螺形龜甲輪蟲形態(tài)結(jié)構(gòu)對(duì)環(huán)境變化的響應(yīng)

劉 璐,梁迪文,楊宇峰,金 鼎,葉曉彤,王 慶*

螺形龜甲輪蟲形態(tài)結(jié)構(gòu)對(duì)環(huán)境變化的響應(yīng)

劉 璐1,2,梁迪文1,楊宇峰1,2,金 鼎1,葉曉彤1,王 慶1,2*

(1.暨南大學(xué)水生生物研究所,廣東 廣州 510632；2.南方海洋科學(xué)與工程廣東省實(shí)驗(yàn)室(珠海),廣東 珠海 519000)

以螺形龜甲輪蟲為研究對(duì)象,于2015年7月至2018年12月,選取廣東南澳島及湖南常德中營(yíng)養(yǎng)至中度富營(yíng)養(yǎng)水體共14個(gè)樣點(diǎn)進(jìn)行采樣,對(duì)螺形龜甲輪蟲進(jìn)行了形態(tài)特征測(cè)量分析.結(jié)果表明,水溫是螺形龜甲輪蟲形態(tài)變化最主要影響因子,且與背甲長(zhǎng)、背甲寬、棘刺長(zhǎng)度均呈顯著負(fù)相關(guān)(<0.01).不同緯度條件下螺形龜甲輪蟲形態(tài)參數(shù)差異顯著,常德地區(qū)螺形龜甲輪蟲個(gè)體顯著大于南澳地區(qū)(<0.05).螺形龜甲輪蟲形態(tài)存在顯著季節(jié)性變化,各形態(tài)參數(shù)隨季節(jié)波動(dòng)呈現(xiàn)夏秋、冬春分化模式.螺形龜甲輪蟲后棘刺長(zhǎng)隨水體營(yíng)養(yǎng)程度增加而減小(=159.4,<0.01),富營(yíng)養(yǎng)條件下后棘刺長(zhǎng)度占全長(zhǎng)的比例減小(=167.5,<0.01).研究結(jié)果表明,螺形龜甲輪蟲棘刺長(zhǎng)度可作為水質(zhì)生物監(jiān)測(cè)指標(biāo),并為研究全球氣候變暖提供重要參考.

輪蟲；表型可塑性；周期變形；生態(tài)指示；環(huán)境響應(yīng)

表型可塑性是生物應(yīng)對(duì)環(huán)境變化做出的相應(yīng)表型適應(yīng),以水生無脊椎動(dòng)物輪蟲尤為顯著.輪蟲是淡水浮游動(dòng)物群落的重要類群[1-2],也是微食物環(huán)的重要組成部分,對(duì)水環(huán)境變化敏感[3-4].輪蟲的形態(tài)結(jié)構(gòu)和生理機(jī)能等對(duì)水環(huán)境具有適應(yīng)性,這種適應(yīng)與生物有機(jī)體的表型可塑性相關(guān),主要表現(xiàn)為周期變形[5].輪蟲的周期變形是指種群內(nèi)出現(xiàn)的輪蟲形態(tài)隨時(shí)間推移而發(fā)生周期性變化,包括輪蟲體態(tài)大小、后棘刺長(zhǎng)度變化和有無后側(cè)棘刺等[6].周期變形使輪蟲具有多態(tài)性,可影響輪蟲生活史、種群動(dòng)態(tài)和生態(tài)相互作用,在生物學(xué)上具有重要意義[7].目前,國內(nèi)外已有一些關(guān)于輪蟲周期變形的研究,主要基于室內(nèi)受控條件,或面向單一淡水水體,探討單一因素對(duì)輪蟲表型可塑性的影響[8-9].

螺形龜甲輪蟲(Gosse, 1851)隸屬于單巢目、臂尾輪科、龜甲輪屬,廣泛分布于世界各地的淡水湖泊和池塘等水體[10-11],對(duì)不同溫度、鹽度、水體營(yíng)養(yǎng)狀態(tài)都具有較強(qiáng)耐受性,且在寡營(yíng)養(yǎng)型水體中易占據(jù)優(yōu)勢(shì)地位[12].螺形龜甲輪蟲具有較強(qiáng)的表型可塑性, 易于鑒定和測(cè)量,這使其成為輪蟲多態(tài)性進(jìn)化及對(duì)環(huán)境變化響應(yīng)研究的理想模型[13-14].研究表明,螺形龜甲輪蟲年平均后棘刺長(zhǎng)度與緯度之間存在弱線性關(guān)系,后棘刺平均長(zhǎng)度隨緯度的增加而增加,與溫度呈顯著相關(guān)[15].且螺形龜甲輪蟲后棘刺長(zhǎng)度易受到食物資源波動(dòng)的影響,能夠間接反映水體營(yíng)養(yǎng)狀態(tài)[6].

目前,自然水體中螺形龜甲輪蟲的多態(tài)性研究尚缺乏調(diào)查資料.本研究通過分析廣東南澳、湖南常德不同水體螺形龜甲輪蟲形態(tài)學(xué)特征(背甲長(zhǎng)、背甲寬、前棘刺長(zhǎng)、后棘刺長(zhǎng))與環(huán)境指標(biāo)間的相關(guān)關(guān)系,比較不同環(huán)境條件下、不同異質(zhì)性水體螺形龜甲輪蟲多態(tài)性差異,探討不同水體螺形龜甲輪蟲對(duì)環(huán)境變化的適應(yīng)特征,以期為區(qū)域環(huán)境變化和水質(zhì)評(píng)價(jià)提供可參考的形態(tài)指示指標(biāo).

