氨氮胁迫对中国明对虾血淋巴氨氮、尿素氮含量和抗氧化能力的影响

将600尾体重为(5.0±1.2)g的健康中国明对虾(Fenneropenaeus chinensis)随机分为5组,每组6个重复,每个重复20尾虾,分别暴露于不同氨氮质量浓度(0 mg/L、2 mg/L、4 mg/L、6 mg/L和8 mg/L)海水中,于胁迫后6 h、24 h、48 h、72 h和96 h测定血淋巴氨氮、尿素氮含量、总抗氧化能力(T-AOC)、抗超氧阴离子活力和血淋巴细胞过氧化氢酶(CAT)基因、过氧化物还原酶(Prx)基因和含半胱氨酸的天冬氨酸蛋白水解酶(caspase)基因的相对表达量,以0 mg/L氨氮组作为对照。结果显示,随着氨氮胁迫时间的延长,中国明对虾血淋巴氨氮含量逐渐积累,以8 mg/L组对虾血淋巴氨氮含量最高,是对照组的5.85倍。氨氮胁迫6 h,胁迫组中国明对虾血淋巴尿素氮含量显著高于对照组(P0.05),其中6 mg/L组对虾血淋巴尿素氮含量最高,是对照组的2.22倍。氨氮胁迫下中国明对虾血淋巴T-AOC、Prx mRNA相对表达量随着取样时间推移先升高后降低,而血淋巴抗超氧阴离子活力、CAT和caspase mRNA相对表达量随时间增加呈现先上升后下降再上升的变化过程。氨氮胁迫下中国明对虾血淋巴抗氧化能力被显著诱导,这可能破坏机体的氧化-抗氧化系统的平衡,从而导致caspase mRNA相对表达量的上调。     

pH、氨氮胁迫对中国对虾HSP90基因表达的影响

研究了pH、氨氮胁迫对中国对虾Fenneropenaeus chinensis血细胞、肝胰腺、鳃和肌肉组织HSP90基因时空表达的影响.分别将中国对虾暴露于pH7.0、9.0的水体中148h和不同氨氮浓度的水体中96h,结果表明,pH（7.0,9.0）胁迫条件下中国对虾鳃、肌肉和血细胞HSP90基因表达均上调,肝胰腺HSP90基因表达对两种pH胁迫差异明显：pH7.0胁迫条件下,HSP90基因表达3h达峰值后明显降低;pH 9.0胁迫时,HSP90基因表达水平逐渐升高,整个胁迫过程中均显著高于对照组（P＜0.05）,说明中国对虾肝胰腺组织是高pH胁迫的响应器官.6mg/L氨氮浓度组鳃和肌肉组织HSP90基因表达水平24h达最高值,分别为对照组的5.46和1.55倍;各胁迫组肝胰腺和血细胞HSP90基因表达水平分别于6h和48h达到最高值,为对照组的1.33～2.08倍和2.20～5.45倍.肝胰腺组织对氨氮胁迫表现敏感,短时间内（6h）通过上调HSP90基因表达水平保护细胞;鳃组织HSP90基因表达波动范围最大,说明鳃组织需要更高表达量的HSP90保护细胞.当氨氮浓度持续48～96h维持在2～6mg/L,各组织HSP90基因表达水平显著降低.     

急性氨氮胁迫对黄颡鱼组织抗氧化酶活性及HSP70和HSP90基因mRNA表达水平的影响

为了探讨急性氨氮胁迫对黄颡鱼组织中抗氧化酶活性及HSP70和HSP90基因mRNA表达水平的影响,实验随机挑选了360尾黄颡鱼[初体质量(17.25±0.05)g],分别暴露于含有0(对照)、5.70(低浓度组)、28.50(中浓度组)和57.00(高浓度组)mg/L总氨氮浓度的水体中,进行96 h的急性胁迫实验。实验开始后,分别于0、12、24、48和96 h取样。结果显示,氨氮胁迫发生后,低、中浓度组实验鱼肝脏中超氧化物歧化酶(SOD)活性呈先升高后降低趋势,而高浓度组则持续降低;低、中、高浓度组实验鱼肝脏中丙二醛(MDA)含量在胁迫开始后显著升高;3 h时,高浓度组实验鱼肝脏中SOD活性达到最低,而MDA含量最高;24 h后,高浓度组实验鱼肝脏中过氧化氢酶(CAT)活性显著升高;低、中、高浓度组实验鱼肝脏中HSP70基因的mRNA表达量呈先降低后升高趋势,而鳃中HSP70基因表达量持续升高,但脑中HSP70基因在0 h后显著降低;氨氮胁迫3 h时,低、中、高浓度组实验鱼肝脏和脑中HSP70基因表达量显著低于对照组,而在鳃中正好相反;相比HSP70基因,高氨氮浓度组实验鱼肝脏和鳃中HSP90基因的mRNA表达量在24 h时达到最高。研究表明,不同浓度的氨氮胁迫会对黄颡鱼抗氧化酶活性造成不同程度的抑制,原因与丙二醛的积累量有关;相比HSP90基因,黄颡鱼HSP70基因的表达量在氨氮胁迫发生后迅速上调,这种生理调控机制提示HSP70在应对急性氨氮胁迫时发挥着更重要的作用。     

