Revision of the species of the genus Cathorops ( Siluriformes : Ariidae ) from Mesoamerica and the Central American Caribbean , with description of three new species

The ariid genus Cathorops includes species that occur mainly in estuarine and freshwater habitats of the eastern and western coasts of southern Mexico, Central and South America. The species of Cathorops from the Mesoamerica (Atlantic slope) and Caribbean Central America are revised, and three new species are described: C. belizensis from mangrove areas in Belize; C. higuchii from shallow coastal areas and coastal rivers in the Central American Caribbean, from Honduras to Panama; and C. kailolae from río Usumacinta and lago Izabal basins in Mexico and Guatemala. Additionally, C. aguadulce, from the río Papaloapan basin in Mexico, and C. melanopus from the río Motagua basin in Guatemala and Honduras, are redescribed and their geographic distributions are revised.


Introduction
Ariid catfishes are widely distributed in tropical and temperate continental shelves all over the world, mainly inhabiting coastal waters and estuarine regions, or in some cases confined to freshwaters (Kailola, 2004;Marceniuk & Menezes, 2007).The neotropical genus Cathorops Jordan & Gilbert, 1882 includes species that occur mainly in estuarine and freshwater habitats in the eastern and western shelves of southern Mexico, Central and South America.The species belonging to Cathorops have been traditionally distinguished by the absence of vomerine tooth plates and presence of one pair of small oval accessory tooth plates bearing molariform teeth.The genus comprises 14 valid species (Marceniuk & Ferraris, 2003;Betancur-R. & Acero P., 2005;Marceniuk, 2007a), although a higher number of species has been recognized, but not named by Marceniuk (1997).Monophyly of the genus was first recognized by Marceniuk (1997) and later confirmed through cladistic analyses by Marceniuk (2003), using osteological characters and Betancur-R.(2003), Betancur-skin.Dorsomedian groove of neurocranium formed by frontals and supraoccipital, relatively deep and long, its margins well marked and progressively narrower posteriorly.Supraoccipital process relatively long and narrow on posterior portion, profile straight.Nuchal plate crescent-shaped, short and relatively wide.Snout long, rounded on transverse section.Anterior and posterior nostrils close to one another.Eye lateral and large.Interorbital distance short, distance between nostrils and orbit long.Maxillary barbel surpassing base of pectoral-fin spine, external mental barbel surpassing margin of gill membrane, internal mental barbel reaching margin of gill membrane.
Mouth narrows, lower jaw arched.Lips thick, lower lip thicker than upper lip.Vomerine tooth plates absent.One pair of elongated and narrow accessory tooth plates, small and distant from each other.Accessory tooth plates with small and few molariform teeth.Premaxilla quite narrow and moderately long.
Soft pectoral-fin rays 10.Pectoral-fin spine thick and short; anterior margin without granules or serrations; posterior margin with long and conspicuous serrations along almost its entire length.Soft dorsal-fin rays 7. Dorsal-fin spine relatively short, longer than pectoral-fin spine; anterior margin smooth; posterior margin serrated along almost its entire length.Pelvic fin high, with 6 rays.Anal fin high and short at base, with 21 rays.Upper and lower lobes of caudal fin long, upper lobe longer than lower lobe.Caudal peduncle high.
Coloration in Alcohol.Dorsal and lateral portions of head brown, ventrally light beige.Body with same brown color, progressively lighter towards lateral line and rather light beige under lateral line.Maxillary barbel dark, mental barbels light; adipose fin dark, and other fins brown.
Sexual dimorphism.Sex of specimens was not examined (see Material and Methods).Description.(Tables 1 and 2).Head long and depressed, profile slightly convex at level of frontals and supraoccipital.Body broader rather than deeper on pectoral girdle area.Cephalic shield rugose, relatively short and narrow on lateral ethmoid, frontal, supracleithrum, and epioccipital areas.Osseous bridge formed by lateral ethmoid and frontal long and slender, evident under Distribution.Cathorops aguadulce was described based on material from río Tesechoacán, río Papaloapan basin in Veracruz, Mexico.Without considering the populations from the río Usumacinta/río Grijalva and río Polochic/Lago Izabal watersheds (see remarks), Miller et al. (2005, Map 6.144) suggested that C. aguadulce occurs from río Coatzacoalcos northwestwards to río Panuco as well as in the Gulf of Mexico (Fig. 6).The species inhabits large to medium-sized rivers, lagoons and small drainages; typically freshwaters, but also occurring in marine waters (Miller et al., 2005).

