Coryphopterus curasub, Baldwin, Carole C. & Robertson, D. Ross, 2015

Baldwin, Carole C. & Robertson, D. Ross, 2015, A new, mesophotic Coryphopterus goby (Teleostei, Gobiidae) from the southern Caribbean, with comments on relationships and depth distributions within the genus, ZooKeys 513, pp. 123-142 : 125-132

Taxon classification Animalia Gobiiformes Gobiidae

Coryphopterus curasub sp. n. Yellow-spotted sand gobyFigs 1, 2

Type locality.

Curaçao, southern Caribbean

Holotype.

USNM 406373, Smithsonian DNA number CUR 11373, 33.3 mm SL, female, Curasub submersible, sta. 11-05, southern Caribbean, Curaçao, east of downline off Substation Curaçao dock, near 12°05.069'N, 68°53.886'W, 80 m, quinaldine, 30 May 2011, D. R. Robertson, B. Brandt, A Schrier, K. Stewart.

Paratypes.

USNM 430037, CUR 13302, 30.0 mm SL, male, Curasub submersible, sta. 13-29, southern Caribbean, Curaçao, east of downline off Substation Curaçao dock, near 12°05.069'N, 68°53.886'W, 70-72 m, quinaldine, 30 October 2013, C. C. Baldwin, D. R. Robertson, B. Brandt, C. Castillo, L. Ybarrondo. USNM 431328, CUR 14003, 31.0 mm SL, male, Curasub submersible, sta. 14-01, southern Caribbean, Curaçao, east of downline off Substation Curaçao dock, near 12°05.069'N, 68°53.886'W, 73 m, quinaldine, 17 March 2014, C. C. Baldwin, D. R. Robertson, B. Brandt, C. Castillo, H. Reichardt. USNM 430019, CUR 13303, 17.5 mm SL, immature (same collection locality as USNM 430037), cleared and stained.

Generic assignment.

The combination of six spines in the first dorsal fin, fewer than 20 rays in the second dorsal fin, pelvic fin with one spine and five soft rays, head pores present, no free pectoral-fin rays, no scales on top of head, and no prominent crest on top of head anteriorly from first dorsal fin support the placement of Coryphopterus curasub in the genus Coryphopterus ( Murdy 2002).

Diagnosis.

A species of Coryphopterus distinguishable from its congeners by the following combination of characters: total second dorsal-fin rays (spinous plus soft) 10-11, usually 11; total anal-fin rays (spinous plus soft) 10; pectoral-fin rays 19-20; pelvic fins united; no pelvic frenum; pectoral-fin base with two prominent dark spots (yellow with dark spotting in life) of roughly equal intensity, one on dorsal portion of fin base and one on ventral part; no distinct black blotch behind orbit above opercle; no dark triangular blotch immediately behind middle of orbit; blotches of pigment on trunk mostly yellow; few melanophores and yellow dots interspersed among yellow blotches of pigment on trunk; no black ring of pigment surrounding anus; dark triangular blotch variously developed beneath anteroventral corner of orbit; basicaudal blotch cross-shaped, with prominent anterior projection; and two yellow/orange blotches on base of caudal fin situated immediately behind basicaudal blotch.

Description.

Dorsal-fin rays VI + I, 9-10 (9 in one paratype, 10 in other specimens), total second dorsal-fin rays 10 or 11 (10 in one paratype, 11 in other specimens); anal-fin rays I, 9; all soft dorsal- and anal-fin rays branched. Pectoral-fin rays 19, 19 (paratypes) or 20, 20 (holotype); all pectoral rays branched except splint-like uppermost and lowermost rays. Pelvic-fin rays I, 5; all soft rays branched; fins unit ed, no frenum. Total caudal-fin rays (including procurrent rays) 30 (holotype) or 31 (cleared and stained paratype; can’t assess number from radiographs of other paratypes); segmented caudal rays17; branched caudal rays12 (6+6); unbranched caudal rays 18 in holotype (9+9), 19 (10+9) in cleared and stained paratype. Dorsal-fin formula 3-22110. Vertebrae 10 precaudal +16 caudal. Epineurals 10 pairs. Ribs on vertebrae 3-10. Anal-fin pterygiophores anterior to first haemal spine 2. Gill rakers on first arch, including rudiments, 2 + 8 (holotype and adult paratypes), 0 + 8 in cleared and stained juvenile paratype. Branchiostegal rays 5. Numerous scales abraded and missing on all specimens, one paratype with approximately 22 scales in longitudinal series, 6 scales between origin of second dorsal fin obliquely downward to anal fin, and approximately 17 circum-peduncular scales.

