陸洪良, 耿 軍, 徐 衛(wèi), 平 駿, 張永普,*

1 杭州師范大學(xué)生命與環(huán)境科學(xué)學(xué)院, 杭州 310036 2 溫州大學(xué)生命與環(huán)境科學(xué)學(xué)院, 溫州 325035

東方蠑螈幼體熱耐受性和游泳表現(xiàn)的熱馴化響應(yīng)

陸洪良1, 耿 軍1, 徐 衛(wèi)1, 平 駿2, 張永普2,*

1 杭州師范大學(xué)生命與環(huán)境科學(xué)學(xué)院, 杭州 310036 2 溫州大學(xué)生命與環(huán)境科學(xué)學(xué)院, 溫州 325035

特定物種的熱馴化能力決定著其是否能成功耐受環(huán)境溫度的改變,在應(yīng)對(duì)未來(lái)氣候變暖的趨勢(shì)中扮演重要角色。為評(píng)估有尾類兩棲動(dòng)物的熱馴化反應(yīng),在3個(gè)恒定水溫(15、20℃和25℃)中馴化東方蠑螈(Cynopsorientalis)幼體4周,測(cè)定馴化后幼體在不同測(cè)試溫度下的運(yùn)動(dòng)(游泳)表現(xiàn)、臨界低溫(CTMin)與臨界高溫(CTMax)。結(jié)果顯示：馴化與測(cè)試溫度均顯著影響蠑螈的游泳速度；馴化溫度亦影響蠑螈的CTMin和CTMax,但不影響可耐受溫度范圍(TRR)。馴化與測(cè)試溫度的交互作用對(duì)蠑螈泳速的影響顯著,表明馴化溫度可改變其游泳表現(xiàn)的熱敏感性。經(jīng)某一溫度馴化后蠑螈泳速似乎在相同測(cè)試溫度下表現(xiàn)最好,該結(jié)果可能支持馴化有益假說(shuō)。CTMin和CTMax隨馴化溫度的升高而增加,表明：低溫馴化可提高動(dòng)物抗低溫能力,而高溫馴化提高其抗高溫能力。兩棲類動(dòng)物熱耐受性與運(yùn)動(dòng)表現(xiàn)熱馴化反應(yīng)的種間變異可能與棲息地?zé)岘h(huán)境的差異有關(guān)。

東方蠑螈；熱馴化；熱耐受能力；運(yùn)動(dòng)表現(xiàn)；馴化有益假說(shuō)

在眾多影響外溫動(dòng)物生理與行為表現(xiàn)的環(huán)境因子中,溫度效應(yīng)無(wú)疑是最明顯的[1-2]。環(huán)境溫度通過(guò)改變外溫動(dòng)物的體溫可影響其生理與行為表現(xiàn)(例如,運(yùn)動(dòng)、攝食、同化、生長(zhǎng)、免疫功能等)[2]。任何一種變溫動(dòng)物對(duì)外界環(huán)境溫度的耐受能力有限。較長(zhǎng)時(shí)間在過(guò)高或過(guò)低的熱環(huán)境中暴露會(huì)使外溫動(dòng)物損傷甚至死亡[2-3]。使動(dòng)物無(wú)法逃離致其死亡狀態(tài)的極端溫度上下限被分別定義為臨界高溫(CTMax)和臨界低溫 (CTMin)[2, 4]。在可耐受溫度范圍內(nèi),任何生理與行為表現(xiàn)隨體溫變化的趨勢(shì)可用熱功能曲線表示：體溫從臨界低溫上升到最適水平,功能表現(xiàn)逐漸增加；從最適水平上升到臨界高溫,功能表現(xiàn)陡然下降[1]。外溫動(dòng)物的熱耐受能力和功能表現(xiàn)的熱敏感性存在顯著的種內(nèi)和種間差異,這種差異與其分布范圍、擴(kuò)散能力等方面相關(guān)聯(lián)。例如,分布范圍廣的種類通常熱耐受范圍相對(duì)較大、熱敏感性較低[2-3]。事實(shí)上,外溫動(dòng)物的熱耐受能力和功能表現(xiàn)的熱敏感性可以看成是長(zhǎng)期適應(yīng)熱環(huán)境變異所做出的反應(yīng)。當(dāng)遷徙到新生境中,動(dòng)物為適應(yīng)當(dāng)?shù)責(zé)岘h(huán)境使某些生理表現(xiàn)(例如,肌肉收縮特性、酶代謝活性)逐漸發(fā)生變化,由此熱耐受能力和功能表現(xiàn)的熱敏感性也隨之發(fā)生偏移。這一生理變化過(guò)程也被稱為熱馴化[5]。

