Description of Marylynnia puncticaudata n. sp. (Nematoda, Cyatholaimidae) from Bizerte Lagoon, Tunisia

Descripción de Marylynnia puncticaudata sp. n. (Nematoda, Cyatholaimidae) del lago de Bizerta, Túnez Se describe morfológicamente una nueva especie de nematodo marino de vida libre de la familia Cyatholaimidae: Marylynnia puncticaudata sp. n. del lago de Bizerta (Túnez). Los machos se caracterizan por tener un cuerpo ligeramente más grande que las hembras, un anillo cefálico seguido de diez sedas subcefálicas, puntuación distinta de la cutícula, diferenciación laterocaudal de grandes puntos y gubernáculo muy cuticularizado con una forma única y la mitad distal bidenticulada. La ornamentación de la cutícula de las hembras es parecida a la de los machos. Sin embargo, su diferenciación laterocaudal se compone de puntos más pequeños y espaciados. Se ofrece una clave morfológica actualizada de la especie Marylynnia.A new free–living marine nematode species of Cyatholaimidae, Marylynnia puncticaudata n. sp. from Bizerte Lagoon (Tunisia) is morphologically described. Males are characterized by a slightly larger body than females, a cephalic ring followed by ten subcephalic setae, modified cuticular punctuation, caudal lateral differentiation of large dots, and strongly cuticularized gubernaculum with a unique shape and bidenticulated distal half. The cuticle ornamentation of females is similar to the males. However, their caudal lateral differentiation is composed of smaller and more spaced dots. An updated morphological key to species of Marylynnia is given.Descripción de Marylynnia puncticaudata sp. n. (Nematoda, Cyatholaimidae) del lago de Bizerta, Túnez Se describe morfológicamente una nueva especie de nematodo marino de vida libre de la familia Cyatholaimidae: Marylynnia puncticaudata sp. n. del lago de Bizerta (Túnez). Los machos se caracterizan por tener un cuerpo ligeramente más grande que las hembras, un anillo cefálico seguido de diez sedas subcefálicas, puntuación distinta de la cutícula, diferenciación laterocaudal de grandes puntos y gubernáculo muy cuticularizado con una forma única y la mitad distal bidenticulada. La ornamentación de la cutícula de las hembras es parecida a la de los machos. Sin embargo, su diferenciación laterocaudal se compone de puntos más pequeños y espaciados. Se ofrece una clave morfológica actualizada de la especie Marylynnia

Impact des pseudo-fèces de moules sur les densités des bactéries hétérotrophes dans le secteur mytilicole de la lagune de Bizerte (Tunisie)

Cette étude se propose de caractériser au niveau du secteur mytilicole de la lagune de Bizerte l’impact des pseudo-fèces de moules sur les densités bactériennes, particulièrement celles des Vibrionaceae et des bactéries hétérotrophes. Les prospections ont été réalisées en hiver 2000 et en été 2001 au niveau de 5 stations plus ou moins proches d’une table d’élevage, aussi bien dans la colonne d’eau que dans le sédiment. Sous le parc, les sédiments étant les plus fortement chargés en fraction fine (78-83%) et en carbone organique total (COT) (2,5%), les densités microbiennes étaient élevées (1,82-2,83 • 108 UFC/g de sédiment pour les bactéries hétérotrophes et 2,50-17,32 • 102 UFC/g pour les Vibrionaceae). Une analyse en composantes principales (ACP) montre une étroite relation entre, d’une part, les concentrations bactériennes et, d’autre part, les teneurs en matière organique et plusieurs variables hydrologiques, particulièrement la température, la salinité et l’oxygène dissous.This study aims to characterize the effect of high organic loads, produced by a mussel farm in the Bizerte Lagoon, on the distribution of bacterial densities of, especially, marine heterotrophic bacteria and Vibrionaceae in the water column and in the sediment. Five sites located along a distance gradient from the mussel breeding ground were surveyed during the winter of 2000 and the summer of 2001. Below the mussel farm, the sediment was characterized by high percentages of fine particles (78-83%) and total organic carbon (TOC; 2.5%). Furthermore, this station exhibited high bacterial densities, especially of heterotrophic flora (1.82-2.83 • 108UFC/g) and Vibrionaceae (2.50-17.32 • 102 UFC/g). Principal components analysis revealed a strong relationship among bacterial density, high organic loads and hydrological parameters, particularly temperature, salinity and dissolved oxygen

