Biologia riproduttiva di Paracentrotus lividus (Lamarck, 1816) in due zone della Sardegna

Paracentrotus lividus è un echinoderma bentonico marino appartenente alla classe Echinoidea, comune in tutto il Mar Mediterraneo e lungo le coste atlantiche dalla Scozia al Marocco. Questa specie è estremamente importante dal punto di vista ecologico in quanto specie chiave nella strutturazione della comunità bentonica macroalgale. Inoltre in tempi recenti il mercato delle sue gonadi ha subito una forte espansione rendendolo una specie di interesse economico in numerosi paesi europei. Il crescente prelievo sta gradualmente portando al depauperamento della risorsa, per questo motivo il riccio di mare è oggetto di numerosi studi e programmi a fini conservazionistici. Una maggiore conoscenza del ciclo riproduttivo della specie potrebbe risultare utile per una migliore gestione della risorsa. Pertanto, questo studio si propone di indagare sulla biologia di P. lividus in due aree distinte della Sardegna: Su Pallosu, nella Penisola del Sinis Sardegna centro-occidentale, e nell’Area Marina Protetta di Tavolara – Punta Coda Cavallo, Sardegna nordorientale, al fine di far luce sulle dinamiche del ciclo riproduttivo. Le informazioni bibliografiche a riguardo evidenziano l’influenza dei fattori ambientali quali fotoperiodo, idrodinamismo, temperatura e tipologia di pascolo sull’andamento del ciclo biologico e il momento di spawning. Diversi autori hanno osservato in Mar Mediterraneo sia un unico ciclo riproduttivo che due eventi riproduttivi annuali a conferma dell’ampia variabilità dell’andamento gonadico. Nel presente lavoro al fine di mettere in relazione le caratteristiche dell’habitat con il ciclo riproduttivo delle popolazioni in oggetto è stato analizzato l’andamento dell’Indice Gonadosomatico (IGS) su individui di diverse taglie/età, come rapporto fra il peso delle gonadi e il peso dell’individuo; inoltre a conferma dello stadio di maturazione è stata effettuata l’analisi istologica delle gonadi su campioni fissati e inclusi in paraffina, sezionati a 7μm e colorati con ematossilina-eosina prima di essere osservati al microscopio ottico. Mediante analisi d’immagine di foto subacquee utilizzando il programma Seascape è stata caratterizzata la componente macroalgale bentonica e la componente abiotica degli habitat (sabbia e roccia non vegetata) con particolare attenzione al calcolo della percentuale di ricoprimento delle specie vegetali. Inoltre i siti sono stati caratterizzati rispetto all’esposizione dei venti dominanti con elaborazione dei dati del periodo di campionamento per direzione, frequenza e intensità.

Characterization of sea urchin yolk glycoproteins

To study the fate of the yolk glycoproteins found in eggs and embryos of the sea urchin, S. purpuratus, a polyclonal antibody to a 90-kDa polymannose glycoprotein was prepared. lmmunoblot analysis of total proteins over the course of development showed that this antibody recognized a family of glycoproteins. Concomitant with the disappearance of the major 160-kDa egg yolk glycoprotein during embryogenesis, glycoproteins with a lower molecular mass appeared. These glycoproteins (115, 108, 90, 83, and 68 kDa) were purified and peptide mapping revealed that they were cleavage products derived from the major yolk glycoprotein. The antibody identified a homologous set of yolk glycoproteins with similar molecular masses in the embryos of three other species in the class Echinoidea: L. pictus, A. punctulata, and D. excentricus. However, eggs from other echinoderm classes and from chicken, frog, fruit fly, and nematode did not contain any cross-reactive molecules. Cross-reactivity within the class Echinoidea was not due to a common carbohydrate epitope, because the antibody recognized the glycoproteins even after the N-linked, polymannose carbohydrate side chains were enzymatically removed. The major yolk glycoprotein (160-170 kDa) from each of the three sea urchin species was purified and analyzed, revealing striking similarities in pI and in amino acid and monosaccharide composition. Peptide mapping showed that the 160-kDa glycoprotein from the four echinoids are structurally homologous. The major yolk glycoprotein appeared to be proteolyzed by a thiol protease, which could be activated in yolk particles prepared from unfertilized eggs by low pH. Immunolocalization by electron microscopy in S. purpuratus showed that the yolk glycoproteins remained within the yolk platelet throughout embryonic development, and that externalization of the glycoproteins was not detectable. The yolk glycoprotein precursor began to be synthesized in premetamorphosis larvae, and continued in adult males and females. Both the yolk glycoproteins and the yolk platelets disappeared during larval development. This disappearance has special significance because there were no yolk proteins in the direct developing sea urchin, H. erthryogramma, which bypasses larval development and metamorphoses directly into an adult. ^

