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al., 1983; MacDonald and Thopmson, 1985a, b; Barber et al., 1988; Paulet and
Boucher, 1991; Honkoop and van der Meer, 1997), gastropods (Spight and Emlen,
1976; Chester, 1996; Cheung and Lam, 1999;), opisthobranchs (Krug, 1998),
echinoids (Vadas, 1977; Meidel and Scheibling, 1998; Beddingfield and McClintok,
1998; Bertram and Strathmann, 1998; Brewin et al., 2000), Antarctic and temperate
echinoderms (Shilling and Manahan, 1994), holothurians (Wigham et al., 2003) and
asteroids ( George et al., 1990; George, 1994; Bosch and Slattery, 1999; Ramirez-
Llodra et al., 2002).
4.4.2. Depth allocation of the species and possible causes.
Howell et al. (2002) found distinct changes in the vertical distribution of the
asteroid fauna in the Porcupine Seabight and Porcupine Abyssal Plain. The present
study also 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 life-history strategies, as
well as the phylogenetic constrains inherent of the species.
Predator species are more abundant at shallower depths and become scarce
with increasing depth (Carey, 1972; Howell et al., 2002). Thus the upper slope zone
ranging from the shelf break to ~700 m is characterized by large seasonally
reproducing predators. They produce small eggs correlated with a large population
size, which increases the chances of successful fertilization. It is not necessary to
invest energy in producing large eggs because the small eggs produce planktotrophic
larvae which feed directly on primary production from surface waters. This upper
continental slope zone is characterized by asteroid species which exhibit the lifehistory
periodic pattern established by Winemiller and Rose (1992), of large body
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