外溫動(dòng)物的熱馴化反應(yīng)決定其應(yīng)對(duì)周圍環(huán)境熱變異(包括未來(lái)氣候變化等)的能力[6-8]。熱馴化會(huì)改變變溫動(dòng)物的熱耐受性,但其影響在不同種類中存在差異[9-12]。例如,有些種類在較低溫度下馴化具有較大熱耐受范圍[13-14],而一些種類則在中等溫度下馴化具有較大的熱耐受范圍[12,15-16]。動(dòng)物的運(yùn)動(dòng)表現(xiàn)與其適合度緊密關(guān)聯(lián),在進(jìn)化生物學(xué)研究中是被測(cè)量最為頻繁的一個(gè)特征[17-18]。熱馴化同樣會(huì)影響外溫動(dòng)物的運(yùn)動(dòng)表現(xiàn),并存在顯著的種間差異[19-20]。例如,許多魚(yú)類和蛙類的蝌蚪在不同水溫下馴化,游泳速度的熱敏感性發(fā)生顯著變化,但是這種效應(yīng)在發(fā)生變態(tài)后的蛙類中并不明顯[20-23]。已有多種假說(shuō)被提出來(lái)用于解釋外溫動(dòng)物運(yùn)動(dòng)表現(xiàn)的熱馴化反應(yīng)。例如,馴化有益假說(shuō)認(rèn)為,經(jīng)特定溫度馴化的動(dòng)物在該溫度條件下會(huì)增強(qiáng)其功能表現(xiàn)或適合度[18,24]。雖然該假說(shuō)獲得了一些實(shí)驗(yàn)數(shù)據(jù)的支持,但其普遍適用性仍存在爭(zhēng)議。一些研究表明：在低溫、中等甚至高溫下馴化的動(dòng)物比在其它溫度中馴化具有較好的功能表現(xiàn)或較高的適合度[24-26]。熱馴化的生理與行為反應(yīng)在魚(yú)類及無(wú)尾兩棲類中已有較多報(bào)道,但有尾兩棲類及陸生脊椎動(dòng)物并不多見(jiàn)[27-29]。

東方蠑螈(Cynopsorientalis)是一種分布于中國(guó)中部及東部的有尾兩棲類動(dòng)物,主要棲息于池塘、水田、流速較緩的山間溪流等水域。有關(guān)東方蠑螈的研究涉及胚胎發(fā)育、形態(tài)、繁殖等內(nèi)容,但體溫調(diào)節(jié)與功能表現(xiàn)方面未見(jiàn)報(bào)道。野外自然環(huán)境中,水溫超過(guò)10℃東方蠑螈開(kāi)始活動(dòng),3—7月雌體產(chǎn)卵,15—25℃是其適宜的生長(zhǎng)溫度[30]。本文以3個(gè)恒定馴化水溫(15、20和25℃)代表適宜東方蠑螈生長(zhǎng)的較低、中等以及較高水溫,測(cè)定其臨界高、低溫以及不同體溫下的運(yùn)動(dòng)表現(xiàn),以評(píng)價(jià)熱馴化對(duì)該種動(dòng)物熱生理特征的影響,旨在探討熱馴化是否會(huì)改變東方蠑螈的運(yùn)動(dòng)表現(xiàn)和熱耐受能力？?jī)蓷悇?dòng)物運(yùn)動(dòng)表現(xiàn)及熱耐受能力的馴化反應(yīng)是否存在種間差異？