Foraminifera and microfossil occurence in Late Jurassic sediments of the North and South Atlantic

Biostratigraphical, taxonomical, and palaeocological results were obtained from Oxfordian to Tithonian foraminifers of the Northern and Southern Atlantic Ocean boreholes of the DSDP Legs 1, 11, 36, 41, 44, 50, and 79. An oversight on the cored Jurassic sections of the DSDP Legs 79 and the corresponding foraminiferal descriptions are given. The reddish brown, clayey and carbonaceous Cat Gap Formation (Oxfordian to Tithonian) of the Northern Atlantic Ocean, rich in radiolarians, yields less or more uniform, in most cases allochthonous foraminiferal faunas of Central European shelf character. No Callovian and Upper Tithonian foraminiferaI zones can be established. The zone of Pseudomarssonella durnortieri covers the Oxfordian/Kimmeridgian, the zone of Neobulimina atlantica the Kimmeridgian/Lower Tithonian interval. Characteristic foraminiferal faunas are missing since the Upper Tithonian to Valanginian for reason of a widely distributed regression which caused hiatuses observed all over the Northern Atlantic Ocean and in parts of Europe. The Upper Jurassic cannot be subdivided into single stages by foraminiferal biostratigraphy alone. The fovaminiferal zones established by Moullad (1984) covering a Callovian-Tithonian interval may be of some local importance in the Tethyan realm: It has too long-ranging foraminiferal species to be used as index marker in the word-wide DSDP boreholes. Some taxonomical confusion is caused because in former publications some foraminiferal species have got different names both in the Jurassic and Cretaceous. The foraminiferal biostratigraphy of drilled sections from DSDP boreholes is restricted by the drilling technique and for palaeo-oceanographical, biological, and geological reasons. Foraminiferal faunas from the DSDP originally described as ,,bathyal, or ,,abyssal,, have to be derived from shallower water. This contrasts the palaeo-water depths of 3000-4000 m which result from sedimentological and palaeo-geographical investigations.

Biology community and bottom sediments in the West Bay of the Furugelm Island, Sea of Japan

An experiment was carried out on the soft bottom in the sublitoral zone of the Furugelm Island (Peter the Great Bay, Sea of Japan) to study formation of benthic communities. Boxes with defauned sediments were placed on depths of 4, 6 and 13 m and exposed during 60 days in the summer period. Half of them were covered with a net with mesh size 2 cm to prevent effect of large predators. It was found that spatial pattern of invertebrates' sinking in the bay conforms to distribution of benthic communities. Larvae of benthic invertebrates sinks in general in places inhabited by their adult species. The main factors responsible for recolonzation are: sediment type and local hydrodynamic conditions. Heart-shaped sea urchin Echinocardium cordatum is numerically dominated in the bay on depth 3-4.5 m, but its larvae sinks in the deeper area. Community structure is supported by mature specimen migration to places inhabited by species. Predators affect largely on the species.

