繁殖期4种淡水鱼类化学预警行为及其与性腺指数的关联

化学预警信息（Chemical alarm cue,CAC）在鱼类捕食者-猎物关系中发挥重要作用,并与二者生存适合度密切关联。繁殖期鱼类的繁殖生理投入和化学预警响应均具有较高的能量需求,因而可能存在某种程度上的生存-繁殖的权衡（Trade-off）。选取高体鳑鲏（Rhodeus ocellatus,卵生,繁殖投入较低）、斑马鱼（Danio rerio,卵生,繁殖投入较高）、孔雀鱼（Poecilia reticulata,卵胎生,繁殖投入较高）和皮球鱼（Poecilia latipinna,卵胎生,繁殖投入很高）等繁殖方式各异、能量投入不同的4种淡水鱼类为实验对象,测定了繁殖IV期实验鱼对不同浓度的化学预警信息（Damage-released chemical alarm cues,DCAC）的行为响应模式,并探究了4种实验鱼的化学预警响应与其性腺指数（Gonadosomatic index,GSI）的关联。结果表明：（1）DCAC对4种实验鱼的空间分布、活跃状态、逃逸行为等大部分化学预警响应参数均有不同程度的影响（P<0.05）;（2）4种实验鱼GSI与其化学预警响应参数的变化无显著相关性（P>0.05）（除高浓度DCAC处理组皮球鱼GSI与底栖时间的变化负相关外）。研究回答了长期以来有关繁殖期鱼类化学预警通讯是否缺失的问题,证实了繁殖期不同繁殖生理投入/繁殖对策的4种淡水鱼类均有显著的化学预警响应,提示鱼类GSI与其化学预警响应程度通常不相关（仅高风险环境下繁殖生理投入很高的物种中可能呈现负相关）。     

圈养林麝(Moschus berezovskii)个性及与麝香分泌和繁殖成效的关系

于2016年6月20日至8月10日在四川马尔康林麝繁育场开展,采用基于量表的个性评价法对172头（雌麝59头,雄麝113头）圈养林麝进行了个性评价,建立了圈养林麝个性维度,并探索了个性维度与其麝香分泌和繁殖成效的关系。结果表明：因子分析各项载荷值均大于0.4,Cronbach''s α分析结果为0.648,表明个性量表具有较好的一致性信度和结构效度。此外,特征根大于1时,圈养林麝的侵略性、活跃性、刻板性、胆怯性及社会性五大个性维度可解释70.77%的个性信息,并通过聚类分析,进一步验证了维度划分的合理性;雄性林麝的社会性维度和麝香分泌量存在显著正相关（r=0.234,P < 0.05）,社会性越强（展现出更多的互饰接触、共同摄食等亲和行为的个体）,其泌香量越高;侵略性（r=0.463,P < 0.05）、活跃性（r=0.440,P < 0.05）、刻板性（r=0.595,P < 0.05）与雌性分娩时间存在显著正相关关系,即个性越强,分娩时间越晚,此外,刻板性与产仔数呈显著负相关（r=-0.341,P < 0.05）,表明圈养林麝的繁殖成效主要受刻板性维度影响,刻板性强的个体对繁殖成效会有一个负面的效应。     

繁殖期高体鳑鲏对化学预警信息的行为响应及其与生理状态的关联

对化学预警信息(Chemical alarm cues,CAC)的识别与应答体现了鱼类在特定生理状态和特定环境下的生态策略,与动物的生存适合度密切相关。由于化学预警通讯和繁殖均为高能耗的生命活动,繁殖期鱼类的CAC通讯是否表现出基于能量代价-收益(Cost-benefit)的权衡成为值得关注的科学问题。本研究以具有特殊繁殖方式的高体鳑鲏(Rhodeus ocellatus)为实验对象,测定了繁殖IV期不同性别实验鱼对CAC的行为响应,并探究了实验鱼化学预警行为与其繁殖生理状态的关系。结果发现:(1)高体鳑鲏空间分布状态(底栖时间)和活跃状态(静止时间、运动距离、身体不重合度)均对CAC表现出明显的行为应答(P0.05),但逃逸行为(高速运动时间)不受CAC的影响(P0.05);(2)高体鳑鲏对CAC的响应无性别差异;(3)高体鳑鲏预警行为的变化与繁殖生理状态(性腺指数、产卵管长度、肥满度)无显著相关性(P0.05)。结果表明,繁殖期高体鳑鲏依然对CAC展现出一定程度的行为应答,然而其行为响应程度并不受繁殖生理状态以及性别的影响,这可能主要与该物种特殊的繁殖对策有关。     

