ABSTRACT: Swimming behavior was observed and substrate preference determined for glaucothoe stage postlarvae of the red king crab Paralithodes camtschaticus in the laboratory. One hundred 1 d old glaucothoe were placed into each of 3 replicate 10 l aquaria, each containing a choice of 3 substrates: sand, gravel, or synthetic fiber mesh. Glaucothoe began settling on the first day, and <10% remained swimming after Day 6. Glaucothoe showed a significant preference for the structurally complex mesh substrate. Occupancy of mesh increased from 49% on Day 2 to 75% by metamorphosis to the first crab (C1) instar, with a mean of 62 ± 11%. Glaucothoe rejected sand, and only 1% were observed on it. Settlement was also tested in aquaria with only sand, gravel or mesh substrates. Glaucothoe in gravel- or mesh-only aquaria settled rapidly, whereas 40% of glaucothoe in the sand-only aquarium continued swimming until metamorphosis to C1 instar. In addition, mean time-to-metamorphosis in the sand-only aquarium (17.6 d) was significantly greater than in other experimental aquaria (16.8 d). Glaucothoe in the sand-only aquarium exhibited marked diurnal swimming behavior; 66% were swimming at 14:00 h (vs a maximum of 12% in other aquaria), but only 5% (vs 1%) were swimming at 02:00 h. Daytime swimming probably allows glaucothoe to avoid nocturnal predators while searching for preferred substrates, i.e. those which are structurally complex, can be easily grasped, and provide a high degree of interstitial space.

KEY WORDS: Settling · Metamorphosis · Substrate · Decapoda · Postlarvae · Glaucothoe

Published in MEPS Vol. 167 (1998) on June 18
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1998