急性氨氮毒性对黄颡鱼头肾巨噬细胞抗氧化及炎症相关基因表达的影响

为了研究急性氨氮胁迫对黄颡鱼头肾巨噬细胞抗氧化及炎症相关基因表达的影响,实验通过建立黄颡鱼离体头肾细胞模型,开展为期96 h的急性氨氮胁迫实验。结果显示,0.14和0.28 mg/L总氨氮处理组SOD基因的相对表达量显著低于对照组,但0.28 mg/L总氨氮处理组GPX基因的相对表达量显著高于其他组;0.14和0.28 mg/L总氨氮处理组IL-1和TNF基因的相对表达量显著低于对照组,而0.28 mg/L总氨氮处理组IL-8基因的相对表达量显著低于0.14 mg/L总氨氮处理组和对照组;吖啶橙染色检测发现,0.14 mg/L总氨氮处理组实验鱼头肾巨噬细胞内可见边缘不规则的黄绿色荧光,0.28 mg/L总氨氮处理组实验鱼头肾巨噬细胞内可见致密浓染的黄绿色荧光信号。研究表明,氨氮毒性能够影响黄颡鱼头肾巨噬细胞抗氧化相关基因的表达;细胞凋亡可能是造成鱼类氨中毒致死的主要原因之一。     

高碱环境下青海湖裸鲤氮废物排泄及相关基因的表达规律

采用个体生理学及定量PCR方法,研究了青海湖裸鲤(Gymnocypris przewalskii)在32 mmol/L(CA32)和64 mmol/L(CA64)碳酸盐碱度胁迫下氮废物排泄规律及鳃和肾组织中Rhesus type b glycoproteins(Rhbg)、Rhesus type c2 glycoproteins(Rhcg2)与urea transporter(Ut)基因的表达规律。结果显示,在32 mmol/L碱度胁迫整个过程中及64 mmol/L碱度胁迫初期裸鲤氨氮排泄率显著降低,但在64 mmol/L碱度胁迫8~20 h、24~72 h时氨氮排泄率基本恢复到胁迫前水平,在32 mmol/L碱度胁迫12~16 h、20~24 h及64 mmol/L碱度胁迫16~48 h时尿素氮排泄率显著升高。定量PCR结果显示,Rhbg、Rhcg2、Ut基因在胁迫过程中都有表达上调趋势,其中32 mmol/L碱性环境下鳃组织中Rhbg基因在胁迫12 h时表达明显上调;64 mmol/L碱性环境下鳃组织中Rhcg2基因在胁迫6 h、48 h、72 h表达明显上调,Ut基因在胁迫6 h表达明显上调,肾组织中Rhcg2基因在胁迫6 h表达明显上调。以上结果表明,裸鲤在高碱环境下虽然前期氮废物排泄受到抑制,但后期会通过启动Rh基因高表达恢复氨氮排泄,同时启动Ut高表达来增加尿素氮排泄来进行氮废物排泄。这一特殊氮废物排泄策略有助于裸鲤更好地适应高碱性环境。     

