Gobiodon bilineatus Herler, Bogorodsky & Suzuki, 2013, sp. nov.

Gobiodon bilineatus sp. nov.

Two-lined Coralgoby

Figs. 1, 2, 10 & 11; Tables 1, 2, 3 & 10

Gobiodon sp. 1 Herler and Hilgers 2005 (part): 120, Figs. 13c–e; Bogorodsky et al. 2010: 122, Figs. 3, 4.

Holotype. NMW 95077 (CH 232–41–011 in Herler & Hilgers, 2005), male 35.7 mm SL, Gulf of Aqaba, Egypt, Dahab, “Islands” (28°28’38.5” N, 34°30’47.1” E), coll. M. Dirnwoeber, 17 April 2004.

Paratypes. Four specimens. NMW 95563, 32.9 mm SL, Gulf of Aqaba, Egypt, Dahab, “Soliman Reef” (28°28’47.0” N, 34°30’51.8” E), coll. J. Herler, 2 May 2010. NMW 95564, juvenile, 22.7 mm, same data as NMW 95563. MNHN 2012-0262, 34.9 mm SL, other data same as NMW 95563. BMNH 2006.10.6.1, 29.4 mm SL, 30 May 2010, other data same as NMW 95563.

Additional material. CH 232-41-063 (DNA sample + photograph), juvenile, 18.0 mm SL, Egypt, Dahab, coll. J. Herler, 30 May 2012; PMR VP 2234, 32.7 mm SL, Yemen, Hanish Island, coll. S.V. Bogorodsky, 23 October 2009; PMR VP 3200, 23.7 mm SL, Egypt, Sharm el Sheikh, Sharm el Moya, coll. S.V. Bogorodsky, 0 4 July 2011.

Comparative material. Gobiodon cf. bilineatus: uncatalogued (DNA sample; Fig. 9 A), 28.9 mm SL, Maldives, Kagi Island, coll. J. Herler, 16 March 2007; uncatalogued (DNA sample; Fig. 9 B), 22.9 mm SL, southern Taiwan, Kenting, coll. J. Herler, 0 6 December 2008. Gobiodon prolixus: holotype, ROM 73338 (Fig. 9 C), male, 26.2 mm, Vietnam, Nha Trang, coll. R. Winterbottom, W. Holleman, B. Hubley, M. Burridge, M. Winterbottom and N. Vij, 27 May 2002; ROM 84987, female, 19.6 mm, Yemen, Hanish Island, coll. S.V. Bogorodsky, 23 October 2009; PMR VP 2233, female, 18.9 mm SL, Yemen, Hanish Island, coll. S.V. Bogorodsky, 23 October 2009. Gobiodon sp. D sensu Munday et al., (1999): uncatalogued (DNA sample; Fig. 9 D), 29.9 mm SL, Maldives, Hembadhu Island, coll. J. Herler, 18 March 2007. Gobiodon quinquestrigatus: uncatalogued (DNA sample, Fig. 9 E), 28.7 mm SL, southern Taiwan, Kenting, coll. J. Herler, 0 4 December 2008.

Diagnosis. Dorsal-fin rays VI + I,10–11; anal-fin rays I,8–9 (usually 9); head and body naked; body slightly compressed, relatively elongate (body depth at pelvic-fin origin 36–40% SL), dorso-ventrally symmetrical; distance between D1 insertion and dorsal insertion of pectoral-fin 53–71% of head length; head rounded, with upper lip curved; mouth small, upper jaw extending to anterior margin of the eye; no groove between isthmus and interopercle; caudal peduncle deep (minimal depth 16.3–17.9% SL); caudal fin relatively short (21.7–23.2% SL). Juveniles and subadults light greenish or reddish with five vertical blue lines on head; adults usually uniformly orange-red or dark red, sometimes with remnants of lines on the head but always with two distinct bluish lines through the eyes, sometimes extending ventrally to suborbital area; dorsal fins and anal fin often with a narrow light bluish band along bases, fading with growth.

