Marine Nematodes Research Articles

Impact of unusual monsoonal rainfall in structuring meiobenthic assemblages at Sundarban estuarine system, India

The present study investigates the impact of monsoon on meiofaunal and free-living nematode communities of the Sundarban estuarine system (SES) both from taxonomic and functional point of view. In 2013, SES experienced an unusual rainfall event followed by cloud burst event at upper Himalayan regime. Average meiobenthic abundance declined considerably in the study area from early phase of monsoon (EM) (699 ± 1569.4 ind. 10 cm−2) to later one (LM) (437 ± 949.9 ind. 10 cm−2) probably due to high annual rainfall which completely flushed the estuary. Free-living marine nematodes were the dominant group among all other meiobenthic taxa in both phases of monsoon. Nematode community was made up of 49 genera in 22 families. Comesomatidae, Chromadoridae, Linhomoeidae and Xylidae were the richest and most abundant families. During both phases of monsoon, stations, which were represented by fine sediments and high amount of organic carbon, harbored higher meiofaunal densities and nematode diversity with a strong dominance of 1B and 2B trophic guilds of nematodes. Different feeding guilds of nematode would be able to reveal anthropogenic-induced stress, which could be useful in assessing ecological quality of estuarine ecosystems. The present study indicates that climate change mediated unusual monsoonal precipitation may notoriously affect the meiobenthic assemblages in tropical estuaries like SES. Thus, this study could be an important first stepping stone for monitoring the future environmental impact on meiobenthic community in the largest mangrove region of the world.

Cobbia bengalensis sp. nov. (Xyalidae: Monhysterida) from an eroding island of Sundarban, India.

A new species, Cobbia bengalensis sp. nov., of free-living marine nematodes is described from an island of Sundarban, Indian coast and compared with other eight valid species of the genus. Cobbia bengalensis sp. nov. is characterized and differentiated from the others by a unique combination of sexually dimorphic tail, arrangement of anterior sensilla, amphid position, presence of four subcephalic sensilla at the level of amphid, buccal cavity with one dorsal and two subventral teeth, elongated cardia and the shape of gubernaculum. Some previously recorded taxa thought to be the species of Cobbia has also been discussed. Wrongly recorded data for nematofaunal inventory from Indian water has also been criticized.

Plant-Parasitic Nematodes and their Management: A Review

Nowhere will the need to sustainably increase agricultural productivity in line with increasing demand be more pertinent than in resource poor areas of the world, especially Africa, where populations are most rapidly expanding. Although a 35% population increase is projected by 2050. Significant improvements are consequently necessary in terms of resource use efficiency. In moving crop yields towards an efficiency frontier, optimal pest and disease management will be essential, especially as the proportional production of some commodities steadily shifts. With this in mind, it is essential that the full spectrums of crop production limitations are considered appropriately, including the often overlooked nematode constraints about half of all nematode species are marine nematodes, 25% are free-living, soil inhabiting nematodes, I5% are animal and human parasites and l0% are plant parasites. Today, even with modern technology, 5-l0% of crop production is lost due to nematodes in developed countries. So, the aim of this work was to review some agricultural nematodes genera, species they contain and their management methods. In this review work the species, feeding habit, morphology, host and symptoms they show on the effected plant and management of eleven nematode genera was reviewed. The review result indicated that all of the reviewed nematodes were different in terms of the above mentioned character; some have wide host range like Aphelenchoide while some have generally narrow host range and specialized like Heterodera. Some are ecto-parasite and some are endo- parasite and some are both in different part of the plant in their feeding habit like Aphelenchoide it is endoparasite in leaves, but also feeds ecto-parasitically on leaf and flower buds in some plants. Most of them have large number of species. They can be managed by using different methods like; Sanitation of fields and equipment like Pots potting soil, bio-control agents Paecilomyces lilacinus , Periodic rotation, fumigation and using of clean planting materials. Keywords: Nematodes, Aphelenchoide, Heterodera , bio-control, Periodic rotation and rotation

The genus Bolbonema Cobb, 1920 (Nematoda: Desmodoridae): emended diagnosis, key to males, and description of three new species from the continental shelf off northeastern Brazil.

