Ammoglanis natgeorum, a new miniature pencil catfish (Siluriformes: Trichomycteridae) from the lower Atabapo River, Amazonas, Venezuela

Abstract

A new species of the sand-dwelling catfish genus Ammoglanis is described from a marginal habitat of the lower Atabapo River, a left-bank blackwater tributary of the upper Orinoco River in Amazonas, Venezuela, adjacent to the border with Colombia. Ammoglanis natgeorum is distinguished from all congeners by trunk pigmentation pattern consisting of scattered ventral chromatophores concentrated around the analfin base and numerous additional meristic and anatomical characteristics. A. natgeorum is the second species of Ammoglanis described from the Orinoco River basin after Ammoglanis pulex, and several shared character states (e.g., eight total dorsal-fin rays, overall coloration pattern and presence of two finger-like papillae posterior to chin) suggest that it is more closely related to Ammoglanis obliquus (from the central Amazon basin) and A. pulex than to other congeners.

Two new miniature translucent catfish species of the rare genus Tridens (Siluriformes: Trichomycteridae) from the Madeira River basin, northern Brazil

“…Some species of Trichomycteridae are almost translucent in life, usually ones that inhabit patches of variable sizes of sand grains, such as members of the genus Ammoglanis Costa, 1994, from the Amazon and Araguaia basins ( e.g. , Costa, 1994; Henschel, Bragança et al ., 2020; Henschel, Lujan et al, 2020), Microcambeva , from the Atlantic Forest ( e.g ., Costa, Vilardo et al ., 2020), Sarcoglanis simplex Myers & Weitzman, 1966 (Myers & Weitzman, 1966) and Stauroglanis de Pinna, 1989, from the Amazon River basin (de Pinna, 1989; Zuanon & Sazima, 2004b) and Typhlobelus auriculatus de Pinna & Zuanon, 2013, from the Xingu River basin (de Pinna & Zuanon, 2013). Another siluriform nearly transparent in life is Mastiglanis asopos Bockmann, 1994, that is found within patches of sand in Amazonian rivers (Bockmann, 1994).…”

“…Furthermore, T. chicomendesi is so far only known from its type locality, increasing its vulnerability to any human‐related environmental disturbance. Considering the raising interest in the taxonomy and systematics of miniature siluriforms ( e.g ., Calegari et al ., 2014; Calegari & Reis, 2017; Carvalho et al ., 2016; Rocha et al ., 2012), and, more specifically, miniature trichomycterids ( e.g ., Henschel et al ., 2018; Henschel, Bragança et al ., 2020; Henschel, Lujan et al, 2020; de Pinna & Dagosta, 2022), even more advances in the knowledge of miniature species can be expected.…”

“…The rich natural histories underlying the striking diversity of these subfamilies led to a significant increase in the number of taxonomic works concerning the family, revealed by the description of 123 species of trichomycterids in the last 10 years (Fricke et al ., 2022). Nonetheless, these data hide an important collection and publication bias that affects studies focused on Trichomyteridae: most concern the diversity of trichomycterines from southern and southeastern Brazil ( e.g ., Costa et al ., 2022; Costa, Henschel et al ., 2020; Costa & Katz, 2021b; Reis et al ., 2022), with fewer efforts directed to members of the TSVSG‐clade, such as vandelliines (Dagosta & de Pinna, 2021; Henschel et al ., 2021; Henschel et al ., 2022; de Pinna & Dagosta, 2022) and sarcoglanidines (Costa et al ., 2019; Henschel, Bragança et al ., 2020; Henschel, Lujan et al, 2020; Canto et al ., 2022).…”

Osteology of Tucanoichthys tucano Géry and Römer, an enigmatic miniature fish from the Amazon basin, Brazil (Teleostei: Characiformes: Characidae)

“…Miniaturization, the evolution of extremely small adult body size, is a common phenomenon among freshwater fishes, especially in the Neotropics from where over 200 miniature species (≤26 mm in standard length [SL] sensu Weitzman and Vari 1988) are already known (Toledo-Piza et al 2014) and new species continue to be discovered annually (e.g., Henschel 2016;Mendonça et al 2016;Carvalho et al 2016Carvalho et al , 2017Calegari and Reis 2017;Pastana et al 2017;Valdesalici and Nielsen 2017;Caires and Toledo-Piza 2018;Camelier et al 2018;Jerep et al 2018;Abrahão et al 2019;Costa et al 2019;Ohara et al 2019;Henschel et al 2020aHenschel et al , 2020bMattox et al 2020Mattox et al , 2021Lima et al 2021;Vieira and Netto-Ferreira 2021). Miniaturization is frequently associated with one of two evolutionary processes: (1) a simple evolutionary decrease in body size resulting in miniature versions of larger close relatives (the so-called proportional dwarves of Gould [1971]); and (2) shifts in the relative timing of gonadal development in relation to somatic development (progenesis) resulting in species with developmentally truncated adults that resemble the larval stages of closely related taxa (so-called developmentally truncated miniatures of Rüber et al [2007]; ; Britz et al [2014]).…”