摘要
为深入了解柔鱼食性,探明其在食物网中的位置和生态功能价值,根据2022年6—8月于西北太平洋公海采集的15尾柔鱼样本,采用高通量测序技术分析其食物组成。结果显示,15尾样品的高通量序列为646 980条,通过聚类分析共得到624个运算分类单元(OTU),经筛选比对检测到的饵料共计65种,分属6门11纲22目37科51属。研究表明,柔鱼主要摄食头足类、鱼类以及多种浮游动物(包括磷虾类、介形类、水母类等)。优势饵料包括拟沙丁鱼、日本爪乌贼、北方拟黵乌贼、萤乌贼、尾棘背灯鱼等。柔鱼摄食范围广,饵料物种与海区的天然饵料有关;不同胴长组柔鱼表现出不同的摄食偏好。通过柔鱼胃含物的全组成分析,对深度挖掘摄食与柔鱼生长、洄游、繁殖等生活史的关系有重要作用,同时为基于生态系统角度的柔鱼资源可持续开发和养护提供科学依据。
柔鱼(Ommastrephes bartramii)是一种重要的海洋经济头足类,目前对于柔鱼的开发集中在北太平洋海
柔鱼的食性研究方法有胃含物形态学鉴定法、稳定同位素分析法、脂肪酸标记法、高通量测序技术等。胃含物形态学鉴定法主要依赖胃肠道中未被完全消化的组织器官的形态学特征进行鉴定,对鉴定人员的专业能力要求较高,且无法获取相对完整的饵料种类信
柔鱼样本于2022年6—8月由上海海洋大学“淞航”号渔业资源科考船在执行农业农村部公海渔业资源综合科学调查期间,在西北太平洋公海海域(157°22′22″E~164°01 ′16″E,38°00′18″N~44°12′16″N)采集。样本在船上-20 ℃条件下冻存,待船靠岸后立即运往实验室进行后续研究。
所有样本采集、实验流程、研究方法均严格按照《上海海洋大学实验室动物伦理规范》和上海海洋大学伦理委员会制定的规章制度执行。
柔鱼样本在实验室解冻清洗后,测定胴长、体质量、性别、性成熟度等基础生物学数据。其中,长度精确至1 mm,质量精确至1 g。随机选取15尾柔鱼样本取出胃并称取胃质量和胃净质量(精确至0.000 1 g)。采用DNA研磨仪(Tube Mill 100 control)将胃含物研磨均匀,移入无菌离心管中,-80 ℃保存待测。
将胃含物充分匀浆并离心后,提取基因组DNA,使用引物COIintF(GGWACWGGWTGAACWGTWTAYCCYCC)和jgHCO2198R(TANACYTCNGGRTGNCCRAARAAYCA)进行目的基因扩增,利用1×TAE的2%琼脂糖凝胶电泳检测。PCR扩增体系:2×proTaq DNA聚合酶10 μL,正反引物(5 μmol)各0.8 μL,DNA模板10 ng/μL,补ddH2O至20 μL。PCR程序:95 ℃预变性5 min,95 ℃变性60 s, 47 ℃退火120 s, 72 ℃延伸60 s,反应循环数为35,最后72 ℃延伸5 min。PCR产物用2%琼脂糖凝胶电泳检测,使用AxyPrepDNA凝胶回收试剂盒(AXYGEN公司)进行纯化,Tris-HCl洗脱。利用QuantiFluor™ -ST蓝色荧光定量系统(Promega公司)将PCR产物检测定量。利用TruSe
将柔鱼样本依据胴长大小按照一定的组间距划分为不同的胴长组,根据统计结果,将15尾柔鱼样本分为3个胴长组,分别为160~219 mm、340~399 mm和400~459 mm(

