Host Anemones Research Articles

Effect of symbiotic state on the fatty acid composition of Anthopleura elegantissima

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 545:175-187 (2016) - DOI: https://doi.org/10.3354/meps11606 Effect of symbiotic state on the fatty acid composition of Anthopleura elegantissima Andrés J. Quesada1,*, Katherina L. Schoo2, Brian L. Bingham1 1Department of Environmental Sciences, Western Washington University, 516 High Street, Bellingham, WA 98225, USA 2Shannon Point Marine Center, Western Washington University, 1900 Shannon Point Road, Anacortes, WA 98221, USA *Corresponding author: andresjquesada@gmail.com ABSTRACT: Anthopleura elegantissima, the most abundant intertidal sea anemone on the Pacific coast of North America, naturally occurs in 3 distinct symbiotic states: zooxanthellate (hosting the dinoflagellate Symbiodinium muscatinei), zoochlorellate (hosting the chlorophyte Elliptochloris marina), and asymbiotic (lacking symbionts). To document the effect of symbiotic state on host lipids, 10 A. elegantissima in each symbiotic state were collected from the same location and habitat. The symbiont and host tissues were separated, and the fatty acid profiles were compared (1) between the 2 symbionts themselves, (2) among anemones in the 3 symbiotic states, and (3) between the symbionts and their host anemones. Significant differences were present in the fatty acid profiles of S. muscatinei and E. marina, with docosahexaenoic acid (DHA) abundant in S. muscatinei, and oleic and α-linolenic acids abundant in E. marina. Zooxanthellate anemone tissues had significantly higher total fatty acid content than did tissues of zoochlorellate hosts, supporting suggestions that S. muscatinei is more productive and thus a better symbiont. Asymbiotic sea anemones had significantly lower concentrations of total fatty acids than hosts in either symbiotic state and overall lower levels of most fatty acids. Previous research suggests that symbionts translocate specific fatty acids to their coral hosts, but there was no evidence for fatty acid translocation in A. elegantissima. Our results support the suggestions that hosting photosymbionts increases the fitness of A. elegantissima and that S. muscatinei is a better symbiotic partner. KEY WORDS: Anthopleura elegantissima · Elliptochloris marina · Fatty acid content · Sea anemone · Symbiodinium muscatinei · Symbiosis · Zoochlorellae · Zooxanthellae Full text in pdf format PreviousNextCite this article as: Quesada AJ, Schoo KL, Bingham BL (2016) Effect of symbiotic state on the fatty acid composition of Anthopleura elegantissima. Mar Ecol Prog Ser 545:175-187. https://doi.org/10.3354/meps11606 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 545. Online publication date: March 08, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Field experiments on individual adaptation of the spider crab Inachus phalangium to its sea anemone host Anemonia viridis in the northern Adriatic Sea

We studied the adaptation of the spider crab Inachus phalangium (Fabricius, 1755) to one of its sea anemone host species, Anemonia viridis (Forsskål, 1775) in the coastal region of Rovinj, Croatia. Similar to other brachyuran species, Inachus spp. generally lives within the anemone to obtain protection from possible predators. Using removal and reintroduction experiments, this study investigates the protection mechanism and shows a loss of adaptation after a period of 10 days when the crabs are taken out of their host and kept solitary. Thirty-nine anemones from two different trial sites were marked individually and the inhabiting crabs were isolated to be released back into their individual hosts later. The reactions of the anemones were closely observed and characterized to determine the respective state of crab adaptation. As 35 out of 39 individuals provoked a defense /attack reaction of the anemone, it is concluded that the crabs possessed some sort of non-permanent protection mechanism that was lost during the test run (chi-square test, p < 0.00014). All tested crabs re-inhabited their host anemones within a maximum of 20 minutes after they had been reintroduced and stung by the anemones. Therefore, habituation to the host’s defense / attack mechanism is acquired individually and not genetically inherent to the species. The results are compared to adaptation and protection data on other decapod crustaceans and some anemonefishes.

Hierarchical behaviour, habitat use and species size differences shape evolutionary outcomes of hybridization in a coral reef fish.

