Hoplias microlepis ( Günther, 1864 )

Mattox, George M. T., Bifi, Alessandro G. & Oyakawa, Osvaldo T., 2014, Taxonomic study of Hoplias microlepis (Günther, 1864), a trans-Andean species of trahiras (Ostariophysi: Characiformes: Erythrinidae), Neotropical Ichthyology 12 (2), pp. 343-352 : 344-348

Hoplias microlepis ( Günther, 1864)

Figs. 1-3

Macrodon microlepis Günther, 1864: 282 [original description; type-locality:Western Ecuador and Chagres River]. - Eigenmann & Eigenmann, 1889: 102 [diagnosis in key, citation to Western slopes of South America from Guayaquil to Panama].

Macrodon trahira var. microlepis Steindachner, 1880: 101 [citation to Guayaquil, Ecuador].

Hoplias microlepis . - Starks, 1906: 772 [comparison with Hoplias malabaricus , citation to Guayaquil, Ecuador]. - Regan, 1908: 167 [redescription, citation to Rio Chagres, Panama and Western Ecuador]. -Meek & Hildebrand, 1916: 303 [diagnosis in key, citation to both slopes of Panama and the Western slope of Ecuador]. - Eigenmann, 1921: 508-511 [citation, distribution]. - Eigenmann, 1922: 169 [diagnosis in key, citation to Pacific slope of Southern Ecuador and both slopes of Central Panama]. - Hildebrand, 1938: 290 [distribution]. - Bussing, 1966: 218 [citation to Puntarenas, Costa Rica]. - Géry, 1977: 102 [diagnosis in key, citation to Pacific slope of Southern Ecuador, Panama and Costa Rica]. - Ortega & Vari, 1986: 10 [checklist, citation to Peru]. - Oyakawa, 2003: 240 [checklist, distribution]. - Barriga, 1991: 31 [checklist]. - Ortega et al., 2011: 39 [checklist, citation to Peru]. - Barriga, 2012a: 110 [distribution, endemism in Guayas basin]. - Barriga, 2012b: 213 [citation to Ecuador with photograph]. - Aguirre et al., 2013 [morphological and genetic divergence among populations in Ecuador].

Lectotype. Panama. Panama Province. Chagres basin: BMNH 1864.1 .26.221, 269.7 mm SL, Chagres River , purchased of Mr. Salvin ( Fig. 1 ) [designated herein].

Paralectotypes. Ecuador. BMNH.1860.6.16.128, 1, 276.6 mm SL, West Ecuador , collector Fraser; BMNH.1860.6.16.154-155, 3, 96.6- 118.5 mm SL, West Ecuador, collector Fraser ; Panama. Panama Province. Chagres basin: BMNH 1864.1.26. 222, 1, 222.8 mm SL, same information as lectotype; BMNH 1864.1 .26.309, 1, 175.6 mm SL, same locality as lectotype, collected by Messrs. Dow & Salvins ( Fig. 2 ). [all designated herein] .

