A new species of Linopherus (Annelida, Amphinomidae) from Beibu Gulf, South China Sea

Abstract

Linopherus beibuwanensis sp. n. is described based on six specimens deposited in the Marine Biological Museum of the Chinese Academy of Sciences, Qingdao, collected from the Beibu Gulf (Tokin Gulf), South China Sea. The new species differs from all other Linopherus species by the shape of prostomium and caruncle. The posterior margin of prostomium is bilobed; the caruncle arises medially and confluently from the posterior margin of the prostomium, joining together with prostomium. A key to distinguish the known species of the genus is provided.

Full text

A new species of Linopherus (Annelida, Amphinomidae) from Beibu Gulf, South China Sea 37
A new species of Linopherus (Annelida, Amphinomidae)
from Beibu Gulf, South China Sea
Yue Sun1,2,3, Xinzheng Li1,3
1 Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, China 2 University
of Chinese Academy of Sciences, Beijing 100049, China 3 Laboratory for Marine Biology and Biotechnology,
Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong, 266070, China
Corresponding author: Xinzheng Li (lixzh@qdio.ac.cn)
Academic editor: C. Glasby|Received 20 June 2016|Accepted 29 November 2016|Published 13 December 2016
http://zoobank.org/F64A8C0C-BDE3-4537-9460-FBB21DC7009F
Citation: Sun Y, Li X (2016) A new species of Linopherus (Annelida, Amphinomidae) from Beibu Gulf, South China
Sea. ZooKeys 640: 37–43. https://doi.org/10.3897/zookeys.640.9619
Abstract
Linopherus beibuwanensis sp. n. is described based on six specimens deposited in the Marine Biological
Museum of the Chinese Academy of Sciences, Qingdao, collected from the Beibu Gulf (Tokin Gulf),
South China Sea. e new species diers from all other Linopherus species by the shape of prostomium
and caruncle. e posterior margin of prostomium is bilobed; the caruncle arises medially and conuently
from the posterior margin of the prostomium, joining together with prostomium. A key to distinguish the
known species of the genus is provided.
Keywords
Fireworm, new species, polychaete, Pseudeurythoe, systematics, taxonomy
Introduction
Polychaetes belonging to the family Amphinomidae are commonly known as re-
worms due to the burning sensation caused by the calcareous harpoon notochaetae
(Fauchald, 1977). e amphinomids are globally distributed and common in shal-
low tropical and subtropical waters (Kudenov 1995): Linopherus abyssalis (Fauchald,
1972a), Linopherus hemuli (Fauchald, 1972b), and Chloeia kudenovi Barroso & Paiva,
ZooKeys 640: 37–43 (2016)
doi: 10.3897/zookeys.640.9619
http://zookeys.pensoft.net
Copyright Yue Sun, Xinzheng Li. 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.
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Yue Sun & Xinzheng Li / ZooKeys 640: 37–43 (2016)
38
2011 are examples of recently reported species from abyssal depths and polar areas
(Barroso 2011; Fauchald 1972a, b).
Species of the genus Linopherus Quatrefages, 1865 have been referred as members
of Pseudeurythoe Fauvel, 1932. Fauchald (1972a) described a new species from abyssal
depths and reviewed the species of Pseudeurythoe. In 1977, he treated Pseudeurythoe
as a synonym of Linopherus. Since then Linopherus has been accepted by subsequent
authors and in the present work (San Martín 1986; Salazar-Vallejo 1987). Linopherus
diers remarkably from the other genera of the family in having species without carun-
cle or with a reduced caruncle, and branchiae that are limited to the anterior part of the
body. e morphology of the prostomium, the development of prostomial appendages,
caruncle, parapodia, and the number of branchiae are important in species identica-
tion (Kudenov 1995). To date, six species of Linopherus have been reported from the
coastal waters of China (Sun, Lei and Zhou 2008): Linopherus ambigua (Monro, 1933),
L. paucibranchiata Fauvel, 1932, L. hirsuta (Wesenderg-Lund, 1949), L. oligobranchia
(Wu, Shen & Chen, 1975), L. microcephala (Fauvel, 1932), and L. spiralis (Wesenderg-
Lund, 1949).
When the authors examined the Amphinomidae archived in the Marine Biologi-
cal Museum of Chinese Academy of Sciences (MBMCAS), Institute of Oceanology,
Chinese Academy of Sciences (IOCAS), six specimens of Linopherus were separated
out. Careful examination revealed that these specimens represented a new species. e
new species is described here, and a key to worldwide species of Linopherus is provided.
Material and methods
e specimens were collected during the late 1950s to early 1960s from Beibu Gulf
(Tonkin Gulf ), northern South China Sea. All specimens are deposited in the MBMCAS,
preserved in 75% ethanol solution. Microscopy observations and drawings were made
using a Zeiss Stemi 2000-C stereomicroscope equipped with an AxioCam MRc 5 digital
camera.
Systematics
Family Amphinomidae Lamarck, 1818
Genus Linopherus Quatrefages, 1865
Linopherus beibuwanensis sp. n.
http://zoobank.org/83C424FA-951B-4F12-8CEC-B6CD6088AD20
Fig.1
Material examined. Holotype, MBM010010, Beibu Gulf, 21°15'N, 108°06'E,
91m, sandy mud, coll. Xiutong Ma, 11 Feb 1959. Paratypes, MBM200142, Beibu

