Measurement of morphological features of Oncomelania hupensis shells in Yunnan Province

Abstract

Objective To investigate the morphological variation of Oncomelania hupensis shells in Yunnan Province, so as to provide insights into the understanding of O. hupensis genetic evolution and control.

Methods According to the O. hupensis density, geographical location, altitude, water system and environmental type, 12 administrative villages were sampled from 10 schistosomiasis-endemic counties (districts) in 3 prefectures (cities) of Yunnan Province as snail collection sites. From December 2021 to January 2022, about 200 snails were collected from each collection site, among which thirty adult snails (6 to 7 spirals) were randomly selected from each site, and the 11 morphological indexes of snail shells were measured and subjected to cluster analysis and principal component analysis.

Results Of O. hupensis snails from 12 localities of Yunnan Province, the longest shell (7.33 mm) was detected in snails from Yongle Village, Eryuan County, with the shortest (4.68 mm) in Dongyuan Village, Gucheng District, and the largest angle of apex (59.47°) was measured in snails from Caizhuang Village, Midu County, with the smallest (41.40°) in Qiandian Village, Eryuan County. The mean coefficient of variation was 9.075% among O. hupensis snails from 12 localities of Yunnan Province, with the largest coefficient of variation seen in the thickness of the labra brim (29.809%). Among O. hupensis snails from 12 localities of Yunnan Province, the mean Euclidean distance was 2.26, with the shortest Euclidean distance seen between O. hupensis snails from Qiandian Village of Eryuan County and Wuxing Village of Dali City (0.26), and the largest found between O. hupensis snails from Caizhuang Village of Midu County and Cangling Village of Chuxiong County (8.17). Cluster analysis and principal component analysis classified O. hupensis snails from 12 localities of Yunnan Province into three categories, including the O. hupensis snail samples from Caizhuang Village of Midu County, O. hupensis snail samples from Cangling Village of Chuxiong County, and O. hupensis snail samples from Qiandian Village of Eryuan County, Wuxing Village of Dali City, Yangwu Village of Yongsheng County, Xiaoqiao Village of Xiangyun County, Yongle Village of Eryuan County, Xiaocen Village of Dali City, Anding Village of Nanjian County, Dongyuan Village of Gucheng District, Lianyi Village of Heqing County, and Dianzhong Village of Weishan County. The variations in these three categories of snail samples were mainly measured in the principal component 2 related to the angle of apex and the thickness of the labra brim.

Conclusion The variations in the Euclidean distance and morphological features of shells of O. hupensis from 12 localities of Yunnan Province gradually rise with the decrease in the latitude of the collection sites. The angle of apex is an indicator for the growth of O. hupensis whorl.

Abstract

［摘要］ 目的 研究云南省钉螺螺壳形态学变异, 为钉螺遗传进化研究和控制提供依据。 方法 在云南省现有钉螺分 布区, 综合考虑钉螺密度、地理位置、海拔、水系、环境类型等多个因素后, 选取 3 个州 (市) 10 个血吸虫病流行县 (市、区) 12 个行政村作为钉螺采集点。2021 年 12 月至 2022 年 1 月, 在每个采集点采集约 200 只钉螺, 随机选取其中 30 只成年钉 螺 (螺旋数 6~7 个), 对钉螺的 11 个螺壳形态学性状指标进行测量, 并进行聚类分析和主成分分析。 结果 12 个钉螺样 本群中, 壳高最长的钉螺样本采自洱源县永乐村, 为 7.33 mm; 最短的样本采自古城区东元村, 为 4.68 mm。壳顶角度最 大的样本采自弥渡县蔡庄村, 为 59.47°; 角度最小的样本采自洱源县前甸村, 为 41.40°; 12 个钉螺样本群的螺壳形态学性 状平均变异系数为 9.075%, 其中以外唇缘厚度变异系数最大, 达 29.809%。12 个钉螺样本群间平均欧式距离为 2.26, 其 中以洱源县前甸村和大理市五星村两地钉螺样本群间欧式距离最小 (0.26), 以弥渡县蔡庄村和楚雄县苍岭村两地样本 群间欧式距离最大 (8.17)。聚类分析和主成分分析均将 12 个钉螺样本群划分为 3 类：弥渡县蔡庄村钉螺样本群, 楚雄县 苍岭村钉螺样本群, 洱源县前甸村、大理市五星村、永胜县杨伍村、祥云县小桥村、洱源县永乐村、大理市小岑村、南涧县 安定村、古城区东元村、鹤庆县莲义村、巍山县甸中村钉螺样本群; 3 类样本群差异主要体现在与壳顶角度和外唇缘厚度 相关的主成分 2 上。 结论 随采集点纬度逐渐减小, 云南省 12 个钉螺样本群螺壳形态指标欧式距离及螺壳形态变异程 度逐渐增加, 壳顶角度可作为反映螺层成长过程的指标之一。