How to Identify Many-toothed Jenynsia

To identify Many-toothed Jenynsia (Jenynsia multidentata), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Generally silvery to olive-brown dorsally, fading to a lighter, often yellowish or whitish ventral surface. Some individuals may exhibit faint vertical bars or scattered dark spots along the flanks. Fins are typically hyaline (clear) to yellowish.

Scale type

cycloid

Mouth position

superior

Distinctive features

Superior mouth, adapted for surface feeding., Sexual dimorphism: males possess a highly modified, asymmetrical anal fin (gonopodium) that is fixed to either the left or right side., Females have a corresponding asymmetrical genital opening.

Dorsal fin

Single, relatively small, positioned posteriorly, originating behind the anal fin origin.

Tail fin

Truncate to slightly rounded.

Pectoral fin

Well-developed, positioned laterally.

Distinctive fins

Anal fin of males is modified into a gonopodium, which is a rigid, elongated, and asymmetrical intromittent organ. The gonopodium is either 'left-sided' or 'right-sided', meaning it is curved to one side.

Identification Tips

1. 1

   Mouth position

   Its superior mouth, angled upwards, is a key indicator, suggesting a surface-feeding habit.

2. 2

   Male gonopodium

   The most definitive feature for males is the asymmetrical, rigid gonopodium, which is curved either to the left or right. This is unique among livebearers.

3. 3

   Body shape and size

   Small, elongated body, typically reaching up to 10-12 cm (4-5 inches) in total length, with females generally larger than males.

4. 4

   Dorsal fin position

   The dorsal fin is set far back on the body, originating posterior to the anal fin origin.

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