A new species of Roeboides ( Teleostei : Characidae ) from Costa Rica and Panama , with a key to the middle American species of the genus

A new species of Roeboides is described from the Pacific slope of Costa Rica and Panama. Roeboides bussingi differs from all other Central American Roeboides and all members of the R. guatemalensis species group by the following combination of characters: presence of 18-22 scales above the lateral line (vs. 12-16 in R. dientito); 15-22 scales below the lateral line (vs. 10-14 in R. dientito, and 20-24 in R. loftini); an inconspicuous, sometimes absent, crescent-shaped humeral spot (vs. a large round, conspicuous humeral spot in R. carti, R. dayi, R. dientonito, R. ilseae, R. loftini, and R. occidentalis); a small wedge-shaped spot that does not reach the lateral line (vs. a large spot crossing the lateral line in R. guatemalensis); a teardrop shaped caudal spot (vs. caudal spot triangle shaped in R. bouchellei); and a dark band at the distal tip of the anal fin (vs. dark band absent in R. bouchellei). A key to all Middle American species of Roeboides is also presented.


Introduction
Roeboides Günther, 1864 includes 21 valid species (Eschmeyer, 2012).The genus has a wide distribution ranging from río Perros at Ixtepec in southern Mexico (Miller et al., 2005) to the la Plata basin in northern Argentina (Lucena, 2007).Members of Roeboides are best known for their habit of tearing off and ingesting scales from other fishes (lepidophagy), which is presumably aided by conspicuous teeth on the external margin of the jaws (Hahn et al., 2000).The genus has its greatest species richness in South America (15 species), whereas in Central America only seven valid species are known, including the recently described Roeboides loftini Lucena, 2011.Six of these species are restricted to Lower Middle America (Costa Rica and Panama).Roeboides bouchellei is the only Middle American species with a large distributional range, extending from Panama to Southern Mexico (Miller et al., 2005).Notably one third of all species of Roeboides have been described in the last decade.Lucena (1998) proposed that the species of Roeboides could be organized into four groups: the R. dispar group, the R. guatemalensis group, the R. microlepis group, and the R. affinis group.Those groups of species are defined by unique osteological synapomorphies (particularly of the jaws) as well as meristic traits (Lucena, 2000(Lucena, , 2003(Lucena, , 2007(Lucena, , 2011)).All species of Roeboides from Central America (viz., R. bouchellei, R. carti, R. dayi, R. guatemalensis, R. ilseae, R. loftini, and R. occidentalis) belong to the R. guatemalensis group.Roeboides dientonito, from Guyana and Venezuela, is the only member of the R. guatemalensis group not found in Central America (Lucena, 2007).
According to Bussing (1998), a preliminary molecular analysis provided evidence that an unidentified species of Roeboides from Costa Rica and Panama was distinct from other valid species of the genus.Bussing (1998) also noted that morphological evidence in favor of that distinction was lacking at the time.In January and April 2011, additional specimens of that species were collected from several localities in Costa Rica and Panama (Fig. 1).That new species of Roeboides is described herein, and a key to Middle American species of the genus is provided.

Material and Methods
Specimens examined are deposited in the Louisiana State University Museum of Natural Science (LSUMZ), Museo de Zoología, Universidad de Costa Rica (UCR), Florida Museum of Natural History (UF), and Tulane University (TU).Morphometric measurements were taken for 17 distances in 29 specimens of the species described herein.Comparative information on other valid species of Roeboides was obtained from Bussing (1985), Lucena (2000) and Lucena (2011) and from specimens listed in the Comparative Material.Measurements were taken following Fink & Weitzman (1974).Measurements were recorded to the nearest 0.1 mm using dial calipers, and include: standard length (SL), head length (HL), orbit diameter, snout length, maxillary length, bony interorbital length, greatest body depth, caudal peduncle depth, caudal peduncle length, predorsal distance, pre-anal distance, pre-pectoral distance, prepelvic distance, height of the dorsal fin, height of the anal fin, pectoral-fin length, and pelvic-fin length.Morphometric measurements are presented as percentages of SL.Meristic counts include: anal-fin rays, pectoral-fin rays, pelvic-fin rays, caudal-fin rays, lateral line scales, scales above lateral line, scales below lateral line, and scales around caudal peduncle.Paratypes.Costa Rica: LSUMZ 14629, 6, 54.4-63.7   Diagnosis.Roeboides bussingi differs from all other members of the R. guatemalensis group by the following combination of characters: the presence of 18-22 scales above lateral line (vs.12-16 in R. dientito), 15-22 scales below lateral line (vs.10-14 in R. dientito, and 20-24 in R. loftini), a small inconspicuous, sometimes absent, crescent-shaped humeral spot (vs. a large round, conspicuous humeral spot in R. carti, R. dayi, R. dientonito, R. ilseae, R. loftini, and R. occidentalis), and the presence of a small wedge-shaped spot that does not reach the lateral line (vs.a large spot crossing the lateral line in R. guatemalensis).Roeboides bussingi and R. bouchellei share a similar humeral spot, and both lack a wedge-shaped spot on the lateral line between the dorsal and anal fins.However, R. bussingi can be distinguished from R. bouchellei by an overall darker body coloration with many scattered melanophores (vs. a lighter colored body with few melanophores; most evident in preserved specimens and consistent across genders), by a dark band of melanophores at the distal tip of the anal fin (vs.distal band absent; melanophores scattered throughout anal fin; Fig. 3a and b), a darker, more developed teardrop shaped caudal spot with the rounded bulbous posterior end on the caudal fin (vs. a lighter, less developed triangular spot typically restricted to the caudal peduncle; Fig. 3c and d), and a lighter lateral band (vs. a darker, more developed lateral band; most evident in preserved specimens).

