CONTENT - International Society of Zoological Sciences

S20 ICZ2008 - Abstracts
Late colonizers, which do not possess bacterial coat, seemed to
take advantage of the decrease of sulfide levels, while the
symbiotic organisms more adapted to the high sulfide levels
disappear. This study combining chemical and biological
approaches allowed a better characterization of sunken wood
colonization process.
Molecular taxonomy and speciation patterns in mussels
associated to organic falls
Julien Lorion and Sarah Samadi
MNHN, Service de Systématique Moléculaire 57 rue Cuvier F-
75231 Paris cedex 05, France
The biodiversity in deep sea marine environments is still poorly
known, what slows down the study of the evolutionary processes
such as speciation and dispersion. In this context, hydrothermal
vents and cold seeps have stirred up the attention of the biologists.
Indeed in this extreme environmental conditions inhabit original
communities of endemic o! rganisms. Among the most studied
organisms living on those ecosystems are the Bathymodiolinae
mussels. Bathymodiolinae mussels (Bivalvia: Mytilidae) were
thoroughly studied in hydrothermal vents and cold seeps, where it
was shown that they have symbiotic relationships with
chemosynthetic bacteria. Other species inhabiting less known
ecosystems such as sunken vegetable material and decaying
bones of marine vertebrates form a clade with the Bathymodiolinea.
Both plant material and bones, produce dihydrogene sulphides,
from lignin or lipids respectively, when decaying on the sea floor
allowing chimiosynthesis. Some species inhabiting sunken woods
were yet shown to have chemosynthetic symbionts, among which
the thiotrophic bacteria are the most common ones. Using an
integrative taxonomy approach, we give new insights to the
diversity of mussel species associated to organic falls and discuss
which factors (such as geographic barriers or symbiotic
relationships) drives the speciation in these reducing environments.
Age, growth and mortality of largescaled scorpionfish
(Scorpaena scrofa, Linnaeus, 1758) in the eastern Adriatic Sea
Sanja Matić-Skoko, Miro Kraljević, Armin Pallaoro and Jakov
Dulčić
Institute of oceanography and fisheries, Spli, Croatia, Meštrovićevo
šetalište 63, P.O.box. 500, 21 000 Split, Croatia
The age, growth and mortality parameters of Scorpaena scrofa
from the eastern middle Adriatic Sea were studied. Total lengths
(TL) of 350 specimens ranging from 13.5 to 58.2 cm were obtained
by trammel net fishing (2000-2005). Total weight was ranging from
60.0 to 3650.0g. The mean lengths, as well as the age frequency
distributions of males and females were not significantly different.
Scales showed clearly the ring pattern. The opaque ring was
deposited during the summer months. The length-weight
relationship showed a positive allometric growth (b = 3.165; R 2 =
0.989). The parameters of the von Bertalanffy growth equation
were: L∞ = 68.20 cm; K = 0.084 per year; t0 = -1.378 year; R 2 =
0.981. This study revealed that S. scrofa is a relatively slow
growing and long-lived species with a life span in excess of 25
years. The mortality parameters were: Z=0,27, M=0,22 and F=0,05.
Description of two new Desmodora species: marine
ectosymbiotic Nematode from Thalassia testudinum
environment in Guadeloupe (F.W.I.)
Leslie C. Maurin 1 , Janura Rzeznik-Orignac 2 and Olivier Gros 1
1 UMR-CNRS 7138, Systématique-Adaptation-Evolution, Equipe
« Symbiose ». Université des Antilles et de la Guyane,
Guadeloupe. France.
2 UMR-CNRS 5178 Biologie des Organismes Marins et
Ecosystèmes, Département Milieux et Peuplements Aquatiques,
MNHN, CP 53, 61 rue Buffon, 75231 Paris cedex 05, France
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Two new morphotypes of marine nematodes belonging to the
genus Desmodora (Desmodoridae) are found from calcareous
sand of Thalassia testudinum sediment in Guadeloupe (F.W.I.).
These two nematodes are characterized by an unstriated head
region of thickened cuticle which forms a conspicuous cephalic
capsule. Data obtained by molecular in situ hybridisation and
electron microscopy (SEM and TEM) prove that these nematodes
are associated with extracellular prokaryotes belonging to the
gamma-proteobacteria. These two species present a thick
bacterial coat constituted by a single morphotype of bacterial
ectosymbionts. The average size of these bacteria is 3µm which
are positioned all along the nematode’s body except in the
cephalic region. The ultrastructural analyses of these bacteria
show the presence of white inclusions located in the periplasmic
space which are considered as elemental sulphur granules due to
Raman microspectrometry data analysis. Such spectra permitted
to detect this compound only in the bacterial coat of these
Desmodora individuals. Nevertheless, within the Desmodoridae
family only the Stilbonematidae subfamily is characterized by an
obligate ectosymbiosis with sulphur-oxidizing bacteria covering
their cuticle in a manner that is characteristic for the genus, and
even species (Polz et al., 1992). In the actual classification the
genus Desmodora belongs to the Desmodoridae family but is not
included in the Stilbonematidae subfamily.
Due to the observations realized in this study, these two
ectosymbiotic Desmodora collected in the tropical sulfidic
environment of Thalassia testudinum could have an emended
classification in order to be transferred with the other ectosymbiotic
nematodes of the Stilbonematidae subfamily.
The impact of wood fall on marine Nematode abundance and
diversity in the mangrove swamp sediment (Guadeloupe,
F.W.I.)
Leslie C. Maurin 1 , Nadine Le Bris 2 , and Olivier Gros 1
1 UMR-CNRS 7138, Systématique-Adaptation-Evolution, Equipe
« Symbiose ». Université des Antilles et de la Guyane,
Guadeloupe. France ; 2 IFREMER Département études des
écosystèmes profonds, Plouzané, France
Abundance and diversity of nematode assemblage in the sediment
surrounding an experimentally implanted sunken wood box in the
mangrove swamp of Guadeloupe (F.W.I) were investigated at 15
days during 3 months after placement. Samples of nematodes
were taken at 0, 1, 2 and 5m distance away from the sunken wood
box. The chemical analyses of: [H2S] measured by an autonomous
probe (NKE, Inc.) directly to the bottom of the mangrove swamp
while [O2] was obtained using microsensors from push cores
realized at the same distance with an analysis at 0, 1, 2, 5, and
10cm of depth.
Preliminary results are shown indicating that the sediment is
anoxic in the first millimeters of the top muddy layer for all sites
analysed (close and far to the wood box). Concerning the H2S
measurement, in the first 15 days, an enrichment of the sediment
was observed in the vicinity of the wood box with a high
concentration (millimolar content) from 2cm depth. The same
concentrations were found at only 5cm depth for the distant sites.
At 1 month, sulphide emission by the degradation of sunken
woods is low and the sediment looses its high [H2S] concentration
in surface. First observations concerning the nematofauna along a
transect from experimentally sunken woods until 5m distance
enable to show the presence of selective and non-selective
deposit feeders (1A and 1B) nematodes close to the wood and a
majority of predators/omnivores (2B) in the sediment far away the
wood box. Preliminary data concerning the quantification and the
distribution of nematodes through a long period (1.5 months) will
be presented in order to connect chemical measurements with
abundance and diversity (family and trophic groups) of nematodes
along this transect. These results will permit to show the impact of
the sulphide emission by the wood fall degradation in mangrove
swamp on the nematofauna.