lack of an effect of mud suggests that mud-derived bacteria comprise little of the host’s natural diet. In contrast, increased light availability (independent of mud availability) did lead to elevated symbiont density and symbiont starch content, consistent with the phototrophic nature of this symbiosis. More surprising was that host protein content was highest in the dark, suggesting perhaps that the symbionts were less of an energetic drain on their host when starved in the dark due to their lower population density. In summary, my thesis provides evidence that A. aureoradiata and its symbiotic algae can use organic carbon obtained from the surrounding mud for their nutrition, but that this carbon source is of only negligible importance. These results are consistent with previous findings for the uptake and role of mud-derived nitrogen in this system. Further work to establish how this symbiosis maintains its remarkable stability under apparently sub-optimal, low-light conditions is therefore needed.</p>

The importance and movement of mud bacterial carbon within the symbiosis of the New Zealand sea anemone Anthopleura aureoradiata

<p>A. aureoradiata is New Zealand’s only native cnidarian to form a phototrophic symbiosis with dinoflagellate microalgae. It is of particular interest as it can be found in estuarine mudflat habitats attached to cockles, where it spends a portion of the day submerged under the mud, either partially or completely. This scenario is very different to the situation in the tropics, where comparable symbioses (e.g. those with reef-building corals) live in brightly lit, clear waters. How A. aureoradiata maintains a stable symbiosis is therefore of considerable interest, with one potential mechanism involving the acquisition of carbon from the surrounding mud to counter the reduced availability of light and hence the reduced rate of photosynthesis. In this thesis, I established the extent to which organic carbon in mud (especially bacteria) can be assimilated by A. aureoradiata and to what extent, if any, this carbon contributes to symbiosis nutrition and facilitates symbiosis stability under otherwise sub-optimal conditions. In the first instance, anemones were given access to¹³C glucose-labelled mud for 12 hours, in both the light and dark, and the extent of label incorporation (¹³C enrichment) in both the host and symbiont was measured by mass spectrometry. Subsequently, A. aureoradiata was starved of planktonic food for six weeks in the presence of differing quantities of unlabelled mud (‘no-mud’, ‘low-mud’ and ‘high-mud’), either with or without light, and a range of nutritional and biomass parameters measured. These included symbiont density, host protein content, and the accumulation of host lipid and symbiont starch stores. Both the host anemone and its symbiotic algae showed signs of ¹³C uptake from the mud. Host anemones maintained in the dark assimilated more ¹³C label from the mud than did anemones incubated in the light, while the extent of label assimilation by the symbionts was unaffected by irradiance. Enhanced heterotrophic feeding in the dark is consistent with patterns reported for other symbiotic cnidarians, such as reef corals, where the host must counter the reduced availability of photosynthate from the symbiotic algae. However, the reason for the equal labelling of the symbionts in the light and dark is less clear. Nevertheless, factors such as reverse translocation in the dark (i.e. the transfer of organic carbon from host to symbiont), dark fixation of inorganic carbon, and a higher respiration rate of symbionts in the light than dark, could act either alone or in concert to produce the labelling pattern seen. While the host and symbiont showed evidence of carbon uptake from the surrounding mud, mud quantity had no effect on either the host’s or symbiont’s storage products (% of starch in symbiont biomass, host protein content and lipid content), or on symbiont density. The lack of an effect of mud suggests that mud-derived bacteria comprise little of the host’s natural diet. In contrast, increased light availability (independent of mud availability) did lead to elevated symbiont density and symbiont starch content, consistent with the phototrophic nature of this symbiosis. More surprising was that host protein content was highest in the dark, suggesting perhaps that the symbionts were less of an energetic drain on their host when starved in the dark due to their lower population density. In summary, my thesis provides evidence that A. aureoradiata and its symbiotic algae can use organic carbon obtained from the surrounding mud for their nutrition, but that this carbon source is of only negligible importance. These results are consistent with previous findings for the uptake and role of mud-derived nitrogen in this system. Further work to establish how this symbiosis maintains its remarkable stability under apparently sub-optimal, low-light conditions is therefore needed.</p>

Rank Change and Growth Within Social Hierarchies of the Orange Clownfish, Amphiprion Percula

