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lecithotrophic development. The prediction that species with planktotrophic larvae
should have more extensive geographic ranges than species with lecithotrophic larvae
did not hold for echinoderms. Asteroid and echinoid species with planktotrophic
development had more constrained distributions compared with lecithotrophic
species. Some of the most widespread species in the deep sea reproduce without the
hypothetical advantage of planktotrophy, although some studies have identified a few
species, which seem to have developed a way to use the advantage of both modes of
development, for example the larvae of the echinoid Aspidodiadema jacobyi develop
from a small egg (90 µm) like typical planktotrophs, but unlike other species,
development of a mouth is delayed for the first 21 days, as the blastocoel becomes
filled with yolky cells from the vegetal plate. These yolky cells permit dispersal and
perhaps vertical migration for up to two months before planktonic food is required
(Young et al., 1989).
There is some further evidence that lecithotrophic larvae have sufficient
energy and nutrients store in order to remain in the water column for long periods of
time. Birkeland et al. (1971) noted that larvae of the temperate starfish Mediaster
aequalis Stimpson survived in culture for more than a year before settlement. Young
& Cameron (1989) carried out experiments about the developmental rate as a function
of depth with the bathyal echinoid species Linopneustes longispinus, showing that the
development of embryos maintained at 5 o C was delayed at the gastrula stage for over
four months and the embryos never became plutei at this temperature. Nevertheless,
gastrulae relocated to temperatures at 10 and 15 o C rapidly developed into plutei.
These results highlighted that at low temperatures the potential for dispersal without
feeding is even greater because of low metabolic demand. Shilling & Manahan (1994)
demonstrated experimentally that the lecithotrophic larvae of some Antarctic
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