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possibility. The opportunistic species are distinctive of highly disturbed and
unpredictable environments (Winemiller and Rose, 1992; McCann and Shuter, 1997).
The zone between 1100 and 3000 m coincides with the transitional zone
proposed by Howell et al. (2002) where boundaries at 2500, 2800 and 3300 m are
thought to demonstrate a region of transition between bathyal and abyssal fauna.
Evolutionarily, bathyal species are likely to have a mixed origin, with some species
from the shelf and some originating from abyssal depths (Rogers, 2000).
Six of the nine species found below 3000 m in this study belong to the
Porcellanasteridae, a family found entirely in the deep sea. It is likely that the
reproductive features at this zone are also related to historical factors affecting
evolutionary pathways. (Vinogradova et al., 1959). Rice et al. (1991) found that the
base of the continental slope in the NE Atlantic occurs at ~ 3300 m and Howell et al.
(2002) proposed that this may represent a barrier to abyssal species.
The abyssal zone is inhabited by asteroids with reproductive features of
equilibrium K strategists (Winemiller and Rose, 1992), which have low fecundity,
large egg size and expected high juvenile survivorship, although their large body size
makes them more comparable to the classical K strategists (MacArthur and Wilson,
1967; Pianka, 1970). K strategists are characteristic inhabitants of constant
environments (Winemiller and Rose, 1992; McCann and Shuter, 1997).
5.5- Final remarks
From the earliest days of deep-sea exploration, it was assumed that animals
living in the presumably invariable environments of the deep sea should show lifehistory
features and reproductive modes differing from those of their shallow water
congeners, but the most recent investigations show that with few exceptions, the
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