Chriolepis bilix, Hastings, Philip A. & Findley, Lloyd T., 2013

Hastings, Philip A. & Findley, Lloyd T., 2013, Chriolepis bilix, a new species of goby (Teleostei: Gobiidae) from deep waters of the western Atlantic, Zootaxa 3745 (5), pp. 596-600 : 597-600

Chriolepis bilix sp. nov.

“Thread-spined Goby” ( Figs. 1 –3)

Dormitator (?) sp. Adams & Kendall 1891 [An obviously tentative and erroneous identification.]

Holotype: USNM 199058, adult female, 32.4 mm SL, northern edge of Little Bahama Bank, 27° 26’N, 78° 57’W, M/V Silver Bay station 3468, 25 October 1961, taken in tumbler dredge at depth of 138 m.

Paratypes. USNM 43554, 1 specimen (25.4 mm SL), sex unknown, southeastern Gulf of Mexico, off Cape Sable, southwestern Florida, 25° 02’ N, 83° 34’ W, R/V Grampus station 5057, dredge at 68-m depth, 17 or 18 February 1889; USNM 214492, 1(23.5), female, off Tobago Island, 11° 13’N, 60° 52’W, R/V Oregon station 5970, shrimp trawl at 62-m depth, 14 March 1966; USNM 214493, 1(29.9), male, off northeastern Colombia, 12° 13’N, 72° 25’W, R/V Oregon station 5699, tumbler dredge at 68-m depth, 12 October 1965.

Diagnosis. A robust, large-eyed species of Chriolepis with 12 second dorsal-fin elements, 11 or 12 anal-fin elements and 19–20 pectoral-fin rays. Body extensively scaled, mid-lateral scales extending from just behind pectoral-fin axil to caudal-fin base. Most scales weakly ctenoid; cycloid scales present on belly, in first row along dorsal- and anal-fin bases, and in anteriormost lateral row. Fifth pelvic-fin ray well developed, slightly greater in length than second pelvic-fin ray. Body relatively deep. First and second dorsal-fin spines greatly elongated, especially in females; first spine extending to posterior end of second dorsal-fin base in female holotype. First two anal-fin pterygiophores inserted anterior to first haemal spine.

Description. Vertebrae 27: 11 precaudal + 16 caudal ( Fig. 2 ). First dorsal fin with seven spines; first through fifth spines closely spaced, sixth and seventh more widely spaced. Dorsal-fin formula 3- 221110. First and second spines greatly elongated as thin filaments in both sexes, but longer in females. In females, when adpressed against the body, first spine extending posteriorly to level of insertion of first (paratype) to last (holotype) ray of second dorsal fin; second spine extending posteriorly to level of insertion of first (paratype) to ninth (holotype) ray of second dorsal fin. In the single known male, first and second dorsal-fin spines extending, respectively, to just short of, and to anterior margin of second dorsal fin. Second dorsal fin separated from the first by a distance equal to approximately one-half eye diameter. Second dorsal fin I,11 (12 total elements), last ray branched from its base. Anal fin I,10 or 11 (11–12 total elements), last ray branched from its base. First two anal-fin pterygiophores inserted anterior to first haemal spine ( Fig. 2 ). Caudal fin with nine upper and eight lower segmented rays (12 central rays branched, others broken in holotype) and seven upper and six lower procurrent rays. Pectoral fin with 19–20 branched rays; longest pectoral-fin ray extends to at least level of anal-fin origin (tips of most rays broken in holotype). Pelvic fin I,5, inserted slightly posterior to level of pectoral-fin base. Pelvic fins completely separate with no interspinal frenum and no membrane connecting innermost rays of left and right fins (a low ridge present medially between fins in USNM 214493). First through fourth pelvic-fin rays branched; longest ray (fourth) not quite reaching anus. Fifth ray well developed (not splintered to fourth), comparatively thin, unbranched, longer than second ray but shorter than third ray. Distal tips of most pelvic rays slightly flattened.

