Search publications of the members of the Royal Belgian institute of natural Sciences
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Hypercalcified Extant and Fossil Chaetetid-Type and Post-Devonian Stromatoporoid-Type Demospongiae: Systematic Descriptions
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Five New Species of Homoscleromorpha (Porifera) from the Caribbean Sea
- Five new species of Homoscleromorpha (Porifera) of four genera, Oscarella, Plakortis, Plakina and Corticium, are described from vertical walls of reef caves at depths ranging from 23 to 28 m in the Caribbean Sea. Oscarella nathaliae sp. nov. has a leaf-like thinly encrusting, flat body, loosely attached to the substrate and a perforated, not lobate surface. Oscarella nathaliae sp. nov. contains two bacterial morphotypes and is characterized by two mesohylar cell types with inclusions. Plakortis myrae sp. nov. has diods of two categories: abundant large ones (83–119 mm long) and rare small ones (67–71 mm long) with sinuous, S-bent centres; triods Y- or T-shaped (18–5 mm long), and abundant microrhabds (5–12 mm long). Plakortis edwardsi sp. nov. has diods of one category with thick, sinuous, S-bent centres (110 to 128 mm long); triods T-shaped (actines 28–59 mm long). It is the only species of this genus showing small diods (22–31 mm long). Plakortis dariae sp. nov. has diods of two categories: large ones (67–112 mm long) and small, rare, irregular ones, slightly curved, often deformed with one end blunt (30–59 mm long); triods rare and regular (actines 20–44 mm long long). Corticium diamantense sp. nov. has oscula situated near its border, regular non-lophose calthrops of one size class, very rare tetralophose calthrops and candelabra with the fourth actine ramified basally in 4–5 microspined rays. In addition, a re-description of Plakina jamaicensis Lehnert & van Soest 1998 is based on newly collected material and the type specimen. P. jamaicensis has a convoluted brainlike surface; well developed sub-ectosomal cavities; irregular sinuous diods, triods, calthrops, rare monolophose calthrops, rare dilophose calthrops, rare trilophose calthrops and common tetralophose calthrops. Molecular ‘barcoding’ sequences for mitochondrial cob are given for Plakortis edwardsi sp. nov., P. dariae sp. nov., Plakina jamaicensis and Corticium diamantense sp. nov. An identification key for all western Atlantic Homoscleromorpha is provided.
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Multi-scale Mineralogical Characterization of the Mediterranean Hypercalcified Sponge Petrobiona massiliana (Porifera, Calcarea, Calcaronea)
- The massive basal skeleton of a few remnant living hypercalcified sponges rediscovered since the 1960s are valuable representatives of ancient calcium carbonate biomineralization mechanisms in basal Metazoa. A multi-scale mineralogical characterization of the easily accessible Mediterranean living hypercalcified sponge belonging to Calcarea, Petrobiona massiliana (Vacelet and Lévi, 1958), was conducted. Oriented observations in light and electron microscopy of mature and growing areas of the Mg-calcite basal skeleton were combined in order to describe all structural levels from the submicronic to the macroscopic scale. The smallest units produced are ca. 50–100 nm grains that are in a mushy amorphous state before their crystallization. Selected area electron diffraction (SAED) further demonstrated that submicronic grains are assembled into crystallographically coherent clusters or fibers, the latter are even laterally associated into single-crystal bundles. A model of crystallization propagation through amorphous submicronic granular units is proposed to explain the formation of coherent micron-scale structural units. Finally, XRD and EELS analyses highlighted, respectively, inter-individual variation of skeletal Mg contents and heterogeneous spatial distribution of Ca ions in skeletal fibers. All mineralogical features presented here cannot be explained by classical inorganic crystallization principles in super-saturated solutions, but rather underlined a highly biologically regulated formation of the basal skeleton. This study extending recent observations on corals, mollusk and echinoderms confirms that occurrence of submicronic granular units and a possible transient amorphous precursor phase in calcium carbonate skeletons is a common biomineralization strategy already selected by basal metazoans.
