394
Craig M. YOUNG
sea crustaceans is that by Van Dover and Williams
(1991) of 52 species of squat lobsters in the superfamily Galatheoidea, which related fecundity and egg size
to depth of occurrence. They found a positive correlation between fecundity and body size, but no indication
of reduced fecundity in deep-sea species that could
not be explained by phylogenetic constraints. Hines
(1988) reported that fecundity of two species of deepsea geryonid crabs is significantly lower than those of
shallow-water crabs with similar body sizes, but that
reproductive output is in fact higher; the low fecundity
values result from partitioning the reproductive effort
into larger eggs. The reproductive effort of brachyuran
crabs seems always to be limited by the amount of
space available in the cephalothorax for yolk accumulation (Hines, 1982), and this rule applies equally well to
the deep-sea forms as to those in shallow water (Hines,
1988). Ramirez Llodra et al. (2000) noted the same
relationship between brood size and body size in deepsea caridean shrimps whether they lived in mid-water
or at Atlantic hydrothermal vents. It should be noted
that closely related crustaceans having very different
fecundities may be successful in the same deep-sea
habitats. Perhaps the most striking example of this
occurs in two congeneric vent-associated galatheids,
Munidopsis lentigo and M. subsquamosa, both of which
live at Pacific vents; they have fecundities of 13 eggs
and 294 eggs, respectively (Van Dover et al., 1985).
Ramirez Llodra et al. (2000) examined fecundity
of three caridean species from hydrothermal vents.
One of these, Mirocaris fortunata, had highly variable
fecundity, the number of eggs carried by a female
ranging from 25 to 503. Based on a single berried
female from each species, Chorocaris chacei and
Rimicaris exoculata had much higher fecundities
than M. fortunata, carrying 2510 and 988 eggs,
respectively.
Embryogenesis and larval development
Peracarids have direct development, brooding their
young to a stage that resembles a miniature adult. Apart
from the study by Tso and Mok (1991) on development
of the giant isopod Bathynomus doederleini, there
have been few specific studies of embryology in
deep-sea peracarids, though Bishop and Shalla (1994)
carefully monitored changes in embryo number and
size in the cumacean Leucon profundus. They found
that embryogenesis was synchronous for the first
eight months of development (their stages I–III), but
a pattern of asynchronous development began with
the last two embryonic stages. Specifically, females
with advanced embryos always contained a single
stage V individual which was about to hatch, while the
remaining embryos in the brood were still at stage IV.
This observation suggests that large juveniles (manca
stage) grow to full size one at a time and are released
singly, the individuals in the brood hatching over a
period of several months. A similar pattern of hatching
has been found in the aseasonal congener Leucon jonesi
(Bishop, 1994).
One of the first deep-sea larvae to be described in
the literature was that of the deep-sea eryonid crab
Willemoesia suhmi, a drawing of which appeared in the
Challenger reports. Embryological development has
since been described for several deep-sea decapods
(e.g., Brattegard and Sankarankutty, 1967; Herring,
1974; Ingle, 1979; Sulkin and Van Heukelem, 1980;
Williamson, 1982). In all cases, the patterns of development and the early larvae resembled closely those
of shallow-water relatives. Caridean shrimps, including
the very abundant vent shrimps Chorocaris chacei,
Mirocaris fortunata and Rimicaris exoculata, have
been studied extensively in recent years. Vereschaka
(personal communication) has found embryos in the
water column which he ascribes to Rimicaris exoculata,
but there is some controversy about their identity. If
this observation is correct, R. exoculata would be
the only caridean that does not brood its embryos on
the pleopods until hatching. However, this observation
would help explain why very few berried vent shrimps
have been collected. Larvae of Atlantic vent shrimps
have been collected in midwater plankton samples
near the mid-Atlantic Ridge, and postlarvae have been
collected as far as 1000 km away, suggesting that
dispersal potential is substantial (Herring and Dixon,
1998).
Fage (1956) reported that the eggs of pycnogonids
(sea spiders) collected from a depth of more than
6000 m in the Banda Sea are brooded on the ovigerous
legs of the males, in exactly the same manner as those
of their shallow-water counterparts.