Head plump, slightly wider than deep. Cheeks not inflated. Eyes large, somewhat superior, with fleshy orbital margins. Interorbit narrow, eyes closely approximated dorsally. Lower jaw inclined upward at approximately 35 degree angle to horizontal and projecting anteriorly just beyond tip of upper jaw. Posterior margin of upper jaw extends to a vertical through anterior margin of pupil. Nostrils in short tubes; anterior tube length approximately equal to one-third pupil diameter; posterior tube approximately one-half length of anterior tube in holotype. Body, including caudal peduncle, relatively deep. Urogenital papilla wide, low, rounded and slightly papillose in female, conical in male.

Cephalic sensory pores absent. Sensory papillae (superficial or free neuromasts, “epipores”) as in Figure 3. Body extensively scaled for a Chriolepis (Fig. 3). Laterally, scales extend from just behind pectoral-fin axil to caudal-fin base in approximately 30 to 35 irregular rows. In holotype, scales extend anteriorly along bases of both dorsal fins to insertion of second dorsal-fin spine, along entire anal-fin base and across belly. Head, nape, anterior pectoral-fin base and ventral midline between inner pelvic-fin bases (= chest) naked (Fig. 3). No modified basicaudal scales present (often present in other Chriolepis species), but these may have been mechanically lost during collection from all specimens, as have some body scales. Most scales with weakly developed ctenii (2–14 per scale). Scales on belly, along dorsal- and anal-fin bases, and anteriormost lateral row lacking ctenii, appearing cycloid.

Upper jaw with an outer row of relatively large, slightly recurved canine teeth, approximately 14 per side (none greatly enlarged); teeth widely spaced anteriorly but more closely spaced postero-laterally. A patch of low, closeset teeth medial to outer row, four or five teeth wide anteriorly, tapering to three teeth wide postero-laterally. No teeth in medial patch enlarged. Upper lip well developed with numerous fleshy protuberances projecting inward between teeth of outer row (lip must be retracted to view outer row of teeth). Outer row of teeth of lower jaw with four slightly enlarged canines on each side; enlarged canines absent postero-laterally. A patch of low, close-set teeth medial to outer row, three or four teeth wide anteriorly, tapering slightly to three teeth wide postero-laterally. Inner tooth patch mostly with low, pointed, closely-set, recurved teeth, with a few slightly enlarged. No teeth present on vomer and palatines. Tongue tip slightly indented. Pseudobranchiae in seven tufts. Gill rakers short; first gill arch of holotype with three rakers on upper limb, one raker at angle, and seven rakers on lower limb (11 total rakers).

Measurements of holotype in mm: SL 32.4; predorsal length 12.2; head length 9.9; eye diameter 3.1; snout length 2.0; interorbital width 0.25; upper-jaw length 3.4; body depth 6.4; pectoral-fin length 8.3; pelvic-fin length (4th ray) 7.7; caudal-peduncle depth 4.15.

Life colors unknown. Color of holotype (in 45% isopropyl alcohol) faded yellow. Lateral aspect of body scattered with a few faint melanophores. An indistinct concentration (blotch) of melanophores present laterally on caudal peduncle. A few melanophores present on anal-fin membrane and a few on pelvic-fin membrane. No other pigment evident. All paratypes faded and in poor condition.

Distribution. Known from four widely separate offshore localities (62 to 138-m depths) throughout the Caribbean Sea and the southeasternmost Gulf of Mexico: northern edge of Little Bahama Bank; off Cape Sable, southwestern Florida; Tobago Island; and northeastern Colombia.

Etymology. From the Latin bilix meaning “with a double thread,” in reference to the two elongated, threadlike dorsal-fin spines.

