14 research outputs found
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)