环境因子对两种海洋双壳类幼体趋性行为中的调节作用

本文研究了温度、盐度和重金属等几种因子对缢蛏和长牡蛎幼体趋地性和趋光性行为的影响。结果表明:1)降低温度能增强缢蛏幼体的正趋地性,而长牡蛎幼体却由正趋地性转变为负趋地性,同时两种幼体的正趋光性受到抑制作用;升高温度对缢蛏幼体趋光性的影响不明显,但能加强牡蛎幼体的正趋光性。2)盐度提高时缢蛏幼体的正趋光性趋于增强,正趋地性趋于减弱。3)重金属Cu和Zn在各自的亚致死浓度下具有提高缢蛏幼体正趋地性和降低正趋光性的作用,而牡蛎幼体的正趋地性却趋于减弱,正趋光性趋于增强。本文据上述幼体的行为变化,还讨论了这几种因子对幼体垂直分布的调节作用。     

香港巨牡蛎和长牡蛎幼虫及稚贝的表型性状

为了评估香港巨牡蛎和长牡蛎在北方沿海的早期表型性状,于2010年7月,以2009年6月在青岛繁育的两种牡蛎为材料,在大连研究了温度(Mt:(22±1.0)℃及Ht:(28±1.0)℃)、盐度(S₂₀:20±1.0及S₃₀:30±1.0)及中间育成环境(ID:室内及OD:室外)对两种牡蛎幼虫及稚贝表型性状的影响。结果表明:香港巨牡蛎壳宽显著大于长牡蛎(P<0.05),壳高及怀卵量显著小于长牡蛎(P<0.05),壳长、鲜重及壳重两者间无显著差异(P>0.05)。在温度和盐度相同情况下,长牡蛎卵径、受精率、孵化率及D形幼虫均大于香港巨牡蛎;香港巨牡蛎幼虫浮游前期生长较慢,而后快于长牡蛎。两种牡蛎幼虫存活能力在15日龄时高温组>中温组;相同温度下,香港巨牡蛎中盐组>高盐组,长牡蛎高盐组>中盐组。幼虫变态期间,较低的温度延迟了变态时间,降低了变态率,使得两种幼虫变态规格大型化。温度是影响幼虫生长、存活、变态的最主要因素,其次为盐度,交互作用几乎尚未起到作用。中间育成阶段,室外比室内培育效果更好,且香港巨牡蛎稚贝壳高在60日龄以后显著大于长牡蛎(P<0.05),环境是影响稚贝生长的最主要因素;无论室内还是室外两种牡蛎稚贝的存活率均在90%以上,且各实验组间无显著差异(P>0.05)。     

Ingestion and digestion of seven species of microalgae by larvae of Strombus gigas (Mesogastropoda: Strombidae)

The potential nutritional value of seven microalgal diets as measured by their ingestibility and digestibility to queen conch Strombus gigas larvae was tested with 30 day old larvae reared at 28 degrees C and fed at 1000 cells x ml(-1). The algae were Tetraselmis suecica, Tetraselmis chuii Isochrysis aff. galbana, Dunaliella tertiolecta, Chlamydomonas coccoides, Chaetoceros sp. and Thalassiosira fluviatilis. Ingestion and digestion were measured by the four nutritional stages studied with epifluorescence microscopy with live larvae. Temporal and absolute indices showed that larvae fed Chaetoceros sp. and T. fluviatilis had lower ingestion and digestion levels. The other algae are recommend to feed S. gigas larvae.     

Effects of water temperature and thermoclines on larval behaviour and development in the giant crab Pseudocarcinus gigas (Lamarck)

