黑斑原鮡对急性高温耐受性的研究
Effects of high temperature stress on the lethality of fry and adult Glyptosternon maculatum
收稿日期: 2023-10-11
基金资助: |
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Received: 2023-10-11
作者简介 About authors
曾荣俊(1982—),男,高级工程师,学士,研究方向:水电厂生态环境保护。E-mail:13928167@qq.com
为探究黑斑原鮡(Glyptosternon maculatum)鱼苗与成鱼对急性高温胁迫的耐受情况,本研究测定了鱼苗与成鱼在不同急性高温胁迫下的半致死时间,以及成鱼的呼吸频率。结果表明:黑斑原鮡鱼苗的半致死时间(LT50)随水温的升高而缩短,不同水温组的半数死亡时间存在显著差异(P<0.05),其中28 ℃组在13.53 h可达到半数死亡,24 ℃则为71.20 h;在高温胁迫下,成鱼的呼吸频率显著升高,24 ℃组的半致死时间(LT50)为15.60 h,远短于鱼苗在该水温下的半致死时间。急性高温胁迫下黑斑原鮡鱼苗的耐受能力强于成鱼,但两者均容易在短期内发生大量死亡,因此在养殖过程中应时刻关注水温的变化。
关键词:
In order to explore the tolerance of Glyptosternon maculatum to extreme temperatures at different stages, this study performed acute hyperthermic stress on the fry and adult fish, determined semi-lethal time at each temperature, and measured the respiratory rate of adult fish under hyperthermia. The results showed that the semi-lethal time (LT50) of fry G.maculatum shortened with the increase of temperature, and there was a significant difference in the LT50 of the different temperature groups (P<0.05), among which LT50 was 13.53 h at 28 ℃ and 71.20 h at 24 ℃. The respiratory rate of adult fish under high temperature stress increased significantly, and the semi-lethal time (LT50) of adult fish at 24 ℃ was 15.6 h, which was much lower than that of fry at this temperature. The results showed that there were differences in heat tolerance at different growth stages, and attention should be paid to water temperature control during the breeding process. The short-term lethal temperature of fry was 28 ℃, and the short-term lethal temperature of adult fish was 24 ℃. The results of this study can provide basic data for healthy breeding and further study of high temperature tolerance mechanism of G.maculatum.
Keywords:
本文引用格式
曾荣俊, 刘晓锐, 耿庆宝, 唐雪梅, 方媛林, 吴雷, 张欢, 顾正选, 禹猛.
ZENG Rongjun, LIU Xiaorui, GENG Qingbao, TANG Xuemei, FANG Yuanlin, WU Lei, ZHANG Huan, GU Zhengxuan, YU Meng.
黑斑原鮡(Glyptosternon maculatum),隶属于鲇形目(Siluriformes)、 鮡科(Sisoridae)、原鮡属(Glyptosternum),是中国唯一的原鮡属鱼类,仅分布在中国境内的雅鲁藏布江水系,栖息地海拔约2 800~4 200 m,具有较高的经济价值和药用价值,同时也是研究适应高海拔鱼类的重要物种[1-2]。近年来受水利工程、过度捕捞、外来入侵物种等的影响,野生黑斑原鮡的资源量和分布范围均日趋减少,加之其生长缓慢、性成熟晚,种群资源难以恢复,现已被《中国生物多样性红色名录》列为极危(CR)物种[3]。因此,保护黑斑原鮡种质资源、推动苗种繁育技术的研究迫在眉睫。