Hybridization is an important evolutionary process, with ecological and behavioural factors influencing gene exchange between hybrids and parent species. Patterns of hybridization in anemonefishes may result from living in highly specialized habitats and breeding status regulated by size-based hierarchal social groups. Here, morphological, ecological and genetic analyses in Kimbe Bay, Papua New Guinea, examine the hybrid status of Amphiprion leucokranos, a nominal species and presumed hybrid between Amphiprion sandaracinos and Amphiprion chrysopterus. We test the hypothesis that habitat use and relative size differences of the parent species and hybrids determine the patterns of gene exchange. There is strong evidence that A.leucokranos is a hybrid of smaller A.sandaracinos and larger A.chrysopterus, where A.chrysopterus is exclusively the mother to each hybrid, based on mtDNA cytochrome b and multiple nDNA microsatellite loci. Overlap in habitat, depth and host anemone use was found, with hybrids intermediate to parents and cohabitation in over 25% of anemones sampled. Hybrids, intermediate in body size, colour and pattern, were classified 55% of the time as morphologically first-generation hybrids relative to parents, whereas 45% of hybrids were more A.sandaracinos-like, suggesting backcrossing. Unidirectional introgression of A.chrysopterus mtDNA into A.sandaracinos via hybrid backcrosses was found, with larger female hybrids and small male A.sandaracinos mating. Potential nDNA introgression was also evident through distinct intermediate hybrid genotypes penetrating both parent species. Findings support the hypothesis that anemonefish hierarchical behaviour, habitat use and species-specific size differences determine how hybrids form and the evolutionary consequences of hybridization.

Habitat bleaching disrupts threat responses and persistence in anemonefish

Climate-induced habitat bleaching is linked to dramatic declines in diversity and abundance of coral reef fish; however, mechanisms underlying these declines are poorly understood. Here, we used in situ studies to demonstrate that bleaching can influence persistence of reef fish by affecting behaviours, including responses to a potential predation threat. When encountering the predatory rock cod Cephalophalis cyanostigma, anemonefish Amphiprion akindynos occupying healthy unbleached host anemones Heteractis crispa respond by feeding less and spending more time within the anemone tentacles. When the host anemone was experimentally bleached, these visual risk responses were compromised: A. akindynos continued to feed and did not seek shelter. The impaired behavioural response may prove detrimental to anemonefish populations as abundance levels of fish on bleached anemones was reduced by 60% within 3 d, which may have been the result of increased predation. Our data illustrate how climate-induced habitat degradation can drive declines of reef fish by potentially altering outcomes of predator–prey interactions.

Host specialist clownfishes are environmental niche generalists.

Why generalist and specialist species coexist in nature is a question that has interested evolutionary biologists for a long time. While the coexistence of specialists and generalists exploiting resources on a single ecological dimension has been theoretically and empirically explored, biological systems with multiple resource dimensions (e.g. trophic, ecological) are less well understood. Yet, such systems may provide an alternative to the classical theory of stable evolutionary coexistence of generalist and specialist species on a single resource dimension. We explore such systems and the potential trade-offs between different resource dimensions in clownfishes. All species of this iconic clade are obligate mutualists with sea anemones yet show interspecific variation in anemone host specificity. Moreover, clownfishes developed variable environmental specialization across their distribution. In this study, we test for the existence of a relationship between host-specificity (number of anemones associated with a clownfish species) and environmental-specificity (expressed as the size of the ecological niche breadth across climatic gradients). We find a negative correlation between host range and environmental specificities in temperature, salinity and pH, probably indicating a trade-off between both types of specialization forcing species to specialize only in a single direction. Trade-offs in a multi-dimensional resource space could be a novel way of explaining the coexistence of generalist and specialists.

Acclimation behaviour and bio-chemical changes during anemonefish (Amphiprion sebae) and sea anemone (Stichodactyla haddoni) symbiosis

Anemonefishes are known to exhibit an obligate symbiotic relationship with a limited number of sea anemone species. This has raised queries about the adaptive mechanisms of these fishes involved. The present study was carried out to understand the role of visual and chemical cues used for host recognition and the bio-chemical changes that occur during acclimation by the fishes. The experiments used the fishes Amphiprion sebae (a common anemone associate), Terapon jarbua (a control fish that does not associate with sea anemone) and Stichodactyla haddoni (an anemone commonly hosting anemonefishes). The results suggested that fish settlers use visual, tactile and chemical cues to select and distinguish their hosts. Furthermore, the acclimation times of A. sebae with the anemone host decreased exponentially during repeated trials. This fish apparently secreted a protective mucus. The epidermal mucus of A. sebae possessed unique glyco-proteins compared with T. jarbua. Chemical analyses showed that A. sebae and S. haddoni produced similar chemical substances, but T. jarbua produced a different kind of glycoprotein. This study helps to explain how anemonefishes are able to live with their host anemone, whereas other fishes are not.

