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These results are very important since larval settlement (and metamorphosis)
is known to be the most critical phase in the life history of any marine benthic species
given that it involves essential changes in morphology, physiology and habitat (Chia,
1989).
5.4- Reproductive adaptations of the different deep-sea asteroid species in
the North-East Atlantic Ocean.
The present study demonstrates that asteroids can inhabit a greater depth range
than most of the population actually exploit. The reasons for the contraction of the
depth range of a species are still unidentified. It is probable that post-selective forces
may exist, which are responsible for the distribution of the species over such
relatively small depth ranges (Howell et al., 2002). Factors specific of a particular
zone such as suitability of habitat, food availability, or interactions with other species,
which eliminates juveniles are likely to affect the distribution on this local scale rather
than potentially lethal factors, such as temperature or pressure.
The present study found differences in the reproductive traits of the species in
correspondence to the zones proposed by Howell et al. (2002) and taking into account
the effect of the environmental factors in selecting the species with successful lifehistory
patterns, as well as the phylogenetic constrains inherent of the species.
The upper slope zone ranging from the shelf break to ~700 m is characterized
by large seasonally reproducing predators that exhibit the life-history periodic pattern
established by Winemiller and Rose (1992), having large body size, high fecundity,
small egg size, single spawning frequency, and possibly low juvenile survivorship.
The life-history periodic pattern is distinctive of species inhabiting predictable and
seasonal environments (Winemiller and Rose, 1992; McCann and Shuter, 1997).
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