王 穎, 孫長虹, 張 偉

東北林業(yè)大學野生動物資源學院, 哈爾濱 150040

通河林區(qū)黃鼬(Mustelasibirica)冬季被毛形態(tài)結構的功能適應性

王 穎, 孫長虹, 張 偉*

東北林業(yè)大學野生動物資源學院, 哈爾濱 150040

被毛在哺乳動物適應性進化過程中執(zhí)行保溫和保護兩個重要功能，其形態(tài)結構上存在的功能適應性特征因所處的部位不同而表現(xiàn)出適應性分化現(xiàn)象，由動物體軀干至四肢末端呈顯著的梯度變化。以黑龍江省通河林區(qū)黃鼬東北亞種(Mustelasibiricamanchurica)冬季雌雄成體各10只完整毛皮對象，研究了背中部、腹中部和后肢下部3個部位的直針毛、披針毛、絨針毛、絨毛，以及后趾部硬毛的被毛性狀因子，統(tǒng)計分析表明：通河林區(qū)黃鼬相同身體部位4種類型毛的長度和細度指標均為直針毛>披針毛>絨針毛>絨毛，相同部位4種類型毛長度的相關性極顯著，直針毛細度與披針毛細度相關性極顯著(P<0.01)，絨針毛細度與絨毛細度相關性極顯著(P<0.01)，這種特征使得被毛在整體結構上為實施保溫和保護功能奠定基礎；同時，黃鼬被毛各性狀的保溫功能從背部向后趾部呈遞減趨勢，而保護功能則呈現(xiàn)遞增趨勢，被毛形態(tài)結構性狀上的分化與動物機體異溫性充分結合，對于黃鼬適應寒冷的森林生態(tài)環(huán)境具有重要意義。

黃鼬; 被毛; 形態(tài)結構; 功能適應

動物機體的形態(tài)結構特征與其所處的環(huán)境及所要發(fā)揮的功能密不可分。哺乳動物被毛是發(fā)揮相關功能以使其適應環(huán)境的重要部分[1- 6]，如一些動物被毛的顏色和斑紋對動物的隱蔽、求偶展示、吸收太陽能等起著重要作用[7- 10]；同時，被毛的形態(tài)結構性狀與所處環(huán)境也緊密相關，棲息于不同生境中的動物在被毛微觀結構上的差異十分顯著[11- 15]，即使生活在特定生境中的動物也通過被毛的季節(jié)性脫換[2,16-17]和身體不同部位被毛的性狀差異[18- 22]來適應所處的生態(tài)環(huán)境。比較動物不同身體部位的被毛特征，能夠反映出不同部位的毛對適應環(huán)境的功能分化，也可以反映出動物對其生存環(huán)境的適應[23]。但以往的研究多是探索動物被毛對高寒環(huán)境的適應策略，事實上動物被毛除了用于防御嚴寒之外[24- 26]，還要保護機體免受傷害[27-28]，并且動物被毛在生態(tài)類型復雜、惡劣氣候環(huán)境下的適應性特征和分化更加明顯；同時，以往研究也多以毛被類型簡單的動物為對象，代表性不突出。本實驗選取生態(tài)類型復雜，冬季漫長嚴寒的黑龍江省通河林區(qū)為研究地，以分布性廣、適應性強、毛被類型復雜(含直針毛、披針毛、絨針毛、絨毛、硬毛等多種類型毛)的黃鼬(Mustelasibirica)為研究對象，探討動物被毛在形態(tài)結構上普遍存在的功能適應性特征和適應性分化現(xiàn)象。

黑龍江省通河龍口林場為低山丘陵地貌，屬溫帶大陸性季風氣候區(qū)，全年平均氣溫1.9 ℃，1月極端最低氣溫達-46.2 ℃，10月下旬到翌年5月下旬為結凍期。主要的森林類型為以闊葉紅松林為主的針闊混交林和以樺樹林、楊樹林、櫟樹林組成的闊葉林，其次為榛子灌叢和胡枝子灌叢。在嚴寒而漫長的冬季，動物首先要解決保溫問題，同時由于植被類型復雜，又要強化對機體的保護以避免外界環(huán)境刮傷身體和避免被毛過長阻礙其運動[29]。通河龍口林場的特殊的環(huán)境氣候特征極適于開展動物被毛的生態(tài)適應性及功能適應性分化的研究。

