台灣海域瑞氏海豚生長及骨骼成熟模式

Patterns of growth and maturation of the skeleton in Risso's dolphins, Grampus griseus, from Taiwanese waters

陳瑩(Ing Chen)

指導教授 ： 周蓮香

共同指導教授 ： Alastair Watson(Alastair Watson)

國立臺灣大學/生命科學院/生態學與演化生物學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.02921

摘要

瑞氏海豚為一種中小型齒鯨，廣泛分布於全球溫帶及熱帶大洋水域，同時也是台灣東部海域最常見的鯨豚種類之一。 由於他們的生活史資料闕如，本研究之目的為由判定牙齒年齡及頭骨、胸鰭骨骼成熟度，來探究台灣瑞氏海豚族群之年齡、體長及骨骼成熟度之間的關係。 研究材料來自1994年至2008年間測量並解剖之死亡擱淺或誤捕致死海豚99隻（體長範圍124 – 290公分）。 骨骼成熟度由67隻胸鰭（來自34隻海豚）的X光片顯影上橈骨（radius）及尺骨（ulna）末端軟骨骨化癒合（epiphyseo-metaphyseal fusion）程度，以及33顆處理過之乾燥頭骨上20個骨骼相接處（sutures/synchondroses/symphysis）癒合程度評估之。 28隻海豚年齡透過牙齒組織切片的生長輪紋（growth-layer-groups, GLG）判定。 初步結果發現台灣的瑞氏海豚在體長的成長模式上沒有明顯性別差異，雌性性成熟估計始於體長240 – 255公分、雄性則為253 – 265公分，雌雄性成熟年齡始於約10歲左右; 性成熟體型略小於日本及南非的族群，而遠小於北大西洋族群。 當海豚胸鰭長度停止生長時，尺骨及橈骨末端軟骨完成骨化癒合，此時其體長介於248 – 255公分，推測當時約為性成熟年齡。 在胸鰭骨骼成熟過程中橈骨與尺骨末端的發育不完全同步，橈骨先熟於尺骨，但左右胸鰭及性別上並無先後差異。在頭骨方面，發育過程中背後側頭蓋骨（basioccipital-exoccipital synchondrosis and supraoccipital-exoccipital suture）先行癒合，而位於項脊（nuchal crest）之骨骼交接處（fronto-parietal, fronto-interparietal sutures）則較晚癒合; 癒合過程也無左右差異。 本研究建議頭骨項脊上骨骼交界、鼻骨與額骨前緣交界（rostral nasal-frontal suture）和上頷骨與前頷骨交界先端（distal maxilla-incisive suture）處癒合狀態可作為判定性成熟個體之指標，因這些癒合線在體長大於250公分的成熟海豚的頭骨中普遍都已進入高度癒合狀態。

關鍵字

瑞氏海豚 ； 台灣 ； 頭骨 ； 胸鰭 ； 牙齒 ； 生活史 ； 年齡鑑定

並列摘要

Risso’s dolphins (Grampus griseus) are moderately small odontocetes, widely distributed throughout temperate to tropical pelagic regions of the world’s oceans and are one of the most frequently encountered cetaceans in eastern Taiwanese coastal waters. Since their life history is poorly known, the goal of this study was to investigate the maturation of the skull and flipper bones, and to estimate age based on growth layers in tooth sections, and to determine the relationship between the age, body length and skeletal maturity for this Taiwanese population. Ninety-nine carcasses of dead-stranded or incidentally bycaught dolphins were measured and dissected during 1994 – 2008 (total body length, TBL: 124 – 290 cm). Skeletal maturity was assessed by a radiographic examination of the fusion of the distal epiphyseo-metaphyseal junction in the distal radius and ulna of 67 flippers (from 34 dolphins), and by an examination of the fusion stages of 20 sutures/synchondroses/symphysis on 33, cleaned dry skulls. Age was estimated by counting growth-layer-groups in routine histologically prepared tooth sections from 28 dolphins. Preliminary analysis revealed no sexual dimorphism in body length, and the onset of sexually maturity occurred at 240 – 255 cm in females and 253 – 265 cm in males, which was at about 10 years of age for both sexes. Body length at sexual maturity was slightly shorter than those from Japan and South African waters, but much shorter than those from northeast Atlantic Ocean. Cessation of longitudinal flipper growth in epiphyseo-metaphyseal ossification in the distal radius and ulna occurred at 248 – 255 cm TBL, about the age at sexual maturity. The distal radius closed earlier than distal ulna; bilateral asymmetry and sexual dimorphism was not detected. On the skull, the bones of the caudoventral brain case fused early in development (basioccipital-exoccipital synchondrosis and supraoccipital-exoccipital suture), whereas fusion along the nuchal crest (fronto-parietal, fronto-interparietal sutures) occurred later; bilateral asymmetry of the fusion process was not detected. At TBL > 250 cm, advanced fusion occurred along the nuchal crest, rostral nasal-frontal, and distal maxilla-incisive sutures which may be useful indicators of sexual maturity.

並列關鍵字

Grampus griseus ； Risso’s dolphin ； Taiwan ； skull ； flipper ； teeth ； GLG ； life history ； age estimation

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