1 材料與方法

1.1 動(dòng)物收集與處理

實(shí)驗(yàn)用東方蠑螈為變態(tài)后幼體(N= 48),2014年6月中旬購(gòu)自杭州錢江花鳥(niǎo)市場(chǎng),隨后運(yùn)至杭州師范大學(xué)兩棲爬行動(dòng)物實(shí)驗(yàn)室。蠑螈隨機(jī)放在3個(gè)塑料整理箱(60 cm × 45 cm × 35 cm)中,在實(shí)驗(yàn)室條件下適應(yīng)性養(yǎng)殖3天。用數(shù)顯游標(biāo)卡尺(0.01mm)測(cè)定蠑螈體長(zhǎng)(吻端至泄殖腔孔前緣間距),體長(zhǎng)范圍為32—43mm,隨后將個(gè)體隨機(jī)分為3組(15℃: (40.50.8) mm,N= 25; 20℃: (40.60.7) mm,N=9; 25℃: (38.90.9) mm,N=14)。將動(dòng)物個(gè)體單獨(dú)放入已標(biāo)記的塑料盒(15 cm × 10 cm × 8 cm)中,盒底加入曝曬過(guò)自來(lái)水,水深約1.5cm,上覆打有小孔的蓋子以保證空氣流通。將裝有蠑螈的塑料盒分別置于溫度預(yù)先設(shè)置為(150.5)℃、(200.5)℃和(250.5)℃的人工氣候箱(寧波萊?？萍加邢薰?中,每隔1d投喂食物(碎魚(yú)肉)1次并換水。氣候箱內(nèi)光照周期設(shè)為13L∶11D,馴化時(shí)間為4周。

1.2 運(yùn)動(dòng)表現(xiàn)的測(cè)定

蠑螈熱馴化4周后,選取無(wú)損傷、無(wú)病態(tài)的活躍個(gè)體用于隨機(jī)測(cè)定3個(gè)測(cè)試溫度(體溫)條件下的運(yùn)動(dòng)表現(xiàn)(N= 44：15℃ 23條,20℃ 8條,25℃ 13條),不同測(cè)試溫度間隔一天進(jìn)行實(shí)驗(yàn)。運(yùn)動(dòng)表現(xiàn)測(cè)定前2h,將蠑螈放置于溫度預(yù)先設(shè)定的人工氣候箱內(nèi)以控制其體溫。將蠑螈放入盛有5cm水深的長(zhǎng)方形玻璃槽(150 cm × 10 cm × 15 cm)中,玻璃槽的水溫預(yù)先調(diào)整至相應(yīng)的測(cè)試溫度,一人用毛筆輕觸蠑螈尾部以驅(qū)使其向前游動(dòng),另一人用松下HDC-HS900數(shù)碼攝像機(jī)記錄蠑螈在水中的游泳情況,每條蠑螈測(cè)定一個(gè)來(lái)回。攝像機(jī)記錄的視頻片段經(jīng)MGI Video Wave III軟件(MGI Software Co., Canada)分析讀出游泳速度。游泳速度用蠑螈游過(guò)25 cm的最大速度表示。運(yùn)動(dòng)表現(xiàn)測(cè)定結(jié)束后,將蠑螈放回原來(lái)相應(yīng)馴化溫度的塑料盒。

