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(Hymenaster membranaceus Thomson). The two species of the family Myxasteridae
analyzed in this study were grouped in the cluster B.
After comparing the depth distribution of the species with the results obtained
by the cluster analysis, a possible pattern of zonation and reproductive features was
found considering the adult size, egg size, fecundity and Gonad Index as follows:
a) A first zone is found, which coincides with the zonation established by Howell
et al. (2002). In this first zone situated in the upper slope from 150-700 m depth, large
species with shallow-water distribution, small egg size, high fecundity and
planktotrophic development are found.
b) Only two species with large adult size, low G.I., large egg size and low
fecundity indicating lecithotrophic development are found from around 800 m depth.
c) From 700 to 1100 m depth only species having small adult size, large egg size
with low fecundity and low G.I. are found, the totality of this species are included in
the cluster B recognized by the cluster analysis, this zone coincides with the mid
bathyal zone proposed by Howell et al. (2002).
d) A zone of mixed reproductive features on the species was found from ~1100
to ~3000 m. In this zone there are species belonging to the three clusters found in the
cluster analysis. Therefore, there are species having large adult size, low G.I., large
egg size and low fecundity, there are also species with small adult size, low G.I, large
egg size and low fecundity. Finally in this zone are also found species which have
large adult size, large egg size, low fecundity, and low Gonad Index. This pattern
appears to support the existence of a zone of transition from 1700-3300 m proposed
by Howell et al. (2002) consisting in part of bathyal species whose ranges extend
down into this zone and in part from abyssal species whose ranges extend up into this
zone, with few species confined to the transition zone.
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