Measurements of holotype in parentheses following extremes for holotype plus two adult paratypes. Juvenile paratype bent and not measured prior to clearing and staining. Body elongate, maximum depth from base of dorsal-fin spines 17-19% SL (17); body compressed, greatest width just posterior to gill opening 14-15% SL (14); head length 30-32% SL (32); snout length (to fleshy edge of orbit) 6.0-7.1% SL (6.0); greatest fleshy orbit diameter 9.3-10% SL (9.3); least fleshy interorbital 1.3-3.3% SL (3.3); caudal-peduncle length 23-24% SL (23); least caudal-peduncle depth 11-12% SL (11); length of dorsal-fin base 39-46% SL (46); first dorsal spine 14-16% SL (16); second dorsal spine 15-18% SL (17); third and longest dorsal spine 16-20% SL (18); sixth and shortest dorsal spine 7.0-8.4% SL (8.4); seventh dorsal spine (first element of second dorsal fin) 14-16% SL (16); last dorsal soft ray 16-17% SL (16); anal-fin spine 8.7-11% SL (11); last anal soft ray 20-22% SL (20); pectoral fin 32-36% SL (36), fin reaching vertical through second anal-fin soft ray, longest pectoral rays the 11th-14th rays from top of fin; pelvic fin 24-32% SL (27), fin reaching origin of anal fin or terminating slightly before origin, longest pelvic ray the fourth.

Trunk, belly, and pre-pelvic region scaled, head and predorsal region naked; scales ctenoid except on pre-pelvic region, where they are cycloid. Upper jaw with several rows of small conical teeth, outermost teeth largest but smaller than outermost dentary teeth; dentary with outer row of fairly large conical teeth and several inner rows of smaller teeth; innermost teeth intermediate in size between teeth of outermost row and those adjacent to it. No teeth on vomer, palatines, or pterygoids. Anterior nare opening on short tube; posterior nare a simple opening. Head pores prominent: nasal pore, anterior interorbital pore, posterior interorbital pore, infraorbital pore, postorbital pore, pore at each end of lateral sensory canal, pore at each end of posterior lateral canal, and three preopercular pores (pores B’, C and D [both single], E, F, G, H’, K’, L’, M’, N, O’). A very low, thin ridge of tissue extending from just posterior to interobital region to base of first dorsal fin.

When photographed against a light background (Fig. 2A), the following color pattern visible in holotype. TRUNK: ground color white, several irregular horizontal rows of yellow/orange irregular-shaped blotches, most blotches bordered by and peppered with small black melanophores; uppermost row comprising approximately 11 blotches distributed along dorsal body margin from head (with two-three blotches) to caudal peduncle; second row shortest, comprising approximately eight blotches and extending from just posterior to posterodorsal margin of orbit to vertical through third or fourth dorsal-fin spine; third row comprising approximately 15 blotches and extending from middle of posterior margin of orbit to caudal peduncle-anterior blotches of this row united to form irregular stripe; lowermost row comprising five prominent blotches that extend from vertical through anterior origin of second dorsal fin to posterior portion of caudal peduncle and several less conspicuous blotches anterior of and within this series; this row continuing anteriorly onto pectoral-fin base and head as an irregular yellow stripe that passes along ventral margin of orbit and terminates on posterior end of upper jaw; yellow blotches on anterior portion of trunk and head better defined by peripheral melanophores than those on posterior portion of trunk; scattered small spots of yellow/black pigment interspersed among blotches in most rows. HEAD: head pigment also including short yellow/black stripe on snout; yellow stripe on ventral portion of head from posterior end of lower jaw to preopercle; triangle of black pigment beneath anteroventral margin of orbit; scattered black dots on upper lip, on snout, and beneath eye; two small black blotches of pigment on operculum; some whitish pigment extending posterodorsally from dark triangle beneath orbit; pu pil black, iris brown; ventral portions of head and trunk mostly white except for streak of yellow pigment beneath opercular opening. CAUDAL PEDUNCLE: dark cross-shaped basicaudal blotch present on central portion of caudal peduncle and caudal-fin base, the anterior projection of cross prominent; two yellow spots bordering dorsal and ventral ends of blotch posteriorly and extending onto bases of several caudal-fin rays. FINS: first dorsal fin translucent, with three irregular yellow stripes; second dorsal fin with three or four irregular yellow stripes; anal fin with broad stripe of pale yellow pigment on middle of fin; caudal fin with blotches of yellow pigment forming an arc on basal portion of fin, some of this pigment extending distally along caudal rays as barely noticeable yellow streaks; pectoral and pelvic fins mostly clear; yellow/black blotch on dorsal portion of pectoral-fin base extending onto basal portion of dorsalmost pectoral rays; lower portion of pectoral-fin base with well-defined, round, yellow/orange blotch with dark dots. When photographed against a black background (Fig. 1B), numerous small, white, round to oblong spots visible on membranes of all fins; distal margin of anal fin with pale blue stripe.

