How to Identify Dwarf Pencilfish

To identify Dwarf Pencilfish (Nannostomus marginatus), look at these key features.

Physical Characteristics

Body shape

torpedo

Coloration

The body is typically a golden-brown to reddish-brown base color. The most prominent feature is three distinct dark horizontal stripes running along the flanks. The uppermost stripe runs from the snout through the eye to the caudal peduncle. The middle stripe, often the most intense, runs from the operculum to the caudal fin base. A third, less distinct stripe may be present along the ventral side. Fins are generally hyaline (clear) but can show reddish tints, especially the caudal and anal fins. Males often exhibit more intense coloration, particularly during breeding, with red or orange hues in the fins and along the body stripes.

Scale type

cycloid

Mouth position

superior

Distinctive features

Three prominent dark horizontal stripes along the body., Small, slender, torpedo-shaped body., Upward-pointing mouth., Males often display more vibrant coloration and may have a more pointed anal fin.

Dorsal fin

Small, single dorsal fin located mid-body, typically with 2 unbranched and 7-8 branched rays.

Tail fin

Forked caudal fin, often with reddish or orange tints.

Pectoral fin

Small, clear pectoral fins, typically with 1 unbranched and 9-10 branched rays.

Distinctive fins

Adipose fin absent. Anal fin typically with 2 unbranched and 7-8 branched rays. Pelvic fins small.

Identification Tips

1. 1

   Size

   Adults typically reach a maximum standard length of 2.5-3.5 cm (1.0-1.4 inches), making them one of the smallest pencilfish species.

2. 2

   Stripes

   Look for the three distinct dark horizontal stripes. The middle stripe is usually the most prominent and extends from the gill cover to the caudal fin base.

3. 3

   Body Shape

   Their slender, torpedo-like body is characteristic of the Nannostomus genus.

4. 4

   Mouth Position

   The mouth is small and upturned, adapted for feeding on surface-dwelling invertebrates.

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