Eocene/Oligocene paleoceanography from ODP Hole 113-689B and Hole 113-690B

Middle Eocene to Late Oligocene sediments from near the crest (Site 689B, water depth 2080 m) and flank (water depth 2914 m) of the Maud Rise (62°S) have been investigated by coarse fraction analysis and have revealed the following: (1) The middle Eocene (50-40 Ma) was a period of pure carbonate sedimentation, with good preservation of carbonate microfossils. No opal > 40 µm is present. (2) In the late Eocene (40-36.5 Ma) opal fossils (mainly radiolaria, and some diatoms > 40 µm) appeared for the first time. Three maxima in opal sedimentation (Eocene/Oligocene boundary, middle early Oligocene and early/late Oligocene boundary) are separated by increases in carbonate sedimentation. The dissolution of carbonate fossils is strong in the opal-rich layers. Opal sedimentation is attributed to cooling and probably more vigorous atmospheric circulation and increased upwelling. (3) Carbonate dissolution increased with water depth in the Oligocene, whereas in the middle Eocene excellent carbonate preservation in the deeper Site 690B and stronger dissolution in the shallower Site 689B is attributed to different bottom-water characteristics. The middle Eocene bottom water probably was formed by strong evaporation at low latitudes, whereas by the earliest Oligocene formation of Antarctic Bottom Water (AABW) had set in. (4) Current influence, not on top but on the flank of the Maud Rise, could be recorded by means of larger grain sizes of benthonic and planktonic microfossils. (5) Ice-rafted debris was not found. Quartz and other minerals are very rare and not larger than 125 µm and may have been supplied by ice as well as by wind or by deep currents. Mica contents were up to 10 times higher in the middle Eocene on the flank compared to on the crest of the Maud Rise, indicating deep current supply.

Benthic foraminifera in Lower Cretaceous sediments from various DSDP samples

From the DSDP Legs 1, 11, 13, 17, 25, 27, 32, 36, 41, 43, 44, 50, and 62 the Lower Cretaceous foraminifers have been investigated for biostratigraphical, taxonomical, and palaeoecological purposes. An overview of the cored Lower Cretaceous sections of Leg 1-80 is given. In the Northern Atlantic Ocean characteristic foraminiferal faunas are missing from the Upper Tithonian to the Valanginian due to a marked regression which caused hiatuses. In areas without black shale conditions Valanginian to Barremian medium rich to poor microfaunas with Praedorothia ouachensis (Sigal) of the Praedorothia ouachensis Zone (Valanginian-Hauterivian). The Hauterivian-Aptian interval is characterized by zones of Gavelinella barrerniana, Gaudryina dividens, and Conorotalites aptiensis. During the Albian a world-wide fauna consisting of agglutinated and calcareous foraminifers of the Pseudoclavulina gaultina Zone is established in areas lacking the wide-spread black-shale conditions. The Upper Albian and the Cenomanian are represented by the Gavelinella eenomanica Zone. Some ornamented species of the nodosariids (Citharina, Lenticulina), Gavelinella, Conorotatites, Pleurostomella, Vatvulineria, and Osangularia are of some importance for the biostratigraphy of the Berriasian-Albian interval. The Berriasian to Albian zones introduced for the Tethys and the DSDP by Moullade (1984) could only be of some local importance due to the long stratigraphical range of the foraminiferal species used. In the Indian Ocean an exact stratigraphical age cannot be assigned to the few Neocomian foraminiferal faunas of a cooler sea water (Site 261). These faunas mainly contain primitive agglutinated foraminifers, because in most cases the calcareous tests are dissolved or redeposited. In the Pacific Ocean most of the Berriasian to Aptian microfaunas are of minor biostratigraphical and palaeoecological importance for reasons of poor core recoveries, contaminations or original foraminiferal poverty (black shales). Since the Albian there are somewhat higher-diverse faunas of calcareous and agglutinated foraminifers with index species of the Pseudoclavulina gaultina Zone. As a rule, the boundary Albian/Cenomanian is set by means of planktonic foraminifers because no other foraminifer has its first appearance datum during this interval, except Gavelinella cenornanica. During the Albian very uniform, world-wide foraminiferal faunas without a marked provincialism are obvious.

Surface sediment analyses, bivalve and gastropod taxa of marine sediments from the Banc d'Arguin, Mauritania

High-nutrient tropical carbonate systems are known to produce sediments that, in terms of skeletal composition, are reminiscent of their extra-tropical counterparts. Such carbonate systems and associated carbonate grain assemblages in the tropics are rare in the present-day world. Nonetheless, it is crucial to gain a better understanding of those ecosystems, including their drivers and players because such settings potentially represent models for ancient depositional systems as well as for predicted future environmental conditions. One of the modern occurrences of eutrophic tropical carbonate systems is the northern Mauritanian Shelf. The marine environment is characterized by an eastern boundary upwelling system that pushes cool and nutrient-rich intermediate waters onto a wide epicontinental platform (Golfe d'Arguin) where the waters warm up to tropical temperatures. The resulting facies is mixed carbonate-siliciclastic with a dominant foramol association grading into bimol and barnamol grain assemblages in the shallowest areas forming the Banc d'Arguin. Besides this cool water-related heterozoan association, the carbonate sediment is characterized by tropical molluskan species, while chlorozoan biota (e.g., corals and algal symbiont-bearing foraminifers) are entirely absent. We here present a first comprehensive facies analysis of this model example of eutrophic tropical carbonates. Furthermore, we reconstruct the loci of carbonate production and provide a conclusive depositional model of the Banc d'Arguin that received little attention to date due to its poorly accessible nature.