Socio-economy of marine ornamental fishery and its impact on the population structure of the clown anemonefish Amphiprion ocellaris and its host anemones in Spermonde Archipelago, Indonesia

The clown anemonefish ‘Nemo’ Amphiprion ocellaris is the most popular fish species in the global marine ornamental trade and also its host sea anemones Heteractis magnifica, Stichodactyla gigantea, and Stichodactyla mertensii are traded. However, total catch and the potential impact of exploitation of these target organisms in Spermonde Archipelago, Indonesia, are not known. Therefore, the main objective of this study was to investigate the impact of the fishery on populations of A. ocellaris and its host anemones and how management could be improved. In order to obtain a comprehensive view on the marine ornamental fishery and trade of these species in Spermonde, this study also investigated the socioeconomics of the marine ornamental fishery and the catch records for A. ocellaris and it's host anemones. The study revealed that both, A. ocellaris and sea anemone densities were significantly lower at coral reefs with high exploitation (HE) than at reefs with low exploitation (LE). The total body length and group size of A. ocellaris was also significantly smaller at HE than at HL sites. The yearly amount traded by middlemen is estimated to 140 000 specimens of A. ocellaris and 31 000 anemones. The socioeconomic analysis showed that educational level of marine fishermen family members was low; most of them only finished elementary school. The household income analysis showed that marine ornamental fishery was not the major source of income, covering 13−43% of the expenses, with the exception of one studied island (84%). These findings revealed a considerable negative impact of marine ornamental fishery on the target populations and therefore, the implications for management strategies and conservation are discussed, including fish size restrictions for collectors, marine protected areas and regular monitoring of the amount of trade at middlemen.

Protection of host anemones by snapping shrimps: a case for symbiotic mutualism?

The sea anemone Bartholomea annulata is an ecologically important member of Caribbean coral reefs which host a variety of symbiotic crustacean associates. Crustacean exosymbionts typically gain protection from predation by dwelling with anemones. Concurrently, some symbionts may provide protection to their host by defending against anemone predators such as the predatory fireworm, Hermodice carunculata, which can severely damage or completely devour prey anemones. Herein we show through both field and laboratory studies that anemones hosting the symbiotic alpheid shrimp Alpheus armatus are significantly less likely to sustain damage by H. carunculata than anemones without this shrimp. Our results suggest that the association between A. armatus and B. annulata, although complex because of the numerous symbionts involved, may be closer to mutualism on the symbiotic continuum.

Searching for a toxic key to unlock the mystery of anemonefish and anemone symbiosis.

Twenty-six species of anemonefish of the genera Amphiprion and monospecific Premnas, use only 10 species of anemones as hosts in the wild (Families: Actiniidae, Stichodactylidae and Thalassianthidae). Of these 10 anemone species some are used by multiple species of anemonefish while others have only a single anemonefish symbiont. Past studies have explored the different patterns of usage between anemonefish species and anemone species; however the evolution of this relationship remains unknown and has been little studied over the past decade. Here we reopen the case, comparing the toxicity of crude venoms obtained from anemones that host anemonefish as a way to investigate why some anemone species are used as a host more than others. Specifically, for each anemone species we investigated acute toxicity using Artemia francisca (LC50), haemolytic toxicity using ovine erythrocytes (EC50) and neurotoxicity using shore crabs (Ozius truncatus). We found that haemolytic and neurotoxic activity varied among host anemone species. Generally anemone species that displayed greater haemolytic activity also displayed high neurotoxic activity and tend to be more toxic on average as indicated by acute lethality analysis. An overall venom toxicity ranking for each anemone species was compared with the number of anemonefish species that are known to associate with each anemone species in the wild. Interestingly, anemones with intermediate toxicity had the highest number of anemonefish associates, whereas anemones with either very low or very high toxicity had the fewest anemonefish associates. These data demonstrate that variation in toxicity among host anemone species may be important in the establishment and maintenance of anemonefish anemone symbiosis.