1 材料与方法
1.1 试验材料
黑斑原鮡鱼苗和成鱼均为2019年5月13日至5月30日收集的黑斑原鮡亲鱼及在西藏拉萨雅鲁藏布江鱼类资源繁育基地所繁殖的子一代。试验开始前,先将试验鱼移至水温约12 ℃(与原饲养水温相近)的全自动控温水族箱中暂养一周,试验用水的pH为(7.2±0.5),溶解氧浓度>6 mg/L。试验开始前禁食24 h,整个试验期间不投喂饵料。
1.2 试验方法
1.2.1 预试验
选择40尾体质健壮的黑斑原鮡鱼苗,随机分成4组,温度分别设定为18、20、22、24 ℃,试验进行96 h,在试验期间不进行饵料投喂。根据96 h内出现黑斑原鮡半数死亡的最低温度,再进行后续试验。
1.2.2 鱼苗急性高温胁迫试验
根据预试验结果,发现在20 ℃及以下水温时,黑斑原鮡鱼苗未出现大量死亡,96 h内未出现半数死亡。因此,本试验设置22、24、26、28 ℃4个胁迫温度,随机选取450尾无病无伤、体质健壮的开口40 d左右的黑斑原鮡鱼苗[平均体质量为(0.042±0.009)g、平均全长为(18.09±1.23)mm],分成4个处理组,每组3个平行。试验开始时,先将黑斑原鮡鱼苗放入水族箱,再逐渐调高水温,温度上调频率为1 ℃/h,直到水族箱内的水温分别达到22、24、26、28 ℃。所选黑斑原鮡鱼苗分别放入编号为1~4号的4个室内全自动控温水族箱,每个水族箱用亚克力隔板平均分成3格,其中1号水族箱每格60尾(基于22 ℃水温预实验时,黑斑原鮡鱼苗96 h内出现半致死率的时间较长,因此在正式实验时增加其数量),2~4号水族箱每格30尾。在水族箱水温分别达到预设温度后,开始连续观察并记录死亡黑斑原鮡鱼苗的个体数量与相应的时间,统计死亡率达10%、20%、30%、40%、50%所用的时间,待LT50出现时停止记录。
1.2.3 成鱼急性高温胁迫试验
为比较黑斑原鮡鱼苗与成鱼耐受性的差异,根据鱼苗的试验结果,选择在96 h内出现LT50的最低水温进行成鱼急性高温胁迫试验。随机选取黑斑原鮡成鱼60尾作为试验对象,分为对照组和试验组,每组30尾,每组设置3个平行。黑斑原鮡成鱼放入用亚克力隔板平均分成3格的室内全自动控温水族箱中,每格10尾。对照组水温保持在12 ℃;试验组的黑斑原鮡成鱼放入水族箱后,按1 ℃/h将水温调至24 ℃。连续观察并测定水体溶解氧、试验鱼每min的平均呼吸频率,由于黑斑原鮡成鱼数量较少,因此试验中连续记录试验组黑斑原鮡的死亡情况,并计算其死亡率,待到达半致死时间时,停止记录。
1.3 数据统计与分析
采用Excel和SPSS 26.0对所得数据进行统计与分析,数据以平均值±标准差(
2 结果
2.1 急性高温胁迫对黑斑原鮡鱼苗的影响
试验结果(表1)表明,在22~28 ℃水温范围内,黑斑原鮡鱼苗死亡速度随水温的升高而明显加快。当水温达24 ℃及以上温度时,黑斑原鮡鱼苗在96 h内均出现了半致死率(此时即为LT50),在水温24 ℃时的LT50为71.20 h,26 ℃为52.86 h,而当水温达到28 ℃时,黑斑原鮡鱼苗死亡速度快速增加,在13.53 h内即达到了50%的死亡率。这说明水温越高,半致死时间越短,对黑斑原鮡鱼体的伤害越大。
表1 急性高温胁迫下黑斑原鮡鱼苗达到相应死亡率所用的时间
Tab.1
温度/℃ Temperature | 致死时间/min Lethal time | ||||
---|---|---|---|---|---|
10% | 20% | 30% | 40% | 50%(LT50) | |
22 | 32.60±4.40a | 46.53±3.06a | 59.93±1.91a | 66.80±0.00a | — |
24 | 33.53±7.22a | 45.67±4.04a | 49.40±1.98b | 64.90±4.80a | 71.20±0.00a |
26 | 24.67±7.03a | 32.77±1.27b | 39.17±5.48c | 45.33±6.75b | 52.86±4.21b |
28 | 8.50±0.87b | 9.93±1.01c | 11.33±1.72d | 13.20±0.00c | 13.53±0.28c |
注:不同小写字母表示不同温度组到达同一死亡率时的时间存在显著差异(P<0.05),相同则无差异(P>0.05)。
Notes: Different lowercase letters indicated significant differences in the time to reach the same mortality rate in different temperature groups (P<0.05), or the same indicated no difference (P>0.05).
