Gnathostomulida from the Otago Peninsula, southern New Zealand
Author
Sterrer, Wolfgang
text
Zootaxa
2006
2006-04-13
1172
1
19
journal article
27070
10.5281/zenodo.2645647
e1ec4acf-3db4-4cd9-97fa-5645a0685e5b
1175-5326
2645647
321024B7-8CE2-45F0-B683-70D600C2215A
Gnathostomula
cf.
salotae
Sterrer, 1991
(Fig. 7.1–7.8)
Material
Six adults, one juvenile from samples SI 10 and SI 16.
Distribution
Tonga
(
Sterrer 1991a
).
Description
Organization and behavior.
Adults are small and plump, ranging from
300 to 400 µm
(mean
352.50 µm
) in length, and
55 to 70 µm
in width (
66.25 µm
) at U 53.08 (body index 5.43). There is a short tail region. Rostrum
50.75 µm
long and
52.50 µm
wide at U 11.46 (index 0.99). Of the sensorium, apicalia were to
15 µm
long, frontalia to
35 µm
, and lateralia to
40 µm
.
FIGURE 7.
Gnathostomula
cf.
salotae
.
7.1 Habitus; 7.2 Bursa; 7.3–7.4 Male copulatory organ of two specimens; 7.5–7.6 Two aspects of sperm squeezed from the testes; 7.7–7.8 Basal plates and jaws of two specimens (7.8 also shows the jugum, top). 7.5–7.8 to the same scale as Fig. 1.
Digestive tract.
The basal plate is
7.33 µm
long and 20.00 µm wide (index 0.37). Its mediorostral margin is finely dentate, with a stronger, medially pointing tooth at the anterior tip. The lateral wings may be curved rostrally. Jaws are
15.60 µm
long, with 6 teeth in the dorsal,
8 in
the median, and 11 teeth in the ventral row. The crescentshaped jugum is
7.33 µm
long and 16.00 µm wide.
Male
system.
The paired, follicular testes extend from U 56.67 to U 80.42. The penis extends from U 66.46 to U 82.53. It is
39–60 µm
(
50.60 µm
) long but only
2.8 µm
wide. Sperm is tiny,
2 µm
in diameter, with a round to beanshaped dense core that is often surrounded by a lucid coating.
Female system.
The largest egg, about
50 µm
in diameter, extends from U 41.7 to U 56.7. The bursa copulatrix is immediately behind it, measuring
35 µm
in length and
15 µm
in width.
| Mean |
SD |
Max |
Min |
n |
| Body length of adults |
352.50 |
49.92 |
400 |
300 |
4 |
| Body width of adults |
66.25 |
7.50 |
70 |
55 |
4 |
| Body index of adults |
5.43 |
1.35 |
7.27 |
4.29 |
4 |
| Rostrum index of adults |
0.99 |
0.18 |
1.24 |
0.83 |
4 |
| Jaw length |
15.60 |
0.89 |
17 |
15 |
5 |
| Basal plate length |
7.33 |
0.58 |
8 |
7 |
3 |
| Basal plate width |
20.00 |
2.00 |
22 |
18 |
3 |
| Basal plate index |
0.37 |
0.04 |
0.40 |
0.32 |
3 |
| Penis stylet length |
50.60 |
8.32 |
60 |
39 |
5 |
| Sperm length |
2.00 |
0.00 |
2 |
2 |
3 |
| Sperm width |
2.00 |
0.00 |
2 |
2 |
3 |
| Sperm index |
1.00 |
0.00 |
1.00 |
1.00 |
3 |
Discussion
Gnathostomula
is the most widespread and eurytopic of all genera, occurring from arctic to tropical waters, and from the intertidal to 400 meters depth. It is also taxonomically the most elusive genus, combining a paucity of speciesspecific characters (of which most such as jaw teeth — are at the lower limit of light microscopy) with high intraspecific variability (
Sterrer 2001
) — each specimen looks just a little different. Of 20 currently valid species (plus several unidentified spp.,
Sterrer 2001
), one (
G. maorica
Sterrer, 1991
) was described from
New Zealand
, but differs from Portobello specimens by its much greater body length (
450–730 µm
) and much shorter penis stylet (
26–33 µm
). Penis stylet length also rules out
G. armata
Riedl, 1971
(
65 µm
),
G. axi
Kirsteuer, 1964
(
65 µm
),
G. brunidens
Riedl, 1971
(
61–68 µm
),
G. costata
Ehlers & Ehlers, 1973
(
17 µm
),
G. jenneri
Riedl, 1971
((
61–68 µm
), G.
karlingi
Riedl, 1971
(
32 µm
),
G. maldivarum
Gerlach, 1958
(
18 µm
),
G. mediocristata
Riedl, 1971
(
80µm
),
G. microstyla
Riedl, 1971
(
18–35 µm
),
G. murmanica
Mamkaev, 1961
(
92–96 µm
),
G. nigrostoma
Riedl, 1971
(
37 µm
) and
G. uncinata
Sterrer, 1998
(
35 µm
). Of the remaining species,
G. salotae
(described by Sterrer 1991 from
Tonga
) is in best agreement with most features of the Portobello specimens, with one exception: the round sperm, which are otherwise only reliably reported from
G. jenneri
Riedl, 1991
.
Suborder Conophoralia
Sterrer, 1972
Family
Austrognathiidae Sterrer, 1971
Austrognatharia australis
n. sp.