1 材料與方法

1.1 材料

將2005年12月—2006年2月在黑龍江省通河龍口林場采集的黃鼬東北亞種雌雄成體各10只的完整毛皮作為實驗材料，分別在每只個體的背中部(dorsal back)、腹中部(belly)、后肢下部(lower hindleg)采集直針毛(unbent awn)、披針毛(sub-awn)、絨針毛(vellus awn)、絨毛(undercoat hair)各5根，在每只個體的后趾部(hind claw)采集硬毛(bristle)各5根。因同部位的同類型的單根毛即可進行形態(tài)學的物種鑒定[30]，5根毛的統(tǒng)計數(shù)據(jù)可以有效避免測量誤差[23]。

1.2 方法

1.2.1 光鏡樣本制備

將完整的毛樣本置于培養(yǎng)皿中，用乙醚和95%的乙醇按1∶1組成的脫脂液脫脂20min；將脫脂后的毛置于30%的過氧化氫中脫色30 min，用無水乙醇清洗10 min。將處理后的毛放到2—3 mm厚的無色有機玻璃載片上，在其上下覆以無機玻璃載片，并用鐵夾固定。放到120 ℃的DGG- 9053A型電熱恒溫干燥箱中加熱2 h；待玻璃冷卻后卸下鐵夾及無機載片，此時毛附著于有機玻璃載片上；用窄透明膠帶將整根毛粘起并平行貼于距毛鱗片印痕1—2 mm處，即制成可同時用光鏡觀察鱗片和髓質(zhì)的裝片[30]。

1.2.2 數(shù)據(jù)測量

應用H6303i生物顯微鏡及配套的圖片處理、測量軟件系統(tǒng)(重光數(shù)碼顯微系統(tǒng))對毛長度、髓質(zhì)長度、毛尖無髓段長度、毛細度、髓質(zhì)細度等指標進行測量，其中毛細度和髓質(zhì)細度以毛最粗部位為標準，測量部位見圖1。在測量前先用臺微尺對顯微鏡進行校正，測定屏幕測量值與實物真實值之間的系數(shù)，所有測量指標乘以校正系數(shù)即為所測量的真實值。

圖1 毛的測量部位示意圖(a: 毛尖無髓段長度；b: 髓質(zhì)長度；c: 毛根無髓段長度；d: 毛細度；e: 髓質(zhì)細度)Fig.1 Measurement of different hair parameters (a: Non-medulla tip length, b: Medulla length, c: Non-medulla root length, d: Hair diameter, e: Medulla diameter)

1.2.3 相對指標的計算

髓質(zhì)長度所占比例=b/(a+b+c)

毛尖無髓段長度所占比例=a/(a+b+c)

髓質(zhì)指數(shù)=e/d

1.2.4 統(tǒng)計分析

應用SPSS15.0軟件處理，先用Kolmogorov-Smirnov分別檢驗背中部、腹中部、后肢下部的直針毛、披針毛、絨針毛、絨毛及后趾部硬毛等五種類型毛的長度、髓質(zhì)長度、髓質(zhì)長度比例、毛尖無髓段長度比例、細度、髓質(zhì)指數(shù)等6個被毛性狀因子是否呈正態(tài)分布，經(jīng)檢驗數(shù)據(jù)均符合正態(tài)分布(P>0.05)。

針對同種類型毛的長度、髓質(zhì)長度、髓質(zhì)長度比例、毛尖無髓段長度比例、細度、髓質(zhì)指數(shù)等指標是否由于身體部位的不同而產(chǎn)生顯著差異，先經(jīng)方差齊性檢驗，P值均大于0.05，方差齊。因此，采用單因素方差分析中的最小顯著差數(shù)法(LSD)對所測指標進行差異顯著性檢驗[31]；并應用皮爾森(Pearson)雙變量相關性統(tǒng)計法對相同部位四種類型毛的長度、細度進行相關性分析。

