Metynnis maculatus (KNER, 1858) Spotted Metynnis

Synonyms

Myletes maculatus Kner 1858

Etymology

Metynnis is a word that combines the Ancient Greek prefix μετά ‎(metá), meaning ‘after, beyond’, and the Latin adjective maculatus, meaning ‘spotted’.

Classification

• Order: Characiformes
• Family: Serrasalmidae

Distribution

The range of this species is not entirely clear, as there are records of its occurrence from Guyana to the upper and lower Amazon basins in Peru and Brazil, respectively. However, it is likely that this species is only found in the upper Rio Madeira, which is a major tributary of the western Amazon watershed in Bolivia and western Brazil. This includes its significant tributaries, such as the Rios Beni and Mamoré, as well as the upper Rio Paraguai in Brazil.

Most of the records for this species relate to the Rio Guaporé (known as Río Iténez in Bolivia), which is the main tributary of the Rio Mamoré. The Guaporé drains the vast tropical wetland area called the Pantanal, along with the upper Rio Paraguai, which has its headwaters in the Pantanal but flows in the opposite direction. During the annual wet

Maximum Standard Length

The maximum standard length is no less than 148 mm.

Aquarium Size

A minimum aquarium size of 180 * 45 * 45 cm, or an equivalent volume, should be taken into consideration.

Maintenance

While the amount of open swimming space and water quality are crucial factors, the choice of décor is not as critical. It’s possible to maintain healthy specimens in completely bare setups, for example. However, a setup decorated with driftwood roots and branches, a sandy substrate, and some water-worn rocks and boulders would create a more natural-looking environment. It’s best to avoid aquatic plants since they are likely to be eaten.

It’s essential to keep the water spotless as this species is intolerant of organic waste. Moderate levels of dissolved oxygen and water movement are also recommended. Therefore, additional powerheads, pumps, etc. should be used if necessary. Weekly water changes of 30-50% should also be considered mandatory for the thriving of the species.

Water Conditions

The appropriate water conditions for this species are:

• Temperature: 20 – 28 °C
• pH: 5.0 – 7.5
• Hardness: 18 – 215 ppm

Diet

Metynnis spp. are opportunistic omnivores and feed on invertebrates, smaller fishes, algae, fruit, nuts, aquatic, and terrestrial plants.

In an aquarium setting, it’s important to offer regular meals of live and frozen foods along with high-quality dried products and a variety of vegetable matter. Good options to include in their diet are shelled peas, blanched courgette, spinach, and chopped fruit. Larger specimens may also consume chopped earthworm, praw

Behaviour and Compatibility

This species is typically not aggressive. However, it’s only suitable for very large tanks that contain robust, similarly-sized tankmates. There are plenty of appropriate choices, including many cichlids, catfishes, cyprinids, and other characins.

In nature, this species is often found swimming in large schools, and some individuals may become skittish or even aggressive if kept in insufficient numbers in the aquarium. Therefore, a group of six or more individuals should be the minimum considered. Keeping them in larger groups will result in a more natural-looking display and allow for interesting behavior as they interact with each other.

Sexual Dimorphism

Male specimens of this species have extended anterior anal-fin rays, resulting in a notched appearance of the fin at the center. They also have a dark spot above the origin of the pectoral fin, small dark spots in the dorsal fin, and dark distal margins to the unpaired fins. During the nuptial period, the ventral portion of the head becomes more prominent and displays an orange-red coloration.

Reproduction

There are no known records of this species being kept in aquaria. However, it has been introduced to the Lajes reservoir in southeastern Brazil, where it has demonstrated an opportunistic reproductive strategy. This reproductive strategy is characterized by a long period of reproduction, repeated spawning of relatively small batches of tiny eggs, and a relatively small adult body size.

Notes

References

1. Kner, R., 1858 – Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften. Mathematisch-Naturwissenschaftliche Classe 32(22): 163-168
   Zur Familie der Characinen. Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften.
2. Cope, E. D., 1878 – Proceedings of the American Philosophical Society 17(101): 673-701
   Synopsis of the fishes of the Peruvian Amazon, obtained by Professor Orton during his expeditions of 1873 and 1877.
3. Gomes, I. D., F. G. Araújo, R. J. Albieri, and W. Uehara, 2012 – Tropical Zoology 25(1): 2-15
   Opportunistic reproductive strategy of a non-native fish, the spotted metynnis Metynnis maculatus (Kner, 1858) (Characidae Serrasalminae) in a tropical reservoir in south-eastern Brazil.
4. Pavanelli, C. S., R. P. Ota and P. Petry, 2009 – Neotropical Ichthyology 7(2): 141-146
   New species of Metynnis Cope, 1878 (Characiformes: Characidae) from the rio Paraguay basin, Mato Grosso State, Brazil.
5. Reis, R. E., S. O. Kullander and C. J. Ferraris, Jr. (eds), 2003 – EDIPUCRS, Porto Alegre: i-xi + 1-729
   Check list of the freshwater fishes of South and Central America. CLOFFSCA.
6. Thompson, A. W., R. Betancur-R, H. López-Fernández, and G. Ortí, 2014 – Molecular Phylogenetics and Evolution 81: 242-257
   A time-calibrated, multi-locus phylogeny of piranhas and pacus (Characiformes: Serrasalmidae) and a comparison of species tree methods.