A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, Russia.
Sci Rep. 2024 Aug 22;14(1):19495. doi: 10.1038/s41598-024-67622-5.
The presence of different types of larvae within the same class suggests a broad ecological diversification. A clear comparison of bivalve larval nervous systems would give a broader view on evolutionary and ecological picture of the clade in question. The present study focused on the neurodevelopment in two bivalve species with different larval types: pericalymma of Acila insignis (Bivalvia: Protobranchia) and veliger of Spisula sybillae (Bivalvia: Autobranchia). It was shown that the pioneer dorsal and ventral neurons in S. sybillae appear at the trochophore stage. Subsequently, future three paired ganglia are developed on the nerve cords in pediveliger. In the pericalymma of A. insignis, serotonin- and FMRFamide-positive cells are found in the apical organ (AO), as well as two pairs of FMRFamide positive neurons are detected on dorsal and posterior part of pericalymma. A comparative analysis showed significant differences in the larval neuromorphology between veliger and pericalymma. In contrast to the S. sybillae veliger, the nervous system of the A. insignis pericalymma is simple, likely due to its different lifestyle. The larval nervous system in the species under study has features characteristic of Lophotrochozoa and Spiralia.
同一纲内存在不同类型的幼虫表明其具有广泛的生态多样化。对双壳类幼虫神经系统进行明确比较，将更全面地了解该研究类群的进化和生态图景。本研究集中于两种具有不同幼虫类型的双壳类物种的神经发育：Acila insignis 的后纤毛幼虫（双壳纲：原鳃亚纲）和 Spisula sybillae 的担轮幼虫（双壳纲：后鳃亚纲）。结果表明，Spisula sybillae 的先驱背侧和腹侧神经元出现在担轮幼虫阶段。随后，在足丝幼虫的神经索上发育出未来的三个成对神经节。在 Acila insignis 的后纤毛幼虫中，在顶器（AO）中发现了血清素和 FMRF 肽阳性细胞，并且在后纤毛幼虫的背侧和后部分别检测到两对 FMRF 肽阳性神经元。比较分析表明，担轮幼虫和后纤毛幼虫的幼虫神经形态存在显著差异。与 Spisula sybillae 的担轮幼虫相比， Acila insignis 的后纤毛幼虫的神经系统较为简单，这可能与其不同的生活方式有关。研究物种的幼虫神经系统具有环节动物和螺旋动物的特征。
