3.5 Metridia lucens Boeck 1864
Metridia lucens Boeck, 1864: p. 14 - Sars,
1903: p. 113, pI. 77 - Brodskii, 1950: p. 294,
fig. 200 - Ramirez, 1969: pI. 68, pI. 12 figs.
84,86, 87, 89.
Paracalanus hibemicus Brady and Robertson,
1873: p. 126, pI. 8 figs. 1-3.
Metridia hibemica Giesbrecht, 1892: pp. 61,
341, pI. 33 figs. 2, 12, 16, 22, 28, 36, 39.
Body length -
females: 2.62-3.21 mm (25 specimens)
males: 1.80-2.00mm (20 specimens)
Female. Cephalothorax
elongated
and
ovate. Head convex on dorsal side and
strongly curved in lateral view. Posterior
corners of last thoracic somite with small
acute apex. Al somewhat longer than last
thoracic somite. Proportional lengths of
cephalothorax and abdomen 65: 35; proportionallengths of abdominal somites and furca
41 :24: 16: 19 = 100. P5 uniramous, 3jointed, sometimes with defined 4th segment.
Distal joint bearing apical setae and one
rather long spine on outer margin (in rare
cases there are 2 spines). Second joint
generally with similar outer spine. P5 highly
variable for the number of joints and the
presence or absence of an outer spine on 2nd
joint. P5 characterized by relative length of
inner apical seta with respect to distal joint,
i.e. this seta clearly longer than two others.
Male. General shape as female, but dorsal
side of head smoother in lateral view. Proportionallengths of cephalothorax and abdomen
63 : 37; proportional lengths of abdominal
Family Metridinidae
somites and furca 14: 19: 18: 18: 13: 18
= 100. P5 asymmetrical. Third joint of right
P5 bearing spiniform process on inner side as
long or slightly longer than terminal joint.
Process denticulated distally along inner
margin. Distal joint of right leg. larger than
corresponding joint of left leg. Left P5 with
2nd joint bearing thick bundle of hairs on
distal inner margin; 3rd joint with rather long
spine and round, lamellar process. Fourth
joint bearing 2 strong spines on inner margin.
Remarks
The specimens examined closely resemble
M. lucens but show a marked variability in
many morphological features, especially in
size, the lateral profile of the female head,
female P5, and length of the spiniform process on right P5 of the male. Interestingly,
some of our male specimens had P5 with
reversed rami. Brodskii (1950) described M.
pacifica, closely allied to M. lucens, as a new
species from northern cold waters of the
Pacific. According to Brodskii's taxonomic
key, our females concord with M. lucens. On
the other hand, males have caudal rami that
are longer than the anal somite and the left
ramus of the P5 bears 2 spines on the inner
margin as in M. pacifica. This is why this
species was identified as M. pacifica in a
previous study on copepods of the Straits of
Magellan (Mazzocchi and lanora 1991). In
fact, the systematic literature is contradictory
and insufficient to clearly distinguish between
the two species. Such uncertainties emerge
also from the work of Tanaka (1963), who
found specimens resembling M. pacifica but
reported the female P5 of M. lucens in his fig.
5c (p. 22).
Metridia lucens Boeck, 1864: p. 14 - Sars,
1903: p. 113, pI. 77 - Brodskii, 1950: p. 294,
fig. 200 - Ramirez, 1969: pI. 68, pI. 12 figs.
84,86, 87, 89.
Paracalanus hibemicus Brady and Robertson,
1873: p. 126, pI. 8 figs. 1-3.
Metridia hibemica Giesbrecht, 1892: pp. 61,
341, pI. 33 figs. 2, 12, 16, 22, 28, 36, 39.
Body length -
females: 2.62-3.21 mm (25 specimens)
males: 1.80-2.00mm (20 specimens)
Female. Cephalothorax
elongated
and
ovate. Head convex on dorsal side and
strongly curved in lateral view. Posterior
corners of last thoracic somite with small
acute apex. Al somewhat longer than last
thoracic somite. Proportional lengths of
cephalothorax and abdomen 65: 35; proportionallengths of abdominal somites and furca
41 :24: 16: 19 = 100. P5 uniramous, 3jointed, sometimes with defined 4th segment.
Distal joint bearing apical setae and one
rather long spine on outer margin (in rare
cases there are 2 spines). Second joint
generally with similar outer spine. P5 highly
variable for the number of joints and the
presence or absence of an outer spine on 2nd
joint. P5 characterized by relative length of
inner apical seta with respect to distal joint,
i.e. this seta clearly longer than two others.
Male. General shape as female, but dorsal
side of head smoother in lateral view. Proportionallengths of cephalothorax and abdomen
63 : 37; proportional lengths of abdominal
Family Metridinidae
somites and furca 14: 19: 18: 18: 13: 18
= 100. P5 asymmetrical. Third joint of right
P5 bearing spiniform process on inner side as
long or slightly longer than terminal joint.
Process denticulated distally along inner
margin. Distal joint of right leg. larger than
corresponding joint of left leg. Left P5 with
2nd joint bearing thick bundle of hairs on
distal inner margin; 3rd joint with rather long
spine and round, lamellar process. Fourth
joint bearing 2 strong spines on inner margin.
Remarks
The specimens examined closely resemble
M. lucens but show a marked variability in
many morphological features, especially in
size, the lateral profile of the female head,
female P5, and length of the spiniform process on right P5 of the male. Interestingly,
some of our male specimens had P5 with
reversed rami. Brodskii (1950) described M.
pacifica, closely allied to M. lucens, as a new
species from northern cold waters of the
Pacific. According to Brodskii's taxonomic
key, our females concord with M. lucens. On
the other hand, males have caudal rami that
are longer than the anal somite and the left
ramus of the P5 bears 2 spines on the inner
margin as in M. pacifica. This is why this
species was identified as M. pacifica in a
previous study on copepods of the Straits of
Magellan (Mazzocchi and lanora 1991). In
fact, the systematic literature is contradictory
and insufficient to clearly distinguish between
the two species. Such uncertainties emerge
also from the work of Tanaka (1963), who
found specimens resembling M. pacifica but
reported the female P5 of M. lucens in his fig.
5c (p. 22).