Influence of light regimes on phyllosomal growth and timing of moulting in Thenus orientalis (Lund) (Decapoda: Scyllaridae)

Abstract

Newly hatched phyllosomas of Thenus orientalis (Lund) were successfully reared under conditions of natural light (D/L), continuous dark (24D) or continuous light (24L). Survival, duration of intermoult periods, moult increment in total body length, and timing of moulting through larval stages were monitored. Survival and growth under 24L was lower than that under D/L and 24D; this may be a result of decreased phyllosomal feeding activity under 24L, caused by a photopositive reaction drawing the phyllosomas away from food at the bottom. There were no differences in phyllosomal development under D/L and 24D. When phyllosomas were reared under D/L, moulting was synchronized and occurred around dawn. Moulting of those reared under 24D or 24L was not synchronized and occurred irregularly. These results indicate that, in phyllosomas, light regime influences the endogenous rhythmic function responsible for the regulation of moulting time. When phyllosomas reared under D/L metamorphosed to the nisto stage, synchronized moulting switched from dawn to after dusk. Furthermore, nistos and juveniles moulted only nocturnally, with apparent synchronicity. This suggests that the switch from planktonic to benthic lifestyle, with consequent different predation pressures, necessitates a change in the timing of moulting.

Review

“…Even those species with the shortest larval development period (c. 4 weeks, Coutures et al 2002, 10 Michel (1968, "Mikami & Greenwood (1997b), 12 Robertson (1979), " Robertson (1969a), 14 Baisre (1994), 15 Mikami & Takashima (1993), 16 Holthuis (2002), 17 Holthuis (1985), 18 Rothlisberg et al (1994), 19 Takahashi & Saisho (1978), 20 Ito & Lucas (1990), 21 Mikami & Greenwood (1997a), 22 Lyons (1970), 23 Crosnier (1972), 24 Johnson (1968), 25 Ritz & Thomas (1973), 26 Dotsu et al (1966), 27 Higa & Saisho (1983), 28 Prasad et al (1975), 29 Berry (1974), 30 Johnson (1971b), 31 Barnett et al (1984), 32 Barnett et al (1986), 33 Olvera Limas & Ordonez Alcalá (1988), 34 Robertson (1969b), 35 Phillips et al (1981), 36 Marinovich et al (1994), 37 Yeung & McGowan (1991), 38 Atkinson & Boustead (1982), 39 McWilliam & Phillips (1983), 40 Inoue et al (2001), 41 Ritz (1977), …”

Slipper Lobsters

“…However, under conditions of total darkness there was no effect on growth of phyllosomas of P. homarus or T. orientalis phyllosomas and nistos, suggesting that light may modify their behaviour, but does not necessarily affect their metabolic rate (Mikami & Greenwood 1997a ). The growth and survival of phyllosoma of T. orientalis (Mikami & Greenwood 1997b ) was not affected when exposed to natural light and 24 hour darkness, but were lower for those larvae exposed to 24 hour light. Moulting was synchronised in natural light and occurred around dawn while under 24 hour darkness and light it was erratic and occurred irregularly (Mikami & Greenwood 1997b ).…”

“…The growth and survival of phyllosoma of T. orientalis (Mikami & Greenwood 1997b ) was not affected when exposed to natural light and 24 hour darkness, but were lower for those larvae exposed to 24 hour light. Moulting was synchronised in natural light and occurred around dawn while under 24 hour darkness and light it was erratic and occurred irregularly (Mikami & Greenwood 1997b ). Light may modify the behaviour of phyllosoma, but may not modify their metabolism (Mikami & Greenwood 1997b ).…”

“…Moulting was synchronised in natural light and occurred around dawn while under 24 hour darkness and light it was erratic and occurred irregularly (Mikami & Greenwood 1997b ). Light may modify the behaviour of phyllosoma, but may not modify their metabolism (Mikami & Greenwood 1997b ). …”

Ozonation of seawater improves the survival of larval southern rock lobster, Jasus edwardsii, in culture from egg to juvenile

“…This heightened sensitivity to OBP coincided with the first appearance of external gills buds (Lesser, 1978). An attempt to briefly introduce ozonated water for only 3 h daily in the afternoons, outside the putative moulting period, still resulted in deformities because, unlike some other lobster species where moulting occurs consistently around dawn (Mikami and Greenwood, 1997), J. edwardsii phyllosoma may moult at other times and are not noted for close synchrony associated with photoperiod (Ritar and Smith, unpublished data). Even though phyllosoma become more sensitive to the adverse effects of ozonation at later stages of development, it appears that they become more resistant to microbial infection and contamination.…”