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Phyllodiscus semoni at South Sulawesi. Extended tentacles and pseudotentacles with vesicles (arrows) in a branched morphotype (A) and a smooth disc (B), West side Bone Baku reef, Spermonde Archipelago, May 1997.
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Phyllodiscus semoni is a morphologically variable sea anemone species from the Indo-Pacific with morphotypes ranging from upright and branched to low-lying and rounded. The apparent camouflage strategies of this sea anemone allow it to resemble other species or objects in its environment, such as stony corals, soft corals, seaweeds, or rocky boulde...
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Context 1
... outgrowths of the column called pseudotentacles. The pseudotentacles provide increased surface area to house and display zooxanthellae to the sun, therefore provid- ing maximum exposure to light for photosynthesis. During the day, the pseudotentacles are expanded, while at night the tentacles on the oral disc are expand- ed (Gladfelter, 1975; Fig. 9). Multiple pseudotentacles occur per Phyllodiscus, extending out from two-thirds of the column (the very top and bottom of the column are free from pseudotentacles). These outgrowths can be branched in various directions and to various de- grees, thereby creating variation in pseudotentacle morphology, and therefore the different ...
Context 2
... more radial symmetry in their body plan (Figs 3-8) and having a body surface that is fluffier. By being softer, their body moves more in turbulent water. After aggravation, specimens extend the col- umn and oral disc with mouth and tentacles, while globular vesicles remain visible on the pseudotenta- cles of the main body around the column (Fig. 9). These vesicles are small bubble-like bumps of which the ectoderm is dense with nematocysts. Compared to sea anemones of Actinodendridae (which they have been confused with), Phyllodiscus individuals are sedentary by having a distinct pedal disc that at- taches to a hard substrate, while actinodendrids bur- row into soft sediment. ...
Citations
... This is undoubtedly due to the difficulty of recognising individuals of this species on the seabed, as they skillfully imitate representatives of other groups of marine benthos in appearance. Special works are devoted to this remarkable peculiarity (Hoeksema & Crowther, 2011;Meij et al., 2018). The venom found in the body of this species has been examined in numerous biochemical studies (Nagai et al., 2002a(Nagai et al., , 2002bUechi et al., 2005aUechi et al., , 2005bUechi et al., , 2010Uechi et al., , 2011Satoh et al., 2007;Frazão et al., 2012;Ashwood et al., 2021). ...
... semoni. Hoeksema & Crowther (2011) emphasise this point, referring to some photographs included in these papers. Additionally, we would like to note that the high similarity of amino acid sequences of toxins (Satoh et al., 2007) isolated from samples attributed to A. villosa and those reliably belonging to Ph. semoni suggests that all Japanese specimens belong to the latter species. ...
... Due to the presence of unusual, variously arranged outgrowths on the column wall, large polyps of Ph. semoni closely resemble other common reef inhabitants, such as branched calcareous colonies of scleractinian corals and bryozoans, which are unattractive to most predators. Hoeksema & Crowther (2011) explain the remarkable appearance of these anemones as a form of mimicry. ...
Phyllodiscus semoni Kwietniewski, 1897, a little-known species of sea anemones of the family Aliciidae, is quite widely distributed in the tropics but has not been recorded from the Spratly Islands so far. The reason that the range of this species is poorly studied lies not only in the fact that many tropical areas are still poorly explored but also in the peculiar appearance of this animal in the sea. It rarely extends its tentacles during daylight hours and is not readily recognised by divers and researchers as an actinian. Our underwater observations, accompanied by high-resolution photography and specimen collection, evidence the presence of this species along the continental coast of Vietnam and in the waters of the Spratly Archipelago. During the dives, some observations were made on the behavior of the polyps and symbiotic shrimp living on their bodies. This species of sea anemones can cause severe skin burns in humans, which is confirmed by our experience. Summarised literature data on the distribution of Ph. semoni is provided.