1.3 熱耐受性測(cè)定

運(yùn)動(dòng)表現(xiàn)測(cè)定結(jié)束,44條蠑螈在相應(yīng)馴化溫度再飼養(yǎng)一周后,用動(dòng)態(tài)法測(cè)定其CTMin和CTMax[3, 31]。臨界高、低溫測(cè)定在人工氣候箱內(nèi)進(jìn)行,為了消除不同時(shí)段對(duì)測(cè)定的影響,每日13:00—16:00進(jìn)行實(shí)驗(yàn)。實(shí)驗(yàn)動(dòng)物分批測(cè)定,單次4—6條蠑螈放入底部鋪有濕潤(rùn)紗布的玻璃缸(35 cm × 30 cm × 25 cm),缸上覆以可透氣塑料蓋以防其逃脫,玻璃缸置于人工氣候箱中。人工氣候箱內(nèi)溫度從馴化溫度以0.3℃ /min的速度下降或上升,當(dāng)氣候箱內(nèi)低于5℃或高于35℃時(shí)按0.1℃ /min改變溫度速率。當(dāng)蠑螈在強(qiáng)烈刺激下出現(xiàn)反正反應(yīng)(Righting response)時(shí)用UT- 325型電子溫度計(jì)(優(yōu)利德電子有限公司,上海)迅速測(cè)出泄殖腔溫度,表示對(duì)應(yīng)的CTMin或CTMax值。實(shí)驗(yàn)測(cè)定CTMin后,在相應(yīng)馴化溫度下繼續(xù)馴養(yǎng)3d后測(cè)定CTMax。可耐受溫度范圍(TRR)用同個(gè)體CTMax與CTMin的差值表示。臨界高低溫測(cè)定結(jié)束后3d內(nèi),4條蠑螈死亡(15℃ 1條,20℃ 1條,25℃ 2條),相對(duì)應(yīng)的CTMin、CTMax值以及可耐受溫度范圍未用于進(jìn)一步統(tǒng)計(jì)分析。馴化反應(yīng)速率(Acclimation response ratio, ARR)用馴化溫度改變1℃時(shí)對(duì)應(yīng)的CTMin或CTMax的變化值表示,即ARR=Δ CTM /Δ AT,式中Δ CTM 為CTMin或CTMax的改變量,Δ AT 為馴化溫度(AT) 的改變量。

1.4 數(shù)據(jù)處理

用Statistica 6.0統(tǒng)計(jì)軟件包(StatSoft, Tulsa, USA)處理相關(guān)數(shù)據(jù)。做進(jìn)一步統(tǒng)計(jì)檢驗(yàn)前, 用Kolmogorov-Smirnov檢驗(yàn)和Bartlett分別檢驗(yàn)數(shù)據(jù)正態(tài)性和方差同質(zhì)性。用重復(fù)測(cè)量方差分析(Repeated measures ANOVA)檢驗(yàn)馴化溫度和測(cè)試體溫對(duì)游泳速度的影響,單因子方差分析(One-way ANOVA)檢驗(yàn)臨界高低溫以及耐受溫度范圍的組間差異,Tukey檢驗(yàn)進(jìn)行多重比較。描述性統(tǒng)計(jì)值用平均值±標(biāo)準(zhǔn)誤表示,顯著性水平設(shè)置為α=0.05。

2 結(jié)果

圖1 不同熱馴化條件下東方蠑螈幼體的游泳速度Fig.1 Swimming speed of juvenile Cynops orientalis acclimated to different temperatures

各實(shí)驗(yàn)組動(dòng)物體長(zhǎng)無(wú)顯著的組間差異(F2, 45=1.04,P=0.363)。東方蠑螈幼體的游泳速度受馴化溫度(F2, 41=3.28,P=0.048)、測(cè)試體溫(F2, 82=4.31,P=0.017)以及兩者交互作用(F4, 82=6.83,P<0.001)的影響顯著(圖1)。15、20℃馴化蠑螈泳速平均值分別在15、20℃測(cè)試溫度下最大,但不同測(cè)試溫度間統(tǒng)計(jì)上無(wú)顯著差異(15℃馴化：F2, 44=1.22,P=0.306；20℃馴化：F2, 14=2.28,P=0.139)；25℃馴化蠑螈在25℃測(cè)試溫度下的泳速顯著大于15、20℃測(cè)試溫度下泳速(F2, 24=14.40,P<0.001)。15℃測(cè)試溫度下,低溫(15℃)和中等溫度(20℃)馴化蠑螈泳速快于高溫(25℃)馴化個(gè)體(F2, 41=3.43,P=0.042)；20℃測(cè)試溫度下,中等溫度馴化蠑螈泳速快于低溫及高溫馴化個(gè)體(F2, 41=5.31,P<0.01)；而25℃測(cè)試溫度下,高溫及中等溫度馴化蠑螈泳速快于低溫馴化個(gè)體(F2, 41=6.94,P<0.01)(圖1)。

