Daniela Pica

New insights into the symbiosis between zanclea (cnidaria, hydrozoa) and scleractinians

Hydroids in the genus Zanclea are a recently discovered component of the fauna associated with reef‐building corals. The phylogenetic relationships among these species are not well known. The present work is based on field surveys in the Republic of Maldives, and for the first time, morphological and molecular analyses are integrated to distinguish a new hydroid species and provide new information on the ecology of this symbiosis. This new hydroid, Zanclea gallii sp. n., was associated with the scleractinian Acropora muricata; it was living sympatrically with its congener Zanclea sango, which was observed for the first time at this locality on the new scleractinian host Pavona varians. The relationships between these two hydroids and other available scleractinian‐associated Zanclea were investigated using two molecular markers, nuclear 28S rDNA and mitochondrial 16S rRNA. Zanclea gallii sp. n. and Z. sango were recovered as distinct lineages within a monophyletic group of scleractinian‐associated Zanclea based on both molecular and morphological data. All Zanclea species that were observed living in association with scleractinians belong to the ‘polymorpha group’ and share the morphological characteristic ‘polymorphic colony’. The genus Leptoseris is the 16th host coral identified for Zanclea. Compared with the frequency of the Z. gallii sp. n. association with A. muricata and Z. sango with the scleractinian P. varians, the latter is twice as common; however, the former exhibited higher Zanclea polyps concentrations over the colony surface. Overall, the Zanclea survey indicates that these diminutive hydroids are more commonly associated with coral than previously known.

Three-dimensional analysis of the canal network of an Indonesian Stylaster (Cnidaria, Hydrozoa, Stylasteridae) by means of X-ray computed microtomography

This study describes the architecture of the coenosteal network in an Indonesian Stylaster species investigated by means of the X-ray computed microtomography (μ-CT) technique. The 3D approach allowed to characterize all internal cavity structures: a network of thin canals, gastropores, dactylopores, and ampullae. The main feature highlighted by this reconstruction is a dense network of thin canals extended to the entire colony. This network gives rise to and surrounds each cyclosystem. Moreover, the 3D analysis made it possible to study the reciprocal relationship between adjacent cyclosystems and to hypothesize the growth process of the branches of Stylaster sp.: each new cyclosystem buds between the gastropore and the dactylopores of the last formed one. The dactylopores of each cyclosystem are partially derived from the precedent one and are partially newly formed. The thin canals enveloping the dactylopores are actively involved in both the formation of a new gastropore and in the re-establishment of the typical amount of dactylopores in each cyclosystem. This growth process was confirmed by the scanning electron microscopy (SEM) observations of apical cyclosystems of several specimens. Results indicate that the non-destructive X-ray μ-CT technique can be fruitfully applied to characterize the coenosteal structures of stylasterids allowing the repetitive study of a specimen by means of virtually infinite section planes and different kinds of analyses (e.g., channel width and porosity).

Pteroclava krempfi-octocoral symbiosis: new information from the Indian Ocean and the Red Sea

Some hydroids are known to form strict relationships with anthozoans. In this study we report the first evidence of the association between Pteroclava krempfi (Hydrozoa: Capitata: Cladocorynidae) and octocorals of the alcyonacean genera Sarcophyton, Lobophytum and Sinularia observed in the Republic of Maldives and in the Red Sea. Our observations contribute to an expansion of both the recorded host-range and geographical distribution of this symbiosis, indicating that the association between hydroids and alcyonaceans is more widespread than previously known.

Boring and cryptic sponges in stylasterids (Cnidaria: Hydrozoa)

Abstract The hydroids belonging to the family Stylasteridae are considered habitat-forming species due to their rigid and branched calcareous skeleton, producing structurally complex habitats which support a high taxonomic diversity of associated fauna. Numerous organisms, such as gastropods, polychaetes, barnacles and other invertebrates, were found in association with dead or living colonies of stylasterids. No specific studies have previously been dedicated to the diversity of sponges in association with these corals. In this study 15 sponge species were found in the coenosteum of Distichopora spp. (ten boring and five insinuating species) and one boring species was associated with Stylaster sp. In Distichopora species the sponges were mainly localized into the dead basal portion of the colonies that is overgrown by algae or bryozoans. Only Aka labyrinthica was found inside the skeleton of the living portion of the colonies, being able to compete with the coenosteal stolon network that pervades the carbonatic skeleton. Nevertheless, in Distichopora spp. colonies no coral reaction to the sponge colonisation was observed. The basal portions of the Stylaster sp. colonies, enveloped by the massive specimens of Spheciospongia cf. solida, were completely demolished by the boring activity of the sponge, while the apical portions were alive. The sponge incorporated the coral skeleton and its tissue penetrated into the coral through the coenosteal pores. Stylaster sp. presented a reaction to prevent the penetration of the sponge: hydranths were regressed and calcium carbonate septa were formed, in order to close the gastropores of the coral, indicating a wide plasticity and quick mineralization of the coenosteum.