Material examined. Ecuador. Guayas. Río Daule basin : BMNH 1898.11 .4.45, 1, 230.9 mm SL, río Daule, West Ecuador , Dr. H. Festa ; BMNH 1920.12.20.129-130, 2, 207.9- 254.1 mm SL, Colimes, C. H. Eigenmann ; BMNH 1920.12.30.131-132, 2, 174.1- 188.9 mm SL, Guayaquil, C. H. Eigenmann ; FMNH 93480 , 5 , 60.5-126.3 mm SL (5 specimens radiographed), Los Ríos, Río Palenque, Estación Biológica Río Palenque , about 5 miles downstream from station in an isolated pool, G. S. Glodek, G. Whitmire & J. Dryan, 30 Jul 1974 ; USNM 53512 , 2 , 217.5 - 219.5 mm SL, Guayaquil, P. Simmons ; USNM 94064 , 6 , 234.6 - 296.4 mm SL, Guayaquil, W. L. Schimitt, 05 Jan 1934 ; Panama. Chiriqui. USNM 78601 , 1, 252.8 mm SL, Bas Obispo, Mandingo River , S. E. Meek & S. F. Hildebrand, 02 Feb 1911 ; Coclé. USNM 310650 , 1 , 85.3 mm SL, Membrillal River at bridge on IAH ( Inter-American Highway ), about 5 miles East of Divisa, H. Loftin et al., 25 Feb 1962 ; USNM 310676 , 1, 140.7 mm SL, creek about 3 miles West of Hato River at bridge on IAH (Inter-American Highway), H. Loftin & E. Tyson, 14 Oct 1961 ; Colón. USNM 78606 , 2 , 131.2 - 141.5 mm SL, small creek at Mindi, S. E. Meek & S. F. Hildebrand, 21 Jan 1911 ; USNM 78608 , 10 , 55.7-108.9 mm SL, Gatún River , Canal Zone, S. E. Meek & S. F. Hildebrand, 24 Jan 1911 ; USNM 78609 , 4 , 128.3 - 182.3 mm SL (4 specimens radiographed), creek opposite Mindi Cut, S. E. Meek & S. F. Hildebrand, 17 Jan 1911 ; USNM 78613 , 2 , 143.2 - 156.9 mm SL (2 specimens radiographed), Mindi creek, French Cut-Off , Canal Zone, S. E. Meek & S. F. Hildebrand, 2 Mar 1911 ; USNM 78614 , 4 , 106.5 - 137.9 mm SL, Gatún River, Monte Lirio , Canal Zone, S. E. Meek & S. F. Hildebrand, 27 Mar 1911 ; USNM 78615 , 4 , 143.2 - 156.9 mm SL (4 specimens radiographed), Largateria Creek, Canal Zone , S. E. Meek & S. F. Hildebrand, 09 Mar 1911 ; USNM 78617 , 11 , 143.2 - 156.9 mm SL (9 specimens radiographed), Mindi Creek, Canal Zone , S. E. Meek & S. F. Hildebrand, 14 Jan 1911 ; USNM 310672 , 1 , 79.6 mm SL, Agua Salud creek on pipeline road near Gamboa, H. Loftin, et al., 31 Dec 1961 ; Darién. USNM 293250 , 5 , 164.7 - 176.2 mm SL (5 specimens radiographed), Pirre River, Tuira, above El Real , 8º05’60’’N 77º45’00’’W, J. Lundberg, B. Chernoff & L. Mcdade, 16 Feb 1985 ; Herrera. USNM 310444 , 1, 186.7 mm SL (1 specimen radiographed), Barrera near Pesé, H. Loftin & E. Tyson, 1961 ; USNM 310678 , 1, 130.4 mm SL, Herrera Creek about 4 miles up Pesé road from junction with Chitre-Divisa Road, H. Loftin & E. Tyson, 21 Oct 1961 ; Los Santos. USNM 78595 , 3 , 131.1 - 163.7 mm SL, río Abajo , S. E. Meek & S. F. Hildebrand, 22 Apr 1911 ; Panama Province. USNM 78603 , 2 , 37.8-186.3 mm SL (2 specimens radiographed), Juan Diaz River , S. E. Meek & S. F. Hildebrand, 17 Jul 1911 ; USNM 78605 , 11 , 37.8-186.3 mm SL (6 specimens radiographed), Alhajuela, Limon Creek , S. E. Meek & S. F. Hildebrand, 26 Feb 1911 ; USNM 78607 , 1, 138.1 mm SL, río Chagres, Gorgona , S. E. Meek & S. F. Hildebrand, 01 Apr 1912 ; USNM 109278 , 3 , 35.4-153.4 mm SL, small creek tributary to Chagres River , Madden Dam Road, S. E. Hildebrand, 14 Feb 1935 ; USNM 310673 , 1, 129.9 mm SL, creek at bridge on IAH (Inter- American Highway ), about 4 miles East of Pacora X-Road, G. H. Loftin & M. Smith, 24 Apr 1962 ; Veraguas. MZUSP 47931 , 2 , 45.3 -106.0 mm SL, creek at bridge about 9 miles from Santiago on San Francisco Road , H. G. Loftin, 14 Jan 1962 ; MZUSP 47932 , 1, 132.7 mm SL, río Frijoles , S. E. Meek & S. F. Hildebrand, 14 Mar 1911 ; USNM 78597 , 1, 151.6 mm SL, Trinidad River, Icc. Hydro Station , S. E. Meek & S. F. Hildebrand, 08 Mar 1911 ; USNM 78598 , 2 , 134.4 - 138.7 mm SL, Gatun, Trinidad River , S. E. Meek & S. F. Hildebrand, 24 Jan 1911 ; USNM 78599 , 2 , 116.1 - 144.7 mm SL, Agua Clara, Trinidad River , S. E. Meek & S. F. Hildebrand, 10 Mar 1911 ; USNM 78600 , 1, 148.5 mm SL, Agua Clara, Trinidad River , Canal Zone, S. E. Meek & S. F. Hildebrand, 10 Mar 1911 ; USNM 78611 , 5 , 32.3-138.2 mm SL, Frijoles River , Canal Zone, S. E. Meek & S. F. Hildebrand, 13 Feb 1911 ; USNM 78612 , 1 , 98.5 mm SL, Gorgona Reservoir , Canal Zone, S. E. Meek & S. F. Hildebrand, 28 Mar 1912 ; USNM 310677 , 1 , 70.2 mm SL, creek 13 miles West of Ocu X-road, Loftin, et al., 21 Oct 1961 ; USNM 310680 , 1, 189.4 mm SL, creek 20 miles West of Santiago , H. Loftin, 1961 .

