Diplecogaster tonstricula, a new species of cleaning clingfish (Teleostei: Gobiesocidae) from the Canary Islands and Senegal, eastern Atlantic Ocean, with a review of the Diplecogaster-ctenocrypta species-group

ABSTRACT The Diplecogaster-ctenocrypta species-group is reviewed; it comprises two species. The clingfish Diplecogaster ctenocrypta from the Canary Islands is redescribed. The new species Diplecogaster tonstricula, a facultative cleaner of other teleosts, is described on the basis of eight specimens and colour photos from Senegal and the Canary Islands, eastern Atlantic Ocean. The species is small, apparently not exceeding 23 mm total length; it is characterised by having nine dorsal-fin rays, eight anal-fin rays, 24–25 pectoral-fin rays, 14–15 principal caudal-fin rays, 13–16 rakers on third gill arch, pelvic disc without lateral papillae in region A, disc region B with two rows of weak papillae, interorbital distance 4.1–4.6 in head length, distance between disc and anus 14–17% of SL, head and body with 10–13 narrow vertical brownish bars, cheek with a white ocellus surrounded by black, and with a small black spot in the middle. The new species is compared with other species of the genus; a key to the six known species of the eastern Atlantic, Mediterranean and Black Sea and South African genus Diplecogaster is presented. A checklist is provided for the species of Diplecogaster and their synonyms.


Introduction
The clingfishes of the family Gobiesocidae are distributed worldwide in tropical and temperate seas, some also living in freshwater streams of the tropics. They occur on hard substrata, usually on rocky bottoms or in coral reefs, mostly in shallow waters. Clingfishes are characterised by possessing an adhesive disc formed by the pelvic fins, the head depressed, the skin naked, one dorsal and anal fin each, and several specialised osteological characters. The family was revised by Briggs (1955), who distinguished nine species from the eastern Atlantic and the Mediterranean (Table 1).

Black Sea
South Africa Canary Is., Madeira, Azores Briggs (1957) described two additional species of clingfishes from West Africa, and Smith (1964) described Apletodon knysnaensis from South Africa, which was later found to be a junior synonym of Apletodon pellegrini. Blache et al. (1970) distinguished two species of clingfishes from tropical West Africa (Table 1). Briggs (1986) found that Lepadogaster microcephalus Brook, 1890 is a junior synonym of Apletodon dentatus (Facciolà 1887); he distinguished eight nominal species of clingfishes from the north-eastern Atlantic and Mediterranean, some having several subspecies. Briggs (1990) recorded eight species of clingfishes from the eastern tropical Atlantic. Hofrichter and Patzner (1997) described Apletodon incognitus from the north-western Mediterranean Sea and the Azores. Vakily et al. (2002) listed five clingfish species from north-western Africa. Henriques et al. (2002) synonymised Lepadogaster zebrinus with L. lepadogaster and recognised L. purpurea as a valid species, based on their revisional study of this species group. Lepadogaster candolii was recently reclassified as Mirbelia candolii by Almada et al. (2008Almada et al. ( , p. 1155 Mirbelia candollei) (see Table 1). Fricke (2007) Briggs (1955) described Diplecogaster ctenocrypta, D. megalops and D. bimaculata pectoralis, distinguishing a total of four species-group taxa in the genus. Murgoci (1964, p. 229) added another subspecies, Diplecogaster bimaculata euxinica from the Black Sea. In a revisionary study of eastern Atlantic and Mediterranean gobiesocids, Hofrichter (1995) treated all these taxa as valid, comprising three valid species of Diplecogaster, or five valid taxa in the species group (including subspecies). Brito et al. (2002, p. 281, figures 364-366) reported Diplecogaster ctenocrypta (non Briggs 1955) from the Canary Islands, and illustrated a striped species that is a facultative cleaner of other teleosts. When additional specimens from the Canary Islands and specimens from Senegal became available, a comparison with the holotype of the deep-water species D. ctenocrypta revealed that the shallow water cleaning Diplecogaster belonged to a separate, undescribed species, which is described in the present paper. The Diplecogaster-ctenocrypta species-group is reviewed, and Diplecogaster ctenocrypta is redescribed.

