Monthly Archives: June 2020

A New Miniature Species of Acanthobunocephalus (Silurifomes: Aspredinidae) from the Lower Purus River Basin, Amazon Basin, Brazil

Tiago P. Carvalho and Roberto E. Reis

A second species of Acanthobunocephalus is described from tributaries of the lower Purus River in the Amazon Basin, Brazil. Acanthobunocephalus scruggsi, new species, is distinguished from all other aspredinid species by its reduced number of fin rays: four pectoral-fin rays (vs. five or more), two dorsal-fin rays (vs. three or more, except Amaralia hypsiura), five pelvic-fin rays (vs. six), four to five anal-fin rays (vs. six or more, except Bunocephalus verrucosus), and nine caudal-fin rays (vs. 10, except Hoplomyzontinae, Amaralia, Platystacus, Bunocephalus chamaizelus, and Bunocephalus minerim). Osteological aspects of the new species of Acanthobunocephalus are described using cleared and stained specimens and high-resolution x-ray computed tomography (HRXCT), and compared with Acanthobunocephalus nicoi and other aspredinids. Generic assignment is based on putative apomorphic shared features and a morphological diagnosis for Acanthobunocephalus is presented.

Link: https://www.asihcopeiaonline.org/doi/abs/10.1643/CI-19-309

Paratype of Acanthobunocephalus scruggsi, INPA 42229, 20.6 mm SL, Amazonas, Tapauá , Igarapé dos Caetanos, tributary to Rio Ipixuna. Scale bar = 10 mm.

HRXCT model of skull and anterior body of Acanthobunocephalus scruggsi, holotype, INPA 57946, 21.7 mm SL. (A) Dorsal view, (B) lateral view, and (C) ventral view. br = branchiostegal rays; cl = cleithrum; cv=parapophysis of complex vertebrae; db=dorsal blade of complex vertebrae; den=dentary; df =dorsal fin; dp=distal portion of pectoral-fin spine; fr = frontal; hc = hemal canal; me = mesethmoid; mnp=middle nuchal plate; mx=maxilla; op=opercle; p=premaxilla; pcl = posterior process of cleithrum; pfs = pectoral-fin spine; po = preopercle; pp =proximal portion of pectoral-fin spine; psc = posterior process of scapulocoracoid; pso= parieto-supraoccipital; pto=pterotic; pv5 = parapophysis of fifth vertebra; r6 = sixth rib; sco = scapulocoracoid; scl=posttemporal-supracleithrum; spo=sphenotic; tf=temporal fontanel. Limits between selected bones are highlighted in black.

Geographic distributions of species of Acanthobunocephalus. Circles =A. nicoi, squares = A. scruggsi. Black symbols refer to type localities. Amazon River basin highlighted in green.

Taxonomical study of Trichomycterus (Siluriformes: Trichomycteridae) from the Ribeira de Iguape River basin reveals a new species recorded in the early 20th century

Laura M. Donin | Juliano Ferrer | Tiago P. Carvalho

Abstract

A new species of Trichomycterus endemic to the Ribeira de Iguape River basin, southeastern Brazil, was studied based on morphological and molecular evidence. This species had an outer layer of coloration composed of scattered, round, black or dark‐brown spots smaller or equivalent in size to the circumference of the eye; eight pectoral‐fin rays; 28–29 opercular odontodes; 54–56 interopercular odontodes; and supraorbital line of the laterosensory system not interrupted, with pores s2 absent. Two other species of Trichomycterus from the Ribeira de Iguape River basin are recorded, and their taxonomic status is discussed: Trichomycterus alternatus and Trichomycterus jacupiranga were not differentiated using molecular analysis but may be consistently distinguished based on morphology. The phylogenetic relationships of the co‐occurring species, T. alternatus and Cambeva zonata , were inferred using mitochondrial data, reinforcing the taxonomic status of these recently revised species that have a complex taxonomy. In addition, a new combination for Trichomycterus taroba with its inclusion in the genus Cambeva is recommended.

Link: https://onlinelibrary.wiley.com/doi/abs/10.1111/jfb.14278

FIGURE. Colour variation in live specimens of Trichomycterus lauryi. (a) UFRGS 24536, 60.7 mm LS, córrego do Queimado; (b) UFRGS 24537, 77.0 mm LS, rio Betari; (c) UFRGS 24537, 68.9 mm LS, rio Betari; Ribeira de Iguape River basin

FIGURE. Distribution of Trichomycterus species in Ribeira de Iguape River and neighbouring coastal basins. Red circles: Trichomycterus lauryi; blue star: Trichomycterus jacupiranga and type locality of T. lauryi; yellow triangles: Trichomycterus alternatus; yellow pentagon: paratype of Cambeva zonata (FMNH 58572) presently identified as T. alternatus; green square: C. zonata

Relationship between diet and pharyngeal jaw morphology of Crenicichla species (Cichliformes: Cichlidae) in streams from Uruguay and Jacuí basins, Southern Brazil

Fernanda Kuhn, Mayara Pereira Neves, Karine Orlandi Bonato & Clarice Bernhardt Fialho

