Host Anemones Research Articles

Manganese Uptake and Partitioning between the Tissue of the Anemone Host Exaiptasia Pallida and Symbiodinium Sp., Including Assessment of Stress and Recovery

Manganese Uptake and Partitioning between the Tissue of the Anemone Host Exaiptasia Pallida and Symbiodinium Sp., Including Assessment of Stress and Recovery

Keep your friends close and your anemones closer – ecology of the endemic wideband anemonefish, Amphiprion latezonatus

Endemic marine species often exist as metapopulations distributed across several discrete locations, such that their extinction risk is dependent upon population dynamics and persistence at each location. The anemonefish Amphiprion latezonatus is a habitat specialist, endemic to two oceanic islands (Lord Howe and Norfolk) and the adjacent eastern Australian coast from the Sunshine Coast to Southwest Rocks. To determine how extinction risk varies across the limited number of locations where A. latezonatus occurs, we quantified ecological, biological, and behavioural characteristics at six locations and four reef zones. The abundance of A. latezonatus and its host anemones varied considerably throughout its range, with A. latezonatus abundance being very low at Sunshine Coast and Elizabeth Reef, low at Lord Howe Island and Norfolk Island, and moderate at North Solitary Island. This species was not detected at Middleton Reef, despite local abundance of their host anemones. Abundance of A. latezonatus was generally correlated with depth and host anemone abundance, from which we infer that extirpation risk is directly proportional to their host anemone population’s size. Consistent with this, A. latezonatus social group size was positively correlated with the number of anemones inhabited. A. latezonatus may be impacted by interactions and competition with other anemonefish species in shallow (< 10 m) waters, but competition has little effect in deeper water where population abundances are highest. Significant differences in population characteristics demonstrate a need for location-specific conservation strategies and identify the Sunshine Coast population as most vulnerable.

Loss of natural coastline influences species diversity of anemonefish and host anemones in the Ryukyu Archipelago

Abstract Anemonefish and host anemones are distributed in the shallow waters of coral reefs, and thus their existence may be affected by coastal development. The Ryukyu Archipelago includes the Okinawa and Sakishima Islands; the former has experienced extensive land reclamation and drainage in coastal areas while the latter still mostly contains natural coasts. To consider the layout of protected areas needed to conserve diversity of host anemones and anemonefish in the Ryukyu Archipelago, the community structure and coexistence mechanisms of anemones and anemonefish were compared between Okinawa and Sakishima Islands. Six species of anemonefish and seven species of host anemone are distributed in both islands. Among 15 species‐pair interactions observed in six species of anemonefish in the Sakishima Islands, 14 were explained by the niche differentiation hypothesis and only one interaction was explained by the cohabitation hypothesis. In the Okinawa Islands, 13 interactions were explained by the niche differentiation hypothesis, one by the cohabitation hypothesis and one by the lottery hypothesis. For both host anemones and anemonefish, β‐diversity in the Okinawa Islands was lower and had a more nested structure than that of the Sakishima Islands. β‐Diversity and its nestedness did not differ between the two regions excluding study sites adjacent to coastlines, suggesting that differences in the coastal environment affected the diversity of anemones and anemonefish in the Ryukyu Archipelago. These results suggested that there is an urgent need to prioritize the conservation of reef edges, where species diversity is relatively higher than directly next to the terrestrial coastline in Okinawa Island. In the Sakishima Islands, where many natural coasts remain, a wider area from directly next to the coast out to the reef edge needs to be comprehensively protected to increase β‐diversity.

