972 research outputs found
Suspended culture of <i>Ostrea edulis</i> in the Calich lagoon (North western Sardinia, Italy): preliminary results
Suspended culture is a widespread farming method used for many bivalve species such as mussels, oysters and
scallops. In the Mediterranean, this technique is mainly practised in lagoons or in sheltered coastal areas using
floating lines from which molluscs are suspended in several ways. In this study, the European flat oyster (Ostrea
edulis Linné, 1758) was grown in suspended lantern nets in the Calich lagoon (Sardinia, Mediterranean Sea) from
March 2004 to March 2005. Two distinct groups of 6 lanterns each were hung to longline ropes near the mouth (station
1) and in the central portion of the lagoon (station 2). In each lantern (diameter=50cm; height=30cm), 90 O.
edulis specimens were grown and, in order to ensure good water circulation inside the lantern net, fouling organisms
were removed every month. Overall mortality, shell length (anterior-posterior axis), shell width (maximum
distance on the lateral axis, between both valves of the closed shell) and total wet weight of a 180 specimen oyster
sample (30 from each lantern) were recorded every 2 months at each site. In addition, water temperature, salinity,
dissolved oxygen, and pH were monitored monthly by means of a multi-parametric probe at both sites (between
10a.m. and 12p.m.). One-way ANOVA was used to test for differences in oyster final mean morphometric characters
recorded at the 2 growing stations. Chi-square test (with Yates correction for continuity) was performed to compare
survival rates at the end of the trial. From an initial mean shell length of 49.5±4.6mm, O. edulis growth rate
showed a similar trend at both the stations. Nevertheless, ANOVA detected significant differences (F=7.10; p<0.01)
in final mean oyster length values (83.7±6.5mm at station 1 vs 81.7±7.6mm at station 2). Significant differences
(F=9.74; p<0.01) were also found in final mean oyster width (28.4±3.1mm at station 1 vs 27.5±2.8mm at station 2)
and weight (F=4.00; p<0.05) values (91.4±16.7g at station 1 vs 87.7±18.3g at station 2). Moreover, chi-square test
revealed a significantly different survival rate (χ2=10.04; p<0.01) between the 2 groups (57.4% at station 1 vs 47.6%
at station 2).Water temperature, salinity, dissolved oxygen, and pH monthly values recorded at the 2 growing stations
were almost identical. Thus, the observed differences in oyster growth and survival seemed not to be due to
the hydrological variables considered. Instead, they could probably be related to mechanical and chemical effects of
water renewal by coastal waters, which may have led to different seasonal seston food supplies at the 2 sites. The
suspended culture of the European flat oyster described in this paper can increase the mollusc production of the
Calich lagoon by growing a valuable bivalve species which is naturally scarce in this biotope. In fact, our preliminary
results showed good survival and growth rates of O. edulis especially near the mouth of the lagoon.
Furthermore, this farming technique could be a possible source of economic benefits for local fishermen and, above
all, a low impact aquacultural activity compatible with the environment
Bacterial flora associated with the digestive tract of gilthead seabreams reared in floating cages in the Alghero Bay (North western Sardinia, Italy): preliminary results
The intestinal microflora of fish is highly variable and can depend on many factors such as species,
developmental stage, environmental conditions, trophic habits and, in the case of farmed fish, on
rearing conditions (i.e., fish density, quality of rearing water, dietary regimen, etc.). Different studies
showed that Gram-negative bacteria such as Enterobacteriaceae and the Vibrio-Aeromonas group
dominate the fish intestine. However, since few studies have been carried out on the bacterial flora of
intensively reared marine teleosts, the aim of the present study was to investigate the microflora associated
with the digestive tract of Sparus aurata specimens reared in floating cages. A total of 30 gilthead
seabreams (mean weight 324.9±61.4 g) starved for 48 hours was sampled in autumn 2008 from a
fish farming facility located in the Alghero Bay (North western Sardinia, Italy: Lat 40°33’43.9’’N, Long
8°16’09.0’’E). The intestine between the pyloric caeca and the anus of each specimen was removed and
analysed by means of conventional bacteriological techniques using five culture media: Plate Count