Coloration in Alcohol.
Head dark brown on dorsal and lateral portions, ventrally light cream.Body with same dark brown coloration on dorsal portion, progressively lighter towards lateral line and light cream under lateral line.Barbels light, fins light beige.
Sexual dimorphism.Sexual dimorphism was observed in two females (175.0-240.0mm SL) and seven males (147.0-211.0mm SL) with respect to following morphological features (see also Table 3).Males with relatively larger heads than females, as evidenced by greater distance between lateral cornu of lateral eth- Distribution.Cathorops belizensis is described from the mangrove channels near St. John´s College at Belize city, Belize (Fig. 11).
Etymology.The specific epithet belizensis derives from the type locality of the species, Belize City.
Vernacular names.Belizean Sea Catfish or bagre de Belize.moid and external limb of supracleithrum, greater interorbital distance, and wider cephalic shield on lateral ethmoids and frontal areas.Anterior portion of body longer in males than in females, as evidenced by distance from tip of snout to pectoral, dorsal and adipose fins and by longer distance from tip of snout to posterior margin of dorsomedian groove of neurocranium.Males with deeper and wider body than females.

Cathorops (Cathorops) higuchii, new species
Premaxilla wider in males than in females (Fig. 10).Accessory tooth plates remarkably longer and wider in females and consequently more distant from one another in males (Fig. 10).Males with smaller and fewer molariform teeth on accessory tooth plates than females.Accessory tooth plates totally or partially covered by epithelial tissue in males.Dentary in females with longer posterior projection and larger and with more molariform teeth on its posterior portion than males (Fig. 10).

Coloration in alcohol.
Head medium to light brown on dorsal and lateral portions, ventrally light beige.Body with same brown coloration on dorsal portion, progressively lighter towards lateral line and light beige under lateral line.Maxillary barbel dark, mental barbels lighter, fins dark beige.
Sexual Dimorphism.Sexual dimorphism was observed in eleven females (97.0-192.0mm SL) and ten males (125.0-163.0mm SL), with respect to the following morphological features (Table 4).Head relatively longer in males than in females, as evidenced by greater distances from tip of snout to pectoral-, dorsal-and anal- fin origins, and greater distance from tip of snout to posterior margin of dorsomedian groove of neurocranium.Premaxilla broader in males than in females (Fig. 15).Accessory tooth plates longer and broader in females than in males (Fig. 15); plates covered by epithelial tissue, more distant from one another, and containing fewer and smaller molariform teeth in males.Posterior expansion of dentary longer and with more molariform teeth in females than in males (Fig. 15).Females with longer pelvic fin and higher anal fin than males.
Distribution.The species is common along most of the Caribbean portion of Central America, from Honduras to Panama (Fig. 11).Cathorops higuchii inhabits shallow coastal areas and low portions of coastal rivers Etymology.This species is named on behalf of Dr. Horácio Higuchi, of Museu Paraense Emílio Goeldi, in recognition for his contribution to the taxonomy, systematics, and morphology of the South American Ariidae.
Vernacular names.Higuchi's Sea Catfish or bagre de Higuchi.

