A preliminary survey of marine cave habitats in the Maltese Islands

The Mediterranean Sea is a hotspot for marine biodiversity. Past studies of Mediterranean marine caves have revealed the unique biocoenotic and ecological characteristics of these habitats, which are protected by European Union legislation. The Maltese Islands have an abundance of partially and fully submerged marine caves with di fferent geomorphological characteristics, yet there have been no systematic studies on these habitats and their associated species. This study is a firrst synthesis of existing information on the biotic assemblages and physical characteristics of Maltese marine caves. The work combines a review of the available information with a preliminary survey of some marine caves in Gozo, during which several species were recorded for the first time for the Maltese Islands. Characteristic species recorded from local marine caves are highlighted, including several species of red and brown algae, sessile invertebrates including bryozoans, ascidians and sponges, and mobile forms including crustaceans and fi sh. A marked zonation from the cave entrance to the inside of the caves was identifi ed: photophilic algae at the mouth of the cave are progressively replaced by more sciaphilic species, followed by a middle section dominated by sessile invertebrates, and then a completely dark inner section that is mostly devoid of sessile organisms. Several species protected by national and international legislation were found to occur.peer-reviewe

Origin and evolution of the Notch signalling pathway: an overview from eukaryotic genomes

Background. Of the 20 or so signal transduction pathways that orchestrate cell-cell interactions in metazoans, seven are involved during development. One of these is the Notch signalling pathway which regulates cellular identity, proliferation, differentiation and apoptosis via the developmental processes of lateral inhibition and boundary induction. In light of this essential role played in metazoan development, we surveyed a wide range of eukaryotic genomes to determine the origin and evolution of the components and auxiliary factors that compose and modulate this pathway. Results. We searched for 22 components of the Notch pathway in 35 different species that represent 8 major clades of eukaryotes, performed phylogenetic analyses and compared the domain compositions of the two fundamental molecules: the receptor Notch and its ligands Delta/Jagged. We confirm that a Notch pathway, with true receptors and ligands is specific to the Metazoa. This study also sheds light on the deep ancestry of a number of genes involved in this pathway, while other members are revealed to have a more recent origin. The origin of several components can be accounted for by the shuffling of pre-existing protein domains, or via lateral gene transfer. In addition, certain domains have appeared de novo more recently, and can be considered metazoan synapomorphies. Conclusion. The Notch signalling pathway emerged in Metazoa via a diversity of molecular mechanisms, incorporating both novel and ancient protein domains during eukaryote evolution. Thus, a functional Notch signalling pathway was probably present in Urmetazoa

Express method for isolation of ready-to-use 3D chitin scaffolds from aplysina archeri (aplysineidae: verongiida) demosponge

Sponges are a valuable source of natural compounds and biomaterials for many biotechnological applications. Marine sponges belonging to the order Verongiida are known to contain both chitin and biologically active bromotyrosines. Aplysina archeri (Aplysineidae: Verongiida) is well known to contain bromotyrosines with relevant bioactivity against human and animal diseases. The aim of this study was to develop an express method for the production of naturally prefabricated 3D chitin and bromotyrosine-containing extracts simultaneously. This new method is based on microwave irradiation (MWI) together with stepwise treatment using 1% sodium hydroxide, 20% acetic acid, and 30% hydrogen peroxide. This approach, which takes up to 1 h, made it possible to isolate chitin from the tube-like skeleton of A. archeri and to demonstrate the presence of this biopolymer in this sponge for the first time. Additionally, this procedure does not deacetylate chitin to chitosan and enables the recovery of ready-to-use 3D chitin scaffolds without destruction of the unique tube-like fibrous interconnected structure of the isolated biomaterial. Furthermore, these mechanically stressed fibers still have the capacity for saturation with water, methylene blue dye, crude oil, and blood, which is necessary for the application of such renewable 3D chitinous centimeter-sized scaffolds in diverse technological and biomedical fields. © 2019 by the authors

Molecular Phylogeny Restores the Supra-Generic Subdivision of Homoscleromorph Sponges (Porifera, Homoscleromorpha)

