齊占會,王 珺,毛玉澤,張繼紅,方建光

(1. 農業(yè)部南海漁業(yè)資源開發(fā)利用重點實驗室,廣東省漁業(yè)生態(tài)環(huán)境重點實驗室,中國水產科學研究院南海水產研究所, 廣州 510300； 2. 中國水產科學研究院黃海水產研究所,青島 266071)

兩種海星對三種雙殼貝類的捕食選擇性和攝食率

齊占會1, 2,王 珺1,毛玉澤2,張繼紅2,方建光2

(1. 農業(yè)部南海漁業(yè)資源開發(fā)利用重點實驗室,廣東省漁業(yè)生態(tài)環(huán)境重點實驗室,中國水產科學研究院南海水產研究所, 廣州 510300； 2. 中國水產科學研究院黃海水產研究所,青島 266071)

在實驗室條件下,研究了多棘海盤車和海燕這兩種海星對櫛孔扇貝、菲律賓蛤仔和貽貝三種雙殼貝類的捕食選擇性和攝食率及溫度的影響,測定了捕食Q10溫度系數。結果顯示：多棘海盤車和海燕對三種貝類均可捕食,且表現出明顯的捕食選擇性,選擇順序依次為菲律賓蛤仔、貽貝和櫛孔扇貝。海星對菲律賓蛤仔的攝食率顯著高于其他兩種貝類,分別為0.50和0.37個/d；對扇貝的攝食率最低,分別為0.05和0.07個/d。海星攝食率隨水溫升高而呈上升的趨勢,總平均攝食干重分別為0.69 和0.79 g/d。水溫從4.3 ℃升高到7.8 ℃多棘海盤車和海燕捕食Q10系數分別為6.38和2.33,而水溫從7.8 ℃升高至13.3 ℃時,Q10系數沒有顯著升高,分別為1.13和1.22。說明水溫從4.3 ℃升高時,海星捕食強度顯著升高,是防御海星的重點時期。根據海星對貝類捕食的選擇性,可在養(yǎng)殖籠內放入貽貝等低值貝類來保護扇貝,緩沖海星對扇貝的捕食,并在緩沖期間對養(yǎng)殖籠內的海星進行清除。

海星；多棘海盤車；海燕；捕食選擇性；攝食率

海星屬于棘皮動物,海星綱(Asteroidea),是典型的掠食性動物,可捕食貝類、海膽、珊瑚和螃蟹等,對潮間帶生物和底棲生物群落的異質性和生物多樣性具有重要影響[1- 4]。我國沿海分布的海星主要屬于海盤車科(Asteriidae)和海燕科(Asterinidae)的種類。海星爆發(fā)時數量可達150000—720000個/公頃[5- 6],是養(yǎng)殖貝類主要敵害生物之一[7- 11]。2007年青島附近海域海星出現暴發(fā)性增殖,幾乎使沿岸海域養(yǎng)殖的貝類損失殆盡。作者對青島流清河海域吊養(yǎng)的櫛孔扇貝養(yǎng)殖籠內海星的情況進行了調查統(tǒng)計,發(fā)現幾乎所有籠內都有海星存在,扇貝死亡率在80%以上。

弄清海星的攝食率、捕食選擇性及關鍵受控因素是揭示其對海洋生物群落影響和作用機制的基礎[12- 15],也是研究其防治策略,規(guī)避其危害的前提[16- 18]。但目前國內對海星捕食選擇性、捕食速率及影響因素等的研究還較少[19, 33]。

多棘海盤車Asteriasamurensis和海燕Asterinapectinifera是我國沿海兩種最常見的海星種類。本文以這兩種海星為對象,研究了它們對櫛孔扇貝、菲律賓蛤仔和貽貝三種貝類的捕食選擇性和攝食率以及溫度的影響,探討了海星捕食機制,旨在揭示海星捕食生理生態(tài)學特征,為進一步研究海星防控策略,減少其對養(yǎng)殖貝類的危害提供科學依據。

1 材料與方法

1.1 實驗材料

實驗用多棘海盤車(輻徑114—135 mm)和海燕(輻徑41—53 mm)均從山東榮成桑溝灣尋山海區(qū)用地籠網捕獲。所用櫛孔扇貝Chlamysfarreri、菲律賓蛤仔Ruditapesphilippinarum和貽貝Mytilusgalloprovincialis均取自桑溝灣養(yǎng)殖海區(qū)。

