The cuttlefish (Sepiella inermis) is an economically important species in the coastal seas of China. The impacts of ocean acidification on the ability of juvenile cuttlefish to select a suitable habitat, its hunting and swimming behavior, remains unknown. We examined behavior-related responses and the eye and cuttlebone structure of juvenile cuttlefish following short-term exposure to CO2-enriched seawater. The predation success rate decreased with the elevation in CO2 concentration. In the CO2 treatment groups, cuttlefish spent more time in the dark zone and the average swimming speed and total swimming distance significantly decreased. The structure of the retina and cuttlebone was affected by seawater acidification. Moreover, apoptotic cells were significantly increased in the eyes. In the wild, the impairment of the eye and cuttlebone may decrease the predation ability of juvenile cuttlefish and negatively affect their ability to select a suitable habitat, which would be detrimental to its population. © 2023

Large yellow croaker (Larimichthys crocea) is a coastal-dwelling soniferous, commercially important fish species that is sensitive to sound. An understanding of how ocean acidification might affect its auditory system is therefore important for its long-term viability and management as a fisheries resource. We tested the effects of ocean acidification with four CO2 treatments (440 ppm (control), 1000 ppm, 1800 ppm, and 3000 ppm) on the inner ear system of this species. After exposure to acidified water for 50 d, the impacts on the perimeter and mass of the sagitta, asteriscus, and lapillus otoliths were determined. In the acidified water treatments, the shape of sagittal otoliths became more irregular, and the surface became rougher. Similar sound frequency ranges triggered startle responses of fish in all treatments. In the highest CO2 treatment (3000 ppm CO2), significant asymmetry of the left and right lapillus perimeter and weight was apparent. Moreover, in the higher CO2 treatments (1800 ppm and 3000 ppm CO2), the fish were unable to maintain a balanced dorsal-up posture and tilted to one side. This result suggested that the balance functions of the inner ear might be affected by ocean acidification, which may threaten large yellow croaker individuals and populations. The molecular response to acidification was analyzed by RNA-Seq. The differentially expressed genes (DEGs) between right and left sensory epithelia of the utricle in each CO2 treatment group were identified. In higher CO2 concentration groups, nervous system function and regulation of bone mineralization pathways were enriched with DEGs. The comparative transcriptome analyses provide valuable molecular information about how the inner ear system responds to an acidified environment. © 2023 Elsevier B.V.

自工业革命以来,空气中人为排放CO_(2)量增加,引起温室效应,导致地球表面温度升高和海水升温;同时,由于海⁃气界面气体交换,大气中CO_(2)部分溶解于海洋,引起海洋酸化。海洋升温加快鱼体内生化反应和代谢速率,并通过影响生长、觅食和繁

Altered behaviors have been reported in many marine fish following exposure to high CO2 concentrations. However, the mechanistic link between elevated CO2 and activation of brain regions in fish is unknown. Herein, we examined the relative quantification and location of c-Fos expression in marine medaka following acute (360 min) and short-term (7 d) exposure to CO2-enriched water (1000 ppm and 1800 ppm CO2). In the control and two treatment groups, pH was stable at 8.21, 7.92 and 7.64, respectively. After acute exposure to seawater acidified by enrichment with CO2, there was a clear upregulation of c-Fos protein in the medaka brain (P 2 exposure for 7 d, medaka showed significant preference for dark zones during the initial 2 min period. c-Fos protein expression in the ventricular and periventricular zones of the diencephalon in medaka exposed to 1000 ppm and 1800 ppm CO2 were 0.51 ± 0.10 and 1.34 ± 0.30, respectively, which were significantly higher than controls (P© 2020 Elsevier B.V.

Fish detect water motion with their mechanosensory lateral line. The basic functional unit of the lateral line is the neuromast. In most fish species, neuromasts are located in lateral line canals (canal neuromasts) or on the skin (superficial neuromasts). In this paper, we describe the lateral line system of the pufferfish, Takifugu obscurus. If threatened, this fish inflates its body by sucking water into the esophagus. Pufferfish lack a canal system but have neuromasts located directly on the skin or in open grooves. Each groove houses tall, medium and short neuromasts, based on the height of their pedestal. One or more medium neuromasts were always located between two tall neuromasts, and the short neuromasts were scattered between them. Tall neuromasts showed phasic responses to water jets, similar to the canal neuromasts of other fish species. In contrast, the medium and short neuromasts showed tonic responses to water jets. The response properties of nerve fibers that innervated the medium and short neuromasts were similar to those of the superficial neuromasts found in other fish species. Our results suggest that each groove of a pufferfish has two functional groups of neuromasts. This may allow pufferfish to extract spatial and temporal hydrodynamic information, despite the changes in body shape that occur during and after inflation. The short neuromasts at the bottom of a groove most likely supplement the medium neuromasts when the body is maximally inflated.

