100 Chapter 4 Euphausiids
come indistinguishable from those of T. macrura
and T. vicina. The relatively larger gill size has
proven to be a good secondary character for T.
gregaria. Differences between the thelycums of
T. gregaria and T. parva regard only the coxal
plates. In T. gregaria, they are more extended
posterolaterally, delimiting 2 wide pockets,
where the spermatophores are located (Costanzo and Guglielmo 1977).
Distribution
T. gregaria inhabits the North (Bigelow 1926;
Moore 1952) and South (Zimmer 1914; Ramirez
1971; Antezana and Brinton 1981) Atlantic, the
Indian Ocean (Illig 1930) and Mediterranean Sea
(Ruud 1936). In both the Pacific and Atlantic
Oceans, T. gregaria is an antitropical or bipolar
species occupying the Transition Zone between
Sub polar and Central Water masses in the midocean and between subpolar and equatorial waters in the California and Humboldt Current
(Brinton 1962b ). Brinton explained the present
disjunct distribution of T. gregaria resulting
from the successive cooling and warming (2.5 oc
at 200 m) of the ocean during the ice ages (Brinton 1962b ). Off the Chilean coast, T. gregaria is
found in a wide latitudinal range between 15°
and 56°S. In the Humbold Current, it occupies an
intermediate oceanic belt 60-200 miles offshore,
and in sub-Antarctic waters of the Cape Horn
Current, it is concentrated in coasta! regions
(Antezana 1978, 1981). In Chilean fjords, T. gregaria is the second most abundant euphausiid,
preceded by E. vallentini. Both species have been
found in mutually exclusive swarms (Antezana
1976). In the present study, only a small number
of specimens were sampled at St. 26. The species
seems tobe confined to areas at the Atlantic entrance to the Straits, where it was sampled from
20-30 m.
come indistinguishable from those of T. macrura
and T. vicina. The relatively larger gill size has
proven to be a good secondary character for T.
gregaria. Differences between the thelycums of
T. gregaria and T. parva regard only the coxal
plates. In T. gregaria, they are more extended
posterolaterally, delimiting 2 wide pockets,
where the spermatophores are located (Costanzo and Guglielmo 1977).
Distribution
T. gregaria inhabits the North (Bigelow 1926;
Moore 1952) and South (Zimmer 1914; Ramirez
1971; Antezana and Brinton 1981) Atlantic, the
Indian Ocean (Illig 1930) and Mediterranean Sea
(Ruud 1936). In both the Pacific and Atlantic
Oceans, T. gregaria is an antitropical or bipolar
species occupying the Transition Zone between
Sub polar and Central Water masses in the midocean and between subpolar and equatorial waters in the California and Humboldt Current
(Brinton 1962b ). Brinton explained the present
disjunct distribution of T. gregaria resulting
from the successive cooling and warming (2.5 oc
at 200 m) of the ocean during the ice ages (Brinton 1962b ). Off the Chilean coast, T. gregaria is
found in a wide latitudinal range between 15°
and 56°S. In the Humbold Current, it occupies an
intermediate oceanic belt 60-200 miles offshore,
and in sub-Antarctic waters of the Cape Horn
Current, it is concentrated in coasta! regions
(Antezana 1978, 1981). In Chilean fjords, T. gregaria is the second most abundant euphausiid,
preceded by E. vallentini. Both species have been
found in mutually exclusive swarms (Antezana
1976). In the present study, only a small number
of specimens were sampled at St. 26. The species
seems tobe confined to areas at the Atlantic entrance to the Straits, where it was sampled from
20-30 m.