氨氮胁迫对三疣梭子蟹酚氧化酶原系统和免疫指标的影响

以三疣梭子蟹(Portunus trituberculatus)为研究对象,研究氨氮胁迫对其酚氧化酶原系统和免疫指标的影响.实验分0mg/L、1 mg,L、5mg,L、20mg,L氨氮处理组,分别于0h、6h、12 h、24 h、48 h取样并进行相关指标测定.结果表明:氨氮胁迫对三疣梭子蟹血淋巴多巴胺含量、血细胞数量、血细胞酚氧化酶原(proPO)活力和mRNA表达以及抗菌、溶菌活力的影响显著(P<0.05).各处理组血淋巴多巴胺含量于6 h达到最大值,12 h后恢复至对照组水平;各处理组血细胞数量均呈明显下降趋势,除20mg/L氨氮处理组半颗粒细胞、总细胞数量表现为逐渐下降趋势外,其他处理组3类血细胞和总细胞数量分别于12h或24h时降至最低值,然后保持稳定.各处理组上述指标分别呈明显下降、升高、下降和峰值变化趋势,其中1mg/L处理组血细胞proPO活力在12 h后恢复至对照组水平,而mRNA表达与对照组差异不显著,其他处理组血细胞proPO活力和mRNA表达分别于12h、6h后保持稳定;各处理组抗菌活力于6h或12h达到最小值,然后恢复至对照组水平,而溶菌活力在24 h后趋于稳定,且1 mg/L处理组与对照组无明显差异.各处理组血细胞数量、proPO活力、溶菌活力在稳定后均与氨氮浓度呈明显的负相关性,而血细胞proPO mRNA表达呈显著正相关性.由此可见,三疣梭子蟹在氨氮胁迫下血细胞数量、proPO活力和mRNA表达以及免疫指标表现出明显的时间剂量效应性,具有显著的免疫毒性效应.本研究旨在为三疣梭子蟹养殖水环境调控和病害防治提供基础依据.     

氨氮对红星梭子蟹早期幼体的急性毒性

在盐度30、pH 8.5、温度28.8～29.8℃、投喂扁藻和轮虫的条件下,设置10、20、40、80、160mg/L共5个氨氮梯度和1个对照组(天然海水),进行了氨氮对红星梭子蟹早期幼体(第Ⅰ期溞状幼体,Z1)的急性毒性试验。结果发现,氨氮暴露12～72h,红星梭子蟹早期幼体活力组间差异显著(P<0.05),当氨氮继续暴露至84～96h,早期幼体活力组间差异不显著(P>0.05);氨氮暴露12～96h,红星梭子蟹早期幼体存活率组间差异显著(P<0.05),但对照组与10mg/L试验组差异不显著(P>0.05);红星梭子蟹早期幼体的氨氮暴露12、24、36h时的半致死质量浓度分别为80.94、27.96、14.43mg/L,红星梭子蟹早期幼体暴露36h的氨氮安全质量浓度为1.44mg/L。     

氨氮短期胁迫与恢复对克氏原螯虾的影响

为探究氨氮胁迫与恢复对克氏原螯虾抗氧化和免疫酶活性及组织结构的影响,将体质量(6.33±0.73)g的克氏原螯虾暴露于0、20、40、60、80 mg/L 5个氨氮质量浓度下,比较胁迫48 h时及恢复48 h后,各组肝胰腺、鳃和血清的抗氧化和免疫酶活性以及各组肝胰腺和肌肉组织结构的变化。试验结果显示：氨氮对克氏原螯虾幼虾24、48、72、96 h的半致死质量浓度分别为359.37、238.09、196.34、162.00 mg/L,安全质量浓度为16.20 mg/L。胁迫48 h后,除20 mg/L试验组外,其余试验组肝胰腺的总超氧化物歧化酶活性较对照组显著增强,80 mg/L组鳃的总抗氧化能力显著降低、过氧化氢酶活性显著增强,80 mg/L组血清的总超氧化物歧化酶活性显著增强;恢复48 h后,60 mg/L组肝胰腺和鳃的丙二醛含量较对照组显著上升,80 mg/L组鳃的过氧化氢酶活性较对照组显著增强,60 mg/L组血清的总抗氧化能力较对照组显著上升,其他试验组酶活性均恢复至对照组水平。氨氮胁迫48 h,随着氨氮质量浓度的升高,肝胰腺管腔逐渐变形、转运泡增大,鳃的呼吸上皮细胞开始脱落、...     