馴化溫度對(duì)東方蠑螈臨界高、低溫的影響均顯著(CTMin：F2, 37=17.30,P<0.001；CTMax：F2, 37=5.92,P<0.01)。CTMin和CTMax均隨馴化溫度的升高而升高(圖2)。20℃條件馴化蠑螈具稍寬的可耐受溫度范圍(TRR),但馴化溫度對(duì)TRR的影響并不顯著(F2, 37=0.74,P=0.483,圖2)。15—20℃馴化溫度,CTMin和CTMax的馴化反應(yīng)速率(ARR)分別為0.09和0.26；而20-25℃馴化溫度,CTMin和CTMax的ARR分別為0.21和0.16。

圖2 不同熱馴化條件下東方蠑螈幼體的臨界高低溫及可耐受溫度范圍(平均值帶不同上標(biāo)字母的表示差異顯著)Fig.2 Critical thermal minimum and maximum, and thermal resistance range of juvenile Cynops orientalis acclimated to different temperatures (Means with different letters differ significantly, Tukey′s test, α=0.05, a>b)

3 討論

3.1 熱馴化對(duì)蠑螈運(yùn)動(dòng)表現(xiàn)的影響

雖然低溫及中等溫度馴化的東方蠑螈幼體在不同測(cè)試溫度的游泳速度無(wú)顯著差異,但總體上其游泳速度的熱敏感性仍存在。外溫動(dòng)物運(yùn)動(dòng)表現(xiàn)的熱功能曲線一般呈右傾的峰型曲線[2]。低溫及中等溫度馴化蠑螈泳速未表現(xiàn)明顯的測(cè)試溫度效應(yīng)可能與熱馴化改變泳速的熱敏感性有關(guān)。運(yùn)動(dòng)表現(xiàn)隨體溫變化而變化在外溫動(dòng)物中是普遍的,但不同運(yùn)動(dòng)方式的熱敏感性存在差異。一些研究表明：因水中運(yùn)動(dòng)能力的相對(duì)重要性,水生動(dòng)物(如魚(yú)類、兩棲類等)水中運(yùn)動(dòng)表現(xiàn)的熱敏感性顯著低于陸地運(yùn)動(dòng)表現(xiàn)[27-29,32-33]。低溫及中等溫度馴化蠑螈在15—25℃測(cè)試溫度范圍內(nèi)泳速無(wú)顯著變化可能部分反映出這種趨勢(shì)。當(dāng)然與蠑螈陸地運(yùn)動(dòng)表現(xiàn)熱敏感性的差異仍需進(jìn)一步確定。

馴化溫度顯著影響蠑螈幼體的運(yùn)動(dòng)表現(xiàn),這與許多其它外溫動(dòng)物的研究結(jié)果相類似。有意思的是,經(jīng)某一溫度馴化后蠑螈的游泳能力似乎在相同測(cè)試溫度下表現(xiàn)最好。例如,25℃馴化蠑螈在25℃測(cè)試溫度泳速最大；其余兩馴化條件蠑螈在對(duì)應(yīng)測(cè)試溫度下泳速亦稍大。因此,這一結(jié)果可能支持馴化有益假說(shuō),即特定溫度馴化的動(dòng)物在該溫度下具增強(qiáng)的功能表現(xiàn)和適合度[18,24]。

外溫動(dòng)物運(yùn)動(dòng)表現(xiàn)的熱馴化效應(yīng)在種間、種群間甚至不同發(fā)育階段間存在差異[19-20]。兩棲類動(dòng)物運(yùn)動(dòng)表現(xiàn)熱馴化效應(yīng)的研究結(jié)果顯示(表1)：許多兩棲類動(dòng)物幼體階段水中運(yùn)動(dòng)表現(xiàn)的熱馴化效應(yīng)顯著,但成年后陸地運(yùn)動(dòng)時(shí)該效應(yīng)基本消失。兩棲類運(yùn)動(dòng)表現(xiàn)的熱馴化效應(yīng)在不同個(gè)體階段的轉(zhuǎn)變被認(rèn)為是與其生活環(huán)境的變遷有關(guān)。兩棲類(特別是蛙類)幼體階段主要在水體中生活,而成體階段在陸地生活的時(shí)間會(huì)明顯增加；水體的溫度日波動(dòng)通常遠(yuǎn)小于陸地上的溫度日波動(dòng)。成年后上陸活動(dòng)的兩棲類逐漸適應(yīng)這種大幅度變化的陸地?zé)岘h(huán)境,同時(shí)也削弱了熱馴化對(duì)其運(yùn)動(dòng)表現(xiàn)以及其它生理行為特征的影響[19,24]。東方蠑螈生活于丘陵、山間或山邊的水塘、溝渠、水田等靜水水域中,此類水體環(huán)境的溫度變異有限,因此,與其它水生動(dòng)物相似[19-20],蠑螈幼體在水中的運(yùn)動(dòng)表現(xiàn)受熱馴化的顯著影響是可預(yù)測(cè)的。