......continued on next page TABLE 1. (Continued)

* recently described as G. aoyagii by Shibukawa et al. (2013)

Description (based on 5 types and several non-type specimens (for osteology)). Head and body only slightly compressed. Body dorso-ventrally symmetrical, head rounded, caudal peduncle deep. Body proportions and meristics for types are provided in Tables 2 and 3, respectively. Dorsal-fin rays VI + I, 10 –11 (10:3, 11:2); anal-fin rays I,8– 9 (8:1, 9:4); pectoral-fin rays 19 –20 (19:3, 20:2); pelvic-fin rays I,5 (all specimens); caudal fin with 15–17 segmented and branched rays; disc short (not reaching anus) and cup-shaped, with significant frenum between spines. First dorsal fin rounded and as high as second dorsal in juveniles, but shorter than D 2 in adults. Vertebral column with 10 precaudal and 16 caudal vertebrae, including urostyle. No scales. Gill opening less wide than pectoral-fin base, ending ventrally in opposite of 3rd or 4th lower pectoral-fin ray. Gill rakers 1–2 + 7–8. No obvious groove between interopercle and isthmus. Mouth terminal, slightly oblique, bending downwards. Upper jaw reaching to below anterior orbital margin. Upper lip usually curved, slightly extends in front of snout. One outer row of 5 to 12 larger, slightly recurved teeth in upper and lower jaw, and increasing in size towards symphysis. Several rows of small, slender and recurved teeth in both jaws behind the outer row. Lower jaw with a pair of large, postsymphysial canines on each side, one often smaller or absent, probably due to tooth loss and replacement. Anterior and posterior nasal openings at the end of short tubes. Head sensory canals typical for Gobiodon (Winterbottom & Harold 2005), with anterior oculoscapular (pores NA (paired), AI, PI (unpaired), SO, AO and IT (paired)) and preopercular (three pores on each side) canals present.

Life colouration. Juveniles reddish or greenish with five vertical blue lines across head (Fig. 2 D), first and second through eye and cheek, third and fourth across anterior and posterior margin of opercle, and fifth across pectoral-fin base. Adults mostly uniformly bright orange-red (Figs. 1 A, 2A). Smaller adults sometimes with remnants of blue lines on the head (Figs. 2 B, C). Large adults mostly only with two distinct bright blue lines through eye. A narrow, pale bluish band sometimes visible along the dorsal-fin bases.

Preserved colouration. Uniformly light or dark brown. Lines on head and/or through eyes diminished (Fig. 1 B).

Molecular genetics. The present analysis includes two newly sequenced specimens from the Red Sea because Herler et al. (2009) sequenced only specimens that have now been assigned to G. irregularis sp. nov. In addition, similar-looking specimens from the Maldives and Taiwan were included. See Table 1 for Genbank accession numbers. The genetically closest described species to G. bilineatus sp. nov. is G. quinquestrigatus (Valenciennes 1837) (Fig. 11). The p -distance between the two species is 0.033 (genetic distance>3%).

Status Holotype Paratype Paratype Paratype Paratype MEAN Coll.No. NMW NMW NMW MNHN BMNH (±SD)

95077 95563 95564 2012-0262 2006.10.6.1

SL (mm) 35.7 32.9 22.7 34.9 29.4

Snout to first dorsal-fin origin 36.3 36.6 34.7 34.8 38.0 36.1 (1.4) Habitat. Gobiodon bilineatus sp. nov. most frequently occupies the reef slope and fore reef areas. It is often found in large colonies of Acropora samoensis but is also present in A. secale and A. gemmifera in the northern Red Sea.

Distribution. This species was found in the Gulf of Aqaba, in the northern Red Sea main basin (near Marsa Alam, Egypt and Al Wajh, Saudi Arabia) and in the southern Red Sea (Dahlak Archipelago, Eritrea; Hanish Island, Yemen). Its distribution range may extend to the Indian and western Pacific Ocean (see Remarks and Fig. 9).