The marine nematode genus Bolbonema has three valid species, the most recent one described eight years ago. Characteristics of the genus include the well-defined globular cephalic capsule and the long and short somatic setae along the body. Three previously undescribed species of this genus were collected on the continental shelf of the Potiguar Basin in northeastern Brazil. Bolbonema braziliensis sp. n. has a relatively large cryptospiral fovea amphidialis, gubernaculum a bent rod dorsally oriented and two subventral precloacal setae inserted on two small papillae above the cloaca. Bolbonema papillae sp. n. has a large multispiral fovea amphidialis with three turns, arched spicules with the proximal region rounded, a laminar and well-developed gubernaculum enfolding the distal portion of the spicules, and two subventral precloacal papillae just above the cloaca. Bolbonema zildae sp. n. has a spiral fovea amphidialis, no supplements, arched spicules with a velum, and the gubernaculum with a dorsal apophysis. These three new species increase to six the number of taxa known in the genus. A dichotomous key based on males, an emended diagnosis of the genus, and the first record of Bolbonema brevicolle Cobb, 1920 from Brazil are provided.

Direct toxicity of the water-soluble fractions of a crude and a diesel-motor oil on the survival of free-living nematodes

The water-soluble fraction (WSF) of an oil contains different classes of petroleum hydrocarbons and, despite their low potential for bioaccumulation, these can be highly toxic to biota. Nematodes are usually the most abundant and species-rich group of metazoans in marine and freshwater sediments as well as terrestrial soils and have been proposed as excellent models to monitor pollution effects. The first aim of this study was to assess the direct effects of the WSFs of a crude and a diesel-motor oil on the survival of 12 free-living bacterivorous nematode species from marine, freshwater and soil environments, and belonging to diverse taxonomic groups. The second aim was to compare the responses of these twelve test species and assess their suitability as candidate alternatives for the common model species Caenorhabditis elegans in future toxicity testing. The third and final aim was to test the common assumption that nematodes which are phylogenetically more closely related would exhibit more similar sensitivities than more distantly related species, and that – as is commonly stated in literature – nematodes belonging to the family Rhabditidae would be the most pollution-tolerant species. While the crude oil was a complex matrix of substances, containing many soluble compounds, the diesel-motor oil 10W40 was characterized by only few soluble substances. Nevertheless, the diesel-motor oil WSF was as toxic (or even more toxic) to some of the tested nematode species as the crude-oil WSF. This could be linked to differences in compounds interactions in each oil-WSF, or to the presence of fuel additives in the 10W40-WSF. Most species exhibited moderate to extreme mortality levels in oil treatments, and experienced an increased mortality with time. Overall, marine nematodes were more sensitive than freshwater/soil organisms, albeit with some exceptions. Species sensitivities to oil did not follow patterns of taxonomic relatedness, contradicting the idea that closely related species should intrinsically respond similarly to pollution. Rhabditidae were not generally more sensitive than other species: out of 6 species of Rhabditidae tested, only Bursilla monhystera was highly tolerant, while C. elegans and cryptic species of Litoditis marina were among the most sensitive taxa. Therefore, we recommend that future effect studies do not focus on a single model species but instead incorporate multiple species for a better and more robust assessment of pollutant effects.