A new species of Linopherus (Annelida, Amphinomidae) from Beibu Gulf, South China Sea 39
Figure 1. Linopherus beibuwanensis sp. n. A Anterior end in dorsal view B Anterior end in vental view
Cleft parapodia of chaetiger 14 in frontal view D branchiae of chaetiger 28 E harpoon notochaeta Fforked
neurochaeta G slender capillary chaeta. Scale bars: A–B, 200μm; C–D, 250 μm; E–F, 50 μm; G, 20 μm.
Gulf, 18°30'N, 107°00'E, 66m, sandy beach, coll. Zhengang Fan, 10 Sep 1960;
MBM200143, Beibu Gulf, 18°00'N, 107°45'E, 90m, silty mud, coll. Ruiping Sun, 9
Apr1962; MBM200144, Beibu Gulf, 18°00'N, 108°00'E, 93m, sandy mud, coll. Xiu-
tong Ma, 11 Dec 1959; MBM200145, Beibu Gulf, 18°30'N, 107°00'E, 66m, sandy
beach, coll. Xiutong Ma, 9 Dec 1962; MBM200122, Beibu Gulf, 18°00'N, 107°00'E,
sandy mud, coll. Zhengang Fan, 14 Feb1960.
Diagnosis. Prostomium globular, posterior margin bilobed, with two pairs of eyes,
anterior pair semicircular in shape. Medial caruncle conspicuous, arising from and con-
uent with posterior prostomial margin, medial lobe projecting above paired lateral
lobes. Parapodia biramous, rami widely separated, with single dorsal and single ventral
cirrus. Branchiae dendritic, present from chaetiger 3 onwards, with more than 40 pairs.