Anemonefish aggressiveness affects the presence of Dascyllus trimaculatus co-existing with host anemones

One of the most well-known symbiosis of coral reefs is the relationship between host anemones and anemonefish. Host anemones are used not only by anemonefish but also by other species such as the immature phase of the three spot damsel (Dascyllus trimaculatus). Anemonefish can be a superior competitor to D. trimaculatus, which shares host anemones as shelter resources. Interspecific competition for shelter resources is considered to be an important factor affecting community structure in coral reef fish. In this study, we investigated the factors affecting host anemone utilization of D. trimaculatus around Okinawajima Island. Among 296 colonies, D. trimaculatus inhabited 52 (= 17.6%) host anemones. Decision tree analyses (CHAID) using five independent variables (species of host anemone and anemonefish, presence/absence of adult anemonefish, numbers of immature anemonefish, and size of host anemone) revealed that D. trimaculatus rarely occupied the anemones Entacmaea quadricolor and Stichodactyla haddoni, and seldom cohabited with Amphiprion frenatus and A. polymnus. We experimentally presented a clay model of D. trimaculatus to colonies of six species of anemonefish and compared the duration of aggressive behavior. The aggressive behaviors of A. frenatus and A. polymnus were significantly longer and more intense than that of the other four species. Our findings demonstrate that species composition in anemone symbioses may be affected by coexisting anemonefish as aggressive behavior toward intruders differs among species.

Five-year study on the bleaching of anemonefish-hosting anemones (Cnidaria: Anthozoa: Actiniaria) in subtropical Okinawajima Island

Since the 1980s, coral bleaching mainly due to rising seawater temperatures has become a serious problem for subtropical and tropical coral reefs around the world. Coral bleaching and the associated loss of corals have a negative impact on taxonomic richness of creatures. Bleaching is seen not only in hard corals (order Scleractinia), but also in other zooxanthellate animals, including anemonefish-hosting anemones (order Actiniaria), where it is known to significantly impact symbiotic anemonefish as well as other organisms. However, to date, there have been few continuous studies on bleaching and its effects on anemones and anemonefish. Therefore, in this study, we recorded the water temperature and the status of bleaching for individual host anemones and symbiotic anemonefish on the western coast of Okinawajima Island over five years from November 2014 to October 2019. In the summers of 2016 and 2017, when abnormally higher water temperatures were observed during ENSO events, five out of 30 host anemones bleached. All individuals of host anemone that bleached in 2016 again bleached in 2017, and these anemones took longer to recover in 2017 than in 2016. Anemonefish pairs inhabiting the five bleached host anemones survived these bleaching periods; however, one of the bleached anemones along with its associated anemonefish disappeared subsequent to the 2017 bleaching. The present study indicates that if abnormally high seawater temperatures continue in consecutive summers, recovery of host anemones from bleaching may become impaired, and associated mortality events may increase.

Host identity and symbiotic association affects the taxonomic and functional diversity of the clownfish-hosting sea anemone microbiome.

All eukaryotic life engages in symbioses with a diverse community of bacteria that are essential for performing basic life functions. In many cases, eukaryotic organisms form additional symbioses with other macroscopic eukaryotes. The tightly linked physical interactions that characterize many macroscopic symbioses create opportunities for microbial transfer, which likely affects the diversity and function of individual microbiomes, and may ultimately lead to microbiome convergence between distantly related taxa. Here, we sequence the microbiomes of five species of clownfish-hosting sea anemones that co-occur on coral reefs in the Maldives. We test the importance of evolutionary history, clownfish symbiont association, and habitat on the taxonomic and predicted functional diversity of the microbiome, and explore signals of microbiome convergence in anemone taxa that have evolved symbioses with clownfishes independently. Our data indicate that host identity and clownfish association shapes the majority of the taxonomic diversity of the clownfish-hosting sea anemone microbiome, and predicted functional microbial diversity analyses demonstrate a convergence among host anemone microbiomes, which reflect increased functional diversity over individuals that do not host clownfishes. Further, we identify upregulated predicted microbial functions that are likely affected by clownfish presence. Taken together our study potentially reveals an even deeper metabolic coupling between clownfishes and their host anemones, and what could be a previously unknown mutualistic benefit to anemones that are symbiotic with clownfishes.

