1,721,003 research outputs found
Seasonal variations in biochemical composition and condition index of cultured mussels (Mytilus galloprovincialis Lmk.) in the Lagoon of Venice (North Adriatic).
No full textSeasonal changes in the main biochemical components and in the condition index of cultured mussels (Mytilus galloprovincialis Lmk) from the Venice Lagoon have been followed during the period October 1979–August 1981.
Carbohydrates (2–32%) show winter minima and summer maxima, while proteins (30–52%) have a rather irregular pattern. Lipids (2–13%) and condition index exhibit an annual cycle with two minima (late spring; autumn-winter) and two maxima (early spring; summer).
Seasonal variations of biochemical composition and condition index are discussed in connection with the reproductive cycle and some environmental parameters such as temperature and phytoplankton availability.
The comparison between the present data and those from other geographic areas confirms the peculiarity of the environment of the Venice Lagoon
Influence of temperature and salinity on embryonic development of Paracentrotus lividus (Lmk., 1816).
No full textThe combined effects of temperature and salinity on early development of the sea urchinParacentrotus lividus (Lmk, 1816) are reported. The optimal temperature-salinity combinations for development are 18 °–20 °C and 34–35‰; there is a significant temperature-salinity interaction. The optimal conditions found in the experiments are above the mean yearly values for the sampled population's environment (North Adriatic Sea), being more similar to those of the Tyrrhenian Sea. These results suggest that embryonic tolerances to temperature and salinity are under genetic and not environmental control
Reproductive cycle of the mussel (Mytilus galloprovincialis Lmk.) in Venice Lagoon (North Adriatic).
No full textThe reproductive cycle of Mytilus galloprovincialis Lmk cultured in Venice Lagoon has been studied from 1979 to 1982. Histology of the gonads shows that the gametes are ripe from September to May, when several spawnings occur with a peak at the end of winter (January -February). Reproductive activity is quiescent between July and August but release of gametes is possible even in summer, if only to a limited extent
Effects of linear alkylbenzene sulphonate (LAS) on skeletal development of sea urchin embryos (Paracentrotus lividus Lmk).
No full textLinear alkylbenzene sulphonate (LAS) acts on the zygotes of the sea urchin Paracentrotus lividus, inducing total inhibition of skeletal development at concentrations higher than 0.45 ppm and a significant decrease at concentrations of 0.30 ppm. The effect of the surfactant is maximum at the end of gastrulation, when calcium uptake is very high, presumably related to the beginning of skeletal growth. This suggests that, in the environment, the sequestering action of LAS on calcium may significantly affect the availability of this ion for morphogenesis. Nevertheless, the experimental data presented in this paper suggest that the toxic action of LAS is also exerted at levels other than those involved in calcium uptake
Effects of linear alkylbenzene sulphonate (LAS) on two marine benthic organisms.
No full textThe effects of dissolved linear alkylbenzene sulphonate (LAS) on two marine benthic filter-feeders, the sea-squirts Botryllus schlosseri and Botrylloides leachi, were tested. The survival and growth rates of both species were significantly affected at LAS concentrations ranging from 0.25 to 0.50 ppm. Larvae were apparently more resistant than adults. However, treatments beginning at the pelagic stage strongly affected the negative response of the next benthic phase, although the pelagic stage only lasted 1.5% of the total duration of the treatment, indicating that the effects of LAS are exerted mainly on this phase of the life cycle
Insediamento di larve di bivalvi su collettori artificiali in unâ€TMarea a barriere artificiali nel Nord Adriatico.
No full textAbstract: From December 2003 to November 2004 a research project on larval settlement of bivalves was carried out in the Northern Adriatic Sea, using some series of collectors (“Chinese cap”) suspended at -2 and -10 m depth. The study revealed the period and density of settlement, as well as the bathymetric preferences of certain species of bivalves. These studies contribute to the knowledge of the distribution of bivalve larvae in the sea environment
Early development of sea urchin eggs (Paracentrotus lividus Lmk.) in artificial media.
No full textThe early development of Paracentrotus lividus was examined in natural sea water and in two artificial media (a commercial sea water and one prepared in the laboratory). The observations were carried out up to 40 hours (at 25°C) after fertilization when the embryos were at the echinopluteus stage. The developmental rate in the tested waters did not significantly differ but the mean size of the echinopluteus did; it was usually greater in laboratory water. These results indicate that up to the echinopluteus stage embryonic development is completely "endotrophic", since it does not necessarily require the several biologically active substances present in natural sea water. The use of a laboratory standard water may be recommended for short-time bioassays using P. lividus as test-organism
Insediamento, reclutamento ed accrescimento di bivalvi eduli su strutture in sospensione nellâ€TMarea del campo sperimentale.
No full textABSTRACT - From December 2003 to November 2004 a research project on the larval settlement of bivalves was carried out in the “Campo Sperimentale”. Each sample consisted of two sets of artificial collectors, consisting each of ten “chinese caps”, ten “pegs” and four “bags”, were tied to a suitable surface long-line system and suspended at -2 and -10 m depth. So each sample consisted of 48 collectors. From December 2003 to November 2004 ten samples were plunged and recovered after about a month, and four after three months. The peak of settlement was in spring-summer period, mostly in August for families Mytilidae, Pectinidae and Veneridae, although some families, as Anomidae and Hiatellidae, settled mainly during the winter season. In August some species of worthless Mytilidae, as Modiolarca subpicta (Contraine, 1835) and Modiolula phaseolina (Philippi, 1844), were rather abundant (188 ind/m2/day on “caps” at 10 m), whereas Mytilus galloprovincialis (Lamarck, 1819) settled between April and July with lower abundance values, mainly on “pegs” and “bags” at 2 m depth. Pectinidae species, Chlamys varia (Linnaeus, 1758), Proteopecten glabra (Linnaeus, 1758) and Aequipecten opercularis (Linnaeus, 1758), present during the whole study period, were mostly abundant in summer (up to 267 ind m-2 day-1) and showed a higher settlement on “bags” and “chinese caps” at 10 m depth. Veneridae, mostly Paphia spp., were rather low (max 36 ind/m2/day on “caps” at 2 m). M. galloprovincialis and Veneridae clearly preferred the most surface collectors, whereas Pectinidae preferred the deepest ones. Moreover, in order to define a suitable spat harvesting strategy throughout the different year periods, a calendar of the settlement, which may be useful for the shellfish producers, was assessed
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