Research Article |
Corresponding author: Hae-Lip Suh ( suhhl3464@gmail.com ) Academic editor: Christopher Glasby
© 2017 Man-Ki Jeong, Jin Hee Wi, Hae-Lip Suh.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Jeong M-K, Wi JH, Suh H-L (2017) A new species of Leiochrides from the Korean subtidal waters with notes on the taxonomic status of the genus Pseudomastus (Annelida, Capitellidae). ZooKeys 685: 91-103. https://doi.org/10.3897/zookeys.685.12700
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Leiochrides yokjidoensis sp. n., collected from the sublittoral muddy bottom in southern Korea, is described as a new species. The taxonomic status of the monospecific genus Pseudomastus has been a subject of controversy for many years, as its characteristics overlap those given in recent generic definitions of Leiochrides. The results of a comprehensive review and comparison regarding the two genera, based on previous records showed minor differences. In this study, a detailed description of L. yokjidoensis sp. n. is given and a comparison with closely related species is tabulated and discussed.The taxonomic status of Pseudomastus is discussed and the genus placed in synonymy with Leiochrides.
Korea, Leiochrides yokjidoensis sp. n., morphology, Polychaeta , Scolecida , Sedentaria
Polychaetes are an important component of the macrobenthic community and they play a crucial role in the functioning of benthic communities in the recycling and reworking of the benthic sediments, bioturbation, and in the burial of organic matter (
The genus Leiochrides was established by
The genus Pseudomastus established by Capaccioni-Azzati and Martin (
This study provides a detailed description of a new species of Leiochrides from southern Korea and reveals its morphological distinctiveness through comprehensive comparisons with closely related species. Additionally, the taxonomic status of the genus Pseudomastus is discussed.
Sediment samples were obtained from the sublittoral muddy-sand bottom of the southern coast of Korea with a 0.05 m2 Van Veen grab followed by elutriation on a 0.35 mm sieve in a 30 L seawater container. The remaining organisms on the sieve were transferred to a 1 L collecting jar with a 7% MgCl2 solution for anesthesia. The relaxed samples were initially fixed in a 10% formalin solution for an hour before they were preserved in 90% ethanol for subsequent analysis. For the identification of the morphological features, the samples were stained with Shirlastain A (SDLATLAS, Inc.) for three seconds and sorted under a zoom stereomicroscope (Nikon SMZ745T). Line drawings were conducted using a differential interference contrast microscope (Eclipse Ci-L, Nikon) and a digital pen display (Cintiq 22HD, Wacom). The MGSP of the examined specimens were described and photographed as described in
The type materials were deposited in the collections of the Marine Biodiversity Institute of Korea (MABIK) in Seocheon, Korea.
Pseudomastus Capaccioni-Azzati & Martin, 1992: 247–249, figs 1a–h, 2a–f. Syn. n.
Leiochrides australis Augener, 1914
Western Australia
(modified after
Holotype (complete specimen): MABIKNA00145754, sex uncertain, Yokjido, 34°31.1’N, 128°21.6’E (DDM), subtidal, sandy mud bottom, 53 m depth, April 2016, collector: Man-Ki Jeong. Paratypes (3 incomplete specimens): MABIKNA00145755–NA00145757, same information as holotype.
Thorax with achaetigerous peristomium and 12 chaetigers. First chaetiger without neuropodia. Chaetigers 1–11 with capillary chaetae only, chaetiger 12 with notopodial capillaries and neuropodial hooks. Abdominal chaetigers with hooded hooks only. Branchiae present on posterior abdominal segments as 2–4 digitate filaments near notopodia. Approximately ten preanal chaetigers without branchiae. Pygidium with four anal cirri.
One complete specimen and eight incomplete specimens. Largest specimen 27 mm long, 0.34 mm wide for 159 chaetigers. Smallest specimens 7 mm long, 0.25 mm wide for 34 chaetigers. Body thread-like, cylindrical, widest in anterior thoracic chaetigers, tapering from abdomen to pygidium. Color in alcohol yellowish or reddish brown.