Pseudocarcinus gigas is a deep-water commercial species. Todate, only three larvae have been collected, despite extensivesampling. Therefore, to assist the targeting of field samplingof larvae, laboratory-based research was undertaken to identifytemperature preferences. Two approaches were taken. The firstinvestigated the behavioural responses of P. gigas larvae totemperature. Experimental columns with discontinuous temperaturegradients were used to test the ability of P. gigas larvae topenetrate thermoclines vertically. Each trial also presentedthe larvae with a choice of two temperature options so resultswere used to infer preferred temperature ranges. In the secondapproach, we measured instar duration, somatic growth and survivalof larvae reared at 12 temperatures between 10.5 and 21.1°C.Behavioural experiments indicated that zoeas I and II couldreadily penetrate experimental thermoclines of 2, 5 and 10°C.Upward swimming was induced in water temperatures 12.7°Cand downward swimming or passive sinking induced by temperatures=" BORDER="0">16.2°C. Intermoult duration decreased withincreasing temperature, although more rapid development wasat the expense of somatic growth. Apparent temperature preferencesof larvae from behavioural trials were also optimal for survivaland growth. No larvae survived to megalopa in those treatmentsbelow the threshold temperature where upward swimming was inducedin behaviour trials. Many megalopas died shortly after moultingfrom zoea V, particularly in treatments with rapid development(>16.8°C) and above those temperatures where downwardmigration of zoeas was induced. Highest abundance of P. gigaslarvae in the field is predicted to be in water of 13–16°C.     

Evaluation of biomarkers in oyster larvae in natural and polluted conditions

Crassostrea gigas D-shaped larvae were subjected to different conditions of temperature and salinity for 24 h and four biomarkers (acetylcholinesterase (AChE) activity, thiobarbituric acid reactive substances (TBARS) levels, glutathione S-transferase (GST) and catalase (CAT) activities) were measured. AChE activity decreased when salinity increased from 25 to 30 and 35 psu at 20 and 25 degrees C. Temperature did not seem to have an influence on AChE activity. TBARS levels increased as a function of salinity when the temperature was maintained at 20 degrees C, whereas at 25 degrees C no effect of salinity could be observed. Variations in GST and CAT activities were not significant with salinity and temperature except that catalase activity was higher at 25 degrees C than at 20 degrees C. Exposure experiments were conducted at 23 degrees C and 30 psu with carbofuran (100 and 1000 microg/l) and malathion (100 and 300 microg/l). There was an inhibition of AChE activity with carbofuran, and a toxic effect shown by an increase in TBARS levels counteracted by increases in GST and CAT activities which protected the larvae. When two pairs of adults producing larvae were taken into consideration, significant differences in biomarker levels were noted between the larval offspring of each pair. Malathion induced a decrease in AChE activity and an increase in CAT activity.     

Behavioural response of larval Atlantic menhaden to different rates of temperature change

Larval Atlantic menhaden Brevoortia tyrannus, spawned off North Carolina (U.S.A.) during the winter, undergo cross-shelf transport from the western Gulf Stream edge to coastal bays and estuaries. Variation in water flow direction with depth provides larvae the opportunity to enhance shoreward transport, if they can regulate their depth behaviourally. Temperature, which normally decreases with depth on the continental shelf, is one possible cue for depth regulation. Laboratory-reared larval menhaden of two different ages were exposed to varying relative rates of temperature increases and decreases, which were presented from both above and below the larvae. Temperature decreases from below caused an ascent response in both young and old larvae, but neither responded to this cue from above. The minimum (threshold) relative rates of decrease for initiating ascents were similar (7.9 × 10^?2, 10.7 × 10^?2° C min^?1) for both age larvae as were the minimum absolute amounts of decrease that must occur before a response (0.1, 0.05°C). Young larvae did not respond to a temperature increase, while old larvae ascended regardless of whether the increase was presented from above or below. Threshold relative rates of increase were 8.59 × 10^?2°C min^?1 from below and 14.79 × 10^?2° C min^?1 from above. The threshold rates and range of larval speeds during vertical movements were used to calculate vertical temperature gradients that could be perceived. These values were compared to measured gradients in areas inhabited by menhaden larvae. On the continental shelf, detectable temperature gradients appear common for temperature decreases that would occur upon descending and temperature increases upon ascending. However, it is uncommon for larvae to encounter temperature increases upon descending that would initiate an ascent response. These results support the hypothesis that menhaden larvae are capable of using temperature gradients for depth regulation.     

