The family Stylasteridae Gray 1847 is one of 112 families of hydrozoans belonging to the phylum Cnidaria, which to date includes 328 species and 33 genera distributed throughout the world, except for the Arctic. Stylasterids, commonly known as 'lace corals', are colonial benthic organisms that require a hard substrate on which to settle and grow. They have a calcareous skeleton, called coenosteum, and polymorphic colonies represented by two different types of polyps: gastrozoids and dactylozoids. Stylasterids play an important ecological role. In fact, in many environments, they are considered habitat-forming species because, thanks to the three-dimensional structure of their calcareous skeleton, they contribute to habitat complexity, creating refuges for a variety of organisms, such as sponges. However, in the literature, information on Stylasteridae and their epibionts is relatively scarce. The main aim of this work was to make a contribution to enriching knowledge on the taxonomy and ecology of these organisms. The analyses were based on the observation of multiple samples of different Stylasteridae species and their epibionts, mainly sponges, sampled in Antarctica. 6 Sampling was conducted in the Ross Sea at 12 sites during the XXXII Antarctic campaign, between January and February 2017, using an epibenthic sled and a box corer, at depths between 432 and 1022 metres. Samples of stylasterids, already dead at the time of sampling, and associated sponges, were then treated with hydrogen peroxide (35%) and nitric and sulphuric acid, respectively, and subsequently identified to the lowest possible taxonomic level through scanning electron microscope (SEM), stereomicroscope and light microscope observations. The taxonomic study of the collected specimens led to the identification of four species of stylasterids: Errina fissurata (Gray, 1872), Errina laterorifa Eguchi, 1964, Errina (Errina) gracilis von Marenzeller, 1903 and Inferiolabiata labiata (Moseley, 1879), and 38 species of sponges, of which 9 are probably new species, belonging to two classes of porifers, Demospongiae Sollas, 1885 and Hexactinellida Schmidt, 1870. Through comparisons with literature data, it has emerged that our data concerning the geographical distribution of the identified stylasterid species confirm those already observed by other authors, while as far as sponges are concerned, it is hypothesised that stylasterid beds are not the ideal secondary substrate for them as they do not represent a living or elevated substrate, but in 7 lack of data in this respect, further studies are needed to confirm our hypotheses. In conclusion, the present study shows how little Antarctic benthic communities are studied and how little is still known about the relationships between organisms in the Antarctic Ocean. In the near future, an increased sampling effort and more in-depth studies should be conducted in synergy in order to support the hypothesis that the Southern Ocean represents a biodiversity hot-spot.
La famiglia Stylasteridae Gray 1847 è una delle 112 famiglie di idrozoi appartenenti al phylum Cnidaria, che ad oggi include 328 specie e 33 generi distribuiti in tutto il mondo, fatta eccezione per l’Artico. Gli stylasteridi, comunemente conosciuti come “lace corals”, sono organismi bentonici coloniali che necessitano di un substrato duro su cui stabilirsi e svilupparsi. Presentano uno scheletro calcareo, chiamato cenosteo, e colonie polimorfiche rappresentate da due differenti tipi di polipi: gastrozoidi e dattilozoidi. Gli stylasteridi presentano un importante ruolo ecologico. Infatti, in molti ambienti, sono considerati specie strutturanti (habitat-formers) in quanto, grazie alla struttura tridimensionale del loro scheletro calcareo, contribuiscono ad aumentare la complessità dell'habitat, creando rifugi per una varietà di organismi, come ad esempio le spugne. Tuttavia, in letteratura, le informazioni sugli Stylasteridae e i loro epibionti sono relativamente scarse. Scopo principale di questo lavoro è stato quello di dare un contributo per arricchire le conoscenze sulla tassonomia e l'ecologia di questi organismi. Le analisi si sono basate sull'osservazione di molteplici campioni di diverse specie di stylasteridi e dei loro epibionti, principalmente spugne, campionati in Antartide. 