Daniela Pica

Background Mitochondrial genomes among Medusozoa show considerable variation in the class Hydrozoa, and many phylogenetic relationships inside the subphylum remain still unresolved. Stylasteridae, one of the most species-rich families among hydrozoans, characterized by a calcareous skeleton, lacks mitochondrial genomic information, limiting our understanding of their evolution and phylogenetic position within Hydrozoa. Methods and results This study present the first mitochondrial genome of two stylasterid species from the genus Errina (E. aspera and E. atlantica). Total genomic DNA was extracted and sequenced using Illumina NovaSeq 6000 and mitochondrial genomes were assembled and annotated using two different methods. Results hypothesized linear genomes of 14,938 bp and 14,969 bp respectively, containing 13 protein-coding genes, 2 transfer RNA genes, and 2 ribosomal RNA genes. The gene order was congruent with other Filifera, but lacking the cox1 duplication, transposition, and inversion common in other hydrozoans. Phylogenetic analyses confirmed the position of stylasterids as a sister group to Hydractiniidae within the Filifera suborder. Conclusions This study provides the first information about the stylasterid mitochondrial genome structure. Moreover, the phylogenetic analysis confirms the phylogenetic position of Hydractiniidae as sister family of Stylasteridae. The new findings have highlighted the importance of sequencing additional genomic data to better unravel the evolutionary history of this significant family.

The association between two hydrozoans, Stylaster sp. and Millepora spp., has been described as a case of pseudo-auto-epizoism, and has only been reported from the Caribbean region of the Atlantic Ocean. Here, we report on the occurrence of this association in the Pacific Ocean on coral reefs around Iriomote-jima Island, Japan, suggesting the association to be more widespread than had previously been thought. Moreover, Stylaster sp. colonies were observed living healthily on bleached and dead branches of Millepora spp., indicating that this interaction is facultative. The interaction reported here differs from the relationship between the Caribbean Stylaster roseus and Millepora alcicornis by the connection points between the two partners, which is made evident by the whitening of the Millepora counterpart in Iriomote-jima Island, while being seamless in the Caribbean association. Further research is necessary to fully understand the nature of these relationships, comprehending under what conditions it occurs, and establishing which species are involved in the interactions.

The Amendolara Bank was recently designated as a Site of Community Importance; however, information on its ecosystems remains limited, with a particular dearth of knowledge regarding the deeper zone (>100 m). Previous studies have discovered the existence of Vulnerable Marine Ecosystems (VMEs) within the bank, underscoring the necessity for more comprehensive data and its significance in terms of conservation in the Ionian Sea. This study aims to investigate various aspects of the bank using Remotely Operated Vehicles (ROVs) to shed light on the possible presence of VME indicator species, their relationship with environmental variables, their connection with the observed fish, and to assess anthropogenic impact via the identification of fishing gear within the study area. This present research provides new information on the biodiversity of the Amendolara Bank, revealing the presence of four VME indicator species including the first sightings of black coral Antipathella subpinnata and the precious red coral Corallium rubrum. Moreover, it provides evidence on the interaction between fish fauna and VME indicator species as well as signs of anthropogenic impact from abandoned, lost, or otherwise discarded fishing gear (ALDFG). These findings highlight the urgent need for additional research to improve the knowledge base on the biodiversity of this unique spot in the Ionian Sea which would in turn ensure the development and implementation of more effective conservation and management measures.

Capitate hydrozoans are a morphologically and ecologically diverse hydrozoan suborder, currently including about 200 species. Being grouped in two clades, Corynida and Zancleida, these hydrozoans still show a number of taxonomic uncertainties at the species, genus and family levels. Many Capitata species established symbiotic relationships with other benthic organisms, including bryozoans, other cnidarians, molluscs and poriferans, as well as with planktonic dinoflagellates for mixotrophic relationships and with bacteria for thiotrophic ectosymbioses. Our study aimed at providing an updated and comprehensive phylogeny reconstruction of the suborder, at modelling the evolution of selected morphological and ecological characters, and at testing evolutionary relationships between the symbiotic lifestyle and the other characters, by integrating taxonomic, ecological and evolutionary data. The phylogenetic hypotheses here presented shed light on the evolutionary relationships within Capitata, with most families and genera being recovered as monophyletic. The genus Zanclea and family Zancleidae, however, were divided into four divergent clades, requiring the establishment of the new genus Apatizanclea and the new combinations for species in Zanclea and Halocoryne genera. The ancestral state reconstructions revealed that symbiosis arose multiple times in the evolutionary history of the Capitata, and that homoplasy is a common phenomenon in the group. Correlations were found between the evolution of symbiosis and morphological characters, such as the perisarc. Overall, our results highlighted that the use of genetic data and a complete knowledge of the life cycles are strongly needed to disentangle taxonomic and systematic issues in capitate hydrozoans. Finally, the colonization of tropical habitat appears to have influenced the evolution of a symbiotic lifestyle, playing important roles in the evolution of the group.

The carbonatic scleraxis of Corallium rubrum (L.), commonly known as red coral, is often found infested by excavating sponges. These boring organisms produce galleries inside the compact axis of the coral in a variety of shapes compromising the integrity of the skeleton and reducing its commercial value. Three sponge species, already known to bore into Corallium rubrum, have been identified in colonies collected from Cape Verde Archipelago—Alectona millari (Carter, 1879); Dotona pulchella mediterranea (Rosell and Uriz, 2002); and Thoosa armata (Topsent, 1888)—together with a new species belonging to the genus Alectona and here described. SEM analysis provided evidence of the microerosion patterns of these species, confirming the presence of radial scars overlapped with the concentric ones, in T. armata. For the first time, microcomputed tomography was employed to obtain three-dimensional reconstructions of sponge excavations inside the red coral scleraxis and to estimate the eroded volume.