1.2 養(yǎng)殖條件

實驗于2008年3月19日至4月5日在山東榮成尋山集團海洋生物實驗室進行。海星和貝類在水泥池(長×寬×高=6.0 ×1.0 ×0.5 m,水體2400 L)內養(yǎng)殖。實驗用海水為桑夠灣海域天然海水,經過沉淀和沙濾后使用。實驗期間海水水質參數用YSI6600測量,溶解氧在5.0 mg/L以上,鹽度32.14-32.54,pH 7.93—8.10。每天8:00全部換水一次。采用自然光照。實驗開始前海星暫養(yǎng)馴化一周,使其適應養(yǎng)殖環(huán)境和實驗處理。馴化期間混合投喂實驗貝類,待海星攝食穩(wěn)定后開始實驗。

1.3 實驗設計

多棘海盤車和海燕在水泥池內的養(yǎng)殖密度為5只/池,每水泥池內投喂櫛孔扇貝、菲律賓蛤仔和貽貝各30粒。投喂時將這三種貝類充分混合,使各種貝在水泥池底隨機分布,遭遇海星捕食的條件相同。每天7:00和17:00觀察記錄海星對貝類的捕食情況,撿出死殼,不補充貝類。研究這兩種海星對三種不同貝類的攝食率和捕食選擇性。每實驗處理設置三個重復。實驗用貝均是達到商品規(guī)格的貝類,貝類的軟體組織在65 ℃下烘干48 h后稱量干重,實驗貝類生物學參數見表1。

1.4 數據處理

1.4.1 攝食率

從3月19日至4月5日記錄分別記錄多棘海盤車和海燕所捕食的貝類種類和數量,某種貝類開始被捕食即計為計算海星對該種貝類攝食率的起始時間。攝食率(個/d；Feed intake (FI): ind/d) 的計算公式為：

FI=D/t

式中,D為海星對某種貝類的捕食數量(個),t為時間(d)。

1.4.2 捕食比例

統(tǒng)計3月19日—24日,3月25日—30日和3月31日—4月5日三個時間段內,多棘海盤車和海燕所捕食的貝類的種類和數量,分析各種貝類在海星獵物中所占比例及隨時間的變化。捕食比例(P)的計算公式為：

P=n/N×100%

式中,n為被海星所捕食的某一貝類的數量(個),N為海星捕食的三種貝類的總數量(個)。

1.4.3 捕食溫度系數

記錄兩種海星在4.3 ℃、7.8 ℃和13.3 ℃下的總攝食干重?？倲z食干重以所捕食的三種貝類軟體組織的總干重計算,連續(xù)記錄5d,以平均值作為該溫度下海星的捕食強度(g/d)。溫度系數(Q10) 的計算公式為：

Q10=(V2/V1)10/(t2-t1)

式中,Q10表示溫度每升高10 ℃時捕食強度增加的倍數；V1和V2為捕食強度；t1和t2分別為各階段的開始和結束溫度。

1.4.4 統(tǒng)計分析

數據以平均值±標準誤(mean±S.E.)表示。采用單因子方差分析(one-way ANOVA)和Duncan多重比較對數據差異進行分析,以Plt;0.05作為差異顯著標準。數據統(tǒng)計分析采用Statistica 6.0軟件進行。

表1 實驗貝類的生物學參數指標

2 實驗結果

2.1 海星捕食行為觀察

圖1 海星捕食行為(A)海燕捕食櫛孔扇貝,(B)多棘海盤車捕食櫛孔扇貝,(C)海燕捕食貽貝,(D)多棘海盤車捕食菲律賓蛤仔Fig.1 The feeding behavior of sea stars: (A) A. amurensis prey on C. farreri, (B) A. amurensis prey on C. farreri, (C) A. amurensis prey on M. galloprovincialis, (D) A. amurensis prey on R. philippinarum

觀察發(fā)現多棘海盤車和海燕捕食時主要靠腕足上細小的管足將獵物“包裹”住,抱縛于腹面盤中央的“口”部。管足吸附在貝殼上并向兩側拉伸,拉開很小的縫隙,將賁門胃伸及貝殼內注入消化液消化并吸食貝類軟體組織,之后將完整的貝殼拋棄。實驗過程中發(fā)現多棘海盤車和海燕可同時捕食兩只或多只菲律賓蛤仔或貽貝(圖 1)。相對于海燕,多棘海盤車的警惕性更高,對外界刺激也更為敏感,捕食過程中受到干擾時,很容易將已捕獲的獵物“吐出”放棄捕食,而海燕可以忍受更大程度的干擾,這可能是其獵食活動更為旺盛的原因之一。實驗過程中發(fā)現兩種海星在白天和夜間均有捕食活動,但夜間捕食強度明顯高于白天,這可能是海星對光線較暗的海底生境產生的適應性。