Abstract

Cichlidae have a magnificent ecological versatility that provides the species to explore many trophic niches, and behavioural biology. This versatility was achieved by modifications in the cranial and pharyngeal apparatus of cichlids. Accordingly, we aim to examine the relationships between pharyngeal morphology and diet of three species of the genus Crenicichla. We analysed the stomach contents and the morphology (through the geometric morphometric and teeth types) of their lower pharyngeal jaws (LPJ). We tested the hypothesis that LPJ morphology predicts the diet of Crenicichla species in streams. Our results indicated that the diet and the patterns of pharyngeal jaws were different among the species of Crenicichla, mainly the posterior process of the LPJ, the region of muscle insertion of LPJs with the neurocranium and the curvature of LPJ. Variation among the lower pharyngeal jaw shapes was shown to be directly associated with the use of food resources. Crenicichla species had a carnivorous diet based on fish and invertebrates (Aegla and aquatic insects). Higher fish consumption was observed in species with elongated lateral process in the LPJ and larger numbers of teeth, mainly recurved and conical unicuspid and bicuspid teeth (C. scottii and C. lepidota). On the other hand, higher consumption of Aegla was associated with a robust LPJ and molariform teeth (C. punctata). The total number of teeth was positively correlated with higher fish consumption. In addition, our results point to the need for investigations about spatial-temporal variations in Crenicichla diets to understand this group’s success in several freshwater environments

Link: https://link.springer.com/article/10.1007%2Fs10641-020-00963-y

a Live representatives of C. lepidota (1), C. punctata (2), and C. scottii (3); b ventral view of lower pharyngeal jaw; c summaries of their stomach contents. Aquatic insects; Terrestrial insects; Other aquatic invertebrates; Aegla; Fish; Plant remains; ■ Detritus

Ventral and lateral view of lower pharyngeal jaw and dentition of 1C. lepidota; 2C. punctata; 3C. scottii from streams, Upper Jacuí and Ibicuí sub-basins, Southern Brazil. Teeth types: a) Bicuspid; b) Recurved unicuspid; c) Conical unicuspid; d) Molariform

A new species of Hemiodus Müller (Characiformes: Hemiodontidae) from the lower Rio Xingu, Brazil

Ivanilza Da Silveira Silva, Acácio Freitas Nogueira, Andre Luiz Netto-Ferreira, Alberto Akama & Guilherme Moreira Dutra,

Abstract
A new species of Hemiodus is described from the Rio Xingu basin, Pará, Brazil. It is distinguished from congeners by the combination of presence of a dark longitudinal stripe extending from head to tip of lower caudal-fin lobe, an oblique blotch on dorsal-fin, 9–11 scale rows above lateral line, 58–66 perforated lateral line scales, and 17–20 circumpeduncular
scales. Comments on the conservation status of the new species, as well as its relationships among Hemiodus species, are made.

Link: https://www.biotaxa.org/Zootaxa/article/view/zootaxa.4751.1.11

Upper : Hemiodus tucupi, MPEG 36362, holotype, 66.5 mm SL, Igarapé Bacajaí, Rio Xingu basin, Pará, Brazil.        Lower: Hemiodus tucupi, live specimen, paratype, INPA 43494, 62.7 mm SL, Rio Xingu at middle portion of Volta Grande, Pará, Brazil. Photo by Mark Sabaj.

Morphological traits correlated with resource partitioning among small characin fish species coexisting in a Neotropical river

Rosilene Luciana Delariva and Mayara Pereira Neves

Abstract

Body shape variation should play a central role in determining the feeding ability of a fish species. We tested whether variations in feeding resource use of sympatric and closely related fish species could be explained by differences in ecologically relevant metrics, such as body morphology, trophic apparatus or combinations thereof. Fish were sampled at 14 sampling sites from Pelotas River and tributaries, Upper Uruguay, Brazil. The stomach contents of five species of Characidae (Astyanax and Bryconamericus ) were analysed by the volumetric method. A geometric morphometric approach was used together with internal morphological traits to predict their patterns of prey use. Significant differences in body depth, snout and caudal peduncle lengths were found. Concomitant pronounced variations were verified to occur among species in structures related to digestion and absorption. Increased numbers of cusps, more pyloric caeca and higher intestinal coefficient values were observed in species that consumed greater proportions of plants. The opposite trends occurred in species that consumed greater proportions of insects. Mixed linear models indicated that the characin species differed significantly in the use of algae, aquatic insects, terrestrial insects, plant remains/seeds and detritus. Dietary differences reflected in low trophic niche overlap. Partial least squares regression results indicated strong correlations between morphological divergences and the corresponding variations in species diet. These outcomes combined confirm that the morphological traits that best enables the exploration of certain resource were an important factor in the resource‐related divergence and were the underlying reasons for these species’ respective feeding modes.

Link: https://onlinelibrary.wiley.com/doi/abs/10.1111/eff.12540

Study area and sampling sites in the main channel of the Pelotas River (C) and its tributaries (T), Upper Uruguay ecoregion, Brazil. The pie charts represent the numerical abundance (%) of the species

Principal component analysis (PCA) results showing biologically important differences in body shape among characin fish species in the Pelotas River basin, Upper Uruguay ecoregion. Thin-plate spline transformations of landmark positions represent the extreme transformations of body shape measurements along the PC axes