The Stylasteridae, commonly known as lace corals, is a family of colonial calcifying hydrozoans mostly inhabiting deep waters. Stylasterids show a cosmopolitan distribution but, in some areas, they are characterized by low species diversity, such as in the Red Sea, where only a shallow-water species has been reported so far. With this work, we provide the first evidence of a deep-sea stylasterid inhabiting the NEOM region in the northern Saudi Arabian Red Sea, at depths ranging between 166 and 492 m. Morphological examinations revealed that this species was previously unknown and belonging to the genus Stylaster. We, therefore, describe Stylaster tritoni sp. nov., representing the first record of the genus in the Red Sea. Lastly, the phylogenetic position of the species within the Stylasteridae was evaluated, revealing a close relationship with shallow-water Indo-Pacific and Western Atlantic Stylaster species and confirming the polyphyletic nature of the genus Stylaster.

The mesophotic zone is a relatively poorly studied area of the Mediterranean Sea, drawing great interest by the scientific community in the last years. This zone represents a connection between the shallow water and the deep-sea communities, in which photophilic framework builders (e.g. coralline red algae) are gradually replaced by heterotrophic ones, such as ahermatypic corals and the bivalve Neopycnodonte cochlear. In this habitat the framework-forming organisms produce a hard substrate with a high topographic complexity, hosting a great biodiversity of secondary structuring taxa like bryozoans. During a survey on coralligenous banks in the mesophotic zone in c. 60 m depth off Gallipoli (southern Apulia), epibiotic aggregations of N. cochlear were found on the fans of the hexacoral Savalia savaglia. In the present paper the diversity of cheilostomatid bryozoans hosted by these bivalve aggregations is described and compared with published information on similar nearby habitats. A total of 48 taxa were found, six of which are newly described: Crassimarginatella matildae sp. nov., Micropora biopesiula sp. nov., Haplopoma celeste sp. nov., Schizomavella (Schizomavella) cerranoi sp. nov., Schizomavella (Calvetomavella) biancae sp. nov., and Schizoporella adelaide sp. nov. The species richness known from the southern Apulian shelf at this depth (47 species) is hereby raised to 83 cheilostomatid bryozoans. Moreover, only 12 species are shared with the other localities studied previously, while 36 are restricted to Gallipoli, supporting the hypothesis of a high rate of exclusivity among Apulian sites in terms of species composition. The differences in faunal composition, and particularly the presence of several new species discovered at Gallipoli, show once more that our knowledge of the bryozoan fauna in certain Mediterranean habitats is still incomplete and warrants further studies. https://doi.org/urn:lsid:zoobank.org:pub:DDC82039-EF44-4169-8198-C67F60B14BA0

Porifera are considered key components of benthic communities, being typical inhabitants of both shallow and deep waters, from the mesolittoral to the bathyal zone. Although sponges are one of the most common organisms in Western Mediterranean ecosystems, in many areas the knowledge on this taxon is still very limited. In the current study, we aim to analyse and compare the sponge communities characterising the hard bottoms of two islands, Montecristo and Giglio, belonging to the Tuscan Archipelago National Park (TANP, Italy), in relation to a bathymetric gradient. A total of 340 samples were collected, 13 orders and 48 species (46 Demospongiae and 2 Calcarea) identified, with Chondrosia reniformis representing the most recorded species, being found at all sites at almost all depths. Depth was the only significant factor in the observed pattern, while the sponge community is shared between the two Islands. In addition, our data were analysed together with data available in the literature on sponges of the Tuscan Archipelago, to assess the sampling effort. Among all the Islands of the Archipelago, Giglio and Montecristo showed the higher mean species diversity. Nonetheless, the sampling effort resulted not sufficient for each Island and future studies targeting Porifera are needed. Our work is the first summarising the sponge diversity of the entire Tuscan Archipelago, and one of the few focussing entirely on the sponge fauna. These results provide new important information on the area of the TANP, aimed to become a future Marine Protected Area, adding new records, and highlighting the high diversity of a poorly known area.

The hydrozoan family Cladocorynidae inhabits tropical to temperate waters and comprises the two genera Pteroclava and Cladocoryne. Pteroclava lives in association with some octocorals and hydrozoans, whereas Cladocoryne is more generalist in terms of substrate choice. This work provides a thorough morpho‐molecular reassessment of the Cladocorynidae by presenting the first well‐supported phylogeny of the family based on the analyses of three mitochondrial and four nuclear markers. Notably, the two nominal genera were confirmed to be monophyletic and both morphological and genetic data led to the formal description of a new genus exclusively associated with octocorals, Pseudozanclea gen. nov. Maggioni & Montano. Accordingly, the diagnosis of the family was updated. The ancestral state reconstruction of selected characters revealed that the symbiosis with octocorals likely appeared in the most recent common ancestor of Pteroclava and Pseudozanclea. Additionally, the presence of euryteles aggregation in the polyp stage and the exumbrellar nematocyst pouches with euryteles represent synapomorphies of all cladocorynid taxa and probably emerged in their most recent common ancestor. The analysis of several Pteroclava krempfi colonies from Indo‐Pacific and Caribbean localities associated with several host octocorals revealed a high intra‐specific genetic variability. Single‐ and multi‐locus species delimitations resulted in three to five species hypotheses, but the statistical analysis of morphometric data showed only limited distinction among the clades of P. krempfi. However, P. krempfi clades showed differences in both host specificity, mostly at the octocoral family level, and geographic distribution, with one clade found exclusively in the Caribbean Sea and the others found in the Indo‐Pacific.