2.2 海星對貝類的捕食選擇性

海星對貝類的選擇性和捕食比例見圖2。兩種海星對這三種貝類均有捕食,且表現出明顯的主動選擇性。實驗初期兩種海星均明顯優(yōu)先捕食菲律賓蛤仔,其次為貽貝,當這兩種貝類數量減少時,對櫛孔扇貝的捕食比例才有所增加。3月19日—24日,多棘海盤車捕食的菲律賓蛤仔、貽貝和櫛孔扇貝比例分別為64.28%,28.57%和7.14%；海燕對這三種貝類的捕食占比例分別為50%,44.44%和5.56%。結果表明多棘海盤車和海燕三種貝類的主動選擇順序依次為：菲律賓蛤仔、貽貝和櫛孔扇貝。

圖2 多棘海盤車(A)和海燕(B)對3種貝類的捕食比例Fig.2 The percentage of bivalves preyed by sea stars (A) Asterias amurensis and (B) Asterina pectinifera

2.3 海星對貝類的攝食率

多棘海盤車和海燕均是對菲律賓蛤仔的攝食率顯著高于對其他兩種貝類的攝食率,分別為0.50和0.37個/d,對扇貝的平均攝食率最低,分別為0.05和0.07個/d。對菲律賓蛤仔的攝食率顯著高于其他兩種貝類(Plt;0.05)(表2)。在本實驗條件下,多棘海盤車和海燕攝食率均隨水溫升高而呈上升的趨勢,每天總的平均攝食干重分別為0.69 g/d和0.79 g/d(表2,圖3)。從4.3℃到7.8℃多棘海盤車和海燕的Q10系數分別為6.38和2.33,而水溫從7.8℃繼續(xù)升高至13.3℃時,Q10系數變化不顯著,分別為1.13和1.22(表3)。

圖3 海星攝食率隨溫度變化趨勢(A)多棘海盤車和(B)海燕Fig.3 Variation of feeding rates with water temperature (A) Asterias amurensis and (B) Asterina pectinifera on bivalves

種類Species攝食率Feedingrate/(個/d)櫛孔扇貝Chlamysfarreri菲律賓蛤仔Ruditapesphilippinarum貽貝Mytilusgalloprovincialis總攝食干重(g/d)Totalfeedingrate多棘海盤車Asteriasamurensis0.05±0.02a0.50±0.10b0.26±0.09c0.69±0.08海燕Asterinapectinifera0.07±0.02a0.37±0.08b0.27±0.06c0.79±0.04

同一行中沒有相同字母上標的數值之間差異顯著

表3 多棘海盤車和海燕的捕食溫度系數

3 討論

3.1 海星捕食選擇性

海星捕食過程包括搜索遭遇獵物、捕食獵物和處理取食獵物等環(huán)節(jié)[20- 22]。每個環(huán)節(jié)如海星個體大小和處理獵物所需時間[20, 23]以及獵物的種類、大小和密度等都會影響海星對食物的選擇[24, 33]。海星對食物的選擇,分為主動選擇和被動選擇。Wong and Barbeau[16]研究了海星Asteriasvulgaris對扇貝Placopectenmagellanicus和貽貝Mytilusedulis的捕食選擇性,發(fā)現在貽貝存在的情況下,無論是主動選擇還是被動選擇,海星都優(yōu)先選擇貽貝,主要是由于貽貝不能通過游泳移動來逃避捕食,更易被捕獲。與之相一致,本研究也發(fā)現多棘海盤車和海燕也都表現出了對食物的主動選擇性,均優(yōu)先選擇捕食菲律賓蛤仔和貽貝,只有這兩種貝類數量變小時才增加對櫛孔扇貝的捕食。這可能主要受到捕食能量效率的影響,海星捕食的能量效率主要受到獵物的豐度和能量含量高低以及搜尋和處理獵物時的能量消耗等因素的影響,這些因素是決定了海星對食物的選擇[1, 25- 26]。從能量效益角度分析,單次捕食選擇較大規(guī)格的貝類能量收益較高,但在捕捉和處理獵物過程中能量消耗也較多,尤其是還存在捕食不成功的風險,反而降低了捕食的能量效率。