A new species of Triptolemma (Porifera: Pachastrellidae) from the Pacific Ocean with a revision of the genus

A new species, T. strongylata sp. nov. is described on the basis of material collected from the Pacific Ocean. The new species is characterized by the presence of sinuous strongyles. Moreover the incomplete description of T. simplex (Sara, 1959 ) is implemented on the basis of new abundant material allowing, for the first time, the complete description of the skeleton of a Triptolemma species and the detecting of the presence of monaxonic spicules in the spicular complement of the genus. The skeleton is composed of a thick crust of disorderly arranged mesotriaenes and scattered microscleres, supported by diverging spicule tracts formed by oxeas towards the surface. Both species were recorded associated to boring sponges (Spiroxya and Cliona) in excavations of the calcareous scleraxis of precious corals or in organogenic concretions. In the cavities where the tissue of Triptolemma was recorded the wall of the excavation partially lost its typical pattern characterized by ovoid scars and became irregularly eroded. Our hypothesis is that Triptolemma insinuates inside the erosions produced by other sponges and it is able to enlarge them by an etching mechanism based on chemical dissolution only.

Morphology and development of the early growth stages of an Indonesian Stylaster (Cnidaria: Hydrozoa)

The aim of this work is to describe the skeletal morphology of the early stages of the colonies of Stylaster sp., settled on artificial panels placed along a coral reef in the Bunaken Marine Park (North Sulawesi, Indonesia). The youngest observed stage deriving from the planula settlement is represented by a well developed primary cyclosystem symmetrically budding two secondary cyclosystems in a very early phase of growth. Successively each cyclosystem starts its vertical growth producing new cyclosystems sympodially arranged. At the same time the basal disc of the first cyclosystem enlarges producing a flattened crust from which new colonies arise. Vertical and encrusting forms are considered different modalities to face the problem of space competition in marine benthic organisms. The colonies of Stylaster sp. grow using both strategies resulting in the asexual reproduction of several colonies from a single settled planula. The new cyclosystems originate as small volcano-like elevations having the centre filled with calcium carbonate. Gradually this calcareous matrix dissolves starting from its perimetric zone and leads to the formation of the gastrostyle and the ring palisade. It is plausible that the cells composing the stolon nets deeply pervading the calcareous structure are responsible for this skeletal plasticity.

Hydroid diversity of Eilat Bay with the description of a new Zanclea species

ABSTRACT Eilat Bay is located at the southernmost tip of Israel in the Gulf of Aqaba (Red Sea). The list of hydroids currently known from there includes 51 species, and when extending it to the entire Red Sea, it includes 157 species belonging to 41 families. Nevertheless, the information regarding hydroids in the Gulf of Aqaba, and in particular in Eilat Bay, is not exhaustive. The aim of this work is to improve knowledge of hydroid biodiversity in this area. The specimens collected during the HyDRa project (Hydroid Diversity of the Northern Red Sea) revealed the presence of 27 species, 13 Anthoathecata and 14 Leptothecata, belonging to 17 families and 20 genera. Two families, Cladonematidae and Corynidae, and five genera, Cladonema, Slabberia, Campanularia, Nemalecium and Lafoeina, are new findings for the Red Sea. Furthermore, Nemalecium lighti, Zanclea gallii and the new species Zanclea eilatensis sp. nov. have never before been recorded in the Red Sea. Zanclea eilatensis sp. nov. lives in association with a bryozoan, has a monomorphic colony lacking a perisarc and only has stenoteles in the polyps. The medusa stage has two prominent perradial exumbrellar nematocyst pouches and two tentacles with about 50 cnidophores having long flagella and containing macrobasic euryteles. In the present work, 54% of the species were associated with other organisms, such as hydroids, corals and bryozoans. New ecological data about the Zanclea–scleractinian coral association are documented. The present investigation provides new information about diversity in the Red Sea, and in particular in Eilat Bay. In addition, our data also have significance for Mediterranean and Red Sea biodiversity conservation due to the recent expansion of the Suez Canal and the consequent possible increase in the introduction of nonindigenous species in both directions. http://zoobank.org/urn:lsid:zoobank.org:pub:C9EA7333-B9DF-4888-A643-4D45E6CD31CB

