Ariopsis assimilis Gunther 1864
Creators: name: Marceniuk, Alexandre P.
name: Acero, Arturo
name: Cooke, Richard
name: Betancur-R, Ricardo
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Siluriformes
Ariidae
Ariopsis
Ariopsis assimilis

description: Ariopsis assimilis (Günther, 1864)
Mayan Sea Catfish (English), Bagre maya (Spanish). Figures 1 and 2, Tables 2–5
Arius assimilis Günther, 1864:146. Type locality: Lake Izabal [Yzabal], Guatemala. Holotype: BMNH 1864.1.26.98. Galeichthys assimilis, Regan, 1906 –1908: 122.
Ariopsis assimilis, Taylor & Menezes, 1978; Castro Aguirre et al., 1999: 156–157; Acero P., 2003: 838; Robertson et al., 2015.
Material examined. Type-specimen: BMNH 1864.1.26.98 (female, 290 mm SL), Guatemala, Izabal. Non-type specimens: USNM 212131 (1, 207 mm SL), Mexico, Quintana Roo; UMMZ 196479 (4, 252– 233 mm SL), Mexico, Quintana Roo, Laguna Bacalar; UMMZ 213491 (2, 168– 225 mm SL), Mexico, Quintana Roo, Laguna Bacalar; FMNH 103770 (2, 243– 254 mm SL), Belize, Belizean Beach, 4.5 miles on western highway; AMNH 35070 (7, 147– 236 mm SL), Guatemala, Izabal, Río Nimblaja, 1 km above mouth into Río Sarstún; USNM 114587 (1, 196 mm SL), Guatemala, Río Sarstún, +/- 20 mi. above mouth; UMMZ 197214 (5, 144– 200 mm SL), Guatemala, Izabal, Río Nimblaja, 1 km above mouth in Río Sarstún; AMNH 32941 (2, 194– 245 mm SL), Guatemala, Izabal, Río Dulce, inside channel ca. 400 m, below Castillo San Felipe; UA 69–91 (1), Mexico, Quintana Roo, Isla Cozumel.
Diagnosis. Ariopsis assimilis is distinguished from its congeners as follows: from A. canteri, from Colombian Caribbean, by 31–36 gill rakers on the first and second gill arches, rarely 37 (vs. 38–44, rarely 36 or 37); from A. felis, from Massachusetts (US) to Yucatán in Mexico (Caribbean), by 34–37 gill rakers on the first and second gill arches (vs. 29–32), osseous medial groove absent (vs. present; Figs. 2 and 3), fleshy medial groove of neurocranium conspicuous or inconspicuous, but never surpassing posterior margin of eyes (vs. conspicuous and very long, surpassing the posterior margin of eyes, Figs. 2 and 4), lateral margin of sphenotic straight, as wide anteriorly as medially (vs. notched laterally, narrower medially than anteriorly, Figs. 2 and 3), pterotic lateral margin markedly convex, sometimes angled (vs. smoothly convex, Figs. 2 and 3); from A. gilberti, from Mexico (EP), by the presence of 14–18 gill rakers on the first gill arch (vs. 19–20, Table 3), osseous medial groove absent (vs. present; Figs. 2 and 3), fleshy medial groove of neurocranium conspicuous or inconspicuous, but never surpassing posterior margin of eyes (vs. conspicuous and very long, surpassing the posterior margin of eyes, Figs. 2 and 4), lateral margin of sphenotic straight, as wide anteriorly as medially (vs. notched laterally, narrower medially than anteriorly, Figs. 2 and 3); from A. guatemalensis, from Mexico to Costa Rica (EP), by its narrower mouth 10.5–13.2% SL (vs. 13.0–15.2% SL, rarely less than 13.2%), narrower cephalic shield at frontals area 8.8–10.1% SL (vs. 10.0–11.5% SL, rarely less than 10.1%), narrow mesethmoid median portion (vs. wide, Fig. 3), mesethmoid medial notch narrow and deep (vs. large and shallow, Fig. 3); from A. jimenezi, from Archipiélago de las Perlas in Panama (EP), by longer pectoral-fin spine 18.2–22.6% SL (vs. 14.6–18.1% SL), osseous medial groove absent (vs. present; Figs. 2 and 3), fleshy medial groove of neurocranium conspicuous or inconspicuous, but never surpassing posterior margin of eyes (vs. conspicuous and very long, surpassing the posterior margin of eyes, Figs. 2 and 4), lateral margin of sphenotic straight, as wide anteriorly as medially (vs. notched laterally, narrower medially than anteriorly, Figs. 2 and 3), pterotic lateral margin markedly convex, sometimes angled (vs. smoothly convex, Figs. 2 and 3), 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. seemanni, from El Salvador to Panama (EP), by the absence of osseous medial groove (vs. present; Figs. 2 and 3), lateral margin of sphenotic straight, as wide anteriorly as medially (vs. notched laterally, narrower medially than anteriorly, Figs. 2 and 3); from A. simonsi, from Colombia to Peru (EP), by the absence of osseous medial groove (vs. present; Figs. 2 and 3).