表1 熱馴化對(duì)幾種兩棲類動(dòng)物運(yùn)動(dòng)表現(xiàn)的影響

3.2 熱馴化對(duì)蠑螈熱耐受性的影響

東方蠑螈幼體的臨界低溫(CTMin, 2.4—3.9℃)低于兩種已研究蛙類蝌蚪的相應(yīng)值(澤陸蛙Fejervaryalimnocharis：7.4—8.9℃；飾紋姬蛙Microhylaornata：8.7—11.7℃[11])；其臨界高溫(CTMax, 34.6—36.7℃)同樣低于蛙類蝌蚪的相應(yīng)值,如中國(guó)林蛙(Ranachensinensis)(35.8—39.8℃)[10],澤陸蛙(42.1—42.9℃)和飾紋姬蛙(39.8—40.9℃)[11],大蟾蜍(Bufogargarizans)(36.5—38.8℃)[39],與一些有尾類動(dòng)物的相應(yīng)值接近(34.1—38.4℃)[40-41]。東方蠑螈比一些蛙類蝌蚪具相對(duì)較低的CTMin和CTMax可能與其生境溫度相對(duì)較低有關(guān)。

熱馴化顯著影響蠑螈幼體的熱耐受能力,CTMin和CTMax隨馴化溫度的升高而上升,表明：低溫馴化個(gè)體比高溫馴化個(gè)體具較強(qiáng)抗低溫能力,而高溫馴化個(gè)體比低溫馴化個(gè)體具較強(qiáng)抗高溫能力。這與已報(bào)道的絕大多數(shù)兩棲類動(dòng)物種類的研究結(jié)果一致[1-11,39, 42]。僅在少數(shù)種類中,高溫馴化個(gè)體的抗高溫能力并不顯著大于低溫馴化個(gè)體。例如,即將發(fā)生變態(tài)的美洲林蛙(Ranasylvatica)[43]和牛蛙(Ranacatesbeiana)[44]蝌蚪在較高溫度馴化的CTMax略低于較低溫度馴化的相應(yīng)值。本研究顯示熱馴化并不影響蠑螈幼體的可耐受溫度范圍(TRR)。該特征的熱馴化效應(yīng)在不同動(dòng)物種類中存在較大差異。例如,澤陸蛙和飾紋姬蛙蝌蚪TRR隨馴化溫度的升高而降低[11],但在爬行類動(dòng)物中并不存在一致的變化趨勢(shì)[12-16,45-46]。稍涼或溫和的環(huán)境溫度可能最適于東方蠑螈幼體生長(zhǎng)[29],本研究中中等溫度馴化蠑螈顯示稍寬的TRR可能反映出接近最適溫度的馴化條件有利于表達(dá)其耐受能力。