1 材料與方法

1.1 研究區(qū)域

廣東南澳與湖南常德均處于亞熱帶季風(fēng)氣候區(qū).南澳縣位于粵東、南海與臺(tái)灣海峽交界海域,距離大陸6km,是廣東唯一的海島縣,島上屬于亞熱帶海洋性季風(fēng)氣候,年際溫度變化小,具有冬無嚴(yán)寒,夏無酷暑,雨量充足、溫暖濕潤(rùn)的特點(diǎn)[16-17].常德市位于湖南省西北部,屬于亞熱帶季風(fēng)氣候,四季分明,年際溫度變化較大,具有河網(wǎng)密布、水資源充沛、降雨不均的特點(diǎn).穿紫河位于常德江北城區(qū),東接柳葉湖,西連沅江,特有的河湖濕地生態(tài)系統(tǒng)造就了高異質(zhì)性的生境[18-19].

1.2 輪蟲的采集

圖1 采樣點(diǎn)分布

柳葉湖,L1～L8穿紫河,C1～C3南澳島水庫,S1～S3

于2015年7月～2018年12月,選取廣東南澳島果老山水庫(S1)、黃花山水庫(S2)、云澳水庫(S3)及湖南常德河湖連通水系(穿紫河C1-C3、柳葉湖L1-L8)共14個(gè)樣點(diǎn)作為調(diào)查對(duì)象(圖1),進(jìn)行季度采樣.輪蟲定量樣品采用20μm浮游生物網(wǎng)過濾濃縮2L水樣,置于50mL聚乙烯瓶,加入甲醛溶液至最終濃度為4%固定保存.輪蟲定性樣品采用40μm浮游生物網(wǎng)進(jìn)行垂直和水平方向拖取,加入甲醛溶液至最終濃度為4%固定保存.水溫、DO和pH值使用YSI-Plus多參數(shù)水質(zhì)分析儀現(xiàn)場(chǎng)測(cè)定.總氮(TN)、總磷(TP)按國家水質(zhì)標(biāo)準(zhǔn)GB3838-2002測(cè)定,Chl-a含量用丙酮分光光度法測(cè)定,水體透明度使用塞氏盤測(cè)定.

1.3 輪蟲形態(tài)指標(biāo)的測(cè)量

將固定好的樣品濃縮至10mL,混勻后隨機(jī)取1mL于1mL計(jì)數(shù)框,光學(xué)顯微鏡下隨機(jī)挑取成熟螺形龜甲輪蟲個(gè)體進(jìn)行顯微觀察及形態(tài)測(cè)定.形態(tài)測(cè)量指標(biāo)包括背甲長(zhǎng)(LL)、背甲寬(LW)、前棘刺長(zhǎng)(ASL)、后棘刺長(zhǎng)(PSL),全長(zhǎng)(TL)=LL+ASL+PSL(圖2),各樣點(diǎn)形態(tài)指標(biāo)至少測(cè)定30個(gè)輪蟲個(gè)體.

圖2 螺形龜甲輪蟲形態(tài)測(cè)量指標(biāo)

ASL: 前棘刺長(zhǎng), LL: 背甲長(zhǎng), PSL: 后棘刺長(zhǎng), LW: 背甲寬, TL: 全長(zhǎng)

1.4 數(shù)據(jù)分析與處理

用Excel軟件對(duì)數(shù)據(jù)進(jìn)行整理和歸類.通過Graphpad Prism 7.0對(duì)符合正態(tài)分布的數(shù)據(jù)采用非配對(duì)檢驗(yàn)(Unpairedtest)或單因素方差分析(One Way ANOVA),比較不同地區(qū)、不同季節(jié)、不同營(yíng)養(yǎng)狀態(tài)下體態(tài)參數(shù)的顯著性差異,不滿足方差齊性的數(shù)據(jù)進(jìn)行校正(Welch's correction),對(duì)不符合正態(tài)分布的數(shù)據(jù)進(jìn)行Kruskal-Wallis test分析.螺形龜甲輪蟲形態(tài)指標(biāo)與環(huán)境因子關(guān)系使用SPSS Statistics 22進(jìn)行Pearson相關(guān)性分析.

采用修正的營(yíng)養(yǎng)狀態(tài)指數(shù)(TSIM)評(píng)價(jià)水體營(yíng)養(yǎng)狀態(tài)[20].分別選取Chl-a、SD、TP作為評(píng)價(jià)水體富營(yíng)養(yǎng)化的基準(zhǔn)參數(shù),計(jì)算公式如下:

參照營(yíng)養(yǎng)狀態(tài)分級(jí)標(biāo)準(zhǔn)進(jìn)行營(yíng)養(yǎng)程度劃分[21]. TSI(Σ)<30,為貧營(yíng)養(yǎng); 30￡TSI(Σ)￡50為中營(yíng)養(yǎng); 50< TSI(Σ)￡60為輕度富營(yíng)養(yǎng)6070,為重度富營(yíng)養(yǎng).

2 結(jié)果與分析

2.1 水體理化環(huán)境特征

湖南常德和廣東南澳地區(qū)采樣水體各理化因子隨季度呈現(xiàn)較大變化(表1).不同采樣點(diǎn)水溫為8.4～33.13℃,常德地區(qū)夏季水溫高于冬季南澳地區(qū)秋季水溫最高,其次是夏季,春季最低兩地區(qū)冬季水溫相差大.透明度最高值均出現(xiàn)在冬季,常德為(86.26±38.40)cm,南澳為(166.67±49.22)cm,各季節(jié)南澳水庫站點(diǎn)平均透明度均大于常德水系.TN、TP最高值分別出現(xiàn)在秋季(9.88±1.78)mg/L和春季(0.27±0.09)mg/L的常德水系.pH值在7.66～8.22之間,各類型水體偏堿性,但未見有明顯季節(jié)變化.常德地區(qū)水溫、TN、DO呈夏秋-冬春分化,南澳地區(qū)水溫、透明度、TN、Chl-a、TSI呈冬春夏-秋分化.