Microboring organisms in living stylasterid corals (Cnidaria, Hydrozoa)

ABSTRACT Microboring or euendolithic microorganisms, which colonize and penetrate various carbonate substrates, are abundant in coral reef ecosystems and play a major role in reef carbonate dissolution. A few studies reported the presence of euendoliths in stylasterid coral skeletons but the biological identity, distribution and abundance of these microorganisms remain largely unknown. Observations of over 100 stylasterid colonies, collected in the Indo-Pacific area, revealed for the first time that the association between these corals and euendolith organisms appears to be quite common in shallow tropical waters. The most abundant euendolith was identified as a cryptic stage in the development of the rhodophyte Porphyra (Conchocelis stage). The euendoliths were observed in the skeletons of seven species of three genera (four Stylaster, two Distichopora and one Lepidotheca). The presence of euendoliths inside skeletons conferred a particular colour to the studied stylasterid corals. Distribution and abundance of microborings varied significantly among stylasterid species and among branches of a single colony and so did the colour of their skeletons. Colonization of skeletons and the associated colour distribution were almost uniform in some stylasterids, forming an upward gradually diminishing or sharply limited gradient. This study shows that patterns of euendolith colonization and growth in stylasterid skeletons may depend on the stage of the euendolith development as well as on their environmental requirements such as light exposure.

Southern hemisphere deep-water stylasterid corals including a new species, Errina labrosa sp. n. (Cnidaria, Hydrozoa, Stylasteridae), with notes on some symbiotic scalpellids (Cirripedia, Thoracica, Scalpellidae)

Abstract A number of stylasterid corals are known to act as host species and create refuges for a variety of mobile and sessile organisms, which enhances their habitat complexity. These include annelids, anthozoans, cirripeds, copepods, cyanobacteria, echinoderms, gastropods, hydroids and sponges. Here we report the first evidence of a diverse association between stylasterids and scalpellid pedunculate barnacles and describe a new stylasterid species, Errina labrosa, from the Tristan da Cunha Archipelago. Overall, five stylasterid species are found to host eight scalpellid barnacles from several biogeographic regions in the southern hemisphere (Southern Ocean, temperate South America and the southern Indo-Pacific realms). There is an apparent lack of specificity in this kind of association and different grades of reaction to the symbiosis have been observed in the coral. These records suggest that the association between pedunculate barnacles and hard stylasterid corals has a wide distribution among different biogeographic realms and that it is relatively rare and confined largely to deep water.

Genetic diversity of the Acropora-associated hydrozoans: new insight from the Red Sea

To date, four nominal species and several other unidentified species of Zanclea hydrozoans are known to live symbiotically with scleractinians, and recent surveys reported this association also in the Red Sea. Previous molecular studies showed that each coral genus involved in this association hosts only one species or molecular clade of Zanclea, with the only exception being the genus Acropora, which hosts at least two Zanclea species. Moreover, some of the detected genetic lineages were morphologically undistinguishable in the polyp stage, suggesting the presence of cryptic species. In this study, we investigated the morphology and genetic diversity of Acropora-associated Zanclea specimens collected in previous studies in Egypt and Israel, as well as new samples collected in Saudi Arabia. Based on the current data, all the analysed samples were morphologically identical to Zanclea gallii, a species associated with Acropora corals from the Maldives. However, molecular analyses separated the samples collected in the Red Sea from all other coral-associated hydroids. Therefore, phylogenetic reconstructions, haplotype networks, genetic distance analyses and distribution data allowed us to identify a previously unknown cryptic species of Acropora-associated hydroid, here named Zanclea gallii IIa, following a recently proposed molecular nomenclature.