Application advances and prospects of CRISPR/Cas9 genome editing in nematodes

Nematodes that belong to the Phylum Nematoda are the most abundant multicellular animals on earth. They are widespread in almost all ecosystems and habitats throughout the planet, including the land and the sea (both shallow sea and deep sea). In the Phylum Nematoda, Caenorhabditis elegans is a popular model organism used in biomedical research, although other organisms such as free-living marine nematodes and parasitic nematodes are also the research focus because of their important roles in marine ecological systems or their roles as pathogens of parasitic diseases in humans, livestock, and crops. In recent years, the rapid development and the widespread application of genome editing techniques based on the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system have revolutionized research in biological sciences. Because of the advantages of simple design, low cost, wide range of targets, and high efficiency, the CRISPR/Cas9 system is rapidly becoming an indispensable experimental tool for the entire biological and medical fields. The application of CRISPR/Cas9 technology for studying the nematode worms can help researchers further investigate the function of genes and the associated biological processes, which is essential for our health, society, and environment. In this review, we summarize the recent progress made in the application of the CRISPR/Cas9 genome editing technique in C. elegans and other nematodes. We also discuss the prospects and future application hotspots of this technology in nematodes.

Two new species of Comesomatidae (Nematoda) from the East China Sea

Two new free-living marine nematode species of the genus Paracomesoma and genus Metacomesoma belonging to family Comesomatidae are described from the sublittoral sediment of the East China Sea. Paracomesoma zhangi sp. nov. is characterized by cuticle with fine transverse rows of dots, without lateral differentiation; buccal cavity with three small teeth; cephalic setae 13.5 μm long; multispiral amphideal fovea with three turns; spicules slender and elongated with thick cuticularized proximal end; gubernaculum plate-like without apophysis; 26 minute precloacal supplements. Metacomesoma macramphida sp. nov. is characterized by very small buccal cavity without teeth; inner and outer labial sensilla papilliform; four cephalic setae 1.5 μm long; multispiral amphideal fovea large, with 4.5 turns; spicules slender and elongated, with cephalated proximal end and finger-shaped distal end; gubernaculum plate-like, without apophysis; precloacal supplements absent. An updated dichotomous key for the identification of the males of the species of Paracomesoma is provided.

Regional-scale drivers of marine nematode distribution in Southern Ocean continental shelf sediments

Many marine meiofauna taxa seem to possess cosmopolitan species distributions, despite their endobenthic lifestyle and restricted long-distance dispersal capacities. In light of this paradox we used a metacommunity framework to study spatial turnover in free-living nematode distribution and assess the importance of local environmental conditions in explaining differences between communities in surface and subsurface sediments of the Southern Ocean continental shelf. We analysed nematode community structure in two sediment layers (0–3 cm and 3–5 cm) of locations maximum 2400 km apart. We first focused on a subset of locations to evaluate whether the genus level is sufficiently taxonomically fine-grained to study large-scale patterns in nematode community structure. We subsequently used redundancy and variation partitioning analyses to quantify the unique and combined effects of local environmental conditions and spatial descriptors on genus-level community composition. Macroecological patterns in community structure were highly congruent at the genus and species level. Nematode community composition was highly divergent between both depth strata, likely as a result of local abiotic conditions. Variation in community structure between the different regions largely stemmed from turnover (i.e. genus/species replacement) rather than nestedness (i.e. genus/species loss). The level of turnover among communities increased with geographic distance and was more pronounced in subsurface layers compared to surface sediments. Variation partitioning analysis revealed that both environmental and spatial predictors significantly explained variation in community structure. Moreover, the shared fraction of both sets of variables was high, which suggested a substantial amount of spatially structured environmental variation. Additionally, the effect of space independent of environment was much higher than the effect of environment independent of space, which shows the importance of including spatial descriptors in meiofauna and nematode community ecology. Large-scale assessment of free-living nematode diversity and abundance in the Southern Ocean shelf zone revealed strong horizontal and vertical spatial structuring in response to local environmental conditions, in combination with (most likely) dispersal limitation.