氨氮急性胁迫对大菱鲆幼鱼的毒性效应

本研究采用96 h半静态毒性实验方法,研究了氨氮对大菱鲆(Scophthalmus maximus)幼鱼的急性毒性效应和血浆生理指标的影响。结果显示,在水温为(19.0±0.5)℃、pH为7.85、盐度为29.5和溶解氧为(7.8±0.2) mg/L的环境条件下,平均体重为(163.90±15.31) g的大菱鲆幼鱼,总氨(TAN)和非离子氨(NH3-N)96 h的半致死浓度(LC50)分别为39.73和0.64 mg/L。氨氮浓度、暴露时间及二者交互作用对血浆肾上腺素(EPI)、皮质醇(Cortisol)、超氧化物歧化酶(SOD)、还原型谷胱甘肽(GSH)、碱性磷酸酶(AKP)和血糖(GLU)含量/活性都存在显著影响;血浆EPI、SOD、GSH、AKP和GLU随氨氮浓度升高响应时间提前,EPI、皮质醇、AKP和GLU随暴露时间延长总体呈现先升后降的趋势;致死高浓度胁迫(TAN浓度70.96和84.11 mg/L)下,血浆SOD和GSH在胁迫期(12 h)内快速升高,GLU快速升高(4 h)后急剧降低(12 h),暗示氨氮急性致死的原因与氧化应激损伤、生理代谢紊乱和呼吸功能受损有关。本结果可为大菱鲆大规格幼鱼的养殖管理和行为数值模拟提供基础资料。     

氨氮对脊尾白虾幼虾和成虾的毒性试验

在水温24℃、盐度31、pH8.1条件下,研究了氨氮对脊尾白虾幼虾和成虾的毒性。试验结果表明,氨氮对脊尾白虾幼虾24、48、72、96h的半致死质量浓度分别为155.81、116.71、92.55、80.40mg/L,氨氮对脊尾白虾成虾24、48、72、96h的半致死质量浓度分别为178.80、156.37、140.28、120.86mg/L。脊尾白虾幼虾总氨氮和非离子氨的安全质量浓度为8.04、0.26mg/L,成虾总氨氮和非离子氨的安全质量浓度为12.09、0.50mg/L。     

Acute Toxicity of Ammonia and Nitrite to Painted River Prawn,Macrobrachium carcinus,Larvae

This study evaluated the toxicity of ammonia and nitrite to different larval stages of Macrobrachium carcinus. Three replicated groups of larvae in the zoea stages II, V, and VIII (hence named Z₂, Z_5, and Z₈, respectively) were exposed separately to five ammonia (5, 10, 20, 40, and 80 mg total ammonia nitrogen [TAN]/L) and six nitrite concentrations (5, 10, 20, 40, 80, and 160 mg NO₂‐N/L), plus a control treatment with no addition of ammonia and nitrite, at a salinity of 20 g/L. The ammonia LC₅₀ values at 96 h for Z₂, Z₅, and Z₈ were 8.34, 13.84, and 15.03 mg TAN/L (0.50, 0.71, and 0.92 mg NH₃‐N/L), respectively, and the nitrite LC₅₀ values at 96 h for Z₂, Z₅, and Z₈ were 3.28, 9.73, and 34.00 mg NO₂‐N/L, respectively. The estimated LC₅₀ values for NO₂‐N were lower than those for TAN in most of the stages evaluated. This observation suggests that M. carcinus larvae are more tolerant to ammonia, except at Z₈, in which larvae had a higher tolerance to nitrite. Based on the lethal concentrations at 96 h, it may be concluded that the tolerance of M. carcinus to ammonia and nitrite increases with larval development. Safe levels were estimated to be 0.834 mg TAN/L (0.05 mg NH₃‐N/L) and 0.328 mg NO₂‐N/L; therefore, efforts should be made to maintain lower concentrations of these compounds throughout the larval rearing of M. carcinus.     