Homoscleromorpha is the fourth major sponge lineage, recently recognized to be distinct from the Demospongiae. It contains <100 described species of exclusively marine sponges that have been traditionally subdivided into 7 genera based on morphological characters. Because some of the morphological features of the homoscleromorphs are shared with eumetazoans and are absent in other sponges, the phylogenetic position of the group has been investigated in several recent studies. However, the phylogenetic relationships within the group remain unexplored by modern methods.Here we describe the first molecular phylogeny of Homoscleromorpha based on nuclear (18S and 28S rDNA) and complete mitochondrial DNA sequence data that focuses on inter-generic relationships. Our results revealed two robust clades within this group, one containing the spiculate species (genera Plakina, Plakortis, Plakinastrella and Corticium) and the other containing aspiculate species (genera Oscarella and Pseudocorticium), thus rejecting a close relationship between Pseudocorticium and Corticium. Among the spiculate species, we found affinities between the Plakortis and Plakinastrella genera, and between the Plakina and Corticium. The validity of these clades is furthermore supported by specific morphological characters, notably the type of spicules. Furthermore, the monophyly of the Corticium genus is supported while the monophyly of Plakina is not.As the result of our study we propose to restore the pre-1995 subdivision of Homoscleromorpha into two families: Plakinidae Schulze, 1880 for spiculate species and Oscarellidae Lendenfeld, 1887 for aspiculate species that had been rejected after the description of the genus Pseudocorticium. We also note that the two families of homoscleromorphs exhibit evolutionary stable, but have drastically distinct mitochondrial genome organizations that differ in gene content and gene order

Biochemical Trade-Offs: Evidence for Ecologically Linked Secondary Metabolism of the Sponge Oscarella balibaloi

Secondary metabolite production is assumed to be costly and therefore the resource allocation to their production should be optimized with respect to primary biological functions such as growth or reproduction. Sponges are known to produce a great diversity of secondary metabolites with powerful biological activities that may explain their domination in some hard substrate communities both in terms of diversity and biomass. Oscarella balibaloi (Homoscleromorpha) is a recently described, highly dynamic species, which often overgrows other sessile marine invertebrates. Bioactivity measurements (standardized Microtox assay) and metabolic fingerprints were used as indicators of the baseline variations of the O. balibaloi secondary metabolism, and related to the sponge reproductive effort over two years. The bioactivity showed a significant seasonal variation with the lowest values at the end of spring and in early summer followed by the highest bioactivity in the late summer and autumn. An effect of the seawater temperature was detected, with a significantly higher bioactivity in warm conditions. There was also a tendency of a higher bioactivity when O. balibaloi was found overgrowing other sponge species. Metabolic fingerprints revealed the existence of three principal metabolic phenotypes: phenotype 1 exhibited by a majority of low bioactive, female individuals, whereas phenotypes 2 and 3 correspond to a majority of highly bioactive, non-reproductive individuals. The bioactivity was negatively correlated to the reproductive effort, minimal bioactivities coinciding with the period of embryogenesis and larval development. Our results fit the Optimal Defense Theory with an investment in the reproduction mainly shaping the secondary metabolism variability, and a less pronounced influence of other biotic (species interaction) and abiotic (temperature) factors

Oscarella malakhovi Ereskovsky, 2006, sp. nov.