Diagnosis. Hoplias microlepis differs from all other species of Hoplias , except for species of H. malabaricus group, in the shape of the dentaries abruptly converging towards the mandibular symphysis (Oyakawa & Mattox, 2009: 118, Fig. 1d ) (vs. dentaries parallel and only gently converging towards the mandibular symphysis) and by the presence of tooth plates on tongue (vs. tooth plates on tongue absent). H. microlepis is also distinguished from H. brasiliensis and H. curupira in the number of scales along lateral line (43-47 vs. 38-43 and 34-39, respectively), and from H. australis and H. lacerdae in the number of pores of the laterosensory system along the ventral surface of dentary (4 vs. always 5 and 6-8 respectively). H. microlepis is distinguished from H. aimara by the presence of the accessory ectopterygoid and lack of a vertically elongate dark spot on the opercular membrane (vs. accessory ectopterygoid absent and dark spot present). H. microlepis is distinguished from the other species in the H. malabaricus species group by the higher number of scales around the caudal peduncle (22-24, usually 24 vs. 18-20, usually 20).

Description. Morphometric data presented in Table 1 . Body cylindrical, deeper than wide. Greatest body depth at vertical through fifth or sixth scale anterior to dorsal-fin origin in specimens smaller than 61.4 mm SL, closer to dorsal-fin origin in larger specimens. Anterior profile of head angular in lateral view. Overall dorsal profile of head straight, slightly convex anteriorly towards snout. Dorsal margin of orbit located at horizontal through dorsal profile of head in specimens smaller than 45.3 mm SL, but not reaching dorsal profile of head in larger specimens (ca. 61.4 mm SL). Dorsal profile of trunk slightly convex from vertical through first series of scales of body to dorsal-fin origin; straight and posteroventrally inclined along dorsal-fin base; straight and less inclined to slightly concave from vertical through base of last dorsal-fin ray to origin of anteriormost dorsal procurrent caudal-fin ray. Ventral profile of lower jaw distinctly angular in region of mandibular symphysis, straight to slightly inclined from vertical through anterior nostril to posterior margin of lower jaw. Medial margins of contralateral dentaries abruptly converging anteriorly towards symphysis. Ventral profile of trunk slightly convex to pelvic-fin origin; approximately straight to slightly convex from latter point to anal-fin origin; straight and posterodorsally inclined along anal-fin base; straight or slightly concave from base of last anal-fin ray to anteriormost ventral procurrent caudal-fin ray.