Spatio-temporal distribution of meiofaunal assemblages and its relationship with environmental factors in a semi-enclosed bay

In order to reveal the spatio-temporal distribution of meiofaunal assemblages and its relationship with environmental factors in semi-enclosed bay habitats, meiofaunal and sediment samples were collected in February (winter), May (spring), August (summer) and November (autumn) 2014 in Jiaozhou Bay, China. A total of 20 meiofaunal taxa were identified. The most dominant group was free-living marine nematode, followed by benthic copepod. During the four sampling seasons, the values of meiofaunal average abundance were (912.3 ± 603.1), (1576.4 ± 659.5), (1074.6 ± 417.6), (2152.4 ± 1062.3) ind./10 cm2 while those of biomass were (575.0 ± 398.5), (874.3 ± 518.4), (617.9 ± 337.8), (1203.6 ± 719.6) μg dwt/10 cm2, respectively. In terms of vertical distribution, meiofauna were mainly found in the (0–2) cm sediment layer (59.92%), followed by (2–5) cm layer (28.25%) and (5–8) cm layer (11.82%). Results of correlation analysis showed that bottom water temperature was the main factor influencing meiofaunal distribution and food source (sediment organic matter content) was the main factor influencing meiofaunal assemblages.

Nematode-associated microbial taxa do not correlate with host phylogeny, geographic region or feeding morphology in marine sediment habitats.

Studies of host-associated microbes are critical for advancing our understanding of ecology and evolution across diverse taxa and ecosystems. Nematode worms are ubiquitous across most habitats on earth, yet little is known about host-associated microbial assemblages within the phylum. Free-living nematodes are globally abundant and diverse in marine sediments, with species exhibiting distinct buccal cavity (mouth) morphologies that are thought to play an important role in feeding ecology and life history strategies. Here, we investigated patterns in marine nematode microbiomes, by characterizing host-associated microbial taxa in 281 worms isolated from a range of habitat types (deep-sea, shallow water, methane seeps, Lophelia coral mounds, kelp holdfasts) across three distinct geographic regions (Arctic, Southern California and Gulf of Mexico). Microbiome profiles were generated from single worms spanning 33 distinct morphological genera, using a two-gene metabarcoding approach to amplify the V4 region of the 16S ribosomal RNA (rRNA) gene targeting bacteria/archaea and the V1-V2 region of the 18S rRNA gene targeting microbial eukaryotes. Contrary to our expectations, nematode microbiome profiles demonstrated no distinct patterns either globally (across depths and ocean basins) or locally (within site); prokaryotic and eukaryotic microbial assemblages did not correlate with nematode feeding morphology, host phylogeny or morphological identity, ocean region or marine habitat type. However, fine-scale analysis of nematode microbiomes revealed a variety of novel ecological interactions, including putative parasites and symbionts, and potential associations with bacterial/archaeal taxa involved in nitrogen and methane cycling. Our results suggest that in marine habitats, free-living nematodes may utilize diverse and generalist foraging strategies that are not correlated with host genotype or feeding morphology. Furthermore, some abiotic factors such as geographic region and habitat type do not appear to play an obvious role in structuring host-microbe associations or feeding preferences.

A CHECKLIST OF FREE-LIVING MARINE NEMATODES AT DIFFERENT ECOSYSTEM IN NORTHERN STRAITS OF MALACCA, MALAYSIA

Nematodes present in all substrates and sediment types with an enormous number of species. The studies on free-living marine nematodes are still limited in Malaysia. The present study provides general information on genus checklist of free-living marine nematodes in the northern part of Peninsular Malaysia in a different ecosystem which are intertidal zones of estuarine, sandy beach and mangrove ecosystems. Samples were randomly collected at three stations in each ecosystem. A total of 34 genera (22 families and ten suborders) were recorded in three ecosystems. Each ecosystem had common genera which also commonly found worldwide. Viscosia genus was observed in all three ecosystems. The nematode genera of Estuary and mangrove ecosystems had greater similarities than those in the sandy beach.