表1 常德及南澳水體環(huán)境因子參數(shù)平均值

注:*表示南澳DO值未進(jìn)行測(cè)量,以NA表示無數(shù)據(jù).

2.2 螺形龜甲輪蟲體態(tài)參數(shù)的時(shí)空變化

圖3 螺形龜甲輪蟲背甲長(zhǎng)(A)、背甲寬(B)、前棘刺長(zhǎng)(C)、后棘刺長(zhǎng)(D)季節(jié)變化(Kruskal-Wallis test)

圖4 常德和南澳螺形龜甲輪蟲平均背甲長(zhǎng)LL、背甲寬LW、前棘刺長(zhǎng)ASL、后棘刺長(zhǎng)PSL的比較(Mann-Whitney test)

共收集螺形龜甲輪蟲828個(gè),其中常德地區(qū)466個(gè),南澳地區(qū)362個(gè).調(diào)查顯示,螺形龜甲輪蟲各體態(tài)參數(shù)隨季節(jié)波動(dòng)呈現(xiàn)夏秋、冬春分化模式(圖3).秋季背甲長(zhǎng)(79.33±5.08)μm、前棘刺長(zhǎng)(19.63± 3.14)μm、后棘刺長(zhǎng)(33.77±6.08)μm顯著低于其他季節(jié)(<0.05).背甲長(zhǎng)、后棘刺長(zhǎng)呈現(xiàn)秋季<夏季<冬季<春季的趨勢(shì).

南澳地區(qū)螺形龜甲輪蟲平均背甲長(zhǎng)(82.51± 5.84)μm、背甲寬(50.30±5.09)μm和前棘刺長(zhǎng)(19.79±3.99)μm均顯著小于常德地區(qū)輪蟲(<0.05,圖4),而后棘刺長(zhǎng)(42.03±7.52)μm顯著大于常德地區(qū)(32.29 ±7.41)μm輪蟲(<0.05).

圖5 常德和南澳螺形龜甲輪蟲不同季節(jié)背甲長(zhǎng)、背甲寬、前棘刺長(zhǎng)、后棘刺長(zhǎng)大小頻度分布

常德螺形龜甲輪蟲體態(tài)參數(shù)頻度分布顯示,相對(duì)于水溫較低的冬春季節(jié),夏秋季螺形龜甲輪蟲背甲長(zhǎng)、背甲寬及后棘刺長(zhǎng)較小,前棘刺長(zhǎng)分布主要集中于20μm冬春季出現(xiàn)背甲長(zhǎng)度超過100μm、后棘刺長(zhǎng)超過50μm的個(gè)體,即冬春季節(jié)螺形龜甲輪蟲的體型更大,棘刺更長(zhǎng)(圖5a).南澳螺形龜甲輪蟲體態(tài)參數(shù)頻度分布顯示,相較于秋冬季,春夏季節(jié)螺形龜甲輪蟲背甲長(zhǎng)、背甲寬及后棘刺較長(zhǎng),在頻度圖中呈右偏分布,春季各體態(tài)參數(shù)較其他季節(jié)分布集中且高于其它季節(jié)(圖5b).

2.3 螺形龜甲輪蟲體態(tài)參數(shù)對(duì)環(huán)境因子的響應(yīng)

相關(guān)分析顯示,水溫與背甲長(zhǎng)、背甲寬、前棘刺長(zhǎng)和后棘刺長(zhǎng)均呈極顯著負(fù)相關(guān)(<0.01).隨著水溫升高,輪蟲個(gè)體體型變小、棘刺變短(表2).透明度與背甲寬呈顯著負(fù)相關(guān)(=-0.377,<0.01),與后棘刺呈顯著正相關(guān)(=0.581,<0.01).背甲寬與Chl-a及TN、TP均呈極顯著正相關(guān),而后棘刺隨Chl-a及TN、TP的升高而減小(<0.01).DO與各體態(tài)參數(shù)均呈極顯著正相關(guān)(<0.01).pH值與背甲長(zhǎng)、背甲寬和前棘刺長(zhǎng)呈極顯著負(fù)相關(guān)(<0.01),TSI與背甲寬呈極顯著正相關(guān),與棘刺長(zhǎng)度呈不同程度負(fù)相關(guān)(<0.05),在營(yíng)養(yǎng)條件越豐富、溫度越高的水體中,螺形龜甲輪蟲的后棘刺長(zhǎng)越短.結(jié)果表明,環(huán)境因子的變化對(duì)后棘刺長(zhǎng)具有顯著影響.

表2 螺形龜甲輪蟲背甲長(zhǎng)、背甲寬、前棘刺長(zhǎng)、后棘刺長(zhǎng)與環(huán)境因子的Pearson相關(guān)性分析

注:* 表示< 0.05**表示< 0.01

2.4 螺形龜甲輪蟲體態(tài)參數(shù)與水體營(yíng)養(yǎng)狀態(tài)的關(guān)系

螺形龜甲輪蟲后棘刺長(zhǎng)在中營(yíng)養(yǎng)水體中顯著高于富營(yíng)養(yǎng)水體(圖6).中營(yíng)養(yǎng)狀態(tài)水體螺形龜甲輪蟲平均后棘刺長(zhǎng)為(39.49±8.72)μm,顯著高于輕度富營(yíng)養(yǎng)(33.63±7.10)μm、中度富營(yíng)養(yǎng)(31.53±9.46)μm和重度富營(yíng)養(yǎng)(32.63±7.46)μm狀態(tài)水體輪蟲(<0.01).輕度富營(yíng)養(yǎng)狀態(tài)水體螺形龜甲輪蟲個(gè)體平均體長(zhǎng)(79.21±5.88)μm、體寬(52.55±5.80)μm顯著低于其他營(yíng)養(yǎng)水平水體(<0.01,圖6).

