Genetic   structure   of   the   high   dispersal   Atlanto-Mediterreanean   sea   star Astropecten aranciacus revealed by mitochondrial DNA sequences and microsatellite loci.

Marine Biology 156(4): 597-610

Abstract:

To investigate the impact of potential marine barriers on gene flow in high dispersal marine invertebrates, we assessed the population genetic structure of the sea star Astropecten aranciacus. Samples were obtained from nine locations within the Atlantic and the Mediterranean Sea including populations east of the Siculo-Tunisian Strait. We obtained both DNA sequence data of the mitochondrial control region and genotype data at four microsatellite loci. Both markers were highly polymorphic and showed a great level of genetic diversity. Genetic differentiation between populations (FST) was in general low, particularly for nuclear data, as is often the case in high dispersal marine invertebrates. Nevertheless, both marker sets indicated a significant genetic differentiation of the population from the island of Madeira to most other populations. Our results also demonstrate a clear pattern of isolation-by-distance supported by both mitochondrial and nuclear markers. Therefore, we conclude that larval dispersal of A. aranciacus is somewhat limited even within the basins of the Atlantic, the west Mediterranean and the east Mediterranean. Microsatellite loci further revealed genetic differentiation between the three basins; however, it is not clear whether this is truly caused by marine barriers. Genetic differentiation between basins might also be a result of isolation-by-distance allowing for any grouping to be significant as long as geographical neighbors are clustered together. Although levels of genetic differentiation were less pronounced in microsatellite data, both datasets were coherent and revealed similar patterns of genetic structure in A. aranciacus.

zulliger-biblio

Vorkommen von Astropecten aranciacus (Asteroidea, Echinodermata) in Abhängigkeit von Umweltbedingungen.

Environmental conditions affecting the occurrence of Astropecten aranciacus (Asteroidea, Echinodermata).

Helgoländer wissenschaftliche Meeresuntersuchungen 28: 167–182

Zusammenfassung:

1. Astropecten aranciacus L. ist die größte von sechs Arten der Gattung, die im Mittelmeer nachgewiesen sind. Dieser Seestern lebt auf Sedimentböden; die obere Grenze des Vorkommens findet sich auf etwa drei Meter Tiefe.
2. Auf 70 Stichprobenfeldern von je 25 m2 Fläche wurde die Individuenzahl von A. aranciacus zusammen mit biotischen und abiotischen Bedingungen registriert. Das Untersuchungsgebiet lag zwischen 3 und 10 m Tiefe.
3. Die statistische Datenauswertung ergab, daß die Abundanz von A. aranciacus mit zunehmender Tiefe und steigendem mittlerem Sandkorndurchmesser zunimmt. Von den biotischen Faktoren war die Anzahl Molluskenarten positiv, die Anzahl Echinocardien negativ mit der Abundanz von A. aranciacus korreliert.
4. Die Bestandesdichte von A. aranciacus schwankte in dem heterogenen, mosaikartig gegliederten Biotop zwischen 0 und 12 Individuen je 100 m2. Im Mittel entfielen auf 100 m² 4 Seesterne. Der Radius R der Tiere variierte zwischen 7 und 15 cm.
5. Die Makro-Infauna des Gebiets fiel durch geringe Abundanz auf. Bei den Mollusken betrug die durchschnittliche Bestandesdichte 36 Tiere pro m2. Dagegen war die Arten-Diversität groß: In Infaunenproben von gesamthaft 17,5 m2 Fläche fanden sich 37 Molluskenarten.

burla-biblio
    

On the coral-feeding habit of the sea star Peltaster placenta.

Marine Biodiversity 49: 2009–2012.

Abstract:

The predatory activity of the asteroid Peltaster placenta (Müller and Troschel, 1842) on the black coral Parantipathes larix (Esper, 1790) is here described for the first time based on video footage obtained during a Remotely Operated Underwater Vehicle (ROV) survey conducted in the Pontine Archipelago (Southern Tyrrhenian Sea, Mediterranean Sea). Feeding is carried out on the living coenenchyme of the basal axis and pinnules of the antipatharian and is confirmed by the occurrence of its cnidocysts in the sea star gut content. The chitinous skeletal parts of the black coral are left intact as bare tissue, which helps to relate colonies to the predation event. Among all black coral species present in the research area, P. placenta was observed grazing exclusively on P. larix, similarly to other goniasterids known to be deep-sea corallivores with a marked selectivity for their prey. The predatory behaviour of P. placenta was previously unknown. The extent of its feeding traces suggests a significant influence on benthic trophic relationships and, ultimately, on the functioning, structure and health status of deep Mediterranean black coral forests.

bo-biblio