Acute and Sublethal Effects of Ammonia on Striped Bass and Hybrid Striped Bass

Bioassays in static water (mean ± SD; temperature, 20–22 C; pH, 8.2–8.4; alkalinity, 205 ± 10 mg/L CaCO₃; total hardness, 220 ± 10 mg/L CaCO₃) were used to determine median lethal concentrations (LC₅₀) of un-ionized ammonia (NH₃-N) for striped bass Moronc saxatilis and hybrid striped bass M. saxatilis × M. chrysops. The 96 h LC₅₀ for striped bass was 1.01 ± 0.24 mg/L NH₃-N₃ and was significantly higher than the LC₅₀ for hybrid striped bass (0.64 ± 0.05 mg/L NH₃-N). The effects of sublethal ammonia were evaluated after fish were exposed for 96 h to 0.0, 0.25, or 0.5 mg/L NH₃-N or to additional exposure to oxygen depleted water (about 2.0 mg O₂/L). Plasma ammonia of striped hass did not change as sublethal ammonia increased, but exposure to oxygen depletion caused a decrease in plasma ammonia. In contrast, plasma ammonia of hybrid striped bass increased as environmental ammonia increased, and increased further after exposure to oxygen depletion. Plasma cortisol levels of striped bass were significantly higher and more variable than cortisol levels of hybrid striped bass; additional exposure to oxygen depletion increased this variability, but these responses may be due to the stress of handling and confinement. Mean differences also existed between species for hemoglobin and hematocrit, while differences in variability occurred for osmolality and oxygen depletion rates. Striped bass tolerated ammonia better than hybrid striped bass but were more susceptible than hybrid striped bass to the additional stress of oxygen depletion. Most changes in physiological characteristics were relatively independent of environmental ammonia, but they were affected by oxygen depletion challenge.     

Ammonia tolerance of Litopenaeus vannamei (Boone) larvae

The tolerance of Litopenaeus vannamei larvae to increasing concentrations of total ammonia nitrogen (TAN) using a short‐term static renewal method at 26°C, 34 g L^?1 salinity and pH 8.5 was assessed. The median lethal concentration (24 h LC₅₀) for TAN in zoea (1‐2‐3), mysis (1‐2‐3) and postlarvae 1 were, respectively, 4.2‐9.9‐16.0; 19.0‐17.3‐17.5 and 13.2 mg L^?1TAN (0.6‐1.5‐2.4; 2.8‐2.5‐2.6 and 1.9 mg L^?1 NH₃‐N). The LC₅₀ values obtained in this study suggest that zoeal and post‐larval stages are more sensitive to 24 h ammonia exposure than the mysis stage of L. vannamei larvae. On the basis of the ammonia toxicity level (24 h LC₅₀) at zoea 1, we recommend that this level does not exceed 0.42 mg L^?1 TAN – equivalent to 0.06 mg L^?1 NH₃‐N – to reduce ammonia toxicity during the rearing of L. vannamei larvae.     

Acute Toxicity of Ammonia and Nitrite to Sea Bream,Sparus aurata (Linnaeus, 1758), in Relation to Salinity

Sea bream, Sparus aurata, is one of the most important fish species that is commonly cultured in the Mediterranean and the eastern coasts of the Atlantic Ocean. The life cycle of sea bream in its natural habitat passes through hyposaline and hypersaline lagoons. It is important to determine the tolerance of the fish to nitrogenous compounds for aquaculture at maximum stocking densities. In the present study, a series of acute experiments were performed to evaluate the effect of salinity on ammonia and nitrite toxicity to sea bream. The fish were exposed to different ammonia and nitrite concentrations according to the static renewal methodology at three different salinities (10, 20, and 30 ppt) and at a temperature of 20 C and a pH of 8.2. The toxic effect of total ammonia nitrogen (TAN) and nitrite nitrogen (NO₂‐N) decreased with increasing salinity levels (P < 0.001). Acute toxicity (96‐h lethal concentration 50 [LC₅₀]) values of TAN were determined to be 5.93, 11.72, and 19.38 mg/L at 10, 20, and 30 ppt salinity, respectively. The 96‐h LC₅₀ values of NO₂‐N were determined to be 370.80, 619.47, and 806.33 mg/L at 10, 20, and 30 ppt salinity, respectively. Results indicate that sea bream is less tolerant to ammonia but more tolerant to nitrite compared with some other fish species.     

Acute toxicity of ammonia in Meagre (Argyrosomus regius Asso, 1801) at different temperatures

Argyrosomus regius (3.0 ± 0.9 g) were exposed to different concentrations of ammonia in a series of acute toxicity tests by the static renewal method at three temperature levels (18, 22 and 26°C) at a pH of 8.2. Low temperature clearly increased the tolerance of the fish to total ammonia nitrogen (TAN) and unionized ammonia (NH₃) (P < 0.05). While the 96‐h LC₅₀ values of TAN were 19.79, 10.39 and 5.06 mg L^?1, the 96‐h LC₅₀ of NH₃ were 1.00, 0.70 and 0.44 mg L^?1 at 18, 22 and 26°C respectively. The safe levels of NH₃ for A. regius was estimated to be 0.10, 0.07 and 0.04 mg L^?1 at 18, 22 and 26°C respectively (P < 0.05). This study clearly indicates that A. regius is more sensitive to ammonia than other marine fish species cultured on the Mediterranean and Eastern Atlantic coasts.     