Calcareous nannofossils and planktonic foraminifera of ODP Hole 132-810C

The 136 m of calcareous oozes recovered in Hole 810C span the interval from upper Maastrichtian to middle Pleistocene. Three major hiatuses interrupt the sequence, with the topmost part of the Maastrichtian through the entire lower Paleocene, most of the lower Eocene, and the entire middle Eocene through most of the middle Miocene missing. Severe reworking and displacement affected the lower part of the succession from the Maastrichtian through the middle Miocene. Reworking and displacement gradually decreased in the upper portion. Calcareous nannofossil biostratigraphy enabled us to calibrate precisely the nearly complete magnetic reversal sequence of the Pliocene to the late Pleistocene. Two minor hiatuses detected by calcareous nannofossils across the Pliocene/Pleistocene boundary and in the upper lower Pleistocene, respectively, resulted in shortening of the Olduvai and Jaramillo Events within the Matuyama Chron of the magnetic reversal sequence.

Biogenic and mineral composition and foraminiferal stratigraphy of sediment cores obtained in northern Germany

The Ratekau boring ended in clays of the so-called Asterigerina-Zone; these clays have shallow-water features in the uppermost samples. The clays are overlain by deep-water clays with pteropods; this formation is split into two parts by a shallow-water deposit. The fossiliferous series ends upward in sandy deposits with shallow-water fossils. The question is raised whether the two deep-water deposits might correspond to the Lower Doberg Beds (Eochattian) and the Upper Doberg Beds (Neochattian) at the Doberg hill, closer to the rim of the basin. All fossiliferous samples from this boring are thought to be of Late Oligocene age; the boundary towards the Middle Oligocene, however, could not be ascertained. The Vaale boring ended in rather typical Septaria clay of the Middle Oligocene. This clay is capped by some metres of unfossiliferous glauconite clays, which in turn are overlain by silts and silty clays with planktonic fossils identical to those found at Dingden locality. These deposits are tentatively dated as Early Miocene. The next higher series of samples consists of sands and clays deposited in shallower waters. They contain a rich fauna of benthic molluscs, which, according to the current notion in stratigraphy, would have a Reinbek Age. In addition, they contain a set of planktonic fossils which differs from the 'Lower Miocene' assemblages. These sands and clays are overlain by a thick series of marine sands very poor in fossils. Finally, four metres of clay with foraminifera, having Younger Miocene affinities, form the top of the fossiliferous sequence. The borings at Wulksfelde and Langenhorn were not far apart and their sediments are easily correlated. Both wells start below in continental 'Lignite Sands' and contain overlying shallow water sands and clays. These yielded Hemmoor benthic mollusca, supposed to indicate Lower Miocene in the relevant literature; however, we encountered their planktonic foraminifera in the uppermost Miocene as well. The same planktonic species were found in all samples of both borings. These deposits under discussion furthermore contain a particular pteropod species. They are overlain by a thick series of gypsiferous clays, with scarce fossils. The uppermost fossiliferous clays (probably Langenfelde Age) contain another pteropod species, not met with in other samples. The discrepancies between the plankton zonation and the traditional subdivision according to benthic molluscs in the borings of Vaale, Wulksfelde and Langenhorn (and in samples from Twistringen, Dingden and Antwerp localities as well) renders the time-stratigraphic value of the denominations Reinbek and Hemmoor rather doubtful. The samples of the Westerland boring can be placed in the Gram and Sylt stages of local chronostratigraphy on the strength of the Astarte series established by HINSCH. The Gram samples contain a typical pteropod species; both groups of samples contain the same planktonic foraminifera as the borings Wulksfelde and Langenhorn. Our material did not bring the problem of the Miocene-Pliocene boundary in this region any closer to a solution. In conclusion, it can be claimed that this investigation provides strong arguments that the usual recognition of Hemmoor and Reinbek does not correspond to well-defined chronostratigraphical units. A better chronostratigraphic subdivision has to be based on the examination of many more samples, and on a better understanding of the paleoecology of the fossils involved.