Yue Sun & Xinzheng Li / ZooKeys 640: 37–43 (2016)
40
Description. Holotype (MBM010010) incomplete, lacking posterior part, 17
mm long, 2 mm wide excluding chaeta, with 45 chaetigers. Body elongate, nearly
rectangular in cross section, tapering posteriorly. Color in alcohol pale yellow, without
color pattern.
Prostomium (Fig. 1A) divided into two parts by transverse groove. Anterior lobe
rounded, with pair of cirriform antennae dorsally and similar pair of palps laterally,
palps with three distinct articulations. Posterior lobe heart-shaped, bilobed along pos-
terior margin, with median antenna and two pairs of reddish eyes. Anterior pair of eye
spots semicircular in shape and large, posterior pair of eye spots rounded and small.
Median antenna conical, slightly shorter than paired antennae, located at posterior
margin of prostomium. Buccal opening occupying two chaetigers (Fig. 1B).
Caruncle rectangular and conspicuous, medial lobe projecting above paired lateral
lobes. Caruncle restrict to chaetiger 1, equal in length to posterior prostomial lobe of
prostomium, reaching to anterior margin of chaetiger 2, arising medially and conu-
ently with posterior prostomium (Fig. 1A).
All parapodia biramous, with chaetiger 1 greatly reduced, chaetiger 2 formingrst
dorsally complete ring. Parapodia with slender cirri (Fig. 1A, C), both notopodia and
neuropodia well-developed, chaetal sac forming low rounded lobe. First two parapodia
with longer and more conspicuous cirri than other parapodia; ventral cirri of chaetiger
2 longest, each with four articulations (Fig. 1A). Succeeding parapodia with tapering
and rather short ventral cirri.
Branchiae present from chaetiger 3, located on posterior face of each notopodia
(Fig. 1A), arising as tufts, dendritically branched, decreasing along body and disap-
pearing at approximately chaetiger 42; chaetiger 1 branchiae with ve terminal la-
ments, chaetiger 17 branchiae with 29 or 26 terminal laments, chaetiger 28 branchiae
with 15 laments (Fig. 1D), chaetiger 42 branchiae with 6 or 7 laments.
Notochaetae of three types: stout harpoon chaetae, numbering 13–24 per fascicle
(Fig. 1E); slender capillary chaetae (Fig. 1G), faintly serrated, without basal spur, many
broken; notoacicula, numbering 3–4 per fascicle, hastate (Fig. 1C). Neurochaetae of
three kinds: forked chaetae, short limb reduced as spur, with thin shafts and long,
distally serrated cutting margins (Fig. 1F); slender, capillary chaetae, smooth; neuroac-
icula, numbering 2–3 per fascicle, slightly hastate, slender than notoacicula (Fig. 1C).
Variations. All specimens examined are incomplete lacking the posterior part.
Specimen size varies from 1.9 to 2.5 mm in maximum width. Branchial chaetiger
range varies from 3 to 31–40. e maximum number of branchial laments varies
from 20–29. One female paratype (MBM200143) with eggs in posterior coelomic
cavity, ranging in diameter from 71μm to 90 μm.
Etymology. e species is named after Beibuwan, the Chinese name for the Beibu
Gulf (Tonkin Gulf), South China Sea.
Distribution. Only known from Beibu Gulf, South China Sea.
Remarks. Linopherus beibuwanensis sp. n. is referred to Linopherus because of
the arrangement of branchiae and the reduced but characteristic caruncle. Linopherus
beibuwanensis sp. n. is unique in this genus for the combined shape of its prostomium

A new species of Linopherus (Annelida, Amphinomidae) from Beibu Gulf, South China Sea 41
and the caruncle. While the posterior prostomial margin is straight (not bilobed) in
most Linopherus species, their caruncles are also either absent or reduced. In the lat-
ter case, species with reduced caruncles typically exhibit a transverse groove that ap-
pears to isolate the caruncle from the prostomium, which is usually partly or com-
pletely concealed by the second chaetiger (see Langerhans 1881; Fauvel 1932; Monro
1933, 1937; Treadwell 1941; Wesenberg-Lund 1949; Knox 1960; Fauchald 1972a, b;
Kudenov 1975; Wu et al. 1975; Kudenov and Blake 1985; San Martín 1986; Salazar-
Vallejo 1987).
Linopherus beibuwanensis sp. n. is similar to L. abyssalis in having the posterior
prostomial margin bilobed. e new species can be distinguished from the latter by the
presence of eyes and arrangement of branchiae; the former has two pairs of eyes and
more than 40 pairs of branchiae, while the latter has no externally detectable eyes and
only 5-6 pairs of branchiae.
Caruncle morphology appears to be an essential character which can be used to dis-
tinguish the species of Linopherus. However, Linopherus species are small in size, and so
their caruncle morphology is imperfectly known since it is usually concealed by constric-
tion of the anterior chaetigers. Clearly, further research on this taxon is necessary.
Key to species of Linopherus (modied from Fauchald 1972 and Salazar-Vallejo
1987).
1 Branchiae present from chaetiger 2 continuing to end of body .....................
......................................................... L. reducta (Kudenov & Blake, 1985)
– Branchiae present from chaetiger 3 or 4 ...................................................... 2
2 Branchiae present from chaetiger 3 ............................................................. 3
– Branchiae present from chaetiger 4 ........................................................... 15
3 Eyes absent .................................................................................................4
– Eyes present, one or two pairs ..................................................................... 5
4 Several pairs of branchiae until end of body .....L. tripunctata (Kudenov, 1975)
– Only six pairs of branchiae .....L. oligobranchia (Wu, Shen & Chen, 1975)
5 First pair of eyes semicircular ...................................................................... 6
– First pair of eyes rounded ............................................................................8
6 Posterior margin of prostomium bilobed, more than 40 pairs of branchiae ...
............................................................................... L. beibuwanensis sp. n.
– Posterior margin of prostomium not bilobed, less than 40 pairs of branchiae ... 7
7 Six pairs of branchiae, caruncle absent ........ L. fauchaldi San Martín, 1986
– About 23 pairs of branchiae, caruncle present, small and rounded ................
.................................................................. L. microcephala (Fauvel, 1932)
8 Anterior lobe of prostomium conical, not expanded anteriorly .....................
............................................................... L. kristiani Salazar-Vallejo, 1987
– Anterior lobe of prostomium rounded, anteriorly expanded .......................9
9 One pair eyes ............................................................................................ 10