Effect of Combined Non‐ionized Ammonia and Dissolved Oxygen Levels on the Survival of Juvenile Dourado,Salminus brasiliensis (Cuvier)

The aim of this study was to assess the mean lethal concentration (LC₅₀) of dissolved oxygen in high ammonia concentration and also the LC₅₀ of ammonia under hypoxic conditions for juveniles of dourado, Salminus brasiliensis. In the first experiment, the non‐ionized ammonia (NH₃) concentrations were: 0.026, 0.447, 0.612, 0.909, and 1.334 mg/L, and the dissolved oxygen concentration was maintained at approximately 1.65 mg/L. In the second experiment, the dissolved oxygen concentrations were: 1.64, 1.99, 3.33, 5.10, and 7.77 mg/L, and the non‐ionized ammonia concentration was kept at approximately 0.927 mg/L. The mean lethal concentrations of non‐ionized ammonia varied from 0.584 to 0.577 mg/L, indicating that LC₅₀ values were almost unaffected by exposure time. The estimated LC₅₀ of dissolved oxygen varied from 4.02 to 5.02 mg/L, indicating a slight increase in the mean lethal concentrations as the exposure time increased. Results from this study indicate that interaction between these two parameters increases mortality and also suggest that dourado is susceptible to the combination of high ammonia with low dissolved oxygen concentrations.     

Ammonia‐, Sodium Chloride‐, and Calcium Sulfate‐induced Changes in the Stress Responses of Jundiá, Rhamdia quelen,Juveniles

Salt (NaCl) and gypsum (CaSO₄) are used as water additives to mitigate fish stress and improve specimen survival. High stocking densities and the transportation of fish can increase aqueous ammonia, which can, in turn, alter fish cortisol secretion. The objectives of this study were to assess the effects of salt, gypsum, and aqueous ammonia on some stress‐induced physiological responses of jundiá, Rhamdia quelen, juveniles induced by captivity and handling, and to determine the lethal ammonia concentration for this species. Jundiá juveniles were subjected to the following five treatments: water only, water + ammonia (0.4 mg/L), water + NH₃ + NaCl (6 g/L), water + NH₃ + gypsum (150 mg/L), and water + NH₃ + NaCl + gypsum. Blood samples were taken after intervals of 1, 5, 24, and 96 h, and the concentrations of cortisol, glucose, chloride, ammonia, and hematocrit were determined. The NH₃ LC₅₀ value after 96 h of exposure (LC_50?96h) was measured to be 1.9 mg/L NH₃. Either salt or gypsum reduced both cortisol and glucose levels during most of the experimental period, but the combination of both reduced these levels even further. The combined use of NaCl and CaSO₄ demonstrates a synergic effect on mitigating stress responses induced by handling and aqueous ammonia in jundiá juveniles.     

Acute and Chronic Effects of Ammonia on Juvenile Cuttlefish,Sepia pharaonis

The aim of this study was to provide a reference value for the safe regulation and control of ammonia nitrogen in the aquaculture of Sepia pharaonis. The effects of acute and chronic toxicity of ammonia on the cuttlefish, S. pharaonis, were tested experimentally using juvenile S. pharaonis. The results showed that the half‐lethal concentration (LC₅₀ ) values of ammonia nitrogen in juvenile S. pharaonis with a body weight of 6.52 ± 0. 23 g at 24, 48, 72, and 96 h were 31.72, 25.77, 23.33, and 18.33 mg/L, respectively, and the corresponding un‐ionized ammonia nitrogen (UIA‐N) concentrations were 1.66, 1.35, 1.22, and 0.96 mg/L, respectively. Compared with the control, the survival rate, specific growth rate, and feed intake of juvenile S. pharaonis declined significantly, and the feed conversion ratio and hepatosomatic index increased significantly at 56 d after exposure to >1 mg/L ammonia nitrogen. Juvenile S. pharaonis should be maintained at a concentration of ammonia nitrogen of no more than 1 mg/L (UIA‐N is 0.056 mg/L) in culture, and removing harmful nitrogenous wastes from the seawater is critical in maintaining cuttlefish culture.