2.2 急性高温胁迫对黑斑原鮡成鱼的影响
急性高温胁迫对水体溶解氧与黑斑原鮡成鱼呼吸频率的影响结果如表2所示。在急性高温胁迫中,试验组水体的溶解氧浓度显著低于对照组(P<0.05),黑斑原鮡成鱼呼吸频率显著高于对照组(P<0.05)。
表2 急性高温胁迫对水体溶解氧与黑斑原鮡成鱼呼吸频率的影响
Tab.2
组别 Groups | 温度/℃ Temperature | 溶解氧/(mg/L) Dissolved oxygen | 呼吸频率/(次/min) Respiratory frequency |
---|---|---|---|
对照组Control group | 12 | 6.52±0.17 | 89.00±4.58 |
试验组Experiment group | 24 | 4.68±0.16* | 205.33±6.43* |
注:*表示试验组与对照组间存在显著差异(P<0.05)。
Note:* indicated that there was a significant difference between the experiment group and the control group (P<0.05).
试验结果(表3)表明,在24 ℃水温条件下,黑斑原鮡成鱼在试验开始后的4.10 h即出现死亡,死亡率为16.67%,在15.60 h死亡率达到50.00%,LT50明显短于同样温度条件下的鱼苗。这说明急性高温胁迫下黑斑原鮡成鱼的耐受能力较鱼苗弱。
表3 急性高温胁迫下黑斑原鮡的死亡情况
Tab.3
时间/h Time | 累计死亡数/ind Cumulative number of deaths | 累计死亡率/% Cumulative death rate |
---|---|---|
4.10 | 5 | 16.67 |
4.60 | 6 | 20.00 |
6.60 | 8 | 26.67 |
9.40 | 9 | 30.00 |
9.60 | 10 | 33.33 |
11.10 | 11 | 36.67 |
12.00 | 13 | 43.33 |
14.40 | 14 | 46.67 |
15.60 | 15 | 50.00 |
注:开始时间记为0 h。
Note:The start time was denoted as 0 h.
3 讨论
鱼类属于变温动物,生理活动易受到外界温度的影响,随着温度的变化,鱼体的能量代谢、生长均随着酶活性的变化而受到影响[12]。已有的研究表明,当水温超过鱼体的最适温度范围时,鱼类的摄食量、代谢酶活力等会相应降低,直至鱼类死亡[6,13]。本试验结果表明,当水温达24 ℃及以上时,黑斑原鮡鱼苗和成鱼在96 h内均出现了半致死时间(LT50),水温越高,半致死时间越短,组间差异显著(P<0.05)。另有研究表明,LT50与半致死浓度(LC50)具有较强的相关性,二者均可衡量毒物毒性[14]。由此可以看出,温度越高对鱼体的伤害越大。这可能是因为随着温度的升高,细胞代谢增加,导致活性氧(ROS)增加,而黑斑原鮡又长期生活在寒冷的环境中,对于氧化应激可能具有先天的生理敏感性[15]。
在本研究中,高温状态下水体溶解氧浓度降低,黑斑原鮡成鱼的呼吸频率加快。在气候变化的情况下,随着温度的升高,水体溶解氧饱和度会相应降低[16],这与本研究结果一致。鱼类大规模死亡事件的发生,常与水体溶解氧浓度的降低有关[17]。在对5种海水养殖鱼类幼鱼[豹纹鳃棘鲈(Plectropomus leopardus)、驼背鲈(Cromileptes altivelis)、棕点石斑鱼(Epinephelus fuscoguttatus)、赤点石斑鱼(Epinephelus akaara)和珍珠龙胆石斑鱼(Epinephelus fuscoguttatus♀×E.lanceolatus♂)]及淡水鱼类[鲤鱼(Cyprinus carpio)][18-19]进行研究时,发现鱼类的呼吸频率与温度呈正相关,水体温度越高,呼吸频率越快,窒息越快,这与本研究的结果一致。在变温生物中,温度变化的补偿是通过生理过程实现的,例如通过调节呼吸频率和代谢率来适应温度变化[19]。因此在高温环境中鱼类的呼吸频率加快,可能与鱼体红细胞数量的减少[13]、水体的溶解氧浓度的降低和鱼体的需氧量增加有关。这也就可以解释黑斑原鮡鱼苗的LT50随温度升高而显著缩短的原因。
本研究中,在24 ℃高温胁迫下,黑斑原鮡成鱼的LT50为15.60 h,远短于鱼苗的71.20 h,这说明急性高温胁迫下黑斑原鮡鱼苗的耐受能力较成鱼强。在对不同生长阶段的鱼类的低氧耐受性研究中也发现,幼鱼观测到的最低效应浓度低于成鱼,幼鱼更耐低氧[20]。而且对拉萨裂腹鱼(Schizothorax waltoni)[21]温度耐受性的研究还发现,小规格拉萨裂腹鱼的极限高温高于中规格和大规格,这与本研究的结果较为一致。但鱼类在成年后的体长与热耐受性间不存在显著的相关性[22],此外澳洲鳗鲡(Anguilla australis)对水温的耐受性随体质量的增加而增加[23]。综上可知,不同鱼类在不同生长阶段的耐受性可能会因物种而不同,没有统一的界限。在查阅文献的过程中,发现有关鱼类不同生长阶段的耐受性的差异及其内在机理变化的研究文献较少,但对于健康养殖来说,了解鱼类不同生长阶段的生理机能、对某一环境因子的耐受情况十分重要。
4 结论
本研究进行了黑斑原鮡鱼苗和成鱼的急性高温胁迫试验,结果显示:在试验水温内,黑斑原鮡鱼苗的LT50随水温的升高而缩短,成鱼在高温胁迫下的呼吸频率会显著升高,远低于在相同水温下鱼苗的LT50,说明黑斑原鮡鱼苗的高温耐受能力高于成鱼。在高温胁迫下,黑斑原鮡鱼苗和成鱼在短期内容易发生大量死亡,因此在养殖过程中应时刻关注水温的变化。但本研究仅测定了高温胁迫下黑斑原鮡鱼苗与成鱼的LT50,而未对其代谢机理、高温胁迫响应机制进行研究,因此后续可针对该方面进行更深入的研究。
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Low oxygen tolerance of different life stages of temperate freshwater fish species