后棘刺長(zhǎng)與水體營(yíng)養(yǎng)狀態(tài)相關(guān)性分析表明,螺形龜甲輪蟲后棘刺長(zhǎng)隨水體營(yíng)養(yǎng)狀態(tài)增加而降低(=159.4,<0.01),同時(shí)背甲長(zhǎng)度無明顯變化(=67.5,<0.01圖7),形態(tài)特征表現(xiàn)為營(yíng)養(yǎng)程度越高后棘刺越短.

圖6 不同水體營(yíng)養(yǎng)狀態(tài)條件下螺形龜甲輪蟲背甲長(zhǎng)、背甲寬、前棘刺長(zhǎng)、后棘刺長(zhǎng)均值的比較(Kruskal-Wallis test)

圖7 螺形龜甲輪蟲后棘刺長(zhǎng)PSL、PSL/TL與水體營(yíng)養(yǎng)狀態(tài)線性回歸分析

圖8 螺形龜甲輪蟲背甲長(zhǎng)LL、背甲寬LW、前棘刺長(zhǎng)ASL、后棘刺長(zhǎng)PSL及環(huán)境因子的PCA主成分分析圖(a);不同營(yíng)養(yǎng)狀態(tài)螺形龜甲輪蟲后棘刺長(zhǎng)PSL頻率分布直方圖 (b)

PCA結(jié)果顯示,后棘刺長(zhǎng)度不受背甲長(zhǎng)度的影響(圖8).輕度富營(yíng)養(yǎng)條件下,螺形龜甲輪蟲后棘刺長(zhǎng)度主要分布于20～50μm區(qū)間,中度富營(yíng)養(yǎng)及重度富營(yíng)養(yǎng)狀態(tài)下,后棘刺超過40μm的螺形龜甲輪蟲個(gè)體幾乎未出現(xiàn).后棘刺長(zhǎng)度為60μm以上個(gè)體僅在中營(yíng)養(yǎng)水體中出現(xiàn)(圖8).

3 討論

研究表明,影響輪蟲周期變形的非生物因素主要有水溫、氮磷含量、Chl-a、透明度、pH值等[22-23],生物因素如食物濃度、個(gè)體競(jìng)爭(zhēng)[6]、種間捕食關(guān)系[24-25]、捕食者組成[26]等因素決定的上、下行效應(yīng)也顯著影響輪蟲的形態(tài)結(jié)構(gòu).Chl-a在一定程度上能夠反映食物資源豐度,食物濃度是影響螺形龜甲輪蟲體長(zhǎng)變化的重要因素[12,24].在低溫和低食物濃度條件下,輪蟲將能量主要用于體態(tài)和棘刺的生長(zhǎng),以提高競(jìng)爭(zhēng)能力、捕食防御能力和生存機(jī)會(huì)[27].

3.1 水溫顯著影響亞熱帶湖庫中螺形龜甲輪蟲的周期變形

水溫是影響輪蟲形態(tài)變化的關(guān)鍵環(huán)境因子之一.螺形龜甲輪蟲后棘刺平均長(zhǎng)度及其變化幅度(SD)隨緯度增加而增加,溫度顯著影響后棘刺長(zhǎng)度變化,且隨緯度增加輪蟲熱耐受性增加[15].常德和南澳水溫變化顯著影響螺形龜甲輪蟲的背甲長(zhǎng)、背甲寬、前棘刺長(zhǎng)、后棘刺長(zhǎng)的季節(jié)變化,這種季節(jié)性變化可能受到熱耐受性和表型可塑性大小的驅(qū)動(dòng).基于單一水體的調(diào)查表明,螺形龜甲輪蟲的體態(tài)大小主要受水溫影響[8,28].室內(nèi)實(shí)驗(yàn)表明,個(gè)體大小及棘刺長(zhǎng)度隨水溫的升高而減小,且在低溫條件下,螺形龜甲輪蟲將更多的能量用于生長(zhǎng)發(fā)育[23].水溫是影響輪蟲壽命的關(guān)鍵環(huán)境因素,在較低水溫條件下,輪蟲生長(zhǎng)速度慢,使得同一時(shí)期存在較多大型個(gè)體[6,29]低溫顯著提高輪蟲存活率,且當(dāng)?shù)蜏乇┞栋l(fā)生在生命周期的早期時(shí),低溫所致壽命延長(zhǎng)效應(yīng)最大,更長(zhǎng)的生存生長(zhǎng)時(shí)間會(huì)產(chǎn)生更大的輪蟲個(gè)體[5,30].敲除輪蟲特定基因可以完全消除低溫壽命延長(zhǎng)效應(yīng),可能原因是由溫度變化引起的遺傳調(diào)節(jié)在溫度介導(dǎo)的壽命延長(zhǎng)過程中比被動(dòng)熱力學(xué)效應(yīng)作用更大[30].水溫升高加速輪蟲的生長(zhǎng),產(chǎn)生具有較短棘刺的小型個(gè)體[27].

目前大多學(xué)者認(rèn)可溫度-大小規(guī)則(temperature-size rule).該規(guī)則指物種體態(tài)大小對(duì)溫度的表型可塑性適應(yīng),體態(tài)大小會(huì)隨環(huán)境溫度升高而減小[31-33].常德和南澳地區(qū)螺形龜甲輪蟲體態(tài)參數(shù)存在顯著性差異(<0.05,圖4圖5),水溫是螺形龜甲輪蟲形態(tài)變化最主要的影響因子.南澳、常德位于不同緯度地區(qū),緯度條件影響水溫的季節(jié)變化,常德水溫波動(dòng)范圍大,低溫區(qū)間明顯,導(dǎo)致螺形龜甲輪蟲個(gè)體體型顯著大于南澳個(gè)體.