Pelagic, turbiditic, and contouritic sequential deposits on the Cape Verde Plateau

On the Cape Verde Plateau, Neogene deposits are composed of major pelagic and hemipelagic sediments. These sediments show climatic sequences composed of two lithologic terms that differ in their siliciclastic and carbonate contents. Several turbiditic and contouritic sequences are interbedded in these deposits. Turbidite sequences are fine grained and thin bedded with a very low frequency (about 12 sequences during the Neogene). They are composed of quartz-rich siliciclastic or volcaniclastic sediments. Quartz-rich turbidites originated from the Senegalese margin. Their slightly higher frequency during the early Pliocene indicates that the stronger turbidity currents, and probably the most abundant continental inputs, occur at that period. Volcaniclastic turbidites are only present in the early Miocene (about 17 Ma) and the early Pleistocene (1 Ma). They have flown from adjacent Cape Verde Islands and reflect two episodes of high volcanic activity in this area. Contourite sequences, composed of biogenic sandy silts, represent less than 5% of the sediment pile and seem to have been mainly deposited during the late Pleistocene. These different sequences show clay mineral variations throughout Neogene time. Kaolinite is predominant in the Miocene and lower Pliocene deposits; this mineral decreases thereafter, with an increased trend of illite in the uppermost Pliocene and Pleistocene sediments, suggesting a change in sediment sources on the Saharan continent at about 2.6 Ma.

Food composition of beryx-alfonsino over submarine rises near Azores

Qualitative and quantitative food composition, as well as intensity of feeding of beryx-alfonsino Beryx splendens was examined on banks near the Azores. Data are presented with respect to size groups and taking into account type of feeding of males and females. Crustaceans and fishes were constituents of their feeding ration. A tendency toward increase in the number of consumed fishes in the course of ontogenetic development of beryx-alfonsino was noted. Beryx-alfonsino was shown to occupy the trophic level of consumers of the third order performing function of a deep-water predator.

Results of biological and geological bottom investigations carried out during Cruise 43 of R/V Akademik Kurchatov in the South Atlantic

The book is devoted to investigations of benthic fauna and geology of the Southern Atlantic Ocean. These works have been carried out in terms of exploring biological structure of the ocean and are of great importance for development of this fundamental problem. They are based on material collected during Cruise 43 of R/V Akademik Kurchatov in 1985-1986 and Cruise 43 of R/V Dmitry Mendeleev in 1989. Problems of quantitative distribution, group composition and trophic structure of benthos in the Southern Scotia Sea, along the east-west Transatlantic section along 31°30'S, and offshore Namibia in the area of the Benguela upwelling are under consideration in the book. Authors present new data on fauna of several groups of deep-sea bottom animals and their zoogeography. Much attention is paid to analysis of morphological structure of the Scotia Sea floor considered in terms of plate tectonics. Bottom sediments along the Transatlantic section and facial variation of sediments in the area of South Shetland Islands and of the continental margin of Namibia are under consideration.