Cophylogenetic analysis of the relationship between anemonefish Amphiprion (Perciformes: Pomacentridae) and their symbiotic host anemones (Anthozoa: Actiniaria)

ABSTRACTThe association between anemonefish and anemone is a classical example of mutualism in coral reefs. Although mutualism is probably the key innovation that triggered the adaptive radiation of anemonefish into a wide range of habitats, the coevolutionary history between the groups has not been thoroughly tested in a phylogenetic framework. We examined the evolutionary history of the association via distance-based (Parafit and PACo) and event-based methods (Core-PA, Jane). Mitochondrial DNA sequences (COI mtDNA, Cytb, 16S rDNA and 12S rDNA) were used to reconstruct the phylogenies of tropical Amphiprion species and their host anemones by using maximum likelihood with best-fit models selected. Neither distance-based analyses nor event-based analyses revealed global significant congruence between the phylogenies of the hosts and the symbionts, and thus no evidence for coevolution between anemone-anemonefish. However, at the individual pair level, the fish showed some dependence on anemone hosts. Even though living in close association and benefiting from each other, the change of genetic composition of one species (anemonefish) does not always evolve in response to changes in the other (anemones). These findings expand our understanding of the pattern and the role of evolutionary events to allow a better prediction of the future of the anemonefish-anemone relationship.

Symbiont population control by host-symbiont metabolic interaction in Symbiodiniaceae-cnidarian associations

In cnidarian-Symbiodiniaceae symbioses, algal endosymbiont population control within the host is needed to sustain a symbiotic relationship. However, the molecular mechanisms that underlie such population control are unclear. Here we show that a cnidarian host uses nitrogen limitation as a primary mechanism to control endosymbiont populations. Nitrogen acquisition and assimilation transcripts become elevated in symbiotic Breviolum minutum algae as they reach high-densities within the sea anemone host Exaiptasia pallida. These same transcripts increase in free-living algae deprived of nitrogen. Symbiotic algae also have an elevated carbon-to-nitrogen ratio and shift metabolism towards scavenging nitrogen from purines relative to free-living algae. Exaiptasia glutamine synthetase and glutamate synthase transcripts concomitantly increase with the algal endosymbiont population, suggesting an increased ability of the host to assimilate ammonium. These results suggest algal growth and replication in hospite is controlled by access to nitrogen, which becomes limiting for the algae as their population within the host increases.

Comparative phylogeography of three host sea anemones in the Indo‐Pacific

AbstractAimThe mutualistic relationship between anemones and anemonefishes is one of the most iconic examples of symbiosis. However, while anemonefishes have been extensively studied in terms of genetic connectivity, such information is lacking entirely for host sea anemones. Here, we provide the first information on the broad‐scale population structure and phylogeographical patterns of three species of host sea anemone, Heteractis magnifica, Stichodactyla mertensii and Entacmaea quadricolor. We evaluate if there is concordance in genetic structure across several distinct biogeographical areas within the Indo‐Pacific region and to what extent the observed patterns may concur with those found for anemonefishes.LocationIndo‐Pacific, including the Red Sea.TaxonHeteractis magnifica, S. mertensii and E. quadricolorMethodsMicrosatellite markers and a combination of statistical methods including Bayesian clustering, isolation by distance (IBD), analysis of molecular variance (AMOVA) and principal components analysis (PCA) were used to determine population structure. The congruence among distance matrices (CADM) method was used to assess similarity in spatial genetic patterns among species.ResultsSignificant population structure was identified in the three host anemone species. Each species is likely composed of at least two genetic clusters corresponding to two biogeographical regions, the Red Sea and the rest of the Indo‐Pacific. Two of the three anemone species seem to be experiencing admixture where the two main clusters overlap (the Maldives). IBD analyses in the Red Sea revealed differences in gene flow among species, suggesting more limited dispersal potential for E. quadricolor than for S. mertensii and H. magnifica. Clonality is documented in S. mertensii for the first time.Main conclusionsThis research documents the genetic population structure for three ecologically important host sea anemones across the Indo‐Pacific and provides valuable insights regarding their biogeography and evolution. Specifically, we found high levels of genetic divergence between populations across different biogeographical regions, suggesting different evolutionary lineages within species. At the same time, common geographical overlap of population structures suggests similar evolutionary histories among all three species. Interestingly, the observed patterns are congruent to some extent with structure reported for several anemonefish species, reflecting their close ecological association.