Embryonic learning of chemical cues via the parents' host in anemonefish (Amphiprion ocellaris)

The species-specific host-recognition system of anemonefish was examined experimentally, with a particular focus on the function of imprinting using naive Amphiprion ocellaris juveniles. Anemonefish parents lay their eggs very close to their host anemone so the eggs are almost always touched by the host's body or tentacles. Here, we demonstrate the embryonic and immediate post-hatching learning of chemical cues via the parents' host in A. ocellaris through a host-exchange experiment with egg batches during hatching. The memory obtained from such imprinting operates at the time when juveniles first search for their hosts. Unexpectedly, innate recognition was found to exist not only in the symbiotic host species but also weakly in two non-partner species. Innate recognition alone is not sufficient. Imprinting via the parents' host complements innate recognition, leading to rigid species-specific host recognition. Imprinting by the parents' single host provides a sufficient cue for reaching the two host species. Furthermore, when combined with imprinting, innate recognition of non-partners serves to supplement the recognition of those species, leading to substitute partnerships that are only observed in some localities. Potential functions of imprinting in the host-recognition system are discussed. The “spare recognition hypothesis” and the necessity of clear distinctions between symbiotic and substitute species are also proposed here.

The photo-physiological response of a model cnidarian–dinoflagellate symbiosis to CO2-induced acidification at the cellular level

We measured the relationship between CO2-induced seawater acidification, photo-physiological performance and intracellular pH (pHi) in a model cnidarian–dinoflagellate symbiosis – the sea anemone Aiptasia sp. – under ambient (289.94±12.54μatm), intermediate (687.40±25.10μatm) and high (1459.92±65.51μatm) CO2 conditions. These treatments represented current CO2 levels, in addition to CO2 stabilisation scenarios IV and VI provided by the Intergovernmental Panel on Climate Change (IPCC). Anemones were exposed to each treatment for two months and sampled at regular intervals. At each time-point we measured a series of physiological responses: maximum dark-adapted fluorescent yield of PSII (Fv/Fm), gross photosynthetic rate, respiration rate, symbiont population density, and light-adapted pHi of both the dinoflagellate symbiont and isolated host anemone cell. We observed increases in all but one photo-physiological parameter (Pgross:R ratio). At the cellular level, increases in light-adapted symbiont pHi were observed under both intermediate and high CO2 treatments, relative to control conditions (pHi 7.35 and 7.46 versus pHi 7.25, respectively). The response of light-adapted host pHi was more complex, however, with no change observed under the intermediate CO2 treatment, but a 0.3 pH-unit increase under the high CO2 treatment (pHi 7.19 and 7.48, respectively). This difference is likely a result of a disproportionate increase in photosynthesis relative to respiration at the higher CO2 concentration. Our results suggest that, rather than causing cellular acidosis, the addition of CO2 will enhance photosynthetic performance, enabling both the symbiont and host cell to withstand predicted ocean acidification scenarios.

North-eastern range extension of the anemone Stichodactyla haddoni to the Marshall Islands represents a new record of host use by the endemic anemonefish Amphiprion tricinctus

Amphiprion tricinctus is an anemonefish endemic to the Marshall Islands that was previously reported to inhabit four species of sea anemone. Underwater visual surveys in 2009 and 2010 located five individuals of the anemone Stichodactyla haddoni in the shallow lagoon of Majuro Atoll. This is the first record of S. haddoni in the Marshall Islands and a significant north-eastern range extension by 2200 km from its nearest record in Chuuk State, Federated States of Micronesia. Stichodactyla haddoni was inhabited by juvenile and adult A. tricinctus. This report is the first to describe a symbiotic relationship between A tricinctus and S. haddoni. The number of host anemone species inhabited by A. tricinctus now extends to five.

