In penaeid shrimp, cortical rods (CRs) are formed in peripheralcrypts of the oocyte after completion of yolk accumulation;subsequently the CRs are utilized as a source of jelly materialsthat surround fertilized eggs. In our previous study, of five majorcomponents, three CR proteins displayed quite similar immunologicalcharacteristics. In this study, cDNA sequences and developmentalexpression profiles at both transcriptional and proteinlevels were examined to elucidate the molecular characteristicsof CR proteins and the process of CR formation. SequencingcDNAs exhibited the presence of three related forms thathave identical sequences except for the loss of 246 and 369 bpin medium and short forms, respectively, suggesting that a singlegene generates three transcriptional variants corresponding tothe three CR proteins. Their deduced amino acid sequences revealedsimilarities to those of extracellular matrix proteins in athrombospondin (TSP) 3,4/cartilage oligomeric protein family,and thereby the CR proteins were designated mjTSP. Semiquantitativeanalysis by real-time polymerase chain reaction revealedthe presence of mjTSP transcripts, at similar levels, in immature,vitellogenic, and mature ovaries. Furthermore, in situ hybridizationlocalized the majority of transcripts in previtellogenic oocytesin ovaries at all developmental stages. By theWestern blot,on the other hand, mjTSP proteins were undetectable in immatureovaries but became obvious at the early vitellogenicstage. The immunosignals were enhanced during vitellogenicstages and maintained a high intensity in mature ovaries. Thus,transcription, translation of mjTSP, and formation of the CRstructure occurred at different stages of ovarian development.