Crustacean symbiosis with Caribbean sea anemones Bartholomea annulata: occupancy modeling, habitat partitioning, and persistence

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 631:99-116 (2019) - DOI: https://doi.org/10.3354/meps13160 Crustacean symbiosis with Caribbean sea anemones Bartholomea annulata: occupancy modeling, habitat partitioning, and persistence Lindsay K. Huebner1,2,*, Colin P. Shea2, Paul M. Schueller3, Ashley D. Terrell1, Stephen G. Ratchford4, Nanette E. Chadwick1 1Department of Biological Sciences, Auburn University, Auburn, Alabama 36849, USA 2Fish & Wildlife Research Institute, Florida Fish & Wildlife Conservation Commission, St. Petersburg, Florida 33701, USA 3Fish & Wildlife Research Institute, Florida Fish & Wildlife Conservation Commission, Gainesville, Florida 32653, USA 4College of Science and Math, University of the Virgin Islands, St. Thomas, US Virgin Islands 00802, USA *Corresponding author: lindsay.huebner@myfwc.com ABSTRACT: Coral reef cnidarians often host crustaceans in multi-level symbioses that may cause reef-wide impacts, especially through anemoneshrimp cleaner interactions with fish clients. Despite the ubiquity and importance of these interactions, patterns of temporal and spatial variation in crustacean association with sea anemones remain largely unknown. We censused corkscrew sea anemones Bartholomea annulata and crustacean associates (5 shrimp and 1 crab species) every 3-6 mo for 2.5 yr at 2 reef sites in St. Thomas, US Virgin Islands. Crustacean abundance per anemone varied with species and census period. Occupancy rates increased with anemone body size, more so offshore where anemones were smaller and less abundant than inshore. Four species of obligate anemoneshrimps partitioned space among 5 microhabitat zones on the host anemone body. Dynamic multi-state models revealed that anemone persistence was enhanced primarily by anemone body size, with variable secondary effects of site and anemoneshrimp species. The presence of the snapping shrimp Alpheus armatus did not enhance the persistence of host anemones. However, the presence of the dedicated cleaner shrimp Ancylomenes pedersoni enhanced the persistence of small host anemones at the inshore site but reduced the persistence of the occasional cleaner shrimp Periclimenes yucatanicus on host anemones, indicating mutualistic and competitive interactions among some partners in this system. Patterns of association among anemones and crustaceans varied significantly at both temporal (seasonal and annual) and spatial scales (among anemones and reef sites), with implications for the ecology of client fishes that visit these Caribbean anemones to receive cleaning services from anemoneshrimps. KEY WORDS: Multi-state occupancy model · Anemoneshrimp · Alpheus armatus · Ancylomenes pedersoni · Periclimenes yucatanicus · Heteromysis actiniae · Mutualism · Coral reef Full text in pdf format Supplementary material PreviousNextCite this article as: Huebner LK, Shea CP, Schueller PM, Terrell AD, Ratchford SG, Chadwick NE (2019) Crustacean symbiosis with Caribbean sea anemones Bartholomea annulata: occupancy modeling, habitat partitioning, and persistence. Mar Ecol Prog Ser 631:99-116. https://doi.org/10.3354/meps13160 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 631. Online publication date: November 21, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

A detailed investigation of the visual system and visual ecology of the Barrier Reef anemonefish, Amphiprion akindynos

