Mollusca from a species-rich deep-water <em>Leptometra</em> community in the Alboran Sea

Abstract

Summary: An exceptional species richness for Mollusca was found on Avempace bank (349-365 m), Djibouti group, Alboran Sea, where the most abundant species was the crinoid Leptometra phalangium. A sample of sediment sieved on a 0.5-mm mesh yielded 156 species of molluscs (83 live-taken, 1772 specimens) with a high Shannon-Wiener diversity index (H' (log2) =3.60). The dominant mollusc was Limopsis aurita and the six most common species accounted for 77% of the specimens. On the other hand, 42 species were represented by only one or two specimens. Two species are described as new, three more are first findings in the Mediterranean and two are first findings in Iberian waters. One-third of the species have not been reported from the neighbouring, well-explored Alboran Island platform. There is a considerable balance between the trophic groups, denoting a stable and structured community. Most of the species have an extensive Atlantic range, and most have a planktonic larval stage. Therefore, it can be hypothesized that the fauna benefits from a diverse influx of larvae carried in by the more superficial incoming Atlantic current. Because of its exceptional richness, this type of bathyal community with Leptometra and Limopsis should be considered a high priority for habitat conservation in the Mediterranean deep sea.Keywords: species diversity; taxonomy; dominant species; trophic structure; geographical distribution; bathyal zone; Leptometra phalangium; marine molluscs. Moluscos de una comunidad profunda de Leptometra rica en especies en el mar de AlboránResumen: Se encontró una excepcional riqueza específica de moluscos en el banco Avempace (349-365 m), grupo de Djibouti, mar de Alborán, donde la especie más abundante fue el crinoideo Leptometra phalangium. En una muestra de sedimento tamizada sobre una malla de 0.5 mm se hallaron 156 especies de moluscos (83 con ejemplares vivos) y 1772 ejemplares, con un alto valor del índice de diversidad Shannon-Wiener (H' (log2) =3.60). El molusco dominante era Limopsis aurita y las seis especies más comunes eran el 77% de los ejemplares. Por otro lado, 42 especies estuvieron representadas únicamente por uno o dos ejemplares. Dos especies se describen como nuevas; tres más son primera cita para el Mediterráneo y dos son primera cita en aguas ibéricas. Un tercio de las especies no están citadas en la plataforma de la vecina isla de Alborán, por su parte bastante estudiada. La representación de los distintos grupos tróficos es equilibrada, denotando una comunidad estable y estructurada. La mayoría de las especies tienen una amplia distribución en el Atlántico y una fase larvaria planctónica. Por lo tanto se supone que la fauna se beneficia de un aporte diverso de larvas por la corriente superficial que entra desde el Atlántico. Por su excepcional riqueza, este tipo de comunidad batial con Leptometra y Limopsis merece considerarse prioritaria para la conservación de hábitats profundos del mar Mediterráneo.Palabras clave: diversidad especifica; taxonomía; especies dominantes; estruc...

Molluscs from benthic habitats of the Gazul mud volcano (Gulf of Cádiz)

“…The species richness of Gazul is also much higher than those 18 species of molluscs found by Olu-Le Roy et al (2004) in five MVs from the eastern Mediterranean or by Ritt et al (2012) in the Mediterranean Ridge area (Napoli and Amsterdam MVs), where they found a total of 19 taxa of molluscs but only 10 to species level. Comparable species richness values have been observed in other deep areas of the southern Iberian Peninsula, such as the Djibouti bank (Gofas et al 2014) and the Alboran Island platform (Peñas et al 2006), both in the Alboran Sea, which have high species richness compared with other studied bathyal zones of the Mediterranean Sea (Negri and Corselli 2016) or the North Atlantic Ocean (Bergquist et al 2003, Henry andRoberts 2007). Furthermore, additional species are known to occur on the Gazul MV, such as those captured by the fishing fleet on adjacent bottoms (e.g.…”

“…This also explains the differences found between the malacofauna associated with the MV edifice, and those of the erosive depression and of the adjacent bottoms, with the highest Shannon-Wiener diversity values and evenness observed on the MV edifice (Table 4). In this respect, the Gazul MV functions as a small seamount, and this may explain the large proportion of species shared with the Djibouti Bank in the Alboran Sea (Gofas et al 2014), where 156 species of molluscs were identified from only one haul collected with beam-trawl at 349 to 365 m depth, and more than half of these species (86 spp.) are shared with the Gazul MV.…”

Syllidae (Annelida: Phyllodocida) from the deep Mediterranean Sea, with the description of three new species

“…This is particularly true for the assemblage composition and species diversity of several groups of benthic invertebrates (Danovaro et al 2010). Most taxonomic studies focused on molluscs (Bouchet & Taviani 1992;Koutsoubas et al 2000;La Perna 2004;Gofas et al 2014) and nematodes (Soetaert et al 1995;Danovaro et al 2009), while the few available studies dealing with polychaetes usually report their diversity at supra-specific level, focusing on ecology and avoiding taxonomic considerations (Mamouridis et al 2011;Baldrighi et al 2013;Romano et al 2013;Baldrighi et al 2014). The Syllidae (Annelida: Phyllodocida) often represent a major faunal component in hard bottom assemblages and are one of the most diverse polychaete families in shallow water ecosystems (Musco & Giangrande 2005;Musco 2012).…”

The unknown bathyal of the Canaries: new species and new records of deep-sea Mollusca

“…reMArks The occurrence of this species, originally described from British waters, had so far been ascertained as far south as the Alboran Sea (Gofas et al 2014). New record for the Canaries.…”

“…MAteriAl exAMined. -1 sh., DW120; 2 sh., DW130.reMArk An amphiatlantic species, originally described from the Florida Straits in 205 fathoms, so far known also from the Cape Verde Islands and from the western Mediterranean(Gofas et al 2014). New record for the Canaries.…”