Sexual maturity and environmental sex determination in the white-striped cleaner shrimp Lysmata amboinensis

Attempts to close the life-cycle of the white-striped cleaner shrimp Lysmata amboinensis (De Man, 1888), a high-value marine ornamental species, in captivity, have heightened in recent years. As a protandric simultaneous hermaphrodite (PSH), individuals develop as males (male phase, MPs), then change to hermaphrodites (SHs) and function as both sexes during the reproductive cycle. Knowledge of male size at sexual maturity and of sex change timing would benefit the establishment of hatchery-based pairs and contribute to future captive production of the species. Lysmata amboinensis MPs used in this study were sexually mature at an average 34.0 mm total length. Regarding the SH size groups, the medium and small SHs produced a similar number of larvae, whereas viable fecundity for the large SH group was approximately three times higher, indicating fecundity increases with body size in L. amboinensis. Brood loss was noted as having a severe impact on larval production, with potential causes discussed. The timing of sex change could be manipulated by exposing the shrimp to different social conditions, indicating “environmental sex determination”. Male-phase shrimp reared on their own changed at an average 37.1 mm, which was considered the “default” size at sex change. The “focal MPs” paired with “similar-sized MPs” changed sex at a smaller size than the “default”, while the “non-focals” changed sex at a slightly larger size than the “default”. “Focal MPs” paired with a “larger MP” changed at a larger size than the “default”, and it was the “larger MPs” in the treatment that changed first to SHs. The “non-focal MPs” in the treatment of “similar-sized MPs” changed sex faster than the “non-focals” in the “different-sized” pairs. Finally, the “MPs” paired with “SHs” changed at a smaller size than the “default”. The observed patterns are discussed in terms of reproductive opportunities for “lowdensity” species.