Social hierarchies within groups define the distribution of resources and provide benefits that support the collective group or favor dominant members. The progression of individuals through social hierarchies is a valuable characteristic for quantifying population dynamics. On coral reefs, a number of small site-attached fish maintain size-based hierarchical communities where individuals queue through social ranks. The cost of waiting in a lower-ranked position is outweighed by the reduced risk of eviction and mortality. Clownfish exist in stable social groups with subordinate individuals queuing to be part of the dominant breeding pair. Site attachment to their host anemone, complex social interactions, and relatively low predation rates make them ideal model organisms to assess changes in group dynamics through time in their natural environment. Here, we investigate the rank changes, and isometric growth rates of individual orange clownfish, Amphiprion percula, from 247 naturally occurring social groups in Kimbe Island, Papua New Guinea (5°12’13.54” S, 150°22’32.69” E). We use DNA profiling to assign and track individuals over an eight-year time period in 2011 and 2019. Over half of the individuals survived alongside two or three members of their original social group, with twelve breeding pairs persisting over the study period. Half of the surviving individuals increased in rank and experienced double the growth rate of those that maintained their rank. Examining rank change over a long-term period in a wild fish population gives new insights and highlights the complexity and importance of rank and social hierarchy in communal site-attached reef fish.Subject Area: behavior, ecology, evolution

Microbiomes of clownfish and their symbiotic host anemone converge before their first physical contact

Background One of the most charismatic, and yet not completely resolved example of mutualistic interaction is the partnership of clownfish and its symbiotic sea anemone. The mechanism explaining this tolerance currently relies on the molecular mimicry of clownfish epithelial mucus, which could serve as camouflage, preventing the anemone's nematocysts' discharge. Resident bacteria are known as key drivers of epithelial mucus chemical signature in vertebrates. A recent study has proposed a restructuration of the skin microbiota in a generalist clown fish when first contacting its symbiotic anemone. We explored a novel hypothesis by testing the effect of remote interaction on epithelial microbiota restructuration in both partners. Methods With metataxonomics, we investigated the epithelial microbiota dynamic of 18 pairs of percula clownfish (Amphiprion percula) and their symbiotic anemone Heteractis magnifica in remote interaction, physical interaction and control groups for both partners during a 4-week trial. Results The Physical and Remote Interaction groups’ results evidence gradual epithelial microbiota convergence between both partners when fish and anemone were placed in the same water system. This convergence occurred preceding any physical contact between partners, and was maintained during the 2-week interaction period in both contact groups. After the interaction period, community structure of both fish and anemone’s epthelial community structures maintained the interaction signature 2 weeks after fish–anemone pairs’ separation. Furthermore, the interaction signature persistence was observed both in the Physical and Remote Interaction groups, thus suggesting that water-mediated chemical communication between symbiotic partners was strong enough to shift the skin microbiota durably, even after the separation of fish–anemone pairs. Finally, our results suggest that fish–anemone convergent microbiota restructuration was increasingly associated with the parallel recruitment of three Flavobacteriaceae strains closely related to a tyrosinase-producing Cellulophaga tyrosinoxydans. Conclusions Our study shows that bacterial community restructuration, in the acclimation process, does not only rely on direct physical contact. Furthermore, our results challenge, for the first time, the traditional unidirectional chemical camouflage hypothesis, as we argue that convergence of the epithelial microbiota of both partners may play essential roles in establishing mutual acceptance.

Microbiomes of Clownfish and Their Symbiotic Host Anemone Converge Before Their First Physical Contact

BackgroundOne of the most charismatic, and yet not completely resolved example of mutualistic interaction is the partnership of clownfish and its symbiotic sea anemone. The mechanism explaining this tolerance currently relies on the molecular mimicry of clownfish epithelial mucus, which could serve as camouflage, preventing the anemone's nematocysts' discharge. Resident bacteria are known as key drivers of epithelial mucus chemical signature in vertebrates. A recent study has proposed a restructuration of the skin microbiota in a generalist clown fish when first contacting its symbiotic anemone. We explored a novel hypothesis by testing the effect of remote interaction on epithelial microbiota restructuration in both partners. MethodsWith metataxonomics, we investigated the epithelial microbiota dynamic of 18 pairs of percula clownfish (Amphiprion percula) and their symbiotic anemone Heteractis magnifica in remote interaction, physical interaction and control groups for both partners during a four weeks trial.ResultsPhysical and Remote Interaction groups’ results evidence gradual epithelial microbiota convergence between both partners when fish and anemone were placed in the same water system. This convergence occurred preceding any physical contact between partners, and was maintained during the two-weeks interaction period in both contact groups. After the interaction period, community structure of both fish and anemone’s epthelial community structures maintained the interaction signature two weeks after fish-anemone pairs separation. Furthermore, the interaction signature persistence was observed both in Physical and Remote Interaction groups, thus suggesting that water-mediated chemical communication between symbiotic partners was strong enough to shift the skin microbiota durably, even after the separation of fish-anemone pairs. Finally, our results suggest that fish-anemone convergent microbiota restructuration was increasingly associated with the parallel recruitment of three Flavobacteriaceae strains closely related to a tyrosinase-producing Cellulophaga tyrosinoxydans. ConclusionsOur study shows that bacterial community restructuration, in the acclimation process, does not only rely on direct physical contact. Furthermore, our results challenge, for the first time, the traditional unidirectional chemical camouflage hypothesis, as we argue that convergence of the epithelial microbiota of both partners may play essential roles in establishing mutual acceptance.

