Lepadichthys bilineatus Craig, Bogorodsky and Randall

Craig, Matthew T., Bogorodsky, Sergey V., Randall, John E. & Mal, Ahmad O., 2015, Lepadichthys bilineatus, a new species of clingfish from Oman (Teleostei: Gobiesocidae), with a redescription of Lepadichthys erythraeus Briggs and Link from the Red Sea, Zootaxa 3990 (1), pp. 113-122 : 114-117

Lepadichthys bilineatus Craig, Bogorodsky and Randall , new species

Figure 1 ; Table 1

Holotype: BPBM 36336, 23.5 mm SL, Oman, southeastern coast, Rahah Bay, 16°57’N, 54°49’E, tidal pool (0–1.5 m), rotenone, J.E. Randall and I. McLeish, 6 February 1993.

Diagnosis. A species of Lepadichthys with origins of dorsal and anal fins posterior on body and lacking a membrane connecting them to caudal fin; dorsal-fin rays 16; anal-fin rays 13; pectoral-fin rays 23; principal caudal-fin rays 10, total caudal-fin rays 18; gill rakers 10; head large, its length 3.1 in SL; body depth 8.0 in SL; disc single; disc length 6.6 in SL; disc width 6.5 in SL; color when fresh as in Fig. 1 A, color in alcohol uniform tan ( Fig. 1 B).

Description. Dorsal-fin rays 16; anal-fin rays 13; pectoral-fin rays 23; principal caudal-fin rays 10; upper and lower procurrent caudal-fin rays 4; gill rakers 10 on second and third arches; vertebrae 34; body long and slender, its depth 8.0 in SL; head length 3.1 in SL; head width 6.5 in SL; snout length 3.4 in HL; eye diameter 5.1 in HL; caudal-peduncle depth 0.8 in its length. Disc simple, lacking fattened papillae characteristic of the genus (although may be a result of damage to the disc), single and small, length 6.6 in SL, and width 6.5 in SL; anus slightly nearer to origin of anal fin than posterior edge of disc. Mouth inferior, slightly oblique, and small; upper-jaw length 10.9 in SL; front of jaws with conical teeth. Upper attachment of gill membrane opposite eighth pectoral-fin ray. Origin of dorsal fin slightly anterior to origin of anal fin; predorsal distance 1.5 in SL; postdorsal-caudal distance 5.8 in dorsal-fin length; preanal-fin distance 1.4 in SL.

Color of holotype when fresh ( Fig. 1 A): body grayish blue, grading ventrally and posteriorly to brownish orange, and to brownish red on about posterior fourth of body; head dark brown dorsally, abruptly yellowish on ventral half, becoming bright yellow on chin; two bluish white lines extending posteriorly and angling slightly ventrally from eye, one dorsally and one ventrally from eye; pupil encircled by a distinct red ring, with a pale blue dash below; outer two-thirds of pectoral fins translucent yellowish, basal third of fin orangish brown, grading to red ventrally on chest; disc yellow; dorsal and anal fins reddish yellow with a narrow pale blue-green margin and a maroon submarginal band; caudal fin colored like body on basal fifth, followed by vertical zones of yellow and dark reddish brown, the reddish brown of rays extending anteriorly into yellow zone; outer two-fifths of fin translucent whitish. Color of holotype in alcohol uniform tan ( Fig. 1 B).

Etymology. The species name bilineatus (Latin for “two lines”) is used in reference to the two parallel bluish white lines that extend posteriorly across the head.

Remarks. The book Coastal fishes of Oman ( Randall 1995) includes species accounts of two gobiesocid fishes, the distinctive long-snouted Diademichthys lineatus , usually found sheltering among the branches of coral or the spines of sea urchins, and Lepadichthys lineatus Briggs 1966 , commensal in a crinoid (as Discotrema lineatum ; see Craig & Randall (2008) for discussion of the nomenclatural history of this species). Fish collections for the book in 1993 also included single specimens of two unidentified clingfishes. One of these was described as the new genus and species, Briggsia hastingsi by Craig & Randall in 2009; the second specimen is described here as Lepadichthys bilineatus . We regret describing these two species from single specimens. We know of no plans for additional collections.

The holotype of L. bilineatus is too desiccated to determine sensory pore number and arrangement, however we assume a similar arrangement and the same number of each pore sensu Shiogaki & Dotsu (1983).

Lepadichthys bilineatus superficially resembles L. sandaracatus Whitley 1943 and L. frenatus , two species that Briggs (1955) considered as possibly conspecific. The three species share a relatively small disc, 16 dorsal-fin rays, and 13 anal-fin rays. Lepadichthys bilineatus differs in lacking a membrane connecting dorsal and anal fins to caudal fin (dorsal and anal fins joined by membrane to caudal fin in L. sandaracatus and L. frenatus ), in having 23 pectoral-fin rays (27–28 in L. sandaracatus and L. frenatus ), a smaller eye (4.2, 4.4 and 5.1 in HL in L. sandaracatus , L. frenatus and L. bilineatus , respectively, a narrower head (head width 6.5 in SL in L. bilineatus , 4.8 in SL in L. sandaracatus , and 4.7 in L. frenatus ), and a more pointed snout. In addition, the color pattern of L. bilineatus is distinct in having two pale lines from the posterior orbit to the edge of the operculum.