Upper jaw slightly shorter than lower jaw. Posterior portion of maxilla dorsally enlarged and extending medially to anterior margins of second and third infraorbitals. Upper and lower lips fleshy, with short projections of skin covering canines externally. Anterior nostril tubular with anterior slit reaching base of tubular portion.Anterior and posterior nostrils situated along horizontal through center of orbit, posterior nostril situated midway between anterior nostril and anterior margin of orbit. Eye proportionately larger in smaller specimens. Infraorbital bones well developed and horizontally elongate. Infraorbitals 3, 4, and ventral portion of 5 partially covering preopercle. Anteroventral margin of infraorbital 3 relatively straight and posteroventral margin convex. Posterior margin of infraorbitals 4, 5, and 6 slightly convex.

Teeth in both jaws conical or canine. Premaxillary teeth in single row. First premaxillary tooth large canine, second tooth medium sized canines. Seventh tooth canine almost as large as anterior most premaxillary canine. Third to sixth, and eighth premaxillary teeth small and conical. Maxilla with single row of approximately 38-39 relatively small teeth, except for very welldeveloped canine-like fourth or fifth tooth. Dentary with anterior external row of teeth and posterior internal row. External series with four anterior small teeth, followed by two well-developed canines with posterior canine larger than anterior canine, and then 11 conical teeth slightly smaller than anterior most dentary canine. Internal series beginning immediately posterior to last conical tooth of external row and composed of approximately 15 very small teeth.Accessory ectopterygoid and ectopterygoid toothed. Ectopterygoid with series of small conical teeth along ventrolateral margin and many smaller viliform teeth on ventromedial surface. Endopterygoid edentulous.

Distal margins of all fins rounded. Dorsal-fin rays ii, 11-13 (mode: ii,12*, n = 64). Dorsal fin located at midbody, its origin at vertical through approximately fourth scale anterior to series along pelvic-fin origin. Longest dorsal-fin ray approximately three-quarters of body depth.Anal-fin base short.Anal-fin rays iiiii, 7-9 (mode: ii,8*, n = 61). Tip of depressed dorsal fin reaching vertical through anal-fin origin in small specimens (less than 138 mm SL) but falling short of that point in larger specimens. Pectoral-fin rays i,10-14 (mode: i,13, n = 63, lectotype with i,12). Pectoral-fin origin located at about vertical through median region of opercle. Tip of pectoral fin separated from pelvic-fin origin by three to five scales. Pectoral and pelvic fins of similar size. Pelvic-fin rays i,7* (n = 64). Pelvic-fin origin situated at midbody and approximately four scales posterior to vertical through dorsal-fin origin. Tip of pelvic fin separated from analfin origin by five or six scales. Caudal-fin rays i,15,i* (n =58).

Well-developed cycloid scales imbricated along body. Series of dorsal scales beginning at vertical on posterior margin of parietals and overlapping supraoccipital spine. Last vertical series of scales on caudal peduncle forming straight vertical line on caudal-fin base in lateral view. Anterior margin of scales with small concavity and posterior margin rounded. Approximately twelve radii extending from center of scale to its anterior margin and around sixteen radii, some anastomosed, extending from center of scale to its dorsal, posterior, and ventral margins. Lateral line straight and complete, extending from posteroventral margin of supracleithrum to posteriormost scale on body. Lateral line with 43-47 (mode: 45, n = 61, lectotype with 44) scales. Longitudinal series of scales between lateral line and dorsalfin origin 6.5-7.5 (mode: 6.5*, n = 63). Longitudinal series of scales between lateral line and pelvic-fin origin 5.5-6.5 (mode: 5.5*, n = 63). Longitudinal series of scales around caudal peduncle 22-24 (mode: 24*, n = 62).

Approximately 9 gill rakers on first epibranchial, most in form of small denticulated plates. Lower branch of first branchial arch with 4-6 (mode: 5*, n = 48) more elongate rakers and approximately 10 plate-like rakers. Laterosensory canal along ventral surface of dentary with 4* (n = 61) pores, one specimen with 5 pores. Total vertebrae: 42-45 (n = 41), 28-30 precaudal and 13-15 caudal vertebrae.

