Creagrutus amoenus Fowler 1943

Vertebrae: 36 - 39

Creagrutus amoenus Fowler, 1943

Creagrutus amoenus Fowler, 1943a:239, fig. 18 [type locality: Colombia (Caquetá), Florencia, Río Ortuguasa (=Orteguaza); one paratype =C. flavescens]; 1948:82, fig. 86 [literature record based on Fowler, 1943a]; 1975:25 [literature compilation].—Géry, 1977:407 [in key].—Wilkens, 1977:156 [paratype despository].—Böhlke, 1984:42 [type depository].—Castro and Arboleda, 1988:8 [Colombia, Río Caqueta].—Vari et al, 1995:289 [comparisons with C. kunturus; C. boehlkei Géry (1972) tentatively placed as synonym of C. amoenus Fowler].—Román-Valencia and Cala, 1996:145 [discussion of species based on literature information].

Creagrutus mülleri [not of Günther, 1859].—Böhlke, 1958:30, tab. 3, pl. 3: fig. 1 [misidentification] [Ecuador (Napo), Río Tutapischo, Río Villano, headwaters of Río Arajuno].

Creagrutus boehlkei Géry, 1972:63, tab. 5, pl. iv: fig. 2 [type locality: Ecuador, “Oriente del Ecuador” (eastern portion of Ecuador); also Río Conambo, Río Capotazo, Río Villano]; 1977:407 [in key].—Wilkens, 1977:156 [paratype depository].—Stewart et al, 1987:26 [Ecuador, Río Napo].—Ibarra and Stewart, 1989:369 [Ecuador, upper Río Napo basin].—Barriga, 1991:17 [literature compilation; eastern portion of Ecuador; based on Géry, 1972].—Vari et al, 1995:289 [C. boehlkei tentatively placed as synonym of C. amoenus]. [New synonymy.]

Creagrutus muelleri [not of Günther, 1859],—Saul, 1975:106 [misidentification] [Ecuador: Napo (now in Sucumbíos), Santa Cecilia, Río Conejo; ecology and stomach contents].

DIAGNOSIS.—The combination of the possession of premaxillary dentition arranged in the three components generalized for most of the species of Creagrutus and Piabina without a pronounced gap between the first and second teeth of the primary premaxillary tooth series, 2 to 4 maxillary teeth, the typical possession of 6 teeth in the primary premaxillary tooth series, 1 post-anal medial scale to the anal-fin origin, 4 scale rows between the lateral line and the dorsal-fin origin, the pigmentation pattern of a series of dark spots along the midlateral line on the body that ontogenetically coalesce, sometimes resulting in a solid stripe in larger individuals, the lack of a distinct patch of pigmentation on the middle portions of the dorsal fin, and the absence of a distinct, vertically elongate humeral mark distinguishes C. amoenus from all congeners with the exception of C. kunturus. Creagrutus amoenus can be separated from C. kunturus, the only other member of the genus with comparable pigmentation on the body and one post-anal scale, by the combination of the number of lateral line scales (35–39 in C. amoenus versus 39–43 in C. kunturus), total vertebrae (36–39, rarely 39, in C. amoenus versus 38–41, typically 39–40, in C. kunturus), the depth of the caudal-peduncle (12.2%–13.8% of SL in C. amoenus versus 11.1%–12.1% of SL in C. kunturus), and the distance from the dorsal-fin origin to the anal-fin origin (33.8%–38.8% of SL in C. amoenus versus 30.9%–33.5% of SL in C. kunturus).

DESCRIPTION.—Morphometric and meristic data for C. amoenus in Table 4. Head and body relatively robust. Greatest body depth at dorsal-fin origin in smaller individuals, variably at, or somewhat anterior of, that line in larger individuals. Dorsal profile of head from tip of snout to rear of supraoccipital spine, ranging from smooth and slightly convex in some specimens to distinctly convex with irregular profile above nostrils in other individuals. Interorbital region distinctly convex. Predorsal profile of body with variably evident change in alignment relative to that of head; slightly convex in smaller specimens, typically distinctly so in larger individuals. Dorsal profile of body inclined at dorsal-fin base, ranging from nearly straight between posterior insertion of dorsal fin and caudal peduncle to slightly convex in region of adipose fin. Ventral profile of head with variably obtuse angle at anteroventral corner of dentary, gently curved from that region to isthmus. Ventral profile of body convex to anal-fin origin, convexity more pronounced in deep-bodied individuals.

