水棲淡水龜在水域生態系中扮演重要角色,在水域環境中所占生物量大,偏雜食及半水棲特性,對水域與陸域間的營養傳輸有極重要貢獻。本研究利用斑龜(Mauremys sinensis)食物組成的研究探討淡水龜在水域生態系所扮演能量傳輸的角色,尤其是在部分半人工的濕地環境。本研究利用胃內含物沖出法採集80個胃內含物樣本,計鑑定出動物性食物類別13個,植物性11個。動物性食物類別出現頻度百分比為75.0%,植物性類別為80.0%。水棲性斑龜屬於機會性攝食策略物種,植物性食物較易由水域或岸邊環獲取的類別頻度較高,包括種子/果實(25.0%)、水竹葉 (Murdannia keisak)(18.8%)、絲藻(Filamentous algae)(17.5%)、火燄木葉(Spathodea campanulata leaves)(10.0%);動物性食物主要為優養化水域環境常見的類群,包括水生昆蟲的劃蝽(Corixidae) (28.8%)、仰泳蝽(Notonectidae) (12.5%)、蚋科(Simuliidae larva)幼蟲(10.0%)及來自陸域環境的螞蟻(Formicidae)(15.0%)。植物性食物的體積占比則以絲藻(23.1%)、火燄木葉(18.1%)及水竹葉(17.2%);動物性食物的體積占比為螞蟻(9.9%)。在植物性食物的相對重要性指數為絲藻(27.0)、水竹葉(21.7)、火燄木葉(12.1)、種子/果實(11.0),而動物性食物的相對重要性指數為螞蟻(9.9%)、劃蝽(9.49%)。雄龜與雌龜的食物組成寬度分別為0.330及0.136,而重疊度為0.26,顯示雄龜和雌龜食物組成差異大。在水量相對穩定的除污水域環境,雄龜與雌龜的胃內含物組成有不同的動植物食物類別,淡水龜被認為有助控制水域環境中部分病媒或優勢物種過度增長,由本研究結果亦支持生物量大的斑龜族群對維持優養或人工除污濕地水域環境動植物組成平衡,避免少數優勢物種過度增生,尤其是具有公共衛生風險動物類群。
Freshwater turtles play an important role in most aquatic ecosystems; due to large biomass, omnivorous and semi-aquatic habit, they contribute greatly to nutrient and energy transfer between aquatic and terrestrial environments. The studies of food composition can provide important clues in ecological roles of freshwater turtles in semi-artificial aquatic habitats, such as treatment wetlands. In this study, 80 food content samples of M. sinensis were obtained by using stomach flushing and 24 food items identified. The results of food analysis indicated that M. sinensis was opportunistic and omnivorous, ingesting 11 plant (80.0% in occurrence) and 13 animal items (75.0%). They consumed the common plant foods in water bodies or on bank, including plant seed/ fruit (25.0%), Murdannia keisak (18.8%), algae (17.5%) and Spathodea campanulata (10.0%); in animals, they ingested the common invertebrate items in nutrient-rich water bodies, including corixidine insects (28.8%), notonectine insects (12.5%), blackfly larvae (Simuliidae) (10.0%). In the percentage of total volume, this turtle ingested filamentous algae (23.1%), S. (18.1%) and M. keisak (18.8%) in plants and ants (9.9%) in animals. According to index of relative importance (IRI), their important food items were filamentous algae (27.0), M. keisak (21.7), S. campanulata (12.1) and seed/ fruit (11.0) in plants and ants (9.9) and corixidine insects (9.49%) in animals. The dietary breath of males (0.330) was larger than that of females (0.136), indicating that male M. sinensis ingested more diverse food resources. The value of dietary overlap was 0.26, suggesting that there was partitioning in utilization of food resources. As the aquatic environment in treatment wetlands was relatively stable, there were no intersexual or seasonal differences in the food composition of M. sinensis. Freshwater turtles were regarded as good candidate in the control of disease-vector insects or overgrowth of nuisance species in aquatic habitats. My results suggest that stable M. sinensis population would be helpful in the management of treatment wetlands, controlling overgrowth of pesky or harmful species in eutrophic waters, especial the species with high risks in public health.