3.2 水體營(yíng)養(yǎng)狀態(tài)對(duì)螺形龜甲輪蟲周期變形的影響

調(diào)查發(fā)現(xiàn),水體由中營(yíng)養(yǎng)型過渡到超富營(yíng)養(yǎng)型,浮游動(dòng)物個(gè)體趨小[34].龜甲輪屬輪蟲是浮游動(dòng)物分布最廣的類群之一,以濾食形式攝食水體中懸浮顆粒物及浮游植物,具有較高的生態(tài)耐受性,在貧營(yíng)養(yǎng)、富營(yíng)養(yǎng)型水體中均可生存[35-36],其形態(tài)指標(biāo)隨水體營(yíng)養(yǎng)狀態(tài)改變表現(xiàn)出較大差異[28].水體營(yíng)養(yǎng)狀態(tài)反映浮游植物生存條件的優(yōu)劣,浮游植物等食物資源對(duì)螺形龜甲輪蟲個(gè)體大小影響密切.輪蟲體態(tài)的變化反映食物清除率的增加或減少,是對(duì)食物資源波動(dòng)的響應(yīng),往往較大個(gè)體具有更高的清除率,且在食物密度較高、捕食者密度較小的條件下,輪蟲傾向于將能量用于繁殖后代的生活史對(duì)策,體態(tài)增長(zhǎng)的同時(shí)將較少的能量用于棘刺生長(zhǎng)[6,25].因此,當(dāng)Chl-a含量升高時(shí),常德、南澳水體螺形龜甲輪蟲背甲寬增加而后棘刺長(zhǎng)度減小,一定范圍內(nèi),隨水體營(yíng)養(yǎng)狀態(tài)增加后棘刺長(zhǎng)及其占全長(zhǎng)的比例減小(圖6圖7),后棘刺長(zhǎng)度在60μm以上個(gè)體僅在中營(yíng)養(yǎng)水體中出現(xiàn)(圖7).

3.3 螺形龜甲輪蟲形態(tài)參數(shù)的潛在生態(tài)指示功能

浮游動(dòng)物的生態(tài)指示作用已被廣泛應(yīng)用于水質(zhì)評(píng)價(jià)[37-38].研究表明,浮游甲殼動(dòng)物的個(gè)體大小可作為湖泊生態(tài)狀況的良好指標(biāo).枝角類僧帽溞在貧營(yíng)養(yǎng)狀態(tài)下生長(zhǎng)良好,體長(zhǎng)、體寬隨營(yíng)養(yǎng)狀態(tài)的增加而減小[39].橈足類體長(zhǎng)隨溫度升高而減小,同時(shí)種群熱耐受性(thermal tolerance)增強(qiáng),相比于具有更大形態(tài)變異度的高緯度地區(qū)種群,低緯度地區(qū)種群熱耐受性較低,易于受到氣候變暖的影響[40].熱耐受性與表型可塑性強(qiáng)度的負(fù)相關(guān)關(guān)系可維持短壽命生物多態(tài)性平衡[41].

由于生命周期短,對(duì)環(huán)境條件變化反應(yīng)迅速,輪蟲的生態(tài)指示功能受到廣泛關(guān)注.輪蟲種類組成[42]、總豐度[43]等被廣泛應(yīng)用于水環(huán)境評(píng)估,但傳統(tǒng)指示指標(biāo)都存在局限性.輪蟲營(yíng)養(yǎng)狀態(tài)綜合指數(shù)(TSIROT)可作為溫帶湖泊營(yíng)養(yǎng)狀態(tài)的評(píng)估指標(biāo),但在高濃度銨的水體中指示結(jié)果可信度低,且該指數(shù)不適用于半咸水水體水質(zhì)評(píng)價(jià)[44-45].相對(duì)于物種組成,輪蟲豐度能夠更客觀地反映亞熱帶淺水湖泊營(yíng)養(yǎng)狀態(tài)[43].龜甲輪蟲指數(shù)(KIN)僅作為河口營(yíng)養(yǎng)狀態(tài)的有效指示指標(biāo)[46].

輪蟲臨界食物濃度隨體態(tài)增加而增大,體態(tài)小的輪蟲在貧營(yíng)養(yǎng)型水體占優(yōu)勢(shì)[47-48].在受煤灰污染的水體中,體態(tài)小的輪蟲占據(jù)競(jìng)爭(zhēng)優(yōu)勢(shì),且卵大于正常生境[49].螺形龜甲輪蟲的生境偏好性導(dǎo)致其產(chǎn)生較大形態(tài)學(xué)差異,近年來受到研究者的廣泛關(guān)注.有研究將螺形龜甲輪蟲定為富營(yíng)養(yǎng)指示種[50],對(duì)廣東省水庫的調(diào)查發(fā)現(xiàn),螺形龜甲輪蟲是寡營(yíng)養(yǎng)型水庫中浮游輪蟲群落組成的絕對(duì)優(yōu)勢(shì)種[12].研究表明,螺形龜甲輪蟲后棘刺長(zhǎng)可反映溫度及食物濃度的變化[28].高溫下,短棘刺或無棘刺型螺形龜甲輪蟲占主導(dǎo)[27].后棘刺長(zhǎng)的螺形龜甲輪蟲個(gè)體僅出現(xiàn)在低溫環(huán)境[8].螺形龜甲輪蟲后棘刺的生長(zhǎng)主要受食物資源的控制,中營(yíng)養(yǎng)流域種群中后棘刺較長(zhǎng)[28].

