Corydoras bethanae

Natural history notes. Corydoras bethanae may be found in blackwater streams that drain into the predominantly whitewater río Blanco (Fig. 8 A), although the UK aquarist Mark Breeze (pers. comm.) states that in the dry season he found small clearwater tributary streams near the confluence with the río Tapiche (Fig. 8 B). Those streams had a sand substrate with hardly any leaf litter and just overhanging terrestrial plants. Corahua et al. (2015) found several Corydoras species in shallow, lotic blackwater streams or flooded forests that flowed into the middle reaches of the río Blanco, that were low in pH (5.4 – 5.5), electrical conductivity (4.8 – 8.9 μs / cm), temperature of 25 degrees Centigrade, with abundant organic detritus, and white sand. A site in the lower region, closer to the type locality of Corydoras bethanae, was the same except it was lentic, the pH ranged from 4.1 – 5.6, and the electrical conductivity was 29.5 – 41.0 μs / cm. Corydoras granti was found by Corhua et al. (2015) in this location (misidentified as Corydoras arcuatus); another species with an arched dark body band. Corahua et al. (2015) list at least eight species from the río Blanco, and in addition to those, information from fish collectors indicates that the following Corydoras can also be found in the río Blanco system: Corydoras coriatae Burgess, 1997, C 138 (which is superficially similar to Corydoras bethanae), and CW 073. Grant (2020) discussed curious behavior exhibited by Corydoras bethanae when in the aquarium. All corydoradins appear to be able to maintain their position in the water column, above the substrate, by using a combination of body movement and fin movement. They usually to do this when maneuvering while performing definite activities e. g., avoiding another fish or predator, feeding, spawning etc. In the aquarium C. bethanae tend to hover regularly and for long periods of time, apparently not related to any particular activity; a behavior that has not been reported for other lineage 8 Corydoras. The pale transversal bar from fourth dorsolateral body plate to posterolateral margin of cleithrum corresponds with a large ligament attached dorsally to the transverse process of dorsal pterygiophore and ventrally to the posterior laminar expansion of the first rib, which itself is connected to the anterior external process of basipterygium. Such condition may have some effect on the ability to hover in the water column, especially by offering a strong support to pelvic fins, which along with pectoral fins seem to be the main fins responsible for keeping them lifting above the substrate. Videos of the holotype and some BMNH paratypes hovering can be seen at: https: // www. youtube. com / watch? v = hcg 45 PlwHjs and https: // www. youtube. com / watch? v = v 6 p 1 hUdls 54 There is a single record of successful spawning of this species, in which the water parameters were pH 6, Total Dissolved Solids (TDS) 82 ppm, and temperature 22.4 ° C (Petersson, 2020).