(Fig.8.1–8.7, 9.1–9.4)
Type material
Holotype
one adult from sample SI 16, in squeeze preparation,
NZNM
W.1536. Further material: One juvenile from the same sample.
Etymology
This is the southernmost species of the genus.
Diagnosis
Slender
Austrognatharia
(body index 13.63) with slender rostrum (index 1.15) and abundant adhesive papillae in the tail region. Basal plate 7.00 µm long, 26.00 µm wide (index 0.27). Jaws
26.50 µm
long, with one tooth in dorsal and 3.00 teeth in ventral row. Conuli to
23 µm
long and
7 µm
wide (index 3.54), with inconspicuous cingulum; hat flat, taking up less than 20% of total conulus length.
Description
:
Organization and behavior.
The single adult had a slender body (length
1090 µm
, width
80 µm
at U 32.1; body index 13.63). The rostrum is slender (
78 µm
long,
68 µm
wide at U 4.3; rostrum index 1.15). The tail region ends in a blunt cone which contains many adhesive papillae composed of bundles of rhabdoids. Of the sensorium, apicalia 1 were
20 µm
long, frontalia
51 µm
, and ventralia
45 µm
. Animals glide slowly, and occasionally perform peristaltic contractions.
Digestive tract.
The elongated mouth opening is surrounded by prepharyngeal glands. The somewhat goggleshaped basal plate is 7.00 µm long and 26.00 µm wide (index 0.27). Its rostral edge lacks a median lobe whereas the lateral lobes are comparatively prominent. There are 11 caudodorsally pointing teeth of which the median tooth and the lateralmost pair are much larger than the rest. Jaws are
26.50 µm
long, with a strong terminal tooth, a single, thin but broadly based dorsal tooth, and 3 delicate, equal teeth in the ventral row. The cauda is
7 µm
long.
Male
system.
The unpaired, dorsal testis extends from U 80.7 to U 87.2 where it empties into a glandular penis. The male pore is located ventrally at U 95. The testis contained 17 conuli of which two had twin cones. The largest conuli
23 µm
long and
7 µm
wide (conulus index 3.54). Conuli are slender, with a flat hat that takes up no more than 20% of total conulus length, and is no wider than the cone. The cingulum beneath the hat is inconspicuous, and sometimes curved upwards.
Female system.
The single specimen did not have a mature egg. Located between U 75.2 and U 80.7, the soft, globular bursa contained three fused conuli, with their cones in a grainy condition.
FIGURE 8.
Austrognatharia australis
nov. spec.
8.1 Head region; 8.2 Posterior body region with bursa and male organs! 8.3–8.4 Basal plate and jaws of two specimens; 8.5 Mature conulus; 8.6 Twin conulus; 8.7 Fused conuli from the bursa. 8.3–8.7 to the same scale as Fig. 1.
TABLE 8.
Morphometric data for
Austrognatharia australis
.
| Mean |
SD |
Max |
Min |
n |
| Body length of adults |
1090.00 |
1 |
| Body width of adults |
80.00 |
1 |
| Body index of adults |
13.63 |
1 |
| Rostrum index of adults |
1.15 |
1 |
| Jaw length |
26.50 |
0.71 |
27 |
26 |
2 |
| Basal plate length |
7.00 |
0.00 |
7 |
7 |
2 |
| Basal plate width |
26.00 |
0.00 |
26 |
26 |
2 |
| Basal plate index |
0.27 |
0.00 |
0.27 |
0.27 |
2 |
| Sperm length |
22.00 |
1.00 |
23 |
21 |
3 |
| Sperm width |
6.33 |
1.15 |
7 |
5 |
3 |
| Sperm index |
3.54 |
0.57 |
4.20 |
3.14 |
3 |
FIGURE 9.
Austrognatharia australis
nov. spec.
9.1 Anterior; 9.2 Posterior body region; 9.3 Conuli in the testis; 9.4 Mature conulus. Phase contrast micrographs of live specimens.
Discussion
Jaws with only 1–2 teeth in the dorsal row, and a basal plate with flat to nonexisting rostral lobes characterize the genus
Austrognatharia
Sterrer, 1970
(emend. Sterrer, 1991). Of 10 species known in this genus, the following can be excluded from further comparison because of their greatly differing conuli dimensions and proportions:
A. sterreri
(Kirsteuer, 1969)
,
A. strunki
Farris, 1973
;
A. atraclava
Ehlers & Ehlers, 1973
;
A. homunculus
Sterrer, 1991
;
A. pecten
Sterrer, 1991
;
A. mooreensis
Sterrer, 1991
;
A. stirialis
Sterrer, 1998
; and
A. medusifera
Sterrer, 1998
. Of the remaining two species,
A. kirsteueri
Sterrer, 1970
has considerably shorter jaws (
21.7 µm
) and a smaller basal plate (
6.4 µm
by
20.1 µm
) as well as shorter (
18.25 µm
) and plumper conuli (index 2.36) than
A. australis
n. sp.
Conversely, these dimensions are much greater in
A. boadeni
Sterrer, 1971
(jaw length
30–31 µm
; basal plate
8–9 µm
long by
28–30 µm
wide), which has also longer (to
38 µm
) and more slender conuli (index 4.5) than
A. australis
n. sp.
Acknowledgments
I am grateful to my friends John and Marge Wells for their hospitality in
Wellington
, to Bev Dickson for making our stay at the Portobello Marine Laboratory so pleasant and productive, and to Susan K. Young for help with sample collecting. This paper has been prepared with support from NSF Grant No. DEB0118804.