Head obtusely pointed in lateral view, distinctly pointed in dorsal view. Upper jaw distinctly longer than, and overhanging, lower jaw. Anterior portion of snout fleshy, with scattered papillae. Papillae more concentrated along ventral margin of upper lip and on fleshy folds and plicae extending between outer and medial premaxillary teeth and along dorsal margin of lower lip.

Infraorbital series moderately developed, proportionally more extensive posteriorly in larger specimens. Ventral margin of third infraorbital curved, deepest region of infraorbital contacting, or nearly contacting, horizontal limb of preopercle. Posterior margins of third through fifth infraorbitals distinctly

Premaxillary dentition in three series: primary row slightly curved or sigmoid, typically with 6 teeth (5 teeth present on one side of head in one specimen) without pronounced gap between first and second tooth of series and with medial tooth separated from its equivalent tooth of contralateral series by distinct gap; triangular cluster of 3 larger teeth; and single tooth of form similar to that of primary series occurring lateral to fourth tooth of primary premaxillary row (2 teeth present in this region of one premaxilla in one, apparently anomalous, specimen). Maxilla with 2 to 4 teeth; teeth all tricuspidate when 2 or 3 teeth present, fourth tooth often with irregular, but not distinctly tricuspidate, distal margin. Dentary typically with 6 teeth, 5 teeth present on dentary on one side of jaws in several specimens. Three anterior dentary teeth distinctly larger than remaining teeth and tricuspidate, with central cusp largest; second tooth largest, about twice as large as first tooth and three times as large as third tooth. Three posterior dentary teeth gradually becoming smaller, with approximately equal and distinct cusps (teeth 4 and 5) or barely apparent cusps (tooth 6, when present).

Dorsal-fin rays typically ii,8, rarely ii,7. Dorsal-fin origin approximately at vertical through pelvic-fin insertion. Profile of distal margin of dorsal fin straight to very slightly concave. Anal-fin rays ii-iii,10–12. Profile of distal margin of anal fin straight to slightly concave. Hooks typically present on anal-fin rays in mature males of many Creagrutus species not present in examined specimens. Pectoral-fin rays i,9–13; relative length of fin somewhat variable, tip extending posteriorly into area slightly to distinctly short of vertical through pelvic-fin insertion. Pelvic-fin rays i,6,i in some small specimens, i,7 in majority of examined individuals. Tip of pelvic fin falling slightly to distinctly short of anus. Hooks typically present on pelvic-fin rays in mature males of many Creagrutus species not present in examined specimens.

Gill rakers of first arch relatively short on epibranchial, elongate on ceratobranchial; 7–8 + 9–11.

COLORATION IN LIFE (based on a transparency of an aquarium specimen provided by H.-G. Evers and the examination of recently collected specimens still in formalin at MEPN).—Overall coloration silvery, more so midlaterally and ventrally. Region above midlateral line with pronounced yellow tint. Yellow coloration most concentrated immediately above midlateral silvery stripe that overlies darker midlateral stripe seen in preserved specimens lacking guanine. Dorsal surface of head yellow. Dorsal fin yellowish, with yellow pigmentation most concentrated along most of length of anterior rays and central portions of remaining rays. Caudal-fin lobes yellow, more so basally, with distal portions having only faint yellow pigmentation. Anal fin with patch of intense yellow pigmentation overlying central portions of all rays, pigmentation more intense anteriorly. Pelvic fin with intense yellow pigmentation on central portions of all but lateralmost rays. Lateralmost pelvic-fin rays with distinct white coloration in photographs of live aquarium specimen. Pectoral fin with broad region of yellow pigmentation; yellow color less obvious on distal portions of rays and on medial rays of fin.

COLORATION IN ALCOHOL.—Overall ground coloration of relatively freshly collected specimens light tan. Dorsal surface of head with dense field of small dark chromatophores, giving region distinctly dusky appearance. Intensity of pigmentation more noticeable over brain, evidently as consequence of deep-lying pigmentation. Dense surface pigmentation continuing anteriorly over snout and upper lip. Denser patch of pigmentation present anterior to nares. Specimens with darker overall head and body pigmentation having region immediately ventral to and posterior to orbit with pigmentation field interrupted by patch of faintly pigmented laterosensory canal segments. Dorsal region of preopercle and infraorbitals with numerous small dark chromatophores. Variably developed pattern of dark pigmentation present posterior to orbit; pattern ranging in form from discrete spot positioned along posterior margin of fourth and fifth infraorbitals, through irregular horizontal band limited to lateral surface of infraorbitals, to distinct stripe extending from posterior margin of orbit to rear of opercle.