Fatty Acid and Phospholipid Syntheses Are Prerequisites for the Cell Cycle of Symbiodinium and Their Endosymbiosis within Sea Anemones

Lipids are a source of metabolic energy, as well as essential components of cellular membranes. Although they have been shown to be key players in the regulation of cell proliferation in various eukaryotes, including microalgae, their role in the cell cycle of cnidarian-dinoflagellate (genus Symbiodinium) endosymbioses remains to be elucidated. The present study examined the effects of a lipid synthesis inhibitor, cerulenin, on the cell cycle of both cultured Symbiodinium (clade B) and those engaged in an endosymbiotic association with the sea anemone Aiptasia pulchella. In the former, cerulenin exposure was found to inhibit free fatty acid (FFA) synthesis, as it does in other organisms. Additionally, while it also significantly inhibited the synthesis of phosphatidylethanolamine (PE), it did not affect the production of sterol ester (SE) or phosphatidylcholine (PC). Interestingly, cerulenin also significantly retarded cell division by arresting the cell cycles at the G0/G1 phase. Cerulenin-treated Symbiodinium were found to be taken up by anemone hosts at a significantly depressed quantity in comparison with control Symbiodinium. Furthermore, the uptake of cerulenin-treated Symbiodinium in host tentacles occurred much more slowly than in untreated controls. These results indicate that FFA and PE may play critical roles in the recognition, proliferation, and ultimately the success of endosymbiosis with anemones.

Taxonomic, Spatial and Temporal Patterns of Bleaching in Anemones Inhabited by Anemonefishes

BackgroundRising sea temperatures are causing significant destruction to coral reef ecosystems due to coral mortality from thermally-induced bleaching (loss of symbiotic algae and/or their photosynthetic pigments). Although bleaching has been intensively studied in corals, little is known about the causes and consequences of bleaching in other tropical symbiotic organisms.Methodology/Principal FindingsThis study used underwater visual surveys to investigate bleaching in the 10 species of anemones that host anemonefishes. Bleaching was confirmed in seven anemone species (with anecdotal reports of bleaching in the other three species) at 10 of 19 survey locations spanning the Indo-Pacific and Red Sea, indicating that anemone bleaching is taxonomically and geographically widespread. In total, bleaching was observed in 490 of the 13,896 surveyed anemones (3.5%); however, this percentage was much higher (19–100%) during five major bleaching events that were associated with periods of elevated water temperatures and coral bleaching. There was considerable spatial variation in anemone bleaching during most of these events, suggesting that certain sites and deeper waters might act as refuges. Susceptibility to bleaching varied between species, and in some species, bleaching caused reductions in size and abundance.Conclusions/SignificanceAnemones are long-lived with low natural mortality, which makes them particularly vulnerable to predicted increases in severity and frequency of bleaching events. Population viability will be severely compromised if anemones and their symbionts cannot acclimate or adapt to rising sea temperatures. Anemone bleaching also has negative effects to other species, particularly those that have an obligate relationship with anemones. These effects include reductions in abundance and reproductive output of anemonefishes. Therefore, the future of these iconic and commercially valuable coral reef fishes is inextricably linked to the ability of host anemones to cope with rising sea temperatures associated with climate change.

Influence of host anemone (Stichodactyla haddoni, saville-kent, 1893) locomotion on its resident anemonefish reproduction

Anemonefish are found commonly in reef habitats and they select only limited anemone species to exist their life. This study describes the movement of anemone, Stichodactyla haddoni and its impact on the reproduction of anemonefishes in captivity. The anemone movement was found to be creeping and in straight-line between successive positions (based on overlay mapping). The distance traveled by the host with (60%) and without substrate (20%) varied significantly (P<0.05) at a random direction. Spawning interval of the resident fish (3–4 days) increased significantly to 8–12 days (P<0.001) because of anemone mobility. Furthermore, host locomotion affected the embryonic development of harbored fish clutches. Percentage of egg maturity (3.5–35.3%) showed an exponential decrease with increase in the distance of substrate from the clutches, from 98 to 100% in the absence of host mobility to 3.5–35% with movement of >60cm. This study concludes that the sedentary habitat would enhance the reproduction value of the harbored fish. Further, in captivity providing with a substrate, supplying regular feed and good light intensity could prevent anemone migration and its implications on the reproductive success of the anemonefish.

