Description of Neblinichthys brevibracchium and N. echinasus from the upper Mazaruni River, Guyana (Siluriformes: Loricariidae), and recognition of N. roraima and N. yaravi as distinct species

Abstract

Neblinichthys brevibracchium and N. echinasus are new sympatric species from upland tributaries of the Mazaruni River (Essequibo River basin) of Guyana. These two new species are the first Neblinichthys reported from Guyana. Adult males of both new species have short pectoral-fin spines and several series of hypertrophied odontodes covering the entire dorsal surface and along the entire edge of the snout. They are distinguished from each other by dorsal-fin base length/standard length (18.1-22.8% in N. brevibracchium vs. 24.3-27.0% in N. echinasus), dorsal-anal distance/SL (13.7-18.3% in N. brevibracchium vs. 11.9-12.5% in N. echinasus), by having the snout decreasing in steep arc just anterior to eyes and then flattening in area anterior of nares in N. brevibracchium vs. the snout tapering shallowly and continuously from eyes to snout tip in N. echinasus); and by having the adpressed dorsal fin reaching the anterior preadipose plate in N. brevibracchium (vs. not reaching anterior preadipose plate in N. echinasus). They are distinguished from all congeners by lacking odontodes on the opercle (vs. odontodes present); and by completely lacking an iris operculum (vs. congeners with small iris operculum present or at least dorsal portion of iris flat instead of rounded). Neblinichthys echinasus and N. brevibracchium differ from all congeners by having a spotted or vermiculated pigment pattern on the abdomen (vs. abdomen plain); in N. echinasus the abdomen is darkly pigmented with bold white spots and in Neblinichthys brevibracchium the abdomen is light-colored with gray spots and vermiculations. Neblinichthys brevibracchium and N. echinasus differ from N. roraima by having one to two preadipose plates (vs. four or more). New observations revealed Neblinichthys roraima and N. yaravi to be distinct, with N. roraima having four or more preadipose plates and N. yaravi having one or two. Both are present in the upper río Caroní, an Orinoco tributary that drains the slopes of Mount Roraima and other mountains of the Pacaraima Range in Venezuela and interdigitates with headwaters of the Mazaruni River.Neblinichthys brevibracchium y N. echinasus son especies nuevas simpátricas que viven en las cabeceras del río Mazaruni (cuenca del río Essequibo) en Guyana. Estas dos especies nuevas son las primeras Neblinichthys registradas de Guyana. Se distinguen uno del otro por la relación de la longitud de la base de la aleta dorsal/SL (18,1-22,8% in N. brevibracchium vs. 24,3-27,0% en N. echinasus), por la distancia dorsal-anal/SL (13,7-18,3% en N. brevibracchium vs. 11,9-12,5% en N. echinasus), por el hocico que declina suavemente desde los ojos hacia la punta (vs. hocico que declina abruptamente desde los ojos hasta la punta) y en tener una aleta dorsal que alcanza la placa pre-adiposa anterior cuando se aprieta al cuerpo (vs. no alcanzando la placa pre-adiposa anterior). Se distinguen de todos sus congéneres por carecer de odontodos en el opérculo, y por la falta del iris opérculo en el ojo (vs. presencia de un iris opérculo pe...

Phylogenetic diagnosis and expanded description of the genus Mazarunia Kullander, 1990 (Teleostei: Cichlidae) from the upper Mazaruni River, Guyana, with description of two new species

“…In 2008, a joint expedition by the Royal Ontario Museum and the University of Guyana collected specimens of both M. mazarunii and of two other cichlid species that were clearly undescribed but whose generic assignment was not immediately obvious. Molecular phylogenetic analysis (López-Fernández et al, 2010) resulted in a strongly monophyletic grouping of all three species, and this clade in turn was well supported as sister to the lowland genus Guianacara. Because the material available for description of M. mazarunii was limited to two specimens, Kullander (1990) was understandably cautious, and preferred not to damage the specimens rather than perform an extensive anatomical investigation of the new genus.…”

“…Counts of fin rays, scales, and gill rakers were made under a dissecting microscope. Scale row nomenclature follows Kullander (1996), osteological and squamation nomenclature follows López-Fernández et al (2005) and references to higher-level classification are based on López-Fernández et al (2010). Counts are given as the observed count followed by the number of individuals with that value in parenthesis; counts in the holotype, when appropriate, are marked with an asterisk.…”

“…The morphological dataset of 136 characters for 38 taxa from López-Fernández et al (2005) was expanded to 43 taxa that include all three species of Mazarunia plus Guianacara dacrya Arbour & López-Fernández, 2011 and G. owroewefi Kullander & Nijssen, 1989 as a way to increase representation of the putative sister group of Mazarunia. A molecular counterpart to the morphological dataset consisted of sequences for five genes (3 mitochondrial: 16S, ND4, Cytochrome b, and 2 nuclear: S7 intron 1 and RAG2) from 56 taxa analyzed by López-Fernández et al (2010). The molecular dataset included taxa from all lineages of the tribes Geophagini and Chaetobranchini in addition to three species of Cichla Bloch & Schneider, 1801 (Cichlini), one of Retroculus Eigenmann & Bray, 1894 (Retroculini) and one each of the genera Mesonauta Günther, 1862, Hoplarchus Kaup, 1860 (Heroini), Astronotus Swainson, 1839 (Astronotini) and Cichlasoma Swainson, 1839 (Cichlasomatini) as representatives of all other lineages of Neotropical cichlids.…”

“…The molecular dataset included taxa from all lineages of the tribes Geophagini and Chaetobranchini in addition to three species of Cichla Bloch & Schneider, 1801 (Cichlini), one of Retroculus Eigenmann & Bray, 1894 (Retroculini) and one each of the genera Mesonauta Günther, 1862, Hoplarchus Kaup, 1860 (Heroini), Astronotus Swainson, 1839 (Astronotini) and Cichlasoma Swainson, 1839 (Cichlasomatini) as representatives of all other lineages of Neotropical cichlids. Detailed descriptions of morphological characters and their coding are given by López-Fernández et al (2005) and Appendix 1; methods for sequencing and aligning the molecular dataset are detailed in López-Fernández et al (2010). The molecular and morphological datasets were concatenated such that all partitions could be analyzed in a total evidence framework.…”

“…Thus the original description of M. mazarunii relied heavily on external anatomical characters and on what was possible to glean from radiographs, but no detailed osteological analysis could be performed. Taking advantage of the newly collected material, we further test the monophyly of Mazarunia and its relationship to Guianacara by incorporating morphological characters to the molecular dataset of López-Fernández et al (2010). We describe morphological synapomorphies of the genus, provide a complement to the original description of M. mazarunii, and describe the two additional species.…”