Scales of dorsolateral portion of body with small dark chromatophores concentrated along posterior scale margin, giving overall reticulate pattern to body pigmentation in that region. Development of humeral mark highly variable. Overall form of mark vertically elongate, with rotund, intensely pigmented region centered immediately dorsal of lateral line. Intensely pigmented region typically flanked ventrally and dorsally by less pigmented areas. Darkly pigmented region dorsal of humeral mark more apparent in smaller individuals and in larger specimens with less intense overall body pigmentation; pigmentation field anterodorsally sloping and dorsally attenuate. Maximum height of humeral mark approximately equal to that of two scales in that region. Ventral extension of main portion of humeral mark usually less obvious, pigmentation extending about one scale width ventral of main body of mark in form of ventrally attenuating patch of scattered chromatophores. Dark pigmentation along midlateral portion of body highly variable both ontogenetically and between comparably sized individuals. Midlateral pigmentation consisting of two components, midlateral band of dark deep-lying chromatophores and regions of dark surface pigmentation. Surface pigmentation ranging from discrete, widely separated spots approximately size of pupil of eye, through variously coalesced spots and stripe segments, to uninterrupted dark band extending from region of rear of opercle to base of middle caudal-fin rays. Highly developed midlateral stripe subsumes humeral mark. Stripe continuous anteriorly with horizontal stripe extending from rear of orbit to rear of opercle.

Dorsal fin with membranes and margins of fin rays overlain by small dark chromatophores, particularly on distal two-thirds of dorsal-fin rays; intensity of dark pigmentation increasing ontogenetically, with number of rays with such pigmentation also increasing with body size. Basal portions of anal-fin rays outlined by small dark chromatophores in medium-sized individuals, rays nearly completely outlined in larger specimens. Caudal fin with fin rays and membranes overlain by small dark chromatophores, particularly in larger individuals. Distinct band of dark pigmentation on middle caudal-fin rays; band most intense basally where it forms irregular spot in many specimens. Basal portion of rays bordering middle caudal-fin rays less intensely pigmented. Distal portions of middle caudal-fin rays and of rays dorsal and ventral to them with margins more intensely pigmented. Pelvic and pectoral fins nearly hyaline in smaller individuals, dusky in larger specimens.

ECOLOGY.—Saul (1975:106) reported that in the Río Conejo, northeastern Ecuador, Creagrutus amoenus (identified therein as C. muelleri) was taken “in swift current over sand, gravel, or bedrock bottom. A few fish (4) were seined in a slow-flowing effluent of the lower lake.” His analysis of stomach contents revealed that C. amoenus feeds on plant debris, insect debris, fish eggs, dragonfly nymphs, beetle larvae, caddisfly larvae, and fly larvae, including those of chironomids, with fly larvae the most abundant. The smallest mature female examined was a gravid 69.7 mm specimen with 0.9 mm ova captured in mid-June. At one locality in the Río San Miguel basin, northeastern Ecuador, C. amoenus was captured sympatrically with C. flavescens (USNM 340973 and USNM 340986, respectively).

DISTRIBUTION.—Creagrutus amoenus occurs in rivers of the Andean foothills of eastern Ecuador and southeastern Colombia (Figure 22, dots).

MATERIAL EXAMINED.—347 specimens (59, 35.4–91.2).

COLOMBIA. Caquetá: Florencia (approximately 1°45′N, 75°35′W), Río Ortuguasa (=Orteguaza), ANSP 70499, 1 (66.5; holotype of Creagrutus amoenus); ANSP 70500–70502, 2 (54.4–68.0; paratypes of Creagrutus amoenus, third paratype in lot is C. flavescens, see “Remarks,” above); ANSP 70503, 1 (paratype of Creagrutus amoenus, specimen cleared and stained for bone); USNM 100762, 1.

