Effect of antibiotic treatment on the growth and survival of juvenile northern Chilean scallop, Argopecten purpuratus Lamarck (1819), and associated microflora in experimental cultures

Juvenile northern Chilean scallops of 937±55 μm shell height were exposed to five different concentrations of chloramphenicol (CHL) (5, 10, 25, 50 and 100 μg mL⁻¹), plus a control without antibiotics. To determine the effect of CHL on the accompanying microflora, the number of colony-forming units (CFU) that grew on TGE culture medium was counted in the seawater of containers with juveniles, and in containers with microalgae used as food. Both were exposed to the same concentrations of CHL. The growth rates of juveniles treated with CHL and the control without antibiotic showed highly significant differences ( P =0.0001). The growth rate was inversely proportional to the CHL concentration. The control sample presented the highest growth rate (84.4±14.3 μm day⁻¹), followed by the sample treated with 5 μg mL⁻¹ (64.2±14.3 μm day⁻¹). The survival in the control and in the treated samples with 5–50 μg mL⁻¹ was rather high, with a mean value of 95%. Only the sample treated with 100 μg mL⁻¹ had a low survival (36.7%). The CFU count was larger in the containers with juveniles, when compared with the ones with food. The CFU count tended to decrease with increasing CHL concentration in the juveniles.     

The culture of the southern bay scallop in Tampa Bay, an urban Florida estuary

Bay scallop, Argopecten irradians concentricus (Say), stocks were collected from a Homosassa (Florida) population in 1991 and were kept in seawater from Bayboro Harbor on Tampa Bay, an urban Florida estuary. They were fed with Isochrysis galbana and Tetraselmis sp. Spawning was allowed to occur after the scallops became ripe. The hatching rate of the F1 eggs to D-shaped larvae was 72%. Settlement and metamorphosis began 11 days after fertilization. When spat reached a shell height of 0.8 mm in the laboratory, they were placed with substrates into 300 and 800 m mesh bags, and later in lantern nets, suspended from a dock in Bayboro Harbor. The F1 scallops successfully survived to gonad maturity in the fall of 1992, with mean (sd) shell height of 49.8 (4.0) mm on 6 September 1992. The scallops experienced heavy mortality during the summer, partially as a result of heavy fouling. From early August to October of 1992, F1 scallops grown in Bayboro Harbor were successfully spawned in the laboratory. Growth and survival of the F2 scallops were comparable to those of the F1 scallops. Results have shown that bay scallops can complete an entire life cycle in an urban estuary such as Tampa Bay, and a hatchery for bay scallops on the estuary can assist in the restoration of the population. Fouling represents a possible severe limitation and alternatives to caging for grow-out should be considered.     

镉对海湾扇贝的急性毒性研究

利用水生生物毒性试验方法,分5个浓度进行Cd2 对海湾扇贝的急性毒性实验,利用概率单位和浓度对数作线性回归,得出Cd2 对海湾扇贝在24、48、96小时的半致死量LC50,其值分别为5．85、4．52、3．45mg/L。并计算出Cd2 对海湾扇贝的安全质量浓度为0．0345 mg/L。     

海湾扇贝杂交家系与自交家系生长和存活的比较

2002年春季,利用国内现有的海湾扇贝两个不同遗传背景的养殖群体A和B的种贝为材料,采用自体受精和异体受精两种交配策略,建立了海湾扇贝的自交系和杂交系。实验由AA(A♀×A♂)、BB(B♀×B♂)、AB(A♀×B♂)、BA(B♀×A♂)四个组组成。杂交使两个表型性状———生长和存活都得到了改良。就生长而言,杂交组比自交组快,杂种优势在幼虫期为35.34%、养成阶段为21.17%;杂交组AB的生长速度比自交组AA的提高了35.53%(幼虫期)和43.32%(养成阶段),杂交组BA的生长速度比自交组BB的提高了35.13%(幼虫期)和12.34%(养成阶段)。就存活而言,两个杂交组的存活率都高于相应的自交组,杂种优势的平均值在幼虫期为19.93%,养成阶段为31.46%;杂交组AB的存活率比自交组AA的提高了25.23%(幼虫期)和49.44%(养成阶段),杂交组BA的存活率比自交组BB的提高了12.36%(幼虫期)和21.29%(养成阶段)。A、B两个群体间存在的遗传差异是它们能够获得杂种优势和性状得到改良的基础。     

Energetic physiology of the Caribbean scallops Argopecten nucleus and Nodipecten nodosus fed with different microalgal diets