Oscarella malakhovi sp. nov. (Figs. 2–8) Material examined. Holotype ZIN RAS 10697 — Russia, Japan Sea, Gulf of the Peter the Great, Vostok Bay, Pashennikov Cape, (42 ° 54 ’ 50 ’’ N – 132 ° 38 ’ 44 ’’ W), 0.2 m, the boulders, 11.08. 2006, collector A.V. Ereskovsky. Paratypes: ZIN RAS 10698 — Russia, Japan Sea, Gulf of the Peter the Great, Vostok Bay, Pashennikov Cape, (42 ° 54 ’ 50 ’’ N — 132 ° 38 ’ 44 ’’ W), 0.2 m, 11.08. 2006, collector D.B. Tokina; ZIN RAS 10699 — the same locality, 4 m, the stones, silt, 0 9.08. 2006, collector A.V. Ereskovsky. Diagnosis. Intertidal and upper supralittoral Oscarella, pinky-beige to yellow in color, with lumpy, microlobate surface, soft, slimy consistency, two particular kinds of cells with inclusions (vacuolar and granular cells), and with two endobiont bacteria species. Description. Thinly encrusting, irregular, lobate sponge, generally pinky-beige, or yellow color, from 0.8–1.5 up to 3–8 cm in diameter, with a soft, slimy consistency. Lobes are small, round, and irregular (Fig. 2). The surface is perforated by abundant inhalant ostia 9–12 µm in diameter (Fig. 3). Most specimens are 1–2 mm thick, and lumpy or undulating with a few oscular tubes about 1–2 mm in height. The sponge is loosely attached to the substratum. Under low magnification (40 ×) the colorless spherical choanocyte chambers can be seen in the living material, and orange spherical embryos. Soft tissue organisation. A spicule and fibre skeleton is absent. The ectosome is 8–15 µm thick. Inhalant canals (6 – 3 µm in diameter) run perpendicular to the surface (Fig. 3). Choanocyte chambers are ovoid to spherical eurypilous, 12–33 µm in diameter (Fig. 4 A, C). Exhalant canals run towards a well-developed system of basal exhalant cavities about 38 µm in diameter, lead to the oscula. Ostia are 9–12 µm in diameter (Fig. 4 B, D). Cytology. Choanocytes ovoid to pyramidal, irregular, 2.9 µm in the base and 4.1 µm high (Fig. 5 A, B). Nucleus basal or, rarely apical, 2 µm in diameter. Cytoplasm with up to eight phagosomes from 0.6 to 2.3 µm in diameter. The collar measures 1.9 µm in width with about 27 microvilli. The choanocytes contact each other at their middle sections. Their basal parts show no or very rare pseudopodia. Apopylar cells (Fig. 5 B, C) are roughly triangular in section, 8.4 µm wide by 3.6 µm in high. Nucleus is spherical, up to 2.3 µm in diameter. Cytoplasm contains mitochondria, digestive vacuoles, and small osmiophilic inclusions. Endopinacocytes (Fig. 5 D, E) are flat to irregular, flagellated 6.7 µm wide by 2.2 µm high. They are anchored in the mesohyl by long thin basal pseudopodia. Their free surface is studded with cytoplasmic projections. Nucleus is ovoid (2.3 µm in diameter), often with the nucleolus. The cytoplasm contains inclusions and phagosomes from 0.6 to 2.3 µm in diameter. Exopinacocytes (Figs. 4 D; 5 F) are similar to the exopinacocytes (5.4 µm wide by 2.3 µm high), except in their flat free surface. A thin irregular layer of glycocalyx covers the surface of exopinacocytes, endopinacocytes, choanocytes and apopylar cells. Choanoderm and pinacoderm are lined by a basement membrane-like structure, which is a continuous, from 0.4 to 0,2 µm thick layer of condensed collagen fibrils in the mesohyl closely adjacent to the base of the cells (Fig. 5 B). Archaeocytes ( Fig. 6 A, B ) very rare, ovoid to irregular, 4.6 µm. The cytoplasm has small phagosomes and rare electron transparent vacuoles from 0.6 to 1.1 µm in diameter. Nucleus ovoid or irregular, 2.6 µm, nucleolated. Within the mesohyl two types of cells with inclusions are observed. Granular cells (Fig. 6 C) are very rare, ovoid, about 4.5 µm. Cytoplasm filled with oval electron dense granules 1.1 µm. Nucleus, irregular 1.8 µm in diameter, without a nucleolus. Vacuolar cells (Figs. 5 C, F; 6 D) abundant, often near the choanocytes chambers or exopinacoderm. These cells are ovoid to irregular 6.1 µm. Nucleus 1.7 µm in diameter, ovoid or compressed by the vacuoles. Cytoplasm with, 3–6 larger vacuoles, 2.9 µm in diameter, with clear and filamentous contents, 