图1 柔鱼样本胴长分布和平均摄食强度
Fig.1 Distribution of mantle length and average feeding intensity of Ommastrephes bartramii
15尾柔鱼样本的高通量测序统计结果:共获得平均长度为312 bp的序列723 721条,其中有效序列为646 980条,分属624个OTU。样品序列数最高为55 556条,最低为43 152条,平均序列数为(48 248±3 946)条。去除注释结果中浮游植物、细菌、病毒、寄生虫等,剩余序列数为59 220,分属80个OTU。稀释曲线可说明样本的测序数量是否合理,且可用来比较测序量不同的样本中物种的丰富度、均一性和多样性。稀释曲线(

图2 各样本的稀释曲线
Fig.2 Rarefaction curve of each sample
柔鱼的食物组成包括鱼类、头足类、浮游动物等,经过高通量测序共检测到饵料物种65种,分属6门11纲22目37科51属。门分类水平上,软体动物门和脊索动物门的相对丰度较高,总和高达90.60%,其余占比大小依次为节肢动物门>刺胞动物门>栉水母动物门>毛颚动物门。在属水平上,除Z10样本的优势饵料为细足磷虾属(Nematoscelis)以外,单个样本的优势饵料通常为某一种鱼类或头足类(

图3 单个样本中饵料组成情况(属水平上)
Fig.3 Food composition in a single sample(on Genus level)
饵料物种 Prey species | 相对丰度百分比 Percentage of abundance/% | 出现频率 Occurrence rate/% | 排序 Rank |
|---|---|---|---|
| 拟沙丁鱼Sardinops sagax | 24.900 | 73.33 | 1 |
| 日本爪乌贼Onychoteuthis borealijaponica | 7.678 | 13.33 | 2 |
| 北方拟黵乌贼Gonatopsis borealis | 6.490 | 13.33 | 3 |
| 萤乌贼Watasenia scintillans | 5.115 | 20.00 | 4 |
| 瘦细足磷虾Nematoscelis gracilis | 4.862 | 6.67 | 5 |
| 尾棘背灯鱼Notoscopelus caudispinosus | 4.558 | 6.67 | 6 |
| 大西洋大梭蜥鱼Magnisudis atlantica | 3.747 | 6.67 | 7 |
| 日本背灯鱼Notoscopelus japonicus | 2.639 | 13.33 | 8 |
| 长体标灯鱼Symbolophorus californiensis | 1.091 | 13.33 | 9 |
| 双浮萤属Discoconchoecia spp. | 0.735 | 6.67 | 10 |
| 哈氏直浮萤Orthoconchoecia haddoni | 0.648 | 6.67 | 11 |
| 长额磷虾Euphausia diomedeae | 0.507 | 6.67 | 12 |
| 琴型伪箭虫Pseudosagitta lyra | 0.384 | 6.67 | 13 |
| 太平洋磷虾Euphausia pacifica | 0.351 | 53.33 | 14 |
| 白身臂灯鱼Stenobrachius leucopsarus | 0.349 | 13.33 | 15 |
| 大浮萤Conchoecia magna | 0.336 | 6.67 | 16 |
| 细足磷虾属Nematoscelis spp. | 0.327 | 6.67 | 17 |
| 双翼平头水蚤Candacia bipinnata | 0.317 | 13.33 | 18 |
| Nematoscelis difficilis | 0.193 | 13.33 | 19 |
| 卷叶磷虾Euphausia recurva | 0.163 | 13.33 | 20 |
柔鱼摄食的鱼类主要为灯笼鱼科(Myctophidae)、鲱科(Clupeidae)、褶胸鱼科(Sternoptychidae)等,其中拟沙丁鱼相对丰度占比最高,其次是尾棘背灯鱼、大西洋大梭蜥鱼、日本背灯鱼(Notoscopelus japonicus)、长体标灯鱼(Symbolophorus californiensis)。此外还有相对丰度较低的细盗目鱼(Lestidiops ringens)、日本乌鲂(Brama japonica)、日本鲭(Scomber japonicus)、柔身纤钻光鱼(Sigmops gracilis)等物种。柔鱼的头足类饵料主要是日本爪乌贼、北方拟黵乌贼、萤乌贼等,其次是发光柔鱼(Eucleoteuthis luminosa)、班乌贼属(Onykia spp.)等。柔鱼广泛摄食浮游动物饵料,本研究共检测到桡足类、介形类、翼足类、水母类、栉水母类、磷虾类、毛颚类、端足类等8种浮游动物类群(
| 饵料物种Prey species | 饵料物种Prey species |
|---|---|
| 桡足类Copepod | 瘦乳点水蚤Pleuromamma gracilis |
| 鹰嘴水蚤科Aetideidae | 比氏乳点水蚤Pleuromamma piseki |
| 短尾真胖水蚤Euchirella curticauda | 哲水蚤科Calanidae |
| 大波刺水蚤Undeuchaeta major | 达氏筛哲水蚤Cosmocalanus darwinii |
| 丽哲水蚤科Calocalanidae | 基齿哲水蚤科Clausocalanidae |