Mollusca
Deep-sea sediments contain a tremendous variety
of gastropods (Clarke, 1962). Although some larger
buccinids and pleurotomariids are encountered at slope
depths (Harasewych, 2002), the deep-sea gastropods
fauna is dominated by diminutive caenogastropod
predators such as turrids. Ectoparasitic forms living as
Craig M. YOUNG
sea crustaceans is that by Van Dover and Williams
(1991) of 52 species of squat lobsters in the superfamily Galatheoidea, which related fecundity and egg size
to depth of occurrence. They found a positive correlation between fecundity and body size, but no indication
of reduced fecundity in deep-sea species that could
not be explained by phylogenetic constraints. Hines
(1988) reported that fecundity of two species of deepsea geryonid crabs is significantly lower than those of
shallow-water crabs with similar body sizes, but that
reproductive output is in fact higher; the low fecundity
values result from partitioning the reproductive effort
into larger eggs. The reproductive effort of brachyuran
crabs seems always to be limited by the amount of
space available in the cephalothorax for yolk accumulation (Hines, 1982), and this rule applies equally well to
the deep-sea forms as to those in shallow water (Hines,
1988). Ramirez Llodra et al. (2000) noted the same
relationship between brood size and body size in deepsea caridean shrimps whether they lived in mid-water
or at Atlantic hydrothermal vents. It should be noted
that closely related crustaceans having very different
fecundities may be successful in the same deep-sea
habitats. Perhaps the most striking example of this
occurs in two congeneric vent-associated galatheids,
Munidopsis lentigo and M. subsquamosa, both of which
live at Pacific vents; they have fecundities of 13 eggs
and 294 eggs, respectively (Van Dover et al., 1985).
Ramirez Llodra et al. (2000) examined fecundity
of three caridean species from hydrothermal vents.
One of these, Mirocaris fortunata, had highly variable
fecundity, the number of eggs carried by a female
ranging from 25 to 503. Based on a single berried
female from each species, Chorocaris chacei and
Rimicaris exoculata had much higher fecundities
than M. fortunata, carrying 2510 and 988 eggs,
respectively.
Embryogenesis and larval development
Peracarids have direct development, brooding their
young to a stage that resembles a miniature adult. Apart
from the study by Tso and Mok (1991) on development
of the giant isopod Bathynomus doederleini, there
have been few specific studies of embryology in
deep-sea peracarids, though Bishop and Shalla (1994)
carefully monitored changes in embryo number and
size in the cumacean Leucon profundus. They found
that embryogenesis was synchronous for the first
eight months of development (their stages I–III), but
a pattern of asynchronous development began with
the last two embryonic stages. Specifically, females
with advanced embryos always contained a single
stage V individual which was about to hatch, while the
remaining embryos in the brood were still at stage IV.
This observation suggests that large juveniles (manca
stage) grow to full size one at a time and are released
singly, the individuals in the brood hatching over a
period of several months. A similar pattern of hatching
has been found in the aseasonal congener Leucon jonesi
(Bishop, 1994).
One of the first deep-sea larvae to be described in
the literature was that of the deep-sea eryonid crab
Willemoesia suhmi, a drawing of which appeared in the
Challenger reports. Embryological development has
since been described for several deep-sea decapods
(e.g., Brattegard and Sankarankutty, 1967; Herring,
1974; Ingle, 1979; Sulkin and Van Heukelem, 1980;
Williamson, 1982). In all cases, the patterns of development and the early larvae resembled closely those
of shallow-water relatives. Caridean shrimps, including
the very abundant vent shrimps Chorocaris chacei,
Mirocaris fortunata and Rimicaris exoculata, have
been studied extensively in recent years. Vereschaka
(personal communication) has found embryos in the
water column which he ascribes to Rimicaris exoculata,
but there is some controversy about their identity. If
this observation is correct, R. exoculata would be
the only caridean that does not brood its embryos on
the pleopods until hatching. However, this observation
would help explain why very few berried vent shrimps
have been collected. Larvae of Atlantic vent shrimps
have been collected in midwater plankton samples
near the mid-Atlantic Ridge, and postlarvae have been
collected as far as 1000 km away, suggesting that
dispersal potential is substantial (Herring and Dixon,
1998).
Fage (1956) reported that the eggs of pycnogonids
(sea spiders) collected from a depth of more than
6000 m in the Banda Sea are brooded on the ovigerous
legs of the males, in exactly the same manner as those
of their shallow-water counterparts.
Mollusca
Deep-sea sediments contain a tremendous variety
of gastropods (Clarke, 1962). Although some larger
buccinids and pleurotomariids are encountered at slope
depths (Harasewych, 2002), the deep-sea gastropods
fauna is dominated by diminutive caenogastropod
predators such as turrids. Ectoparasitic forms living as