7.1 Sagitta decipiens Fowler, 1905
Sagitta decipiens Fowler, 1905: p. 70, pl. 5 figs.
32-35- Lea, 1955: p. 606, fig. 4- Neta, 1961: p. 27,
figs. 22-24- Vucetic, 1963: p. 67, fig. 7a- Ducret,
1968: p. 125, fig. 25- Fagetti, 1968: p. 162- Alvarifio, 1969: p. 245, figs. 87a-c, 88a-k - PierrotBults, 1979: p. 137, figs. 1 a,d, 2-4 - Boltovskoy,
1981: p. 788, fig. 256, 8- Bieri, 1991b: p. 221.
Sagitta neodecipiens Tokioka, 1959: p. 377, figs.
17-19, 20 - Ducret, 1962: p. 344, figs. 14-16, 18 -
Ducret, 1968: p. 125, fig. 25 - Gamulin, 1977:
p. 139- Pierrot-Bults, 1979: p. 138, figs. 1-5.
Mesosagitta decipiens Tokioka, 1965a: p. 348 -
Bieri 1991a, p. 131- Lutschinger, 1993: p. 28, fig.
13a,b.
Decipisagitta decipiens Bieri, 1991b: p. 223, fig. 3.
Body length -
14.5-17.5 mm
Description. Body elongated, flaccid and transparent; slightly swollen in posterior third, just
before caudal septum. Intestina! diverticulae
present but not always easy to distinguish. Small
head bearing 6-7 hooks. Number of teeth variable: 6-8 triangular anterior teeth and 6-14 posterior teeth. Proportionallength of tail with respect to total body length 24-28.5 %. Anterior
fins long and narrow with barely visible rays,
ending anteriorly behind ventral ganglion. Posterior fins with maximum width slightly behind
caudal septum, not reaching seminal vesicles.
Ovaries reaching posterior end or surpassing
anterior fins. When full, seminal vesicles flasklike in shape and characteristic of the species,
with a glandular anterior extremity. In the Magellan specimens, ripe seminal vesicles were not
observed; their position was at an equal distance
between the posterior and caudal fins. The species may differ in aspect due mainly to the caudal
region, which can be notably opaque when
sperm are ripe.
Remarks
There is much disaccord among systematicians
on the exact description of this species. In aur
specimens, the number ofhooks and teeth differ
from the number reported by other authors: 410 anterior and 6-18 posterior teeth (PierrotBults 1979) and 8-10 anterior and 19-22 posterior teeth (Alvarifio 1969). The proportional
length of the tail with respect to the total body
length is similar to that reported by Fagetti
(22.7-27.2 %), Alvarifio (25-29 %) and PierrotBults (25-32.7 %). Lutschinger (1993) draws
both anterior and posterior fins rayless in the
anterior region. The testicles are mature in specimens of 16 mm. In larger specimens, the characteristic club-shaped seminal receptacles are well
defined whereas the eggs are not yet mature. van
Ritter-Zahony (191la) reports that the length
var ies from 6-20 mm, whereas Pierrot-Bults
(1979) reports a maximum length of 13.5 mm.
Distribution
The species is mesoplanktonic and is widely distributed in all oceans including the Antarctic,
where it has been defined by David (1958) as an
"exotic species". In the Straits of Magellan, it was
sampled almost exclusively in the western sector,
but one specimen was also found in Baia Inutil.
Pierrot-Bults (1979) maintains that S. neodecipiens is synonymous with S. decipiens Fowler.
Sagitta decipiens Fowler, 1905: p. 70, pl. 5 figs.
32-35- Lea, 1955: p. 606, fig. 4- Neta, 1961: p. 27,
figs. 22-24- Vucetic, 1963: p. 67, fig. 7a- Ducret,
1968: p. 125, fig. 25- Fagetti, 1968: p. 162- Alvarifio, 1969: p. 245, figs. 87a-c, 88a-k - PierrotBults, 1979: p. 137, figs. 1 a,d, 2-4 - Boltovskoy,
1981: p. 788, fig. 256, 8- Bieri, 1991b: p. 221.
Sagitta neodecipiens Tokioka, 1959: p. 377, figs.
17-19, 20 - Ducret, 1962: p. 344, figs. 14-16, 18 -
Ducret, 1968: p. 125, fig. 25 - Gamulin, 1977:
p. 139- Pierrot-Bults, 1979: p. 138, figs. 1-5.
Mesosagitta decipiens Tokioka, 1965a: p. 348 -
Bieri 1991a, p. 131- Lutschinger, 1993: p. 28, fig.
13a,b.
Decipisagitta decipiens Bieri, 1991b: p. 223, fig. 3.
Body length -
14.5-17.5 mm
Description. Body elongated, flaccid and transparent; slightly swollen in posterior third, just
before caudal septum. Intestina! diverticulae
present but not always easy to distinguish. Small
head bearing 6-7 hooks. Number of teeth variable: 6-8 triangular anterior teeth and 6-14 posterior teeth. Proportionallength of tail with respect to total body length 24-28.5 %. Anterior
fins long and narrow with barely visible rays,
ending anteriorly behind ventral ganglion. Posterior fins with maximum width slightly behind
caudal septum, not reaching seminal vesicles.
Ovaries reaching posterior end or surpassing
anterior fins. When full, seminal vesicles flasklike in shape and characteristic of the species,
with a glandular anterior extremity. In the Magellan specimens, ripe seminal vesicles were not
observed; their position was at an equal distance
between the posterior and caudal fins. The species may differ in aspect due mainly to the caudal
region, which can be notably opaque when
sperm are ripe.
Remarks
There is much disaccord among systematicians
on the exact description of this species. In aur
specimens, the number ofhooks and teeth differ
from the number reported by other authors: 410 anterior and 6-18 posterior teeth (PierrotBults 1979) and 8-10 anterior and 19-22 posterior teeth (Alvarifio 1969). The proportional
length of the tail with respect to the total body
length is similar to that reported by Fagetti
(22.7-27.2 %), Alvarifio (25-29 %) and PierrotBults (25-32.7 %). Lutschinger (1993) draws
both anterior and posterior fins rayless in the
anterior region. The testicles are mature in specimens of 16 mm. In larger specimens, the characteristic club-shaped seminal receptacles are well
defined whereas the eggs are not yet mature. van
Ritter-Zahony (191la) reports that the length
var ies from 6-20 mm, whereas Pierrot-Bults
(1979) reports a maximum length of 13.5 mm.
Distribution
The species is mesoplanktonic and is widely distributed in all oceans including the Antarctic,
where it has been defined by David (1958) as an
"exotic species". In the Straits of Magellan, it was
sampled almost exclusively in the western sector,
but one specimen was also found in Baia Inutil.
Pierrot-Bults (1979) maintains that S. neodecipiens is synonymous with S. decipiens Fowler.