The bearded fireworm <i>Hermodice carunculata</i> is an amphinomid stinging polychaete widespread in the Eastern Atlantic Ocean, and in the Central and Southern Mediterranean Sea. Whereas <i>H. carunculata</i> is a thermophilic species increasing in abundance along the Italian peninsula, very little information is available on its feeding habits, ecological functions and potential impacts on rocky benthic communities. The main goals of my PhD research activity were the investigation of fireworm sinecology, biogeography and chemical ecology. Laboratory feeding experiments were performed to investigate interactions between Mediterranean <i>H. carunculata</i> and species of sessile or sedentary marine invertebrates. Fireworms proved to be voracious generalist predators. Their predatory ability may be due to a combination of several 'weapons' (large size, motility, stinging chaetae and eversible, sucking pharynx), which seems unique among marine worms and could enable <i>H. carunculata</i> to persist also after radical changes in prey community composition and withstand selective pressures associated to ongoing environmental changes. Populations from South Italy were analyzed using allometric variables to assess the best morphometric parameters to estimate individual size. Regression analyses suggested the existence of significant relationships among allometric traits, a key information for future studies on fireworm population dynamics. Besides, demographic history analysis on molecular markers confirmed a recent expansion event in Apulia, as a crucial step forward in the study of present-day <i>H. carunculata</i> populations. An exhaustive collection of existing information on fireworm presence was examined to investigate the spatiotemporal changes that have occurred in <i>H. carunculata</i> abundances and distribution along the Italian coasts so far. The integration of different data sources allowed the reconstruction of the shifts that have happened over the last 50 years, which are coherent with the consistent warming trend of Mediterranean Sea surface temperatures. These findings provide unique insights into the expansion of <i>H. carunculata</i>, supporting future spreading throughout the Northern and Western Mediterranean. Amphinomid fireworms are notorious for their stinging dorsal bristles (notochaetae), but if the cause of the irritation is merely mechanical or chemical is still unclear. Besides, chaetae composition has not been investigated to date and strong debates are ongoing on their internal structure. The chemical and mineralogical composition, the ultrastructure and the external structure of <i>H. carunculata</i> chaetae were examined for the first time. SEM micrographs showed that the notochaetae are hollow and may be able to vehicle toxins. To determine whether and where chemical or structural deterrents were present, different <i>H. carunculata</i> body parts involved in inter-specific interactions were tested. Feeding bioassays were performed to assess palatability against generalist consumers and deterrent action on contact with fireworm prey. The results highlighted that only the notochaetae display deterrent activity. To date, the only acute inflammation inducer isolated from an amphinomid is “complanine”, a trimethylammonium compound. High-resolution LC-MS/MS and NMR analyses suggested the presence of complanine-related compounds in all fireworm body parts and in other polychaetes, but in a far lesser extent, while they seem absent in cnidarians, mollusks, echinoderms and tunicates. The urticating system of fireworms is triggered by a synergy between mechanical injury and venom release. This unique feature could support the success of fireworms in marine benthic environments and significantly improves knowledge on the chemical ecology of amphinomids.

Il verme di fuoco <i>Hermodice carunculata</i> è un polichete anfinomide urticante diffuso nell’Oceano Atlantico orientale e nel Mediterraneo centrale e meridionale. Sebbene <i>H. carunculata</i> sia una specie termofila in aumento lungo le coste italiane, le informazioni disponibili su abitudini alimentari, ruolo ecologico e potenziali impatti sulle comunità bentoniche rocciose sono molto limitate. I principali obiettivi delle mie ricerche di Dottorato hanno riguardato lo studio della sinecologia, biogeografia ed ecologia chimica dei vermi di fuoco. Sono stati svolti esperimenti di predazione in laboratorio per investigare le interazioni tra esemplari mediterranei di <i>H. carunculata</i> ed altri invertebrati marini sessili o sedentari. I vermi di fuoco si sono rivelati predatori generalisti efficienti. Le loro capacità potrebbero essere dovute ad una combinazione di “armi” (dimensioni cospicue, chete urticanti e faringe estroflettibile succhiante), che sembrano uniche tra gli anellidi marini, e permetterebbero ad <i>H. carunculata</i> di far fronte a cambiamenti nella composizione delle comunità di prede e pressioni selettive dovute ai cambiamenti climatici in atto. Per valutare i migliori parametri morfometrici atti a stimare la taglia individuale dei vermi di fuoco, sono state analizzate variabili allometriche di popolazioni del sud Italia. Le analisi della regressione hanno suggerito l’esistenza di relazioni significative tra tratti allometrici, un dato chiave per studi futuri sulle dinamiche di popolazione. Inoltre, analisi di demografia storica su marcatori molecolari hanno confermato un recente evento di espansione in Puglia, incentivando ulteriori studi sulle popolazioni attuali di <i>H. carunculata</i>. Le informazioni esistenti sulla presenza dei vermi di fuoco sono state raccolte per capire i cambiamenti spazio-temporali avvenuti finora lungo le coste italiane. L’integrazione di diverse fonti ha permesso di ricostruire gli shifts verificatisi negli ultimi 50 anni, coerenti con il trend di aumento delle temperature superficiali del Mediterraneo. Questi risultati forniscono importanti conoscenze sull’espansione di <i>H. carunculata</i>, supportando una futura diffusione verso il Mediterraneo settentrionale ed occidentale. Gli anfinomidi sono famosi per le loro chete dorsali urticanti (notochete), ma non è ancora chiaro se la causa dell’irritazione sia meccanica o chimica. Inoltre, la composizione delle chete non è stata studiata finora e forti dibattiti sono in corso sulla loro struttura interna. La composizione chimica e mineralogica, l’ultrastruttura e la struttura esterna delle chete di <i>H. carunculata</i> sono state esaminate. Al SEM, le notochete risultano cave e potrebbero veicolare tossine. Per determinare la presenza e localizzazione di sostanze deterrenti, sono state testate diverse parti del corpo di <i>H. carunculata</i> coinvolte in interazioni inter-specifiche. Mediante feeding bioassays, sono state valutate palatabilità verso un consumatore generalista ed azione deterrente al contatto con prede dei vermi di fuoco. I risultati hanno evidenziato che solo le notochete sono deterrenti. Ad oggi, l’unica sostanza infiammatoria isolata da un anfinomide è la “complanina”, un composto trimetil-ammonio. Analisi LC-MS/MS ad alta risoluzione ed NMR hanno suggerito la presenza di composti correlati alla complanina in tutti i distretti corporei dei vermi di fuoco ed in misura molto minore in altri policheti, mentre sembrano assenti in cnidari, molluschi, echinodermi e tunicati. Alla base dell’irritazione provocata dai vermi di fuoco vi è una sinergia tra danno meccanico e rilascio di un veleno. Questa peculiarità supporterebbe il successo dei vermi di fuoco negli ambienti bentonici marini, migliorando notevolmente le conoscenze sull’ecologia chimica degli anfinomidi.