Correlation between Oxygen Demand of Nematode Communities with Dissolved Oxygen in the Organic Shrimp Farming Ponds, Ca Mau Province

Correlation between Oxygen Demand of Nematode Communities with Dissolved Oxygen in the Organic Shrimp Farming Ponds, Ca Mau Province

Seasonal and Spatial Variations of Meiofauna Communities in Correlation to Environmental Characteristics in the Organic Shrimp Farms of Tam Giang Commune, Nam Can District, Ca Mau Province

Environmental factors and meiofauna communities in the organic shrimp farms located in Tam Giang commune, Nam Can District, Ca Mau province were investigated in March (dry season), July (transfer season) and November (wet season) of 2015. The results recorded that the environmental factors were not quite optimal for shrimp farming such as the high percentage of TN and TOC and anaerobic condition in sediment. The results were also indicated that DO, TOC and TN showed significant correlation with characteristics of meiofauna communities. Following results were indicated that the meiofauna communities were expressed as the high abundance and slightly biodiversity that is a rich natural food sources for shrimp in the organic shrimp farms ponds. Further more, nematoda dominate numerically in the meiofauna communities.
 Keywords
 Biodiversity, Ca Mau, mangroves, meiofauna, organic shrimp farms
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Do the morphological and functional traits of free-living marine nematodes mirror taxonomical diversity?

The taxonomical structure and diversity of nematode assemblages are the main attributes analyzed in ecology, but nematode adaptations to their habitats are still understudied. Accordingly, a survey on some known and other newly proposed morpho-functional traits was carried out in order to: determine if the morpho-functional diversity of nematodes mirrors their taxonomical diversity; and assess potential nematode adaptations to sediment type and hydrodynamic stress. Morpho-functional traits were investigated both singularly and together and showed significant differences related to these environmental factors. The greatest taxonomical and morpho-functional diversity was found in medium-coarse sand (M-CS) and at an intermedium energy level (IEL). The M-CS and IEL were probably richer in micro-habitats and subject to a low selective pressure, hosting nematodes with a wide range of adaptations. The mirroring of morpho-functional diversity with taxonomical diversity is crucial for the future growth of the use of nematodes in biomonitoring. This is because the study of their morpho-functional traits could reduce the level of work involved and the costs of any analyses.

Ecostructuring of marine nematode communities by submarine groundwater discharge

Inputs of submarine groundwater discharge (SGD) to the coastal ocean may alter local and regional-scale biology. Here, we report on nematode assemblages along the north shore of Long Island, NY. We test if nematode communities differed between sites impacted by mixed fresh-saline SGD and where SGD is exclusively saline. Diversity of nematodes was low at sites impacted by fresh SGD and communities were dominated by a few opportunistic genera. Moreover, a set of typical freshwater nematode genera restricted to impacted sites was observed. Their presence in the marine coastal zone is exceptional and underlines the structuring role that fresh SGD plays in the local ecosystem. Saline SGD structured nematode assemblages differently compared to sites impacted by fresh SGD. The number of nematode genera was markedly higher at saline SGD sites, with a different community structure. This study highlights the importance to which inputs of fresh SGD may have on local ecosystem diversity in marine coastal environments.

Inventory of the free-living marine nematode species from el Bibane Lagoon (Tunisia)