... Stings of some tropical shallow-water species from the Indo-West Pacific region may leave severe, long-lasting scars on their human victims, or in some instances, cause death (Erhardt and Knop 2005). Amongst species from the region that harbour potent stings, and are a threat to public health, four are well-known: Dofleinia armata Wassilief, 1908, Phyllodiscus semoni Kwietniewski, 1897, and members of the family Actinodendridae Haddon, 1898 such as Actinodendrum arboreum (Quoy and Gaimard, 1833) and Actinostephanus haeckeli Kwietniewski, 1897(see: Coleman 1999Hoeksema and Crowther 2011;Mizuno et al. 2007;Rowlett 2020). ...
... Dolfeinia armata is another, similar example: it bears visible nematocyst batteries on its tentacles, and have basitrichs that are > 50 µm (e.g., up to 76 µm; see Carlgren 1945). Other sea anemones that have been reported to be a threat to public health, such as Phyllodiscus semoni and members of Actinodendridae also bear specialised structures along their tentacles that harbour a dense reservoir of nematocysts (e.g., nematocyst batteries) and cnidae larger in size (for sizes, see Carlgren 1945;Fautin et al. 2009;Hoeksema and Crowther 2011). Following this line of logic, we suggest that sea anemone species that may inflict painful stings are ones that usually bear specialised structures on their tentacles, and/or have large nematocysts; M. aspera may also be a potential threat to humans. ...
Sea anemones (Cnidaria, Actiniaria) are a successful group of marine invertebrates found in a diverse range of environments globally. In spite of their ubiquity, identities for many sea anemones remain unverified, especially those from the Indo-West Pacific region. Here, we clarify the taxonomy of the poorlynknown Macrodactyla aspera, a shallow-water species first described from the Torres Straits in northern
Australia. We re-describe M. aspera based on new morphological and molecular data gathered from the type specimen, other museum vouchers, and from fresh material collected from Singapore. We tested the monophyly of Macrodactyla using three mitochondrial (12S, 16S and cox3) and one nuclear (28S) marker
based on three congeners, recovering this genus to be polyphyletic. As a consequence, we transferred M. doreensis to the genus Heteractis, and describe a new species, Macrodactyla fautinae sp. nov. While both M. aspera and M. fautinae sp. nov. share the same arrangement and number of complete mesenteries, a
similar distribution of cnidae, and are not symbiotically associated with any other biota, M. fautinae sp. nov. has perforated, lobe-like verrucae on its column, and lacks nematocyst batteries on its tentacles, unlike M. aspera. These two species also occur in similar habitats in Singapore. Finally, because M. aspera strongly
resembles Dofleinia armata, the latter species flagged as a danger to public health due to its ability to inflict painful stings, we tested the relationship between these species and found them not to be closely related. However, tentacles of M. aspera, like D. armata, are densely covered with nematocyst batteries and harbour large nematocysts; we infer that M. aspera may also be capable of delivering stings that
endanger public health. This study builds upon a growing number of studies that aim to ascertain identities and systematics of sea anemones historically reported from the Indo-West Pacific. Our findings will facilitate accurate species identification, which is crucial for advancing research, formulating conservation measures, and protecting public health.
... Phyllodiscus semoni is widespread in the Central Indo-West Pacific to the East China Sea. 6 There are few reports of patients seeking hospitals on the day of injury, and most patients seem to consult doctors in urban areas who are relatively unfamiliar to tropical medicine, therefore, making it difficult to establish an accurate diagnosis. 3,4 The organism also changes its appearance in a variety of ways to suit its surroundings. ...
... 3,4 The organism also changes its appearance in a variety of ways to suit its surroundings. 6 Therefore, information on the shape of what it touches is not always useful. As contact with Phyllodiscus semoni can lead to acute renal failure without any vital sign changes, it is necessary to check the renal function if a characteristic skin rash is observed. ...