Prostomium short, conical, wider than long, with blunt anterior end; presence of nuchal organs indistinct, eyespots not observed in preserved specimen (Figs
Thorax with 13 segments including single peristomium and 12 chaetigers (Fig.
Transition between thoracic and abdominal region distinguished by change in position and type of chaetae and length of segments; abdominal segments longer and slightly narrower than thoracic segments, gradually smaller posteriorly; notopodial hooded hooks first present on chaetiger 13 (first abdominal chaetiger) (Fig.
Abdominal parapodial lobes slightly developed, located in posterior half of segment, well separated from each other; parapodial lobe gradually reduced posteriorly (Fig.
Hooded hooks short, with main fang extending slightly beyond hoods; hood flared; shaft slightly enlarged like manubrium (Figs
Branchiae digitiform, cylindrical, retractile; abdominal chaetiger 120–150 each with 3–5 branchiae per fascicle emerging from notopodia which lack hooks in this region; eight preanal 8 segments without branchiae (Figs
Prostomium not stained. Peristomium and thoracic chaetigers 1–5 slightly stained in blue but rapidly fades. Chaetigers 6–9 stained blue, with narrow transverse blue speckled band near intra-segmental furrow (Fig.
The new species is named for its occurrence in Yokjido, Korea.
Leiochrides yokjidoensis sp. n. is distributed in the subtidal habitat (53 m) of the southern part of Korea.
Ecology. The surface sediment is mainly composed of sandy mud with fragmented shells. Mediomastus Hartman, 1944 and Notomastus M. Sars, 1851, also belonging to the Capitellidae, also occurred at the same location.
Leiochrides yokjidoensis sp. n. is distinct in the morphological combination of 12 thoracic chaetigers, chaetigers 1–11 with only capillary chaetae, and the last thoracic chaetiger with the notopodial capillaries and neuropodial hooks. Among the genera of Capitellidae the presence of 12 thoracic chaetigers and neurohooks in last thoracic chaetiger are shared with Leiochrides, Pseudomastus, and Scyphoproctus Gravier, 1904. However, Scyphoproctus is clearly separated from the new species by the presence of the unique anal plaque, acicular spines in the posterior abdomen, and two achaetous segments in the anterior part of the thorax. In this study, the new species was placed under the genus Leiochrides, because the generic diagnosis of Pseudomastus mostly agreed with that of Leiochrides (see details in discussion section). Leiochrides yokjidoensis sp. n. closely resembles L. hemipodus and P. deltaicus in the presence of the neurohooks in the thorax, the uniramous first chaetiger, the two distinct basal teeth above the main fang, and the presence of the branchiae in the posterior abdomen (Table
Leiochrides yokjidoensis sp. n. A anterior end, left lateral view B same, dorsal view C anterior end with proboscis (MABIKNA00145754), left lateral view D posterior end (MABIKNA00145754), left lateral view E–F hooded hooks from anterior abdominal notopodium. Abbreviations: ac, anal cirri; br, branchia; cc, capillary chaeta; hh, hooded hook; lo, lateral organ; mf, main fang; per, peristomium; pro, prostomium; prob, proboscis.
Leiochrides yokjidoensis sp. n. A−F scanning electron micrographs A anterior end in left lateral view B chaetigers 4–5 in left dorsolateral view C chaetigers 11–12 in left lateroventral view D chaetiger 15 in left lateral view E notopodial hooded hooks of chaetiger 16 F neuropodial hooded hooks of chaetiger 16 in frontal view G–H photomicrographs G thorax and anterior abdomen, right lateral view showing methyl green staining reaction H posterior end of body in left lateral view (MABIKNA00145754). Abbreviations: ac, anal cirri; br, branchia; cc, capillary chaeta; ch, chaetiger; hh, hooded hook; lo, lateral organ; mf, main fang; per, peristomium; pro, prostomium
Morphological comparison between L. yokjidoensis sp. n. and most related species. A: absent; P: present; C: capillary chaeta; H: hooded hook; L: length; W: width; Ch: chaetiger; incomp: incomplete specimen; no: notopodia; neu: neuropodia; NM: not mentioned.
