A new Maldane species and a new Maldaninae genus and species (Maldanidae, Annelida) from coastal waters of China

Abstract Paramaldane, new genus, with type species Paramaldane glandicincta sp. n., and Maldane adunca sp. n. (Maldanidae, Polychaeta) are described based on material from the coast of south China. The new genus Paramaldane is similar to Maldane Grube, 1860 and Sabaco Kinberg, 1867, but it clearly differs from all genera within the subfamily Maldaninae by a unique combination of characters: the cephalic plate is almost circular with low, entire and smooth cephalic rim, nuchal grooves small and crescentic, lacking a collar on chaetiger 1, short companion notochaetae, a collar-like glandular band on the anterior part of the sixth chaetiger, and a well-developed anal valve. Paramaldane glandicincta sp. n. is characterised by having a glandular band on the anterior part of the sixth chaetiger, an almost circular cephalic plate, an entire and smooth cephalic rim, and small crescentic nuchal grooves. Maldane adunca sp. n. is characterised by a low cephalic rim, nuchal grooves with a strongly curved anterior part and isolated from the cephalic rim. Finally, a taxonomic key to genera of Maldaninae and a comparative table to species of Maldane are provided.


Introduction
The Maldanidae, also known as bamboo worms, is a tubicolous and common family found in hard or soft substrates from the intertidal region to the deep sea (Paterson et al. 2009;De Assis and Christoffersen 2011). Maldanid species have a long, cylindrical body, generally with one or both truncate ends; elongated median segments with prominent tori on the end of each chaetiger; a keel-shaped prostomium fused to the peristomium; and a pair of nuchal grooves located on each side of the prostomium (Fauchald 1977;Fauchald and Rouse 1997;De Assis and Christoffersen 2011). Arwidsson (1906) split Maldanidae into subfamilies after the major and complete revision of the family, leaving Maldane and Asychis in the nominotypical subfamily as the Maldaninae. The subfamily Maldaninae is recognised by the presence of cephalic and anal plates, and having the anus dorsal to the plate (Fauchald 1977). Light (1991) reviewed the Maldaninae and considered characters of cephalic and anal plates, the types of notochaetae, and the presence of a collar on chaetiger 1 as important generic characters. This author made a major revision of Maldaninae, and recognized six genera: Asychis Kinberg, Maldane Grube, Sabaco Kinberg, Bathyasychis Detinova, Chirimia Light and Metasychis Light. Posteriorly, De Assis and Christoffersen (2011) analyzed the phylogenetic relationships within Maldanidae based on morphological characters.
During a sorting of the Maldanine specimens deposited in the Marine Biological Museum, Chinese Academy of Sciences (MBM) in the Institute of Oceanology, Chinese Academy of Sciences, Qingdao (IOCAS), some specimens of Asychis-like species were identified, which belonged to an unknown species. Based on these specimens, two new species are fully described and illustrated and a new genus of Maldaninae is proposed. A taxonomic key to genera of Maldaninae and a table comparing the morphology of all species of Maldane are provided.

