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Larvae of the spider crab Hyas araneus were reared in the laboratory at constant conditions (12 ~ 32 %oS), and their feeding rate (F), oxygen consumption (R), nitrogen excretion (U), and growth were measured in regular intervals of time during development from hatching to metamorphosis. Growth was measured as dry weight (W), carbon (C), nitrogen (AT), hydrogen (H) protein, and lipid. All these physiological and biochemical traits revealed significant changes both from instar to instar and during individual larval moult cycles. Average F was low in the zoea I, reached a maximum in the zoea II, and decreased again in the megalopa. In the zoeai instars, it showed a bell-shaped pattern, with a maximum in the middle (zoea I) or during the first half of the moult cycle (zoea II). Maximum F in the megalopa was observed still earlier, during postmoult.Respiration (R) increased in the zoeai instars as a linear function of time, whereas it showed a sinusoidal pattern in the megalopa. These findings on variation in F and R during larval development confirm results obtained in previous studies on H. araneus and other decapod species. Excretion (U) was measured for the first time with a high temporal resolution in crab larvae. It showed in all three larval instars a bell-shaped variation pattern, with a maximum near the middle of the moult cycle, and significantly increasing average values from" instar to instar. The atomic O/IV ratio followed an inverse pattern, suggesting a maximum utilization of protein as a metabolic substrate during intermoult Growth data from the present study and from a number of previous studies were compiled, showing consistency of growth patterns, but a considerable degree of variability between larvae from different hatches reared under identical conditions. The data show the following consistent tendencies: during the first part of each larval moult cycle (in postmoult, partly in intermoult), lipids are accumulated at a higher rate than protein, whereas an inverse growth pattern is typical of the later (premoult) stages. These two different growth phases are interpreted as periods dominated by reserve accumulation in the hepatopancreas, and epidermal growth and reconstruction (morphogenesis), respectively. Differences between individual larval instars in average biochemical composition and growth patterns may be related to different strategies: the zoeal instars and the early megalopa are pelagic feeding stages, accumulating energy reserves (principally lipids) necessary for the completion of larval development, whereas the later (premoult) megalopa is a semibenthic settling stage that converts a significant part of this energy to epidermal protein. The megalopa shifts in behaviour and energy partitioning from intense feeding activity and body growth to habitat selection and morphogenesis, preparing itself for metamorphosis, i.e. it shows an increasing degree of ]ecithotrophy. Data from numerous parallel elemental and biochemical analyses are compiled to show quantitative relationships ...

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Larvae of Elminius modestus (Darwin) at a wide range of temperature (6 ° to 24 °C) and salinity (20 to 50 %0 S). Mortality was highest at 10 %0 S; only at 12 ° and 18 °C did a small percentage develop to the cypris, The larvae from New Zealand were reared at a temperature range of 12°-24 °C at 20, 30 and 40 %0 S; mortality increased in all populations at all salinities with decreasing temperature and was extremely high at 12 °C and 40 %0 S. The temperature influence on larval duration could be described in all cases by a power function. No significant differences in temperature influences on developmental times between the tested salinities were found, except for the Portobello population at 20 %o S. Significant differences were found in the temperature influence on larval development between the populations from Helgoland and the North Island of New Zealand (Leigh, Doubtless Bay). No differences were found between the Helgoland and Portobello population. The pooled data for the temperature influence on the larval development of the three tested New Zealand populations at 20, 30 and 40%o S and the pooled Helgoland data at 20, 30 and 40 %~ S show highly significant differences.Larval size (stage VI) was influenced by experimental conditions. The larvae grew bigger at low temperatures and attained their maximum size at 30%0 S (Helgoland). There was a strong reduction in larval size at temperatures from 18 ° to 24 °C. The .larvae of the New Zealand populations were smaller than those from Helgoland. The greatest difference in size existed between the larvae from Portobello and Helgoland.