[J].Data on low dissolved oxygen (DO₂) tolerance of freshwater fish species of north-western Europe were used to create species sensitivity distributions (SSD). Lowest observed effect concentrations (LOEC) and 100% lethal concentrations (LC₁₀₀) data were collected from the scientific literature. Comparisons were made among life stages as well as between native and exotic species. In addition, lethal DO₂ concentrations were compared to oxygen concentrations corresponding to maximum tolerable water temperatures of the same species. Fish eggs and embryos were the least tolerant. Juveniles had a significantly lower mean LOEC than adults, but there was no difference in mean LC₁₀₀ between the two groups. The difference in lethal oxygen concentrations between adults and juveniles was largest for three salmonids, although it remains uncertain if this was a result of smoltification. There were no significant differences between native and exotic species; however, data on exotics are limited. DO₂ concentrations converted from maximum tolerable water temperatures were 3·9 times higher than the measured lethal DO₂ concentrations, which may reflect changes in respiration rates (Q₁₀) and may also relate to the simplicity of the model used.© 2013 The Authors. Journal of Fish Biology © 2013 The Fisheries Society of the British Isles.
Relationship between fish size and upper thermal tolerance
[J].Using critical thermal maximum (CTMax) tests, we examined the relationship between upper temperature tolerances and fish size (fry–adult or subadult lengths) of rainbow trout Oncorhynchus mykiss (41–200‐mm TL), Apache trout O. gilae apache (40–220‐mm TL), largemouth bass Micropterus salmoides (72–266‐mm TL), Nile tilapia Oreochromis niloticus (35–206‐mm TL), channel catfish Ictalurus punctatus (62–264 mm‐TL), and Rio Grande cutthroat trout O. clarkii virginalis (36–181‐mm TL). Rainbow trout and Apache trout were acclimated at 18°C, Rio Grande cutthroat trout were acclimated at 14°C, and Nile tilapia, largemouth bass, and channel catfish were acclimated at 25°C, all for 14 d. Critical thermal maximum temperatures were estimated and data were analyzed using simple linear regression. There was no significant relationship (P > 0.05) between thermal tolerance and length for Nile tilapia (P = 0.33), channel catfish (P = 0.55), rainbow trout (P = 0.76), or largemouth bass (P = 0.93) for the length ranges we tested. There was a significant negative relationship between thermal tolerance and length for Rio Grande cutthroat trout (R2 = 0.412, P < 0.001) and Apache trout (R2 = 0.1374, P = 0.028); however, the difference was less than 1°C across all lengths of Apache trout tested and about 1.3°C across all lengths of Rio Grande cutthroat trout tested. Because there was either no or at most a slight relationship between upper thermal tolerance and size, management and research decisions based on upper thermal tolerance should be similar for the range of sizes within each species we tested. However, the different sizes we tested only encompassed life stages ranging from fry to adult/subadult, so thermal tolerance of eggs, alevins, and larger adults should also be considered before making management decisions affecting an entire species.
澳洲鳗鲡(Anguilla australis)不同生长阶段的生物学耐受性特征及其演变趋势
[J].
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