FISHERY BULLETIN: VOL. 80, NO. 3 



Figure b.—Hyas araneus. C:N (car- 

 bomnitrogen) ratio in larvae fed and 

 starved for different lengths of time. 



8 10 12 U 16 18 20 22 



Age (days) 



Certainly the buildup of the chitin cuticle, and 

 perhaps also the disproportionately strong 

 storage of lipids, contributed to the increase. The 

 subsequent decrease in the C:N ratio suggests 

 that more proteins than other organic constitu- 

 ents were accumlated later. This trend was best 

 visible in the Z-l and megalopa stages; in the 

 latter it was followed by a new increase begin- 

 ning on day 16. This period was identical with 

 that of decreasing biomass (Fig. 3). The curves 

 given in Figure 5 for starved larvae will be dis- 

 cussed below. 



TheC:H ratio remained fairly constant within 

 stages, and it did not differ much among larval 

 instars. The mean values and 95% confidence 

 intervals (weight-based) were 6.67+0.08 in the Z- 

 1 (1980), 6.64±0.26 in the Z-2, and 6.49+0.11 in 

 the megalopa. In field-caught Z-2 larvae and in 

 young crabs mean ratios of 6.66 and 6.67 were 

 found. The ratios in the Z-l and megalopa stages 

 were statistically different from each other 

 (P<0.01). There was also a significant difference 

 (P — 0.002) between the figures in the Z-l from 

 1979 (6.86+0.09) and from 1980 (see above). 



The growth patterns described in Figure 3 do 

 not consider losses due to shedding of exuviae. In 

 order to determine the approximate amount of 

 organic substances cast during molts, occasional 

 analyses of exuviae were carried out (Table 5). 

 Wet weight and DW measurements did not 

 provide useful results, because the amount of 

 water and salt inside the cast could not be 

 accurately determined. The composition of the 

 exuviae corresponded closely to that of its main 

 component, chitin. Deviations from the theoreti- 



cal atomic ratio C:N:H =9:1:14 can partly be 

 explained by analytical inaccuracies (see 95% 

 confidence limits in the megalopa), partly by 

 other biochemical components of exuviae, or by 

 slight chemical changes before sampling and 

 analyzing the casts (partial decomposition). 



The amount of organic matter lost during 

 zoeal molts was far lower than during meta- 

 morphosis to the crab: 4 to 5% versus 19% in N, 6 

 to 9% versus 29% in both C and H (Table 5). 

 Assuming an energy content of ca. 18 J/mg dry 

 organic exuvial matter (after Winberg 1971, 

 somewhat corrected for protein compounds) and 

 a C content of ca. 45% (according to the molecular 

 formula of chitin), then the energy losses should 

 be ca. 0.23 J in the Z-l, 0.29 in the Z-2, and 1.61 in 

 the megalopa. These estimates correspond to ca. 

 9, 7, and 34% of total body energy levels in late 

 premolt in these stages. Compared with average 

 daily energy fixation rates (see above), these 

 figures mean losses of ca. 1.3 to 1.4 d in the zoeal 

 stages, and ca. 8 d in the megalopa. 



Preliminary experiments were carried out to 



Table 5.— Composition [carbon (C), nitrogen (N), hydrogen 

 (H)] of larval exuviae of Hyas araneus and percentage of pre- 

 molt matter cast at ecdysis. n - number of analyses, AT = 

 number of exuviae analyzed. 



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