Vision plays a major role in the life of most teleosts, and is assumingly well adapted to each species ecology and behaviour. Using a multidisciplinary approach, we scrutinised several aspects of the visual system and ecology of the Great Barrier Reef anemonefish, Amphiprion akindynos, including its orange with white patterning, retinal anatomy and molecular biology, its symbiosis with anemones and sequential hermaphroditism. Amphiprion akindynos possesses spectrally distinct visual pigments and opsins: one rod opsin, RH1 (498 nm), and five cone opsins, SWS1 (370 nm), SWS2B (408 nm), RH2B (498 nm), RH2A (520 nm), and LWS (554 nm). Cones were arranged in a regular mosaic with each single cone surrounded by four double cones. Double cones mainly expressed RH2B (53%) in one member and RH2A (46%) in the other, matching the prevailing light. Single cones expressed SWS1 (89%), which may serve to detect zooplankton, conspecifics and the host anemone. Moreover, a segregated small fraction of single cones coexpressed SWS1 with SWS2B (11%). This novel visual specialisation falls within the region of highest acuity and is suggested to increase the chromatic contrast of Amphiprion akindynos colour patterns, which might improve detection of conspecifics.

Social behavior of the Pederson cleaner shrimp Ancylomenes pedersoni (Chace, 1958) (Decapoda: Caridea: Palemonidae) in the Caribbean Sea: size- and gender-based dominance hierarchy

AbstractSocial interactions among Pederson cleaner shrimp Ancylomenes pedersoni (Chace, 1958), an associate of sea anemones, likely affect cleaning services to reef fishes, but major aspects of their social group structure and behavior remain unknown. We hypothesized that Pederson shrimp form dominance hierarchies expressed through size- and gender-based behavioral interactions. Observation of 116 shrimp on coral reefs at St. Thomas, US Virgin Islands, revealed that they formed social groups of ~3 or 4 individuals (range 1–9) per host sea anemone, as a mix of large females, medium-size males, and/or small juveniles. Social groups were not rigidly size-structured, in that body size ratio between adjacent individuals did not differ significantly from random. Individuals, however, were spatially structured such that distance between shrimp and the tentacles of the host anemone decreased significantly with shrimp body size; large individuals occupied the anemone tentacle crown, whereas smaller shrimp perched on reef or sand substrates adjacent to the anemone. During laboratory experiments, shrimp exhibited five types of exploitation competition behaviors toward client fish models (signal, approach, clean, no response, retreat), and four types of interference competition behaviors toward conspecific shrimp (approach, attack, no response, retreat). Large females more frequently signaled toward, approached, and cleaned fish models than did males and juveniles, which did not respond or retreated. Females also approached and attacked conspecifics more than did males and juveniles, which retreated at frequencies that increased with decreasing body size. We conclude that Pederson shrimp form gender and size-based hierarchies in which large females monopolize food resources (ectoparasites on client fishes), and interfere with resource access by smaller males and juveniles. These behaviors cause them to spatially partition microhabitats on anemones, and hypothetically could lead to males and juveniles dispersing among anemones more frequently than females. These shrimp social interactions may thus enhance spatial and temporal variation among cleaning stations, with consequences for the health and mobility of reef fishes.

Nickel uptake in Symbiodynium spp. and host cnidarian -assessment using the model cnidarian Exaiptasia pallida

Start Nickel (Ni) is common marine pollutant and derived from discharge of industries, mining and agriculture. Elevated Ni concentrations, could be harmful the organisms in marine environment such as corals reef. The sea anemones Exaiptasia pallida has been widely used for toxicity tests in the laboratory because it is easy to maintain and culture in contained aquarium conditions. To understand the pathway of uptake and storage of elevated Ni between the sea anemone host and symbiotic algae, and the model sea anemone E. pallida was exposed to three different Ni concentrations (500 xg/L, 1000 xg/L, 2000 xg/L) and control treatment over 9 days and 18 days. Ni accumulation was assessed in both the host anemone tissues and the Symbiodinium spp. The concentration of Ni was measured using Perkin Elmer NexION 300D ICPMS (Inductively Couple Plasma Mass Spectrophotometry) after sampel digestion. The statistical analysis was completed using R version 3.5.0 (R core team 2013) R Foundation for Statistical Computing, Vienne, Austria. The model was chosen by Akaike Information Criterion (AIC) after to comparing between model options. Shapiro-Wilks test was used to verify the normal distribution of the date set to be analysed.The overall result showed the accumulation of nickel was highest in Symbiodinium spp. (212.62 + 50.12 mg/Kg) after a 9 days exposure period in concentration 2000 xg/L while 18 days exposure period was less ( 129.66 + 31,94 mg/Kg) in concentration 2000 xg/L. The lower uptake of Ni in Symbiodinium spp. in the longer exposure time of 18 days compare to 9 days exposure might be due to the ability of Symbiodinium spp. to release the Ni through their metabolism or the Ni dose may have inhibited normal function of the algae, although the accumulation of both times period was significantly higher than the control treatments. Meanwhile, host anemones accumulated 77.43 + 6.28 mg/Kg Ni over 9 days exposure period and the 2000 xg/L treatment and increased after 18 days exposure in concentration 2000 xg/L (45.54 + 4.12 mg/Kg).The result of these finding highlight the importance of understanding the metal accumulation in host and cnidarian. This is particularly important if these species are used in biomonitoring studies where bleaching may occur due to stress, but may in effect be a depuration pathway for metal load, masking the biological uptake and interaction between metal and organisms.