Description. (Tables
Mouth small, lower jaw arched.Lips thick, lower lip thicker than upper lip.Vomerine tooth plates absent.One pair of accessory tooth plates, elongated and narrow, quite small and distant from each other.Accessory tooth plates with small and not numerous molariform teeth.Premaxilla relatively short and quite narrow.Dentary with no so pronounced posterior projection, with many sharp teeth on anterior portion and few small molariform teeth on posterior portion. Soft pectoral-fin rays 9-10 (10).Pectoral-fin spine long and thick; anterior margin with few granules on basal two thirds, distal third with short serrations; posterior margin with straight basal fourth, distal three quarters with long and conspicuous serrations.Soft dorsal-fin rays 7. Dorsal-fin spine longer than pectoral-fin spine; anterior margin with few granules on basal two thirds, distal third with short serrations; posterior margin serrated along almost its entire length.Pelvic fin high, with 6 rays.Anal fin high and relatively short at base, with 20-24 (22) rays.Upper and lower lobes of caudal fin long, upper lobe longer than lower lobe.Caudal peduncle relatively low.
Acicular gill rakers on first arch 14-16 ( 14), 4 or 5 (5) on upper limb, 9 to 11(9) on lower limb.Spike shaped gill rakers on second arch 13-16 (13), 4 or 5 (4) on upper limb, 9 to 11 (9) on lower limb.Mesial surfaces of all gill arches with developed gill rakers.Lateral and mesial surfaces of first and second gill arches with fleshy papillae intercalated with gill rakers, papillae more developed on second arch.Distribution.Material examined of Cathorops kailolae comes from the lago Izabal basin in Guatemala (type locality) and the río Usumacinta basin in Mexico and Guatemala (Fig. 6).Because the main arm of the río Usumacinta flows into the río Grijalva near its mouth, the population reported by Miller et al. (2005, Map 6.144) from the río Grijalva is probably conspecific with C. kailolae, but this requires confirmation.This species inhabits chiefly freshwaters, but apparently also present in high salinities, as in laguna de Términos (Miller et al., 2005).
Etymology.The species is name to honor Dr. Patricia J. Kailola, The University of the South Pacific, Suva, Fiji, for her enormous contribution to the systematics of the Ariidae.
Remarks.Despite the fact that the lago Izabal and the río Usumacinta basins are presently isolated, no important meristic or morphometric differences were observed between the populations from these two localities at this time.Type specimens were restricted to the lago Izabal basin because future studies (e.g.phylogeographic approaches) might reveal some differences between the two populations.Cathorops kailolae is closely related to C. aguadulce (see remarks of C. aguadulce).(Günther, 1864) Figs  20).

Description. (Tables
Mouth relatively small, lower jaw arched.Lips relatively thick.Vomerine tooth plates absent.One pair of small, narrow and elongated accessory tooth plates, quite distant from one another.Accessory tooth plates with small molariform teeth.Premaxilla quite narrow and long.Dentary with not so pronounced posterior projection, with many sharp teeth on anterior portion and few small molariform teeth on posterior portion. Soft pectoral-fin rays 10.Pectoral-fin spine short; anterior margin with few granules on basal two thirds, distal third with  Distribution.Material examined is from the río Motagua in Guatemala, type locality of the species (Fig. 6).Probably present in the Honduran portion of the río Motagua, near its mouth.The species is restricted to freshwaters.Vernacular names.Dark Sea Catfish, bagre prieto.

