. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 106 CHARMANTIER ET Figure 4. Salinity tolerance in lar\al il ) and post-Ian al (PL) Pen- aeus japonicus at 25°C. Variations in LS50 in %o and mosm-kg"1 ac- cording to larval/post-larval stages and days of development. Each point represents the mean value of at least two determinations from 10 animals, with 95^ confidence interval. N. nauplius: Z. zoea: M. mysis; PI. post-larval stage. Closed circles: 24 h LS50; open circles: 48 h LS50; open triangles: 96 h LS50. PL10. P20 (24 h LS50 about 200 mosm-kg'1 or ?%„). The
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 106 CHARMANTIER ET Figure 4. Salinity tolerance in lar\al il ) and post-Ian al (PL) Pen- aeus japonicus at 25°C. Variations in LS50 in %o and mosm-kg"1 ac- cording to larval/post-larval stages and days of development. Each point represents the mean value of at least two determinations from 10 animals, with 95^ confidence interval. N. nauplius: Z. zoea: M. mysis; PI. post-larval stage. Closed circles: 24 h LS50; open circles: 48 h LS50; open triangles: 96 h LS50. PL10. P20 (24 h LS50 about 200 mosm-kg'1 or ?%„). The 48 h LS50. higher than the 24 h LS50 by 20-150 mosm-kg"1 (), followed the same pattern of variation. Molting between larval stages was possible in 0%, about 50%, and 60-100% of the larvae in media of 800 mosm - kg"' (, , ), respectively. P. japonicus: osmoregulatory ability Adaptation time. After a rapid transfer from seawater (1050 mosm-kg"' or ) to a dilute medium (500 mosm-kg"' or 17%o), the hemolymph osmotic pressure stabilized in 1 h in stage zoea 3, 3 h in fourth post-larval stage (PL4), and 6 h in stage PL 10 (Fig. 5). In all subse- quent experiments, we kept the animals 6-24 h in each medium before sampling. Osmoregulation. Larval stages (zoea 2 and 3, mysis 1- 1) h\per-osmoconformed over the whole range of tested salinities: the osmotic pressures of hemolymph and me- dium differed by about 10-40 mosm-kg '. In stage mysis 3, which lasted 2 days, regulation was slightly more hy- per-osmotic towards the end of the stage, , in prcmolt animals ' . 6). At the end of the larval period, most of the animal lied in the dilute media and the few survi- vors teni1 iismoconform. The pattern o smoregulation changed after meta- morphosis. Starting I n the end of first post-larval stage (PL1) which lasted 1 the regulation shifted to slightly hyper-osmotic ii •lute media and hypo-osmotic in seawater. Hyper- and i po-osmotic
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