在沉积物暴露条件下2种海洋贝类对Cu、Pb 的富集动力学研究

首次通过构建海水-底泥-生物体体系,应用半静态双箱动力学模型室内模拟了沉积物暴露条件下文蛤(Meretrix meretrix)和缢蛏(Sinonovacula constricta)对Cu、Pb的生物富集实验,通过对富集与排出过程中文蛤体内重金属污染物的动态监测和对富集与排出过程监测结果的非线性拟合,得到了文蛤和缢蛏富集重金属的吸收速率常数K1、排出速率常数K2、生物富集因子BCF、富集平衡浓度CAmax、生物学半衰期B1/2等动力学参数。拟合结果得到的Cu、Pb各动力学参数分别为:文蛤K1为4.63—69.41,K2为0.05—0.08,CAmax为9.83—40.57,BCF为60.77—1444.56,B1/2为9.09—14.43;缢蛏K1为4.27—122.92。K2为0.05—0.07。CAmax为5.12—32.84。BCF为65.68—2112.02。B1/2为9.81—14.15。对模型的拟合优度检验结果显示,在沉积物暴露条件下文蛤和缢蛏对重金属Cu、Pb的生物富集数据符合双箱模型,模型的拟合优度良好。比较结果得出:吸收速率常数K1及生物富集因子BCF均随着外部水体金属暴露浓度的增大而减小;CAmax均随着外部水体金属暴露浓度的增大而增大;文蛤和缢蛏对Cu富集能力大于Pb;Cu在文蛤和缢蛏体内的生物学半衰期B1/2大于Pb;理论平衡状态下文蛤和缢蛏体内Cu、Pb的含量CAmax随着外部水体中金属暴露浓度的增大而增大,且呈显著正相关,实验结果表明在沉积物暴露条件下双箱动力学模型在一定条件下是可以应用于文蛤和缢蛏的富集动力学研究的,但仍需要进一步开展在不同条件下实验研究分析。     

Abiotic factors influencing embryonic development, egg hatching, and larval orientation in the reindeer warble fly, Hypoderma tarandi

Wild-caught, tethered females of the reindeer warble fly, Hypoderma tarandi (L.) (= Oedemagena tarandi (L.)), (Diptera, Oestridae) were stimulated to oviposit on hairs of a reindeer hide. Newly laid eggs incubated at constant temperatures and relative humidities hatched within 3 days to 2 weeks, depending on the experimental conditions. Over a range of 7-40 degrees C, hatching only occurred between 20 and 37 degrees C. Eggs held at 100% relative humidity had lower hatchability and longer time to hatch relative to eggs held at 77% relative humidity. The average number of degree-days for hatching was 50.35. Between 20 and 33 degrees C there was a temperature-dependent linear trend in developmental rate, and the proportion of eggs hatching was highest, and least variable, at the mid-temperature ranges. The temperature range found in the natural host micro-habitat where H. tarandi commonly affix their eggs (close to the skin at the base of a host hair) was consistent with the experimental temperature treatments that produced the highest hatching rate. Newly emerged larvae displayed positive thermotaxis, while showing no phototaxic or geotaxic behaviour. Results indicate that constraints of the host environment, coupled with temperature-dependent hatching success, may impose a selective pressure on oviposition behaviour.     

Toxicity to bivalve hemocytes of pathogenic vibrio cytoplasmic extract

Using a chemiluminescence (CL) test, it had been previously demonstrated that Vibrio pectenicida, which is pathogenic to Pecten maximus larvae, was able to inhibit completely the CL activity of P. maximus hemocytes and partially inhibit those of Crassostrea gigas. Conversely, a Vibrio sp. strain, S322, pathogenic to C. gigas larvae was more active in reducing the CL activity of oyster hemocytes than of scallop hemocytes. Using this same CL biotest, V. pectenicida and S322 cytoplasmic extracts were shown to reproduce CL inhibition while the cytoplasmic extract of a nonpathogenic strain (U1, Pseudoalteromonas) was without effect. Moreover, cytoplasmic extract as well as live V. pectenicida cells provoked, within a few hours, death of P. maximus hemocytes adhering to a glass slide. After partial purification, it was shown that toxic activities of V. pectenicida cytoplasmic extract was due to a toxin, named VHKT (for vibrio hemocyte-killer toxin), which is heat stable, acid and protease resistant, and less than 3 kDa in molecular weight. Attempts to purify VHKT by reverse-phase (C18) HPLC separated activity into the fraction eluted by water at a retention time of 4.02 min.