盐度胁迫下曼氏无针乌贼的行为和生理响应

盐度变化会引起头足类动物渗透调节、免疫能力和激素分泌异常等一系列生理应激反应，同时还会引发应激诱导的喷墨行为等异常行为变化，最终可能导致头足类因渗透失衡出现大量死亡。结合头足类苗种繁育过程中因海水盐度波动出现的摄食及行为异常等问题，探究了盐度胁迫对曼氏无针乌贼（Sepiella japonica）行为活跃性、组织结构、渗透调节以及免疫相关酶活性的影响，明确了其对盐度变化的应激反应及适应能力。结果显示：在高盐胁迫下曼氏无针乌贼的行为活跃性显著增加（P<0.05），且倾向于绕水槽壁游动；与21‰组相比，27‰组和33‰组肌肉、鳃和肝脏组织结构呈现较严重的损伤，15‰组的各组织结构无明显变化；随着盐度的升高，鳃中Na⁺/K⁺-ATP酶活性呈现先降低后升高趋势（P<0.05）；33‰组脑中皮质醇含量显著高于其他处理组（P<0.05）；盐度升高或降低均会导致鳃和肝脏中超氧化物歧化酶（Superoxide dismutase，SOD）、过氧化氢酶（Catalase，CAT）活性显著升高（P<0.05），丙二醛（Malondialdehyde，MDA）含量显著增加（P<0.05），溶菌酶（Lysozyme，LZM）活性显著降低（P<0.05）。综合分析认为，曼氏无针乌贼具有较好的耐低盐能力，高盐胁迫会引发其类焦虑行为。此外，在研究设定的15‰-33‰盐度范围内，盐度变化还会引起其渗透调节以及免疫相关酶活性的改变。研究结果为阐释头足类适应盐度波动的调节机理，控制适宜的养殖环境提供了参考依据。     

模拟失重不同时长对大鼠抑郁样行为的影响

目的 本研究旨在观察不同持续时间的模拟失重对大鼠抑郁样行为和海马超氧化物歧化酶（SOD）和过氧化氢酶（CAT）的影响，以探究其影响及可能的作用机制。方法 采用后肢悬挂（HLS）尾吊法模拟大鼠失重状态。将大鼠分为对照组和不同模拟失重时间尾吊组（尾吊时长分别为1、2、3、4周）。采用旷场实验（OFT）、新物体识别实验（NORT）、强迫游泳实验（FST）观察大鼠抑郁样行为，采用酶联免疫吸附试验（ELISA）法测定海马SOD和CAT活性。结果 OFT结果显示，与对照组相比，HLS不同时间大鼠的僵滞时间增加（P<0.05，P<0.01）。在NORT中，与对照组相比，HLS不同时间大鼠对新物体的探索潜伏期增加，探索次数和时间减少（P<0.05，P<0.01）。在FST中，与对照组相比，HLS不同时间大鼠在FST中的不动时间增加，攀爬次数减少（P<0.05，P<0.01）。与对照组相比，HLS不同时间组大鼠海马组织中SOD和CAT水平均下降（P<0.05，P<0.01）。结论 短时间或长时间的失重都会导致大鼠产生类抑郁样行为。     