3–7 small inclusions (1.4 µm in diameter) with electron-dense homogeneous contents from spherical to triangulate, and pahgosomes 1 µm in diameter. This cell type to be involved in the secretion of ground substances of the intercellular matrix, because it is often seen liberating the contents of its larger, clear vacuoles in the mesohyl (Fig. 6 D). Symbiotic bacteria. Endobiont bacteria of two kinds occur in the mesohyl: B 1 and B 2 both are extracellular (Figs. 5 D; 6 A, C; 7 A, B). B 1 is more numerous, oval peanutshaped, has a length of 1.1–1.7 µm and diameter: 0.5–0.9 µm. The cell wall is the Gramnegative. Under the cell wall there is a vast transparent space with filaments. The thickness of the space is very variable. A filamentous network of the nucleoid is irregular: thick elements are in center and thin filaments are closer to periphery of the cell. Near the cytoplasmic membrane a small layer of granular cytoplasm occurs. B 2 type is elongated with the length 0.4–1.1 µm and diameter 0.19–0.3 µm. The cell wall is Gram-negative and consists of two membranes, under which a thin electron transparent space is found. The thick nucleoid filaments form a more ordered voluminous structure with thin periphery of the dark cytoplasm. Development. During the end of July — the end of August sponges are full of oocytes and embryos at different developmental stages: from two blastomeres to larva (Fig. 3 A, B). The larva is a typical homoscleromorph cinctoblastula with the lateral-posterior zone of the cells with intranucleolar paracristalline inclusion and basement membrane. In the larval cavity there are the symbiotic bacteria of two morphotypes. The posterior pole of larvae is colored orange. The O. malakhovi sp. nov. also display asexual reproduction by budding. Numerous small, spherical and transparent buds are visible on the sponge surface (Fig. 8 A, B). The diameter of the buds is from 90 to 140 µm. Habitat and distribution. Specimens of Oscarella malakhovi sp. nov. occur as thin sheets on the sides of bivalve Crenomytilus grayanus (Dunker, 1853), or on the lower side of stones in the Gulf of the Peter the Great, Vostok Bay (42 ° 54 ’ 50 ’’ N – 132 ° 38 ’ 44 ’’ W) at a depth to 0.4–4 m (Fig. 1). Discussion. The genus Oscarella is cosmopolitan with 8 valid species known from different oceans around the world (Table 1), but only four species are known from the Pacific: two from the Indo-Pacific: O. nigraviolacea and O. stillans (Bergquist & Kelly 2004), one species form the Eastern coast of the former URSS — O. lobularis (Koltun 1966). However, this record was considered unrecognizable by Muricy et al. (1996). And one from the Eastern Pacific (California) — O. carmela (Muricy & Pearse 2004). The identification of Oscarella at the species level is difficult because species of this genus have no skeleton, and histological characters are homogeneous. The differences among species are mostly in external traits: color, consistency, and aspect of the surface (Boury-Esnault et al. 1992; Muricy et al. 1996; Muricy & Diaz 2002; Bergquist & Kelly 2004; Muricy & Pearse 2004). But many of them are greatly subjective to describe. Oscarella malakhovi sp. nov. is unique in color: pinky-beige to yellow color had not seen in other Oscarella species. The surface aspects (smooth, microlobate) are helpful, but one cannot separate all species on that basis alone. The new species is thinly encrusting, irregular, sponges, with soft, slimy consistency, lobes are round and irregular. ZOOTAXA 1376 morphological, anatomical, cytological and ecological characters of Oscarella species. O. lobularis O. tuberculata O. viridis O. microlobata O. imperialis O. stillans O. nigraviolacea O. carmela O. malakhovi Oscarella nigraviolacea Bergquist and Kelly, 2004 differs from the new species by its dark violet, almost black color, and the oscules situated on top of papillae. O. stillans Bergquist and Kelly, 2004 forms a series of fused tubes up to 3.5 cm long, some with solid branches, and it is dark honey yellow in color. It also has a characteristically high collagen