espanolSe ha realizado un inventario detallado de los nematodos de vida libre de la parte norte deTunez, pero la parte sur del pais esta inexplorada. La laguna de El Bibane es la segunda mas extensa de Tunez, por lo que su importancia es fundamental para el desarrollo de futuras acciones de conservacion y su biodiversidad debe ser evaluada. Se encontraron 71 especies de nematodos, pertenecientes a 68 generos y 22 familias, registrandose la menor riqueza en la zona central de la laguna, donde se concentran los porcentajes mas elevados de lodo y materia organica. El numero de especies halladas en este estudio es elevado si se compara con el de otros entornos de transicion de la cuenca mediterranea, pero mas bajo que los registrados en el norte de Europa. La mayor parte de las especies son tipicas de entornos de transicion o de sedimentos ricos en fraccion fna y detritos. Las familias mas ricas fueron Cyatholaimidae y Chromadoridae, pero las halladas con mayor frecuencia fueron Xyalidae, Linhomoeidae y Cyatholaimidae. Merece destacarse que seis especies recolectadas son nuevas para la ciencia, siete son nuevos registros en aguas tunecinas y cuatro nuevos registros en la cuenca mediterranea. Este estudio aporta asimismo informacion importante para la biogeografia del flo puesto que hasta ahora algunas de las especies registradas aqui eran conocidas unicamente en otras regiones geografcas. Entre las especies que en este momento aparecen como endemicas en el mar Mediterraneo se encuentran Chromadorina metulata, Synonchiella edax, Paralongicyatholaimus mastigodes, Trichotheristus setifer yMetalinhomoeus numidicus. MultipleS’ha fet un inventari detallat dels nematodes de vida lliure de la part nord de Tunisia, pero la part sud del pais esta inexplorada. La llacuna del Bibane es la segona mes extensa de Tunisia, per la qual cosa te una importancia fonamental per al desenvolupament de futures accions de conservacio i cal avaluar–ne la biodiversitat. S’hi van trobar 71 especies de nematodes, pertanyents a 68 generes i 22 families. La riquesa mes baixa es va registrar a la zona central de la llacuna, on es concentren els percentatges mes elevats de llot i materia organica. El nombre d’especies trobades en aquest estudi es alt si es compara amb el d’altres entorns de transicio de la conca mediterrania, pero mes baix que els registrats al nord d’Europa. La major part de les especies son tipiques d’entorns de transicio o de sediments rics en fraccio fna i detrits. Les families mes riques van ser Cyatholaimidae i Chromadoridae, pero les trobades amb mes frequencia van ser Xyalidae, Linhomoeidae i Cyatholaimidae. Cal posar en relleu que sis especies recol·lectades son noves per a la ciencia, set son nous registres en aigues tunisenques i quatre nous registres a la conca mediterrania. Aquest estudi tambe aporta informacio important per a la biogeografa del filum ates que fns ara algunes de les especies registrades aqui nomes eren conegudes en altres regions geografques. Entre les especies que en aquest moment apareixen com a endemiques al mar Mediterrani es troben Chromadorina metulata, Synonchiella edax, Paralongicyatholaimus mastigodes, Trichotheristus setifer i Metalinhomoeus numidicus. EnglishA detailed inventory of the free–living nematodes of Tunisia has been made for the northern part of Tunisia, but the southern part of the country is unexplored. El Bibane is the second largest lagoon in Tunisia. It is thus of high importance for future conservation actions, but little is known about its biodiversity. In this study, we identifed 71 nematode species, belonging to 68 genera and 22 families. Richness was lowest in the central area of the lagoon where the highest percentages of mud and organic matter were found. The number of species detected in this study is high compared to other transitional environments in the Mediterranean basin, but lower than those reported for North Europe. Most of the species are typical of transitional environments or sediments rich in the fne fraction and detritus. The richest families were Cyatholaimidae and Chromadoridae, but the most frequently found species were Xyalidae, Linhomoeidae and Cyatholaimidae. Six of the species collected are new to science, seven are new records for Tunisian waters, and four are new for the Mediterranean basin. This study adds also important information to the biogeography of the phylum because some of the species detected here were previously known only for other geographical regions. Species that currently appear endemic to the Mediterranean Sea include Chromadorina metulata, Synonchiella edax, Paralongicyatholaimus mastigodes, Trichotheristus setifer and Metalinhomoeus numidicus.

The mature and immature spermatozoa of the free-living marine nematode Daptonema sp. (Nematoda: Monhysterida: Xyalidae)