Phylogenetic relationships among the clownfish-hosting sea anemones

The clownfish-sea anemone symbiosis has been a model system for understanding fundamental evolutionary and ecological processes. However, our evolutionary understanding of this symbiosis comes entirely from studies of clownfishes. A holistic understanding of a model mutualism requires systematic, biogeographic, and phylogenetic insight into both partners. Here, we conduct the largest phylogenetic analysis of sea anemones (Order Actiniaria) to date, with a focus on expanding the biogeographic and taxonomic sampling of the 10 nominal clownfish-hosting species. Using a combination of mtDNA and nuDNA loci we test (1) the monophyly of each clownfish-hosting family and genus, (2) the current anemone taxonomy that suggests symbioses with clownfishes evolved multiple times within Actiniaria, and (3) whether, like the clownfishes, there is evidence that host anemones have a Coral Triangle biogeographic origin. Our phylogenetic reconstruction demonstrates widespread poly- and para-phyly at the family and genus level, particularly within the family Stichodactylidae and genus Stichodactyla, and suggests that symbioses with clownfishes evolved minimally three times within sea anemones. We further recover evidence for a Tethyan biogeographic origin for some clades. Our data provide the first evidence that clownfish and some sea anemone hosts have different biogeographic origins, and that there may be cryptic species of host anemones. Finally, our findings reflect the need for a major taxonomic revision of the clownfish-hosting sea anemones.

Host choice and fitness of anemonefish Amphiprion ocellaris (Perciformes: Pomacentridae) living with host anemones (Anthozoa: Actiniaria) in captive conditions.

In this study, we investigated the host choice of naïve Amphiprion ocellaris, a specialist, at two different stages of development (newly settling juveniles and post‐settlement juveniles). The fish were exposed to their natural and unnatural host species in the laboratory and their fitness was assessed in terms of activity and growth rate. Newly settling juveniles exhibited little host preference, while post‐settlement juveniles immediately associated with their most common host in the wild. The analysis of fish activity confirmed that A. ocellaris is diurnal; they are most active in the morning, less at midday and barely move at night. The average travelling distance of juveniles was shorter in the groups living with their natural host, increasing in the groups living with an unnatural host and was highest in groups that did not become associated with any other unnatural host species. Post‐settlement juveniles living with the natural host species grew better than those living with unnatural hosts or without anemone contact. These results suggest that the welfare of A. ocellaris in captivity will be optimized by keeping them with their natural anemone host species, although more generalist Amphiprion species may survive in association with other hosts.

