ELEMENTAL COMPOSITION (C,N,H) AND ENERGY IN GROWING AND 

 STARVING LARVAE OF HYAS ARANEUS (DECAPODA, MAJIDAE) 



Klaus Anger 1 and Ralph R. Dawirs 2 

 ABSTRACT 



Laboratory-reared larvae of the spider crab, Hyas araneus L., were studied with regard to their 

 fresh weight (FW), dry weight (DW), carbon (C), nitrogen (N), hydrogen (H), and energy content(J; 

 estimated from C). FW remains fairly constant in each larval stage, regardless of feeding or 

 starving conditions. This is due to regular changes in water content as opposed to those in organic 

 constitutents. FW therefore is not a good measure for living biomass. Growth in fed zoeal stages, if 

 expressed by gain in any parameter but FW, can be described by power functions of time. There is a 

 considerable gain (by a factor of 2 to 3) within each of these two instars. In the magalopa also a high 

 amount of C, N, H, and energy is accumulated, but most of this gain is lost again during the last third 

 of its stage duration. This finding suggests that there is no more food uptake during this last period 

 preceding metamorphosis to the crab. In all larval stages, weight-specific energy (J/mg DW) follows 

 rather a cyclic pattern with decreases before and after molts, and increases during intermolt 

 periods. It shows a decreasing trend during larval development. The loss in cast exoskeletons is 

 <10% of premolt organic matter in the zoeal stages, but >30% in the megalopa. During starvation, 

 biomass declines in an exponential pattern. Larvae of all stages die, when ca. 40 to 60% of their living 

 substance and energy is lost. The C :N ratio suggests that protein serves as the main source of energy; 

 in the final phase, presumbaly, lipids are also catabolized. Weight-specific energy and probably also 

 metabolism decrease in a hyperbola-shaped curve. 



Advanced rearing techniques developed in the 

 last three decades have greatly increased our 

 knowledge of autecology and physiology of 

 meroplanktonic marine larvae. However, there 

 is little quantitative information on growth, 

 energetic needs, and reserves. 



Within the literature on decapod larvae, there 

 are numerous data on size increments from one 

 developmental stage to the next (Rice 1968), but 

 few on biomass production. Since size is fairly 

 constant in each particular instar, this informa- 

 tion represents only a rough measure of actual 

 growth patterns. 



A number of authors have investigated bio- 

 chemical or energetic aspects of larval develop- 

 ment in decapod crustaceans: Reeve (1969), 

 Mootz and Epifanio (1974), Frank et al. (1975), 

 Sulkin et al. (1975), Logan and Epifanio (1978), 

 Morgan et al. (1978), Anger and Nair (1979), 

 Capuzzo and Lancaster (1979), Omori (1979), 

 Dawirs (1980), Stephenson and Knight (1980). 

 These studies, however, mainly concentrated on 



'Biologische Anstalt Helgoland, Meeresstation, D-2192 

 Helgoland, Federal Republic of Germany. 



2 Zoologisches Institut der Universitat Kiel, Olshausenstr. 

 40 - 60, D-2300 Kiel 1, Federal Republic of Germany. 



Manuscript accepted December 1981. 

 FISHERY BULLETIN: VOL 80, NO. 3, 1982. 



gross differences among larval stages rather 

 than on changes within single instars. Thus, bio- 

 mass was either considered practically constant 

 in each stage, or it was interpolated by means of 

 (mostly exponential) regression equations 

 describing growth from the first to the last larval 

 instar. The present paper attempts to analyze 

 actual growth patterns within stages of the 

 spider crab, Hyas araneus. 



Growth achieved in the laboratory under 

 optimal food conditions (as in this paper) 

 probably represents only one end of the scope in 

 which development is possible, rather than a 

 typical expression of it. The other end is char- 

 acterized by the poorest food level still allowing 

 minimal growth. Anger and Dawirs (1981) dis- 

 cussed the potential ecological role of starvation 

 in a variable environment. They showed that 

 larvae of Hyas araneus are well adapted to this 

 condition. 



In the present study diminution and growth 

 rates were estimated from frequent samples of 

 starved and fed larvae. They constitute a further 

 step toward a better understanding of larval 

 ecology and energetics in North Sea species as 

 required in a joint research project! Anger and 



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