Ariopsis seemanni ( Günther, 1864 ), Gunther, 1864

Marceniuk, Alexandre P., Acero, Arturo, Cooke, Richard & Betancur-R, Ricardo, 2017, Taxonomic revision of the New World genus Ariopsis Gill (Siluriformes: Ariidae), with description of two new species, Zootaxa 4290 (1), pp. 1-42 : 31-35

Ariopsis seemanni ( Günther, 1864)

Congo Prieto or Musengue (Spanish, Panama) Figures 18 and 19 , Tables 2–4 and 11.

Arius seemanni Günther, 1864:147 . Type locality: Central America (Pacific). Holotype (unique): BMNH 1855.9 .19.1107. Tachisurus jordani Eigenmann & Eigenmann, 1888:142 . Type locality: Panama (Pacific) . Syntypes: MCZ 4945 (2). Galeichthys eigenmanni Gilbert & Starks, 1904:21 , Pl. 4, fig. 8. Type locality: Panama . Holotype: CAS-SU 6986. Paratypes:

(11) BMNH 1903.5.15.319–320; CAS-SU 12878–80 (1, 1, 1); USNM 50379 (1); ZMB 15858 [ex USNM] (2). Arius seemanni, Kailola & Bussing, 1995: 874 .

Ariopsis seemanni, Robertson & Allen, 2015 .

Material examined. Holotype: BMNH 1855.9.19.1107 (1, 227 mm SL). Non-type specimens: MCZ 4945 (2, 198– 201 mm SL), Panama ; STRI 15948 (1, 178 mm SL), El Salvador, Acajutla ; STRI 12668 (1, 171 mm SL), Panama, bahía de Parita ; STRI 12667 (1, 177 mm SL), Panama, Bahía de Parita ; STRI 17240 (1, 314 mm SL), Panama, isla Majagual ; STRI 17241 (2, 155– 219 mm SL), Panama, Isla Majagual ; STRI 9297 (1, 204 mm SL), Panama, Punta Chame outer beach and inside lagoon ; STRI 16754 (1, 153 mm SL), Panama, Bahía de Panama, isla Naos ; STRI 3071 (1, 145 mm SL), Panama, Veracruz Beach ; FMNH 19791 (2, 226– 285 mm SL), Panama, Chame Point.

Diagnosis. Ariopsis seemanni can be differentiated from its congeners as follows: from A. assimilis , from Mexico (Quintana Roo) to Honduras (Caribbean), by the presence of an osseous medial groove (vs. absent; Figs. 3 and 19 ), lateral margin of sphenotic notched, narrower medially than anteriorly (vs. straight, as wide medially as anteriorly, Figs. 3 and 19 ); from A. canteri , from the Colombian Caribbean, by the presence of an osseous medial groove (vs. absent; Figs. 3 and 19 ), lateral margin of sphenotic notched, narrower medially than anteriorly (vs. straight, as wide medially as anteriorly, Figs. 3 and 19 ); from A. felis , from Massachusetts ( US) to Yucatán in Mexico (Caribbean), by its fleshy medial groove of neurocranium, never surpassing posterior margin of eyes (vs. very long, always surpassing the posterior margin of eyes, Figs. 4 and 19 ), pterotic lateral margin convex, sometimes angled (vs. smoothly convex, Figs. 3 and 19 ); from A. gilberti , from Mexico (EP), by the presence of 30–36 gill rakers on the first and second gill arches (combined counts; vs. 40–42), fleshy medial groove of neurocranium conspicuous or inconspicuous, but never surpassing posterior margin of eyes (vs. conspicuous and very long, always surpassing the posterior margin of eyes, Figs. 3 and 19 ); from A. guatemalensis , from Mexico to Costa Rica (EP), by its narrower mouth 9.7–12.7% SL (vs. 13.0–15.2% SL), osseous medial groove present (vs. absent; Figs. 3 and 19 ), lateral margin of sphenotic notched, narrower medially than anteriorly (vs. straight, as wide medially as anteriorly, Figs. 3 and 19 ), median portion of mesethmoid narrow (vs. wide, Fig. 3 ), medial notch of mesethmoid narrow and deep (vs. large and shallow, Fig. 3 ); from A. jimenezi , from Archipiélago de Las Perlas in Panama (EP), by its fleshy medial groove of neurocranium, conspicuous or inconspicuous, but never surpassing posterior margin of eyes (vs. conspicuous and very long, always surpassing the posterior margin of eyes, Figs. 4 and 19 ), pterotic lateral margin markedly convex, sometimes angled (vs. smoothly convex, Figs. 3 and 19 ), external posterior branch of lateral ethmoid columnar and thin (vs. depressed and thick, Fig. 3 ), fenestra delimited by mesethmoid and lateral ethmoid conspicuous (vs. inconspicuous, Fig. 3 ); from A. simonsi , from Colombia to Peru (EP), by its notched lateral margin of sphenotic, narrower medially than anteriorly (vs. straight, as wide medially as anteriorly, Figs. 3 and 19 ).