Metabarcoding free-living marine nematodes using curated 18S and CO1 reference sequence databases for species-level taxonomic assignments

High‐throughput sequencing has the potential to describe biological communities with high efficiency yet comprehensive assessment of diversity with species‐level resolution remains one of the most challenging aspects of metabarcoding studies. We investigated the utility of curated ribosomal and mitochondrial nematode reference sequence databases for determining phylum‐specific species‐level clustering thresholds. We compiled 438 ribosomal and 290 mitochondrial sequences which identified 99% and 94% as the species delineation clustering threshold, respectively. These thresholds were evaluated in HTS data from mock communities containing 39 nematode species as well as environmental samples from Vietnam. We compared the taxonomic description of the mocks generated by two read‐merging and two clustering algorithms and the cluster‐free Dada2 pipeline. Taxonomic assignment with the RDP classifier was assessed under different training sets. Our results showed that 36/39 mock nematode species were identified across the molecular markers (18S: 32, JB2: 19, JB3: 21) in UClust_ref OTUs at their respective clustering thresholds, outperforming UParse_denovo and the commonly used 97% similarity. Dada2 generated the most realistic number of ASVs (18S: 83, JB2: 75, JB3: 82), collectively identifying 30/39 mock species. The ribosomal marker outperformed the mitochondrial markers in terms of species and genus‐level detections for both OTUs and ASVs. The number of taxonomic assignments of OTUs/ASVs was highest when the smallest reference database containing only nematode sequences was used and when sequences were truncated to the respective amplicon length. Overall, OTUs generated more species‐level detections, which were, however, associated with higher error rates compared to ASVs. Genus‐level assignments using ASVs exhibited higher accuracy and lower error rates compared to species‐level assignments, suggesting that this is the most reliable pipeline for rapid assessment of alpha diversity from environmental samples

The response of cultured meiofaunal and benthic foraminiferal communities to lead contamination: results from mesocosm experiments.

partially_open13sìLead (Pb) is regarded as a highly toxic element that poses a serious threat to biota. A mesocosm experiment was performed to assess the influence of Pb on meiofaunal (metazoans within 45–500 mm) and benthic foraminiferal (protozoan) communities. To this end, sediments bearing such communities were incubated in mesocosms, exposed to different levels of Pb in seawater, and monitored for up to 8 wk. Concentrations of Pb <1ppm in water did not promote a significant increase of this metal in sediments. Relatively high concentrations of Pb seemed to affect meiofaunal and benthic foraminiferal communities by reducing their richness or diversity, and the abundance of the most sensitive taxa. The mesocosm approach can be considered an effective method to document the responses of meiofaunal and benthic foraminiferal communities to various kinds and concentrations of pollutants over time. This approach allows the evaluation of dose–response relationships, validates the outcomes of field studies, and possibly confirms the sediment quality guidelines and thresholds.openFrontalini F., Semprucci F., Di Bella L., Caruso A., Cosentino C., Maccotta A., Scopelliti G., Sbrocca C., Bucci C., Balsamo M., Martins V., Armynot du Châtelet E., Coccioni R.,Frontalini, F.; Semprucci, F.; Di Bella, L.; Caruso, A.; Cosentino, C.; Maccotta, A.; Scopelliti, G.; Sbrocca, C.; Bucci, C.; Balsamo, M.; Martins, V.; Armynot du Châtelet, E.; Coccioni, R

Checklist of the subfamily Adoncholaiminae Gerlach and Riemann, 1974 (Nematoda: Oncholaimida: Oncholaimidae) of the world: genera, species, distribution, and reference list for taxonomists and ecologists

Adoncholaiminae is one of the seven subfamilies in the free-living aquatic nematode family Oncholaimidae. Nematodes in Adoncholaiminae are found from various water environment of the world. However, a checklist of all Adoncholaiminae species including full literature, especially information of experimental (not taxonomic) works, has not been updated for more than 40 years. A revised checklist of the subfamily Adoncholaiminae of the world is provided. It contains 31 valid and 13 invalid species names in four genera with synonyms, collection records, and full literature from 1860's to 2015 for each species. A literature survey of total 477 previous papers was conducted in this work, and 362 of them are newly added to checklist

Description of Marylynnia puncticaudata n. sp. (Nematoda, Cyatholaimidae) from Bizerte Lagoon, Tunisia

A new free–living marine nematode species of Cyatholaimidae, Marylynnia puncticaudata n. sp. from Bizerte Lagoon (Tunisia) is morphologically described. Males are characterized by a slightly larger body than females, a cephalic ring followed by ten subcephalic setae, modified cuticular punctuation, caudal lateral differentiation of large dots, and strongly cuticularized gubernaculum with a unique shape and bidenticulated distal half. The cuticle ornamentation of females is similar to the males. However, their caudal lateral differentiation is composed of smaller and more spaced dots. An updated morphological key to species of Marylynnia is given

Stress-induced selection of a single species from an entire meiobenthic nematode assemblage: is this possible using iron enrichment and does pre-exposure affect the ease of the process?