Male paratypes (Fig. 1C) with similar coloration except black triangle of pigment beneath anteroventral corner of eye less conspicuous; melanophores present on lower jaw; iris mottled whitish/bronze; pectoral fin with pale yellow pigment; and pelvic fin with black-spotted yellow patches. IMMATURE SPECIMEN (Fig. 1D) paler but with most pigment described above developing; diagnostic cross-shaped marking on caudal peduncle not formed, and only lower black-spotted yellow blotch on pectoral-fin base well formed; most prominent pigment comprising yellow stripes on head, five black-spotted yellow blotches on trunk in lowermost row, and black-spotted yellow blotch in line with this row on base of caudal fin.

Color of holotype in alcohol (Fig. 1A). Ground color of head and trunk light tan, overlain by assorted dark circles, stripes, and irregular markings. Scattered melanophores and blotches present along base of spinous dorsal fin and on dorsal portion of trunk. Most prominent trunk pigment located just ventral to lateral midline as a row of six mostly circular blotches of roughly equal size except the second from anterior and last, which are small relative to the others; this row of pigment markings originating at a vertical through second element of second dorsal fin and terminating on caudal peduncle. Head with several circular blotches in row posterior to posterodorsal portion of orbit; irregular stripe of pigment extending posteriorly from middle of orbit; irregular stripe-like mark extending posteriorly from posteroventral portion of orbit; scattered melanophores on snout, lacrimal, and upper jaw; dark triangle of pigment beneath anteroventral corner of orbit; and two irregular streaks of pigment on ventral portion of operculum. Dark portion of basicaudal blotch as described above, but no melanophores present on remainder of caudal fin or on anal and pelvic fins. First dorsal fin with small bits of dark pigment on membranes of second, third and fifth spines. Pectoral-fin base with one dorsal and one ventral circular blotches, the former extending as short series of melanophores posteriorly onto bases of dorsal rays of fin.

Distribution.

Known from 70-80 m off Curaçao, southern Caribbean.

Habitat.

Notes recorded during the submersible dive on which the 33.0 mm SL paratype (USNM 431328) was collected indicate that it occurred on sand with rubble patches on a 45°slope.

Etymology.

Named for the manned submersible Curasub, which is owned and operated by Substation Curaçao, in recognition of the contributions of this vehicle to increasing our knowledge of the Caribbean deep-reef fish fauna.

Common name.

"Yellow-spotted sand goby" refers to the yellow spots on the trunk and the collection habitat.

Morphological comparisons.

