Opistognathus vicinus, Smith-Vaniz, William F., Tornabene, Luke & Macieira, Raphael M., 2018

Smith-Vaniz, William F., Tornabene, Luke & Macieira, Raphael M., 2018, Review of Brazilian jawfishes of the genus Opistognathus with descriptions of two new species (Teleostei, Opistognathidae), ZooKeys 794, pp. 95-133 : 104-109

Opistognathus vicinus sp. n. Figures 4B, 5B, 8, 9; Tables 1, 2, 4

Opistognathus whitehursti (Longley, 1927): Simon et al. 2013b (listed).

Holotype.

CIUFES 0796, 43.0 mm SL, male, Ilha Rasa de Dentro, Guarapari, Espírito Santo, 20°40'S, 40°21'W, 15m, 11 March 2008, R. M. Macieira and T. Simon.

Paratypes.

(12 specimens 17.0-47.4 mm SL) all from Brazil Province: UF 239659 (2, 27.9-31.0), taken with the holotype; CIUFES 0868 (1, 38.3*), Ilha Rasa de Dentro, Guarapari, Espírito Santo, 20°40'S, 40°21'W, 10 m, 29 January 2008, V.C. Brilhante; USNM 440402 (1, 38.6*), Ilha das Garças, Vila Velha, Espírito Santo, 20°36'S, 40°22'W, 30 March 2000, J.L. Gasparini; MZUSP 123869 (1, 38.9), MNRJ 51284 (1, 17.0), ZUEC 16915 (1, 42.5*) and AMNH 267141 (2, 21.7-38.9*), Ilha Escalvada, Guarapari, Espírito Santo, 20°42'S, 40°24'W, 21 m, 23 February 2010, R.M. Macieira, T. Simon and C.R. Pimentel; NPM 5030 (1, 47.4*), Ilha Rasa de Dentro, Guarapari, Espírito Santo, 20°40'S, 40°21'W, 31 October 2005, R.M. Macieira and J.-C. Joyeux; CIUFES 0467 (1, 26.2), Ilhas Rasas, Guarapari, Espírito Santo, 20°40'S, 40°21'W, 17 m, 5 December 2005, R.M. Macieira and J.-C. Joyeux; CIUFES 131797 (1, 36.0), Ilhas Rasas, Guarapari, Espírito Santo, 20°40'S, 40°21'W, 14 August 1989, J.L. Gasparini.

Diagnosis.

A species of Opistognathus with the following combination of characters: anterior nostril a short tube with simple cirrus on posterior rim; maxilla rigid, not produced as a thin flexible lamina posteriorly; supramaxilla absent; subopercle without a broad, fan-like flap; vomer without teeth; body with 43-47 oblique body scale rows in longitudinal series; vertebrae 10+17; sides with two rows of pale spots, each approximately diameter of eye. Body with six vertically irregular, evenly spaced bands, widest on mid-side, and two rows of six pale spots, each spot approximately diameter of eye; buccal area surrounding esophageal opening pale. This species is also easily distinguished from congeners by divergence in the mitochondrial gene COI, as specimens form a monophyletic group that differs from its closest relative ( O. whitehursti ) by an average of 11% (654 bp analyzed).

Description.

Morphometric data are given in Table 4 for the holotype and specimens indicated above by an asterisk; other comparative features are presented in Table 1. Where counts differ, those of the holotype are given first, followed in parentheses by those of the paratypes. Dorsal fin XI, 14. Anal fin II, 13 (II or III [anterior spine minute if III], 12-13, usually II, 13). Pectoral-fin rays 18 (17-18). Vertebrae: 10+17, last pleural rib on vertebra 10, epineurals 12-14. Supraneurals absent. Caudal fin: procurrent rays 4+4 (5 –4+3– 4); segmented rays 8+8, middle 12 branched, total elements 24 (23-25); hypural 5 absent. Gill rakers (number not increasing with increase in SL in adults) 7+16 (7 –8+15–17=23– 25).

Scales absent from head, nape, pectoral-fin base and breast; belly completely scaled, and sides fully scaled except for area above lateral line anteriorly. Body with 46 (43-47) oblique scale rows in longitudinal series. Lateral-line terminus below verticals between segmented dorsal-fin ray 1 (2-3). Anterior lateral-line pores relatively numerous and arranged in branched series along lateral-line tubes, all of which are embedded in skin. Mandibulo-preopercular pore positions all consisting of multiple pore series, except first two mandibular pore positions occupied by simple pores. Infraorbital pore positions consisting of multiple series that extend onto cheeks. Nape nearly to completely covered by sensory pores except for V-shaped naked area immediately in front of dorsal-fin origin (Figure 4B).