Methods and materials
Methods follow Briggs (1955) and Hofrichter and Patzner (1997). The abbreviation SL refers to the standard length (measured from the tip of the snout to the middle of the caudal fin base), and TL to the total length (measured from the tip of the snout to the end of the caudal fin). The adhesive disc is divided into three different areas: region A is the anterior portion, region B the posterior portion, and region C the centre of the disc (as illustrated by Briggs 1955). In the description, data of the holotype are given first, followed by data of the paratypes in parentheses. Fin rays are counted using the method of Fricke (1983), where spines are expressed as Roman numerals, unbranched soft rays are expressed as lower case Roman numerals and branched rays as Arabic numerals. Subspecies classification is no longer used, following the method of Fricke et al. (2007); valid taxa of the species group formerly treated as subspecies are raised to species level. Specimens cited in the present paper are deposited in the following collections: CCML (

Diagnosis
Three and one half gills; gill membranes attached to the isthmus; disc double; dorsal and anal fins normal with strong rays; disc length 3.2-5.2 in SL; no spine in subopercular area; 4-9 dorsal-fin rays; 3-8 anal-fin rays; 20-26 pectoral-fin rays; premaxillaries short; maxillaries well forward in position; head lateral-line system with two pores in the lacrymal canal.

Remarks
A total of six valid species is known in this genus; a checklist of the species and an identification key are presented below. Within the genus Diplecogaster, two species groups can be distinguished: -Diplecogaster-bimaculata group: characterised by a moderate number of 4-8 rays in the dorsal fin and 3-7 in the anal fin (D.-ctenocrypta group: 9 rays in the dorsal fin, 8 rays in the anal fin), and the position of the anus which is situated in the middle between disc and anal-fin origin (D.-ctenocrypta group: situated closer to the analfin origin than to the end of the disc).

Diplecogaster-ctenocrypta species-group
Diagnosis Dorsal fin with 9 rays; anal fin with 8 rays; anus situated closer to the anal-fin origin than to the end of the disc.

Remarks
The distribution of the two species of this group is restricted to the eastern Atlantic Ocean (Canary Islands; Senegal).

Diagnosis
A species of Diplecogaster with 9 dorsal-fin rays, 8 anal-fin rays, 24-25 pectoral-fin rays, and 14-15 principal caudal-fin rays; 13-16 rakers on third gill arch; pelvic disc without lateral papillae in region A; disc region B with 2 rows of weak papillae; principal caudal-fin rays 14-15; interorbital distance 4.1-4.6 in head length; distance between disc and anus 14-17% of SL; head and body with 10-13 narrow vertical brownish bars; cheek with a white ocellus surrounded by black, and with a small black spot in the middle.

Description
Dorsal-fin ix; anal-fin viii; pectoral-fin xxiv-xxv; caudal-fin xiv-xv. Gill rakers on 3rd arch 13-16, very small, pointed. Teeth small, conical, slightly recurved, in patches towards the front of each jaw, narrowing to a line of single teeth laterally. Head lateral line system with 3 pores in nasal canal, 3 pores in postorbital canal, and 2 pores in lacrymal canal ( Figure 3); no mandibular pores.

Colour of preserved material
Head and body yellowish white, with 10-13 narrow vertical brownish bars (Figure 1). Nape with small white spots. Cheek with a white ocellus surrounded by black, and with a small black spot in the middle. Fins translucent.

Etymology
Tonstricula (Latin) means little female barber. The name refers to the cleaning behaviour of the new species.

