Bursa tract diverticulum in the hermaphroditic land snail Arianta arbustorum (Stylommatophora: Helicidae): Morphology, function, and evolutionary implications
Bursa tract diverticulum in the hermaphroditic land snail Arianta arbustorum (Stylommatophora: Helicidae): Morphology, function, and evolutionary implications
复制标题
雌雄同体陆地蜗牛 Arianta arbustorum 中的囊管憩室（Stylommatophora：Helicidae）：形态、功能和进化意义
作者：
K. Beese;K. Beier;B. Baur
囊性憩室广泛存在于肺柱头蝇雌雄同体生殖系统的雌性部分。然而，憩室的超微结构尚不清楚，只有零星的证据表明该器官具有溶解精囊的功能。在本研究中，我们观察了同时雌雄同体的陆地蜗牛Arianta arbustorum交配后不同时间间隔憩室的超微结构和组织学、组织化学和形态计量学的变化。这种蜗牛的憩室是一个突出的器官，由管腔柱状上皮组成，周围有一层厚厚的结缔组织。在交配过程中，憩室作为精囊摄取的部位。在憩室管腔内，精囊壁溶解或至少部分被破坏。消化的物质被上皮细胞吸收，并积聚在结缔组织的软体动物特异性细胞中，即所谓的结缔组织细胞。交配后，憩室总直径明显增大，在交配后12 h达到最大值，同时憩室壁和憩室上皮厚度减小。与蜗牛大小相比，憩室的长度表现出正异速性和高表型变异，表明憩室存在定向性选择。我们认为，在雄性和雌性功能的不同进化利益所施加的选择压力下，A. arbustorum的憩室已经进化。j . Morphol。©2006 Wiley‐Liss, Inc。
A bursa tract diverticulum is widespread in the female part of the hermaphroditic reproductive system of stylommatophoran pulmonates. However, the ultrastructure of the diverticulum is unknown and there is only anecdotal evidence for a spermatophore‐dissolving function for this organ. In the present study, we examined the ultrastructure of the diverticulum and investigated histological, histochemical, and morphometric changes at different time intervals after mating in the simultaneously hermaphroditic land snail Arianta arbustorum. The diverticulum in this species of snail is a prominent organ, consisting of a luminal columnar epithelium surrounded by a thick layer of connective tissue. During mating, the diverticulum functions as the site of spermatophore uptake. Within the lumen of the diverticulum the spermatophore wall is dissolved or at least partly broken down. The digested material is taken up by epithelial cells and accumulated in molluscan‐specific cells of the connective tissue, the so‐called rhogocytes. Subsequent to copulation, the total diameter of the diverticulum increases markedly, reaching a maximum size 12 h after mating, while at the same time the thicknesses of the diverticulum wall and diverticulum epithelium decrease. The length of the diverticulum shows a positive allometry and a high phenotypic variation compared to snail size, which suggests that the diverticulum is under directional sexual selection. We propose that the diverticulum in A. arbustorum has evolved in response to selection pressures imposed by divergent evolutionary interests between male and female function. J. Morphol. © 2006 Wiley‐Liss, Inc.