7.4 Sagitta tasmanica Thomson, 1947
Sagitta serrato-dentata Krohn, 1853: p. 272, figs.
3, 4.
Spadella serratodentata Grassi, 1883: p. 19, pl. 1
figs. 8-10.
Sagitta serratodentata Strodtman, 1892: p. 39 -
von Ritter-Zahony, 191lb: p. 22, figs. 21, 22 -
Germain and Joubin, 1916: p. 41, pl. 3 figs. 12, 13,
19-21.
Sagitta serratodentata tasmanica Thomson,
1947: p. 15, figs 1-3- Tokioka, 1959: p. 364, figs.
5, 7, 8.
Sagitta tasmanica Furnestin, 1957: p. 148, fig. 20,
p. 151, fig. 54a-f- Fagetti, 1958a: p. 46, fig. 7- Alvarifio, 1961: p. 71, fig. 6- Fagetti, 1968: p. 123,
pl. 1 fig. a,b, pl. 3, figs. a-c- Ducret, 1968: p. 116,
fig. 19a- Alvarifio, 1969: pp. 188, 189, fig. 63a-d,
fig. 64a-f- Pierrot-Bults, 1974: p. 220, figs. 4, 5Boltovskoy, 1981: p. 786, fig. 256 21a-d.
Sagitta selkizki Fagetti, 1958b: p. 125, pl. 1, figs.
a-d.
Serratosagitta tasmanica Lutschinger, 1993: p.
33, fig. 17.
Body length -
10-24.5 mm
Description. Body elongated and rigid; total
length/caudallength proportions varying from
21-33 %. Anterior fins beginning posterior to
ventral ganglion. Posterior fins longer than anterior. Anterior portions ofboth anterior and posterior fins partially lacking rays. A narrow, barely visible band unites anterior and posterior fins.
Posterior fins reaching seminal receptacles but
not caudal fin. Mature and full receptacles appear as dark bulges. Mature ovaries variable in
length and sometimes reaching beyond ventral
ganglion in large specimens. Oocytes generally
arranged in two rows but sometimes aligned in a
single row. Eye pigment distributed in three
branches. The number of hooks varies from 6-9
(more hooks observed in larger specimens).
Hooks on head saw-edged at high magnification
and appear as small mammellar protrusions
(Fig. 7.4.2). Teeth vary from 4-6 anteriorly, and
8-15 posteriorly. Corona ciliata ( ciliary loop) elliptical in shape, visible in very few specimens
only after staining with methyl blue. Corona begins in front of eyes and extends onto neck and
trunk. Distance from ventral ganglion twice the
length of the ganglion. In large specimens (2024 mm) the corona is 2.5-3 mm in length. There
are no intestina! diverticulae.
Remarks
This was the most abundant species in the Straits
of Magellan, representing 75 o/o of the chaetognaths sampled (Ghirardelli et al. 1995). The species shows considerable individual variability in
size at sexual maturity, depending on the sampling area and depth. According to Pierrot-Bults
(1974), the anterior portion of the anterior fins
lacks rays, whereas Alvarino ( 1969) reports them
as present. Fagetti (1968) found specimens in
which the anterior fins lacked rays in southern
Chilean regions, whereas they were present in
northern specimens. In our specimens, the rays
were partially lacking in both anterior and posterior fins. According to Fagetti (1968), the arrangement of the oocytes in a single or double
row depends on the age of the specimens. Immature specimens have a double row of oocytes
whereas mature specimens have only a single
row. According to the same author, in southern
Chilean waters individuals were already mature
when 8-10 mm in length. Alvarifio (1969) and
Sagitta serrato-dentata Krohn, 1853: p. 272, figs.
3, 4.
Spadella serratodentata Grassi, 1883: p. 19, pl. 1
figs. 8-10.
Sagitta serratodentata Strodtman, 1892: p. 39 -
von Ritter-Zahony, 191lb: p. 22, figs. 21, 22 -
Germain and Joubin, 1916: p. 41, pl. 3 figs. 12, 13,
19-21.
Sagitta serratodentata tasmanica Thomson,
1947: p. 15, figs 1-3- Tokioka, 1959: p. 364, figs.
5, 7, 8.
Sagitta tasmanica Furnestin, 1957: p. 148, fig. 20,
p. 151, fig. 54a-f- Fagetti, 1958a: p. 46, fig. 7- Alvarifio, 1961: p. 71, fig. 6- Fagetti, 1968: p. 123,
pl. 1 fig. a,b, pl. 3, figs. a-c- Ducret, 1968: p. 116,
fig. 19a- Alvarifio, 1969: pp. 188, 189, fig. 63a-d,
fig. 64a-f- Pierrot-Bults, 1974: p. 220, figs. 4, 5Boltovskoy, 1981: p. 786, fig. 256 21a-d.
Sagitta selkizki Fagetti, 1958b: p. 125, pl. 1, figs.
a-d.
Serratosagitta tasmanica Lutschinger, 1993: p.
33, fig. 17.
Body length -
10-24.5 mm
Description. Body elongated and rigid; total
length/caudallength proportions varying from
21-33 %. Anterior fins beginning posterior to
ventral ganglion. Posterior fins longer than anterior. Anterior portions ofboth anterior and posterior fins partially lacking rays. A narrow, barely visible band unites anterior and posterior fins.
Posterior fins reaching seminal receptacles but
not caudal fin. Mature and full receptacles appear as dark bulges. Mature ovaries variable in
length and sometimes reaching beyond ventral
ganglion in large specimens. Oocytes generally
arranged in two rows but sometimes aligned in a
single row. Eye pigment distributed in three
branches. The number of hooks varies from 6-9
(more hooks observed in larger specimens).
Hooks on head saw-edged at high magnification
and appear as small mammellar protrusions
(Fig. 7.4.2). Teeth vary from 4-6 anteriorly, and
8-15 posteriorly. Corona ciliata ( ciliary loop) elliptical in shape, visible in very few specimens
only after staining with methyl blue. Corona begins in front of eyes and extends onto neck and
trunk. Distance from ventral ganglion twice the
length of the ganglion. In large specimens (2024 mm) the corona is 2.5-3 mm in length. There
are no intestina! diverticulae.
Remarks
This was the most abundant species in the Straits
of Magellan, representing 75 o/o of the chaetognaths sampled (Ghirardelli et al. 1995). The species shows considerable individual variability in
size at sexual maturity, depending on the sampling area and depth. According to Pierrot-Bults
(1974), the anterior portion of the anterior fins
lacks rays, whereas Alvarino ( 1969) reports them
as present. Fagetti (1968) found specimens in
which the anterior fins lacked rays in southern
Chilean regions, whereas they were present in
northern specimens. In our specimens, the rays
were partially lacking in both anterior and posterior fins. According to Fagetti (1968), the arrangement of the oocytes in a single or double
row depends on the age of the specimens. Immature specimens have a double row of oocytes
whereas mature specimens have only a single
row. According to the same author, in southern
Chilean waters individuals were already mature
when 8-10 mm in length. Alvarifio (1969) and