... Vesicles in Phyllodiscus semoni are comparably nematocyst-dense spherical structures attached to the pseudotentacles (Figure 1g,h) [26]. Pseudotentacles are restricted to the family Aliciidae and differ from true tentacles in that they are outgrowths of the lower column wall [26,35]. Tentacles and pseudotentacles alternate, extending and retracting in a cyclic manner, with pseudotentacles extending and obscuring the true tentacles during the day [35,36]. ...
... Pseudotentacles are restricted to the family Aliciidae and differ from true tentacles in that they are outgrowths of the lower column wall [26,35]. Tentacles and pseudotentacles alternate, extending and retracting in a cyclic manner, with pseudotentacles extending and obscuring the true tentacles during the day [35,36]. The alternating retraction of pseudotentacles and tentacles implies that these structures have specific functions, which may require different venom compositions, resulting in differential expression of toxins across these morphological features. ...
... Similarly, vesicles and pseudotentacles in species from Aliciidae are predicted to have a major role in predator deterrence. During the day, tentacles are retracted in P. semoni and offer no protection against predators [35,36]. Conversely, vesicles and pseudotentacles extend in response to light exposure, obscuring the retracted tentacles [36], and therefore these are the structures that predators are most likely to come into contact with. ...
Phylum Cnidaria is an ancient venomous group defined by the presence of cnidae, specialised organelles that serve as venom delivery systems. The distribution of cnidae across the body plan is linked to regionalisation of venom production, with tissue-specific venom composition observed in multiple actiniarian species. In this study, we assess whether morphological variants of tentacles are associated with distinct toxin expression profiles and investigate the functional significance of specialised tentacular structures. Using five sea anemone species, we analysed differential expression of toxin-like transcripts and found that expression levels differ significantly across tentacular structures when substantial morphological variation is present. Therefore, the differential expression of toxin genes is associated with morphological variation of tentacular structures in a tissue-specific manner. Furthermore, the unique toxin profile of spherical tentacular structures in families Aliciidae and Thalassianthidae indicate that vesicles and nematospheres may function to protect branched structures that host a large number of photosynthetic symbionts. Thus, hosting zooxanthellae may account for the tentacle-specific toxin expression profiles observed in the current study. Overall, specialised tentacular structures serve unique ecological roles and, in order to fulfil their functions, they possess distinct venom cocktails.
... Likewise, synonymies are generally justified through the demonstration of identity in these visible features. Although these data are certainly relevant for species delimitation in hexacorallian cnidarians, ecophenotypic variation can be very high (e.g., Hoeksema & Crowther 2011), and phylogenetic analyses have repeatedly highlighted the plasticity and high levels of convergence of key features in sea anemones (González-Muñoz et al., 2015;Rodríguez et al., 2012Rodríguez et al., , 2014Grajales & Rodríguez 2016;Daly et al. 2017;Gusmão et al. 2020) and other anthozoans (e.g., Bo et al., 2018;Budd et al., 2010;Cachet et al., 2015;Sánchez et al., 2003). This has cast doubt on the effectiveness of morphological characters as the arbiter of species boundaries within this lineage. ...
Genome-level sequencing is the next step in understanding species-level relationships within Anthozoa (soft corals, anemones, stony corals, and their kin) as morphological and PCR-directed (single-locus) sequencing methods often fall short of differentiating species. The sea anemone genus Metridium is a common northern temperate sea anemone whose species are difficult to differentiate using morphology alone. Here we use Metridium as a case study to confirm the low level of information available in six loci for species differentiation commonly sequenced for Actiniaria and explore and compare the efficacy of ddRAD and sequence-capture methods in species-level systematics and biogeographic studies. We produce phylogenetic trees from concatenated datasets and perform DAPC and STRUCTURE analyses using SNP data. The six conventional loci are not able to consistently differentiate species within Metridium. The sequence-capture dataset resulted in high support and resolution for both current species and relationships between geographic areas. The ddRAD datasets displayed ambiguity among species, and support between major geographic groupings was not as high as the sequence-capture datasets. The level of resolution and support resulting from the sequence-capture data, combined with the ability to add additional individuals and expand beyond the genus Metridium over time, emphasizes the utility of sequence-capture methods for both systematics and future biogeographic studies within anthozoans. We discuss the strengths and weaknesses of the genomic approaches in light of our findings and suggest potential implications for the biogeography of Metridium based on our sampling.