Roeboides bussingi, new species
Description.Morphometric and meristic data for type specimens are summarized in Table 1.Roeboides bussingi is a laterally compressed characin with a strongly concave nape and a convex, hump-shaped nuchal region.Greatest body depth between dorsal-and anal-fin origins.Post-dorsal profile straight, angling ventrally from the dorsal-fin origin to caudalfin origin.Pre-anal profile rounded from tip of snout to analfin origin, post-anal profile straight along the anal fin, angling ventrally at the caudal peduncle.
Mouth terminal with strongly inclined gape.Upper jaw protrudes over lower jaw.Maxilla reaches slightly past vertical through midline of pupil.Premaxilla and dentary with unicuspid mammiliform teeth exposed on outer margin of lips.Largest mammiliform teeth larger than internal buccal teeth.Two large mammiliform teeth projecting from anterior margin of upper lip.Two small mammiliform teeth on the dentary directly below those on the margin of the upper lip.Buccal teeth unicuspid and conical, in single irregular row on both jaws (tooth morphology identical to other species of the R. guatemalensis group).Dorsal-fin origin slightly posterior to vertical through anal-fin origin.Pelvic-fin rays extending beyond anal-fin origin.Pectoral-fin rays not reaching origin of anal fin.Small bony hooks present in the segmented rays of the anal fin, as described by Lucena (2011) for R. loftini.

Color in life.
Overall coloration silvery (transparent where scales are absent), with a greenish-silvery lateral band.All fins yellow to orange.Distal tips of anal and caudal fins with dusky distal margins.Conspicuous dark teardrop-Fig.2. Photographs of (a) Roeboides bussingi (LSUMZ 14629; 69.2 mm SL) depicting live coloration, and (b) preserved holotype (LSUMZ 14799; 74.9 mm SL).shaped spot on caudal peduncle that extends to the caudal fin (rounded end on caudal fin).Dark, crescent-shaped humeral spot present (Fig. 2a), inconspicuous or absent in some specimens.
Color in alcohol.Ground color yellowish-tan.Dorsal head and flank with melanophores loosely dispersed but more concentrated than below lateral line.Dark gray mid-lateral band extending from anterior margin of opercle to black teardropshaped spot on caudal peduncle and base of middle rays of the caudal fin.Humeral spot dark brown, crescent-shaped when present.Dorsal and caudal fins whitish to transparent and with dusky distal margins, anal fin with concentrated melanophores at distal margin.Paired fins opaque (Fig. 2b, 3a).
Distribution.Roeboides bussingi is known from the Pacific slope of Costa Rica and Panama, including tributaries of the río Coto drainage in Costa Rica to the río San Pablo west of the city of David in western Panama (Fig. 1).
Etymology.The species is named after William Bussing, an exceptional ichthyologist who has devoted his professional career to the understanding of the Costa Rican and Central American ichthyofauna.He was the first to suggest that the species described herein was new to science (Bussing, 1998).

Remarks.
A reduced or absent humeral spot clearly distinguishes R. bussingi from all other Lower Middle American species of Roeboides with the exception of R. bouchellei, which is nevertheless distinct from R. bussingi in terms of color pattern.Examination of more than 300 specimens of R. bouchellei revealed that the differences in coloration described in the diagnosis of R. bussingi are consistent, strongly indicating that the species are distinct.In addition, Bermingham et al. (1997) concluded that specimens of Roeboides from the río Coto and Western Panama are genetically distinct from other R. bouchellei.That might be interpreted as additional circumstantial evidence for the distinction of R. bussingi among congeners, given that R. bussingi is the only species of the genus known to occur in the río Coto.

Fig. 3 .
Fig. 3. (a) Anterior portion of the anal fin of Roeboides bussingi (LSUMZ 14797, 79.0 mm SL; paratype) showing concentration of melanophores forming a dark band at the edge of the fin.(b) Same region of anal fin of R. bouchellei (LSUMZ 14798, 72.2 mm SL) showing scattered melanophores, without a distinctive dark band.(c) Caudal region of R. bussingi showing the teardrop-shaped spot that extends onto the caudal fin.(d) Caudal region of R. bouchellei showing a lighter and triangleshaped spot, largely restricted to the caudal peduncle.Also note the densely distributed melanophores on the body of R. bussingi and the lighter body coloration and fewer melanophores in R. bouchellei.

Table 1 .
Morphometric and meristic data of holotype (H) and paratypes (n =28) of Roeboides bussingi.Holotype is not included in the range, mean and standard deviation (SD).