The closest geographic congener of L. bilineatus appears to be L. erythraeus . These two species are easily differentiated based on color pattern and morphological characteristics (see account of L. erythraeus below).

The skin of the body of the holotype of Lepadichthys bilineatus is slightly wrinkled. We believe this may have resulted from the inadvertent partial drying of the specimen. This gives the faint impression of scales in the photograph ( Fig. 1 A), however all clingfishes known at this time lack scales. The holotype of L. bilineatus is too desiccated to determine sensory pore number and arrangement, however we assume a similar arrangement and number of pores as seen in L. erythraeus (see description below).

Recently, photographs of an unidentified clingfish taken at Musandam in the Strait of Hormuz ( Oman) were presented to the second author by Mr. Patrick Louisy. The fish was seen at a depth of 15 m among spines of diadematid sea urchin. The individual photographed ( Fig. 1 , C–D) appears similar to L. bilineatus , and if it is indeed that species, would indicate that there is variation in the overall body color of the species and the prominence of the white lines extending along the head. Unfortunately it was not collected; we are unable to confirm that the individual is in fact L. bilineatus .

Figures

FIGURE 1. Lepadichthys bilineatus. BPBM 36336, holotype, 23.5 mm SL, Rahah Bay, Oman. A: Recently collected (white underside enhanced by a light used below to eliminate shadows); B: Preserved. C & D: Lepadichthys cf. bilineatus (not collected), Musandam, Strait of Hormuz, Oman. Photos by J. E. Randall (A), M. Craig (B), P. Louisy (C & D).

Tables

TABLE 1. Morphometric (expressed as % SL) and meristic data of Lepadichthys bilineatus n. sp. and L. erythraeus. Count of caudal-fin rays given as number of principle rays followed by total rays in parentheses.

Specimen Standard length (mm) Body depth Body width	Lepadichthys bilineatus n.sp. BPBM 36336, holotype 23.5 12.8 17.9	SMF 5586, holotype 36.6 14.5 15.6	BPBM 40985 19.1 12.6 13.1	KAUMM 318 (KAU13-366) 25.9 12.4 16.2	Lepadichthys erythraeus SMF 35410 USNM KAUMM (KAU13- 314225 319 367) 26.6 28.5 35.3 12.4 12.3 13.6 15.8 14.7 16.4	SMF 35410 (KAU13-365) 36.0 13.1 16.7	KAUMM 318 36.2 13.3 16.8	SMF 35411 (KAU13- 634) 37.9 14.5 16.9
Head length	32.8	34.2	33.5	32.8	32.0 35.0 31.4	32.8	31.2	33.0
Head width Snout length Orbit diameter	15.7 9.8 6.4	19.1 10.7 6.0	18.3 8.4 5.2	16.2 10.4 6.5	16.2 16.8 16.7 10.5 12.6 10.5 6.4 6.3 6.0	17.2 11.1 6.1	16.3 10.5 5.5	18.5 11.1 5.3
Interorbital width Upper-jaw length Caudal-peduncle depth	6.4 9.4 5.1	8.8 8.2 7.4	6.3 7.9 6.8	7.3 8.5 7.7	7.1 7.0 9.1 8.3 8.8 10.2 7.5 8.1 9.1	10.0 8.1 7.2	9.1 9.9 9.1	9.8 9.8 9.2
Caudal-peduncle length Postdorsal-caudal distance Predorsal length Preanal-fin length	3.8 5.1 70.2 73.2	4.4 4.4 66.7 77.9	4.2 4.2 66.5 73.8	4.3 3.9 67.6 71.8	4.5 4.2 4.2 4.5 3.9 4.2 65.4 67.4 63.2 69.2 77.5 72.2	4.4 4.2 60.0 72.2	4.4 4.4 61.9 70.4	4.5 4.5 69.7 78.8
Dorsal-fin length Anal-fin length Caudal-fin length Pectoral-fin length	29.4 24.3 23.9 9.4	28.7 23.2 13.9 13.7	27.7 18.8 9.9 9.9	32.4 28.2 12.4 11.2	33.1 29.5 28.9 27.8 27.7 23.8 12.0 13.3 14.7 10.9 11.2 11.9	29.4 27.3 12.8 9.7	28.5 23.5 14.6 11.6	30.3 25.4 17.7 13.2
Pelvic-disc length	15.2	15.8	15.2	13.9	13.2 13.3 14.7	14.2	14.4	14.5
Meristics Dorsal-fin rays Anal-fin rays	16 13	16 13	15 13	15 13	15 15 15 13 13 13	16 13	15 13	15 13
Pectoral-fin rays Caudal-fin Rays*	23 10 (18)	28 12 (20)	27 12 (20)	26 12 (20)	26 26 26 12 (20) 12 (20) 12 (20)	26 12 (20)	26 12 (20)	27 12 (20)
Gill Rakers (2nd arch)	10	8	8	8	8 8 8	8	8	8