The Caribbean scallops Argopecten nucleus and Nodipecten nodosus are currently being placed into mass culture in Colombia. The limited availability of wild seed upon which to base these cultures has promoted research into the development of artificial production of this seed in hatcheries. In support of this effort, we studied the effects of different diets on the physiology of the two scallop species in order to determine the optimal feeding regimes for maintenance of adult specimens in the laboratory. Seven monoalgal diets were tested, including Chaetoceros calcitrans, Chaetoceros muelleri, Isochrysis galbana (Ig), Nannochloris oculata (No), Phaeodactylum tricornutum (Pt), Tetraselmis chui (Tc) and Tetraselmis tetrahele (Tt). Four mixed diets were also tested, including I. galbana + C. calcitrans (Ig + Cc), I. galbana + N. oculata (Ig + No), I. galbana + T. tetrahele (Ig + Tt), and I. galbana + lipid emulsion of docosahexanoic acid DHA (Ig + lip). All the dietary trials were carried out under uniform conditions of temperature (25 °C), salinity (36‰) and algal concentration (0.45 mg L^− 1). Physiological variables measured in association with each diet included feeding rates (clearance, ingestion and absorption), oxygen consumption and ammonium excretion rates as well as their scope for growth. The results showed that the best scope for growth for both scallops was obtained with diet Ig since this diet induced the highest feeding rates, accompanied by the lowest oxygen consumption and ammonium excretion. The feeding rates and scope for growth of A. nucleus were greater than those of N. nodosus for the majority of the diets, which was attributed to a higher rate of water pumping by the former species. Greater capacity for branchial food retention by A. nucleus was discarded as a possibility since N. nodosus had a greater branchial surface area per unit dry weight than A. nucleus. In spite of these differences, the oxygen consumption and the excretion rates were similar between the two scallops which suggested that A. nucleus was more efficient in its use of oxygen and retention of body proteins for physiological functioning. Mixed diets or addition of DHA did not permit increases in scope for growth in either of the scallops over that observed using monoalgal diet Ig, which suggest that biologically and economically this diet is optimal for the feeding of adult scallops in the laboratory.     

Effects of temperature on non-specific immune parameters in two scallop species: Argopecten irradians (Lamarck 1819) and Chlamys farreri (Jones & Preston 1904)

The effect of chronic (2 weeks) temperature (19, 22, 25, 28 and 31°C) on certain non‐specific immune parameters of two species of scallops, Argopecten irradians (Lamarck 1819) and Chlamys farreri (Jones & Preston 1904) were studied. The survival ratio of the two species of scallops at 31°C was the lowest. Haemocyte concentration of C. farreri in the 19 and 22°C treatment groups was significantly lower than that of the 25 and 28°C treatment groups but significantly higher than that of the 31°C treatment group. With elevation of seawater temperature, the alkaline phosphatase (ALP) and acid phosphatase (ACP) activities in sera of two scallop species increased and reached the peak at 25°C and then decreased. However, the specific activity of ALP and ACP of the 31°C treatment group was the highest. The results demonstrated that temperature of seawater significantly affected immunity of scallops. The concept that the stress of high environmental temperature on C. farreri may be partially responsible for the mass mortality of the organism is also introduced.     

Reproductive conditioning of Chilean scallop (Argopecten purpuratus) and the Pacific oyster (Crassostrea gigas): effects of enriched diets

The quality of diet fed to bivalve broodstock during reproductive conditioning directly affects growth and survival of their larval and postlarval progeny. The objective of the present study was to improve the quality of larval production in the Chilean scallop (Argopecten purpuratus) and the Pacific oyster (Crassostrea gigas) by testing of the effects of different experimentally enriched diets on the conditioning and early development of progeny under laboratory conditions. The diets used included protein-rich microalgae and mixtures of microalgae and lipid emulsions. Quality of D-larvae, pediveligers, and 1-mm postlarvae from the variously fed broodstock was measured to evaluate each diet as indicators of growth and survival of the early life stages. Biochemical analyses were carried out on eggs and larvae to determine the effects of the different diets on these parameters. The main results for the scallops and oysters were that a conditioning diet containing algae rich in protein improved larval growth and survival. This effect did not, however, extend past metamorphosis. Also, the best conditioning diet increased the lipid content of the eggs, as well as the protein content of the D-larvae, although the mechanism for this remains unclear.     

有效预防海湾扇贝面盘幼虫解体病的试验

扇贝的面盘幼虫解体病的发病主要因素为亲贝性腺发育不成熟所致。预防的有效措施,应在亲贝促熟上下功夫。利用发生面盘幼虫解体病的亲贝进行了生产性育苗实验研究,并取得了成功,培育出海湾扇贝稚贝20亿枚,单位水体出苗量368万枚/m3。     

紫扇贝和墨西哥湾扇贝种间杂交的初步研究

针对墨西哥湾扇贝养殖过程中出现的问题,采用种间杂交技术来对墨西哥湾扇贝进行种质改良。以墨西哥湾扇贝(Argopecten irradians concentricus)和紫扇贝(A. purpuratus)为亲本进行种间杂交试验,养殖过程中对生长发育的相关数据进行测量并分析。结果表明：各群体受精率和孵化率均达到90%以上,其中MZ的受精率最高,MM的孵化率最高。在育苗和养成阶段,杂交群体MZ的生长速度大于自交群体MM和ZZ。在幼虫期MZ的生长速度最快,壳高日增长量为6.58 μm/d,壳长日增长量为6.67 μm/d。在养成期MZ的壳高日增长量为0.33 mm/d,壳长日增长量为0.36 mm/d,体重日增长量为0.23g/d,至收获时,杂交贝比墨西哥湾扇贝平均壳高、壳长和体重分别大24.65%,27.40%和85.14%,杂种优势十分明显。     

海湾扇贝多糖水提工艺研究

利用正交试验法对海湾扇贝多糖水提工艺进行优化,以多糖提取率为指标,研究了温度、料液比、时间对提取效果的影响。结果表明:最佳水提工艺为:提取时间为6 h,温度为90℃,料液比为1∶40,多糖提取率为5.419%,为海湾扇贝产品开发提供依据。