Material and methods
The specimens were collected from the South China Sea from 1959 to 1962. They have been stored in 70% ethanol. Specimens were examined under Zeiss Stemi 2000-C stereomicroscopes, and compound microscopes. Drawings were prepared with the aid of 'AxioCam MRc 5'digital camera fitting on the stereomicroscopes. Line drawings are completed in the Adobe Photoshop CS6 using a graphics tablet. Notochaetae and neurochaetae were extracted carefully and observed under optical and scanning electron microscopes (SEM). All specimens are deposited in the Marine Biological Museum, Chinese Academy of Sciences (MBM). An identification key to the genera of Maldaninae modified from Light (1991) is provided below. Table 1 compares morphological characters for all known species of genus Maldane.
Etymology. The generic name is a combination of the prefix para-(meaning resembing) and the generic name Maldane. The new genus is related to Maldane in morphology. Gender: feminine.
Remarks. The new genus Paramaldane is superficially similar to Maldane Grube, 1860 and Sabaco Kinberg, 1867. The anal plate and notochaetae type of Paramaldane are closer to Maldane. The shape of prostomial palpode and nuchal grooves are closer to Sabaco. However, the new genus can be easily distinguished by the characters of the cephalic plate, which are considered to be of generic importance (Light 1991;Green 1994). The cephalic rim of Maldane and Sabaco is divided into two lateral lobes and a posterior lobe by deep lateral notches, but that of the Paramaldane is almost smooth. The prostomial palpode of Maldane is spade-like, but that of Paramaldane is bluntly rounded and confluent with cephalic rim. Both Sabaco and Paramaldane have small crescentic nuchal grooves that are isolated from cephalic rim, but Sabaco has a complete collar on the first chaetiger that is lacking in Paramaldane. Notochaetae of Sabaco have long companion chaetae, but companion notochaetae of Paramaldane are short. An identification key to the genera of Maldaninae modified from Light (1991) is provided below. Diagnosis. Complete specimen with 19 chaetigers and two preanal achaetigerous segments. Cephalic plate rounded. Cephalic rim with two lateral creases, margin of the rim almost smooth. Anterior chaetigers biannulate. Sixth chaetiger with thick, collarlike glandular band. Rim of anal plate with deep lateral notches,ventral margin of anal rim crenulate, dorsal margin smooth.
Description. Holotype complete, 43 mm long, and 2.0 mm wide at the third chaetiger. Paratype of MBM 008130 complete, 74 mm long and 2.5 mm wide. Body cylindrical with 19 chaetigers, two preanal achaetigerous segments, and pygidium. First chaetiger without neurochaetae. Anterior part of the sixth chaetiger with thick glandular band forming a low collar and overlapping posterior part of the fifth chaetiger (Figs 1A, F; 2C-E).
First four chaetigers completely biannulate, each comprising an achaetigerous and chaetigerous annulus. First six chaetigers short, following chaetigers elongated. Epidermal glands developed well on chaetigers 1-6. Glands only present on parapodial tori of following segments.Thick glandular band resembling a collar located on anterior part of sixth chaetiger, covering rear of fifth chaetiger, divided into dorsal and ventral parts by two lateral slits (Figs 1F, 2C). Dorsal margin of glandular band smooth (Fig. 2E). A small notch on ventral median line of ventral glandular band (Figs 1A, 2D).
Etymology. The specific name glandicincta is a combination of glans and cinctus (meaning "belt", feminine form cincta), refering to the characteristic glandular belt on the six chaetiger.
Remarks. Paramaldane glandicincta sp. n. is characterised by a collar-like glandular band on the anterior margin of the sixth chaetiger. Description. Holotype about 65 mm in length, 1.5 mm in width. Largest specimen more than 70 mm in length, and 3.0 mm in width. Segments short on anterior and posterior body, longer on middle body (Figs 3A, 4D).
Two short and rudimentary preanal achaetigerous segments (Figs 3I, 4C), which deeply stained with methyl green. Anal pore with a less-developed anal valve (Fig. 3I). Anal mound well developed. Anal plate truncated, nearly rounded; median part of plate with a shallow furrow dorso-ventrally extended (Fig. 3C). Rim of anal plate low and incised laterally (Fig.  3C, I). Dorsal part of rim smooth. Ventral part of the rim smooth to weakly serrated.
Variation. Body wall of small individuals thin but thick in large ones. Body of small individuals smooth, semitransparent and lacking epidermal glands. Large individuals with glandular pads on parapodial tori and ventral side of chaetigers 3-5. Etymology. The specific epithet is the Latin adjective adunca (feminine, meaning hooked) and refers to the strongly curved nuchal grooves.
Remarks. Maldane adunca sp. n. is distinctive in the genus Maldane with its low cephalic rim and hook-like nuchal grooves. Maldane adunca sp. n. is close to Maldane sarsi Malmgren, 1865, a potential species-complex, which is thought to be a cosmopolitan species (Day 1967, Hartman 1961. However, the new species differs from the latter by possessing a low cephalic rim, strongly curved nuchal grooves which are isolated from the cephalic rim, and lacking crescentic glandular bands on the dorsal surface of the fifth chaetiger. In M. sarsi, the cephalic rim is well developed, its posterior part forms a deep pocket-like structure (Arwidsson 1906) and overlaps the posterior part of cephalic keel, cephalic keel is strongly arched, the nuchal grooves are narrow and slightly curved and connected with margin of cephalic rim, and the dorsal surface of the fifth chaetiger sometimes bears a crescentic glandular band (Green 1991, Fauvel 1953. Maldane adunca sp. n. is also closely related to Maldane glebifex Grube, 1860. The new species differs from the latter in the form of the anal rim and nuchal grooves. Maldane glebifex has a crenulated border to the anal plate while M. adunca sp. n. has a smooth to slightly crenulated anal rim. The nuchal grooves of M. adunca sp. n. are much more curved than that of M. glebifex. In terms of geographical distribution, M. glebifex is a Mediterranean/ North Atlantic species (Fauvel 1927), and it is unlikely to occur in the South China Sea. Light (1991) revised the subfamily Maldaninae and recognized 16 species of Maldane, of which Maldane pellucida Sars, 1869 was recognized later as nomina nuda (Oug et al. 2014 Arwidsson, 1911 andM. sarsi borealis Imajima, 1963 but their validity is doubtful. Maldane sarsi antarctica resembles the stem species. Color and gland pattern is main difference between the subspecies and its stem species according to Arwidsson (1911), but they are not robust taxonomic characters. Imajima (1963) collected only one specimen to erect M. sarsi borealis. This subspecies has 18 chaetigers, and anal plate of it incised ventrally. The chaetiger number is unusual in Maldane (usually, 19 chaetigers in Maldane species).