2 結果與分析

2.1 相同身體部位四種類型毛的長度、細度比較

由表1可知，相同身體部位四種類型毛的長度和細度變化趨勢均為：直針毛﹥披針毛﹥絨針毛﹥絨毛；由表2可知，四種類型毛長度之間的相關性均極顯著。

由表1可知，相同身體部位的直針毛細度與披針毛細度相差不大，且直針毛細度是絨針毛細度的2倍左右，是絨毛細度的6—8倍。由表3可知，直針毛細度與披針毛、絨針毛的細度均呈顯著正相關，但與絨毛細度不相關(r=0.176,P>0.05)；披針毛細度與絨針毛、絨毛的細度均顯著正相關，絨針毛細度與絨毛細度顯著正相關(r=0.340，P<0.05)。表明黃鼬直針毛細度可能左右著披針毛和絨針毛的細度，而絨毛細度與直針毛細度無關，披針毛、絨針毛和絨毛之間的細度密切相關。

2.2 不同身體部位被毛性狀之間的比較

由表1可知，雄性直針毛的長度和細度表現(xiàn)為：背中部﹥腹中部﹥后趾部﹥后肢下部，而直針毛的其他性狀指標(如雌性直針毛的長度和細度、雌雄性直針毛的髓質(zhì)長度、髓質(zhì)長度所占比例、髓質(zhì)指數(shù))則都表現(xiàn)為：背中部﹥腹中部﹥后肢下部﹥后趾部，毛尖無髓段長度所占比例則都表現(xiàn)為：背中部﹤腹中部﹤后肢下部﹤后趾部。雖然后肢下部直針毛與后趾部硬毛的長度、細度因黃鼬性別不同呈相反的變化趨勢，但后肢下部與后趾部在毛長度(P雄∶后肢下部—后趾部=0.124>0.05,P雌∶后肢下部—后趾部=0.773>0.05)和毛細度(P雄∶后肢下部—后趾部=0. 229>0.05,P雌∶后肢下部—后趾部=0.589>0.05)上并無顯著差異。這表明在總體上直針毛和硬毛的長度、細度、髓質(zhì)長度、髓質(zhì)長度所占比例和髓質(zhì)指數(shù)由軀干向四肢末端遞減，毛尖無髓段長度所占比例則正好相反(注：為了便于說明問題，將后趾部的硬毛與直針毛統(tǒng)一進行比較) 。

無論雌雄，披針毛的長度、髓質(zhì)長度、髓質(zhì)長度所占比例、細度、髓質(zhì)指數(shù)都表現(xiàn)為：背中部﹥腹中部﹥后肢下部，披針毛的毛尖無髓段長度所占比例則都表現(xiàn)為：背中部﹤腹中部﹤后肢下部。表明披針毛的長度、細度、髓質(zhì)長度、髓質(zhì)長度所占比例和髓質(zhì)指數(shù)由軀干向四肢末端遞減，毛尖無髓段長度所占比例則正好相反。

對于絨針毛，除了雌性的髓質(zhì)指數(shù)表現(xiàn)為：腹中部﹥背中部﹥后肢下部外，毛長度、髓質(zhì)長度、髓質(zhì)長度所占比例、毛細度、雄性絨針毛髓質(zhì)指數(shù)都表現(xiàn)為：背中部﹥腹中部﹥后肢下部；毛尖無髓段長度所占比例為：背中部﹤腹中部﹤后肢下部。這表明在總體上絨針毛的長度、細度、髓質(zhì)長度、髓質(zhì)長度所占比例和髓質(zhì)指數(shù)由軀干向四肢末端遞減，毛尖無髓段長度所占比例則正好相反。

除了絨毛細度、雄性絨毛的髓質(zhì)指數(shù)表現(xiàn)為：腹中部﹥背中部﹥后肢下部外，毛長度、髓質(zhì)長度、髓質(zhì)長度所占比例、雌性絨毛的髓質(zhì)指數(shù)都表現(xiàn)為：背中部﹥腹中部﹥后肢下部，毛尖無髓段長度所占比例則為：背中部﹤腹中部﹤后肢下部。絨毛相應性狀的身體部位差異不明顯，只有毛尖無髓段長度由軀干向四肢末端明顯增大。