高寒草甸物种多样性对藏系牧羊放牧行为的影响

为探究草原植物物种多样性对家畜放牧行为的影响及其机制,在青藏高原高寒草甸开展藏系牧羊轮牧试验,调查植被物种多样性,观察藏系牧羊采食速率、觅食速率和采食时间,并计算藏系牧羊日采食量。结果表明：两年间,植物物种丰富度与藏系牧羊采食速率呈显著正相关关系（P<0.05）;觅食速率、采食时间和日采食量对放牧率响应敏感（P<0.05）,呈夏秋增冬春减的趋势。植物Shannon-Wiener指数与藏系牧羊的采食时间显著负相关（P<0.05）;在暖季或8羊/hm²放牧率下植物Shannon-Wiener指数与藏系牧羊日采食量呈显著正相关（P<0.05）。Pilelou均匀度指数与藏系牧羊采食速率和采食时间显著负相关（P<0.05）;在暖季或8羊/hm²放牧率下Pilelou均匀度指数与藏系牧羊日采食量呈显著负相关（P<0.05）。植物物种丰富度对藏系牧羊放牧行为贡献较大,且放牧藏系牧羊的采食速率和采食时间比觅食速率和日采食量对植物物种丰富度响应更敏感,以用植物物种丰富度为自变量可以更好预测藏系牧羊放牧行为。放牧管理通过影响植被物种多样性从而进一步影响了藏系牧羊放牧行为。放牧行为不仅是评价草地营养价值和家畜生产力的关键指标,也是草地健康管理的基础。因此,明确草原植物物种多样性-藏系牧羊放牧行为的互作机制有助于更好的提高藏系牧羊地生产力,维护草原生态健康。     

克氏针茅草原群落物种多样性与生物量关系对放牧强度的响应

放牧强度引起的草原植物群落物种多样性与地上生物量变化是近年来草地生态系统研究的热点问题。以内蒙古锡林郭勒克氏针茅草原为研究对象,探究植物群落结构特征、物种多样性与地上生物量之间相互关系及其对不同放牧强度的响应。结果表明：随着放牧强度的增加植物群落结构逐步向退化方向演替;植物群落高度逐渐降低（P<0.05）,密度逐渐增加（P<0.05）,盖度总体呈下降趋势（P<0.05）;植物群落和原有群落优势种地上生物量总体呈下降趋势（P<0.05）,而退化指示物种的地上生物量逐渐增加（P<0.05）;轻度、中度放牧条件下群落物种Margalef指数、Pielou指数、Simpson指数均显著高于重度放牧（P<0.05）;地上生物量与Shannon-Wiener指数、Margalef指数和Pielou指数呈正相关关系,而与Simpson指数呈负相关关系。综上所述,克氏针茅草原植物群落结构和功能在不同放牧强度下产生不同的响应,适度放牧有利于提高群落物种多样性与生物量。     

热岛效应下亚热带城市植被叶气孔权衡特征及其与叶功能性状的关系

叶片气孔不仅是植物平衡光合-蒸腾关系的重要门户,也是影响大气碳循环与水循环的关键结构。分析热岛效应下福州市乔木、灌木、草本3种生活型和常绿、落叶2种叶习性植物的气孔性状间的差异及其与其他叶功能性状间的权衡关系有助于探究不同类型植物在热环境下的适应策略。以福州市区的自然和半自然植被为研究对象,测定441个植物样本的气孔特征、化学计量特征和形态特征,结果表明：（1）3种生活型、2种叶习性植物的气孔长度（SL）、气孔密度（SD）差异显著（P<0.05）,潜在气孔导度指数（PCI）不存在显著差异（P>0.05）。草本的SL高于灌木和乔木,乔木的SD最高,灌木次之,草本最低;落叶植物的SL高于常绿植物,SD低于常绿植物。（2）SL与SD间的权衡关系稳定存在于3种生活型和2种叶习性植物中,且随着不同生活型和落叶习性植物的生态策略而呈现各异的权衡特征,即当SL一定时,乔木的SD最大,灌木的SD最小,常绿植物的SD大于落叶植物。（3）气孔性状和叶片形态、化学计量特征紧密联系,SL与比叶面积（SLA）正相关（P<0.01）,与叶面积（LA）负相关（P<0.01）;SD与叶氮含量（LNC）、叶磷含量（LPC）、SLA负相关（P<0.01）,与LA正相关（P<0.01）;PCI与LNC、SLA负相关（P<0.01）,与叶厚度（LT）正相关（P<0.05）。（4）复杂的环境是气孔性状变异的重要驱动因素,SL、PCI均与年均温（MAT）负相关（P<0.05）。     

