Effects of larval cryopreservation on subsequent development of the blue mussels,Mytilus galloprovincialis Lamarck

In this study, the effects of three commonly used chemicals, dimethyl sulphoxide (DMSO), ethylene glycol (EG), propylene glycol (PG) and their combinations with trehalose, were evaluated on the cryopreservation of D‐larvae of the blue mussel Mytilus galloprovincialis. The larvae were harvested 30 h post‐fertilization at 21 °C and cryopreserved using a standard protocol in 5%, 10% or 15% of DSMO, EG and PG either as single chemical solutions or in combination with 0.2 M trehalose. Among these cryoprotectants, 5% DMSO resulted in the highest post‐thaw survival rate of 55.3±7.8%, although it did not significantly differ from those with 10% and 15% EG. The addition of 0.2 M trehalose did not improve the post‐thaw larval survival rates in all the combinations assessed. The cryo‐effects on subsequent development were evaluated using the D‐larvae frozen with 5% DMSO. The results showed that cryopreservation affected both larval survival and growth in this species. The relative daily mortality rate was significantly higher in treated than control groups over the period from 3 h post‐thaw to day 11 post‐fertilization. On day 6 post‐fertilization, the average larval length in the treated group was significantly smaller than that in the control. From day 11 post‐fertilization, and onwards, differences in these two traits were not significant between treated and control groups. On day 21 post‐fertilization, about 80% of the larvae in both treated and control groups developed eyes and the normalized survival rate in the treated group was 12.5%.     

Depuration of mussels (Mytilus galloprovincialis) contaminated with domoic acid

Domoic acid is a neurotoxin responsible for the Amnesic Shellfish Poisoning (ASP). With the aim of determining its depuration kinetics in raft mussels Mytilus galloprovincialis and the effects of body weight, salinity and temperature on it, an experiment involving these factors was carried out. Mussels which had incorporated this toxin to a concentration of 153 μg·g^–1 of soft tissue during a bloom of the pennate diatom Pseudo nitzschia australis, were collected from the Galician Rías and placed at temperatures of 18 and 22 ºC and salinities of 12.5 and 31. Mussel samples were taken at the start of the experiment and daily during the four subsequent days and the domoic acid contents of the soft tissues were analysed. The simple one-compartment kinetics, that is a kinetics in which all toxin depurates at the same rate, was fitted to the data, with good quantitative results. Notwithstanding, the deviations of the model from the actual data were dependent on time, suggesting that such a simple model is not enough to correctly describe the data, and that a more complex kinetics may be more adequate. A two-compartment kinetic model, in which two pools of toxins exist (compartments), each one depurating at different rate, described qualitatively better the depuration but its quantitative contribution to the fit was not statistically significant. The parameters of the model, obtained by least squares fitting, suggest the possibility of a small second compartment of very small or null depuration rate, as detected in other species. This kind of model would explain the reduced quantitative contribution of the second (slowly depurating) compartment.Low salinity was shown to reduce the depuration rate. The two other factors checked, temperature and body weight, nor any interaction had significant effect on depuration rate.     

Changes in extractive components in live Mytilus galloprovincialis mussels during ice storage

Extractive components of live mussels during ice storage for 13 days were investigated to determine changes in the quality of the mussels. The quality of live mussels was estimated using a taste active value (TAV), an equivalent umami concentration (EUC), and a hierarchical cluster analysis heat map, which were calculated from the extractive components. The extractive components with TAV greater than 1 were glutamic acid, alanine, adenosine monophosphate, and succinic acid during the storage period and aspartic acid up to day 10, whereas the TAV of glycine and inosine monophosphate was less than 1 after day 3. EUCs decreased from 4.38 mg MSG/100 g on day 0 to 3.28 mg MSG/100 g on day 13. Based on the cluster analysis of the metabolite composition and viable bacterial counts, ice-cold live mussels were divided into three clusters: I (days 0–1), II (days 3–10), and III (day 13). Considering not only the decrease in TAV and EUC but also the results of the cluster analysis, it is suggested that live mussels maintain high quality up to the 1st day of ice storage, and thereafter, the quality will be reduced gradually during storage on ice.

     

Survival and growth of local and transplanted blue mussels (Mytilus trossulus, Lamark)

Consumer demand for fish and shellfish has led to an increase in aquatic species movement for aquaculture purposes. One potential drawback to the successful transplantation of animals for aquaculture is unpredictable performance due to local adaptation effects. This study used a common environment experiment to examine the potential for local adaptation in Mytilus trossulus (Lamark) on the east coast of Vancouver Island, British Columbia (BC). Newly settled mussels were collected from two sites, Chemainus and Quadra Island (approximately 150 km apart), reared in cages at the Quadra collection site, and mortality and shell length were monitored. Mussels were cage‐reared for 384 days with an overall survival of 59% (Quadra) and 39% (Chemainus). The Quadra mussels were initially smaller (5.07 mm) than the Chemainus mussels (5.90 mm), but the two were similar at the end of the experiment (23.5 and 23.6 mm). Transplanted mussels had a significantly higher mortality over the course of the experiment, primarily due to a severe episode in the early summer, and had significantly lower relative growth rates at three of 11 measurement dates. Overall, the local mussels performed better than the transplanted mussels. This study demonstrates the potential for local adaptation effects between populations of mussels separated by only a relatively small geographic distance.     

