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

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)

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

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)