增温对南亚热带常绿阔叶林4种幼树生长和碳氮磷化学计量特征的影响

为了解不同物种在气候变暖条件下的生长及养分利用策略,研究选取南亚热带常绿阔叶林4种具代表性的典型乔木树种幼苗（1年生）木荷（Schima superba）、红锥（Castanopsis hystrix）、红枝蒲桃（Syzygium rehderianum）和海南红豆（Ormosia pinnata）为研究对象。采用红外-箱式增温的方法（2016年1月至2018年12月期间,年平均气温升高2.26℃,P<0.05）,研究了4种幼苗生长以及各器官中C、N、P化学计量特征和非结构性碳水化合物（NSC）含量对增温的响应。结果表明：增温促进了红锥和海南红豆（除2017年6月）的生长,但降低了木荷（增温1年后）和红枝蒲桃的生长（P<0.05）。增温显著降低了木荷细根、红锥茎干和海南红豆枝的P含量（P<0.05）,与对照相比,分别降低了1.91%、18.70%和46.07%。增温增加了固氮物种海南红豆细根N含量,但降低了其叶片N含量（P<0.05）,增温对其它树种N含量无显著影响。木荷茎干N∶P和海南红豆的细根N∶P在增温下分别升高了30.42%和90.29%（P<0.05）。此外,增温显著升高了木荷和红枝蒲桃叶片的可溶性糖含量（P<0.05）。以上结果表明,增温对南亚热带常绿阔叶林植物的影响存在种间差异,木荷和红枝蒲桃在增温条件下生长受限,但促进了红锥和海南红豆的生长,未来气候变暖可能会改变该生态系统的养分竞争平衡,进而可能会改变群落组成。     

具核梭杆菌脂多糖诱导THP-1细胞M2极化及对低浓度白介素6产生的作用

[背景] 在结直肠肿瘤等多种肿瘤中普遍存在的具核梭杆菌（Fusobacterium nucleatum）与结直肠肿瘤发生、预后不良、复发及化疗耐药等密切相关。其引发炎症、对肿瘤微环境中巨噬细胞等免疫细胞作用与机制尚待阐明。[目的] 对比分析F.nucleatum脂多糖（Lipopolysaccharide,LPS）与嗜黏蛋白阿克曼氏菌（Akkermansia muciniphila）、大肠杆菌（Escherichia coli）的LPS诱导单核细胞极化、炎性细胞因子表达等活性差异,探讨F.nucleatum在诱发慢性炎症、致癌等过程中的作用与机制。[方法] 分别用A.muciniphila、E.coli、F.nucleatum LPS或联合干扰素γ（Interferon-γ,IFN-γ）处理后,观察THP-1、THP-1 M0细胞的细胞形态变化,然后检测M0（CD11B）、M1（CD40、CD86）和M2（CD163、CD206）巨噬细胞标志基因、TLR3、TLR4、IL-6、IL-10等基因转录水平,以及IL-6、IL-10、C反应蛋白（C Reactive Protein,CRP）翻译水平的表达变化。[结果] 聚丙烯酰胺凝胶电泳（Polyacrylamide Gel Electrophoresis,PAGE）分析显示,A.muciniphila、E.coli、F.nucleatum这3种细菌的LPS条带位置、数量存在明显差异。F.nucleatum LPS在具有较强诱导THP-1细胞贴壁的同时,对经佛波肉豆蔻醋酸（Phorbol Myristate Acetate,PMA）处理贴壁的THP-1细胞,无论是单独或是联合IFN-γ处理,诱导形成伪足数、伪足长度及形成梭形细胞比例（M1型巨噬细胞）等均低于A.muciniphila和E.coli LPS。进一步转录水平检测巨噬细胞标志基因表达发现,M1标志基因中,CD40分别上调5 011.0%（P<0.001）、6 048.9%（P<0.001）和1 011.6%（P=0.009 4）,CD86分别上调637.3%（P<0.001）、657.9%（P<0.001）和194.1%（P>0.05）;M2标志基因中,CD163分别下调39.5%（P=0.001 1）、53.7%（P<0.001）和5.9%（P>0.05）,CD206下调18.6%（P>0.05）、88.4%（P=0.005 5）和24.8%（P>0.05）。TLR、白介素家族基因转录水平分析发现,TLR3分别下调32.3%（P=0.044 7）、311.5%（P=0.001 9）、9.6%（P>0.05）;IL-6分别上调17 763.2%（P<0.001）、35 458.2%（P<0.001）、1 123.6%（P>0.05）;IL-10分别上调729.3%（P<0.001）、1 223.3%（P<0.001）、124.4%（P>0.05）。翻译水平上,A.muciniphila、E.coli、F.nucleatum LPS单独或联合IFN-γ处理时,THP-1细胞产生IL-6分别为0.16、6.17、0 pg/mL与410.03、1 334.40、46.20 pg/mL。[结论] F.nucleatum LPS不仅具有较强招募单核细胞并诱导其向M2极化的作用,同时,具有诱导巨噬细胞分泌低浓度IL-6的特性,说明其在引发慢性炎症及肿瘤免疫应答、逃逸等过程中发挥重要作用。综合上述信息,对致癌、免疫激活及肿瘤治疗相关细菌LPS的结构、活性、分子机制等研究将有助于明确革兰氏阴性细菌在慢性炎症、肿瘤发生、免疫调控等中的作用,以期为相关疾病预防与治疗提供新的策略与靶点。     