ECUADOR. “Oriente del Ecuador” (=eastern Ecuador), ZSM 28428, 1 (91.2, holotype of Creagrutus boehlkei); ZSM 28429, 2 (75.9–88.6, paratypes of Creagrutus boehlkei); ANSP 136915, 1 (76.5). Pastaza: Río Conambo, tributary of Río Tigre, ZMH 1757, 1 (81.0, paratype of Creagrutus boehlkei). Río Danta, tributary to Río Conambo (1°45′03″S, 76°47′04″W), USNM 311297, 2 (64.2–68.0); USNM 311339, 3 (1, 65.0; 1 specimen cleared and counterstained for cartilage and bone); MEPN 6608, 4; MEPN 6602, 3; MEPN 6607, 27. Río Capotazo, tributary of upper Río Pastaza (approximately 2°07′S, 77°27′W), ZMH 1758, 4 (62.5–70.0, paratypes of Creagrutus boehlkei); MCNG 2183.35, 2 (paratypes of Creagrutus boehlkei). Río Villano, ZMH 1868, 1 (68.5, paratype of Creagrutus boehlkei). Río Villano, near Villano (1°30′S, 77°29′W), ANSP 75910, 1 (76.0); USNM 164045, 5; MEPN uncataloged, 7. Río Tiguino basin, estero of Tiguino No. 3 (unnamed tributary of Río Tiguino; 1°07′35″S, 76°56′52″W), MEPN 4599, 1; MEPN 6288, 5. Río Landayacu, Moretecocha (01°35′12″S, 77°24′18″W), MEPN 7194, 12. Río Metzera (=Río Palora; 1°51′S, 77°49′W), MEPN 5357, 2. Río Jandiayacu, MEPN 9649, 17. Napo: Río Yasuni, Estero Triniti, 45 minutes by boat from Rocafuerte, USNM 311341, 4; MEPN 6497, 3. Río Tut-apishco, near Loreto (0°38′S, 77°19′W), ANSP 75909, 1; ANSP 75908, 1; USNM 164070, 4 (2, 62.4–83.1; 1 specimen cleared and counterstained for cartilage and bone). Stream tributary to Río Napo, approximately 15 mi (23 km) downstream of Missahuali (0°56′S, 77°30′W), ANSP 145981, 1 (81.0). Río Cowi, near camp of oil drilling site in “Bloque 16 Pozo Cowi-Conoco” (0°08′10″S, 76°15′18″W), MEPN 4626, 27 (10, 51.3–76.5); USNM 340985, 4. Quebrada Yaucanoyacu, tributary to Río Payamino, downstream from Río Tiquino (0°25′36″S, 77°19′24″W), FMNH 102997, 28 (10, 37.4–48.8). Quebrada Aulayacu, tributary to Río Payamino (0°25′36″S, 77°19′24″W), FMNH 102998, 11. Quebrada to Río Misahualli, in front of church at Cotundo (0°52′18″S, 77°50′12″W), FMNH 102979, 5. Río Napo, near Puerto Francisco de Orellana (=Coca; 0°28′S, 76°58′W), USNM 340987, 6. Quebrada Yaucanayacu, tributary of Río Payamino, 1 river km below mouth of Río Tiquino (0°25′36″S, 77°19′24″W), MEPN 5267, 50. Quebrada Aulayacu, tributary of Río Payamino, 0.8 river km below mouth of Río Tiquino (0°25′36″S, 77°19′24″W), MEPN 5255, 10. Sucumbíos: Río Conejo, at bridge on road from Lago Agrio to Lumbaqui, near Santa Cecilia (0°3′30″N, 77°02′W), MEPN 5265, 13. Río Shushufindi, tributary to Río Aguarico (0°10′S, 76°40′W), ANSP 137626, 4 (65.5–82.3). Santa Cecilia, Río Conejo (approximately 0°03′N, 76°58′W), 1 km N of town, KU 13457, 7. Río Bahita, 0.5 mi (0.8 km) N of Santa Cecilia, KU 13454, 6. Río Coca drainage basin, headwater tributary of Río Dashino, approximately 9 km SW of Lumbaqui (by road) and 0.3 km S (0°0′3″S, 77°23′48″W), FMNH 102984, 46 (15, 35.4–53.7). Río San Miguel basin, Río La Bermeja, in front of Communidad Shuor Chari (approximately 0′10′N, 76°25′W), MEPN 4640, 6; USNM 340986, 4.