4 結(jié)論

4.1 水溫是螺形龜甲輪蟲形態(tài)變化最主要影響因子,隨水溫升高螺形龜甲輪蟲體形趨小.不同緯度條件下螺形龜甲輪蟲形態(tài)參數(shù)差異顯著,常德地區(qū)螺形龜甲輪蟲個(gè)體顯著大于南澳地區(qū).螺形龜甲輪蟲形態(tài)存在顯著季節(jié)性變化,各體態(tài)參數(shù)隨季節(jié)波動(dòng)呈現(xiàn)夏秋、冬春分化模式.

4.2 本研究的湖庫水體均為中、富營(yíng)養(yǎng)狀態(tài),螺形龜甲輪蟲后棘刺長(zhǎng)與水體營(yíng)養(yǎng)狀態(tài)呈負(fù)相關(guān)關(guān)系,富營(yíng)養(yǎng)條件下后棘刺長(zhǎng)度占全長(zhǎng)的比例減小.

4.3 螺形龜甲輪蟲在不同營(yíng)養(yǎng)條件下的廣泛分布和其較高的表型可塑性使其具有成為生態(tài)指示物種的潛力,形態(tài)變化及棘刺長(zhǎng)度可反映湖庫水體營(yíng)養(yǎng)狀態(tài),對(duì)水溫的敏感性適應(yīng)可作為全球變暖區(qū)域響應(yīng)的指示指標(biāo).深入研究輪蟲形態(tài)受環(huán)境影響的變化規(guī)律,可為環(huán)境保護(hù)和治理提供科學(xué)依據(jù).

[1] Liang D, Wei N, Wang Q, et al. Influence of hydrological heterogeneity on rotifer community structure in three different water bodies in Shantou Area, Guangdong (China) [J]. Zoological Studies, 2019,58:23.

[2] Segers H, De Smet W H. Diversity and endemism in Rotifera: A review, andBory de St Vincent [J]. Biodiversity and Conservation, 2008,17(2):69-82.

[3] May L, Spears B M, Dudley B J, et al. The response of the rotifer community in Loch Leven, UK, to changes associated with a 60% reduction in phosphorus inputs from the catchment [J]. International Review of Hydrobiology, 2014,99(1/2):65-71.

[4] Duggan I, Green J, Shiel R. Distribution of rotifers in North Island, New Zealand, and their potential use as bioindicators of lake trophic state [J]. Hydrobiologia, 2001,446:155-164.

[5] 葛雅麗,席貽龍,馬 杰,等.溫度對(duì)矩形龜甲輪蟲生命表統(tǒng)計(jì)學(xué)參數(shù)和形態(tài)特征的影響 [J]. 應(yīng)用生態(tài)學(xué)報(bào), 2011,22(5):1287-1294.

Ge Y L,Xi YL, Ma J, et al. Effects of temperature onlife table demography and morphometric characteristics [J]. Chinese Journal of Applied Ecology, 2011,22(5):1287-1294.

[6] Diéguez M, Modenutti B, Queimali?os C. Influence of abiotic and biotic factors on morphological variation of(Gosse) in a small Andean lake [J]. Hydrobiologia, 1998:387-388.

[7] Gilbert J J. No-genetic polymorphisms in rotifers: environmental and endogenous controls, development, and features for predictable or unpredictable environments [J]. Biological Reviews, 2017,92(2):964- 992.

[8] Green J. Morphological variation of(Gosse) in a backwater of the River Thames [J]. Hydrobiologia, 2005,546(1):189- 196.

[9] Gilbert J J. Predator-specific inducible defenses in the rotifer[J]. Freshwater Biology, 2009,54(9):1933-1946.

[10] Green J.(Gosse) in Africa [J]. Hydrobiologia, 1987,147:3-8.

[11] Segers H. Annotated checklist of the rotifers (Phylum Rotifera), with notes on nomenclature, taxonomy and distribution [J]. Zootaxa, 2007, 1564(1):1-104.

[12] 林秋奇,趙帥營(yíng),韓博平.廣東省水庫輪蟲分布特征 [J]. 生態(tài)學(xué)報(bào), 2005,25(5):1123-1131.

Lin Q Q, Zhao S Y, Han B P. Rotifer distribution in tropical reservoirs, Guangdong Province, China [J].Acta Ecologica Sinica, 2005,25(5): 1123-1131.

[13] Cieplinski A, Weisse T, Obertegger U. High diversity in(Rotifera, Monogononta): morphological and genetic evidence [J]. Hydrobiologia, 2017,796(1):145-159.

[14] Ramos-Rodríguez E, Moreno E, Conde-Porcuna J M. Intraspecific variation in sensitivity to food availability and temperature-induced phenotypic plasticity in the rotifer[J]. Journal of Experimental Biology, 2020,223(7).

[15] Zhang H, Br?nmark C, Hansson L A. Predator ontogeny affects expression of inducible defense morphology in rotifers [J]. Ecology, 2017,98(10):2499-2505.

[16] 喬永民,顧繼光,楊 揚(yáng),等.南澳島海域表層沉積物重金屬分布、富集與污染評(píng)價(jià) [J]. 熱帶海洋學(xué)報(bào), 2010,29(1):77-84.

Qiao Y M, Gu J G, Yang Y, et al. The distribution, enrichment and pollution assessment of heavy metals in surface sediments of sea areas around the Nanao Island [J]. Journal of Tropical Oceanography, 2010, 29(1):77-84.

[17] 任玉正,柯志新,譚燁輝,等.廣東省南澳島東部海域浮游動(dòng)物群落結(jié)構(gòu)及其影響因素 [J]. 熱帶海洋學(xué)報(bào), 2020,39(2):65-76.

Ren Y Z, Ke Z X, Tan Y H, et al. Community structure of zooplankton and its influencing factors in the eastern waters of Nan’ao Island, Guangdong [J]. Journal of Tropical Oceanography, 2020,39(2):65-76.

[18] 袁 皓.常德市穿紫河水環(huán)境質(zhì)量監(jiān)測(cè)與評(píng)價(jià) [J]. 資源節(jié)約與環(huán)保, 2013,(12):161-161.