Color in alcohol. Ground coloration of head and body dark to light brown, darker dorsally and paler ventrally ( Fig. 3 ). Ventral region homogeneously white or light yellow in specimens up to 106.2 mm SL. Larger specimens (i.e., 130.0 mm SL) with scales of ventrolateral surface of body with white central portion bordered by darker pigmentation, giving aspect of thin longitudinal dark and pale stripes. Specimens up to 60 mm SL with conspicuous dark longitudinal stripe along lateral line scales, covering approximately half of the series immediately above and below lateral line. Longitudinal dark stripe less conspicuous in larger specimens. Approximately five to six darker parallel diagonal bars along dorsal region extending anteroventrally to just below lateral line ( Fig. 3 ). Diagonal dark bars in many specimens continuing posteroventrally to approximately three longitudinal scale series below lateral line, resulting in chevronlike pattern. Dorsal portions of bars more evident than ventral portions. Bars more conspicuous in specimens with light brown ground coloration. Specimens larger than 106.0 mm SL with conspicuous round spot on dorsal portion of caudal peduncle, near base of uppermost caudal-fin rays ( Fig. 3 ). Dorsal surface of head dark brown. Lips with alternating dark and light vertical bands, inconspicuous in some specimens. Ventral surface of dentaries varying from white in small specimens (ca. 35.4 mm SL), to alternating dark and light transverse stripes in specimens larger than 61.4 mm SL. Coloration of infraorbital region and dorsal surface of head similar to each other. Many specimens with two dark stripes radiating posteriorly from eye along infraorbital 6 and dorsal portion of infraorbital 3. Ground coloration of opercular series dark brown. Opercular membrane usually lighter than opercle ( Fig. 3 ).

All fins light brown, lighter than body in some specimens, with dark spots on rays and interradial membranes forming pattern of irregular dark stripes ( Figs. 1 , 2 a-b, 3). Stripes on pelvic, anal and caudal fins wider and more regular than those on dorsal fin. Ventral surfaces of pectoral and pelvic fins either lighter than, or with same pattern as, dorsal surface, but with pattern less conspicuous. Fins of largest specimens (ca. 163.0 mm SL) usually darker than rest of body.

Distribution. Hoplias microlepis occurs in rivers along the entire Pacific coast of Panama and in rivers tributaries to the Panama Canal including the Atlantic coast. The species also occurs in the río Guayas basin which empties in the Gulf of Guayaquil, Ecuador. Although we did not examine specimens from Costa Rica and Peru, there are records in the literature of Hoplias microlepis in Puntarenas, Southwestern Costa Rica ( Bussing, 1966) and río Tumbes, Northwestern Peru ( Ortega & Vari, 1986) ( Fig. 4 ).

Figures

Fig. 1. Hoplias microlepis (lectotype of Macrodon microlepis), BMNH 1864.1.26.221, 269.7 mm SL, Chagres River, Panama.

Fig. 2. Hoplias microlepis (paralectotypes of Macrodon microlepis). (a) BMNH 1864.1.26.222, 222.8 mm SL, Chagres River, Panama; (b) BMNH 1864.1.26.309, 175.6 mm SL, Chagres River, Panama; (c) BMNH 1860.6.16.128, 276.6 mm SL, West Ecuador; (d) BMNH 1860.6.16.154-155, 96.6 mm SL, West Ecuador; (e) BMNH 1860.6.16.154-155, 108.2 mm SL, West Ecuador; (f) BMNH 1860.6.16.154-155, 118.5 mm SL, West Ecuador.

Fig. 3. Hoplias microlepis, USNM 293250, 176.2 mm SL, Pirre River, Tuira, Panama.

Fig. 4. Map of Northwestern South America and part of Central America showing geographic distribution of Hoplias microlepis based on material examined herein (star and dots) and records from literature (squares). Star indicates type-locality at Chagres River, Panama. Some symbols may represent more than one lot.