Description. Morphometrics and meristics summarized in Table 2–4, 11. Head moderately long, wide and high, especially depressed at lateral ethmoid and frontal area, profile slightly elevated posteriorly, straight from mesethmoid to parietosupraoccipital. Snout rounded and moderately long. Anterior nostril rounded, with fleshy edge, posterior nostril covered by flap of skin, moderately separated and moderately distant from orbit, not connected by fleshy furrow. Eye lateral, moderately large and distant to one another. Three pairs of long teretiform barbels; maxillary barbel surpassing or not membranous portion of operculum, lateral and mesial mental barbel not reaching posterior margin of gill membrane. Osseous bridge formed by lateral ethmoid and frontal moderately long and slender, delimiting a fenestra little evident under the skin. Cephalic shield exposed, moderately long and moderately wide on supracleithrum, lateral ethmoid and frontal areas, with thick granulation, forming distinct patterns from eyes to parietosupraoccipital procces. Fleshy portion of dorsomedial groove of neurocranium, affixed to anterior cranial fontanel, moderately long and conspicuoust, not surpassing eyes. Lateral margin of sphenotic notched, narrower medially than anteriorly. Pterotic lateral margin convex, sometimes angled. Parietosupraoccipital keeled, triangular, with straight lateral margins converging posteriorly, relatively short and moderately wide at posterior portion, with posterior margin convex. Nuchal plate crescent–shaped, conspicuously granulated dorsally, moderately long and narrow. Mouth subterminal, moderately large, with lips moderately thick and lower jaw arched. Vomerine tooth plates rounded. One pair of accessory tooth plates ovate, with sharp teeth. Premaxilla rectangular transversally, long and wide, with sharp teeth. Dentary with eyebrow-shaped patch of teeth, separated at midline with sharp teeth. Gill membranes fused, attached to isthmus. Fifteen to 18 acicular gill rakers on first arch, 15–18 spike-shaped gill rakers on second arch and rakers present on posterior margin of all gill arches.

Caudal-fin lower lobe length 2 29.4 29.1–29.7 Body wider than its height at pectoral girdle area, progressively compressed from pectoral to caudal peduncle, ventrally flattened from pectoral girdle to anal origin. Lateral line sloping ventrally on anterior one-third, extending posteriorly to caudal peduncle, bending abruptly onto dorsal lobe of caudal. Dorsal fin spine relatively short and thick, almost as long as pectoral-fin spine; anterior margin granulated on basal two-thirds, with weak serrations on distal third; posterior margin smooth on basal third, distal third with weak serrations. Seven dorsal fin soft rays.

Pectoral fin spine moderately long and thick; two-thirds of anterior margin weakly granulated, with weak serrations on distal third; posterior margin straight on basal one-fourth, distal three-fourths with serrations. Nine to ten pectoral fin soft rays. Posterior process of cleithrum triangular, smooth to rugose, slightly visible. Pelvic fin deep and large at base, with six rays, and well-developed fleshy protuberances in adult females. Adipose fin low, with base moderately long, shorter than anal base. Anal fin moderately high and long at base, with 18–20 rays and ventral profile convex. Caudal peduncle moderately high. Caudal-fin forked, dorsal and ventral lobes moderately long, dorsal lobe somewhat longer than ventral lobe and pointed.

Maximum length: May exceed 350 mm Tl.

Coloration in alcohol. Head and body dark brown to bluish above, whitish below; dorsal surfaces of pelvic proximally black, distally lighter; anal dark, distal tips lighter; caudal grayish to blackish ( Fig. 18 ).

Sexual dimorphism. Only females have well-developed fleshy protuberances or pads in basal portion of pelvics, especially during reproductive season. Vomerine tooth patches and accessory tooth patches not observed directly, but possibly showing same variation described for A. canteri and A. jimenezi .

Distribution and habitat. Ariopsis seemanni occurs in estuarine and marine waters, from El Salvador to Panama (EP) ( Fig. 5 ). In Panama, it is abundant in tidal rivers and high salinity salt pans, but has not been recorded from freshwaters.