Yuan H. Environmental quality monitoring and evaluation of Chuanzi River in Changde city [J]. Resource Conservation and Environmental Protection, 2013,(12):161.

[19] 葉曉彤,梁迪文,王 慶,等.洞庭湖流域常德柳葉湖及其鄰近水體輪蟲群落結(jié)構(gòu)變化及其對(duì)環(huán)境因子的響應(yīng) [J]. 湖泊科學(xué), 2020, 32(4):1126-1139.

Ye X T, Liang D W, Wang Q, et al. Variation of the rotifer community structure and its responses to environmental factors in Lake Liuye and its adjacent waters in Changde City, Lake Dongting Basin [J]. Journal of Lake Sciences, 2020,32(4):1126-1139.

[20] 楊梅玲,胡忠軍,劉其根,等.利用綜合營(yíng)養(yǎng)狀態(tài)指數(shù)和修正的營(yíng)養(yǎng)狀態(tài)指數(shù)評(píng)價(jià)千島湖水質(zhì)變化(2007年-2011年) [J]. 上海海洋大學(xué)學(xué)報(bào), 2013,22(2):240-245.

Yang M L, Hu Z J, Liu Q G, et al. Evaluation of water quality by two trophic state indices in Lake Qiandaohu during 2007～2011 [J]. Journal of Shanghai Ocean University, 2013,22(2):240-245.

[21] 鄭丙輝,張 遠(yuǎn),富 國,等.三峽水庫營(yíng)養(yǎng)狀態(tài)評(píng)價(jià)標(biāo)準(zhǔn)研究 [J]. 環(huán)境科學(xué)學(xué)報(bào), 2006,26(6):1022-1030.

Zheng B H, Zhang Y, Fu G, et al. On the assessment standards for nutrition status in the Three Gorge Reservoir [J]. Acta Scientiae Circumstantiae, 2006,26(6):1022-1030.

[22] West-Eberhard M J. Developmental plasticity and evolution [M]. Oxford: Oxford University Press, 2003.

[23] Ge Y, Xi Y, Ma J, et al. Factors influencing morphological characteristics ofin Lake Tingtang [J]. Proceedings of the National Academy of Sciences, India Section B: Biological Sciences, 2018,88(1):421-428.

[24] Stemberger R S, Gilbert J J. Spine development in the rotifer: induction by cyclopoid copepods and[J]. Freshwater Biology, 1984,14(6):639-647.

[25] 殷旭旺,趙 文,畢進(jìn)紅,等.卜氏晶囊輪蟲對(duì)4種臂尾輪蟲形態(tài)可塑性的影響 [J]. 大連水產(chǎn)學(xué)院學(xué)報(bào), 2009,24(6):494-496.

Yin X W, Zhao W, Bi J H, et al. Rotiferinduced morphological plasticity in fourrotifer species [J]. Journal of Dalian Fisheries University. 2009,24(6):494-496.

[26] Green J. Morphological variation of(Gosse) in Myanmar (Burma) in relation to zooplankton community structure [J]., 2007,593(1):5-12.

[27] Biela?ska-Grajner I. Influence of temperature on morphological variation in populations of(Gosse) in Rybnik Reservoir [J]., 1995,313-314(1).

[28] Hillbricht-Ilkowska A. Morphological variation of(Gosse) in Lake Biwa, Japan [J]., 1983, 104(1).

[29] Ruttner-Kolisko A. The vertical distribution of plankton rotifers in a small alpine lake with a sharp oxygen depletion () With 7 figures in the text [J]. Internationale Vereinigung für Theoretische und Angewandte Limnologie: Verhandlungen, 1975, 19(2):1286-1294.

[30] Johnston R K, Snell T W. Moderately lower temperatures greatly extend the lifespan of(Rotifera): Thermodynamics or gene regulation? [J]. Experimental gerontology, 2016,78:12-22.

[31] Tabi A, Garnier A, Pennekamp F. Testing multiple drivers of the temperature-size rule with nonlinear temperature increase [J]. Functional Ecology, 2020,34(12):2503-2512.

[32] Forster J, Hirst A G. The temperature-size rule emerges from ontogenetic differences between growth and development rates [J]. Functional Ecology, 2012,26(2):483-492.

[33] 張 銳,朱藝峰,趙圣男,等.電廠增溫對(duì)中小型浮游動(dòng)物群落結(jié)構(gòu)的影響[J]. 中國環(huán)境科學(xué), 2020,40(2):839-850.

Zhang R, Zhu Y F, Zhao S N, et al. Effects of temperature increase on meso-and micro-zooplankton community in thermal discharge seawaters near Guohua Power Plant [J]. China Environmental Science, 2020,40(2):839-850.

[34] 黃祥飛,陳雪梅,伍焯田,等.武漢東湖浮游動(dòng)物數(shù)量和生物量變動(dòng)的研究 [J]. 水生生物學(xué)集刊, 1984,(3):345-358.

Huang X F, Chen X M, Wu Z T, et al. Studies on the changes in abundance and biomass of zooplankton in lake Donghu, Wuhan [J]. Acta Hydrobiologica Sinica, 1984,(3):345-358.

[35] 李共國,虞左明.千島湖輪蟲群落結(jié)構(gòu)及水質(zhì)生態(tài)學(xué)評(píng)價(jià) [J]. 湖泊科學(xué), 2003,(2):169-176.

Li G G, Yu Z M. Community structure of Rotifera and ecological assessment of water quality in Qiandao Lake [J]. Journal of Lake Sciences, 2003,(2):169-176.

[36] 郭 凱,趙 文,殷守仁,等.北京官廳水庫輪蟲群落結(jié)構(gòu)與水體富營(yíng)養(yǎng)化狀況 [J]. 湖泊科學(xué), 2010,22(2):256-264.

