416
Craig M. YOUNG
ontogenetically to the euphotic zone comes from the
work of Ashworth (1915) and Bouchet (1976a,b),
both of whom collected deep-sea larvae among the
shallow-water plankton. Bouchet and Fontes (1981) and
Killingley and Rex (1985) analysed oxygen isotopes
in protoconchs; these data indicated that the carbonate
in protoconchs was deposited at a warmer temperature
than in the teloconchs.
Genetic studies of hydrothermal vent animals generally have demonstrated a high level of genetic exchange
among remote sites, suggesting the strong possibility of
larval dispersal (reviewed by Jollivet, 1993; Mullineaux
and France, 1995; Vrijenhoek, 1997; Tyler and Young,
1999). Indeed, larvae from many phyla have been
collected in vent plumes (Mullineaux et al., 1995,
1996), larval development has been inferred from shell
apices of many vent molluscs (Gustafson and Lutz,
1994); and a handful of vent and seep species have
been reared in the laboratory from larvae (Young
et al., 1996b; Epifanio et al., 1999; Marsh et al.,
2001; Pradillon et al., 2001). The swimming behavior
of larvae of the vent crab Bythograea thermydron
suggests that it disperses quite passively for long
distances, then begins walking when it encounters the
warm water of a vent. Similarly, the embryos of an
alvinellid polychaete, Alvinella pompejana, undergo
arrested development at 2ºC, then resume cleavages
when encountering warmer temperatures (Pradillon
et al., 2001). Using data on lipid reserves, metabolism
and currents, dispersal distance has been estimated
for the siboglinid polychaete Riftia pachyptila (Marsh
et al., 2001). The lecithotrophic larvae of this species
are capable of drifting for about 38 days. At 9ºN on
the East Pacific Rise, this dispersal time is sometimes
enough to permit dispersal over the transform faults
that separate ridge segments.
Young et al. (1999) analysed the geographic ranges
of deep-sea echinoderms and ascidians with known
modes of larval dispersal. They found that the standard
relationship between geographic range and mode of
development (planktotrophs disperse farther and have
broader ranges than lecithotrophs: see Jablonski and
Lutz, 1983) breaks down in deep water. This is
probably because lecithotrophs can drift much longer
distances in the cold temperatures of the deep sea than
in warmer surface waters. Some of the species with
the broadest ranges were elasipod holothurians, which
produce lecithotrophic larvae, but also are capable of
pelagic dispersal in the juvenile and adult stages.
Etter and Caswell (1994) tested the prediction of
their dispersal/disturbance model by examining the
relative proportions at various depths of gastropod
species with planktotrophic and nonplanktotrophic
development (Rex and War´ en, 1982). In the western
Atlantic, the proportion of prosobranch gastropods
with planktotrophic development increases with depth
to 2000 m, where the number of planktotrophic and
nonplanktotrophic species is approximately the same
(Rex and War´ en, 1982). This pattern fits the predictions of the model well, suggesting that disturbance
frequency might interact with other factors influencing
the evolution of larval dispersal in the deep sea.
CONCLUSIONS
It is now recognized that the deep sea is not a single,
continuous habitat, but rather a mosaic of habitats
in which many species have particular specialized
requirements (Tyler, 1995). The insular, dynamic, often
ephemeral, vent and seep habitats with abundant
sources of autochthonous nutrition contrast markedly
with stable, nutrient-poor and extensive abyssal plains
where all energy is allochthonous in origin. Likewise,
the continental slopes and rises contain many different
habitats, each characterized by specific topographic
features, food levels, and physical characteristics, and
each occupied by distinct assemblages of species
adapted to those conditions. It is not surprising
therefore that reproductive modes and life-history traits
of animals, as revealed by more than a century of
study, show a rich assortment of tactics and strategies
for responding to the diversity of habitats in the deep
sea. With few exceptions, the reproductive strategies
and tactics found in shallow-water systems are also
represented in the deep sea, though there remain clear
shifts in the relative importance of different strategies
with depth. As in most other ecological systems,
generalizations become harder to make as one learns
more about the details.
REFERENCES
Adiyodi, R.G. and Subramoniam, T., 1983. Arthropoda–Crustacea.
In: K.G. Adiyodi and R.G. Adiyodi (Editors), Reproductive Biology
of Invertebrates, Vol. 1: Oogenesis, Oviposition and Oosorption.
Wiley, Chichester, pp. 443–495.
Agassiz, A., 1881. Echinoidea. Reports of the Scientific Research of
the Voyage of HMS Challenger, Zoology, 3(9): 1−321. 65 Plates.
Allen, J.A., 1979. The adaptations and radiation of deep-sea bivalves.
Sarsia, 64: 19−27.