Coryphopterus curasub is most similar to Coryphopterus dicrus (Fig. 2) and keys to that species in the most recent dichotomous key to western Atlantic Coryphopterus ( Baldwin et al. 2009). They share the presence of two dark circular markings on the pectoral-fin base that are of roughly equal intensity (except in the juvenile Coryphopterus curasub , in which only the lower spot is prominent), the absence of a distinct black blotch or triangle of pigment behind the eye above the opercle in adults, the presence of a united pelvic fin in which the fourth rays are longer than the fifth, and the absence of a pelvic frenum. They usually differ in total number of rays (spinous plus soft) in the second dorsal fin (10-11, usually 11, in Coryphopterus curasub , 10 in Coryphopterus dicrus ); absence of a dark triangular blotch immediately posterior to the orbit in Coryphopterus curasub (present in Coryphopterus dicrus ); presence of a dark triangular blotch beneath the anteroventral portion of the orbit in the largest specimen (33.3 mm SL holotype) of Coryphopterus curasub (absent in similarly large specimens of Coryphopterus dicrus ); blotches of pigment on the trunk typically yellow in Coryphopterus curasub , orange to rusty brown in Coryphopterus dicrus ; few yellow spots with tiny melanophores among the yellow blotches of pigment on the trunk in Coryphopterus curasub vs. many rusty spots with tiny melanophores between the rusty brown blotches in Coryphopterus dicrus ; configuration of the basicaudal blotch (a cross-shaped blotch with a distinct anterior projection in Coryphopterus curasub vs. a dumbbell-shaped bar in Coryphopterus dicrus ); the two yellow/orange blotches on the base of the caudal fin situated immediately behind the basicaudal blotch in Coryphopterus curasub vs. superimposed on and contributing to the upper and lower heads of the basicaudal bar of Coryphopterus dicrus ; maximum body depth from base of spinous dorsal fin (17-19% SL in Coryphopterus curasub , 20-26% SL in Coryphopterus dicrus - Böhlke and Robins 1960); least depth of caudal peduncle (11-12% SL in Coryphopterus curasub , 13-15% SL in Coryphopterus dicrus - Böhlke and Robins 1960). Coryphopterus curasub differs from all other western Atlantic Coryphopterus ( Coryphopterus alloides Böhlke & Robins, Coryphopterus eidolon , Coryphopterus glaucofraenum , Coryphopterus hyalinus , Coryphopterus kuna , Coryphopterus lipernes , Coryphopterus personatus , Coryphopterus punctipectophorus , Coryphopterus thrix , Coryphopterus tortugae , and Coryphopterus venezuelae ) in having two round dark marks on the pectoral-fin base that are of roughly equal intensity in adults. It further differs from Coryphopterus hyalinus , Coryphopterus lipernes , and Coryphopterus personatus in lacking a black ring around the anus; from those species and Coryphopterus alloides in having the pelvic fin united; from Coryphopterus glaucofraenum , Coryphopterus tortugae , and Coryphopterus venezuelae in lacking both a pelvic frenum and a distinct black blotch or triangle behind the eye above the opercle; and from Coryphopterus kuna in having 10 or 11 total second dorsal-fin rays, 10 total anal-fin rays, and 19-20 pectoral-fin rays (vs. 9, 9, and 15, respectively).

Of the 14 apomorphic morphological characters of Coryphopterus species tabulated by Thacker and Cole (2002) for inclusion in their phylogenetic analysis of the genus, Coryphopterus curasub has (character 1) no pelvic frenum, (3) the fifth (innermost) pelvic-fin ray shortened relative to the fourth, (4) a low ridge of tissue on top of the head, (8) orange or gold coloration on the body, and (10) three stripes of pigment on the head. The presence of a low ridge of tissue on the head characterizes all Coryphopterus species and is thus uninformative. Likewise, although Thacker and Cole (2002) scored most species as lacking orange or gold coloration, in a more thorough analysis of fresh color patterns in western Atlantic Coryphopterus , Baldwin et al. (2009) noted the presence of yellow/orange/gold pigment in all species. Coryphopterus curasub shares with Coryphopterus dicrus , Coryphopterus alloides , Coryphopterus personatus , Coryphopterus hyalinus , and Coryphopterus lipernes the absence of a pelvic frenum, with those taxa and Coryphopterus eidolon a shortened fifth pelvic-fin ray (relative to the fourth), and with Coryphopterus eidolon , Coryphopterus thrix , Coryphopterus dicrus , Coryphopterus glaucofraenum , Coryphopterus tortugae , Coryphopterus venezuelae , Coryphopterus urospilus , and Coryphopterus punctipectophorus the presence of three stripes of pigment on the head. In Coryphopterus curasub , the lowermost stripe (on the cheek) is yellow and lacks melanophores, which are present in the other species. The homology of the pigment stripes is thus questionable. Thacker and Cole (2002) list several apomorphic characters (11-13) related to basicaudal pigment, but the configuration of the basicaudal blotch in Coryphopterus curasub is unique among Coryphopterus species. Thacker and Cole’s (2002) 14th character, the presence or absence of a pigment spot on the pectoral-fin base, insufficiently describes the variation in this character in Coryphopterus . Of the various configurations-no spots, one spot dorsally, one spot ventrally, two spots with upper spot more intense, two spots of roughly equal intensity-only Coryphopterus curasub and Coryphopterus dicrus have two spots of equal intensity among Coryphopterus species and outgroup taxa. In summary, of the potentially informative, putative apomorphic characters exhibited by Coryphopterus curasub , only Coryphopterus dicrus shares all of them.

