Walking with worms: coral‐associated epifaunal nematodes

Abstract

To study the community structure and habitat preferences of the Epsilonematidae and Draconematidae in coral degradation zones. To assess the contribution of different localities and microhabitats to meiobenthic diversity in such ecosystems. To discuss dispersive capacities and the occurrence of cryptic species in meiobenthic organisms. Porcupine Seabight (north-east Atlantic Ocean; continental slope) and a transect along the Kenyan coast (Indian Ocean; shallow lagoon). In the north-east Atlantic, dead coral fragments, sponge skeletons and sediment were collected with a boxcorer. Along the Kenyan coast, dead coral fragments and coral gravel were collected during snorkelling and skin diving. Only nematodes belonging to the families Epsilonematidae and Draconematidae were considered. Community structure was analysed using multivariate techniques. Biodiversity was represented via rarefaction curves. Additive partitioning of species diversity was conducted. Turnover between microhabitats within locations and between locations within microhabitats were compared in a ternary plot. Twelve epsilonematid and five draconematid species were found in the Porcupine Seabight. In Kenya, 39 epsilonematid and 20 draconematid species were distinguished. Three species were found at both sampling locations. A table with the known distribution of all currently described species encountered in our study area is provided. At both sampling locations, the communities on coral fragments were significantly different from those in the other microhabitats, and were most diverse. In Kenya, species richness was mainly determined by local diversity and by turnover between localities. The contribution of beta-diversity decreased when abundance data were analysed. Turnover between microhabitats and between coral samples from different localities was higher than turnover between locations for gravel samples. Coral fragments were recognized as favourable substrata for typically epifaunal nematodes. Species-specific habitat preferences were explained by finely tuned morphological adaptations. Our results suggest that cosmopolitan species could well be cryptic species, and this explanation for the existence of morphologically identical nematodes in geographically distant areas is weighed up against other plausible explanations. Coral degradation zones are an important source for new species of Epsilonematidae and Draconematidae. The addition of sampling locations contributed to the total number of species, although the added species were generally rare

High Meiofaunal and Nematodes Diversity around Mesophotic Coral Oases in the Mediterranean Sea

“…These studies have proven that bio-constructor organisms (as gold corals or deep-water corals), thanks to the complex structure created by their large and hard skeletons, promote benthic biodiversity of hard bottoms by increasing the spatial heterogeneity of the substrate [5], [8], [48], [49]. Recent studies also demonstrated that these corals are able to promote biodiversity even when dead (e.g., coral rubbles), by creating novel substrates [20], [50]. These complex ecosystems are severely threatened by a variety of anthropogenic (e.g., trawling fisheries) and natural disturbances (e.g., climate-driven episodic events, such as dense shelf water cascading and temperature anomalies [15], [51].…”

“…Very little information is available on the role of habitat heterogeneity in modulating the biodiversity of soft-bottom sediments surrounding coral-associated habitats [20], [21]. For example, it has been shown that the meiofaunal abundance and biodiversity in proximity of forests of the gold coral Savalia savaglia are significantly higher than soft bottoms at the same depth but without corals.…”

Marine Nematodes from the Shallow Subtidal Coast of the Adriatic Sea: Species List and Distribution

“…e occurrence of morphologically identical nematode species in completely divergent habitats ("meiofauna paradox" sensu Giere, [56]) is also common in marine meiofauna. However, the existence of cryptic species (a complex of morphologically identical species which can only be differentiated by DNA) or a parallel evolution in response to similar microhabitats seems to be more plausible explanation to this trend than the dispersal capacities (see for review [41]). erefore, theories on the biogeography of nematodes as well as other meiofaunal groups should be proposed with caution.…”

“…In fact, the sediment grain size appears to be one of the main environmental variables in�uencing the horizontal distribution of nematodes. Different sediment types are characterized by different nematode assemblages and by a predominance of speci�c families, so-called isocommunities or parallel communities (see [4,41,42]). …”

Meiobenthos and nematode assemblages from different deep-sea habitats of the Strait of Sicily (Central Mediterranean Sea)

“…To date, only the coral reef from the Porcupine Seabight (NE Atlantic) was in-vestigated (Raes and Vanreusel, 2006;Raes et al, 2008). According to this study, Desmoscolex was the dominating genus in the sediments underlying the coral reef, followed by Pselionema, Sabatieria, Acantholaimus and Desmodora.…”