海洋酸化导致海水中碳酸钙（CaCO3）的饱和度下降,对海洋钙化生物影响较大。某些鱼类,如海水青鳉鱼（Oryzias melastigma）内耳中具有钙质的耳石,可能对海洋酸化敏感。海洋酸化对幼鱼耳石发育影响已有报道,但成鱼耳石的形态和化学组成是否受到影响的研究较少。本文模拟未来100~300 a的近岸海域可能的酸化水平,研究其对海水青鳉鱼成鱼耳石形态及主要元素成分的影响。研究发现,在高浓度CO2（980 ppm、2900 ppm和4850 ppm）的酸化水体中养殖青鳉鱼成鱼45 d,青鳉鱼体长和体重与对照组差异不显著,内耳中矢耳石、星耳石和微耳石的形状,包括耳石表面积和圆趋近率,没有受到酸化的影响。然而,随着水体中CO2浓度升高,矢耳石的重量则呈现下降的趋势,其中2900 ppm和4850 ppm高浓度组矢耳石重量显著低于对照组。在2900 ppm酸化处理组中,左右耳石不对称性趋势明显。而且,酸化处理组中,实验鱼耳石中C元素相对含量显著低于对照组。高浓度CO2酸化海水对青鳉鱼成鱼的耳石形态和成分的影响,可能干扰其听觉,并对捕食、防御敌害等听觉相关行为造成影响。

以海水青鳉作为研究对象,研究海洋酸化对其性别分化的影响。将刚受精的受精卵置于对照组(CO2浓度为480×10-6)和2个处理组(CO2浓度分别为1 000×10-6和2 000×10-6)的水体中,直到孵化出膜。将出膜后仔鱼饲养在对照组水体中至性成熟,然后通过形态学、组织学和遗传学方法,对每一尾实验鱼进行表现型和基因型的性别鉴定。经形态学判断,发现酸化处理组的雄雌比例显著高于对照组（P＜0.01）。经形态学观察其第二性征和遗传学性别判断,对照组的青鳉从孵化到性成熟的个体中并未出现基因型和表现型性别不一致的个体,而在2个酸化处理组中,均有基因型为XX而表现型为雄性的个体,即性逆转雄性,性逆转率分别为38.4%和47.5%。

海洋酸化是人为CO2排放引起的又一重大环境问题，大量研究表明海洋钙化生物面临来自酸化的巨大威胁，近年来酸化对鱼类等非钙化生物的影响也逐渐引起关注。有报道海洋酸化能够影响珊瑚礁仔鱼的感觉和行为，但其影响机制未知。逃跑行为对于鱼类的存活至关重要，该行为主要由声音诱发产生。本课题以海水青鳉鱼作为实验材料，研究海水酸化对其逃跑行为影响的机制。首先开展海水酸化对青鳉鱼早期发育及逃跑行为的影响的研究，结果表明酸化海水对青鳉鱼的逃跑行为的发生概率及行为发生的延迟时间与对照组有显著不同，并且对青鳉鱼两眼间距、眼睛发育及脑发育产生影响。由于，由声音诱发的逃跑行为是受环境因素精确调控的，继而开展了酸化对内耳耳石、骨骼等钙化器官影响研究，发现酸化组耳石重量变重，左右耳石不对称性增加，这可能影响鱼类听觉，进而影响逃跑行为。C-fos 即刻蛋白是在受到刺激的初期高度表达，而后下降，但是它作为第三信使，可以联系胞外刺激与机体长期适应的一个纽带。青鳉鱼受到酸化处理后，大脑在30min分钟内表达C-fos蛋白，并在不同脑区的表达存在时间上的差异。较早在端脑区表达，而后在中脑、后脑中陆续表达。已有报道海洋算算主要是通过改变GABAA受体功能，从而改变鱼类的神经活动。因此，利用免疫组化、蛋白免疫印记等技术，研究酸化对GABA受体以及谷氨酸在青鳉鱼脑部受体表达区域以及表达量的影响。研究发现酸化处理的实验组NMDA受体在延脑及第四脑室附近的分布比对照组数目略多，且酸化处理的实验组NMDA受体测量荧光信号光密度值远大于对照组即NMDA受体的表达强度更大。推测，海洋酸化对青鳉鱼脑部谷氨酸受体表达有影响，这可能是其C-start行为发生异常的原因。

海洋酸化是指大气增多的二氧化碳（CO2）溶解于海水而导致海水p H值降低的过程。海洋酸化将改变海水碳酸盐平衡体系,使依赖于原化学环境的多种海洋生物乃至生态系统面临巨大威胁。海洋酸化对钙质生物影响的研究最早引起大家关注,而海洋鱼类具有较完善的酸碱调节机制,大家普遍认为酸化对其影响不大。但在过去的5年中,不少实验证明海洋酸化会影响海洋鱼类仔稚鱼的感觉和行为,减弱其野外的生存能力及增加被捕食率,很可能将威胁自然种群补给量和影响全球的渔业资源量。本文从嗅觉、听觉、视觉及高级意识和相关行为角度,综述近几年海洋酸化对鱼类感觉和行为影响的研究进展,介绍了鱼类神经行为生物学的研究,为全面了解和预测海洋酸化的生态、经济和社会效应提供科学依据。