雄性直針毛和披針毛的髓質(zhì)長度所占比例、雄性直針毛的毛尖無髓段長度所占比例、雌雄性直針毛及雄性披針毛的毛細度、雄性直針毛及雌雄性披針毛的髓質(zhì)指數(shù)等指標在背中部與腹中部之間無顯著差異(P背中部—腹中部>0.05)，以及腹中部與后肢下部直針毛的髓質(zhì)指數(shù)無顯著差異外(P腹中部—后肢下部>0.05)，其他性狀指標之間都存在顯著差異。表明背中部與腹中部的絨針毛和絨毛的相應性狀無明顯差異。

表2 雌雄黃鼬四種類型毛長度相關性(n=400)

表3 雌雄黃鼬四種類型毛細度相關性 (n=400)

3 討論

被毛作為哺乳動物身體最外層的部分，對機體的保溫和抗機械損傷起著重要作用。在宏觀性狀上，動物通過增加被毛的長度和密度來適應寒冷環(huán)境[22,24,29,32]。在微觀結構上，動物被毛的性狀指標也同樣具備一定的保溫和抗機械損傷功能，如通過擴大髓質(zhì)的比例來加強保溫[6,21,24]或者調(diào)節(jié)髓質(zhì)發(fā)達程度、鱗片的排列方式和密集程度實現(xiàn)保溫和保護功能[33]。但毛長度過長不利于動物的奔跑[29,34]；髓質(zhì)占據(jù)毛空間的比例過大，降低了毛的彈性、強度和韌性[30],同時也影響被毛的抗機械損傷功能[35-36]；毛尖無髓段比例越大，動物身體上被毛的耐磨性越強[37]。所以動物要增強被毛的保溫功能，就會弱化其保護功能，同一部位被毛在微觀性狀上的保溫和保護功能不可能同時得到最好的表達。但是動物機體存在異溫性，這對于動物在被毛微觀結構上解決保溫和保護功能的矛盾發(fā)揮了重大作用。故在長期的進化過程中，動物被毛的功能分化與動物機體的異溫性相結合，使得被毛在微觀性狀上很好地解決了保溫和保護功能上的矛盾[21]。

黃鼬被毛在整體上明顯分化為直針毛、披針毛、絨針毛、絨毛4種類型的毛，它們呈4層分布，構成錯落有致的防護層，絨毛細度與直針毛細度無關且長度遠遠小于直針毛，可以充分填充直針毛、披針毛間的空隙，從而增加毛密度；而且絨針毛下部及絨毛整體的彎曲結構，使動物被毛之間可容納較多的靜止空氣，可降低冷空氣進入被毛內(nèi)的速度，從而加強了保溫作用。同時，由于直針毛和披針毛位于毛被的最上層，先與環(huán)境接觸，對毛被的整體結構起支撐作用，它們的紡錘形結構，使得毛頭部位相對較粗、也較絨針毛和絨毛結實，且毛頭部位皮質(zhì)層發(fā)達，抗機械損傷性能強，有效地保護了下部的絨針毛和絨毛。

研究表明，背中部被毛的長度最大，增加了背部保溫層的厚度；同時髓質(zhì)長度最長、髓質(zhì)長度所占比例、毛細度及髓質(zhì)指數(shù)最大、毛尖無髓段所占比例最小，由此多方面地增加了背中部被毛髓質(zhì)所占的比例，使單根毛能夠容納更多的靜止空氣。因為背部接近體核且直接暴露，需要具有極強保溫功能的被毛來阻止身體熱量的流失[20,38]。

后趾部由于與外環(huán)境直接接觸多，需要強化保護功能。其硬毛最短，有利于動物的活動，倘若通過增加毛長度來加強緩沖能力，則不利于黃鼬的穿行，也易造成被毛與植被纏結。但硬毛的髓質(zhì)指數(shù)最小，則皮質(zhì)層最發(fā)達，同時髓質(zhì)長度及髓質(zhì)長度所占比例最小、毛尖無髓段所占比例最大，這避免了由于髓質(zhì)比例過大導致的毛脆、易折斷等不利情況，增加了毛的彈性和強度，使毛的抗機械損傷功能加強[34-35]。但后趾部被毛的這些特點勢必降低其保溫功能，動物體的異溫性恰好彌補了這一不足。

