100
Systematic Account
3.14 Calanus simillimus
Giesbrecht 1902
Calanus simillimus Giesbrecht, 1902: p. 16,
pI. 1 fig. 9 - van Breemen, 1908: p. 10, fig.
5 - Wolfenden, 1908: p. 10, pI. 1 figs. 5,
6 - Mackintosh, 1934: p. 85, figs. 3c, c 1 -
Vervoort, 1951: p. 11, figs. 3-14 - Tanaka,
1960a: p. 12, pI. 2 figs. 3-10.
Calanus propinquus Giebrecht, 1892: p. 91,
pI. 7 figs. 31, 34, pI. 8 figs. 14, 22, 24, 32.
Body length -
females: 2.93-3.97 mm (31 specimens)
males: 2.89-3.20mm (10 specimens)
Female. Body slender, with a distinctly
obtuse head in dorsal view. Proportional
lengths of cephalothorax and abdomen 75: 25.
Last thoracic somite with triangular-shaped
ma'rgins which extend half-way across genital
somite; postero-Iateral corners pointed,
with points slightly produced. Proportional
lengths of abdominal so mites and furca
36: 17: 14: 13:20 = 100. Genital somite
longer than wide. Each caudal ramus carries
5 thin setae and a curved short internal seta
bearing fine hairs on inner margin. P5
symmetrical. Internal margins of B 1 carry
about 18 triangular teeth of equal size and
small cluster of 3-4 teeth isolated from the
others.
Male. Same body shape as female with
similar proportional lengths between
cephalothorax and abdomen 74: 26. Proportionallengths of abdominal somites and furca
12:31: 17: 13: 13: 14 = 100. Caudal rami
diverging and carrying 5 thin setae and
curved inner seta. P5 asymmetrical. B1 with
asymmetrical left and right sides, this latter
shorter than the left. Both furnished with
triangular teeth on inner margin (20-22 on
left B1). Left exopod twice the length of
exopod of right P5. Endopod of left leg
reaching base of Re2. Last joint of left
exopod with 2 small lateral spines and 1 very
long apical spine about 1.5 times length of
joint. Inner margin of last joint ornated with
short bristles and small cluster of longer
hairs.
Remarks
Our specimens are similar to those described
by Vervoort (1951) except for the toothing of
the margins of the P5 B 1 in both females and
males. The teeth are more numerous in our
specimens. Also, the last joint of the left P5
of the male differs by the presence of an
ornamentation along the inner margin that is
not reported in Vervoort's fi.gure.
Distribution
C. simillimus ranges widely over northern
Antarctic and sub-Antarctic oceanic areas.
According to Mackintosh (1934) and
Vervoort (1951), this species is a normal
inhabitant of sub-Antarctic waters. It may
also occur near the Convergence and is at
times carried south of the polar front in certain
areas (Ramirez and Dinofrio 1976).
Specimens have been reportc;:d for Chilean
fjords by many Authors (Arcos 1976; Marin
and Antezana 1985; Hirakawa and Zama
1985; Hirakawa 1989). Mazzocchi and Ianora
(1991) reported it as the most common
Calanus species in previous collections from
the Straits of Magellan, where it was present,
mainly as copepodite stages, only in the
Pacific sector. Hardy and Gunther (1935)
reported that the vertical distribution of C.
simillimus ranges up to 1000 m throughout
the area between South Georgia and the
Falkland Islands. They also noted that this
species exhibits marked and rapid diurnal
vertical migrations. In the present study, C.
simillimus was distributed throughout the
Straits of Magellan. Maximum abundances
were recorded in the Central area, where it
was found at all sampled depths.
Systematic Account
3.14 Calanus simillimus
Giesbrecht 1902
Calanus simillimus Giesbrecht, 1902: p. 16,
pI. 1 fig. 9 - van Breemen, 1908: p. 10, fig.
5 - Wolfenden, 1908: p. 10, pI. 1 figs. 5,
6 - Mackintosh, 1934: p. 85, figs. 3c, c 1 -
Vervoort, 1951: p. 11, figs. 3-14 - Tanaka,
1960a: p. 12, pI. 2 figs. 3-10.
Calanus propinquus Giebrecht, 1892: p. 91,
pI. 7 figs. 31, 34, pI. 8 figs. 14, 22, 24, 32.
Body length -
females: 2.93-3.97 mm (31 specimens)
males: 2.89-3.20mm (10 specimens)
Female. Body slender, with a distinctly
obtuse head in dorsal view. Proportional
lengths of cephalothorax and abdomen 75: 25.
Last thoracic somite with triangular-shaped
ma'rgins which extend half-way across genital
somite; postero-Iateral corners pointed,
with points slightly produced. Proportional
lengths of abdominal so mites and furca
36: 17: 14: 13:20 = 100. Genital somite
longer than wide. Each caudal ramus carries
5 thin setae and a curved short internal seta
bearing fine hairs on inner margin. P5
symmetrical. Internal margins of B 1 carry
about 18 triangular teeth of equal size and
small cluster of 3-4 teeth isolated from the
others.
Male. Same body shape as female with
similar proportional lengths between
cephalothorax and abdomen 74: 26. Proportionallengths of abdominal somites and furca
12:31: 17: 13: 13: 14 = 100. Caudal rami
diverging and carrying 5 thin setae and
curved inner seta. P5 asymmetrical. B1 with
asymmetrical left and right sides, this latter
shorter than the left. Both furnished with
triangular teeth on inner margin (20-22 on
left B1). Left exopod twice the length of
exopod of right P5. Endopod of left leg
reaching base of Re2. Last joint of left
exopod with 2 small lateral spines and 1 very
long apical spine about 1.5 times length of
joint. Inner margin of last joint ornated with
short bristles and small cluster of longer
hairs.
Remarks
Our specimens are similar to those described
by Vervoort (1951) except for the toothing of
the margins of the P5 B 1 in both females and
males. The teeth are more numerous in our
specimens. Also, the last joint of the left P5
of the male differs by the presence of an
ornamentation along the inner margin that is
not reported in Vervoort's fi.gure.
Distribution
C. simillimus ranges widely over northern
Antarctic and sub-Antarctic oceanic areas.
According to Mackintosh (1934) and
Vervoort (1951), this species is a normal
inhabitant of sub-Antarctic waters. It may
also occur near the Convergence and is at
times carried south of the polar front in certain
areas (Ramirez and Dinofrio 1976).
Specimens have been reportc;:d for Chilean
fjords by many Authors (Arcos 1976; Marin
and Antezana 1985; Hirakawa and Zama
1985; Hirakawa 1989). Mazzocchi and Ianora
(1991) reported it as the most common
Calanus species in previous collections from
the Straits of Magellan, where it was present,
mainly as copepodite stages, only in the
Pacific sector. Hardy and Gunther (1935)
reported that the vertical distribution of C.
simillimus ranges up to 1000 m throughout
the area between South Georgia and the
Falkland Islands. They also noted that this
species exhibits marked and rapid diurnal
vertical migrations. In the present study, C.
simillimus was distributed throughout the
Straits of Magellan. Maximum abundances
were recorded in the Central area, where it
was found at all sampled depths.