Conspecific alarm cue sensitivity by the estuarine calanoid copepod,Paracartia longipatella

Sensitivity to chemical cues associated with predation threat has been well observed in many freshwater zooplankters, yet few studies have highlighted such sensitivity in eury‐ and stenohaline metazoans. We aimed to assess sensitivity to conspecific chemical alarm cues in the estuarine copepod, Paracartia longipatella. Alarm cues associated with predation have been shown to have population level effects on certain zooplanktonic species. As such, we assessed the occurrence of such effects on population dynamics of P. longipatella over a 12 day period. Using experimental in situ mesocosms, we compared P. longipatella adult, copepodite and nauplii numbers between three treatments; one inoculated with conspecific alarm cues, one containing direct predation pressure (zooplanktivorous fish), and a control treatment containing no predation threat. Trends in population abundances were similar between the direct predation and alarm cue treatments for the six days of the experiment, decreasing in abundance. During the latter half of the study, however, P. longipatella abundances in the alarm cue treatment increased, while those in the presence of direct predation continued to decrease. In the treatment absent of any predation threat, P. longipatella abundances increased consistently over time for the duration of the study. We suggest that P. longipatella are indeed sensitive to conspecific alarm cues associated with predation threat. Furthermore, we propose that prolonged exposure to conspecific alarm cues in the absence of any real threat results in a reduction in sensitive to these cues.     

Anti-predator behaviour in response to conspecific chemical alarm cues in an esociform fish, <Emphasis Type="Italic">Umbra limi</Emphasis> (Kirtland 1840)

When a predators attack prey, damaged prey tissue releases chemical information that reliably indicates an actively foraging predator. Prey use these semiochemicals to cue anti-predator behaviour and reduce their probability of predation. Here, we test central mudminnows, Umbra limi (Kirtland 1840), for anti-predator behavioural responses to chemical cues in conspecific skin extract. In a field experiment, traps scented with mudminnow skin extract (alarm cue) caught fewer mudminnows than traps scented with water (control). Under controlled laboratory conditions, mudminnows showed a significant reduction in activity and movement to the bottom in response to alarm cues relative to water controls. Reduced activity and increased time on the bottom of the tank are both known components of an anti-predator response. Thus, based on field and lab data, mudminnows exhibited anti-predator behavioural responses to chemical alarm cues released by damaged epidermal tissue. Histological preparations of epidermal tissue did not reveal the presence of specialised “alarm substance” cells for the production of chemical alarm cues. This is the first report of an alarm reaction in an esociform, an order with a long evolutionary history of piscivory.     