Genetic comparisons.

COI sequences derived from tissue samples from the four type specimens of Coryphopterus curasub and three specimens of Coryphopterus venezuelae collected by submersible as part of this study (Appendix) were combined with 173 previously published COI sequences for western Atlantic Coryphopterus ( Baldwin et al. 2009, Weigt et al. 2012b) in a neighbor-joining analysis (Fig. 3). Intraspecific divergence in COI for Coryphopterus curasub was 0.1% as compared to 17-23% interspecific divergence between Coryphopterus curasub and other western Atlantic Coryphopterus species, including Coryphopterus dicrus (18%, Table 1). Intraspecific divergences for all western Atlantic Coryphopterus species were <1% except for Coryphopterus alloides (3.7%), likely reflecting, as suggested by Baldwin et al. (2009), a cryptic species that awaits investigation. Phylogenetic relationships within Coryphopterus were analyzed using a reduced COI dataset of western Atlantic Coryphopterus (43 ingroup sequences selected from the entire COI data set to maximize geographical coverage of each species), the eastern Pacific Coryphopterus urospilus , and the western Atlantic Lophogobius cyprinoides . A strict consensus of 24 trees resulting from a maximum parsimony analysis (Fig. 4) does not resolve the relationships of Coryphopterus curasub with confidence. A clade comprising Coryphopterus venezuelae , Coryphopterus glaucofraenum , and Coryphopterus tortugae is strongly supported (99%), as are clades comprising Coryphopterus venezuelae and Coryphopterus glaucofraenum (80%), the hovering species Coryphopterus hyalinus and Coryphopterus personatus (100%), and the planktivores Coryphopterus lipernes + Coryphopterus hyalinus + Coryphopterus personatus (63%). As noted by Thacker and Cole (2002) based on ND2 mitochondrial and morphological data, Lophogobius is closely related to Coryphopterus , here appearing in a poorly supported clade that also comprises Coryphopterus dicrus and the eastern Pacific Coryphopterus urospilus . Adding more loci to the genetic analysis as well as Coryphopterus punctipectophorus and the eastern- and Indo-Pacific species of Lophogobius may help resolve interspecific and generic relationships. The placement of Coryphopterus kuna outside of the western Atlantic Coryphopterus + Lophogobius cyprinoides clade warrants further morphological and molecular investigation.

Depth distributions.

Depth ranges of Coryphopterus species are shown in Figure 5. Coryphopterus curasub , which is known from 70-80 m, is the only member of the genus that has a narrow depth range completely confined to mesophotic depths. Coryphopterus venezuelae , Coryphopterus glaucofraenum , Coryphopterus dicrus , Coryphopterus eidolon , Coryphopterus thrix , Coryphopterus hyalinus , Coryphopterus lipernes , and Coryphopterus personatus inhabit depths as deep as 52-70 m, but they have broad depth ranges that extend as shallow as 1-6 m. The only Coryphopterus species in addition to Coryphopterus curasub that we have collected using the Curasub submersible are Coryphopterus hyalinus - one specimen from 33 m, and Coryphopterus venezuelae - three specimens from 65-69 m. Prior to this study, Coryphopterus venezuelae was known from 1-20 m ( Robertson and Van Tassell 2015), and thus our new collections of the species off Curacao extend its known range by nearly 50 m.