- The vasa gene encodes an ATP- dependent RNA helicase belonging to the DEAD-box family that, in many organisms, is specifically ex- pressed in germline cells throughout the life cycle. In this study we first cloned Pacific white shrimp (Litopenaeus vannamei) partial cDNAs of two mem- bers of the DEAD-box family, one belonging to the vasa subfamily (Lv-Vasa) and the other to the PL10 subfamily (Lv-PL10). Examination of their spatial expression pattern in adult tissues revealed that Lv- Vasa is restricted to the gonads, whereas Lv-PL10 is found in gonads as well as in somatic tissues. Next, we cloned the full-length shrimp vasa cDNA and found that Lv-Vasa encoded a protein with a DEAD-like helicase domain followed by a helicase superfamily C-terminal domain. In addition, Lv-Vasa encoded N-terminal three repeats of the C2HC-type zinc finger domain, a motif encoded by vasa genes of several crustaceans and several other invertebrate organisms. In situ hybridization of ovarian sections showed that the Lv-Vasa transcript is localized to the cytoplasm of the oocyte throughout oogenesis. The abundance of Lv-Vasa mRNA in mature oocytes suggests a maternal contribution for the developing embryo. It is demon- strated that the vasa homolog from L. vannamei is a gonad specific germline cell marker that could be exploited to enhance our understanding of develop- mental and reproductive processes in the germline of this economically important shrimp. Mol. Reprod. Dev. 74: 172-177, 2007. 2006 Wiley-Liss, Inc.