Composition of sediments from the north-west African continental margin

Entlang dreier Profile vom NW-afrikanischen Kontinentalrand wurden Oberflächensedimente aus Wassertiefen zwischen 39m und 1514m auf ihre Zusammensetzung der Sandfraktion, auf ihre Gehalte an Karbonat und organischer Substanzen sowie auf ihre mineralogische Zusammensetzung hin untersucht. 1) Die auf dem Schelf und dem oberen Hang abgelagerten Sedimente (<500m) zeichnen sich durch hohe Sandgehalte (>70%) und durch hohe Grob/Fein-Verhältnisse aus. Unterhalb dieses Bereiches nimmt der Einfluß von Strömungen, die die Ablagerung von wesentlichen Mengen an Feinmaterial oberhalb 500m verhindern, ab, wie die starke Abnahme des Sandgehaltes, des Quarz/Glimmer und des Grob/Fein-Verhältnisses zeigen. Die Sedimente aus diesen Wassertiefen werden zum großen Teil aus Partikeln der Siltfraktion aufgebaut. Mit zunehmender Tiefe ist auch eine Zunahme der Tonfraktion zu beobachten, wobei höhere Tonanteile (>10%) erst in Tiefen unterhalb von 1200m auftreten. 2) Die quantitative Komponentenanalyse der Sandfraktion zeigt, daß der karbonatische Anteil fast ausschließlich biogener Herkunft ist. Er besteht zum wesentlichen Teil aus planktonischen Komponenten, vorwiegend Foraminiferen und mengenmäßig nur sehr untergeordnet auftretenden Pteropoden. Das opalkieselige Plankton (Diatomeen, Radiolarien) ist nur in geringen Mengen in den untersuchten Proben vorhanden. Auch das Benthos stellt nur eine untergeordnete Komponente der Sandfraktion dar. Vor allem der Anteil von Foraminiferen und Mollusken nimmt mit zunehmender Wassertiefe relativ deutlich ab. Die übrigen benthonischen Komponenten sind im Sediment nur in geringen Anteilen vertreten. 3) Hauptsedimentbildner im Profil Nouakchott sind die nichtbiogenen, terrigen-detritischen Sandkomponenten. Sie bestehen vorwiegend aus Quarz und mit zunehmender Wassertiefe aus Kotpillen bzw. Kotpillenaggregaten. Je nach Tiefe treten vor allem Glimmer (>1000m) und Glaukonit (<800m) hinzu. Die restlichen Komponenten treten nur gelegentlich und in äußerst geringen Mengen im rezenten Oberflächensediment auf. 4) Quarz wird als Windstaub mit dem NE-Passat und vor allem durch den "Harmattan" aus der Sahara heraustransportiert und vorwiegend über dem Schelfbereich sedimentiert. Windstaubmaterial besteht primär weitgehend aus Siltkorngrößen, die vor Nouakchott über die Schelfkante hinaustransportiert werden und zu einer Grobsiltanreicherung am mittleren Hang führen. 5) Das Verhältnis zwischen den karbonatischen Biogenkomponenten und den nichtbiogenen Partikeln spiegelt sich deutlich in der Karbonatverteilung sowohl des Gesamtsedimentes als auch der Sandfraktion wider. Relativ hohe Karbonatgehalte vor Cap Leven im Norden stehen sehr geringen Anteilen von Nouakchott gegenüber. Mit zunehmender Wassertiefe ist eine deutliche Abnahme des Karbonatanteils zu verfolgen. 6) Die Tatsache, daß das Profil Cap Blanc im Bereich des ganzjährigen Auftriebs liegt, spiegelt sich nicht in der Zusammensetzung der Sandfraktion wider. Südlich der Zone des ganzjährigen Auftriebs weisen verschiedene Parameter (Radiolarien, Diatomeen, Verhältnis von Radiolarien zu planktonischen Foraminiferen, Benthos/Plankton-Verhältnis der Foraminiferen) trotz abnehmender Auftriebsintensität eher steigende Werte auf. Dies ist wesentlich auf eine infolge des Nährstoffeintrages durch Flußzufuhr bedingte Verschiebung der maximalen Primärproduktion weit in südliche Richtung zurückzuführen. 7) In den aufgeführten Parametern zeigen sich von Profil zu Profil sehr deutliche fazielle Unterschiede, obwohl der großklimatische Hintergrund im gesamten Untersuchungsgebiet etwa gleich ist. Vor Cap Leven bildet sich eine Fazies, die im wesentlichen aus planktonischen Foraminiferen besteht, während das Sediment vor Nouakchott zum überwiegenden Teil aus nichtbiogenen Komponenten aufgebaut wird. Im Übergangsbereich vor Cap Blanc bildet sich eine Mischfazies, die keinerlei Prägung durch das Auftriebsgeschehen erhält. Die Ursachen dieser faziellen Unterschiede werden auf fehlenden Terrigeneinfluß vor Cap Leven einerseits und hohe Terrigenanlieferung vor Nouakchott andererseits zurückgeführt. 8) Die Zusammensetzung und Verteilung der rezenten Grobfraktionssedimente am Kontinentalrand vor Nw-Afrika wird somit im wesentlichen als Ergebnis einer Überprägung der Biogenanlieferung durch nichtbiogene Komponenten angesehen. Wesentlicher steuernder Faktor ist demnach das hier vorherrschende Windsystem.