EFFECT OF PHOTOPERIOD ON DEVELOPMENT AND METAMORPHOSIS OF SPINY LOBSTER (SAGMARIASUS VERREAUXI)

This study examined the effects of photoperiod on the growth, survival, feeding and moulting in early and late stage spiny lobster, Sagmariasus verreauxi, phyllosoma. In the first experiment, the effects of five photoperiods (0, 6, 12, 18 and 24 h photophase) were examined in the culture of larvae from hatch to instar stage 5. Phyllosoma at 6 h photophase grew larger, however, fewer survived. Phyllosoma at 6 h photophase also ingested fewer Artemia which suggested that the observed inverse relationship between growth and survival may have been a result of cannibalism. Phyllosoma cultured in continuous light were significantly smaller, probably due to an imbalance in energy uptake and consumption due to prolonged activity. Moult increment among all photoperiods was similar. These results suggest that a light dark regime is important for early stage phyllosoma and a photophase of 12 to 18 h is recommended for culture. In the second experiment, the effects of four photoperiods (6, 12, 18 and 24 h photophase) were examined in the culture of late stage larvae to metamorphosis. Photoperiod did not significantly affect survival or growth, however, long day length triggered phyllosoma to progress through metamorphosis sooner. At 24 and 18 h photophase 28 and 19 % more larvae metamorphosed to pueruli, respectively, than at 12 h photophase. Metamorphosis survival was also best at 18 h photophase. This provides the first evidence that metamorphosis in rock lobsters can be influenced by an exogenous cue. It is hypothesized that metamorphic moult is regulated by photoperiod so that it occurs at the most propitious time of the year. This finding is important in propagation as it may allow the initiation of metamorphosis sooner, reducing the duration of the resource intensive phyllosoma rearing phase.