... This species is a master of camouflage and mimicry, not only in colour and pattern, but also in shape and form. Many morphotypes have been recorded for this species including morphs resembling dead coral rock, soft and stony corals, and algae (Hoeksema and Crowther, 2011). The large variety in morphotypes complicates identification of this species, and records of P. semoni are still rather sparse (Den Hartog, 1997;Hoeksema and Crowther, 2011). ...
... Many morphotypes have been recorded for this species including morphs resembling dead coral rock, soft and stony corals, and algae (Hoeksema and Crowther, 2011). The large variety in morphotypes complicates identification of this species, and records of P. semoni are still rather sparse (Den Hartog, 1997;Hoeksema and Crowther, 2011). Information about the regional occurrence of this species is important; Phyllodiscus possess some of the most dangerous venoms for humans. ...
... Known records of P. semoni in the Indo-West Pacific include: Ari Atoll in the Maldives (Erhardt and Knop, 2005), various locations in the Philippines (Gosliner et al., 1996) and Indonesia (Gosliner et al., 1996;Den Hartog, 1997;Coleman, 2000;Erhardt and Knop, 2005;Hoeksema and Crowther, 2011), Milne Bay in Papua New Guinea (Halstead, 2000), Okinawa in Japan (Mizuno et al., 2007) off Townsville in Australia (Shick et al., 1991), and New Caledonia (Laboute and de Forges, 2004;listed as Alicia rhadina Haddon and Shackleton, 1893). In addition there is a possible record from southern Vietnam (see discussion in Hoeksema and Crowther, 2011). ...
The stinging sea anemone Phyllodiscus semoni is recorded from Malaysia for the first time. This species exhibits high morphological variation, and morphotypes resembling dead coral rock, soft and stony
corals and algae have been documented. Correct identification and information on local occurrences of Phyllodiscus is important, since this species is armed with venom-laden nematocysts that are hazardous to humans. In situ photographs of the specimens encountered in Malaysian Borneo are provided and their morphotypes are discussed.
... It was reported that P. semoni could have a variety of polymorphic types since it mimics the neighboring background environment, and it was previously thought to unlikely be a single species. For example, one of Clinical Toxinology DOI 10.1007/978-94-007-6288-6_64-2 # Springer Science+Business Media B.V. 2018 P. semoni's camouflage strategies is to mimic the shape of Seriatopora caliendrum when it grows with dead, hard coral (Hoeksema and Crowther 2011). ...
... Another highly toxic sea anemone in Okinawan waters, A. villosa was originally reported by Quey and Gaimard in the early 1800s, as shown in a report by Fautin et al. (2007). A. villosa also mimics its surroundings and is closely related to P. semoni, and therefore the two species are easily confused and have even been thought to be the same species (Hoeksema and Crowther 2011). However, A. villosa was determined by Oshiro et al. in 2001 to be a distinct species from P. semoni (Oshiro et al. 2001). ...
... Venom extracted from A. villosa was identified by Uechi et al. in 2005Uechi et al. (2005a, 2005b. As mentioned above, P. semoni and A. villosa can be easily confused; therefore, future work associated with A. villosa toxin should be careful to distinguish the two species, as mentioned by Hoeksema et al. (Hoeksema and Crowther 2011). Severe Dermatitis and AKI Caused by P. semoni P. semoni is an extremely harmful sea anemone belonging to the family Aliciidae. ...
... It was reported that P. semoni could have a variety of polymorphic types since it mimics the neighboring background environment, and it was previously thought to unlikely be a single species. For example, one of Clinical Toxinology DOI 10.1007/978-94-007-6288-6_64-2 # Springer Science+Business Media B.V. 2018 P. semoni's camouflage strategies is to mimic the shape of Seriatopora caliendrum when it grows with dead, hard coral (Hoeksema and Crowther 2011). ...