腹中部被毛的諸多性狀與背中部被毛的相關性狀接近，這是由于腹部位于體核需要加強保溫，同時又處于體核下部，處于保溫向保護的過渡階段。在后肢下部的上毛中，除雄性黃鼬在直針毛的髓質(zhì)指數(shù)上與腹中部直針毛無顯著差異外，其他性狀均與腹中部存在顯著差異，而雌雄黃鼬后肢下部直針毛的長度、細度與后趾部硬毛更加接近(P后肢下部—后趾部>0.05)，由此可見，后肢下部直針毛的功能更趨向于接近后趾部硬毛，主要實施保護。

進而，由表1可知，黃鼬被毛各形態(tài)結構性狀從背部向肢體末端的保溫功能呈逐漸下降趨勢，而抗機械損傷功能呈逐漸上升趨勢，并在腹中部和后肢下部表現(xiàn)出過渡特征。背中部被毛與后趾部上毛的形態(tài)結構性狀處于保溫與保護功能的兩個極端，而腹中部與后肢下部則處于中間狀態(tài)。Underwood[19]和Moen[20]研究發(fā)現(xiàn)北極狐和黑熊的被毛厚度由背部向四肢末端逐漸降低，這與本文的研究結果相一致。被毛長度越短，熱量散失得越快，保溫性能則越低，動物體的異溫性特征正好彌補了保溫功能由軀干至四肢末端梯度降低的不足[17]。許多學者的研究也表明被毛因部位的不同分化出分別執(zhí)行保溫功能和保護功能的結構特征，馬鹿東北亞種冬季從臀部向蹄部被毛保溫功能逐漸降低，保護功能逐漸增加[21]。狍冬季采食較困難，需要大量運動，為適應積雪和草木干枯所增大的磨損作用，其被毛的保護功能由軀干向四肢逐漸增大[6]。白唇鹿在被毛性狀的保溫和保護功能上的表現(xiàn)也是如此，這與其需要在高寒草原和灌叢中快速奔跑相適應[39-40]。生活于通河林區(qū)的黃鼬冬季食物主要是鼠類，通河林區(qū)植被類型復雜[41-42]，需要在布滿榛子灌叢和胡枝子灌叢的厚雪地上獵食鼠類，對腹部和四肢的被毛造成巨大的機械磨損作用，黃鼬的腹部和四肢的抗機械損傷功能增強后，對防止動物被植物傷害顯得極其重要[42]，因此其被毛的保溫功能和保護功能由軀干至四肢出現(xiàn)了適應性的變化。

綜上所述，被毛分化為四種類型，使得毛被在整體結構上對于黃鼬具備一定的保溫和緩沖功能，在此基礎上，被毛微觀結構上的分化又滿足了黃鼬身體不同部位對保溫和保護功能的需要，這一特性與動物機體的異溫性結合，使得肢體末端、趾部等與外環(huán)境接觸較多的部位的被毛在微觀上強化了保護功能，從而在降低了保溫功能的情況下不至凍傷機體。這對于黃鼬適應殘酷寒冷的森林環(huán)境具有重要意義。

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Hair morphology as functional adaptation in winterMustelasibiricain Tonghe forest area

