Meiofauna y diversidad de nemátodos en algunas áreas submareales mediterráneas de los mares Adriático y Jónico

Sediments of three different subtidal areas (15-705 m depth) of the Italian coasts (Manfredonia, Brindisi and Gallipoli) were investigated to study meiofauna and nematode composition. The nematodes were identified to the genus level and their abundances compared using multivariate analysis. Our data showed an evident depth gradient in meiofauna abundance: the shallowest sites had more diverse and abundant meiobenthic communities than the deeper ones. Nematodes were the dominant taxon (83-100%) at all sites, followed by Copepoda (0.5-8%). Sabatieria, Astomonema, Dorylaimopsis, Terschellingia and Daptonema were among the dominant nematode genera in the three areas. Nematode genus H’ diversities were not significantly dissimilar, though at community level some differences were detected among the study areas. The greatest differences were observed in the comparison of the communities from Manfredonia and Gallipoli. Furthermore, there was a difference between shallow (<200 m) and deep sites due to high differential abundances of common genera, i.e. Astomonema, Dorylaimopsis, Sabatieria and Terschellingia.Los sedimentos de tres áreas submareales (15-705 m de profundidad) de la costa italiana (Manfredonia, Brindisi, Gallipoli) se investigaron para estudiar la meiofauna y composición de nemátodos. Los nemátodos se identificaron a nivel de género y sus abundancias se compararon usando análisis multivariantes. Nuestros datos mostraron un evidente gradiente de profundidad en la abundancia de la meiofauna: los lugares más someros tuvieron comunidades del meiobentos más diversas y abundantes que los más profundos. Los nemátodos fueron el taxon dominante (83-100%) en todos los lugares, seguido por los copépodos (0.5-8%). Sabatieria, Astomonema, Dorylaimopsis, Terschellingia y Daptonema fueron los géneros de nemátodos dominantes en las tres áreas. Las diversidades de géneros de nemátodos (H’) no fueron significativamente disimilares; incluso a nivel de comunidad se detectaron algunas diferencias entre areas de estudio. Las mayores diferencias se observaron cuando se compararon comunidades de Manfredonia y Gallipoli. Además, hubo diferencia entre sitios someros (<200 m) y profundos debido a las grandes diferencias en la abundancia de géneros comunes, i.e. Astomonema, Dorylaimopsis, Sabatieria, Terschellingia

Further studies on the marine tardigrade fauna from Sardinia (Italy)

An investigation on the taxonomy and ecology of marine tardigrades was carried out in different intertidal and subtidal sites along the coasts of Sardinia (Italy). Particle size analysis of sediments revealed medium or medium-fine intertidal sands and coarse subtidal sands, the latter mainly formed by coralligenous debris. The systematic study was particularly relevant, leading to the identification of 25 species, of which 9 are new records for Sardinia, and 2 are new to science. With these new findings, the total number of species for Sardinia adds up to 47. The species found belong to the families Halechiniscidae (16 species; abundance 2 to 263 ind. 10 cm-2), Batillipedidae (6 species; abundance 2 to 574 ind. 10 cm-2) and Stygarctidae (3 species; abundance 0 to 13 ind. 10 cm-2). The present data confirm the existence of a remarkable diversity, both of intertidal and subtidal tardigrade fauna. Generally, the prevalently siliceous intertidal sands host a few number of species (sometimes with many individuals), while the subtidal sediments, which were mainly calcareous, show a higher number of species often with low density. In fact, in the intertidal sediments only 11 species were found, 5 belonging to Halechiniscidae and 6 to Batillipedidae. In the subtidal sediments, there was a much wider variety; Halechiniscidae showed the highest number of species (16), compared to the remaining families, while Stygarctidae, which were present only in subtidal sediments, accounted only for 3 species. In the intertidal zone the highest value of the diversity index (H') was 2.1 and in the subtidal zone it was 3.3

The diversity of Indian Ocean Heterotardigrada

Information about Indian Ocean tardigrades is quite scarce and in most cases refers to species in coastal coralline sediment and occasionally in abyssal mud. The present data concern species found in the intertidal sand of Coco and La Digue Islands in the Seychelles, previously unsampled for tardigrades, as well as species in subtidal sediment found at depths ranging between 1 and 60 m off the shores of the Maldive Atolls. These sediments are all very similar and consist of heterogeneous coralline sand, moderately or scarcely sorted. Sixteen species (three new to science) were found in the Seychelles, belonging to Renaudarctidae, Stygarctidae, Halechiniscidae, Batillipedidae and Echiniscoididae. Diversity and evenness data are also interesting, with maximum values of H' = 2.59 and of J = 0.97. In the Maldives 25 species were found (two new to science) belonging to Neostygarctidae, Stygarctidae, Halechiniscidae and Batillipedidae. Such a number of species, despite the low percentage of tardigrade fauna (only 0.6% of the total meiofauna), contributes to the high values of both diversity and evenness, with H' ranging between 1.5 and 2.6 and J between 0.6 and 1. The Indian Ocean tardigrade fauna currently numbers 31 species of Arthrotardigrada and 2 species of Echiniscoidida. In the present study, Arthrotardigrada are the most abundant and all the families are present except Neoarctidae. Halechiniscidae is present with all the sub-families (except Euclavartinae), thus contributing to the high diversity values. Furthermore, 18 species, representing more than 50% of the total marine tardigrade fauna, are new records for the Indian Ocean, including five species new to science

Further studies on the marine tardigrade fauna from Sardinia (Italy)

An investigation on the taxonomy and ecology of marine tardigrades was carried out in different intertidal and subtidal sites along the coasts of Sardinia (Italy). Particle size analysis of sediments revealed medium or medium-fine intertidal sands and coarse subtidal sands, the latter mainly formed by coralligenous debris. The systematic study was particularly relevant, leading to the identification of 25 species, of which 9 are new records for Sardinia, and 2 are new to science. With these new findings, the total number of species for Sardinia adds up to 47. The species found belong to the families Halechiniscidae (16 species; abundance 2 to 263 ind. 10 cm-2), Batillipedidae (6 species; abundance 2 to 574 ind. 10 cm-2) and Stygarctidae (3 species; abundance 0 to 13 ind. 10 cm-2). The present data confirm the existence of a remarkable diversity, both of intertidal and subtidal tardigrade fauna. Generally, the prevalently siliceous intertidal sands host a few number of species (sometimes with many individuals), while the subtidal sediments, which were mainly calcareous, show a higher number of species often with low density. In fact, in the intertidal sediments only 11 species were found, 5 belonging to Halechiniscidae and 6 to Batillipedidae. In the subtidal sediments, there was a much wider variety; Halechiniscidae showed the highest number of species (16), compared to the remaining families, while Stygarctidae, which were present only in subtidal sediments, accounted only for 3 species. In the intertidal zone the highest value of the diversity index (H') was 2.1 and in the subtidal zone it was 3.3