Cat-eLog Right Arrow Auchenipteridae Right Arrow Centromochlinae Right Arrow Gelanoglanis

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Scientific Name Gelanoglanis nanonocticolus  Soares-Porto, Walsh, Nico & Netto, 1999
Common Name
Type Locality Río Asisa, 22-30 kilometers upstream from confluence with Río Paru, Río Ventuari drainage, Orinoco River basin, about 4°33'N, 65°54'W, elevation 115 meters.
Etymology Gelanoglanis: Greek, gelanes, -es, -es = happy, smiling + Greek, glanis = a fish that can eat the bait without touching the hook; a cat fish. nanonocticolus: Latin nanus, = small + Latin nocticolus = night-lover, in reference to the diminutive adult size and apparent nocturnal habits of this species.
Down arrow Species Information
Size 22mm or 0.9" SL. Find near, nearer or same sized spp.
Identification Diminutive auchenipterid catfishes, distinguished by the following unique combination of characters: Single pair of chin barbels (vs. two pairs); pectoral spine, if present, lacking serrations on anterior margin; posterior nare large and immediately anterior to small eye; oblique, sinuous mouth with free fleshy flange around angle of gape; dorsal, anal, and paired fins short based with few rays; third pectoral-fin radial absent. Other shared traits include: Premaxillary tooth patches laterally oriented and widely separated anteriorly at midline; frontals sutured along midline for entire length; anterior fontanelle absent; vomer absent; mesopterygoid reduced to small round bone; mandibular ramus of lateral-line canal free from dentary.

Key for the species of Gelanoglanis (Calegari, Reis & Vari, 2014; Calegari & Reis, 2017)
1a. Pelvic fin almost reaching to the urogenital opening................ 2
1b. Pelvic fin falling short of the urogenital opening by a distance longer than the anal-fin length................ G. varii
2a. Dorsal and pectoral fins with spine................ 3
2b. Dorsal and pectoral fins lacking spine................ G. nanonocticolus
3a. Adult males with short gonopodium terminating at anal-fin origin; premaxillary teeth occupying two-thirds of length of premaxilla; anterior fontanel absent................ 4
3b. Adult males with long gonopodium extending posteriorly to midlength of base of anal fin; premaxillary teeth restricted to anterior portion of bone, occupying one-half or less of length of premaxilla; anterior fontanel present................ G. pan
4a. Dorsal-fin spine with strong serrae along posterior margin................ G. stroudi
4b. Dorsal-fin spine simple, without serrae along posterior margin................ G. travieso.

G. nanonocticolus is distinguished from its congeners by: Dorsal and pectoral fin spines absent (vs. present in G. stroudi). First bony rays of dorsal and pectoral fins are flexible and unbranched, lacking serrations (vs. present as stiffened serrated spines in G. stroudi). Adipose fin absent or, if present, a long, low fin fold (vs. small fin with short base and free posterior margin in G. stroudi). Putative smaller maximum adult body size, 22 mm SL (vs. 36 mm SL in G. stroudi). Structure of adult-male anal fin differs: In G. nanonocticolus, the first three anal-fin rays elongate, unbranched, and enlarged, about twice width of the fourth (longest branched) ray; (vs. the anterior unbranched anal-fin rays (i-iii) not greatly enlarged relative to remaining rays in adult male G. stroudi).
Sexing As in other members of the auchenipterid subfamily Centromochlinae, anal-fin forms an intromittent structure in adult males. Specific to G. nanonocticolus: Nuptial males have shorter anal-fin base and shorter fin rays than females. Gonopore of males forms an elongate, fleshy tube anterior to ossified fin rays; in females, gonopore also anterior to fin, but in shape of a short conical structure. Nuptial males have filamentous tip of first pectoral-fin ray longer than in females of comparable size and extending well beyond interradial membrane between first and second rays.
General Remarks A nocturnally active fish, inhabiting open water areas of blackwater streams and rivers with moderate flow.
Down arrow Habitat Information
Distribution South America: Asisa River basin in Orinoco drainage and Negro River basin.
Orinoco, Upper Orinoco, Ventuari, Paru (Venezuela), Asisa (click on these areas to find other species found there)
Amazon, Middle Amazon (Solimoes), Negro (click on these areas to find other species found there)

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IUCN Red List Category Not Evaluated
pH 4.5 - 5.0
Other Parameters Wild-caught individuals found in open water, with slow to moderate current, low pH, and sand substrate.
Down arrow Husbandry Information
Feeding Stomach contents of wild-caught specimens include adult midges and gnats (Diptera, suborder Nematocera).
Breeding Reports There is no breeding report.
Down arrow Further Information
Reference Ichthyological Exploration of Freshwaters v. 10 (no. 1), pp 65, Fig. 1.
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Last Update 2020 Oct 27 06:35 (species record created: 2015 Oct 15 13:40)