Description. Morphometrics and meristics summarized in Tables 2–5. Head moderately long, wide and relatively low, notably depressed at lateral ethmoid and frontal area, profile elevated posteriorly, straight from mesethmoid to parietosupraoccipital. Snout rounded and moderately long. Anterior nostrils rounded, with fleshy edge, posterior nostril covered by flap of skin; nostrils moderately separated and moderately distant from orbit, not connected by fleshy furrow. Eye lateral, relatively large. Eyes widely spaced. 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 wide on supracleithrum area, and relatively narrow on 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, without reaching eyes, posterior osseous medial groove inconspicuous or absent. Lateral margin of sphenotic straight, as wide medially as anteriorly. Pterotic lateral margin markedly convex, sometimes angled. Parietosupraoccipital process 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 relatively 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, moderately 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. Fourteen to 18 acicular gill rakers on first arch, 17–20 spike-shaped gill rakers on second arch and some rudiments at the end; rakers present on posterior margin of all gill arches.
13 14 15 16 17 18 19 20
Ariopsis assimilis 1 2 8 2 1
Ariopsis canteri 3 7 1 5 11 Ariopsis felis 2 4 3 1
Ariopsis gilberti 2 3 Ariopsis guatemalensis 1 1 1
Ariopsis jimenezi 3 8 1
Ariopsis seemanni 2 6 1 1
Ariopsis simonsi 1 4 7 3 2
14 15 16 17 18 19 20 21 22 23 24
Ariopsis assimilis 1 4 3 4
Ariopsis canteri 2 5 9 11 5 4 Ariopsis felis 2 5 3
Ariopsis gilberti 1 3 3 1 Ariopsis guatemalensis 1 1 Ariopsis jimenezi 1 1 6 4
Ariopsis seemanni 3 1 3
Ariopsis simonsi 3 1 2 3 3 2 1 1
Body significantly 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 spine relatively short and thick, shorter than 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 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 conspicuous serrations. Nine to 11 pectoral-fin soft rays. Posterior process of cleithrum triangular, slightly visible, smooth to rugose. Pelvic-fin deep and large at base, with six rays, 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 17–20 rays and ventral profile concave. Caudal peduncle moderately high. Caudal-fin forked, dorsal and ventral lobes moderately long, dorsal lobe somewhat longer than ventral lobe, posteriorly slightly pointed.
Maximum length: Grows to 350 mm TL.
Coloration in alcohol. Head and body counter-shaded, dorsum brown to blackish, venter light beige; dorsal surfaces of pelvic and pectorals proximally black, distally lighter; anal dark, distal tips lighter; caudal grayish to blackish (Fig. 1).
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. The WA Ariopsis assimilis occurs in fresh and estuarine waters, from Quintana Roo on the Caribbean coast of Mexico to Honduras (Fig. 5).
Remarks. Ariopsis assimilis was described by Günther (1864) based on a single specimen collected at Lake Izabal, Guatemala (Figs. 1 and 2). The original description used characters that are shared with congeneric species. Thus, the recognition of A. assimilis relies on a combination of morphometric, meristic, and osteological features observed on the type specimen and non-type specimens. Posteriorly, Jordan & Gilbert (1882) assigned A. assimilis to both coasts of tropical America, including Magdalena Bay, Mazatlán, and Altata in Mexico, and the Magdalena River, Colombia. The Colombian Magdalena record is in error, since Jordan & Gilbert (1882) described a fontanel prolonged backward as a narrow groove. After Gunther “ median longitudinal fonticulus on the upper side of the head does not extend to the base of occipital process”, a condition that is verified in the type specimen (Fig. 2).
description: Published as part of 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, pp. 1-42 in Zootaxa 4290 (1) on pages 4-8, DOI: 10.11646/zootaxa.4290.1.1, http://zenodo.org/record/828843