Anemonefish oxygenate their anemone hosts at night

Anemonefish oxygenate their anemone hosts at night

Anemonefish oxygenate their anemone hosts at night

Many stony coral-dwelling fishes exhibit adaptations to deal with hypoxia among the branches of their hosts; however, no information exists on the respiratory ecophysiology of obligate fish associates of non-coral organisms such as sea anemones and sponges. This study investigated metabolic and behavioral interactions between two-band anemonefish (Amphiprion bicinctus) and bulb-tentacle sea anemones (Entacmaea quadricolor) at night. We measured the net dark oxygen uptake ( , μmol O2 h(-1)) of fish-anemone pairs when partners were separate from each other, together as a unit, and together as a unit but separated by a mesh screen that prevented physical contact. We also measured the effects of water current on sea anemone and quantified the nocturnal behaviors of fish in the absence and presence of host anemones in order to discern the impacts of anemone presence on fish behavior. Net of united pairs was significantly higher than that of both separated pairs and united pairs that were separated by a mesh screen. Anemone increased with flow rate from 0.5 to 2.0 cm s(-1), after which remained constant up to a water flow rate of 8.0 cm s(-1). Furthermore, the percentage time and bout frequency of flow-modulating behaviors by fish increased significantly when anemones were present. We conclude that physical contact between anemonefish and sea anemones elevates the of at least one of the partners at night, and anemonefish behavior at night appears to oxygenate sea anemone hosts and to augment the metabolism of both partners.

Measuring Body Size in Small Marine Fishes: A Comparison of Three Non-intrusive Methods

Studies of non-intrusive techniques are important in fisheries biology, because research methods may inadvertently cause damage to the study organisms. In addition, current effects of human–environment interactions coupled with future trends in global climate change likely will lead to increased monitoring of fish population dynamics. The aim of this study is to analyze the effectiveness of three simple non-intrusive techniques to accurately obtain body length measurements of anemonefish and other small fishes. Frequently used catch and re-capture methods are stressful to fishes, and can alter their behaviors upon release, thus negatively impacting field ecological studies. Alternate methods to non-intrusive sizing of reef fishes are needed, and these methods should be compared to determine the most effective and efficient means of collecting the targeted data. Three non-intrusive techniques were employed to obtain accurate fork length (FL) measurements of the two-band anemonefish, Amphiprion bicinctus. Comparison of these methods revealed that fish lengths from visual estimates by self-contained under water breathing apparatus (SCUBA) divers did not differ significantly from those estimated using both video-mirror and Tps-mirror techniques (ANOVA, F(2,60) 5 1.572; p 5 0.22). Under laboratory conditions, fish sizes from manual measurements also did not differ significantly from those obtained using either mirror method (ANOVA, F(2,81) 5 0.489; p 5 0.61), demonstrating that the mirror techniques accurately assess fish size under both laboratory and field conditions. These methods were not effective in identifying or tracking individual fish among years in the field, due to high rates of fish mobility and turnover. However, they were useful in determining short-term anemonefish migration among sea anemone host.

Host preference and habitat segregation among Red Sea anemonefish: effects of sea anemone traits and fish life stages

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 464:1-15 (2012) - DOI: https://doi.org/10.3354/meps09964 FEATURE ARTICLE Host preference and habitat segregation among Red Sea anemonefish: effects of sea anemone traits and fish life stages Lindsay K. Huebner1,*, Brianna Dailey1, Benjamin M. Titus1, Maroof Khalaf2, Nanette E. Chadwick1 1Department of Biological Sciences, Auburn University, Auburn, Alabama 36849, USA 2Department of Marine Biology, The University of Jordan-Aqaba, Aqaba 77110, Jordan *Email: lindsayhuebner@gmail.com ABSTRACT: Competition drives habitat segregation between adults and juveniles in many types of organisms, but little is known about this process in anemonefish that compete for host sea anemones which differ in habitat quality. We performed field and laboratory experiments to determine causes of habitat segregation in 2-band anemonefish Amphiprion bicinctus on coral reefs in the northern Red Sea, where juvenile fish mainly occupy leathery sea anemones Heteractis crispa, and breeding adults almost exclusively inhabit bulb-tentacle sea anemones Entacmaea quadricolor. E. quadricolor were usually larger than H. crispa, and expanded more in response to fish presence. Adult fish visually concealed a larger proportion of their body surface area among the relatively thick tentacles of E. quadricolor than among the thinner tentacles of H. crispa, while juveniles were concealed equally well in both hosts. During field experiments, vacated E. quadricolor were colonized rapidly by fish, whereas H. crispa were not. In laboratory choice experiments, fish at all post-settlement life stages preferred E. quadricolor, and large individuals monopolized this host and relegated subordinates to H. crispa. We conclude that competitive exclusion drives habitat segregation among life stages of this anemonefish and that host anemone traits underlie this process. The non-preferred host H. crispa may function as a refuge for juvenile fish while they wait for space to become available in the preferred host E. quadricolor, where they are able to attain sexual maturity. KEY WORDS: Intraspecific competition · Symbiosis · Amphiprion bicinctus · Entacmaea quadricolor · Heteractis crispa · Coral reef Full text in pdf format Information about this Feature Article NextCite this article as: Huebner LK, Dailey B, Titus BM, Khalaf M, Chadwick NE (2012) Host preference and habitat segregation among Red Sea anemonefish: effects of sea anemone traits and fish life stages. Mar Ecol Prog Ser 464:1-15. https://doi.org/10.3354/meps09964 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 464. Online publication date: September 19, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