Yue Sun & Xinzheng Li / ZooKeys 640: 37–43 (2016)
42
– Two pairs of eyes ......................................................................................11
10 Caruncle present, cirri of second chaetiger longer than others .......................
................................................................ L. paucibranchia (Fauvel, 1932)
– Caruncle absent, cirri of second chaetiger as long as others ...........................
...........................................................L. hirsuta (Wesenberg-Lund, 1949)
11 More than 20 pairs of branchiae present ................................................... 12
– Maximally 16 pairs of branchiae present ................................................... 14
12 Branchiae present only on anterior chaetigers, eyes indistinct .......................
......................................................................... L. ambigua (Monro, 1933)
– Branchiae present in all but rst two and last few chaetigers, eyes distinct ... 13
13 Caruncle absent, eyes inconspicuous ...L. spiralis (Wesenberg-Lund, 1949)
– Caruncle present, eyes conspicuous ................ L. oculata (Treadwell, 1941)
14 13-16 pairs of branchiae present, caruncle present ........................................
.................................................. L. annulata (Hartmann-Schröder, 1965)
– Maximally seven pairs of branchiae present, caruncle absent .........................
................................................................ L. canariensis Langerhans, 1881
15 More than 40 pairs of branchiae present, eyes distinct, caruncle absent ........
..................................................................L. acarunculata (Monro, 1937)
– Less than 10 pairs of branchiae, eyes absent, caruncle present ...................16
16 Seven pairs of branchiae present, subdistally inated (hastate) acicular chae-
tae absent ...............................................................L. minuta (Knox, 1960)
– Less than 7 pairs of branchiae present, subdistally inated (hastate) acicular
chaetae present .......................................................................................... 17
17 Five or six pairs of branchiae present, dorsal cirri absent in branchial chaeti-
gers, caruncle in deep pocket at posterior margin of prostomium, small and
rounded .........................................................L. abyssalis (Fauchald, 1972)
– Five pairs of branchiae present, dorsal cirri absent in branchial chaetigers,
caruncle button-shaped .................................. L. hemuli (Fauchald, 1972b)
Acknowledgments
We appreciate the assistance of Dr. Sergio I. Salazar -Vallejo (EI Colegio de la Frontera
Sur, Chetumal, Mexico) and Dr. Beatriz Yáñez-Rivera (Ciencias del Mar y Limnología,
Universidad Nacional Autónoma de México, Unidad Académica Mazatlán, Mexico) for
their kind help with our taxonomic research and for providing us with important refer-
ences. We are grateful to Dr. Paulo Paiva and Dr. Jerry D. Kudenov for their comments
and suggestions improving the manuscript. We are also grateful to the managers of the
MBMCAS for their assistance in sorting the specimens. is study was supported by
the funds of the Ocean Public Welfare Scientic Research Project (No. 201505004-1),
the National Natural Science Foundation of China (No. 41406157), and the Strategic
Priority Research Program of the Chinese Academy of Sciences (XDA11020303).

A new species of Linopherus (Annelida, Amphinomidae) from Beibu Gulf, South China Sea 43
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