The peppermint shrimp Lysmata vittata (Caridea: Hippolytidae) is a marine caridean shrimp popular in marine aquarium trade, the species is known to display the sexual system of protandric simultaneous hermaphrodite. In this study, based on captive bred specimens, the complete ontogenetic gonadal development of L. vittata was studied both morphologically and histologically, from newly settled juveniles until they reached euhermaphrodite phase. It was found that in all specimens examined (carapace length: 1.8 - 8.5 mm), including the newly settled juveniles, possessed ovotestes, which comprised of an anterior ovarian and a posterior testicular part. Based on both morphological (e.g. size, color and shape) and histological features (e.g. oogenesis and spermatogenesis), four gonadal developmental stages were defined and described for L. vittata. From Stage I to III, the testicular part of the gonad became gradually mature but the ovarian part was still immature, which is defined as the male phase. Surprisingly, it was found that even in the newly settled juveniles, a small amount of spermatozoa was presented in the testicular part of their gonads. At Stage IV, both the testicular part and the ovarian part were mature and hence is defined as euhermaphrodite phase. This is the first time that complete ontogenetic gonadal and external sexual character development have been described and staged for a species from the genus Lysmata from newly settled juveniles to euhermaphrodite phase.
Key words: ontogenetic gonad development; Lysmata vittata; protandric simultaneous hermaphrodite; gonadal developmental stages