Settlement of mussels (Mytilus galloprovincialis Lamarck) on rope collectors in the estuary of the River Krka,Yugoslavia

The 25-km² estuary of the River Krka, Yugoslavia, supports a large natural population of mussels. Artificial culture on hanging ropes is now beginning, and for this it is necessary to know the best areas, depths and times for settlement and collection of seed. In this experiment, plastic rope test collectors were set each month from May 1981 to April 1982 at three sites. After 2 months, settled mussels were removed from collectors. Water temperature and salinity measurements were made weekly at each site. Maximal settlement at the two upstream sites was found in September, when 350 and 485 mussels were recovered from 125 cm² of rope at 2 m depth. However, at the site further downstream, good settlement occurred throughout the year, peaking at 5250 mussels per 125 cm² of rope at 3 m depth during April. Such productive sites will be extremely useful in supplying seed for mussel farms in this area.     

Effect of temperature on survival,growth and development of Mytilus galloprovincialis larvae

Mussel aquaculture is widely prevalent worldwide, but generally relies on natural seed collection, which does not always meet the needs of the producers. Thus, development of mussel hatcheries is of economic interest in some parts of the world, such as Europe; it provides opportunities not only on annual reliability of seed but also on genetic improvements. To broaden knowledge on mussel larval physiology, we carried out temperature treatments (17, 20 and 24 °C) on Mytilus galloprovincialis larvae under laboratory conditions. The trials ended when 30% of the larval population was in the post‐larval stage. The temperature coefficient Q₁₀ indicated a strong relationship between temperature and increase in growth from 17 to 20 °C, but not between 20 and 24 °C. Exposure of M. galloprovincialis larvae to 17 °C resulted in poor growth, low survival and a delayed development and was considered to be inadequate for M. galloprovincialis larval culture. Rearing the larvae at 20 or 24 °C produced better growth, higher survival rates and faster metamorphosis as compared with 17 °C. The temperature region within 20 and 24 °C was suggested as adequate for the mussel M. galloprovincialis larval culture, and implications of these results on the development of commercial hatcheries were discussed.     

Cryopreservation of strip spawned sperm using non‐programmable freezing technique in the blue mussel Mytilus galloprovincialis

In this study, a non‐programmable freezing technique has been developed with the strip spawned blue mussel (Mytilus galloprovincialis) sperm. The key parameters optimized including (1) cryoprotectant agents (CPAs); (2) cooling temperature; (3) thawing temperature; (4) sugar and amino acid supplementation and (5) sperm to egg ratio. The fertilization rate and/or integrity of plasma membrane and acrosome were used as sperm quality assessment indicators. The highest post‐thaw sperm fertilization rate of 95% was achieved, when sperm were cryopreservated in 8% dimethyl sulfoxide at 7.8 cm above the liquid nitrogen surface and thawed in a 60°C seawater bath. The addition of glucose, sucrose or trehalose in dimethyl sulfoxide did not, whereas 0.8% glycine did significantly improve the post‐thaw sperm fertilization rates. The fluorescent evaluation has demonstrated that the addition of glycine significantly improved the post‐thaw sperm acrosome integrity, revealing a positive role of glycine in the improvement of post‐thaw sperm quality in blue mussels.     

Cadmium,lead and metallothionein contents in cultivated mussels (Mytilus galloprovincialis) from the Gulf of Naples (Southern Italy)

The concentration of cadmium and lead ions was determined in digestive gland and mantle of mussels (Mytilus galloprovincialis) from five aquaculture stations located in the Gulf of Naples (Southern Italy, Tyrrhenian Sea). Metallothionein (MT) levels in the same tissues were also evaluated. This gulf represents a greatly urbanized area, characterized by an important commercial port and past industrial activities, terminated in the last decade of the 20th century. The results were compared with those obtained from mussels cultivated in a more pristine neighbouring area. Data demonstrate that the amount of both metals found in mussels harvested at the highly anthropogenic sites in the Gulf of Naples was comparable with that found in mussels from the more naturalistic site. The content of both cadmium and lead was not related with that of MT. Indeed, the amount of both metals in the digestive gland was greater than in the mantle, whereas the MT preferentially accumulated in the mantle. Possibly, the MT content in mantle was associated to the physiological function of the tissue, rather than heavy metals exposure.     