Guo K, Zhao W, Yin S R, et al. Relationship between eutrophication status of the water body and rotifer community structure in Guanting Reservoir, Beijing [J]. Journal of Lake Sciences, 2010,22(2):256-264.

[37] 李 玲,劉 玉,于 菲,等.廣州市谷河輪蟲群落結(jié)構(gòu)及水體黑臭水平 [J]. 中山大學(xué)學(xué)報(bào)(自然科學(xué)版), 2020,59(3):73-81.

Li L, Liu Y, Yu F, et al. Community structure of rotifera and black- odor level analysis in Gu River of Guangzhou city [J]. Acta Scientiarum Naturalium Universitatis Sunyatseni, 2020,59(3):73-81.

[38] 許木啟.從浮游動(dòng)物群落結(jié)構(gòu)與功能的變化看府河-白洋淀水體的自凈效果 [J]. 水生生物學(xué)報(bào), 1996,(3):212-220.

Xu M Q. Evaluation of self-purification efficiency of Fuhe stream- Baiyangdian Lake through zooplankton [J]. Acta Hydrobiologica Sinica. 1996,(3):212-220.

[39] Karpowicz M, S?ugocki ?, Koz?owska J, et al. Body size ofas an indicator of the ecological status of temperate lakes [J]. Ecological Indicators, 2020,117:106585.

[40] Sasaki M, Hedberg S, Richardson K, et al. Complex interactions between local adaptation, phenotypic plasticity and sex affect vulnerability to warming in a widespread marine copepod [J]. Royal Society open science, 2019,6(3).

[41] Sasaki M C, Dam H G. Genetic differentiation underlies seasonal variation in thermal tolerance, body size, and plasticity in a short‐lived copepod [J]. Ecology and evolution, 2020,10(21):12200-12210.

[42] May L, O’Hare M. Changes in rotifer species composition and abundance along a trophic gradient in Loch Lomond, Scotland, UK [J]., 2005,546(1).

[43] Wen X L, Xi Y L, Qian F P, et al. Comparative analysis of rotifer community structure in five subtropical shallow lakes in East China: role of physical and chemical conditions [J]., 2011, 661(1):303-316.

[44] Jurczak T, Wojtal-Frankiewicz A, Frankiewicz P, et al. Comprehensive approach to restoring urban recreational reservoirs. Part 2-Use of zooplankton as indicators for the ecological quality assessment [J]. Science of the Total Environment, 2019,653:1623-1640.

[45] Gutkowska A, Paturej E, Kowalska E. Rotifer trophic state indices as ecosystem indicators in brackish coastal waters [J]. Oceanologia, 2013,55(4):887-899.

[46] Gopko M, Telesh I V. Estuarine trophic state assessment: new plankton index based on morphology ofrotifers [J]. Estuarine, Coastal and Shelf Science, 2013,130:222-230.

[47] Stemberger R S, Gilbert J J. Body size, food concentration, and population growth in planktonic rotifers [J]. Ecology, 1985,66(4): 1151-1159.

[48] 趙帥營(yíng),韓博平.大型深水貧營(yíng)養(yǎng)水庫——新豐江水庫浮游動(dòng)物群落分析 [J]. 湖泊科學(xué), 2007,(3):305-314.

Zhao S Y, Han B P. Structural analysis of zooplankton community in a large deep oligotrophic reservoir- Xinfengjiang Reservoir, South China [J]. Journal of Lake Sciences,2007,(3):305-314.

[49] Ying H X, Xiao X Y, Gen Z, et al. Morphological differentiation ofcaused by predation and coal ash pollution [J]. Scientific Reports, 2017,7(1).

[50] M?emets A. Rotifers as indicators of lake types in Estonia [J]., 1983,104(1):357-361.

The responses of morphological variation ofto environmental changes.

LIU Lu1,2, LIANG Di-wen1, YANG Yu-feng1,2, JIN Ding1, YE Xiao-tong1, WANG Qing1,2*

(1.Institute of Hydrobiology, Jinan University, Guangzhou 510632, China；2.Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai 519000, China)., 2021,41(11)：5326～5333

In this study, to measure and analyze the morphometric parameters of., 14sites were selected in Nan’ao Island, Guangdong Province and Changde city, Hunan Province with different water trophic statuses from mesotrophic to moderate-eutrophic. Samples were collected quarterly from July 2015 to December 2018. The results showed that the water temperature was the most important factor affecting the morphological changes of.and had a significant negative correlation with lorica length, lorica width and spine length (<0.01). There were significant differences in morphometric parameters of.in different latitudes, with individuals from Changde area being significantly larger than those in Nan'ao (<0.05). There were also significant seasonal changes in the morphology of., and the morphological parameters of this species showed different pattern between summer-autumn and winter-spring. The length of the posterior spines of.decreased with the increased of nutrient loading (=159.4,<0.01), and the ratio of the length of the posterior spines to the total length of rotifer decreased under eutrophic condition (=167.5,<0.01). The results showed that the spine length of.can be used as a biological monitoring index of water quality, and provided an important reference for the study of global warming.

rotifer；phenotypic plasticity；cyclomorphosis；ecological indicator；environmental response

X17

A

1000-6923(2021)11-5326-08

劉 璐(1998-),女,湖南省長(zhǎng)沙人,暨南大學(xué)碩士研究生,主要從事輪蟲生態(tài)學(xué)研究.

2021-03-04

國家自然科學(xué)基金資助項(xiàng)目(41673080);南方海洋科學(xué)與工程廣東省實(shí)驗(yàn)室(珠海)課題(311021006);廣東省自然科學(xué)基金資助項(xiàng)目(2021A1515010814)

* 責(zé)任作者, 副研究員, wq2010@jnu.edu.cn