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Corydoras bilineatus Knaack, 2002

An excerpt from the original description by Joachim Knaack published in: Aquaristik aktuell 4/2002 p. 50-56; translated and amended from German by Stephan M. Tanner.

Classification:     

Corydoras bilineatus belongs to the Corydoras elegans group sensu Nijssen & Isbrucker consisting of C. elegans, C. hastatus, C. undulatus, C. latus, C. pygmaeus, C. guapore, C. nanus, and C. gracilis, as well as C. napoensis.

Description:

This short-nosed species presents with an obvious sexual dimorphism in size and coloration that already becomes apparent in juveniles at 10 mm standard length (SL). Females become considerably larger (max 55 mm SL) and appear grayer in color. Males are smaller (max 44 mm SL) with a more contrastful pattern due to the two name giving lateral stripes that can vary from white to pale yellow. These are also visible in females but appear more greenish-gray. The dorsal fin in males usually shows a black blotch that can vary in size and form.

Habitat:

Corydoras bilineatus was collected in Bolivia, Departmento Santa Cruz, Cochabamba and Beni, system of the upper Rio Marmor-14-18 degree S and 62-68 degree W at an elevation of 161-327 m above sea level. The typus locality was a large standing pool in October 2001 with dense floating plant cover of Pistia stratiotes, Eichhornia, and Salvinia. The roots of Pistia serve as substrate for egg laying. C. bilineatus from the typus locality live in relatively cold-water temperatures of only 18-22 C (64-72 F). In contrast, specimens from the Northeastern low lands (Trinidad) live in temperatures that about 3 C/F higher. The pH ranges from 6.04-8.40 with 20-1000 mS depending on locality. C. bilineatus occurs in rather large groups that contain hundreds of individuals.

Aquarium keeping:

C. bilineatus is an attractive and very active aquarium fish that prefers densely planted tanks with not too bright lighting. Given their natural behavior these fish should be kept in groups of no less than 8-10 individuals. To induce breeding the temperature should be lowered 2-3 C/F for 2-3 months. A fat-rich diet and increasing frequency of water changes with slightly warmer water will induce spawning which is quite productive. The numerous eggs are preferably stuck to swimming plant roots or egg mobs. Young C. bilineatus grow fast and reach 12 mm SL within four weeks. C. bilineatus eats any stable diet but prefers worm food such as tubifex, grindal, small mosquito larvae (blood worms), and brine shrimp, which can be offered frozen or live.

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