Microbiomes of Clownfish and Their Symbiotic Host Anemone Converge Before Their First Physical Contact.

BackgroundOne of the most charismatic, and yet not completely resolved example of mutualistic interaction is the partnership of clownfish and its symbiotic sea anemone. The mechanism explaining this tolerance currently relies on the molecular mimicry of clownfish epithelial mucus, which could serve as camouflage, preventing the anemone's nematocysts' discharge. Resident bacteria are known as key drivers of epithelial mucus chemical signature in vertebrates. A recent study has proposed a restructuration of the skin microbiota in a generalist clown fish when first contacting its symbiotic anemone. We explored a novel hypothesis by testing the effect of remote interaction on epithelial microbiota restructuration in both partners. MethodsWith metataxonomics, we investigated the epithelial microbiota dynamic of 18 pairs of percula clownfish (Amphiprion percula) and their symbiotic anemone Heteractis magnifica in remote interaction, physical interaction and control groups for both partners during a four weeks trial.ResultsPhysical and Remote Interaction groups’ results evidence gradual epithelial microbiota convergence between both partners when fish and anemone were placed in the same water system. This convergence occurred preceding any physical contact between partners, and was maintained during the two-weeks interaction period in both contact groups. After the interaction period, community structure of both fish and anemone’s epthelial community structures maintained the interaction signature two weeks after fish-anemone pairs separation. Furthermore, the interaction signature persistence was observed both in Physical and Remote Interaction groups, thus suggesting that water-mediated chemical communication between symbiotic partners was strong enough to shift the skin microbiota durably, even after the separation of fish-anemone pairs. Finally, our results suggest that fish-anemone convergent microbiota restructuration was increasingly associated with the parallel recruitment of three Flavobacteriaceae strains closely related to a tyrosinase-producing Cellulophaga tyrosinoxydans. ConclusionsOur study shows that bacterial community restructuration, in the acclimation process, does not only rely on direct physical contact. Furthermore, our results challenge, for the first time, the traditional unidirectional chemical camouflage hypothesis, as we argue that convergence of the epithelial microbiota of both partners may play essential roles in establishing mutual acceptance.

Microbiomes of Clownfish and Their Symbiotic Host Anemone Converge Before Their First Physical Contact.

BackgroundOne of the most charismatic, and yet not completely resolved example of mutualistic interaction is the partnership of clownfish and its symbiotic sea anemone. The mechanism explaining this tolerance currently relies on the molecular mimicry of clownfish epithelial mucus, which could serve as camouflage, preventing the anemone's nematocysts' discharge. Resident bacteria are known as key drivers of epithelial mucus chemical signature in vertebrates. A recent study has proposed a restructuration of the skin microbiota in a generalist clown fish when first contacting its symbiotic anemone. We explored a novel hypothesis by testing the effect of remote interaction on epithelial microbiota restructuration in both partners. MethodsWith metataxonomics, we investigated the epithelial microbiota dynamic of 18 pairs of percula clownfish (Amphiprion percula) and their symbiotic anemone Heteractis magnifica in remote interaction, physical interaction and control groups for both partners during a four weeks trial.ResultsPhysical and Remote Interaction groups’ results evidence gradual epithelial microbiota convergence between both partners when fish and anemone were placed in the same water system. This convergence occurred preceding any physical contact between partners, and was maintained during the two-weeks interaction period in both contact groups. After the interaction period, community structure of both fish and anemone’s epthelial community structures maintained the interaction signature two weeks after fish-anemone pairs separation. Furthermore, the interaction signature persistence was observed both in Physical and Remote Interaction groups, thus suggesting that water-mediated chemical communication between symbiotic partners was strong enough to shift the skin microbiota durably, even after the separation of fish-anemone pairs. Finally, our results suggest that fish-anemone convergent microbiota restructuration was increasingly associated with the parallel recruitment of three Flavobacteriaceae strains closely related to a tyrosinase-producing Cellulophaga tyrosinoxydans. ConclusionsOur study shows that bacterial community restructuration, in the acclimation process, does not only rely on direct physical contact. Furthermore, our results challenge, for the first time, the traditional unidirectional chemical camouflage hypothesis, as we argue that convergence of the epithelial microbiota of both partners may play essential roles in establishing mutual acceptance.