| 短缩丽水蚤Calocalanus contractus | 弓角基齿哲水蚤Clausocalanus arcuicornis |
| 细长丽哲水蚤Calocalanus tenuis | 蓝基齿哲水蚤Clausocalanus lividus |
| 平头水蚤科Candaciidae | 尖基齿哲水蚤Clausocalanus parapergens |
| 双翼平头水蚤Candacia bipinnata | 纽氏伪哲水蚤Pseudocalanus newmani |
| 真哲水蚤科Eucalanidae | 拟哲水蚤科Paracalanidae |
| 加州真哲水蚤Eucalanus californicus | 小拟哲水蚤Paracalanus parvus |
| 长腹水蚤科Metridinidae | 拟哲水蚤属Paracalanus spp. |
| 腹突乳点水蚤Pleuromamma abdominalis | Paracalanus tropicus |
| 隆水蚤科Oncaeidae | Larsonia pterophylla |
| Oncaea scottodicarloi | 双生水母科Diphyidae |
| 长腹剑水蚤科Oithonidae | 锥体浅室水母Lensia conoidea |
| 拟长腹剑水蚤Oithona similis | 球水母科Sphaeronectidae |
| 磷虾类Euphausiacea | Sphaeronectes koellikeri |
| 磷虾科Euphausiidae | 棍手水母科Rhopalonematidae |
| 太平洋磷虾Euphausia pacifica | 宽膜棍手水母Rhopalonema velatum |
| 卷叶磷虾Euphausia recurva | 钟螅水母科Campanulariidae |
| 长额磷虾Euphausia diomedeae | Campanularia tulipifera |
| 细足磷虾属Nematoscelis spp. | 单囊美螅水母Clytia folleata |
| 瘦细足磷虾Nematoscelis gracilis | 口冠水母科Stomolophidae |
| Nematoscelis difficilis | 口冠水母属Stomolophus spp. |
| 端足类Amphipoda | 栉水母类Ctenophora |
| Hyperiidae | 蛾水母科Bolinopsidae |
太平洋拟长脚 Parathemisto pacifica | 蛾水母属Bolinopsis spp. |
| 饵料物种Prey species | 侧腕水母科Pleurobrachiidae |
| 长体标灯鱼Symbolophorus californiensis | 风球水母属Hormiphora spp. |
| 高体电灯鱼Electrona risso | 长瓣水母科Eurhamphaeidae |
| 褶胸鱼科Sternoptychidae | Deiopea spp. |
| 拉氏烛光鱼Polyipnus ruggeri | 翼足类Pteropoda |
| 褶胸鱼属Sternoptyx spp. | 螔螺科Limacinidae |
| 钻光鱼科Gonostomatidae | 螔螺Limacina helicina |
| 柔身纤钻光鱼Sigmops gracilis | 驼蝶螺科Cliidae |
| 鲱科Clupeidae | 翼菱蝶螺Clio cuspidata |
| 拟沙丁鱼Sardinops sagax | 鱼类Fish |
| 乌鲂科Bramidae | 灯笼鱼科Myctophidae |
| 日本乌鲂Brama japonica | 汤氏原灯笼鱼Protomyctophum thompsoni |
| 鲭科Scombridae | 白身臂灯鱼Stenobrachius leucopsarus |
| 日本鲭Scomber japonicus | 饵料物种Prey species |
蜥鱼科Paralepididae | 大西洋大梭蜥鱼Magnisudis atlantica |
| 细盗目鱼Lestidiops ringens | 头足类Cephalopoda |
| 介形类Ostracoda | 武装乌贼科Enoploteuthidae |
| 吸海萤科Halocyprididae | 萤乌贼Watasenia scintillans |
| 尖额齿浮萤Conchoecilla daphnoides | 发光柔鱼Eucleoteuthis luminosa |
| 双浮萤属Disconchoecia spp. | 黵乌贼科Gonatidae |
| 大浮萤Conchoecia magna | 北方拟黵乌贼Gonatopsis borealis |
| 尖后浮萤Metaconchoecia acuta | 柔鱼科Ommastrephidae |
| 长后浮萤Metaconchoecia longiseta | 柔鱼Ommastrephes bartramii |
| 哈氏直浮萤Orthoconchoecia haddoni | 爪乌贼科Onychoteuthidae |
| 毛颚类Chaetognatha | 日本爪乌贼Onychoteuthis borealijaponica |
| 箭虫科Sagittidae | 班乌贼属Onykia spp. |
| 琴型伪箭虫Pseudosagitta lyra | 其他Others |
| 水母类Medusa | 三段海鞘科Polyclinidae |
| 面具水母科Pandeidae | 褶胃海鞘属Aplidium spp. |

