Development and growth in larval and juvenile Hyas coarctatus (Decapoda, Majidae) reared in the laboratory

Larvae of the spider crab Hyas coarctatus Leach were reared in the laboratory.Duration of development in the larval and early juvenile stages was studied in relation to temperature, and compared to previous findings in a closely related species, H. araneus.Mortality in H. coarctafus was higher at extreme (18 and 6°C) than at intermediate (9 to 15°C) temperatures.The laboratory-derived results were used to estimate the duration of development from hatching to the third crab stage in the field.Settling and metamorphosis was predicted to occur mainly during June.Biomass, measured as early postmoult dry weight, carbon, nitrogen, and hydrogen, increased exponentially during larval development from hatching to metamorphosis.Juvenile growth (increase in carapace length) was also exponent~al, and was maximum at g°C, and minimum at 18 and 6°C.Growth rates observed in the laboratory would suggest that: (1) in the field H. coarctatus probably reaches sexual maturity and its final body size during the second year of postlarval life; (2) first offspring can hatch 2 yr after hatching of the mother generation; (3) freshly hatched H. coarctatus larvae are smaller and contain much less biomass than those of H. araneus, but because of higher growth rates they catch up w ~t h H. araneus, and juvenile crabs of these species are of equal size in the same instar.However, growth and moulting cease earlier (after fewer moults) in H. coarctatus, so that its final size is much smaller than H. araneus.