Species | Overall size (L/W, mm) | Eyes | Thoracic chaetal arrangement | No. of chaetae per fascicle | Dental structure of hooks | Special character | No. of branchiae per fascicle | No. of anal cirri | Methyl green staining pattern | Locality | References | |
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Thorax | Abdomen | |||||||||||
L. hemipodus (Holotype) | 30–40/1–2 (incomp.) |
A | no: 12C neu: 11C+1H |
NM | NM | 2 rows (2/1) | 3–12 (sometimes bifurcated) |
NM | Ch 1–12 | San Pedro basin, California (887m) |
|
|
L. hemipodus (Paratype & its related sp.) | ?/1 | A | no: 12C neu: 10C+2H |
NM | NM | 2 rows (2/1) | Glands on chaetiger 6 | ca. ~15 (in fig. 4.9; branched) |
0 | Ch 1–12 | Santa Maria basin, California (603m) |
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L. yokjidoensis sp. n. | 27/0.34 | A | no: 12C neu: 11C+1H |
8–12(C) 8(H) |
no: 5–6(H) neu: 8–10(H) |
3 rows (2/3/3–5) |
3–5 (palmate) |
4 | Ch 6–11 | Korea (~43m) |
This study | |
P. deltaicus | 50/0.7 | P | no: 12C neu: 10C+2H |
13–20(C) 12(H) |
11–12(H) | 3 rows (2/1/4) | Distal spinules on notopodial capillaries | 2–4 | 3 | NM | Spain (~6m) |
Capaccioni-Azzati and Martin ( |
Capaccioni-Azzati and Martin (
This study provides the detailed morphological features of L. yokjidoensis sp. n. including the presence/absence of the lateral organ and genital pore, the number of chaetae per fascicle, MGSP, and the number of anal cirri.
1 | First chaetiger biramous; chaetigers 1–12 with capillary chaetae only | 2 |
– | First chaetiger uniramous | 4 |
2 | Prostomium deeply bifid; hooded hooks with small teeth above main fang in 3 rows | L. biceps |
– | Prostomium without dorsal furrow; hooded hooks with small teeth above main fang in 2 rows | 3 |
3 | Hooded hooks with 4–6 teeth above main fang | L. africanus |
– | Hooded hooks with 8–10 teeth above main fang | L. pallidior |
4 | Chaetigers 1–12 with capillary chaetae | 5 |
– | One or more transitional chaetigers with capillary notochaetae and neurohooks | 7 |
5 | First two abdominal segments with notopodial capillaries; pygidium with 4 anal cirri; branchiae present | L. norvegicus |
– | Abdominal segments without capillary chaetae | 6 |
6 | Hooded hooks with 5 teeth above main fang in 3 rows | L. andamanus |
– | Hooded hooks with 10–11 teeth above main fang in 3 rows | L. australis |
7 | Chaetiger 12 transitional with capillary notochaetae and neurohooks | 8 |
– | Chaetigers 11–12 transitional with capillary notochaetae and neurohooks | 9 |
8 | Hooded hooks with 8–10 teeth above main fang in 3 rows; posterior abdomen with 3–5 branchiae per fascicle; pygidium with 4 anal cirri | L. yokjidoensis sp. n. |
– | Hooded hooks with 3 teeth above main fang in 2 rows; posterior abdomen with 3–12 branchiae per fascicle; pygidium without anal cirri | L. hemipodus |
9 | Hooded hooks with 3 teeth above main fang in 2 rows | L. branchiatus |
– | Hooded hooks with 7 teeth above main fang in 3 rows; posterior abdomen with 2–4 branchiae per fascicle; pygidium with 3 anal cirri | P. deltaicus |
We would like to thank the editor and anonymous reviewers who made constructive and invaluable suggestions. This study was a part of the project titled ‘Long-term change of structure and function in marine ecosystems of Korea’, funded by the Ministry of Oceans and Fisheries, Korea. This work was supported by National Marine Biodiversity Institute Research Program (2017M01100).