Etymology. This species is named for its two distinct, bright blue lines through the eye, which is the only distinct colour pattern that remains in the largest adults when alive. The name “ bilineatus ” is derived from the latin words “bi“, meaning two, and “linea” for line. Suggested common name: Two-lined Coralgoby. Allen and Erdmann (2012) already used the common name Twoline Coralgoby for their G. sp. 2, but they actually show G. fulvus sensu Winterbottom and Emery (1986), a species known under the common name Brown Coralgoby.

Remarks. Herler and Hilgers (2005) mistook two genetically but also morphologically distinct species for one: G. bilineatus and G. irregularis sp. nov. were erroneously pooled as Gobiodon sp. 1. The authors considered G. irregularis sp. nov. as the juvenile/subadult form of G. bilineatus. Only our recent genetic investigations revealed that the juveniles of G. bilineatus are actually rather uniformly coloured with 5 blue lines on the head as the only distinctive colour pattern. Therefore, very small (<1 cm SL) G. bilineatus may be almost indistinguishable from similar-sized G. rivulatus, G. quinquestrigatus, G. sp. D sensu Munday et al. (1999) or G. prolixus Winterbottom and Harold (2005), with at least the three former also being genetically close taxa (Fig. 11). There are also no unique fin meristic features which could help to discriminate between them (see also Herler & Hilgers 2005, and Winterbottom & Harold 2005). Although the lesser body depth and shorter D1-P1-distance of G. prolixus (28.2– 35.5% SL and 41.3–50.4% of head length, respectively, vs 36–40% SL and 53.4–70.4% of head length in G. bilineatus) may help distinguish this species when adult (although differences in colouration will then also be evident), it is doubtful that these body proportions are also distinct in juveniles. Adult G. bilineatus, however, are distinct in that the 5 vertical blue lines disappear with growth, and in their bright orange-red colour. As mentioned, the three most similar and also genetically closest species are G. quinquestrigatus, G. sp. D sensu Munday et al. (1999) and G. rivulatus. According to Duchene et al. (2013), the two former species are genetically distinct. All four species can be distinguished by slight differences in life colour, although field identification may be very difficult, in particular between the two former species and G. bilineatus. Gobiodon rivulatus is most easily distinguished by the three or more additional, shorter lines on the head, which are positioned in the interspaces of the typical five long lines on the head, and by the many more irregular lines on the body (particularly visible in lighter coloured forms). By contrast, the other three species have only five bluish lines on head (sometimes a very short sixth line behind the upper pectoral-fin base), all in the same position (Figs. 2 B, C, 9D, E). When lines on the head disappear in adults of G. bilineatus, this species is characterised by a uniformly orange-red colour, including the fins (Figs. 1 A, 2A). Gobiodon quinquestrigatus differs by its very distinct and bluish lines on head, which remain in adults on the otherwise orange-brown head, and by its dark brown body colouration. Gobiodon sp. D sensu Munday et al. (1999) has a reddish body colouration, less distinct bluish lines on head, and brown fins that are darker than the body. The latter species and juveniles and subadults of G. bilineatus are similar to each other in that a narrow bright bluish band is frequently present along the dorsal-fin bases. This feature is less distinct or absent in Gobiodon quinquestrigatus. It is unclear whether the Indian Ocean (Maldives) and western Pacific (Taiwan) populations (designated as G. cf. bilineatus herein) should be considered as G. bilineatus or as a very closely related, but distinct species (Figs. 9, 11). They differ from typical G. bilineatus in that the maximum size seems to be smaller (many specimens were observed in the Maldives and collected by JH) and their life colour is much darker (Figs. 9 A, B). Note that life colour is usually distinct in different Gobiodon species. Although they show genetic distances (Table 10) of <1.4%, we refrained from including this material in the species description because the distinct life colouration strongly indicates that it is a separate species.