Nematodes down under: State of knowledge and future trends

Nematodes inhabit most environments that address their need of water, carbon, and energy. They also play an important role in epigean food webs by occupying different trophic levels, while providing essential ecosystem services such as regulating decomposition and nutrient mineralization. Conversely, little is known about the role that nematodes play in subterranean ecosystems. For this reason, an in-depth review was undertaken in order to concatenate data from existing literature and provide a baseline for future studies. A total of 41 surveyed scientific works, published over a time period of 138 years, reported 295 unique taxa from 78 different cave systems. Although an increase in scientific outputs was recorded from the late 1990s, there is a considerable lack of information on cave-dwelling nematodes from Asia, South America, and North America. Also, only seven true cave-dwelling (troglobitic) species have been discovered, which may indicate a lack of comprehensive taxonomic efforts. From an ecological perspective, very few works have reported on the importance of nematode assemblages associated with cave ecosystems. This has resulted in the causal factors leading to population resilience processes, as well as trophic interactions, remaining mostly speculative. Nonetheless, the isolated cave-dwelling nematode assemblage associated with Movile Cave, including the true cave-dwelling species Chronogaster troglodytes, fulfills an important role by feeding on microbial mats and in turn serving as a food source for predators. This example of a cave nematode assemblage providing ecosystem services has inspired the undertaking of the Gcwihaba Caves Research Project, which aims at studying artificially opened caves in Ngamiland, Botswana. Compared to other caves in the area with natural openings, the artificially opened systems present different food source pathways, atmospheric conditions, and community assemblage structures. This provides a unique opportunity to study isolated cave communities, including nematode assemblages, as well as their ecological importance

Nematode-based indices in soil ecology: Application, utility, and future directions

14 Pág.The health and functioning of soil ecosystems are the foundation of sustainable food production and land management. Of key importance in achieving sustainability, is the frequent measurement of soil health, and indices based on the community structure of nematodes are amongst the most widely used toolsets by soil ecologists. Thirty years after the development of the Maturity Index, we aimed to evaluate the application, utility, and future directions of nematode-based indices (NBIs). This review focused on NBIs that are calculated using the coloniser-persister classification of nematodes. Data from 672 empirical studies in terrestrial environments revealed that the NBIs presented a dissimilar usage trend. The Channel Index and Metabolic Footprints showed the strongest increase in application rates over time, thus indicating a greater interest in studying decomposition pathways and ecosystem functioning, respectively. Furthermore, nematode-based indices were mostly applied in agricultural systems associated with herbaceous crops and in studies investigating, for example, soil nutrient enrichment following manure and/or inorganic fertilizer application. We further provide a framework for selecting a focus-orientated subset of NBIs for testing hypotheses based on the underlying ecological mechanisms. Also, we highlight important considerations, including the unexpected behaviour of some nematode taxa, in the interpretation of NBIs. The improvement of NBIs relies on advancing our understanding of the autecology of nematodes. Finally, we deliver insight into the further development of NBIs considering recent methodological advancements. We highlight that NBIs have been and might become increasingly important in providing valuable information on soil ecosystem health and functioning, especially considering the urgent need for more sustainable land use.The contribution of JHS was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) — :— Project no. 420414676: “The self-regulatory potential of agro-ecosystems: Using nematodes as indicators for legume disease suppressive soils”.Peer reviewe

Nematodes of the Wonderfontein Cave (Witwatersrand Basin, South Africa)

Although the importance of nematodes, especially in soil ecosystems, is well appreciated, very little is known about the occurrence of and ecosystem services provided by cavernicolous nematodes. This study was undertaken to determine the nematode occurrence, density and distribution in the Wonderfontein Cave (South Africa), which is subjected to the influx of water from the Wonderfontein Spruit. Of the 53 nematode genera collected from the Wonderfontein Cave during the first (April 2013) and second (September 2013) sampling intervals, 22 have never been reported from a cave environment. Results indicated that many of the nematodes found may only be temporary residents introduced from the surface environment. This study reveals the necessity of further efforts to investigate the nematode communities associated with subterranean environments, which will provide a better understanding of the functioning of the associated ecosystem

Aphelenchoides spp. (Nematoda: Aphelenchida) and Panagrolaimus leperisini (Nematoda: Rhabditida) found associated with grass seeds in the Telperion Nature Reserve, South Africa

Girgan, Chantelle, Swart, Antoinette, Marais, Mariette, Fourie, Hendrika (2018): Aphelenchoides spp. (Nematoda: Aphelenchida) and Panagrolaimus leperisini (Nematoda: Rhabditida) found associated with grass seeds in the Telperion Nature Reserve, South Africa. Zootaxa 4370 (2): 137-155, DOI: https://doi.org/10.11646/zootaxa.4370.2.