Putative germ granular material is inherited by the primordial germ cell in Marsupenaeus japonicus (Spence Bate, 1888) (Decapoda: Dendrobranchiata: Penaeidae)

A putative germ granule, termed an intracellular body (ICB), has been identified in penaeid shrimps, where it is inherited from a 2-cell stage blastomere to one of the mesendoblasts at the 32-cell stage. It is hypothesized that this structure may be a germ granule and therefore a marker of germ-cell fate. Fluorescence and electron microscopy has been previously used to follow the fate of the ICB in the first cleavages to early gastrulation. The ICB contained RNA and was composed of granules and vesicles in the cortical cytoplasm. These results are consistent with the ultrastructure of germ granules described in other species of shrimps, supporting the hypothesis that the ICB may be a germ granule in penaeids. The aim of the present research was to continue tracing the putative germ granule in Marsupenaeus japonicus (Spence Bate, 1888) through later stages of gastrulation to the hypothesized primordial germ cell. Neither Vasa nor Nanos antibodies stained the ICB, so TEM was used to follow its fate. Electron dense, granular material was traced from one mesendoblast at early gastrulation to the hypothesized primordial germ cell at late gastrulation. We interpret this as remnants of the ICB, consistent with its identity as germ-granule material.