deposition in the mesohyl, giving it a collagenous consistency. O. carmela Muricy and Pearse, 2004 differs from O. malakhovi sp. nov. by variability of color and surface characters: from light brown to tan or dull orange color, and from a smooth to microlobate surface. Cytological characters, such as the types of cells with inclusions present, are very important for Oscarella species identification. Cells with inclusions are special sponge cells with different cytoplasmic inclusions, most of which have unknown functions (e.g., Simpson 1984; Muricy et al. 1996, 1999). They are diverse and abundant in species of Oscarella, and each species has a particular set of cells with inclusions that are useful characters for species identification (Boury-Esnault et al. 1992; Muricy et al. 1996; Muricy & Pearse 2004). Nowadays at TEM were studied only five Mediterranean and one East-Pacific Oscarella species (Boury-Esnault et al. 1992; Muricy et al. 1996; Muricy & Pearse 2004). Oscarella from the Indo-Pacific had not characterized cytologically. The new species is similar to O. carmela, but differs from all other Mediterranean Oscarella species in its cell contents, which are simple, with only two kinds of cells with inclusions: granular cells and vacuolar cells with two different inclusions, osmiophilic and filamentous (Fig. 6 C, D). In contrast, O. carmela the new species has the granular cells, which absent in O. carmela. The archaeocytes of O. malakhovi sp. nov. differ from O. carmela by absence of abundant long pseudopodia. It is interesting, that the basement membrane-like structure of the new species is apparently thicker (0.4 to 0.3 µm) than in other species of Oscarella — 0.005–0.02 µm (Muricy et al. 1996; Myricy & Pearce 2004). Other useful characters are symbiotic bacteria morphology. Different sponge species from one genus can possess various bacterial morphotypes (Boury-Esnault et al. 1992; Muricy et al. 1996; 1999; Hentschel et al. 2001; Muricy & Pearse 2004). Symbiotic bacteria have been found in the mesohyl of all species of Homoscleromorpha studied so far and the composition of the symbiotic bacterial populations has been shown to be species specific (Boury-Esnault et al. 1992, 1995, Muricy et al. 1996, 1999). As in O. carmela, O. malakhovi sp. nov. has two type of endosymbiotic extracellular bacteria. The differences between the symbiotic bacteria type B 1 in O. malakhovi sp. nov. and O. carmela are: 1 — smooth cell without a wrinkles on its wall; 2 — the cytoplasm is clear and not dark; 3 — has biggest dimension then in O. carmela. The type B 2 in O. malakhovi sp. nov. is smaller then in O. carmela. The sexual and asexual developmental characteristics of the new species are typical for the other Oscarella species described early (Ereskovsky & Boury-Esnault 2002; Boury-Esnault et al. 2003; Ereskovsky & Tokina 2006). The complete absence of a skeleton is shared the genus Oscarella with Hexadella Topsent, 1896 (Verongida, Ianthellidae), Chondrosia Nardo, 1847, Thymosiopsis, Vacelet & Perez, 1998 (Chondrosida, Chondrillidae), Myceliospongia Vacelet & Perez, 1998 (Demospongiae incertae sedis), Halisarca Johnston, 1842 Halisarcida, Halisarciidae), and Pseudocorticium Boury-Esnault et al., 1995 (Homosclerophorida, Plakinidae). These genera can also be distinguished through examination of histological sections to observe the shape and size of the canals, choanocyte chambers, larvae and cytological features. Within the genus Oscarella cytological (ultrastructural) characters, including cellular composition, cell morphology, particularly the cells with inclusions, are more successful for the species discrimination (Boury-Esnault et al. 1992; Muricy et al. 1996; Muricy 1999). The detail cytological analysis of Oscarella species, collected in shallow waters the northwestern Sea of Japan, Russia, allow describing it as a new species.Published as part of Ereskovsky, Alexander V., 2006, A new species of Oscarella (Demospongiae: Plakinidae) from the Western Sea of Japan, pp. 37-51 in Zootaxa 1376 on pages 40-49, DOI: 10.5281/zenodo.17498