图4 各饵料类群的相对丰度占比
Fig.4 Proportion of relative abundance of each prey group
研究发现,160~219 mm胴长组柔鱼主要摄食浮游动物和鱼类(

图5 不同胴长组各种饵料平均相对丰度占比
Fig.5 Mean relative abundance ratio of various preys items in different mantle length groups

图6 饵料物种在不同胴长组间的分布比例(纲水平上)
Fig.6 Distribution ratio of prey species among different groups (on Class level)
实心圆代表纲水平下的物种,圆的大小代表物种的平均相对丰度。
The solid circles represent the species of Class level, the size of the circles represents the average relative abundance of the species.
选用相似水平为97%的OTU分析统计,得到饵料物种分属80个OTU。为了直观体现不同发育状态柔鱼胃含物中饵料物种丰富程度的差异和交叉特

图7 不同胴长组中OTUs数量分布情况(韦恩图)
Fig.7 Distribution of OTUs in mantle length groups (Venn diagram)
研究表明西北太平洋柔鱼主要摄食鱼类、头足类及多种浮游动物。根据相对丰度占比和出现频率判断,柔鱼表现出对拟沙丁鱼和灯笼鱼科鱼类显著的摄食选择,拟沙丁鱼的相对丰度占比(24.90%)和出现频率(73.33%)最高,灯笼鱼科鱼类的出现频率为53.33%。此外,日本爪乌贼、北方拟黵乌贼、萤乌贼和磷虾类也是柔鱼的主要摄食对象。这与WATANABE
本研究结果显示,磷虾类饵料总相对丰度占比(6.24%)在浮游动物饵料中最大(
本研究发现浮游动物饵料主要出现在160~219 mm胴长组柔鱼中,340~399 mm、400~459 mm胴长组柔鱼摄食鱼类和头足类的比例大于160~219 mm胴长组柔鱼,这与以往的研
在本研究中,胴长大于400 mm的柔鱼胃含物中存在多种浮游动物饵料,这与IVANOVIC
高通量测序技术的应用使食性分析完成了从粗略的定性化描述到半定量化表达的关键突
本研究通过高通量测序对柔鱼食性进行初步分析,发现柔鱼主要摄食头足类、鱼类和多种类浮游动物。且不同发育状态柔鱼的摄食偏好不同,小型个体柔鱼摄食浮游动物较多,大型个体柔鱼饵料中头足类和鱼类的比例增加。运用高通量测序技术共检测筛选得到柔鱼饵料物种65种,表明柔鱼摄食范围广泛。柔鱼是机会主义摄食者,所选择摄取的饵料与海区资源组成和丰度有
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