本實驗采用的櫛孔扇貝個體相對較大,閉殼肌發(fā)達閉合力強,并且扇貝殼上有尖利的棘刺,不利于海星捕食,反而是選擇小規(guī)格的貝類比較容易捕食,能量效率也相對更高[27- 28]。Sommer等[29]研究了個體大小對海星Asteriasrubens捕食貽貝M.edulis的影響,也發(fā)現海星傾向于捕食個體相對較大的貽貝,但不捕食殼長在4.8 cm以上的貽貝,也主要是由于能量效率的原因。杜美榮等[19]研究報道多棘海盤車優(yōu)先選擇貽貝,而不是菲律賓蛤仔,與本實驗結果存在一定差異。這可能是由于他們所采用的貽貝(殼長10—21mm)小于菲律賓蛤仔(殼長19—27mm),而本實驗采用的貽貝和菲律賓蛤仔規(guī)格相近(表 1),這也證明了貝類的個體大小是影響海星捕食選擇的重要因素。

3.2 海星攝食率及溫度的影響

不同種類海星的攝食率存在很大差異。Nadeau等[17]研究結果顯示,在水溫10—15 ℃條件下,海星A.vulgaris(輻徑70—90 mm)和L.polaris(輻徑90—110 mm)對扇貝P.magellanicus(殼長25—35 mm)的攝食率分別為0.9和0.02個/d,高于本實驗中海星的攝食率(表2),這主要是由于海星種類和貝類規(guī)格不同,本研究采用的扇貝規(guī)格較大,能量含量較高,且對海星捕食具有一定防御抵抗能力,而小規(guī)格扇貝更易受到攻擊捕食。

溫度對于變溫動物的生命活動具有顯著的影響。研究發(fā)現海星捕食強度主要受到獵物密度和規(guī)格[17- 18]、底層基質[24]和水溫[30]等的影響。溫度升高會使捕食者用于捕食活動的時間增加,尋找獵物時的活動速度也更快,進而使發(fā)現獵物的機率升高,并且也會使捕捉和處理獵物的時間縮短,總體上提高了捕食效率[30]。這一現象在其它水生生物如蟹類等的捕食研究中也得到了證實[31- 32]。本研究結果顯示,在一定范圍內多棘海盤車和海燕對貝類的捕食強度均隨著溫度的升高而增加。這與Barbeau和Scheibling[30]的研究結果相一致,他們也發(fā)現海星A.vulgaris對扇貝P.magellanicus的捕食強度在一定范圍內隨水溫上升而升高,但捕食強度升高的溫度范圍與本研究結果存在顯著的差異。他們發(fā)現當水溫從4 ℃升高至8 ℃,海星的捕食強度沒有明顯的變化,而溫度從8 ℃繼續(xù)升高至15 ℃時,捕食強度顯著提高(Q10=6.9)。本研究中從4.3 ℃到7.8 ℃海星捕食強度明顯提高(Q10系數分別為6.38和2.33),但繼續(xù)升高至13.3 ℃,捕食強度變化不明顯(Q10系數分別為1.13和1.22)(表3)。這些不同的實驗結果表明不同種類海星最適捕食的溫度不同。本實驗是在水溫4.3—13.3 ℃條件下進行的,海星在其他溫度范圍下的捕食情況以及捕食的最適溫度還需要進一步研究確定。

3.3 海星防御建議

網籠養(yǎng)殖的貝類主動逃避海星捕食的能力較差,一方面由于櫛孔扇貝等貝類的成熟個體通過足絲附著在養(yǎng)殖籠上營固著生活,另一方面具有一定游泳遷移能力種類,也幾乎不可能從養(yǎng)殖籠內逃脫,因此只能通過采取其它措施來防御海星捕食。本研究的結果顯示水溫從4.3℃升高至7.8℃時海星的捕食強度顯著升高,這一階段是防御海星的重點時期。根據海星對貝類捕食的選擇性,可在養(yǎng)殖籠內放入貽貝等低值貝類來保護扇貝,緩沖海星對扇貝的捕食,并在緩沖期間對養(yǎng)殖籠內的海星進行清除。

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PreyselectionandfeedingrateofseastarsAsteriasamurensisandAsterinapectiniferaonthreebivalves

QI Zhanhui1, 2, WANG Jun1, MAO Yuze2, ZHANG Jihong2, FANG Jianguang2,*

1KeyLaboratoryofSouthChinaSeaFisheryResourcesDevelopmentandUtilization,MinistryofAgriculture;KeyLaboratoryofMarineFisheryEcologyEnvironmentofGuangdongProvince/SouthChinaSeaFisheriesResearchInstitute,ChineseAcademyofFisherySciences;Guangzhou510300,China2YellowSeaFisheriesResearchInstitute,ChineseAcademyofFisheriesSciences,Qingdao266071,China

Sea stars are one of the primary predators of shellfish and often cause mass mortality among cultured shellfish. To develop effective control strategies, it is critical to understand the feeding ecophysiology (e.g., feeding rate and prey selection) of sea stars.

