3.22 Aetideus australis Vervoort 1957
Euaetideus australis Vervoort, 1957: p. 46,
figs. 16-19, 20a - Park, 1978: p. 105, figs. 2,
3.
Aetideus australis Bradford, 1971a: p. 19,
figs. 5, 6a, 7 - Bradford and Jillett, 1980: p.
14, fig. 6.
Body length -
females: 1.76-1.96mm (12 specimens)
males: 1.55-1.57 mm (3 specimens)
Female. Cephalothorax 2.5 times longer
than wide. Proportional lengths of
cephalothorax and abdomen 77: 23. Head
resembling pointed arch in dorsal view,
tapering ventrally into large bifurcated
rostrum with strong base and large U-shaped
excavation between points. Posterior corners
of last thoracic somite produced distally into
large spiniform processes that become more
subtle at extremities and reaching half length
of second abdominal somite. Proportional
lengths of abdominal somites and furca
32:14:10:16:28: = 100. Genital somite
slightly wider than long in dorsal view, with
widest part at mid-length. Very conspicuous
seminal receptacles both in dorsal and lateral
views, with distal end expanded into large
bursa. Caudal rami about 3 times longer than
wide, with long fragile hairs on inner margins.
P4 Bl with row of strong, wide spinules at
base of internal seta.
Male. Cephalothorax more slender than
female, 2.7 times longer than wide. Proportional lengths of cephalothorax and
abdomen 74: 26. Rostrum absent. Posterior
corners of last thoracic somite produced
distally into spiniform processes extending
beyond distal margin of first abdominal
somite. Proportional lengths of abdominal
somites and furca 18: 22 : 18: 22 : 18: 2 = 100.
Anal somite extremely reduced, hidden
between fourth abdominal somite and furca.
Caudal rami 3.2 times longer than wide. P5
single, uniramous, 5-jointed; third joint the
longest. Fourth joint with few short bristles
on distal surface; last joint very short, with
Aetideus australis
133
longitudinal row of dense bristles that also
ornate tip.
Remarks
A. australis was described by Vervoort (1957)
as Euaetideus a. This species is very similar to
A. armatus but, also according to Bradford
and Jillett (1980) and Park (1978: Euaetideus
australis), A. australis is characterized and
distinguished by its longer posterior thoracic
points and, in the female, by the genital
somite, which is widest at the middle in
dorsal view (in A. armatus it is widest anterior
to the middle). This latter difference is very
evident when Mediterranean specimens of
A. australis and A. armatus are compared.
The male can be readily distinguished by the
relatively long caudal rami, which are about
3 times longer than wide; according to
Tanaka (1957), the caudal rami are about 2
times longer than wide in A. armatus. In our
specimens we did not observe (up to 7 X 10 4
magnification at SEM) the chitinous thickenings on the anterior integument reported by
Bradford (1971a).
Distribution
A. australis was originally reported from
Antarctic and sub-Antarctic waters, in the
Indian Ocean and Australian sector of the
Pacific (Vervoort 1957). It was later found in
Antarctic and sub-Antarctic areas of the
Pacific Ocean by Park (1978). According to
Bradford (1971a), A. australis was sampled
in the SW Pacific (0-1000 m depth) and in
the SE Atlantic (0-3OOm depth). It has
been recorded once north of the Subtropical
Convergence off Southern Africa (Bradford
1971 a) and once south of the Antarctic
Convergence (Vervoort 1957). In Chilean
waters, only A. armatus (very similar to A.
australis) is reported (Ramirez 1969; Arcos
1975; Ramirez and Dinofrio 1976). In the
present study, A. australis was present
throughout the water column at all stations
in the Pacific area of the Straits of Magellan.
A few individuals were also sampled from
200-250m off Cape Froward.
Euaetideus australis Vervoort, 1957: p. 46,
figs. 16-19, 20a - Park, 1978: p. 105, figs. 2,
3.
Aetideus australis Bradford, 1971a: p. 19,
figs. 5, 6a, 7 - Bradford and Jillett, 1980: p.
14, fig. 6.
Body length -
females: 1.76-1.96mm (12 specimens)
males: 1.55-1.57 mm (3 specimens)
Female. Cephalothorax 2.5 times longer
than wide. Proportional lengths of
cephalothorax and abdomen 77: 23. Head
resembling pointed arch in dorsal view,
tapering ventrally into large bifurcated
rostrum with strong base and large U-shaped
excavation between points. Posterior corners
of last thoracic somite produced distally into
large spiniform processes that become more
subtle at extremities and reaching half length
of second abdominal somite. Proportional
lengths of abdominal somites and furca
32:14:10:16:28: = 100. Genital somite
slightly wider than long in dorsal view, with
widest part at mid-length. Very conspicuous
seminal receptacles both in dorsal and lateral
views, with distal end expanded into large
bursa. Caudal rami about 3 times longer than
wide, with long fragile hairs on inner margins.
P4 Bl with row of strong, wide spinules at
base of internal seta.
Male. Cephalothorax more slender than
female, 2.7 times longer than wide. Proportional lengths of cephalothorax and
abdomen 74: 26. Rostrum absent. Posterior
corners of last thoracic somite produced
distally into spiniform processes extending
beyond distal margin of first abdominal
somite. Proportional lengths of abdominal
somites and furca 18: 22 : 18: 22 : 18: 2 = 100.
Anal somite extremely reduced, hidden
between fourth abdominal somite and furca.
Caudal rami 3.2 times longer than wide. P5
single, uniramous, 5-jointed; third joint the
longest. Fourth joint with few short bristles
on distal surface; last joint very short, with
Aetideus australis
133
longitudinal row of dense bristles that also
ornate tip.
Remarks
A. australis was described by Vervoort (1957)
as Euaetideus a. This species is very similar to
A. armatus but, also according to Bradford
and Jillett (1980) and Park (1978: Euaetideus
australis), A. australis is characterized and
distinguished by its longer posterior thoracic
points and, in the female, by the genital
somite, which is widest at the middle in
dorsal view (in A. armatus it is widest anterior
to the middle). This latter difference is very
evident when Mediterranean specimens of
A. australis and A. armatus are compared.
The male can be readily distinguished by the
relatively long caudal rami, which are about
3 times longer than wide; according to
Tanaka (1957), the caudal rami are about 2
times longer than wide in A. armatus. In our
specimens we did not observe (up to 7 X 10 4
magnification at SEM) the chitinous thickenings on the anterior integument reported by
Bradford (1971a).
Distribution
A. australis was originally reported from
Antarctic and sub-Antarctic waters, in the
Indian Ocean and Australian sector of the
Pacific (Vervoort 1957). It was later found in
Antarctic and sub-Antarctic areas of the
Pacific Ocean by Park (1978). According to
Bradford (1971a), A. australis was sampled
in the SW Pacific (0-1000 m depth) and in
the SE Atlantic (0-3OOm depth). It has
been recorded once north of the Subtropical
Convergence off Southern Africa (Bradford
1971 a) and once south of the Antarctic
Convergence (Vervoort 1957). In Chilean
waters, only A. armatus (very similar to A.
australis) is reported (Ramirez 1969; Arcos
1975; Ramirez and Dinofrio 1976). In the
present study, A. australis was present
throughout the water column at all stations
in the Pacific area of the Straits of Magellan.
A few individuals were also sampled from
200-250m off Cape Froward.