Low density populations of anemonefish with low replenishment rates on a reef edge with anthropogenic impacts

The population dynamics of anemonefish are expected to have unique patterns because of the symbiotic relationship with host anemones. Recent anthropogenic impacts may affect the abundance of anemones, which may also affect population dynamics of anemonefish. However, long-term field studies and demographic data on reproduction, immigration, and mortality rates are deficient. Here, we investigated the dynamics of anemonefish for 3 years on the reef edge with anthropogenic impacts of Okinawa-jima Island, southern Japan. During the study period, six species of host anemone were used as spawning grounds by four species of anemonefish, and as nurseries by six species of immature anemonefish. The density of breeding pairs was low (0.21–1.46 /ha), which may have been restricted by the abundance of host anemones. Survival rates were different among species; from 0.21 to 1.00 over 3 years. Ten cases of dissolution of breeding pairs were observed during the 3 years, and only five pairs were replenished. Through the study period, 215 individuals of six species of immature fish immigrated into the study site, and this number was skewed due to higher numbers of Amphiprion clarkii (77.7%). Demographic patterns differed among species, and requirements for conservation will therefore be different among species on the reef edges of Okinawa-jima Island under anthropogenic impact.

Is ancestral hybridization fuelling adaptive radiation in clownfishes?

Event Abstract Back to Event Is ancestral hybridization fuelling adaptive radiation in clownfishes? Sarah Schmid1*, Baptiste Micheli1, Anna Marcionetti1, Joris Bertrand2 and Nicolas Salamin1 1 Université de Lausanne, Switzerland 2 Université de Perpignan Via Domitia, France The contribution of hybridization in the generation of global species diversity has long been a subject of controversy among evolutionary biologists. However it is now increasingly accepted that hybridization has many impacts on the process of speciation. Especially, it is an important mechanism fostering adaptive radiation, because it can generate new phenotypic combinations enabling the occupancy of new niches. Here, we focused on clownfish (Pomacentridae), a clade of 28 coral reef fishes displaying a mutualistic interaction with sea anemones. This behavior is the key innovation that triggered adaptive radiation of clownfishes, as each species is able to occupy a different combination of host anemone species and habitat. Previous work suggested that hybridization might be responsible for the extant diversity of clownfish species. To test this hypothesis, we analyzed whole-genome datasets for each clownfish species. First, we reconstructed the phylogeny of the clade based on topology weighting method, which enables the visualization of the relationships between taxa across the genome. Then, we highlighted possible ancient hybridization events based on comparative genomic framework for detecting introgression in genomes. We highlighted a large amount of significant hybridization between the different clades, which suggests that hybridization occurred between the ancestors of the current species. Moreover, patterns of high heterogeneity in the phylogenetic relationships across the genome might be a consequence of the combined effect of extensive hybridization and polygenic barrier loci. Taken together, these results support the hypothesis of ancestral hybridization occurring during the evolutionary history of clownfishes. Keywords: hybridization, speciation, adaptive radiation, Clownfish, Genomics Conference: XVI European Congress of Ichthyology, Lausanne, Switzerland, 2 Sep - 6 Sep, 2019. Presentation Type: Oral Topic: EVOLUTIONARY GENOMICS OF FISHES Citation: Schmid S, Micheli B, Marcionetti A, Bertrand J and Salamin N (2019). Is ancestral hybridization fuelling adaptive radiation in clownfishes?. Front. Mar. Sci. Conference Abstract: XVI European Congress of Ichthyology. doi: 10.3389/conf.fmars.2019.07.00043 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 29 May 2019; Published Online: 14 Aug 2019. * Correspondence: Mx. Sarah Schmid, Université de Lausanne, Lausanne, Switzerland, sarah.schmid@unil.ch Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Sarah Schmid Baptiste Micheli Anna Marcionetti Joris Bertrand Nicolas Salamin Google Sarah Schmid Baptiste Micheli Anna Marcionetti Joris Bertrand Nicolas Salamin Google Scholar Sarah Schmid Baptiste Micheli Anna Marcionetti Joris Bertrand Nicolas Salamin PubMed Sarah Schmid Baptiste Micheli Anna Marcionetti Joris Bertrand Nicolas Salamin Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Host anemone size as a determinant of social group size and structure in the orange clownfish (Amphiprion percula).

