ANGER and DAWIRS: ELEMENTAL COMPOSITION OF HYAS ARANEUS 



However, due to high variation among the 1979 

 samples, these differences were not statistically 

 significant. 



In May 1979, eight Z-2 of H. araneus were 

 isolated from a plankton sample and analyzed 

 for comparison. The results (Table 4) compared 

 favorably with those of late laboratory-reared Z- 

 2 larvae (Table 2), although C and H values were 

 slightly higher in the field-caught larvae. 



It becomes obvious from Figure 3 (lower 

 graph) that growth in the megalopa was quite 

 different from that in the zoeal stages. Since 

 variation among analyses (see Table 2) was 

 rather high, calculation of fitted growth curves 

 was not considered useful and, therefore, only 

 the assumed pattern was displayed in the 

 diagram as an eye-fitted curve. A surprising de- 

 crease in all parameters was found during the 

 last third of the megalopa stage. As a result, 

 young crabs contained only little more organic 

 substances than young megalopae (Fig. 1). 



From the above results, approximate average 

 daily energy gains per individual (J/d per ind.) 

 can be calculated. In the 1979 Z-l larvae a value 

 of 0.08 was estimated. This compares favorably 

 with the data reported by Anger and Nair (1979). 

 They found 0.06 (their figures —0.4 and 0.6 on 

 page 51 are erroneous; they should read —0.04 

 and 0.06), based on C contents, and 0.07 to 0.11, 

 based on biochemical composition (excluding 

 and including chitin, respectively). Since the 

 1980 larvae grew better (see above), their daily 

 energy gain was higher: 0.16 J/d per ind. In the 

 second zoeal stage a value of 0.22 was found 

 (Fig. 1). In the megalopa it was similar (0.20) 

 until day 16, when it dropped to —0.34 until 



Table 4.— Ranges and arithmetic means 

 (J) for Hyas araneus zoea-2 from 

 Helgoland plankton in May 1979. Four 

 analyses comprising eight individuals. 

 For explanation of abbreviations see 

 Table 1. 



metamorphosis; on the average, a weak gain 

 (0.02 J/d per ind.) resulted. 



The weight-specific energy content (J/mg 

 DW) followed a cyclic pattern (Fig. 4). Due to salt 

 uptake, it decreased during molt, and then it in- 

 creased again during growth. From instar to 

 instar there was a conspicuous decreasing trend. 

 It was related to a decrease in the percentage of 

 organic substances, expressed as maximum sum 

 of the C, N, and H portions (upper part of Fig. 4). 



The ratio between single elements can be used 

 as an index for biochemical composition. 

 Changes in the C:N ratio mainly indicate shifts 

 in the relative amounts of lipids (plus carbo- 

 hydrates) and proteins (plus free amino acids) 

 (Fig. 5). There were no major differences found 

 during the molt cycles. In all larval stages there 

 was an initial increase, followed by a decline. 



12 



16 20 24 28 32 



Day after hatching 



36 



40 



44 



48 



FIGURE 4.— Hyas araneus. Changes in 

 weight-specific energy during larval 

 development; vertical lines: 95% con- 

 fidence intervals of the means. Upper 

 right: Maximum sum of carbon (C), 

 nitrogen (N), and hydrogen (H) in all 

 larval stages. 



425 