There must be something in the water: assessing the behavioral responses of rusty crayfish (<Emphasis Type="Italic">Orconectes rusticus</Emphasis>) to fish and amphibian predator kairomones

Animals use chemical cues to find food, locate mates, and detect potential predators. Detecting cues in a risky environment can induce behavioral changes to increase survival. Rusty crayfish (Orconectes rusticus) reduce activity, increase refuge use, and make defensive displays after detecting fish predator cues. However, no studies have introduced amphibian cues. We investigated crayfish responses to hellbender salamander (Cryptobranchus alleganiensis, a dominant predator of crayfish) cues and compared these to responses to largemouth bass (Micropterus salmoides) cues. Largemouth bass occur sympatrically with hellbenders and are known to induce distinct responses in rusty crayfish. We randomly assigned crayfish to predator cue and conspecific alarm cue combinations and recorded frozen behavior, appendage movement, locomotion, and refuge use. We found crayfish increased their proportion of time spent frozen and reduced their proportion of time spent active in the tank when exposed to either predator cue. Moreover, these responses were magnified when crayfish were exposed to predator cues in combination with conspecific alarm cues. Our experiment demonstrates evidence in support of the crayfish’s ability to detect and appropriately respond to predator cues alone and in combination with conspecific alarm cues. Future work should investigate the effects of these behavioral changes on trophic dynamics in a natural system.     

Predator Inspection Behaviour in a Characin Fish: an Interaction between Chemical and Visual Information?

Recent evidence suggests that predator inspection behaviour by Ostariophysan prey fishes is regulated by both the chemical and visual cues of potential predators. In laboratory trials, we assessed the relative importance of chemical and visual information during inspection visits by varying both ambient light (visual cues) and predator odour (chemical cues) in a 2 × 2 experimental design. Shoals of glowlight tetras (Hemigrammus erythrozonus) were exposed to a live convict cichlid (Archocentrus nigrofasciatus) predator under low (3 lux) or high (50 lux) light levels and in the presence of the odour of a cichild fed tetras (with an alarm cue) or swordtails (Xiphophorus helleri, with an alarm cue not recognized by tetras). Tetras exhibited threat‐sensitive inspection behaviour (increased latency to inspect, reduced frequency of inspection, smaller inspecting group sizes and increased minimum approach distance) towards a predator paired with a tetra‐fed diet cue, regardless of light levels. Similar threat‐sensitive inspection patterns were observed towards cichlids paired with a swordtail‐fed diet cue only under high light conditions. Our data suggest that chemical cues in the form of prey alarm cues in the diet of the predator, are the primary source of information regarding local predation risk during inspection behaviour, and that visual cues are used when chemical information is unavailable or ambiguous.     

Underwater Video Reveals Strong Avoidance of Chemical Alarm Cues by Prey Fishes

A diversity of fishes release chemical cues upon being attacked by a predator. These cues, commonly termed alarm cues, act as sources of public information warning conspecifics of predation risk. Species which are members of the same prey guild (i.e. syntopic and share predators) often respond to one another's alarm cues. The purpose of this study was to discriminate avoidance responses of fishes to conspecific alarm cues and cues of other prey guild members from responses to unknown damaged fish odours and novel odours. We used underwater video to measure avoidance responses of freshwater littoral species, namely fathead minnows (Pimephales promelas), finescale dace (Chrosomus neogaeus), and brook stickleback (Culaea inconstans), to both injured fish cues and novel non‐fish odours. The cyprinids (minnows and dace) showed significant avoidance of minnow cues over swordtail cues, morpholine, and the control of distilled water and tended to avoid fathead cues over cues of known prey guild members (stickleback). Cyprinids also significantly avoided cues of stickleback over unknown heterospecific cues (swordtail) and tended to avoid stickleback cues over morpholine and the distilled water control. Stickleback significantly avoided fathead minnow extract over the distilled water and tended to avoid stickleback and swordtail over distilled water. We conclude that fishes in their natural environment can show dramatic changes in behaviour upon exposure to alarm cues from conspecifics and prey guild members. These responses do not represent avoidance of cues of any injured fish or any novel odour.     

