The Malabar danio (Devario malabaricus) is a species of freshwater ray-finned fish in the family Danionidae. Originating in Sri Lanka and the west coast of India, the fish has been circulated throughout the world through the aquarium trade.
The Malabar danio is found in tropical climates in a wide variety of waters, from mountain streams to small pools, but it prefers flowing waters. It is an active shoaling fish.
Taxonomy and etymology
The Malabar danio was described in 1849 as Perilampus malabaricus by the English physician and zoologist Thomas C. Jerdon with the type locality given as Chalakudy River, a river in the southern Indian state of Kerala. The specific epithet refers to this fact, as southern India was then known as Malabar. The species was at a time incorrectly considered a synonym of Devario aequipinnatus, which is a valid name for a different species.
Description
The Malabar danio is a relatively small (although comparatively large compared to many other species in the family), brightly colored fusiform fish. It is laterally compressed and has a superior mouth. It has a few orange longitudinal stripes on its flanks that may be broken up, and there are a few irregular vertical bars on the anterior half of their bodies, just in front of the longitudinal stripes. These bars are also orange. The dorsal fin sits posteriorly with 12 to 16 soft rays, and the anal fin contains 15 to 20 soft rays. The caudal fin is forked. The Malabar danio grows to a maximum length of 15 cm, but rarely exceeds 10 cm in a home aquarium.
The Malabar danio possesses a "danionin notch", which is an indentation of the lower jar characteristic of the family Danionidae. And like its congeners, the Malabar danio possesses a maxillary barbel and a P stripe (P standing for "pigment" here) that extends on the median caudal fin rays.
There are at least five other Sri Lankan Devario species, and the Malabar danio can be distinguished from them by its anteriorly bifurcated P stripe that originates at the caudal fin. Both sexes lack nuptial tubercles; however, males have epidermal tubercles located on the anterior rays of the pectoral fin.
(Figure 1. A simplified diagram of Devario fish. Numbers correspond to landmarks for measurements taken in a study. To be more precise, the Malabar danio occurs in lowland flood plains, hill streams, and mountain torrents up to 1,300 m above sea level, in various ecoclimatic zones whose waters vary in turbidity, shade, and disturbance levels.
Biology and life history
The Malabar danio often forms medium-sized shoals close to the water surface.
The Malabar danio is oviparous and is a group spawner.
Interestingly, the Malabar danio would release a chemical called 7-hydroxybiopterin when injured; when sensed, this signal alerts conspecifics to swim rapidly away. This alarm mechanism has also been observed in other cypriniform fish species.
Conservation status
The IUCN Red List listed the Malabar danio as Least Concern as of August 2019.