WANG Ying, SUN Changhong, ZHANG Wei*

CollegeofWildlifeResources,NortheastForestryUniversity,Harbin150040,China

The body function and external morphology of animals with long life span are affected by the environment. Changes in environmental factors, such as temperature, humidity, and illumination, affect the animal′s appearance and its internal functions through changes in physiological mechanisms. Many species of mammals are characterized by a layer of hair on the skin. Hair, being constantly exposed to the outside environment, directly indicates functional adaptations to the environment. Adaptation to the environment is caused by a long-lasting selection pressure on a trait as a result of natural selection. To fit the environment, animal can change a series of traits, such as color and body shape. The hairs, which serve for thermal insulation and protection, are the result of a long adaptive evolution. As a result of geographic isolation, populations of one species that are isolated from each other for a long time undergo speciation, resulting in subspecies or new species. Morphological structure of hairs covering different body regions is the result of different functional adaptations. Often there is a gradient in hair variation from the body to the end of the limbs in many mammals. Siberian weasel is a valuable fur animal and a subject of various studies in China. The animal molts seasonally starting from tail to hips, back, and neck, and lastly head and limbs in the fall, and in the opposite direction in the spring. The hair type in Siberian weasel is complex. On the basis of its shape and structure, hair is divided into guard hair, sub-awn, vellus awn, undercoat hair, and bristles. In this study, we measured the length and diameter of guard hair, sub-awn, vellus awn, and undercoat hair, all of which were sampled from the center of the back and venter, the lower end of hind limb, and bristles from the upper side of the hind toe. These hairs were collected from winter pelage of 20 adult Siberian weasels located in Tonghe forest area of Heilongjiang Province. Results showed that the length and diameter of the four types of hair always decreased at the same position. We detected significant correlation between the length of the four hair types (P< 0.01) and significant positive correlation between the diameter of guard hairs and sub-awns (P< 0.01) as well as between vellus awns and undercoat hairs (P< 0.01). The character of each hair type provided the potential to properly insulate and protect animal body as a whole. Thus, the insulation provided by the hair decreased from the back to the hind toe, whereas the protection increased. The hair traits differed among body regions in relation to different temperatures at those parts. We collected and analyzed morphological characters of the guard hair including its length and width, cuticular scale pattern, and medulla. We found significant difference in hair density between the winter and summer coat, hair length, and proportion of absent medulla in guard hair, and we discuss the adaptive mechanism of this variation. Pelage is found only in mammals, where during the course of evolution, its primary role became insulation and protection from the elements. The morphology of the pelage related to the insulation and protection function differed significantly between body regions, resulting from the differentiation of the characteristics during the course of adaptation of pelage. There is a visible gradient in its morphology from the trunk to the limbs. This study reported functional adaptability of the morphological structure of winter pelage of Siberian weasel. The fur was sampled from 20 Siberian weasels (10 males and 10 females) from Longkou Forest Farm of Tonghe in Xiaoxingan Mountain, Heilongjiang Province, in winter from December 2005 to February 2006. Five hairs of each of the four hair types (unbent awn, sub-awn, vellus awn, undercoat hair) were sampled from different parts of the body including dorsal back, venter, and lower hind leg, and five bristles were sampled from upper side of hind claw. The length of the hair, medulla, and non-medulla tip as well as the diameter of the hair and medulla were measured in all sampled hairs and the measurements were used to calculate the proportion of the length of medulla, non-medulla tip, and indexes of medulla (proportion of medulla diameter to hair diameter). All the measurements were carried out by using microscope photography and its supporting software for photo processing and measuring. The analyses indicated a significant correlation between the length of the four hair types and a significant positive correlation between the diameter of unbent awn and sub-awn (P< 0.01) and between vellus awn and undercoat hair (P< 0.01); the hair length played a very important role in the insulation and protection properties of the pelage. Furthermore, the morphological properties of the Siberian weasel winter pelage showed a gradual change from the trunk to the limbs, indicating that the gradient in the insulation and protection function of the pelage corresponds to the heterothermy. Observed polarization of winter pelage in Siberian weasel is the result of adaptation to cold environment in winter. This study provided insights into the strategies of Siberian weasel to adapt to cold climate in the Tonghe forest area.

Siberian weasel; pelage hairs; morphological structure; functional adaptation

國家自然科學基金(30570272)

2013- 11- 27;

日期:2014- 11- 03

10.5846/stxb201311272833

*通訊作者Corresponding author.E-mail: zwfur@aliyun.com

王穎, 孫長虹, 張偉.通河林區(qū)黃鼬 (Mustelasibirica)冬季被毛形態(tài)結構的功能適應性.生態(tài)學報,2015,35(17):5623- 5631.

Wang Y, Sun C H, Zhang W.Hair morphology as functional adaptation in winterMustelasibiricain Tonghe forest area.Acta Ecologica Sinica,2015,35(17):5623- 5631.