馴化反應(yīng)速率(ARR)代表外溫動(dòng)物對(duì)環(huán)境溫度變化產(chǎn)生生理反應(yīng)的能力。兩棲類動(dòng)物CTMin和CTMax的ARR值存在顯著的種間差異(表2)。這種差異反映了在不同熱環(huán)境中動(dòng)物擴(kuò)展其耐受能力的差別,并可能與它們棲息環(huán)境的溫度條件有關(guān)。生活在短期內(nèi)溫度波動(dòng)大的環(huán)境中的種類比生活在溫度長(zhǎng)期緩慢變化的環(huán)境中的種類通常具有較強(qiáng)抵抗快速溫度變化的能力[47-48]。15—20℃馴化溫度蠑螈幼體CTMax的ARR值(0.26)大于CTMin對(duì)應(yīng)值(0.09),但20—25℃馴化溫度CTMax的ARR值(0.16)小于CTMin對(duì)應(yīng)值(0.21)。這一結(jié)果與澤陸蛙和飾紋姬蛙蝌蚪[11]和爬行類動(dòng)物[12-14,45-46]的報(bào)道相似。Chatterjee等[49]預(yù)測(cè)CTMin或CTMax的變化幅度隨著馴化溫度接近對(duì)應(yīng)熱耐受臨界值時(shí)逐漸減小至零,本文的研究結(jié)果與之相符合。然而,在一些種類中CTMin和CTMax(特別是CTMin)隨馴化溫度的變化趨勢(shì)并不總是與上述預(yù)測(cè)相符。例如,10—20℃馴化溫度美洲林蛙蝌蚪CTMin的ARR值大于CTMax的對(duì)應(yīng)值[42]。

表2 幾種兩棲類動(dòng)物臨界高低溫的馴化反應(yīng)速率

Table 2 Acclimation response ratios (ARRs) of critical thermal minimum (CTMin) and maximum (CTMax) in some species of amphibians

物種Species發(fā)育階段Developmentstage馴化溫度/(℃)Acclimationtemperature臨界低溫馴化反應(yīng)速率Acclimationresponseratioofcriticalthermalminimum臨界高溫馴化反應(yīng)速率Acclimationresponseratioofcriticalthermalmaximum無(wú)尾類Anura Fejervaryalimnocharis[11]蝌蚪26—30期20—300．140．06 Microhylaornata[11]蝌蚪26—30期20—300．30．11 Ranachensinensis[10]蝌蚪？期10—25—0．27 R．sylvatica[43]蝌蚪27—29期10—30—0．11 R．catesbeiana[44]蝌蚪28—40期15—25—0．08 Bufoamericanus[43]蝌蚪32期10—30—0．06 B．woodhousei[43]蝌蚪27—32期10—30—0．02 B．marinus[42]蝌蚪26—30期25—350．10．25 B．gargarizans[39]蝌蚪？期10—25—0．39 Pseudacristriseriata[43]蝌蚪27期10—30—0．16 Gastrophrynecarolinensis[43]蝌蚪32期20—30—0．08有尾類Caudata Euryceamultiplicata[40]成體5—15—0．13 E．lucifuga[40]成體5—15—0．02 E．longicauda[40]成體5—15—0．08 Ambystomamaculatum[40]成體5—15—0．08 Cynopsorientalis(本研究)幼體15—250．150．21

綜上所述,東方蠑螈幼體經(jīng)不同溫度馴化后其運(yùn)動(dòng)表現(xiàn)和熱耐受能力會(huì)發(fā)生改變。經(jīng)特定溫度馴化后的蠑螈在對(duì)應(yīng)測(cè)試體溫下具有較好的運(yùn)動(dòng)表現(xiàn),結(jié)果支持馴化有益假說(shuō)；低溫馴化有助于提升蠑螈的抗低溫能力,而高溫馴化能提升抗高溫能力。兩棲類動(dòng)物的熱馴化反應(yīng)存在顯著的種間差異。這些差異可能反映了不同種類個(gè)體發(fā)育過(guò)程中所經(jīng)歷熱環(huán)境的變化。棲息生境溫度變異幅度大,可能會(huì)削弱動(dòng)物生理及功能表現(xiàn)的熱馴化效應(yīng),但有助于提高其應(yīng)對(duì)溫度變化的能力。

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Physiological response and changes in swimming performance after thermal acclimation in juvenile chinese fire-belly newts,Cynopsorientalis

LU Hongliang1, GENG Jun1, XU Wei1, PING Jun2, ZHANG Yongpu2,*

1HangzhouKeyLaboratoryofAnimalAdaptationandEvolution,SchoolofLifeandEnvironmentalSciences,HangzhouNormalUniversity,Hangzhou310036,China2CollegeofLifeandEnvironmentalScience,WenzhouUniversity,Wenzhou325035,China