... Another highly toxic sea anemone in Okinawan waters, A. villosa was originally reported by Quey and Gaimard in the early 1800s, as shown in a report by Fautin et al. (2007). A. villosa also mimics its surroundings and is closely related to P. semoni, and therefore the two species are easily confused and have even been thought to be the same species (Hoeksema and Crowther 2011). However, A. villosa was determined by Oshiro et al. in 2001 to be a distinct species from P. semoni (Oshiro et al. 2001). ...
... Venom extracted from A. villosa was identified by Uechi et al. in 2005Uechi et al. (2005a, 2005b. As mentioned above, P. semoni and A. villosa can be easily confused; therefore, future work associated with A. villosa toxin should be careful to distinguish the two species, as mentioned by Hoeksema et al. (Hoeksema and Crowther 2011). Severe Dermatitis and AKI Caused by P. semoni P. semoni is an extremely harmful sea anemone belonging to the family Aliciidae. ...
... P ID between siblings ranged from 4.5 × 10 −6 in E. quadricolor at Magna to 1.9 × 10 −2 in H. magnifica at Kimbe Island. Sea anemones are known to have the ability to reproduce asexually (Billingham and Ayre 1996;Bocharova and Kozevich 2011), which can result in large aggregations of similarly shaped morphotypes (Hoeksema and Crowther 2011). Since all four microsatellite panels described in this work can yield low P ID s, they represent an adequate tool to identify clones within populations of these organisms. ...
Relatively few studies have investigated the genetic population structure of sea anemones. This is particularly true for sea anemones that host some of the most iconic fishes on coral reefs, the anemonefishes. One of the main reasons for this knowledge gap is the lack of appropriate genetic markers. We developed and characterized a total of 47 novel polymorphic microsatellite markers for four host sea anemone species from the Indo-Pacific: Entacmaea quadricolor (n =16micro- satellite markers), Heteractis magnifica (n =8), Stichodactyla mertensii (n =13), and Stichodactyla gigantea (n = 10). Here, we report genetic diversity statistics from two different sampling locations for each anemone species. Overall, we found that most markers were highly polymorphic. On average, we found a mean of seven alleles per locus.Observed and expected heterozygosities displayed high variation among loci, ranging from 0.033 to 0.980 and from0.038 to 0.927, respectively. Only four loci showed deviations of Hardy–Weinberg equilibrium in both populations and were identified as having null alleles. Additionally, two pairs of loci were identified to be in linkage disequilibrium in only one population. Host anemones are highly sought after in the marine aquarium trade and are susceptible to thermal bleaching. Although most studies focus on their obligate symbionts (the anemonefish), genetic analyses of host sea anemones can expand our understanding of the biology, connectivity, and population structure of these organisms and potentially help develop conservation strategies that will aid both the host and its symbionts.
... Fortunately, only a few case reports describing AKI in patients stung by sea anemones have been reported to date. In one case, a patient developed AKI with severe acute tubular necrosis after contact with P. semoni (Mizuno et al. 2000 ) which can be diffi cult to identify because it can be resemble other organisms under some circumstances (Hoeksema and Crowther 2011 ). In this case, direct nephrotoxicity of the venom was considered to be responsible as there was no evidence of organ failure or a state of shock. ...
Natural toxins are among the most important causes of acute kidney injury in humans. Several marine animals produce toxins that are nephrotoxic for humans. Cnidarians produce toxins in nematocysts that offer protection from potential enemies and are used in feeding. Envenomation by these toxins through stings can be toxic for humans, with injuries typically comprising skin eruptions and ulcers. However, the stings of several species induce more severe symptoms such as shock syndromes and organ failure, particularly renal failure. Here I summarize the current state of knowledge concerning renal injuries resulting from envenomation by coelenterates and describe the expected mechanisms, possibilities for therapeutic approaches, and strategies for preventing human diseases in future.
