Syllidae (Annelida: Polychaeta) from Indonesia collected by the Siboga (1899 – 1900) and Snellius II (1984) expeditions
Author
Aguado, Teresa
Author
Martín, Guillermo San
Author
Ten, Harry A.
text
Zootaxa
2008
1673
1
48
journal article
50187
10.5281/zenodo.180233
7bf44e29-23f0-4bfc-b0f7-549bc7d3b187
1175-5326
180233
Opisthosyllis flaccida
(
Grube, 1878
)
n. comb.
Fig. 6
Syllis flaccida
Grube, 1878
: 118
–119 + p. 112, Pl. 7, fig. 6.
Typosyllis flaccida
.—
Licher, 1999
: 246
, 247, fig. 103.
Material examined.
3
Syntypes
MPW 394, 2
Syntypes
ZMB
Q 4395,
Philippines
, Camiguin, Aibuhit. 2 spec.
ZMA
V.Pol. 1985.04 (as
Syllis exilis
),
Indonesia
, Lesser Sunda Isl., Bay of Bima, near south fort, trawl, dredge, muddy bottom with coral sand,
55 m
, Siboga Expedition, Sta. 47, 8/
12 April 1899
.
Comparative material examined.
Opisthosyllis leslieharrisae
Aguado, San Martín & Nygren, 2005
.
Type
material
MNCN
16.01/10264-66,
USA
, California, Santa Catalina Island, Wrighley Marine Science Centre,
1–4 m
,
33°26.7’N
118°29.1’W
.
Description.
Largest
syntype
37 mm
long,
1.5 mm
wide, with 121 segments. Specimens from
Indonesia
27 mm
long,
1.2 mm
wide with 82 segments;
32 mm
,
1.3 mm
, 77 segments, respectively. Body broad and flaccid. Segments slightly annulated secondarily, with about four to five rings. Dorsal surface covered by small irregularly distributed dark inclusions (
Fig. 6
A). Prostomium wider than long, rectangular to oval, with two pairs of dark eyes in trapezoidal arrangement, anterior pair larger than posterior, eye spots absent. Palps broad, fused at base, with central groove, similar in length to prostomium, ventrally folded. Antennae, tentacular and dorsal cirri distinctly thick. Median antenna with 20 articles. Lateral antennae inserted on anterior margin of prostomium, slightly shorter than median antenna, with 16 articles. Triangular occipital flap partially covering posterior part of prostomium. Peristomium shorter than subsequent segments (
Fig. 6
A). Dorsal tentacular cirri with 32–35 articles, ventral pair shorter, with 20 articles. Anterior dorsal cirri with 21–24 articles, midbody and posterior dorsal cirri with 25 articles. Ventral cirri digitiform, inserted proximally, reaching tip of parapodia (
Fig. 6
H). Prechaetal and postchaetal lobes similar in length, on all parapodia. Seven heterogomph compound chaetae on anterior chaetigers, nine to ten on median and five to seven on posteriorly-most parapodia. Compound chaetae of anterior and midbody parapodia with slightly bidentate blades, proximal tooth small. Blade edge with short spines; distal part of shafts provided with minute spines (
Figs 6
B, C). Length of dorsal-most chaetal blades on anterior parapodia and midbody parapodia ca. 30 µm. Posterior compound blades unidentate, ca. 26 µm long, with short spines; shafts distally curved (
Fig. 6
D). Dorsal and ventral simple chaetae not seen. Four straight aciculae in anterior parapodia, three in median and two in posterior, all straight or slightly oblique (
Figs 6
E, F). Pygidium conical (
Fig. 6
G), two anal cirri with about 30 articles. Pharynx through eight segments, similar in length but somewhat narrower than proventricle, tooth long and slender, dagger-shaped, located on midline of pharynx. Proventricle through segment 9 to 14, rectangular to oval, with about 30 rows of muscular cells (
Fig. 6
A). Both specimens from
Indonesia
developing female stolons (oocytes accumulated in last 22, and 30 segments, respectively).
Remarks.
The description above is based on the Indonesian material; the
syntypes
are longer and exhibit some variations in number of articles of antennae and dorsal cirri (median antenna 26–30 articles, lateral ones 18–22, tentacular cirri 40–45, dorsal cirri of anterior segments 25–35, midbody cirri 30–40 and posterior ones 25–28). A pharyngeal tooth located posteriorly in the pharynx is the principal diagnostic character for
Opisthosyllis
and is visible, after dissection, in both the
types
and Indonesian material. The shape of the compound chaetae and presence of an occipital flap in
O. flaccida
are also other diagnostic characters of
Opisthosyllis
. Other species with a tooth in the middle of the pharynx are
Opisthosyllis laevis
Day, 1957
,
O. longidentata
San Martín, 1991
and
O. leslieharrisae
. In contrast to
O
.
flaccida
,
O. laevis
have bidentate falcigers;
O. longidentata
has thin dorsal cirri becoming pseudoarticulated in the posterior part of the body and bidentate blades with long spines and, finally,
O. leslieharrisae
has papillae over the dorsum and bidentate blades with long spines (
Day, 1957
; San Martín, 1991;
Aguado
et al.
, 2005
).
FIGURE 6.
Opisthosyllis flaccida
n. comb.
ZMA V. Pol. 1985.04. A: Anterior part dorsal view; B: Anterior chaetae; C: Midbody chaetae; D: Posterior chaetae; E: Anterior aciculae; F: Midbody aciculae; G: Posterior part, dorsal view; H: Parapodium, anterior view. Scale A: 0.5 cm; B–F: 30 µm; G: 1.4 cm; H: 1 mm.
Distribution.
Philippines
,
Indonesia
.