6 I campionamenti sono stati condotti nel Mare di Ross in 12 siti durante la XXXII campagna Antartica, tra Gennaio e Febbraio 2017, mediante l'utilizzo di una slitta epibentonica e un box corer, a profondità comprese tra i 432 e 1022 metri. I campioni di stylasteridi, già morti al momento del campionamento, e di spugne ad essi associate, sono stati poi trattati rispettivamente con perossido di idrogeno (35%) e acido nitrico e solforico, e successivamente identificati al minor livello tassonomico possibile attraverso osservazioni al miscroscopio elettronico a scansione (SEM), stereomicroscopio e microscopio ottico. Lo studio tassonomico dei campioni raccolti ha condotto all’identificazione di quattro specie di stylasteridi: Errina fissurata (Gray, 1872), Errina laterorifa Eguchi, 1964, Errina (Errina) gracilis von Marenzeller, 1903 e Inferiolabiata labiata (Moseley, 1879), e a 38 specie di spugne, di cui 9 probabilmente sono nuove specie, appartenenti a due classi di poriferi, Demospongiae Sollas, 1885 ed Hexactinellida Schmidt, 1870. Attraverso confronti con dati di letteratura, è emerso che i nostri dati relativi alla distribuzione geografica delle specie di stylasteridi identificate, confermano quelle già osservate da altri autori, mentre per ciò che concerne le spugne, si ipotizza che i letti di stylasteridi, non siano il substrato secondario ideale per loro in quanto non rappresentano un substrato vivo o elevato, ma in 7 carenza di dati a riguardo, ulteriori studi necessitano per confermare le nostre ipotesi. In conclusione, il presente studio mostra quanto poco le comunità bentoniche dell'Antartide siano studiate e quanto poco si sappia ancora sulle relazioni esistenti tra gli organismi dell'Oceano Antartico. Nel prossimo futuro, un aumento dello sforzo di campionamento e studi più approfonditi, dovrebbero essere condotti in sinergia, al fine di sostenere l'ipotesi secondo cui l'Oceano Meridionale rappresenti un hot-spot di biodiversità.
STYLASTERIDAE (CNIDARIA:HYDROZOA) DELL'ANTARTIDE E LORO SPUGNE ASSOCIATE
VULTAGGIO, CARLO
2020/2021
Abstract
The family Stylasteridae Gray 1847 is one of 112 families of hydrozoans belonging to the phylum Cnidaria, which to date includes 328 species and 33 genera distributed throughout the world, except for the Arctic. Stylasterids, commonly known as 'lace corals', are colonial benthic organisms that require a hard substrate on which to settle and grow. They have a calcareous skeleton, called coenosteum, and polymorphic colonies represented by two different types of polyps: gastrozoids and dactylozoids. Stylasterids play an important ecological role. In fact, in many environments, they are considered habitat-forming species because, thanks to the three-dimensional structure of their calcareous skeleton, they contribute to habitat complexity, creating refuges for a variety of organisms, such as sponges. However, in the literature, information on Stylasteridae and their epibionts is relatively scarce. The main aim of this work was to make a contribution to enriching knowledge on the taxonomy and ecology of these organisms. The analyses were based on the observation of multiple samples of different Stylasteridae species and their epibionts, mainly sponges, sampled in Antarctica. 6 Sampling was conducted in the Ross Sea at 12 sites during the XXXII Antarctic campaign, between January and February 2017, using an epibenthic sled and a box corer, at depths between 432 and 1022 metres. Samples of stylasterids, already dead at the time of sampling, and associated sponges, were then treated with hydrogen peroxide (35%) and nitric and sulphuric acid, respectively, and subsequently identified to the lowest possible taxonomic level through scanning electron microscope (SEM), stereomicroscope and light microscope observations. The taxonomic study of the collected specimens led to the identification of four species of stylasterids: Errina fissurata (Gray, 1872), Errina laterorifa Eguchi, 1964, Errina (Errina) gracilis von Marenzeller, 1903 and Inferiolabiata labiata (Moseley, 1879), and 38 species of sponges, of which 9 are probably new species, belonging to two classes of porifers, Demospongiae Sollas, 1885 and Hexactinellida Schmidt, 1870. Through comparisons with literature data, it has emerged that our data concerning the geographical distribution of the identified stylasterid species confirm those already observed by other authors, while as far as sponges are concerned, it is hypothesised that stylasterid beds are not the ideal secondary substrate for them as they do not represent a living or elevated substrate, but in 7 lack of data in this respect, further studies are needed to confirm our hypotheses. In conclusion, the present study shows how little Antarctic benthic communities are studied and how little is still known about the relationships between organisms in the Antarctic Ocean. In the near future, an increased sampling effort and more in-depth studies should be conducted in synergy in order to support the hypothesis that the Southern Ocean represents a biodiversity hot-spot.| File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12075/8295