Discussion
The genus Cathorops can be diagnosed from other New World ariid genera by having accessory tooth plates small and oval (vs.large, round to subtriangular in Amphiarius and some Notarius and Sciades, longitudinally elongated in Aspistor, Occidentarius, some Notarius and Sciades or absent in Potamarius), dentary with posterior expansion in females (vs.dentary without posterior expansion in other ariid genera with exception of Potamarius), extrascapular subtriangular, contacting the supraoccipital through a suture parallel to the longitudinal axis (vs.extrascapular subrectangular or subquadrangular with oblique suture in other genera), base of adipose fin quite short, less than one-half the length of anal-fin base (vs.about half as long as anal-fin base in Genidens, Notarius, Potamarius and Sciades or as long as anal-fin base in Amphiarius, Aspistor, and Galeichthys), and lateral line not bifurcated at caudal region, reaching base of caudal-fin upper lobe (vs.bifurcated at caudal region, reaching base of caudal-fin upper and lower lobes in Bagre).The subgenus Cathorops, within which the species described here are included, can be diagnosed from the subgenus Precathorops and from other ariid genera by possessing a lateral ethmoid and frontal limiting a wide conspicuous fenestra, visible under the skin (vs.moderately developed in Precathorops, Amphiarius, Aspistor, Bagre, Galeichthys, Notarius, and Potamarius or reduced or absent in Genidens, Sciades, and Occidentarius), mesethmoid, lateral ethmoid and frontal lacking bony spinulations (vs.bony spinulations present in Precathorops), posterior cranial fontanel very reduced (vs.moderately developed, long and narrow in Precathorops, Notarius, and Potamarius, large and long in Amphiarius and Aspistor, or absent in Sciades), vomerine tooth plates absent (vs.present in Precathorops, Aspistor, Bagre, Galeichthys, Notarius, Occidentarius, and Sciades), accessory tooth plates bearing molariform teeth (vs.conical in Precathorops, and in other ariid genera except Aspistor), posterior cleithral process short (vs.moderate length in Precathorops and other ariid genera), and mesial gill rakers on first two arches developed (vs.absent or reduced in Precathorops, Amphiarius, Aspistor, Bagre, Notarius, Occidentarius, and Sciades).& Acero P., 2006).Both species are unambiguously distinguished from one another by mitochondrial characters, but the best morphological discriminators (e.g.anterior internarial distance in maxillary barbel length, gill raker counts on first and second arches) have some degree of overlapping.Both entities are thus referred as the C. mapale species complex (Colombian Caribbean and Venezuela; Betancur-R.& Acero P., 2006).Based on the morphology, distribution, and habitat preferences of the new Caribbean species described here (C.higuchii and C. belizensis), it would be expected that they are included within the C. mapale/C.fuerthii clade, but this requires confirmation.The molecular phylogenies also recovered the freshwater C. aguadulce complex sister to a clade including four Eastern Pacific species (C. taylori, C. steindachneri, C. hypophthalmus, and C. tuyra).The pyhlogenetic position of C. melanopus is still uncertain and needs further investigation.
Ariids are known for their peculiar reproductive habits (i.e.male mouthbrooding) (Rimmer & Merrick, 1982;Acero P. et al., 2005;Wang, et al., 2005) associated with striking morphological differences between males and females.Females have pelvic fins that are longer and wider at base than males and distally rounded (Gudger, 1916;Lee, 1931Lee, , 1937;;Merriman, 1940;Whitley, 1941), and during the spawning season the inner pelvic-fin rays become hook-like (Mane, 1929;Lee, 1931).Likewise, during the incubation period, males enlarge the branchial chamber, reduce the number of teeth, and modify the epithelium that covers the oral cavity (Gudger, 1916;Dimitrenko, 1970).All these differences are observed in the species of Cathorops, which have additional modifications not found in other ariid species, such as head larger and wider in males than in females (Marceniuk, 1997;2007a;2007b).These differences may be associated with the smaller body sizes, on average, attained by the species of Cathorops.Considered r-strategists, ariid species reach gonadal maturity at relatively old ages and large sizes, but in Cathorops the values for these traits are lower (Etchevers, 1978;Mishima & Tangi, 1983;Mello & Teixeira, 1992).Consequently, additional dimorphic features associated to head size in males of Cathorops, could represent an adaptation to compensate for the smaller body lengths, allowing a relative increase of the branchial chamber.The conspicuous dimorphism of Cathorops has caused misidentifications and synonym descriptions in the literature.For instance, Valenciennes (1840) based the description of Arius arenatus and A. fissus on generalized features within the Ariidae, considering that A. arenatus (= Cathorops arenatus) could be

