New Gymnotus knifefish described

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Scientists from the University of Louisiana at Lafayette have described a new species of brown, banded electric knifefish from the upper Juruá River drainage in southeastern Peru.

Emmanuel Maxime and James Albert name the new species Gymnotus chaviro in a recent issue of the journal Neotropical Ichthyology.  

The new species resembles G. carapo and is distinguished from congeners in the G. carapo group by its unique colour pattern of oblique, dark, unbroken pigment bands along the length of the body, dark band-pairs with wavy, irregular margins, mainly unbranched or incompletely separated, pale inter-bands rarely reaching to the dorsal mid- line on the front half of the body and crescent-shaped in the abdominal area.  

According to the authors, G. chaviro (named after the common name for Gymnotus by the Aseninka people) "…inhabit pools and runs of small terra firme streams as they enter the floodplain, and the vegetated margins of flooplain lakes, with substrates of leaf litter and organic rich mud.

Specimens are most dense in submerged stems and roots of aquatic grasses (e.g., Oryza spp.) and floating macrophytes (e.g., Eichornia crassipes). At the period of low water (August) when collections were made, specimens were very abundant, aggregated closely together, and were not distributed into discrete territories."

It is further distinguished by a combination of: 17–22 oblique bands on the body, clear (unpigmented) patch of membrane at the hind end of the anal fin, pale grey anal fin, 4–5 arrow-head shaped teeth at the front end of the lower jaw, body depth 6.3–10.2% total length, mouth width 35.5–52.5% head length, interorbital distance 37.9–49.2% head length, head depth 61.8–89.0% head length, head width 58.5–74.7% head length, pectoral fin length 45.8–66.8% head length, 18–19 pectoral-fin rays, 48–52 pored lateral-line scales to the first ventral ramus, head length 8.9–12.0% total length, 7–12 ventral lateral-line rami 7-12, 228–280 anal-fin rays, four caudal rows of electroplates, and 7–9 scales above the lateral line.

For more information, see the paper: Maxime, EL and JS Albert (2009) A new species of Gymnotus (Gymnotiformes: Gymnotidae) from the Fitzcarrald Arch of southeastern Peru. Neotropical Ichthyology 7, pp. 579–585.