Nutritional Value of Preserved Microalgae for Subadult Mytilus galloprovincialis

Abstract.— Subadult (4–5 cm) Mytilus galloprovincialis were fed for 31 d with equal daily rations, equivalent to 6% of their body weight on a dry weight basis, of Chaetoceros sp. and Phaeodactylum tricornutum fresh, or preserved by air-drying, freeze-drying, and by freezing. At the end, increases in size, in dry weight, and in condition index with preserved diets were significantly lower than those of the mussels fed with live algae. In general, the frozen diets were better than the air- and freeze-dried ones. Increases with live Chaetoceros sp. were greater than with live P. tricornutum ; however, with preserved diets the latter was better than Chaetoceros sp .     

The effect of environmental factors, depth and position on the growth and mortality of raft-cultured blue mussels (Mytilus edulis L.)

One‐year‐old rope grown blue mussels (Mytilus edulis L.) were grown in experimental lantern nets at two depths (2 and 6 m below the surface) in two different positions (inflow and outflow) off a raft in Loch Etive on the west coast of Scotland. Shell and tissue growth, and mortality were recorded. Water temperature, salinity and food availability were also monitored over the experimental period. There were no significant differences in the length, live weight, wet meat weight, dry meat weight and ash‐free dry meat weight between depths (P > 0.05). However, position had a significant effect on these parameters as mussels located at the inflow of the raft differed significantly from those at the outflow of the raft (P < 0.05). Particulate organic matter (POM) and chlorophyll a (Ch a) were significantly higher at the inflow than the outflow of the raft (P < 0.05), but depth had no effect on POM and Ch a (P > 0.05). The results show that food concentration was higher in the inflow of the raft than the outflow. In the light of these results, recommendations for better management of Scottish raft mussel cultivation are discussed.     

Growth and condition index of mussel Mytilus galloprovincialis in experimental integrated aquaculture

Integrating mussel and finfish aquaculture has been recognized as a way to increase profits and decrease environmental impacts of finfish aquaculture, but not enough is known about the effects of finfish aquaculture on mussel growth. Here we present a pilot study aimed at determining how distance from finfish aquaculture affects mussel growth. To this end, we measured growth and condition index of mussel (Mytilus galloprovincialis) at three different distances (0, 60 and 700 m) from finfish aquaculture in the eastern Adriatic Sea. There was a statistically significant difference in growth of tagged mussels with respect to site. Average measured lengths of mussels at sites 1, 2 and 3 after the 10 months of the experiment were 57.60, 62.73 and 58.66 mm. Mussels grew fastest from March to May, and slowest from July to September, regardless of their position. Condition index showed spatial and temporal variations with higher values during fall and winter (∼23), and lower values during spring and summer (∼20). Our results show that production cycle in areas traditionally considered suboptimal for aquaculture can be equivalent to the cycle in areas traditionally considered optimal for mussel aquaculture if mussel aquaculture is integrated with finfish aquaculture.     

海水酸化胁迫对紫贻贝能量分配的影响

2016年5～6月在山东桑沟湾楮岛海区,采用野外围隔和现场流水相结合的方法,以紫贻贝(Mytilus galloprovincialis)为研究对象,以pH为8.0作为对照组,探讨了酸化胁迫(p H=7.7)对其能量分配的影响。结果显示,短期(10d)海水酸化胁迫下,紫贻贝的滤水率、同化效率、氧氮比显著下降(P0.05),排氨率极显著增加(P0.01),耗氧率无显著差异(P0.05);中期(30d)海水酸化胁迫下,紫贻贝的滤水率和氧氮比显著下降(P0.05),而同化效率、耗氧率、排氨率显著升高(P0.05)。能量收支的结果显示,短期(10 d)酸化胁迫下,紫贻贝的摄食能和吸收能显著降低(P0.05),呼吸能无显著差异(P0.05),排泄能显著增加(P0.05),生长余力极显著降低(P0.01);中期(30d)海水酸化胁迫下,摄食能降低(P0.05),吸收能、呼吸能、排泄能、生长余力显著升高(P0.05)。氧氮比的结果显示,在海水酸化胁迫下,氧氮比的波动范围为14.28～20.46,贝类体内的供能物质由脂肪和碳水化合物逐渐向蛋白质过渡。研究结果为揭示紫贻贝应对海水酸化胁迫的生理响应提供了基础数据。     

Comparative growth of cultured blue mussels, Mytilus edulis, M. trossulus and their hybrids, in naturally occurring mixed-species stocks