AsteriasamurensisandAsterinapectiniferaare the dominant sea star species in the coastal waters of China. We evaluated prey selection and the feeding rate of these two sea stars on three species of bivalves: scallopsChlamysfarreri, clamsRuditapesphilippinarum, and blue musselsMytilusgalloprovincialis. The experimental sea stars and bivalves were collected from Sanggou Bay, Northern China and transported to our seaside laboratory. The animals were acclimated to laboratory conditions for 7 d prior to the initiation of the experiment. The experiment was conducted between March 19 and April 5, 2008, at different seawater temperatures. Following acclimation, the sea stars were placed in cement tanks (L×W×H=6×1×0.5 m) at a density of 5 individuals per tank (single species per tank). The sea water was pumped from Sanggou Bay and sand filtered. Daily water exchange was ca 100%. We placed the bivalves (N=30 per species) evenly in each tank to ensure the sea stars had an equal probability of encountering the three species of bivalves. Each treatment was conducted in triplicate (N= 3 tanks). The number of bivalves of each species preyed upon by the sea stars was recorded twice daily at 7:00 and 17:00. In addition, we measured theQ10coefficient at water temperatures ranging from 4.3—7.8℃ and from 7.8—13.3℃.

Both species of sea star preyed on all three bivalve species. Similarly, both species exhibited preference in the order clamgt;musselgt;scallop. During the first part of the experiment (March 19—24),A.amurensispreyed on 64.28, 28.57, and 7.14% of the scallops, clams, and blue mussels, respectively.A.pectiniferapreyed upon 50, 44.44, and 5.56% of the bivalve species, respectively. The mean feeding rates ofA.amurensisandA.pectiniferaon the clam (0.50 and 0.37 ind/d, respectively) and blue mussel (0.26 and 0.27 ind/d, respectively) were significantly higher than those on the scallop (0.05 and 0.07 ind/d, respectively). The feeding rate was significantly influenced by water temperature and generally increased with increasing water temperature. The total mean feeding rates of the two sea stars were 0.69 and 0.79 g·d-1, respectively (based on dry tissue weight of bivalves). As water temperature increased from 4.3 to 7.8℃, theQ10coefficients forA.amurensisandA.pectiniferawere 6.38 and 2.33, respectively. However, when the water temperature was increased from 7.8 to 13.3℃, there was no increase in the feeding rate (Q10=1.13 and 1.22, respectively). Our results have implications for the provision of protective refuges for the species of interest (i.e., scallops) during culture in suspended lantern nets. Protective strategies are most likely to be needed when the water temperature increases above 4.3℃, as the feeding rate and activity of sea stars increased significantly above this point. Based on prey selectivity, bivalves that have a lower commercial value (e.g., blue mussels) may be co-cultured in the scallop lantern nets to serve as a buffer against predators. Furthermore, any sea stars present in the cultivation nets should be removed during the buffering period.

sea star;Asteriasamurensis;Asterinapectinifera; prey selection;feeding rate

國家自然科學基金(41106088)；“十二五”國家科技支撐計劃(2011BAD13B02)；863計劃(2012AA052103)；重點實驗室開放課題(201104,MESE- 2011- 02,開- c10- 09)

2012- 08- 21;

2013- 08- 20

*通訊作者Corresponding author.E-mail: Fangjg@ysfri.ac.cn；qizhanhui@scsfri.ac.cn

10.5846/stxb201208211174

齊占會,王珺,毛玉澤,張繼紅,方建光.兩種海星對三種雙殼貝類的捕食選擇性和攝食率.生態(tài)學報,2013,33(16):4878- 4884.

Qi Z H, Wang J, Mao Y Z, Zhang J H, Fang J G.Prey selection and feeding rate of sea starsAsteriasamurensisandAsterinapectiniferaon three bivalves.Acta Ecologica Sinica,2013,33(16):4878- 4884.