Craig M. YOUNG
ontogenetically to the euphotic zone comes from the
work of Ashworth (1915) and Bouchet (1976a,b),
both of whom collected deep-sea larvae among the
shallow-water plankton. Bouchet and Fontes (1981) and
Killingley and Rex (1985) analysed oxygen isotopes
in protoconchs; these data indicated that the carbonate
in protoconchs was deposited at a warmer temperature
than in the teloconchs.
Genetic studies of hydrothermal vent animals generally have demonstrated a high level of genetic exchange
among remote sites, suggesting the strong possibility of
larval dispersal (reviewed by Jollivet, 1993; Mullineaux
and France, 1995; Vrijenhoek, 1997; Tyler and Young,
1999). Indeed, larvae from many phyla have been
collected in vent plumes (Mullineaux et al., 1995,
1996), larval development has been inferred from shell
apices of many vent molluscs (Gustafson and Lutz,
1994); and a handful of vent and seep species have
been reared in the laboratory from larvae (Young
et al., 1996b; Epifanio et al., 1999; Marsh et al.,
2001; Pradillon et al., 2001). The swimming behavior
of larvae of the vent crab Bythograea thermydron
suggests that it disperses quite passively for long
distances, then begins walking when it encounters the
warm water of a vent. Similarly, the embryos of an
alvinellid polychaete, Alvinella pompejana, undergo
arrested development at 2ºC, then resume cleavages
when encountering warmer temperatures (Pradillon
et al., 2001). Using data on lipid reserves, metabolism
and currents, dispersal distance has been estimated
for the siboglinid polychaete Riftia pachyptila (Marsh
et al., 2001). The lecithotrophic larvae of this species
are capable of drifting for about 38 days. At 9ºN on
the East Pacific Rise, this dispersal time is sometimes
enough to permit dispersal over the transform faults
that separate ridge segments.
Young et al. (1999) analysed the geographic ranges
of deep-sea echinoderms and ascidians with known
modes of larval dispersal. They found that the standard
relationship between geographic range and mode of
development (planktotrophs disperse farther and have
broader ranges than lecithotrophs: see Jablonski and
Lutz, 1983) breaks down in deep water. This is
probably because lecithotrophs can drift much longer
distances in the cold temperatures of the deep sea than
in warmer surface waters. Some of the species with
the broadest ranges were elasipod holothurians, which
produce lecithotrophic larvae, but also are capable of
pelagic dispersal in the juvenile and adult stages.
Etter and Caswell (1994) tested the prediction of
their dispersal/disturbance model by examining the
relative proportions at various depths of gastropod
species with planktotrophic and nonplanktotrophic
development (Rex and War´ en, 1982). In the western
Atlantic, the proportion of prosobranch gastropods
with planktotrophic development increases with depth
to 2000 m, where the number of planktotrophic and
nonplanktotrophic species is approximately the same
(Rex and War´ en, 1982). This pattern fits the predictions of the model well, suggesting that disturbance
frequency might interact with other factors influencing
the evolution of larval dispersal in the deep sea.
CONCLUSIONS
It is now recognized that the deep sea is not a single,
continuous habitat, but rather a mosaic of habitats
in which many species have particular specialized
requirements (Tyler, 1995). The insular, dynamic, often
ephemeral, vent and seep habitats with abundant
sources of autochthonous nutrition contrast markedly
with stable, nutrient-poor and extensive abyssal plains
where all energy is allochthonous in origin. Likewise,
the continental slopes and rises contain many different
habitats, each characterized by specific topographic
features, food levels, and physical characteristics, and
each occupied by distinct assemblages of species
adapted to those conditions. It is not surprising
therefore that reproductive modes and life-history traits
of animals, as revealed by more than a century of
study, show a rich assortment of tactics and strategies
for responding to the diversity of habitats in the deep
sea. With few exceptions, the reproductive strategies
and tactics found in shallow-water systems are also
represented in the deep sea, though there remain clear
shifts in the relative importance of different strategies
with depth. As in most other ecological systems,
generalizations become harder to make as one learns
more about the details.
REFERENCES
Adiyodi, R.G. and Subramoniam, T., 1983. Arthropoda–Crustacea.
In: K.G. Adiyodi and R.G. Adiyodi (Editors), Reproductive Biology
of Invertebrates, Vol. 1: Oogenesis, Oviposition and Oosorption.
Wiley, Chichester, pp. 443–495.
Agassiz, A., 1881. Echinoidea. Reports of the Scientific Research of
the Voyage of HMS Challenger, Zoology, 3(9): 1−321. 65 Plates.
Allen, J.A., 1979. The adaptations and radiation of deep-sea bivalves.
Sarsia, 64: 19−27.