Predator recognition learning in rainbow darters Etheostoma caeruleum: specific learning and neophobia

This study investigated whether rainbow darters Etheostoma caeruleum can learn to recognize unfamiliar predators through the process of classical conditioning. Etheostoma caeruleum were conditioned by exposing them simultaneously to their chemical alarm cues (a known fright stimulus) and either chemical cues from larval ringed salamanders Ambystoma annulatum (unfamiliar predator) or to a blank water cue (control). Conditioning could result in either specific learning of the A. annulatum cue or increased wariness in response to any novel cue (neophobia). To distinguish between these possibilities, E. caeruleum in both groups were exposed to either A. annulatum cues alone or to chemical cues from western rat snakes Pantherophis obsoletus (novel cue) 2 days after conditioning. Treatment (A. annulatum‐conditioned) E. caeruleum, but not control E. caeruleum, showed a fright response when they were exposed to both the conditioned (A. annulatum) and novel (P. obsoletus) cues, indicating increased sensitivity to new stimuli. When E. caeruleum were retested after an additional 32 days, however, the fright response occurred only following exposure to the conditioned (A. annulatum) stimulus, indicating that specific learning of the A. annulatum cue had been retained whereas the neophobia to novel stimuli was temporary.     

Predation risk assessment by olfactory and visual cues in a coral reef fish

Assessment of predation risk is vital for the success of an individual. Primary cues for the assessment include visual and olfactory stimuli, but the relative importance of these sources of information for risk assessment has seldom been assessed for marine fishes. This study examined the importance of visual and chemical cues in assessing risk for the star goby, Asterropteryx semipunctatus. Visual and chemical cue intensities were used that were indicative of a high threat situation. The behavioural response elicited by both the visual cues of a predator (the rock cod, Cephalopholis boenak) and the chemical alarm cues from conspecifics were similar in magnitude, with responses including a decrease in feeding strikes and moves. A bobbing behaviour was exhibited when the predator was visible and not when only exposed to the chemical alarm cue. When visual and chemical cues were presented together they yielded a stronger antipredator response than when gobies were exposed solely to conspecific alarm cues. This suggests additivity of risk assessment information at the levels of threat used, however, the goby’s response is also likely to depend on the environmental and social context of the predator–prey encounter. This study highlights the importance of chemical cues in the assessment of predation risk for a coral reef fish.     

The Diel Activity of Crucian Carp, Carassius Carassius, in Relation to Chemical Cues from Predators

Chemical cues from piscivorous fish and prey alarm substances often cause rapid fright responses in prey. However little is known of how piscivore-related chemical cues affect prey behaviour over periods longer than a few hours. Here we have investigated how chemical cues from piscivorous northern pike, Esox lucius, affect habitat choice and diel activity of crucian carp, Carassius carassius, over an extended period 11 days. At the beginning of the experiment control fish were nocturnal while fish in the pike cue treatment were aperiodic. After 11 days, control fish had become more strongly nocturnal and displayed two activity peaks during early and late night whereas fish in the pike cue treatment were still aperiodic with no activity peaks. Habitat choice was aperiodic in both treatments throughout the experiment. In both treatments, more fish were found in the vegetation zone than in the open habitat. This was most pronounced when pike cues were present. These results demonstrate that short-term anti-predator responses to chemical cues from predators can translate into long-term adjustments of diel periodicity. Further, the results did not support the idea that crucian carp should switch to nocturnal activity in response to visually hunting predators. Control fish were nocturnal and chemical cues from pike did not make this pattern more pronounced.     

Smell, learn and live: The role of chemical alarm cues in predator learning during early life history in a marine fish

The speed with which individuals can learn to identify and react appropriately to predation threats when transitioning to new life history stages and habitats will influence their survival. This study investigated the role of chemical alarm cues in both anti-predator responses and predator identification during a transitional period in a newly settled coral reef damselfish, Pomacentrus amboinensis. Individuals were tested for changes in seven behavioural traits in response to conspecific and heterospecific skin extracts. Additionally, we tested whether fish could learn to associate a previously novel chemical cue (i.e. simulated predator scent) with danger, after previously being exposed to a paired cue combining the conspecific skin extract with the novel scent. Fish exposed to conspecific skin extracts were found to significantly decreased their feeding rate whilst those exposed to heterospecific and control cues showed no change. Individuals were also able to associate a previously novel scent with danger after only a single previous exposure to the paired conspecific skin extract/novel scent cue. Our results indicate that chemical alarm cues play a large role in both threat detection and learned predator recognition during the early post-settlement period in coral reef fishes.