Smithsonian at the Poles: Contributions to International Polar

this same inshore habitat (Fontaine, 1988). Species of
the antarctica species group are assumed to have evolved
after the colonization of the Southern Ocean by a common
ancestor (see the Evolution of the Pelagic Calanoid
Fauna within the Southern Ocean section). Each species
of Paraeuchaeta in the remaining four species groups represented
in the Southern Ocean has its closest relative in
other oceans, rather than the Southern Ocean, suggesting
that the remaining species of Paraeuchaeta may have colonized
the Antarctic region independently.
The family Heterorhabdidae is represented in the
Southern Ocean by three genera, Heterorhabdus, Heterostylites,
and Paraheterorhabdus. There are fi ve species in
the fi rst genus; a single species in each of the last two genera
is found in the Southern Ocean (Park, 2000). Four of the
fi ve species of Heterorhabdus belong to the same species
group, the abyssalis species group, with 17 species. Two of
the four species of this group, H. spinosus and H. paraspinosus,
are morphologically quite similar, suggesting a recent
speciation event within the Southern Ocean. The remaining
two Heterorhabdus species of the abyssalis species group,
H. austrinus and H. pustulifer, are morphologically dissimilar;
they may have colonized the Southern Ocean independently
from one another and from the pair H. spinosus
and H. paraspinosus. The fi fth species, H. lobatus, belongs
to the papilliger species group along with fi ve other species
found in other oceans; along with Paraheterorhabdus farrani
and Heterostylites nigrotinctus, H. lobatus represents
an independent colonization.
INSHORE CALANOIDS ALONG
CONTINENTAL AND INSULAR COASTS
OF THE SOUTHERN OCEAN
Eight species of pelagic calanoids have been found
exclusively in waters close to a land mass of the Southern
Ocean (Table 1): three species of Drepanopus (D. bispinosus,
D. forcipatus, and D. pectinatus), three species
of Paralabidocera (P. antarctica, P. grandispina, and
P. separabilis), and two species of Stephos (S. longipes
and S. antarcticus). The three species of Drepanopus
have been collected several times, and all three occasionally
have been collected in very large numbers, so
their distribution is well known. Drepanopus bispinosus
has been reported, often as abundant, from inshore waters
adjacent to the Vestfold Hills region of Antarctica
(Bayly, 1982), and its population structure has been established
(Bayly, 1986). Drepanopus pectinatus occurs
close to shores of Crozet Island, Kerguelen Island, and
PELAGIC CALANOID COPEPODS OF THE SOUTHERN OCEAN 149
TABLE 1. Inshore pelagic calanoid copepods of the southern
ocean. Ant, waters south of the Antarctic Convergence; S-Ant,
waters between the Antarctic Convergence and the Subantarctic
Convergence; CC, very common (over 100 specimens found); C,
common (between 99 and 50 specimens found); R, rare (between
49 and 10 specimens found).
Species name Distribution Abundance
Drepanopus bispinosus Ant CC
Drepanopus forcipatus S-Ant CC
Drepanopus pectinatus S-Ant CC
Paralabidocera antarctica Ant C
Paralabidocera grandispina Ant R
Paralabidocera separabilis Ant R
Stephos longipes Ant C
Stephos antarcticus Ant R
Heard Island in the Indian Ocean sector of the Southern
Ocean (Hulsemann, 1985a); some aspects of its biology
also have been elucidated (Razouls and Razouls, 1990).
Drepanopus forcipatus is restricted to Atlantic and Pacifi
c coastal and shelf areas along southern South America,
including the Falkland Islands, and around South
Georgia Island (Hulsemann, 1985a); its copepodid stages
have been described (Hulsemann, 1991).
The distributions of the remaining fi ve inshore species
are not as well known, and only Paralabidocera antarctica
and Stephos longipes have been reported from more than
one locality. Paralabidocera antarctica is now known to
occur in small numbers in waters close to the shoreline
at several locations, including the South Shetland Islands,
the extreme south of the Ross Sea, two localities in the Atlantic
Ocean sector of Antarctica, and one locality in the
Indian Ocean sector of Antarctica (Vervoort, 1957). The
species is believed to inhabit the surface water layers and
is occasionally captured under the ice (Vervoort, 1951);
development of its marine and lacustrine populations has
been described (Swadling et al., 2004). Paralabidocera
grandispina Waghorn, 1979 and P. separabilis Brodsky
and Zvereva, 1976 are known only from their type localities,
beneath the ice along the Pacifi c Ocean sector of
Antarctica and near the shore of Antarctica in the Indian
Ocean sector, respectively.
Of the two species of Stephos, S. longipes has been
found close to or under the ice shelf in the Pacifi c and
Indian ocean sectors of Antarctica including the Ross Sea,
where it can be very abundant (Giesbrecht, 1902; Farran,
1929; Tanaka, 1960). Its associations with the ice and the
open water have been described (Kurbjeweit et al., 1993;