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Larval dispersal from eight populations of the ophiuroid Ophiothrix fragilis
(Abildgaard) in the English Channel was examined by Lefebvre et al. (2003) using an
advection/diffusion model. Although larval dispersal and settlement of this species are
apparently hydrodynamic constrained in almost all populations larval retention
appeared to be sufficient to ensure local recruitment, in spite of short larval life span
and/or meteorological conditions.
Nowadays it is recognized that the deep sea is not a single, continuous habitat,
but rather a mixture of habitats in which many species have particular specialized
requirements depending on where they are situated (Tyler, 1995).
The dynamic, insular and often temporary habitats represented by
hydrothermal vents and cold seeps with a rich supply of self-produced
(autochthonous) food contrast markedly with, stable, nutrient-poor and extensive
abyssal plains, where all energy has its sources from the sea surface. In a similar way,
the continental slope and rise include many different habitats, each characterized by
specific topographic features, physical characteristics, and food interactions, and each
occupied by distinct groups of species adapted to those different conditions.
Therefore, reproductive modes and life-history traits of animals show a rich variety of
strategies for responding to the diversity of habitats in the deep sea (Young, 2003).
5.3- Larval physiological tolerances of shallow-water asteroids
Eggs of the shallow-water asteroids Asterias rubens Linnaeus and
Marthasterias glacialis (Linnaeus) were fertilized in vitro and incubated through the
early embryonic cleavages until the larval stage. Early embryos, blastulae, gastrulae,
and swimming bipinnaria were subjected to a temperature/pressure regime of 5, 10,
15 and 20 o C and 1, 50, 100, 150 and 200 atm.
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