The thermal acclimatory capacity of a particular species determines its tolerance to environmental changes and affects its survival under future changing climatic conditions. Acclimation effects on physiological traits have been determined in many fish and frog species, but rarely in newts or salamanders. In the present study, we evaluated the physiological acclimatory response of newts. A total of 48 juvenile Chinese fire-belly newts (Cynopsorientalis) were collected and acclimated to 15℃, 20℃, and 25℃, which represented the low, intermediate, and high environmental temperatures experienced byC.orientalisduring their active period, respectively, over the course of 4 weeks. The locomotor (swimming) performances of individuals were measured at the same three test temperatures in a glass tank (150 cm × 10 cm × 15 cm) filled with water to a depth of 5 cm, and the critical thermal minimum (CTMin) and maximum (CTMax) were determined using a dynamic method. The thermal resistance range (TRR) was calculated as the difference between CTMaxand CTMin, and acclimation response ratio (ARR) of CTMinand CTMaxwas obtained by dividing the tolerance change by the change in acclimation temperature. The results from repeated-measures ANOVA analyses revealed that newt swimming speeds were significantly affected by the acclimation and test temperatures. Despite no statistically significant difference, low and intermediate temperature-acclimated newts had relatively high mean swimming speeds at 15℃ and 20℃, respectively, while the high-temperature-acclimated newts had superior swimming speeds at 25℃. Similarly, at 15℃, low temperature-acclimated newts swam faster than those acclimated to a high temperature. However, at 20℃, intermediate temperature-acclimated newts swam faster than low or high temperature-acclimated individuals, while at 25℃, high and intermediate temperature-acclimated newts swam faster than those acclimated to low temperature. Thus, our data supports the beneficial acclimation hypothesis, which predicts that acclimation to a particular temperature enhances the animal′s performance or fitness at that temperature. Our results also indicate that temperature acclimation shifts the thermal sensitivity of swimming performance inC.orientalissince low temperature-acclimated newts appear to have lower thermal sensitivity levels than those acclimated to high temperature. Both CTMinand CTMaxwere significantly enhanced at higher acclimation temperatures, suggesting that juvenile newts acclimated to low temperatures are more resistant to low temperatures and less resistant to high temperatures, whereas those acclimated to high temperatures are more resistant to high but less resistant to low temperatures. These results are consistent with previous studies focused on the various ectothermic vertebrate species analyzed to date. The TRR of newts was not affected by acclimation temperature, while the ARR of CTMax(0.26) was higher than that of CTMin(0.09) at acclimation temperatures between 15℃ and 20℃, but lower at acclimation temperatures between 20℃ and 25℃ (CTMax: 0.16vsCTMin: 0.21). These results are consistent with previous predictions that the magnitude of the change in CTMinor CTMaxslowly decreases and ultimately approaches zero as the acclimation temperature gradually reaches its thermal limits. Inter-species differences in thermal physiological response to acclimation in amphibians may be correlated with differences in thermal environments in their natural habitats.

Cynopsorientalis; thermal acclimation; thermal tolerance; locomotor performance; beneficial acclimation hypothesis

國(guó)家自然科學(xué)基金項(xiàng)目(31170376)；浙江省自然科學(xué)基金項(xiàng)目(LY15C030006,LY16C030001)

2015- 10- 06;

日期:2016- 07- 13

10.5846/stxb201510062006

*通訊作者Corresponding author.E-mail: zhangypu@126.com

陸洪良, 耿軍, 徐衛(wèi), 平駿, 張永普.東方蠑螈幼體熱耐受性和游泳表現(xiàn)的熱馴化響應(yīng).生態(tài)學(xué)報(bào),2017,37(5):1603- 1610.

Lu H L, Geng J, Xu W, Ping J, Zhang Y P.Physiological response and changes in swimming performance after thermal acclimation in juvenile chinese fire-belly newts,Cynopsorientalis.Acta Ecologica Sinica,2017,37(5):1603- 1610.