Comparison
The Diplecogaster-ctenocrypta group, comprising the species D. ctenocrypta and D. tonstricula n. sp., is characterised by a high number of 9 rays in the dorsal fin and 8 in the anal fin (other species of the genus: 4-8 rays in the dorsal fin, 3-7 rays in the anal fin), and the position of the anus which is situated closer to the anal-fin origin than to the end of the disc (other species of the genus: situated in the middle between disc and anal-fin origin). Species of the group are further distinguished from D. bimaculata, D. euxinica and D. pectoralis in having 14-15 caudal-fin rays (18-21 in D. bimaculata, D. euxinica and D. pectoralis), and lacking lateral papillae in disc region A (many lateral papillae present in D. bimaculata, D. euxinica and D. pectoralis), and from D. megalops in 13-16 rakers on third gill arch (7-9 rakers in D. megalops). Diplecogaster tonstricula n. sp. differs from D. ctenocrypta by having the pelvic disc without lateral papillae in region A (lateral papillae present in D. ctenocrypta), disc region B with 2 rows of papillae (5 rows in D. ctenocrypta), lacking mandibular pores (one mandibula pore present in D. ctenocrypta), principal caudal-fin rays 14-15 (16 rays in D. ctenocrypta), the interorbital distance 4.1-4.6 in head length (5.4 in head length in D. ctenocrypta), the distance between disc and anus 14-17% of SL (19% of SL in D. ctenocrypta), and 13-16 rakers on third gill arch (18 in D. ctenocrypta). The live colour pattern of D. ctenocrypta is unknown, but the holotype is pale, without traces of bands, while the head and body of Diplecogaster tonstricula n. sp. is covered with 10-13 bars.
The species of Diplecogaster may be distinguished with an identification key (see above). Counts and proportions of the species of the genus are compared in Table 1.

Distribution and habitat
Eastern Atlantic Ocean: Canary Islands (El Hierro, Tenerife, Fuerteventura), Senegal (Dakar). Probably more widespread in the region. The species was collected and observed at 10-38 m depth, mainly on hard substrate. It was observed to act as a facultative cleaner of larger fishes ( Figure 5, Senegal, cleaning a muraenid, Gymnothorax afer; Brito et al. (2002, figures 364-366), Canary Islands, cleaning a muraenid and a serranid).

Remarks
The new species was classified in the genus Diplecogaster as it agrees with the generic characters given by Briggs (1955) as 3½ gills, the gill membranes attached to the isthmus, the disc double, the dorsal and anal fins with strong rays, normal, the subopercular region without a spine, 24-25 pectoral fin rays, the absence of incisors or well-   developed canines, and 13-16 rakers on the third gill arch. It is a member of the Diplecogaster-ctenocrypta group (comprising D. ctenocrypta and D. tonstricula n. sp.), which is characterised within the genus by a high number of 9 rays in the dorsal fin and 8 rays in the anal fin, and the position of the anus which is situated closer to the anal-fin origin than to the end of the disc.
The species was first described and illustrated by Brito et al. (2002, p. 281, figures 364-366) from the Canary islands, but it was confused by authors with Diplecogaster ctenocrypta Briggs 1955. A recent examination of the holotype of that deep-water species (ZMUC P9037) provided evidence that this is a separate species.
Cleaning behaviour has previously been observed in other gobiesocid fishes. Patzner and Debelius (1984) photographed a specimen of Diplecogaster bimaculata cleaning a moray eel, Muraena helena. Hutchins (1991) described Cochleoceps bicolor from southern and south-western Australia, and C. orientalis from south-eastern Australia, as setting up cleaning stations to remove parasites of other teleosts. Weitzmann and Mercader (2012) reported an observation of Lepadogaster candolii in the north-western Mediterranean Sea which was cleaning a grouper, Epinephelus marginatus.

Diagnosis
A species of Diplecogaster with 9 dorsal-fin rays, 8 anal-fin rays, 25 pectoral-fin rays, and 16 principal caudal-fin rays; pelvic disc with lateral papillae in region A; disc region B with 5 rows of papillae; principal caudal-fin rays 16; interorbital distance 5.4 in head length; distance between disc and anus 19% of SL; head and body pale, without bars or ocelli.
Description Dorsal-fin ix; anal-fin viii; pectoral-fin xxv; caudal-fin xvi. Gill rakers on 3rd arch 18, very small, pointed. Teeth small, conical, slightly recurved, in patches towards the front of each jaw, narrowing to a line of single teeth laterally. Head lateral line system with 3 pores in nasal canal, 3 pores in postorbital canal, 1 pore in mandibular canal, and 2 pores in lacrymal canal (Figure 9).

Colour in life
Unknown.

Colour in alcohol
Head and body yellowish white; eyes dark grey.

Distribution
Eastern Atlantic Ocean: Canary Islands (Gran Canaria). Probably more widespread in the region. The species was collected at 165 m depth, on hard substrate among algae.

Remarks
A record of Diplecogaster ctenocrypta (non Briggs 1955) from the Gulf of Guinea by Böhlke and Robins (1970, p. 6) is probably based on a different species.