Molecular evidence and phylogenetic relationships. Our phylogenetic analyses failed to support the monophyly Ariopsis seemanni , suggesting the existence of a species complex segregated by geography ( Fig. 9 ). Examined specimens from Panama and El Salvador are not each other’s closest relatives. Instead, the specimen from El Salvador appears to be closer to the new Caribbean species, A. canteri .

Remarks. Arius seemanni was described by Günther (1864), based on a single specimen collected in Pacific coast of Central America ( Figs. 18 and 19 ). The original description recognizes Ariopsis seemanni based on morphometric, meristic and osteological characteristics that are clearly also present in other species in the genus (i.e., are not diagnostic). Here, A. seemanni is tentatively delimited based on a combination of morphometric, meristic, and osteological characters. The molecular evidence, however, failed to resolve the species as monophyletic (see above). The apparent absence of conspicuous or unique features in A. seemanni may also explain the difficulties faced by previous ichthyologists in delimiting this species. In fact, most nominal species in the tropical EP (except for Ariopsis guatemalensis ) have at times been subsumed in synonymy under A. seemanni . Galeichthys eigenmanni from Panama, described by Gilbert & Starks (1904), is confirmed as a junior synonym of A. seemanni ( sensu Regan, 1906 –1908; Meek & Hildebrand, 1923; Kailola & Bussing, 1995), while Ariopsis gilberti and Ariopsis simonsi have been taxonomically redefined herein. Tachisurus jordani Eigenmann & Eigenmann (1888) , described from the EP of Panama, is recognized as valid by Eigenmann & Eigenmann (1889), Jordan & Everman (1896), Meek & Hildebrand (1923), and Hildebrand (1946). Galeichthys jordani (sensu Meek & Hildebrand, 1923) was differentiated from Ariopsis seemanni based on qualitative degrees of granulation on the cephalic shield, i.e., “roughly granular vs. smooth” or “slightly granular”, “median keel of the occipital process low and blunt vs. sharp”, “snout very low, and the eye small vs. larger” (see Meek & Hildebrand, 1923: 105). Because our perusal of these characters reveal intraspecific variation and ontogenetic variation, they cannot be used as diagnostic. For these reasons, we follow the opinion of Regan (1906–08) and Kailola & Bussing (1995) that T. jordani is a junior synonym of Ariopsis seemanni , but acknowledge that the species, as delimited herein, possibly represents a species complex.

Figures

FIGURE 3. Neurocranium, dorsal view. A. Ariopsis guatemalensis, STRI 5.2.13.3.; B. A. felis, catfishesbone. acnatsci. org; C. A. canteri, uncataloged; D. A. seemanni, STRI 5.1.1.19.; E. A. jimenezi, STRI no registry; F. A. simonsi, STRI 5.1. 1.10. Abbreviation: LEepb, external posterior branch of Lateral Ethmoid; PT, Pterotic; MS, Mesethmoid; MSmn, Mesethmoid medial notch; mg, medial groove of cranium; SH, Sphenotic.

FIGURE 4. Medial groove of neurocranium. A. Ariopsis felis and B. A. assimilis. White, anterior fleshy portion (apposed to the anterior cranial fontanel); gray, posterior bony portion (formed by the mesial depression of the frontals and the anterior portion of parietosupraoccipital).

FIGURE 5. Sampling localities of examined material.

FIGURE 9. A, Clade including the genera Sciades + Potamarius + Ariopsis, extracted from the Ariidae tree of Betancur-R. et al. (2012), including five of the eight species of Ariopsis validated herein. The complete time tree was estimated using a Bayesian analysis of five mitochondrial and six nuclear gene fragments and 19 calibration points (both inside and outside Ariidae). B, Rooted RAxML phylogram with expanded specimen sampling for six species of Ariopsis, but based on the analysis of only two mitochondrial genes (Cyt b and ATPase 8 / 6; 1937 bp). Nodal numbers indicate RAxML bootstrap support values and posterior probability values (MrBayes tree), respectively. The RAxML and MrBayes trees are identical with respect to topology and highly similar with respect to branch lengths. Two letter country codes follow ISO- 3166.

FIGURE 18. Body in lateral view. (A) Ariopsis seemanni, 300 mm TL, Holotype, BMNH 1855.9.19.1107; (B) Tachisurus jordani, Syntype, MCZ 4945; (C) Galeichthys eigenmanni, Holotype, CAS-SU 6986.

FIGURE 19. Head in dorsal view. (A) Ariopsis seemanni, Holotype, BMNH 1855.9.19.1107; (B) Tachisurus jordani, Syntype, MCZ 4945; (C) Galeichthys eigenmanni, Holotype, CAS-SU 6986.