SYMBIOTIC ALGAE DELIVER GLUCOSE TO ANEMONE HOST

Organisms that have struck up symbiotic relationships have found a wonderful quid pro quo lifestyle solution. For example, animal hosts provide essential nutrients and a safe refuge to their algal lodgers, while the algae provide a plentiful supply of energy harnessed by photosynthesis. ‘Most earlier studies had pointed to glycerol as being the primary photosynthetic metabolite [energy source] transferred from dinoflagellate algae to their cnidarian animal hosts’, explains John Pringle from Stanford University. However, other studies had suggested that symbionts may supply their hosts with alternative materials, such as photosynthetic glucose. Pringle, a yeast geneticist by trade, says that he was attracted to the problem because of his fascination with coral reefs. However, he recalls that when he began working on symbiosis he had no preconceptions about which materials the symbionts might deliver to their hosts. ‘When you change fields you look at everything with a sceptical eye’, he remembers. Teaming up with graduate student Matthew Burriesci, Pringle wanted to tackle the question of material transfer from a fresh – and softer – perspective. He decided to find out which materials the symbiotic anemone Aiptasia receives from its algal occupants (p. 3467).According to Pringle, symbiotic algae are remarkably robust, surviving separation from their host, and in the past, many researchers had measured the materials released by the isolated algae. Instead, Burriesci and Pringle supplied the intact anemone with heavy carbon dioxide – where the 12C atoms were replaced with 13C atoms – and allowed the algae, secure inside their symbiotic hosts, to photosynthesise for a day before separating the two. Then Burriesci and Theodore Raab analysed which materials in the host tissue had acquired the heavy carbon marker by isolating individual compounds with gas chromatography and identifying them by mass spectrometry.‘Glycerol does eventually appear in the host's body along with succinate, fumarate, various amino acids and other compounds’, recalls Pringle, adding that most host materials become labelled eventually if left for long enough. However, in order to find out which metabolic compound was being delivered directly to the host by its residents, Burriesci and Pringle realised that they would have to separate the symbiotic partners more quickly.Burriesci went off and designed and built a bespoke filter holder; ‘He did all the machining himself. I didn't know about it until after it was done,’ recalls Pringle, adding, ‘Then Matt could take an anemone sitting in a tank that had been provided with 13CO2, disrupt it, separate the mixture into an algal fraction and an animal cytoplasm fraction and then freeze them in liquid nitrogen, all within about two minutes’. Under the right conditions, this would allow the team to capture the first carbon compounds that the algae delivered to its anemone host after exposure to the heavy carbon dioxide.Switching the lights on for a few hours – to make sure that the algae were happily photosynthesising – before supplying the anemone with the heavy carbon dioxide, Burriesci swiftly separated the algae from the anemone 2–10 min later. Then he began analysing the animal tissue for any evidence of transfer of the heavy carbon from the photosynthesising algae to the anemone.‘The results were, to my eye, remarkably clear cut’, recalls Pringle. Mass spectral analysis showed that the only compound in the anemone tissue carrying the 13C signature was glucose. Instead of delivering glycerol to its host, the algae were supplying it with glucose. However, Pringle is quick to point out that this does not necessarily mean that all symbiotic algae provide glucose to their hosts, adding that they could deliver glycerol or other compounds under different circumstances.