The size and structure of social groups of animals can be governed by a range of ecological factors and behavioral interactions. In small, highly site-attached coral reef fishes, group size is often constrained by the size of the habitat patch they are restricted to. However, group size may also be influenced by changes in abundance along important environmental gradients, such as depth or distance offshore. In addition, the body size and sex structure within social groups can be determined by the size of the habitat patch and the dominance relationships among group members. Here we examined the roles of ecological factors and behavioral interactions in governing group size and structure in the orange clownfish, Amphiprion percula, on inshore reefs in Kimbe Bay, Papua New Guinea. We quantified relationships between ecological variables (anemone size, depth, and distance from shore) and social group variables (group size, and total body length of the three largest individuals (ranks 1, 2, and 3)). Anemone size explained the greatest amount of variation in group variables, with strong, positive relationships between anemone surface area and group size, and total length of individuals ranked 1, 2, and 3. Group structure was also weakly correlated with increasing depth and distance from shore, most likely through the indirect effects of these environmental gradients on anemone size. Variation in group size and the lengths of ranks 2 and 3 were all closely related to the length of rank 1. Path analysis indicated that anemone size has a strong direct effect on the length of rank 1. In turn, the length of rank 1 directly affects the size of the subordinate individuals and indirectly affects the group size through its influence on subordinates. Hence, anemone size directly and indirectly controls social group size and structure in this space-limited fish species. It is also likely that anemonefish have feedback effects on anemone size, although this could not be differentiated in the path analysis.

Patterns of coexistence of six anemonefish species around subtropical Okinawa-jima Island, Japan

The species diversity of anemonefish in tropical regions has been explained by the niche differentiation hypothesis or cohabitation hypothesis. However, anemonefish community structure has seldom been investigated in high-latitude areas. To understand the mechanism underlying species diversity of anemonefish in the northern limits of their distribution and to compare with previous results from tropical and other areas, we investigated the community structure of anemonefish around the western coast of Okinawa-jima Island, Japan. Seven species of host anemones and six species of anemonefish were distributed across the 12 study sites. The diversity index of anemonefish and the host anemone varied among sites; anemonefish diversity increased with diversity of host anemones, which was associated with the ratio of sandy areas and distance from shore. The density of each species of anemonefish increased with the density of the primary host anemone, which suggests that niche differentiation may be occurring. However, results of two species of host anemone (Stichodactyla mertensii, Heteractis magnifica) associated each with two species of anemonefish did not support the niche differentiation hypothesis. Forty-seven percent of S. mertensii were shared by Amphiprion clarkii and A. sandaracinos simultaneously, supporting the cohabitation hypothesis. Amphiprion ocellaris and A. perideraion used the same host H. magnifica, but never shared a host simultaneously. Moreover, anemone size and water depth did not differ between the two anemonefish species, suggesting the possibility of the lottery model. In subtropical Okinawa, 86.7% of species interactions supported the niche differentiation hypothesis, 6.7% supported the cohabitation hypothesis, and 6.7% supported the lottery hypothesis. The mechanisms of coexistence of anemonefish in subtropical regions include not only niche differentiation and cohabitation but also the lottery hypothesis, which has not been reported in tropical regions.

Scary clowns: adaptive function of anemonefish coloration.

Clownfishes, with their showy coloration, are well known for their symbiosis with sea anemones and for their hierarchical reproductive system, but the function of their coloration is unclear. We used a phylogeny of 27 clownfish species to test whether fish coloration (i) serves a protective function that involves their anemone hosts, or (ii) signals species identity in species with overlapping host ranges that can potentially share the same host. We tested for an association between fish colour pattern traits, host morphology and host toxicity and examined coloration in relation to host sharing and geographic proximity. Fish with fewer stripes occupied fewer anemone species, and hosts with shorter tentacles, than fish with multiple stripes. There was a negative relationship between anemone toxicity and tentacle length and these protective traits together were correlated with the evolution of stripes. Host sharing or range overlap was not associated with coloration divergence. We propose that ancestral anemonefishes had multiple stripes that served for hiding/camouflage among the hosts' long tentacles, whereas increased specialization towards fewer and more toxic hosts (with shorter tentacles) led to the use of coloration as an aposematic signal. The intriguing notion that an aposematic signal could advertise the defence of another species may reflect the unique symbiotic relationship between anemonefishes and their hosts.