Kengne-Fokam Alvine C, Nana-Djeunga Hugues C, Djuikwo-Teukeng Félicité F, Njiokou Flobert
University of Yaoundé 1, Parasitology and Ecology Laboratory, Faculty of Science, PO Box 812, Yaoundé, Cameroon.
Centre for Research on Filariasis and other Tropical Diseases (CRFilMT), PO Box 5797, Yaoundé, Cameroon.
Parasit Vectors. 2016 Jan 6;9:10. doi: 10.1186/s13071-015-1285-4.
Biomphalaria pfeifferi and Biomphalaria camerunensis are intermediate hosts of the trematode Schistosoma mansoni. Up till now, very scanty data report the life history traits of these freshwater snails. This study was therefore conducted to provide further knowledge on the mating system of these two S. mansoni intermediate hosts in Cameroon. The study was performed following a three-step experimental design as follows: (i) for each species, a sample of young snails (G1), virgin and sexually mature was constituted and divided into two groups; (ii) in the first group, individuals were maintained isolated for the evaluation of the impact of self-fertilization on life history traits while in the second group, individuals were paired for few hours for the evaluation of cross-fertilization impact; (iii) in each group, fitness parameters (fecundity of G1 snails and survival of G2 offspring) were monitored during one month.
The sexual maturity (age at first egg-laying) was reached, on average, at 63.9 (sd: 3.0) and 103.7 (sd: 36.6) days for B. pfeifferi and B. camerunensis, respectively. Copulation was observed in all paired individuals in both species. In B. pfeifferi, the fecundity (number of egg capsules and eggs) of young G1 individuals and survival of G2 offspring on D0 and D8 were similar between selfing and outcrossing individuals, and a very low inbreeding depression (0.063) was observed. In B. camerunensis, the fecundity of outcrossed individuals was significantly higher than that of selfed individuals. The hatching rate was significantly higher and the incubation time significantly shorter for cross-fertilized eggs as compared with self-fertilized eggs, and a high inbreeding depression (0.71) was observed.
These findings may explain the high adaptability to more diverse and inconstant habitats, as well as the better compatibility of B. pfeifferi to S. mansoni compared with B. camerunensis, and may support the sustainability of S. mansoni life cycle where this intermediate host prevails.
费氏双脐螺和喀麦隆双脐螺是曼氏血吸虫的中间宿主。迄今为止，关于这些淡水螺生活史特征的数据非常稀少。因此，本研究旨在进一步了解这两种曼氏血吸虫中间宿主在喀麦隆的交配系统。该研究按照以下三步实验设计进行：（i）对于每个物种，构建一组年轻的（G1）、未交配且性成熟的蜗牛样本，并将其分为两组；（ii）在第一组中，将个体单独饲养，以评估自体受精对生活史特征的影响，而在第二组中，将个体配对数小时，以评估异体受精的影响；（iii）在每组中，在一个月内监测适合度参数（G1蜗牛的繁殖力和G2后代的存活率）。
费氏双脐螺和喀麦隆双脐螺达到性成熟（首次产卵年龄）的平均天数分别为63.9（标准差：3.0）天和103.7（标准差：36.6）天。在两个物种的所有配对个体中均观察到交配现象。在费氏双脐螺中，自体受精和异体受精个体的年轻G1个体的繁殖力（卵囊和卵的数量）以及D0和D8时G2后代的存活率相似，并且观察到非常低的近亲繁殖衰退（0.063）。在喀麦隆双脐螺中，异体受精个体的繁殖力显著高于自体受精个体。与自体受精的卵相比，异体受精的卵孵化率显著更高，孵化时间显著更短，并且观察到较高的近亲繁殖衰退（0.71）。
这些发现可能解释了费氏双脐螺比喀麦隆双脐螺对更多样化和不稳定栖息地具有更高的适应性，以及与曼氏血吸虫更好的兼容性，并且可能支持在这种中间宿主占优势的地区曼氏血吸虫生命周期的可持续性。