In Atlantic Canada, both Mytilus edulis and M. trossulus occur naturally in sympatric populations and readily hybridize forming genotypically complex assemblages that vary widely in relative species composition throughout the region. We monitored growth in single year‐class cohorts of rope‐cultured Mytilus spp. during a 14‐month period from sleeving of seed to harvest at three commercial mussel farms in Notre Dame Bay, Newfoundland, Canada. Electrophoretic variation at the mannose phosphate isomerase (Mpi) enzyme locus was used to categorize the two species (M. edulis and M. trossulus) and their hybrids. Seed populations varied significantly among sites in relative proportions of each species and hybrids. Growth in shell length, wet weight and shell weight varied significantly with Mpi genotype at all three farm sites. Growth in flesh weight varied significantly with Mpi genotype at two of the three sites. Growth rates for all weight variables were consistently significantly greater in M. edulis than in sympatric M. trossulus. Growth in shell length was significantly different between sympatric M. edulis and M. trossulus at only one farm site. Growth rates of hybrids were typically intermediate between sympatric M. edulis and M. trossulus, but were often statistically similar to one or other of M. edulis or M. trossulus. We conclude that the production of rope‐cultured blue mussels in Atlantic Canada is significantly influenced by genotype‐dependent growth variation in naturally occurring mixed‐species stocks. Our results also suggest that farm site production may be increased and intrasite variability reduced at farm sites currently using indigenous mixed‐species stocks by substitution and growout of transplanted seed from unispecific M. edulis stocks.     

紫贻贝和厚壳贻贝杂交及F1代杂交优势初探

2005-2007年对紫贻贝(Mytilus gallo provincialis)和厚壳贻贝(Mytilus coruscus)种间进行了杂交生产性试验,通过亲贝强化培育、确认雌雄亲贝、改革育苗水体交换方法、投喂混合单细胞藻类、流水培养附着稚贝等技术,获得F1代.结果表明,正交F1代幼虫的成活率明显高于反交F1代和厚壳贻贝,在幼虫培育前期与紫贻贝的成活率相当,但随着幼虫的发育有高于紫贻贝的趋势.正交F1代幼虫的壳长和壳高在培育阶段的前期生长与紫贻贝相当,低于厚壳贻贝,高于反交F1代;但后期的生长明显增快,并高于反交F1代和其他两种贻贝.各试验组贻贝海区养殖的成活率在90%以上,正交F1代最高,显著高于反交F1代.各试验组生长特性,正交F1代紫贻贝厚壳贻贝反交F1代.其中正交F1代获附着稚贝3.77×109 ind.正交F1除在孵化率上低于紫贻贝、厚壳贻贝外,在壳长、壳高、成活率等方面指标具有一定杂交优势,而反交F1代的杂交优势不明显.     

Effect of different ions on larval metamorphosis of the mussel Mytilus galloprovincialis

Metamorphic responses of pediveliger larvae of Mytilus galloprovincialis to different ions were investigated through a series of bioassays. Effects of tetraethylammonium chloride (TEA) on inductive effects of these above ions were also investigated. Excess ions including Li⁺, Cs⁺, Rb⁺ and Ca²⁺ induced larval metamorphosis at 10^?3 M to 5 × 10^?2 M in 24‐h exposure assays. In continuous exposure assays, only excess Ca²⁺ showed inductive activity and induced 25% metamorphosis at 5 × 10^?2 M. Larval responses to Li⁺ and Rb⁺were inhibited by TEA, while induction of metamorphosis by Cs⁺and Ca²⁺ was independent of the presence of TEA. Thus, these ions used can be useful inducers of larval metamorphosis for application in the aquaculture industry. The finding provides new insights on the biochemical mechanism controlling larval metamorphosis in this species.     

Effects of stocking density on survival,growth and biochemical composition of cultured mussels (Mytilus galloprovincialis,Lamarck 1819) from an offshore submerged longline system

This study examined an offshore submerged mussel longline system, in the Black Sea, from May 2009 to May 2010. The system was allowed 1 year for spat collection. After a 1‐year spat collection period, some spat collectors were left untouched (NS), and some spat collectors were grazed and socked (S) for a grow‐out study in May 2009. The effects of stocking density on the growth and survival of the S and NS mussels were examined. The biochemical composition of the mussels was also determined. Environmental factors including temperature, salinity, chlorophyll a, total suspended matter, inorganic matter and organic matter were monitored monthly during the experimental period. In May 2010, the mean length and live weight of the S and NS mussels were 60.46 ± 0.60 mm and 53.34 ± 0.37 mm, respectively, and 20.50 ± 0.50 g and 13.11 ± 0.26 g respectively. Mean moisture and ash were 82.35 ± 0.47% and 6.67 ± 0.44% respectively. Mean carbohydrate, protein and lipid were 27.74 ± 2.40%, 57.68 ± 2.15% and 7.91 ± 0.68% respectively. These results indicate that a submerged offshore mussel culture system in the Black Sea can be commercially convenient. In addition, stock management via thinning out of the spat can considerably increase the marketable size of mussels, reduce harvest time and produce better growth.