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Seasonal modifications and morphogenesis of the hypercalcified sponge Petrobiona massiliana (Calcarea, Calcaronea)
- The periodicity of sexual elements and soft tissue modifications during the life cycle of the hypercalcified sponge Petrobiona massiliana was investigated monthly from June 2006 to November 2007. Sexual reproduction, likely regulated by seawater temperatures, occurred during more than half of the year (from early April to late October); 70% of the samples appeared reproductively active. Specimens of P. massiliana displayed a high plasticity of tissue organization, allowing modulation and rearrangement of their aquiferous systems in response to life cycle phases and environmental changes. Permanent changes were observed in the basal region of the choanosome in non-reproductive specimens, such as disorganization/ restructuring events leading to remodeling of the aquiferous system. Periodic modifications occurring during sexual reproduction included the transformation of choanocytes from a typical form to hourglass and vespiform shapes, and more global disorganization of the basal region of the choanosome during provisioning of oocytes and embryos, followed by restructuring after release of the larvae. Finally, episodic disorganization/reorganization phenomena occurred in a few specimens after unfavorable environmental conditions (e.g., decreasing seawater temperatures). Histological and ultrastructural observations of storage cells, located in peculiar trabecular tracts, suggest a transdifferentiation capacity that allows such soft tissue dynamics.
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A new Clathria (Demospongiae, Microcionidae) from Peru occurring on rocky substrates as well as epibiontic on Eucidaris thouarsii sea urchins
- Southeastern Pacific sponges (Phylum Porifera) range among the world’s least known faunas, with only 13 species reported to date from the entire Peruvian coast. This state of affairs motivated the onset of two large, cooperative, exploratory initiatives, with the aim of mapping sponge richness and distribution in the area: Proyectos ESPER and EsponjAS. Over 800 specimens have been collected in Peru since 2007, with identifications still in progress. Among these, a sponge species originally thought to be an exclusive epibiont on Eucidaris thouarsii sea urchins, relatively conspicuous on Peru’s Punta Sal region. This sponge, latter found to occur on additional substrates too, is described as a new species of Clathria (Microciona). Cidarid density ranged between 1.5 and 12/m2, and largest diameter of the tests between 3.2 and 5.6 cm. Total number of spines on each sea urchin varied between 68 and 96, and percent sponge coverage of these, between 18.2 and 75.7. There appears to be only a slight tendency for increased sponge coverage on larger sea urchins, so there may be factors, other than sea urchin age, shaping this association. Clathria (Microciona) aculeofila sp. nov. can be markedly dominant as an epibiont on E. thouarsii, albeit the great sponge richness in the area. This is in contrast to the allegedly opportunistic, diverse epibiosis by sponges reported previously for Antarctic cidaroids.
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Introduction to Living Hypercalcified Sponges
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Temperature, salinity and growth rate dependences of Mg/Ca and Sr/Ca ratios of the skeleton of the sea urchin Paracentrotus lividus (Lamarck): an experimental approach
- The skeletal Mg/Ca ratio of echinoderms is known to increase with temperature but the relation has never been established in controlled experimental conditions. The present study investigated the eVect of temperature, salinity and growth rate on Mg/Ca and Sr/Ca ratios in calcite skeletons of juvenile sea urchins grown in experimental conditions. Mg/Ca ratio was positively related to temperature, increasing until a plateau at high but Weld occurring temperatures. It was not linked to salinity nor growth rate. We suggest that this plateau is due to properties of the organic matrix of mineralization and recommend to take it into account for the use of Mg/Ca as proxy of seawater Mg/Ca. Skeletal Sr/Ca ratio was mainly dependent on temperature and growth rate, as usually observed in calcite skeletons.