Ecologia e capacità difensive-offensive del verme di fuoco Mediterraneo Hermodice carunculata (Annelida), una specie in espansione / Sara Righi , 2021 Apr 12. 33. ciclo, Anno Accademico 2019/2020.

Ecologia e capacità difensive-offensive del verme di fuoco Mediterraneo Hermodice carunculata (Annelida), una specie in espansione

RIGHI, SARA
2021

Abstract

The bearded fireworm Hermodice carunculata is an amphinomid stinging polychaete widespread in the Eastern Atlantic Ocean, and in the Central and Southern Mediterranean Sea. Whereas H. carunculata is a thermophilic species increasing in abundance along the Italian peninsula, very little information is available on its feeding habits, ecological functions and potential impacts on rocky benthic communities. The main goals of my PhD research activity were the investigation of fireworm sinecology, biogeography and chemical ecology. Laboratory feeding experiments were performed to investigate interactions between Mediterranean H. carunculata and species of sessile or sedentary marine invertebrates. Fireworms proved to be voracious generalist predators. Their predatory ability may be due to a combination of several 'weapons' (large size, motility, stinging chaetae and eversible, sucking pharynx), which seems unique among marine worms and could enable H. carunculata to persist also after radical changes in prey community composition and withstand selective pressures associated to ongoing environmental changes. Populations from South Italy were analyzed using allometric variables to assess the best morphometric parameters to estimate individual size. Regression analyses suggested the existence of significant relationships among allometric traits, a key information for future studies on fireworm population dynamics. Besides, demographic history analysis on molecular markers confirmed a recent expansion event in Apulia, as a crucial step forward in the study of present-day H. carunculata populations. An exhaustive collection of existing information on fireworm presence was examined to investigate the spatiotemporal changes that have occurred in H. carunculata abundances and distribution along the Italian coasts so far. The integration of different data sources allowed the reconstruction of the shifts that have happened over the last 50 years, which are coherent with the consistent warming trend of Mediterranean Sea surface temperatures. These findings provide unique insights into the expansion of H. carunculata, supporting future spreading throughout the Northern and Western Mediterranean. Amphinomid fireworms are notorious for their stinging dorsal bristles (notochaetae), but if the cause of the irritation is merely mechanical or chemical is still unclear. Besides, chaetae composition has not been investigated to date and strong debates are ongoing on their internal structure. The chemical and mineralogical composition, the ultrastructure and the external structure of H. carunculata chaetae were examined for the first time. SEM micrographs showed that the notochaetae are hollow and may be able to vehicle toxins. To determine whether and where chemical or structural deterrents were present, different H. carunculata body parts involved in inter-specific interactions were tested. Feeding bioassays were performed to assess palatability against generalist consumers and deterrent action on contact with fireworm prey. The results highlighted that only the notochaetae display deterrent activity. To date, the only acute inflammation inducer isolated from an amphinomid is “complanine”, a trimethylammonium compound. High-resolution LC-MS/MS and NMR analyses suggested the presence of complanine-related compounds in all fireworm body parts and in other polychaetes, but in a far lesser extent, while they seem absent in cnidarians, mollusks, echinoderms and tunicates. The urticating system of fireworms is triggered by a synergy between mechanical injury and venom release. This unique feature could support the success of fireworms in marine benthic environments and significantly improves knowledge on the chemical ecology of amphinomids.
Ecology and physico-chemical weapons of the Mediterranean range-expanding fireworm Hermodice carunculata (Annelida)
12-apr-2021
SIMONINI, Roberto
PREVEDELLI, Daniela
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