Agar (PCA), Nutrient Agar (NA), Violet Red Bile Glucose Agar (VRBGA), Violet Red Bile Agar Mug
(VRBA-MUG), and de Man-Rogosa-Sharpe (MRS) agar. Total viable counts on PCA and NA were quite
similar, showing mean values of 126.7±109.0 colony forming units (cfu) per gram intestinal tissue
(between 10.0 and 495.0 cfu/g) and 108.0±101.6 cfu/g (from nil to 350.0 cfu/g), respectively. The mean
number of Enterobacteriaceae determined on VRBGA proved to be 46.3±42.8 cfu/g (from nil to 150 cfu/
g) and the VRBA-MUG mean count were 30.4±29.3 cfu/g (from nil to 95.0 cfu/g). No bacterial colonies
were instead detected using the MRS medium. These results, although preliminary, evidenced a relative
low number of bacteria associated with the digestive tract of the fish examined, thus indicating
good hygienic conditions inside the cages as well as a suitable rearing density and a balanced diet for
the seabreams
Suspended culture of Ostrea edulis in the Calich lagoon (North western Sardinia, Italy): preliminary results
Suspended culture is a widespread farming method used for many bivalve species such as mussels, oysters and scallops. In the Mediterranean, this technique is mainly practised in lagoons or in sheltered coastal areas using floating lines from which molluscs are suspended in several ways. In this study, the European flat oyster (Ostrea edulis Linné, 1758) was grown in suspended lantern nets in the Calich lagoon (Sardinia, Mediterranean Sea) from March 2004 to March 2005. Two distinct groups of 6 lanterns each were hung to longline ropes near the mouth (station 1) and in the central portion of the lagoon (station 2). In each lantern (diameter=50cm; height=30cm), 90 O. edulis specimens were grown and, in order to ensure good water circulation inside the lantern net, fouling organisms were removed every month. Overall mortality, shell length (anterior-posterior axis), shell width (maximum distance on the lateral axis, between both valves of the closed shell) and total wet weight of a 180 specimen oyster sample (30 from each lantern) were recorded every 2 months at each site. In addition, water temperature, salinity, dissolved oxygen, and pH were monitored monthly by means of a multi-parametric probe at both sites (between 10a.m. and 12p.m.). One-way ANOVA was used to test for differences in oyster final mean morphometric characters recorded at the 2 growing stations. Chi-square test (with Yates correction for continuity) was performed to compare survival rates at the end of the trial. From an initial mean shell length of 49.5±4.6mm, O. edulis growth rate showed a similar trend at both the stations. Nevertheless, ANOVA detected significant differences (F=7.10; p<0.01) in final mean oyster length values (83.7±6.5mm at station 1 vs 81.7±7.6mm at station 2). Significant differences (F=9.74; p<0.01) were also found in final mean oyster width (28.4±3.1mm at station 1 vs 27.5±2.8mm at station 2) and weight (F=4.00; p<0.05) values (91.4±16.7g at station 1 vs 87.7±18.3g at station 2). Moreover, chi-square test revealed a significantly different survival rate (χ2=10.04; p<0.01) between the 2 groups (57.4% at station 1 vs 47.6% at station 2).Water temperature, salinity, dissolved oxygen, and pH monthly values recorded at the 2 growing stations were almost identical. Thus, the observed differences in oyster growth and survival seemed not to be due to the hydrological variables considered. Instead, they could probably be related to mechanical and chemical effects of water renewal by coastal waters, which may have led to different seasonal seston food supplies at the 2 sites. The suspended culture of the European flat oyster described in this paper can increase the mollusc production of the Calich lagoon by growing a valuable bivalve species which is naturally scarce in this biotope. In fact, our preliminary results showed good survival and growth rates of O. edulis especially near the mouth of the lagoon. Furthermore, this farming technique could be a possible source of economic benefits for local fishermen and, above all, a low impact aquacultural activity compatible with the environment
Peripheral nerve sheath myxoma. Clinicopathological and immunohistochemical study of a morphologically distinctive myxoid peripheral nerve sheath tumor in the forelimb of a cat
Peripheral nerve sheath tumors (PNST) are a class of nervous system tumors which arise in both schwann
cells and perineural fibroblasts. Benign and malignant PNSTs are reported to occur in all domestic animals.
