RNAi Reveals Role of Insulin-Like Androgenic Gland Hormone 2 (IAG2) in Sexual Differentiation and Growth in Hermaphrodite Shrimp

<jats:p>Insulin-like androgenic gland hormone (IAG) is the most widely known hormone that regulates sexual differentiation in crustaceans. Previously, a transcriptome study described two transcripts of IAGs (<jats:italic>Lvit-IAG1</jats:italic> and <jats:italic>Lvit-IAG2</jats:italic>) in the peppermint shrimp <jats:italic>Lysmata vittata</jats:italic>, a species characterized by a rare reproductive system of protandric simultaneous hermaphroditism (PSH). Herein, we explored the function of <jats:italic>Lvit</jats:italic>-IAG2 via RNA interference (RNAi) experiments, and then compared the functional differences between the two IAGs. We demonstrated that <jats:italic>Lvit</jats:italic>-IAG2 positively regulated the expression of crustacean hyperglycemic hormone (<jats:italic>Lvit-CHH</jats:italic>) in eyestalk ganglion but exhibited no significant effect on the expression of gonad-inhibiting hormone (<jats:italic>Lvit-GIHs</jats:italic>) and crustacean female sex hormone (<jats:italic>Lvit-CFSHs</jats:italic>). Besides, <jats:italic>Lvit-IAG2</jats:italic> gene knockdown caused degeneration in appendices masculinae (AM) and suppressed germ cells at the secondary spermatocyte stage. Moreover, silencing the <jats:italic>Lvit-IAG2</jats:italic> gene impeded ovarian development, including smaller previtellogenic oocytes, and lower expression of <jats:italic>vitellogenin</jats:italic> (<jats:italic>Lvit-Vg</jats:italic>) gene in hepatopancreas and <jats:italic>vitellogenin receptor</jats:italic> (<jats:italic>Lvit-VgR</jats:italic>) gene in the ovarian region. Notably, silencing the <jats:italic>Lvit-IAG2</jats:italic> gene impeded individual growth of the species. Collectively, findings from this study demonstrate that <jats:italic>Lvit</jats:italic>-IAG2 and <jats:italic>Lvit</jats:italic>-IAG1 coordinatively function to modulate sexual differentiation in <jats:italic>L. vittata</jats:italic>; meanwhile, <jats:italic>Lvit</jats:italic>-IAG2 stimulates the growth of the PSH species.</jats:p>