The present work proposes a new experimental design using iron enrichment to select a single species from an entire meiobenthic nematode community. The high diversity of nematodes makes it impossible to study their responses to stressors in terms of chemical biomarkers, as this kind of research demands a single species as a form of biological material. Two assemblages, one from a control site (Canal) and one from an iron-contaminated site (Fouledh) in Bizerte Lagoon (Tunisia), were used to validate the protocol and to study whether pre-exposure to iron could affect the ease of the selection process. Analyses of variance suggested that the abundance and species number of nematodes from the Canal and Fouledh sites decreased discernibly with exposure to iron. Multivariate analyses performed on nematode abundances revealed that Oncholaimus campylocercoides, Sabatieria granifer, Sabatieria punctata and Theristus flevensis were the most tolerant species, probably due to their depositfeeding behaviour. Species with a restricted feeding spectrum showed a low tolerance potential. At the end of the experiment, O. campylocercoides became the unique component of the nematode community from both sites. The complete alteration of the community was achieved with more difficulty for nematodes from Fouledh than for those from Canal. The identity of the selected species was confirmed at both the morphological levels and by sequencing the nuclear small subunit ribosomal DNA (18S rDNA)

An experimental protocol to select nematode species from an entire community using progressive sedimentary enrichment.

The purpose of this study was to introduce free-living marine nematodes to the ‘world of biomarkers’.Biomarkers are still not used in the monitoring and assessment of this highly diverse phylum, becausethe technique needs to be applied at the single species level. This incurs high costs and involves time-consuming procedures, which are currently the main pitfalls when it comes to the application of thesetechniques to marine nematodes. Consequently, this work proposes an innovative protocol for selectinga single species from an entire community of nematodes using two independent selection processeswhereby the sediment of the microcosms is progressively and separately enriched with fine and coarsesediment fractions. During our experiment, the abundance and number of nematode species decreaseddiscernibly with exposure to both finer and coarser sediment. Multivariate analyses revealed that deposit-and epigrowth-feeders were the most tolerant feeding guilds, probably due to their deposit-feedingand microvore behaviours. At the end of the experiment, Terschellingia longicaudata and Ptycholaimellusponticus became the unique members of the community when the sediment was enriched with fine andcoarse sediment particles, respectively. After the complete alteration of the community, and when themono-species level had been achieved, it was possible to maintain these two species alive, and withoutany drop in numbers, under the same laboratory conditions considered during the selection process.Accordingly, the protocol adopted here lays new foundations for the study of nematodes in the biomarkerfield

Marine Nematode Taxonomy in Africa: Promising Prospects Against Scarcity of Information

From the late 19th century, Africa has faced heavy exploitation of its natural resources with increasing land/water pollution, and several described species have already become extinct or close to extinction. This could also be the case for marine nematodes, which are the most abundant and diverse benthic group in marine sediments, and play major roles in ecosystem functioning. Compared to Europe and North America, only a handful of investigations on marine nematodes have been conducted to date in Africa. This is due to the scarcity of experienced taxonomists, absence of identification guides, as well as local appropriate infrastructures. A pivotal project has started recently between nematologists from Africa (Tunisia), India, and Europe (Italy) to promote taxonomic study and biodiversity estimation of marine nematodes in the African continent. To do this, as a first step, collection of permanent slides of marine nematodes (235 nominal species and 14 new to science but not yet described) was recently established at the Faculty of Sciences of Bizerte (Tunisia). Capacity building of next generation of African taxonomists have been carried out at level of both traditional and molecular taxonomy (DNA barcoding and next-generation sequencing [NGS]), but they need to be implemented. Indeed, the integration of these two approaches appears crucial to overcome lack of information on the taxonomy, ecology, and biodiversity of marine nematodes from African coastal waters