The germline is a key feature of sexual animals and the ways in which it separates from the soma differ widely across Metazoa. However, at least at some point during germline differentiation, some cytoplasmic supramolecular structures (collectively called germ plasm-related structures) are present and involved in its specification and/or differentiation. The factors involved in the assembly of these granular structures are various and non-ubiquitous among animals, even if some functional patterns and the presence of certain domains appear to be shared among some. For instance, the LOTUS domain is shared by Oskar, the Holometabola germ plasm master regulator, and some Tudor-family proteins assessed as being involved in the proper assembly of germ granules of different animals. Here, we looked for the presence of LOTUS-containing proteins in the transcriptome of Ruditapes philippinarum (Bivalvia). Such species is of particular interest because it displays annual renewal of gonads, sided by the renewal of germline differentiation pathways. Moreover, previous works have identified in its early germ cells cytoplasmic granules containing germline determinants. We selected the orthologue of TDRD7 as a candidate involved in the early steps of germline differentiation through bioinformatic predictions and immunohistological patterning (immunohistochemistry and immunofluorescence). We observed the expression of the protein in putative precursors of germline cells, upstream to the germline marker Vasa. This, added to the fact that orthologues of this protein are involved in the assembly of germ granules in mouse, zebrafish, and fly, makes it a worthy study unit for investigations on the formation of such structures in bivalves.

生殖系是有性动物的一个关键特征，它与体细胞分离的方式在后生动物中差异很大。然而，至少在种系分化过程中的某个时刻，存在一些细胞质超分子结构（统称为种质相关结构）并参与其特化和/或分化。参与这些颗粒结构组装的因素在动物中是多种多样的，并不普遍存在，即使某些功能模式和某些域的存在似乎在某些人之间共享。例如，LOTUS 域由 Oskar、Holometabola 种质主调节器和一些被评估为参与不同动物胚芽正确组装的 Tudor 家族蛋白共享。这里，菲律宾蛤仔（双壳纲）。这种物种特别令人感兴趣，因为它显示性腺的年度更新，伴随着生殖细胞分化途径的更新。此外，先前的工作已在其早期生殖细胞胞质颗粒中鉴定出含有生殖系决定簇的物质。我们通过生物信息学预测和免疫组织学模式（免疫组织化学和免疫荧光）选择了 TDRD7 的直向同源物作为参与生殖系分化早期步骤的候选物。我们观察到该蛋白质在种系细胞的假定前体中的表达，位于种系标记 Vasa 的上游。再加上这种蛋白质的直向同源物参与小鼠、斑马鱼和苍蝇中胚芽颗粒的组装这一事实，使其成为研究双壳类动物中此类结构形成的一个有价值的研究单位。