3.2 Haloptilus acutifrons
Giesbrecht 1892
Hemicalanus acutifrons Giesbrecht, 1892:
p. 384, pI. 3 fig. 11, pI. 27 figs. 4, 12, 18, 26,
pI. 42 figs. 12, 20.
Hemicalanus spinifrons Sars, 1900: p. 95,
pI. 28 figs. 1-12.
Haloptilus acutifrons Sars, 1924-1925: p.
250, pI. 74 figs. 1-11- Brodskii, 1950: p. 364,
fig. 255 - Grice, 1962: p. 223, pI. 25 figs. 1-8
- Owre and Foyo, 1967: p. 81, figs. 523525.
Body length -
females: 4.35-4.66mm (6 specimens)
Female. Body transparent. Cephalothorax
2.8 times longer than wide. Proportional
lengths of cephalothorax and abdomen 84:
16. Forehead produced into long, strong
spine, slightly bent downward, with subtle
filamentous rostrum. Al exceeds end of body
by 5-7 distal joints. Mandibular blade with
strong distal tooth and group of 3 much
smaller teeth on opposite margin. Proportionallengths of abdominal somites and furca
39:11:9:14:27 = 100. P5 biramous, symmetrical; last exopodal joint with 2 terminal
spines of different length. Longer of 2 spines
slightly shorter than same joint. Endopod not
reaching distal margin of Re2.
Haloptilus acutifrons
31
Remarks
Haloptilus acutifrons resembles H. oxycephalus, the latter of which is often recorded
from Antarctic and sub-Antarctic seas (Park
1988). As discussed by Park (1988), the two
species are practically indistinguishable; the
only useful anatomical detail to determine H.
acutifrons is the relatively shorter cephalic
spine. H. acutifrons is also smaller than H.
oxycephalus; both species, however, show a
wide size range depending on the sampling
region and latitude. Our specimens show a
size range overlapping that of H. oxycephalus,
but the shape of the forehead is exactly as
always reported for H. acutifrons.
Distribution
Oceanic, cosmopolitan species with a wide
geographical distribution range both in the
Northern and Southern hemispheres. Farran
(1929) recorded Haloptilus acutifrons off
New Zealand during the "Terra Nova
Expedition". It was found at a depth of 4001000 m in the central part of the Arctic
Ocean, and below 1000 m in Greenland
waters; it can also occur at shallower depths
such as 100 m or 50 m, and even at the surface
(Brodskii 1950). This species was also
recorded from 0-2000 m in the Mediterranean Sea (Scotto di Carlo et al. 1984).
Vervoort (1957) summarized records of its
geographical distribution and Roe (1972) discusses its vertical distribution. In the present
study, H. acutifrons was only found from
100-400 m at two stations in the Pacific area
of the Straits of Magellan.
Giesbrecht 1892
Hemicalanus acutifrons Giesbrecht, 1892:
p. 384, pI. 3 fig. 11, pI. 27 figs. 4, 12, 18, 26,
pI. 42 figs. 12, 20.
Hemicalanus spinifrons Sars, 1900: p. 95,
pI. 28 figs. 1-12.
Haloptilus acutifrons Sars, 1924-1925: p.
250, pI. 74 figs. 1-11- Brodskii, 1950: p. 364,
fig. 255 - Grice, 1962: p. 223, pI. 25 figs. 1-8
- Owre and Foyo, 1967: p. 81, figs. 523525.
Body length -
females: 4.35-4.66mm (6 specimens)
Female. Body transparent. Cephalothorax
2.8 times longer than wide. Proportional
lengths of cephalothorax and abdomen 84:
16. Forehead produced into long, strong
spine, slightly bent downward, with subtle
filamentous rostrum. Al exceeds end of body
by 5-7 distal joints. Mandibular blade with
strong distal tooth and group of 3 much
smaller teeth on opposite margin. Proportionallengths of abdominal somites and furca
39:11:9:14:27 = 100. P5 biramous, symmetrical; last exopodal joint with 2 terminal
spines of different length. Longer of 2 spines
slightly shorter than same joint. Endopod not
reaching distal margin of Re2.
Haloptilus acutifrons
31
Remarks
Haloptilus acutifrons resembles H. oxycephalus, the latter of which is often recorded
from Antarctic and sub-Antarctic seas (Park
1988). As discussed by Park (1988), the two
species are practically indistinguishable; the
only useful anatomical detail to determine H.
acutifrons is the relatively shorter cephalic
spine. H. acutifrons is also smaller than H.
oxycephalus; both species, however, show a
wide size range depending on the sampling
region and latitude. Our specimens show a
size range overlapping that of H. oxycephalus,
but the shape of the forehead is exactly as
always reported for H. acutifrons.
Distribution
Oceanic, cosmopolitan species with a wide
geographical distribution range both in the
Northern and Southern hemispheres. Farran
(1929) recorded Haloptilus acutifrons off
New Zealand during the "Terra Nova
Expedition". It was found at a depth of 4001000 m in the central part of the Arctic
Ocean, and below 1000 m in Greenland
waters; it can also occur at shallower depths
such as 100 m or 50 m, and even at the surface
(Brodskii 1950). This species was also
recorded from 0-2000 m in the Mediterranean Sea (Scotto di Carlo et al. 1984).
Vervoort (1957) summarized records of its
geographical distribution and Roe (1972) discusses its vertical distribution. In the present
study, H. acutifrons was only found from
100-400 m at two stations in the Pacific area
of the Straits of Magellan.