3.38 Spinocalanus brevicaudatus
Brodskii 1950
Spinocalanus brevicaudatus Brodskii, 1950:
p. 136, fig. 55 - Semenova, 1962: p. 1571,
figs. 1-4 - Damkaer, 1975: p. 53, figs. 130136, 157.
See Damkaer (1975) for more complete
synonymy.
Body length -
females: 1.55-1.80mm (20 specimens)
male:
1.57 mm (1 specimen)
Female. Cephalothorax ovoid in dorsal view,
2.6 times longer than wide; head slightly
truncated; rostrum absent. Posterior corners
of last thoracic somite rounded, not prolonged. Proportional lengths of cephalothorax
and abdomen 78: 22; proportional lengths of
abdominal somites and furca 37: 17: 16: 19: 11
= tOO. Genital somite slightly longer than the
following somite and protruding ventrally.
Ventral surface of genital somite ornated
with tuft of long hairs below genital aperture.
Borders of abdominal somites ornated with
fringes. Caudal rami as long as wide, symmetrical, with long hairs on dorsal side. P1
Re3 posterior surface without spines; P2 B1
inner posterior surface with setules; P3 B1
outer surface with few setules and spines,
inner margins with hairs; P4 B2 posterior
surface lacks ornamentation.
Male. Cephalothorax elongated, rectangular
in dorsal view, 2.6 times longer than wide.
Posterior corners of last thoracic somite
prolonged into small rounded processes
curved outwards. Proportional lengths
of cephalothorax and abdomen 44: 19.
Family Spinocalanidae
Abdomen 5-segmented; anal somite very
short, almost hidden between the fourth
somite and furca. Proportional lengths of
abdominal somites and furca 11: 35 : 20: 21 :
3: to = 100. Caudal rami about as long as
wide, symmetrical. P5 birameus; left B1
reaching 113 length of right B2; left B2 reaching middle of right ReI. Right leg, including
terminal blade, longer than left. Each Re3 is
subtle and stylet-shaped. Endopods styletshaped, right Ri longer than left. Inner edge
of left Re2, Re3 with long hairs.
Remarks
The systematics of the family Spinocalaoidae
is rather complex and confusing, particularly
for the genus Spinocalanus, which now includes 26 species (Razouls 1993). Since they
are easily damaged, it is difficult to find specimens in which the swimming legs are intact,
a prerequisite for their correct taxonomic
identification. To date, the best revision of
this family is still the one by Damkaer (1975).
S. brevicaudatus had been known as a
larger form of S. abyssalis until Brodskii
(1950) recognized it as a separate species.
Mazzocchi and lanora (1991) reported S.
terranovae from the previous cruise in the
Straits of Magellan. Their identification was
based on a single female specimen with
damaged swimming legs. Therefore, it
probably should be corrected to S. brevicaudatus.
S. brevicaudatus and S. terranovae have
overlapping size ranges; the former species
has a somewhat lower size limit (1.4-2.4mm
versus 1.7-2.2mm). Due to the scarce
iconographic information for both species,
the two appear very similar in morphology.
Brodskii 1950
Spinocalanus brevicaudatus Brodskii, 1950:
p. 136, fig. 55 - Semenova, 1962: p. 1571,
figs. 1-4 - Damkaer, 1975: p. 53, figs. 130136, 157.
See Damkaer (1975) for more complete
synonymy.
Body length -
females: 1.55-1.80mm (20 specimens)
male:
1.57 mm (1 specimen)
Female. Cephalothorax ovoid in dorsal view,
2.6 times longer than wide; head slightly
truncated; rostrum absent. Posterior corners
of last thoracic somite rounded, not prolonged. Proportional lengths of cephalothorax
and abdomen 78: 22; proportional lengths of
abdominal somites and furca 37: 17: 16: 19: 11
= tOO. Genital somite slightly longer than the
following somite and protruding ventrally.
Ventral surface of genital somite ornated
with tuft of long hairs below genital aperture.
Borders of abdominal somites ornated with
fringes. Caudal rami as long as wide, symmetrical, with long hairs on dorsal side. P1
Re3 posterior surface without spines; P2 B1
inner posterior surface with setules; P3 B1
outer surface with few setules and spines,
inner margins with hairs; P4 B2 posterior
surface lacks ornamentation.
Male. Cephalothorax elongated, rectangular
in dorsal view, 2.6 times longer than wide.
Posterior corners of last thoracic somite
prolonged into small rounded processes
curved outwards. Proportional lengths
of cephalothorax and abdomen 44: 19.
Family Spinocalanidae
Abdomen 5-segmented; anal somite very
short, almost hidden between the fourth
somite and furca. Proportional lengths of
abdominal somites and furca 11: 35 : 20: 21 :
3: to = 100. Caudal rami about as long as
wide, symmetrical. P5 birameus; left B1
reaching 113 length of right B2; left B2 reaching middle of right ReI. Right leg, including
terminal blade, longer than left. Each Re3 is
subtle and stylet-shaped. Endopods styletshaped, right Ri longer than left. Inner edge
of left Re2, Re3 with long hairs.
Remarks
The systematics of the family Spinocalaoidae
is rather complex and confusing, particularly
for the genus Spinocalanus, which now includes 26 species (Razouls 1993). Since they
are easily damaged, it is difficult to find specimens in which the swimming legs are intact,
a prerequisite for their correct taxonomic
identification. To date, the best revision of
this family is still the one by Damkaer (1975).
S. brevicaudatus had been known as a
larger form of S. abyssalis until Brodskii
(1950) recognized it as a separate species.
Mazzocchi and lanora (1991) reported S.
terranovae from the previous cruise in the
Straits of Magellan. Their identification was
based on a single female specimen with
damaged swimming legs. Therefore, it
probably should be corrected to S. brevicaudatus.
S. brevicaudatus and S. terranovae have
overlapping size ranges; the former species
has a somewhat lower size limit (1.4-2.4mm
versus 1.7-2.2mm). Due to the scarce
iconographic information for both species,
the two appear very similar in morphology.