Fig. 6 .
Fig. 6.Distribution of freshwater species of Cathorops in Mesoamerica.C. aguadulce [open square, holotype; filled square, non-types; hatched square, from Miller et al. (2005, Map 6.144)]; C. kailolae [open circle, holotype; filled circle, paratypes; gray circle, non-types; hatched circle, from Miller et al. (2005, Map 6.144)], and Cathorops melanopus (triangle).Some symbols represent more than one locality or lot of specimens (from www.aquarius.geomar.de).underskin.Dorsomedian groove of neurocranium formed by frontals and supraoccipital deep and relatively large, its margins well marked and progressively narrower posteriorly.Supraoccipital process relatively short and wide on posterior portion, profile straight.Nuchal plate crescent-shaped, short and wide.Snout long and rounded on transverse section.Anterior and posterior nostrils quite distant from one another.Eyes lateral and small.Interorbital distance long, distance between nostrils and orbit moderate.Maxillary barbel reaching base of pectoralfin spine, external mental barbel reaching margin of gill membrane, internal mental barbel not reaching margin of gill membrane.Mouth broad, lower jaw arched.Lips wide, lower lip thicker

Fig. 11 .
Fig. 11.Distribution of marine and estuarine species of Cathorops in the Central American Caribbean.Cathorops belizensis (triangle) andC.higuchii (open square, holotype and some paratypes; filled square, other paratypes).Some symbols represent more than one locality or lot of specimens (from www.aquarius.geomar.de).
Betancur-R. & Acero (2005)  andBetancur-R.et al. (2007)   hypothesized the relationships of 13 species of Cathorops based on mitochondrial sequences (ATP synthase 8/6, cytochrome b, 12S, and 16S, total 2842 bp).The marine and brackish entities occurring from Belize to Brazil were formerly treated as C. spixii (e.g.Taylor & Menezes, 1978), described from equatorial Brazil.Betancur-R.& Acero (2005) demonstrated that C. mapale, described from the southern and central coasts of the Colombian Caribbean, is more closely related to the C. fuerthii group from the Eastern Pacific than to the C. spixii clade (including C. spixii, C. agassizii, and probably C. arenatus), which is restricted from Brazil and the Guyanas.The entity distributed between northern Colombian and Venezuela has been recently hypothesized to be the sister species of C. mapale based on mitochondrial grounds (Betancur-R.

Table 2 .
Morphometrics for Cathorops aguadulce.Standard length is expressed in millimeters, other measurements are percents of standard length.Ranges include paratypes only.
Diagnosis.Cathorops belizensis is distinguished from all congeners by having 19-20 gill rakers on first arch (vs.14-16 in C. aguadulce, 14-15 in C. fuerthii, 37-40 in C. hypophthalmus, 14than upper lip.Vomerine tooth plates absent.One pair of oval shaped accessory tooth plates, moderate in size and distant from one another.Accessory tooth plates with large molariform teeth.Premaxilla broad and short.Dentary with well pronounced posterior projection, with sharp teeth on anterior portion, molariform teeth on posterior portion and few conical teeth on intermediate portion.

Table 3 .
Morphometrics for Cathorops belizensis.Standard length is expressed in millimeters, other measurements are percents of standard length.Ranges include paratypes only.

Table 4 .
Morphometrics for Cathorops higuchii.Standard length is expressed in millimeters, other measurements are percents of standard length.Ranges include paratypes only.

Table 6 .
Morphometrics for Cathorops melanopus.Standard length is expressed in millimeters, other measurements are percents of standard length.shortserrations;posteriormarginstraight on basal fourth, distal three quarters with long serrations.Soft dorsal-fin rays 7. Dorsalfin spine short, as long as pectoral-fin spine; anterior margin with granules on basal two thirds, distal third with short serrations; posterior margin serrated for almost its entire length.Pelvic fin high, with 6 rays.Anal fin high and long at base, with19-20 (19)rays.Upper and lower lobes of caudal fin of moderate length, upper lobe longer than lower lobe.Caudal peduncle high.Acicular gill rakers on first arch 16-18 (17), 5 or 6 (5) on upper limb, 11 or 12 (11) on lower limb.Spike shaped gill rakers on second arch 16-18, 4 to 6 on upper limb, 12 or 13 on lower limb.Mesial surfaces of all gill arches with developed gill rakers.Lateral and mesial surfaces of first and second gill arches without fleshy papillae intercalated with gill rakers.Dorsal and lateral portions of head dark, ventrally light beige.Body with same dark color, progressively lighter towards lateral line and rather light beige under lateral line.Maxillary barbel dark, mental barbels light, fins dark especially towards edge.