Pimelodella bockmanni

description

The Colombian records of Pimelodella bockmanni come from terra firme forest streams, tributaries to the main channel of the Amazon River in Colombia, in the southernmost extreme of the country, known regionally as Trapecio Amazónico (Fig. 1). These specimens were originally identified as P. geryi Hoedeman, 1961 by Arbeláez et al. (2008), possibly due to their similar general appearance and pigmentation pattern (Fig. 2). However, Colombian specimens differ from P. geryi by their supraoccipital process not reaching the nuchal plate (vs. in contact), adipose fin longer (35.2 – 40.1 % in SL vs. 23.8 – 25.1 %), and upper lobe of caudal fin longer (vs. lower lobe longer) (Hoedeman 1961; Slobodian et al. 2017). Pimelodella bockmanni was recently described from main right tributaries of the Madeira River in Brazil (Slobodian & Pastana 2018). Although the type series of P. bockmanni was not examined directly, we found that our specimens agree with the morphological information provided in its original description (Slobodian & Pastana 2018), except by having a longer upper lobe of the caudal fin (39.0 – 51.0 % of SL vs. 25.8 – 34.8 %), which can be attributed to the larger size of the examin

New records of Pimelodella (Siluriformes, Heptapteridae) from Colombia for the Amazon River basin, and redescription of P. serrata

distribution

The geographic distribution of Pimelodella bockmanni seems to conform to the Central Blackwater Amazon pattern proposed by Dagosta & de Pinna (2019), which connects the two hydrographic systems with known records of the species, i. e. Madeira and western Amazon (above the mouth of the Rio Negro). Although the Amazon River is a typically white-water system in the Amazonas / Solimıes region, the streams where Colombian specimens were collected drain heavily leached soils, and their waters are poor in nutrients and dissolved solids (Arbeláez et al. 2008). Detailed data on the type of water corresponding to the localities where the type series originated will allow confirmation of this biogeographic categorization. Pimelodella serrata (Fig. 3), is recorded for the first time from Colombia, based on specimens coming from flooded areas (laguna Yahuarcaca) and terra firme streams (quebrada La Arenosa), draining directly to the main channel of the Amazon River in Colombia (Fig. 1). This species was described for San Joaquín, a locality drained by the Machupo River, a tributary of the Iténez River (upper Guaporé drainage) in Bolivia, and was distinguished by four characters in the dichotomo

New records of Pimelodella (Siluriformes, Heptapteridae) from Colombia for the Amazon River basin, and redescription of P. serrata