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Growth rate and chemical features of the massive calcium carbonate skeleton of Petrobiona massiliana (Baeriida: Calcaronea: Calcispongiae)
- In addition to the spicules typically produced by sponges, about twenty hypercalcified species belonging to both classes Demospongiae and Calcispongiae secrete a massive basal calcareous skeleton composed of calcite or aragonite. Skeletal growth rates and growth mechanisms are still poorly known in those hypercalcified Calcispongiae. In situ calcein staining experimentation on the Mediterranean calcisponge Petrobiona massiliana revealed a mean annual growth rate of the massive skeleton of 236 mm/y (+90). Scanning electron microscopy (SEM) revealed that some spicules are entrapped within the massive skeleton (a solid mass forming apical crests with multidirectional growth axes) during its formation. Whole actines were observed within the massive skeleton of fractured specimens, indicating that they do not dissolve after entrapping. Calcein incorporation bands seen through epifluorescence microscopy and SEM morphological observations of the skeletal surface revealed cone shaped protuberances corresponding to active growth areas. A spatially discontinuous growth was highlighted, but the annual growth rates were similar at the tip of crests and at the bottom of depressions separating them. The skeleton of P. massiliana is composed of magnesium calcite with strontium as the main trace element. Significant differences in skeletal chemistry of specimens collected in different Mediterranean locations revealed a possible temperature dependence of Mg/Ca. Although such temperature signature exists in the massive skeleton of P. massiliana, its use as an accurate environmental recorder is limited by several factors including multidirectional and spatially discontinuous growth.
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Taking care of the sea.
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DNA barcoding reveals new insights into the diversity of Antarctic species of Orchomene sensu lato (Crustacea: Amphipoda: Lysianassoidea)
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Bizarre fossil beaked whales (Odontoceti, Ziphiidae) fished from the Atlantic Ocean floor off the Iberian Peninsula
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The most basal beaked whale Ninoziphius platyrostris Muizon, 1983: clues on the evolutionary history of the family Ziphiidae (Cetacea: Odontoceti)
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EuroGeoSurveys – 34th General Assembly. Geological Excursion along the Meuse River between Namur and Dinant - 21.03.2013 - Guidebook
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Excursie Brussel - Natuursteen van de middeleeuwen tot de 20ste eeuw.
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On the genus Halirages (Crustacea, Amphipoda), with the description of two new species from Scandinavia and Arctic Europe
- A new common deep-sea species of Halirages Boeck, 1871 closely related to H. qvadridentatus G.O. Sars, 1877, H. cainae sp. nov., is described after specimens collected in the Norwegian Sea during the MAREANO 2009-111 cruise. Examination of the syntypes of H. elegans Norman, 1882 demonstrates that Norman's species is a junior synonym of H. qvadridentatus G.O. Sars, 1877 and that the species usually named H. elegans in literature was actually undescribed. The name H. stappersi sp. nov. is proposed for that species. A key to and a checklist of Halirages species is given.
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The genus Liljeborgia in the Mediterranean Sea, with the description of a new species (Crustacea: Amphipoda: Liljeborgiidae)
- A new amphipod crustacean, Liljeborgia clytaemnestra sp. nov., is described based on specimens from Malta and the Bay of Naples. It is quite similar to the sympatric L. dellavallei Stebbing, 1906, but it has narrower and more regular-sized spines on the propodus of pereiopods 3–4. The longest spine on the dorsolateral border of the peduncle of uropod 1 is not strongly elongate in adult males, as in L. dellavallei. The apical spines on the lobes of the telson are much longer than in L. dellavallei. L. clytaemnestra sp. nov. is actually more similar to two northeastern Atlantic species, the British L. pallida (Spence Bate, 1857) and the Scandinavian L. brevicornis (Bruzelius, 1859) than to the Mediterranean L. dellavallei. In L. clytaemnestra sp. nov., article 2 of the mandibular palp has setae on distal third, whilst setae are restricted to tip in the two other species. Article 3 of the mandibular palp is also longer in L. clytaemnestra sp. nov. than in the two Atlantic species. The spines of the outer plate of the maxilliped are longer in L. clytaemnestra sp. nov. than in the two other species. The most distal spine of the propodus of pereiopods 3–4 is reduced in L. clytaemnestra sp. nov. and L. brevicornis, but not in L. pallida. The serration of the posterior border of the basis of pereiopod 7 is much stronger in L. clytaemnestra sp. nov. than in the two other species. Finally, in L. clytaemnestra sp. nov., the spines of the lobes of the telson are longer than in L. pallida. A lectotype is designated for L. dellavallei. The presence/absence of a posterodorsal tooth on pleonite 3 in L. dellavallei is discussed. The validity of L. kinahani (Spence Bate, 1862) is questioned. An identification key is proposed for Mediterranean Liljeborgia species.