Oscarella Vosmaer 1884

Genus Oscarella Vosmaer, 1884 Type species. Halisarca lobularis Schmidt, 1862 (by monotypy). [Oscaria] Vosmaer, 1881: 163 (preocc. by Oscaria Gray, 1873 — Reptilia); Oscarella Vosmaer, 1884: pl. 8 (explanation); 1887: 326 (nom. nov. for Oscaria Vosmaer). Octavella Tuzet and Paris, 1964: 88. Diagnosis (Muricy & Diaz 2002). Plakinidae without skeleton, with thinly encrusting to lobate shape. Thin ectosome (<100 µm), often limited to pinacoderm; true cortex absent. Mesohyl poorly developed, with a proportion of mesohyl to chambers varying from 0.5: 1 to 1.2: 1. The aquiferous system has a sylleibid organization, with spherical, eurypylous choanocyte chambers uniformly arranged around large, regular exhalant canals, and a large basal cavity.Published as part of Ereskovsky, Alexander V., 2006, A new species of Oscarella (Demospongiae: Plakinidae) from the Western Sea of Japan, pp. 37-51 in Zootaxa 1376 on page 38, DOI: 10.5281/zenodo.17498

Transdifferentiation is a driving force of regeneration in Halisarca dujardini (Demospongiae, Porifera)

The ability to regenerate is widespread in the animal kingdom, but the regenerative capacities and mechanisms vary widely. To understand the evolutionary history of the diverse regeneration mechanisms, the regeneration processes must be studied in early-evolved metazoans in addition to the traditional bilaterian and cnidarian models. For this purpose, we have combined several microscopy techniques to study mechanisms of regeneration in the demosponge Halisarca dujardini. The objectives of this work are to detect the cells and morphogenetic processes involved in Halisarca regeneration. We show that in Halisarca there are three main sources of the new exopinacoderm during regeneration: choanocytes, archaeocytes and (rarely) endopinacocytes. Here we show that epithelial-to-mesenchymal transition (EMT) and mesenchymal-to-epithelial transition (MET) occur during Halisarca regeneration. EMT is the principal mechanism during the first stages of regeneration, soon after the injury. Epithelial cells from damaged and adjacent intact choanocyte chambers and aquiferous canals assume mesenchymal phenotype and migrate into the mesohyl. Together with archaeocytes, these cells form an undifferentiated cell mass beneath of wound, which we refer to as a blastema. After the blastema is formed, MET becomes the principal mechanism of regeneration. Altogether, we demonstrate that regeneration in demosponges involves a variety of processes utilized during regeneration in other animals (e.g., cell migration, dedifferentiation, blastema formation) and points to the particular importance of transdifferentiation in this process. Further studies will be needed to uncover the molecular mechanisms governing regeneration in sponges

proceedings of the First All-Russia Meeting of Spongiologists, St. Petersburg, February 1996

Contents ; List of Contributors ; Introduction ; I. General Problems of Sponge Biology. S. M. Efremova: Once more on the position among Metazoa - Gastrulation and germinal layers of sponges ; N. N. Marfenin: Sponges viewed in the light of up-to-date conception on coloniality ; A. V. Ereskovsky & G. P. Korotkova: The reasons of sponge sexual morphogenesis peculiarities II. Developmental Biology of Sponges. O. M. Ivanova-Kazas: Analysis of the sponges ontogeny at sexual reproduction ; R. P. Anakina: The cleavage specifity in embryos of the Barents Sea sponge Leucosolenia complicata Montagu (Calcispongiae, Calcaronea) ; L. V. Ivanova: New data about morphology and metamorphosis of the spongillid larvae (Porifera, Spongillidae). 1. Morphology of the free-swimming larvae ; L. V. Ivanova: New data about morphology and metamorphosis of the spongillid larvae (Porifera, Spongillidae). 2. The metamorphosis of the spongillid larvae ; L. V. Ivanova & V. V. Semenov: Feeding habits of the larvae of sponges ; N. A. Sizova & A. V. Ereskovsky: Ultrastructural peculiarities of the early embryogenesis in a White Sea sponge Halisarca dujardini (Demospongiae, Dendroceratida) ; III. Ecology of Sponges. R. P. Anakina & E. I. Slepian: Spiculas' malformations of freshwater sponges as indicators of water environment in St. Petersburg City ; A. S. Plotkin & A. V. Ereskovsky: Ecological aspects of asexual reproduction of the White Sea sponge Polymastia mammillaris (Demospongiae, Tetractinomorpha) in Kandalaksha Bay ; I. S. Smirnov & V. M. Koltun: Symbiosis of the antarctic sponge genus lophon (Porifera) and ophiuroid genus Ophiurolepis (Ophiuroidea, Echinodermata) ; IV. Palaeontology and Systematics. L. V. Bolshakova: Stromatoporoids - the fossil sponges ; E. V. Veinberg, 0. M. Khlystov, S. S. Vorobyova, E. G. Kornakova, 0. V. Levina, S. M. Efremova, & M. A. Grachev: Distribution of sponge spicules in sediments of the underwater Akademichesky ridge of Lake Baikal ; K. R. Tabachnik & C. Levi: Amphidiscophoran Hexasterophora (Part I & II) ;conferenceDFG, SUB Göttinge