Anterior nostril positioned closer to posterior nostril than to dorsal margin of upper lip, and adults with a slender cirrus that reaches anterior margin of orbit when depressed; height of cirrus 2.0 times maximum diameter of posterior nostril. Dorsal fin moderately low anteriorly, with posterior rays slightly longer; profile relatively uniform without noticeable change in fin height at junction of spinous and segmented rays. Dorsal-fin spines stiff and straight and in larger specimens the skin covered tips usually with pale, slightly swollen fleshy tabs. Segmented dorsal- and anal-fin rays all typically branched distally. Outermost segmented pelvic-fin ray not tightly bound to adjacent ray and interradial membrane strongly incised distally; tip of depressed pelvic fin in front of anal-fin origin. Upper margin of subopercle oval-shaped without a broad, truncated flap (Figure 4B) and dorsalmost spine of opercle moderately elongate; posterior margin of preopercle distinct, with a well-developed groove dorsally. No papillae on inner surface of lips. Fifth cranial nerve passes over A1β section of adductor mandibulae muscle.

Upper jaw not sexually dimorphic, extending 0.76 (0.62-0.88) eye diameters behind orbit in specimens 36.0-47.4 mm SL; posterior end of maxilla rigid and truncate, without a thin flexible lamina; supramaxilla absent. Premaxilla with a single row of teeth, largest anteriorly becoming smaller and more closely spaced posteriorly, except in mature males posteriormost three or four teeth stouter and more strongly hooked than adjacent teeth. Dentary anteriorly with two rows of teeth, innermost smaller and slanted backwards; laterally teeth uniserial and larger than anterior teeth, posterior teeth of males larger and more strongly hooked than others. Vomer without teeth. Infraorbital bones tubular, with numerous openings for sensory canals; third infraorbital with a wide suborbital shelf. Postcleithra closely attached; dorsal postcleithrum an irregular elongate oval, narrowest ventrally where it overlaps head of ventral postcleithrum; ventral postcleithrum club-shaped, broadest dorsally and with a pointed ventral end.

Color in life (Figure 8). Background color of head and body brownish to reddish brown. Body with six vertically irregular and evenly spaced dark bands, widest on mid-side, that extend onto base of dorsal fin; two rows of six pale spots on sides, one along dorsal-fin base and the other along anal-fin base, each spot approximately diameter of eye; upper jaw with a wide dark band behind which is a white band at posterior end; the eyes are red; the lips with dark and pale bands; branchiostegal membranes dark; dorsal fin with dark stripe, widest anteriorly, along middle of fin, and a dark blue blotch between the second and fourth spine; pectoral fins are translucent; pelvic fins pale blue to dark or entirely pale; caudal fin with pair basicaudal spots bordered posteriorly by dark continuous band and remainder of fin vertical rows of dark spots or narrow bands.

Preserved color (Figure 9). Body with dark bands and large pale spots as above; other makings various shades of brown. Inner margin of maxilla posteriorly and adjacent membranes with brownish blotch, best developed in males. Buccal area surrounding esophageal opening pale.

Comparisons.

Genetic differences (see discussion in "Phylogenetic relationships of western Atlantic Opistognathus "), suggested that Opistognathus vicinus and the Caribbean O. whitehursti could be separate species despite their very similar appearance, including meristic values and sexually dimorphic premaxillary teeth (see Smith-Vaniz 1997: fig. 33). Initially we considered both species to be only “genovariants” sensu Victor (2015). However, O. vicinus lacks the small supramaxilla (see Smith-Vaniz 1997: fig. 32a) present in O. whitehursti and vomer without teeth (typically one or two teeth present in O. whitehursti ). The color pattern of juveniles of O. whitehursti (Figure 10) is virtually identical to those of adult Brazilian fish. Unlike Opistognathus vicinus , adults of O. whitehursti usually have more reduced body bands (Figure 11) and the spinous dorsal-fin spot is often absent. As noted by Böhlke and Chaplin (1968: 486) for Bahamas fish, "The spot on the spinous dorsal fin is … blue in color in young, frequently missing or poorly defined in adults." Thus, the combined differences in COI, adult coloration, and the lack of a supramaxilla and vomerine teeth support the recognition of O. vicinus as a distinct species. Comparison of the six species of Opistognathus known from the Brazilian Province is given in Table 1.

Etymology.

From the Latin vicinus (near, neighboring), referring to the allopatric distribution and sister-species phylogenetic relationship of the new species and the Caribbean Opistognathus whitehursti .

Distribution and Habitat.

A Brazilian endemic (Figure 6), known from Ceará to Espírito Santo State but absent from oceanic islands. Common in coastal regions, in depths of 10-25 meters, associated with gravel-sand bottoms, near coral reefs and rocky areas. Feeds on small benthic organisms near the bottom (e.g., small shrimps, crabs, and isopods).

Conservation.

The conservation status of this species [cited as Opistognathus whitehursti ( Longley 1927) - unpublished data] has been assessed by the Ministério do Meio Ambiente/Instituto Chico Mendes de Conservação da Biodiversidade (MMA/ICMBio - Brazil), and it was listed as Least Concern.