The immature spermatozoa stored in the testis and female postvulval uterine sac (PUS), and mature spermatozoa from the uterus of the free-living marine nematode Daptonema sp. (Monhysterida: Monhysterina: Xyalidae) were studied. The spermatozoa have a nucleus without a nuclear envelope. The central cytoplasm of the immature spermatozoa from the testis and the distal part of the PUS is occupied by a mass of pale fibrous bodies (FB) surrounded by mitochondria and osmiophilic membranous organelles (MO). The spermatozoa in the proximal half of PUS have a wide peripheral layer of electron lucent filamentous cytoplasm. The uterus lumen contains an aggregation of mature spermatozoa of which the periphery is transformed into pseudopods. The FB replaced by a voluminous electron-lucent halo bounded by a continuous layer of MO, mitochondria and fibrous matter. The MO may be intact, but numerous MO are fused with the plasma membrane, having been transformed into transparent pouches, each one opening to the exterior via a pore. Ultrastructural data showed that the activation is regulated in the female when spermatozoa migrate toward the uterus and transform into amoeboid mature spermatozoa. In general, the spermatozoa of Daptonema sp. and some other Monhysterina closely resemble those of the taxa belonging to the order Rhabditida. However, the `rhabditid' pattern of spermatozoon structure and development is most likely the plesiomorphic state in Rhabditida and close sister groups.

Seasonal dynamics of meiofaunal distribution in the Dagu River Estuary, Jiaozhou Bay, China

Sediment samples were collected in the intertidal zone of the Dagu River Estuary, Jiaozhou Bay, China in April, July and October 2010 and February 2011 for examining seasonal dynamics of meiofaunal distribution and their relationship with environmental variables. A total of ten meiofaunal taxa were identified, including free-living marine nematodes, benthic copepods, polychaetes, oligochaetes, bivalves, ostracods, cnidarians, turbellarians, tardigrades and other animals. Free-living marine nematodes were the most dominant group in both abundance and biomass. The abundances of marine nematodes were higher in winter and spring than those in summer and autumn. Most of the meiofauna distributed in the 0–2 cm sediment layer. The abundance of meiofauna in hightidal zone was lower than those in low-tidal and mid-tidal zones. Results of correlation analysis showed that Chlorophyll a was the most important factor to influence the seasonal dynamics of the abundance, biomass of meiofauna and abundances of nematodes and copepods. CLUSTER analysis divided the meiofaunal assemblages into three groups and BIOENV results indicated that salinity, concentration of organic matter, sediment sorting coefficient and sediment median diameter were the main environmental factors influencing the meiofaunal assemblages.

Checklist of the Free-Living Marine Nematodes of the Iberian Peninsula (north east Atlantic).

A Checklist of the Free-Living Marine Nematodes of the Iberian Peninsula, based on the literature published to date, is presented in this paper. The localities where the taxa were collected, as well as the habitats and depths where they were found, are also mentioned. All references to date provide a total of 236 species, 142 genera and 37 unidentified families. Also, the preparation of the present Checklist allowed us to clarify some errors that have been dragging on for some time and make a few clarifications, all of them based on a review of the original papers.

An approach based on nematode descriptors for the classification of ecological quality (EcoQ) of the Malaysian coasts

Free-living marine nematodes were employed in ecological studies and were proven to be suitable bioindicators of pollution-induced effects on the benthic domain. This study represents the first attempt to use nematode descriptors in order to assign ecological quality (EcoQ) status to areas along the Sarawak coasts, thus integrating the methods actually applied by the Department of Environment (DOE). Three nematode parameters, i.e. colonizer–persister percentage, maturity index (MI), and Shannon diversity index (Hˈ), were used, as they are recognized as the best descriptors of EcoQ status in coastal habitats. The thresholds applied to the nematode parameters for the Sarawak study sites showed predominantly moderate and bad EcoQ status, with the exception of the Similajau site, which being close to a national park was found to have good EcoQ. The sites with the worst EcoQ were characterized by low salinity values, suggesting riverine inflows as a primary source of pollution, likely from the discharge of untreated wastes. This was confirmed by both the Hˈ and MI indices, which showed a close positive relation with salinity. Results obtained for the Niah site may suggest that “traces” of pollution were left in the nematode assemblages that could not be detected from other parameters of the water column. This investigation shows that analysis of nematode descriptors could be effectively applied to ecological assessment criteria within environmental policies of rapid growth countries such as Malaysia. Furthermore, it certainly suggests the need for management and conservation actions in the Sarawak coasts aimed at more sustainable use of the marine resources to prevent the loss of biodiversity.