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Two new Pseudorchomene species from the Southern Ocean, with phylogenetic remarks on the genus and related species (Crustacea: Amphipoda: Lysianassoidea: Lysianassidae: Tryphosinae)
- Two new lysianassoid amphipods of the genus Pseudorchomene Schellenberg, 1926 from the Southern Ocean are described: P. debroyeri sp. n. collected in baited traps deployed around the Falkland Islands, Burdwood Bank and Îles Kerguelen between 55 and 470 m, and P. lophorachis sp. n. collected in baited traps and Agassiz trawls deployed in the Scotia and Weddell Seas at depths between 847 and 1943 m. P. lophorachis sp. n. is characterized by an strongly elongated first gnathopod and by the occurrence of low posterodorsal humps on the body segments. P. debroyeri sp. n. is very similar to P. coatsi (Chilton, 1912) but exhibits slight differences of proportions in the articles of gnathopods 1 and 2, more spines on pereopods and more acute spines on the propodus of pereopods 3–7. Molecular data indicate the existence of a welldefined clade comprising P. lophorachis sp. n., P. debroyeri sp. n., P. coatsi (Chilton, 1912), Abyssorchomene plebs (Hurley, 1965) and A. rossi (Walker, 1903). On the other hand, A. plebs and A. rossi do not form a clade with A. chevreuxi (Stebbing, 1906), which is the type species of the genus Abyssorchomene De Broyer, 1984. The definition of Pseudorchomene is amended, so that it now includes P. coatsi, P. debroyeri, P. lophorachis, P. plebs and P. rossi. The triangular coxa 1 in these 5 species is unique for ‘orchomenid’ lysianassoids, thus considered as a putative synapomorphy. P. coatsi (Antarctic species) is morphologically extremely similar to P. debroyeri (sub-Antarctic species) but it is genetically closer to the morphologically distinct P. lophorachis (Antarctic species). Hypotheses for these recent speciations and the morphological evolution within Pseudorchomene are discussed. The type species and the nomenclatural history of the genus Tryphosa Boeck, 1871, which is the type genus of the subfamily Tryphosinae, are discussed.
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Voortplantende populatie van de Purperslak Nucella lapillus in Belgie na meer dan 30 jaar afwezigheid (Mollusca, Gastropoda, Muricidae)
- In the past, the dog whelk Nucella lapillus (Mollusca, Gastropoda, Muricidae) used to be a common species on jetties and groynes along the Belgian coast. During the seventies, the species became increasingly rare and the last Belgian specimen observed in situ was found in 1981. The extinction of the species is attributed to the use of paintings containing tributyltin (TBT) on the hulls of ships as antifouling protection. TBT dilutes in seawater and, even at extremely low concentration, sterilizes dog whelks. Since 1990, the use of Tributyltin (TBT) was restricted to ships smaller than 25 m; in 2003, it was totally forbidden and in 2008 old TBT paintings had to be removed from ship hulls. As a consequence the concentration in TBT of seawater presumably decreased in Belgian waters. On November 17th, 2012, several living adult dog whelks and 40 to 50 spawns ofthat species were observed on the concrete blocks of the western jetty of Zeebrugge harbour, indicating recolonization of the species in Belgium at least in one locality.
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Exploring species level taxonomy and species delimitation methods in the facultatively self-fertilizing land snail genus Rumina (Gastropoda: Pulmonata)
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Yaratılışçılığın çürütülmesine taksonomi katkısı Harun Yahya’nın çakma fosilleri