Comparisons. Chriolepis bilix is the only species of morphologically similar gobies ( Chriolepis and Varicus ) in the western Atlantic with elongated dorsal-fin spines and two (rather than one) anal-fin pterygiophores inserted anterior to the first haemal spine ( Table 1 ). It resembles two other deep-living species of the genus, Chriolepis vespa Hastings & Bortone, 1981 , known from 35 to 183-m depths, and C. benthonis Ginsburg, 1953 , known from only two specimens from 154 and 350-m depths, in having a robust body, plump head and relatively large eyes. It differs from those species in having scales covering the entire lateral aspect of the body and the belly, whereas scales are restricted to the posterior half of the body in the other two species. Chriolepis bilix also differs from those two species in the length of the fifth (innermost) pelvic-fin ray which is considerably longer than the pelvicfin spine in C. bilix , but shorter than the spine in the other two species. Finally, it differs from those two species in number of elements in the second dorsal fin: 12 in C. bilix , 10 in C. vespa and 9 in C. benthonis . The only other currently recognized species of Chriolepis in the western Atlantic, the shallow-living C. fisheri , differs from all of these species in having a small body, a relatively flat head, and in lacking scales on the lateral aspect of the body (two specialized basicaudal scales are present in C. fisheri ). Chriolepis bilix differs from morphologically similar gobies in the genus Varicus , known only from the western Atlantic, in having branched pelvic-fin rays (unbranched in Varicus ), the fifth pelvic-fin ray longer than the pelvic-fin spine (shorter than the spine in Varicus ), and greater numbers of second dorsal-fin, anal-fin and pectoral-fin elements ( Table 1 ).

Chriolepis bilix closely resembles the eastern Pacific species Chriolepis atrimelum Bussing, 1997 , known from a single specimen collected at a depth of 137–146 m at Isla del Coco (Bussing, 1997). They have similar numbers of second dorsal-fin elements (12), anal-fin elements (11–12 in C. bilix versus 11 in C. atrimelum ), and pectoral-fin rays (19–20 versus 20). Both have a fully scaled body, elongate anterior dorsal-fin spines, and two anal-fin pterygiophores inserted anterior to the first haemal spine. They differ in number of mid-lateral scale rows, estimated to be 30–35 in C. bilix and 41 in C. atrimelum , dorsal fin configuration (spines I and II elongated with the first the longer in C. bilix versus I–III elongated with the second the longest in C. atrimelum ). They may also differ in coloration. Chriolepis atrimelum has a dark oval blotch on the operculum, while no such pigment is evident in the faded C. bilix specimens.

The presence of the first two anal-fin pterygiophores inserted anterior to the first haemal spine in C. bilix is unique among western Atlantic species of Chriolepis , as well as the related genus Varicus ; all other known western Atlantic species of these genera have only the first anal-fin pterygiophore inserted anterior to the first haemal spine ( Table 1 ; Birdsong et al. 1988). This feature is shared with C. atrimelum , as well as some other eastern Pacific species of Chriolepis (Birdsong et al. 1988) . Thus the importance of this character in determining relationships among the species of these poorly known genera remains unclear.

Acknowledgements

We thank Susan Jewitt for the loan of specimens. Radiographs were made possible by a grant from the National Science Foundation (DBI-1054085) to the senior author.

Figures

FIGURE 1. Holotype of Chriolepis bilix (USNM 199058).

FIGURE 2. Radiograph of holotype of Chriolepis bilix (USNM 199058).

Tables

TABLE 1. Comparison of western Atlantic species of Chriolepis and Varicus. D 2 = total second dorsal-fin elements; A = total anal-fin elements; P 1 = pectoral-fin rays (single fin); AFP = number of anal-fin pterygiophores inserted anterior to first haemal spine; * = from Birdsong et al. (1988). Data for Varicus species are from Birdsong et al. (1988), Gilmore (1979), Greenfield (1981), Robins & Böhlke (1961), and Williams & Gilbert (1983).

Species D2	A	P1	Pelvic fin rays Belly
Chriolepis benthonis 9	8	16	branched naked
Chriolepis bilix 12	11–12	19–20	branched scaled
Chriolepis fisheri 11–12	10	17–18	branched naked
Chriolepis vespa 10	7–9	15–17	branched naked
Varicus bucca 9–10	8	16–19	unbranched naked/scaled
Varicus imswe 8	8	14–15	unbranched scaled
Varicus marilynae 9	8	16–18	unbranched naked
TABLE 1. (Continued)