In cats they represent 3% of all cutaneous and subcutaneous neoplasms. Only in dogs mixoid PNST has
been observed generally localized in the fingers. In humans, PNSTs are rare neoplasms, and nerve sheath
myxomas are a distinct neoplasia most commonly found in limb extremities
Morphometric relationships and annual gonad index of the edible Sea urchin <i>Paracentrotus lividus</i> from North Western Sardinia = Relazioni morfometriche e indice gonadico annuale del riccio di mare commestibile <i>Paracentrotus lividus</i> nel nord ovest Sardegna
Weight/diameter, weight/height and height/diameter morphometric relationships were calculated for a shallow rocky Paracentrotus lividus population sampled monthly near Alghero (Italy) from November 2004 to October 2005. Gonad index (GI) of the sea urchins was also evaluated. Statistical analyses showed significant differences of GI between 2 distinct periods of the year: late fall-winter and spring-late summer
Thin corrugated-edge shells inspired by Nervi’s dome: Numerical insight about their mechanical behaviour
During the last decades, the constant evolution of the construction systems has led to the possibility of carrying out increasingly complex architectural project. Among the wide range of construction systems, thin concrete shells with corrugated-edge stand out for their relevance.
In this paper, the mechanical behaviour of thin concrete corrugated-edge shell inspired by Nervi’s Flaminio dome has been analysed in detail, considering different load configurations (self-weight, uniform normal pressure and antisymmetric vertical load) and constraints (pure membrane vs. displacements restrained boundary conditions).
Non-linear static analysis has been performed to assess the vertical load-bearing capacity of the corrugatededge shell considering a Concrete Damaged Plasticity (CDP) constitutive model and linear and non-linear buckling analyses have been carried out to evaluate the effects of the corrugation on buckling behaviour.
The results obtained from linear and non-linear analyses have been compared with those obtained for a concrete thin smooth-edge shell having the same geometric global characteristics. The comparison highlighted improvements provided by corrugated-edge in terms of structural behaviour
Natural and man-made terrestrial electromagnetic noise: an outlook
The terrestrial environment is continuously exposed to electromagnetic radiations which set up a «background»
electromagnetic noise. Within the Non Ionizing Radiation band (NIR), i.e. for frequencies lower than 300 GHz,
this background can have a natural or an artificial origin. Natural origins of electromagnetic radiations are generally
atmospheric or cosmic while artificial origins are technological applications, power transmission, communications,
etc. This paper briefly describes the natural and man-made electromagnetic noise in the NIR band.
Natural noise comes from a large variety of sources involving different physical phenomena and covering a wide
range of frequencies and showing various propagation characteristics with an extremely broad range of power
levels. Due to technological growth man-made electromagnetic noise is nowadays superimposed on natural
noise almost everywhere on Earth. In the last decades man-made noise has increased dramatically over and
above the natural noise in residential and business areas. This increase has led some scientists to consider possible
negative effects of electromagnetic waves on human life and living systems in general. Accurate measurements
of natural and man-made electromagnetic noise are necessary to understand the relative power levels in
the different bands and their influence on life
Response of captive seabass and seabream as behavioural indicator in aquaculture
Welfare of cultivate fish at high-density represents an important concern for modern aquaculture.
The behaviour of European seabass (Dicentrarchus labrax) and seabream (Sparus aurata) reared in cages was studied
in a fish farm of northern Sardinia (Italy) in autumn 2006 to test whether captive condition had an effect on
the movement patterns of these two species.Video images recorded before, during and after the manual feeding distribution
allowed us to collect data on different behaviours of captive fish. Thus, behaviours indicating the position
of fish in the water column, swimming direction and possible aggressive behaviours (aggression, direction change
and collision) showed juveniles and adults of seabass and seabream were overall affected by feeding rhythms and
captive overcrowding. Seabream had a major tendency to swim towards the bottom and higher frequency of horizontal
swimming and collisions than seabass. The overall behavioural difference between two species was explained
in terms of their differences in ecological features in the wild
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