Microbiomes of clownfish and their symbiotic host anemone converge before their first physical contact

BackgroundOne of the most charismatic, and yet not completely resolved example of mutualistic interaction is the partnership of clownfish and its symbiotic sea anemone. The mechanism explaining this tolerance currently relies on the molecular mimicry of clownfish epithelial mucus, which could serve as camouflage, preventing the anemone's nematocysts' discharge. Resident bacteria are known as key drivers of epithelial mucus chemical signature in vertebrates. A recent study has proposed a restructuration of the skin microbiota in a generalist clown fish when first contacting its symbiotic anemone. We explored a novel hypothesis by testing the effect of remote interaction on epithelial microbiota restructuration in both partners. MethodsWith metataxonomics, we investigated the epithelial microbiota dynamic of 18 pairs of percula clownfish (Amphiprion percula) and their symbiotic anemone Heteractis magnifica in remote interaction, physical interaction and control groups for both partners during a four weeks trial.ResultsPhysical and Remote Interaction groups’ results evidence gradual epithelial microbiota convergence between both partners when fish and anemone were placed in the same water system. This convergence occurred preceding any physical contact between partners, and was maintained during the two-weeks interaction period in both contact groups. After the interaction period, community structure of both fish and anemone’s epthelial community structures maintained the interaction signature two weeks after fish-anemone pairs separation. Furthermore, the interaction signature persistence was observed both in Physical and Remote Interaction groups, thus suggesting that water-mediated chemical communication between symbiotic partners was strong enough to shift the skin microbiota durably, even after the separation of fish-anemone pairs. Finally, our results suggest that fish-anemone convergent microbiota restructuration was increasingly associated with the parallel recruitment of three Flavobacteriaceae strains closely related to a tyrosinase-producing Cellulophaga tyrosinoxydans. ConclusionsOur study shows that bacterial community restructuration, in the acclimation process, does not only rely on direct physical contact. Furthermore, our results challenge, for the first time, the traditional unidirectional chemical camouflage hypothesis, as we argue that convergence of the epithelial microbiota of both partners may play essential roles in establishing mutual acceptance.

Microbiomes of clownfish and their symbiotic host anemone converge before their first physical contact

BackgroundOne of the most charismatic, and yet not completely resolved example of mutualistic interaction is the partnership of clownfish and its symbiotic sea anemone. The mechanism explaining this tolerance currently relies on the molecular mimicry of clownfish epithelial mucus, which could serve as camouflage, preventing the anemone's nematocysts' discharge. Resident bacteria are known as key drivers of epithelial mucus chemical signature in vertebrates. A recent study has proposed a restructuration of the skin microbiota in a generalist clown fish when first contacting its symbiotic anemone. We explored a novel hypothesis by testing the effect of remote interaction on epithelial microbiota restructuration in both partners. MethodsWith metataxonomics, we investigated the epithelial microbiota dynamic of 18 pairs of percula clownfish (Amphiprion percula) and their symbiotic anemone Heteractis magnifica in remote interaction, physical interaction and control groups for both partners during a four weeks trial.ResultsPhysical and Remote Interaction groups’ results evidence gradual epithelial microbiota convergence between both partners when fish and anemone were placed in the same water system. This convergence occurred preceding any physical contact between partners, and was maintained during the two-weeks interaction period in both contact groups. After the interaction period, community structure of both fish and anemone’s epthelial community structures maintained the interaction signature two weeks after fish-anemone pairs separation. Furthermore, the interaction signature persistence was observed both in Physical and Remote Interaction groups, thus suggesting that water-mediated chemical communication between symbiotic partners was strong enough to shift the skin microbiota durably, even after the separation of fish-anemone pairs. Finally, our results suggest that fish-anemone convergent microbiota restructuration was increasingly associated with the parallel recruitment of three Flavobacteriaceae strains closely related to a tyrosinase-producing Cellulophaga tyrosinoxydans. ConclusionsOur study shows that bacterial community restructuration, in the acclimation process, does not only rely on direct physical contact. Furthermore, our results challenge, for the first time, the traditional unidirectional chemical camouflage hypothesis, as we argue that convergence of the epithelial microbiota of both partners may play essential roles in establishing mutual acceptance.