Ituglanis agreste, a new catfish from the rio de contas basin, northeastern Brazil (siluriformes: trichomycteridae)

Ituglanis agreste, a new species of catfish, is described from a tributary stream of the rio Gongogi drainage, rio de Contas basin, Bahia State, northeastern Brazil, from a transition area between the Atlantic Rain Forest and the semi-arid Caatinga savanna. This species is distinguished from its congeners by the following characters: elongate interopercle plate with high number of odontodes (26-30), high number of ribs (5-6), fewer vertebrae (36), number of branchiostegal rays (7), number of pectoral-fin rays (i,6) and absence of s1 pore. Comparisons with other Ituglanis species and putative plesiomorphic characters are presented. Some comments about conservation of Ituglanis species from northeastern Brazil are also made.

Ituglanis agreste, espécie nova, é descrita de um tributário da drenagem do rio Gongogi, bacia do rio de Contas, Bahia, nordeste do Brasil, de uma área de transição entre dois biomas, a Caatinga e a Mata Atlântica. Esta espécie distingue-se de todas as demais espécies do gênero pelas seguintes características: placa interopercular alongada com elevado número de odontódeos (26-30), número elevado de costelas (5-6), número reduzido de vértebras (36), número de raios branquiostégios (7), número de raios da nadadeira peitoral (i,6), e ausência do poro s1. Comparações com outras espécies de Ituglanis e a presença de supostos caracteres plesiomórficos são apresentados. Alguns comentários sobre conservação das espécies de Ituglanis do nordeste do Brasil também são feitos.

Parotocinclus seridoensis, a new hypoptopomatine catfish (Siluriformes: Loricariidae) from the upper rio Piranhas-Açu basin, northeastern Brazil

A new species of Parotocinclus is described from the upper rio Piranhas-Açu basin, northeastern Brazil. The new species differs from all its congeners, except P. bidentatus, P. muriaensis (both from rio Paraíba do Sul basin, southeastern Brazil), and P. spilurus (rio Jaguaribe basin, northeastern Brazil) by presenting the adipose fin rudimentary or absent. The new species differs from P. bidentatus, P. muriaensis, and P. spilurus mainly by presenting the abdomen region extensively naked, with few reduced rounded dermal platelets between the pectoral girdle and the anus. Parotocinclus seridoensis is probably an endemic species of the semi-arid Caatinga, region where the genus presents high species richness.

Uma espécie nova de Parotocinclus é descrita da bacia do alto rio Piranhas-Açu, nordeste do Brasil. A espécie nova difere de todas as congêneres, exceto P. bidentatus, P. muriaensis (ambas da bacia do rio Paraíba do Sul, sudeste do Brasil) e P. spilurus (bacia do rio Jaguaribe, nordeste do Brasil), por apresentar nadadeira adiposa rudimentar ou ausente. A espécie nova difere de P. bidentatus, P. muriaensis e P. spilurus principalmente por apresentar no abdômen extensas áreas nuas, com poucas placas dérmicas reduzidas e arredondadas entre a cintura peitoral e o ânus. Parotocinclus seridoensis é provavelmente uma espécie endêmica da Caatinga semi-árida, região onde o gênero apresenta elevada riqueza de espécies.

Ground-foraging ants (Hymenoptera: Formicidae) and rainfall effect on pitfall trapping in a deciduous thorn woodland (Caatinga), Northeastern Brazil

The semi-arid Caatinga is the fourth largest biome of Brazil, which biota still remains one of the most poorly known, especially with regard to invertebrate groups. In this study, a ground-foraging ant assemblage was surveyed during one year and the effect of rainfall on pitfall trapping was assessed. The study was performed in an area located in the municipality of Pentecoste (3º48’ S - 39º20’ W), in the State of Ceará. A 200m transect with 20 equidistant sampling points was established. Transect sampling was performed once a month during 12 months, over the period August 2008-August 2009. At each sampling point, a pitfall trap partially filled with a mixture of ethanol and monoethylene glycol was placed at the beginning of each month and remained in the field for seven days. 39 species belonging to six subfamilies and 19 genera, plus two unidentified species, were collected, with Pheidole (10 spp.) and Camponotus (8 spp.) being the taxa with the most species. 23 species were frequent, being found in more than 50% of the 12 transect samplings. Five species had an intermediate frequency (25 to 50%), while 13 were relatively infrequent (less than 25%). Most of the species (22) showed low occurrence, being found in less than 10% of the 240 samples (20 samples each month, during 12 months). Only five species were collected in more than 50% of the samples, those species being also responsible for most of the total abundance (number of captured individuals of all species) observed each month. The speciesaccumulation curves (observed and estimated) indicated that sampling sufficiency was attained, and that about 92% of the estimated ground-foraging ant fauna had been collected. 40 and 29 species were collected in the dry and rainy season, respectively, with monthly species richness ranging from 13 to 28. The total ant abundance showed a drastic decrease during the rainy season, and a negative linear correlation was found between rainfall and total ant abundance (R2=0.68). A similar negative linear correlation was found for species occurrences against rainfall (R2=0.71), and for mean number of species per pitfall trap against rainfall (R2=0.71). However, some species showed equal abundance, occurrence and mean number of individuals per pitfall trap in both seasons, while others showed a much higher abundance and occurrence during the rainy season. Pitfall trapping as a method to sample ground-foraging ant assemblage of the Caatinga biome and potential factors responsible for lower pitfall trap performance during rainy season are discussed. Rev. Biol. Trop. 59 (4): 1637-1650. Epub 2011 December 01.

La Caatinga semiárida es el cuarto bioma más grande de Brasil. Pese a ello, es también el bioma brasileño cuya biota continúa siendo la más pobremente estudiada, especialmente en lo que se refiere a grupos de invertebrados. En este estudio se examinó durante un año el grupo de hormigas que forrajean en el suelo de un área de Caatinga y se evaluó el efecto de la lluvia sobre las trampas de caída. El estudio se llevó a cabo en un área del municipio de Pentecoste (3º48’ S - 39º20’ W), estado de Ceará. Se estableció un transecto de 200m con 20 puntos de muestreo equidistantes. El muestreo del transecto se realizó mensualmente durante 12 meses, entre Agosto 2008-Agosto 2009. En cada punto de muestreo se colocó al principio de cada mes una trampa de caída parcialmente llena con una mezcla de etanol y monoetilenglicol y se mantuvo en el campo durante siete días. Se recogieron 39 especies pertenecientes a seis subfamilias y 19 géneros, además de dos especies sin identificar, siendo Pheidole (10 spp) y Camponotus (8 spp) los taxones con más especies. Veintitrés especies fueron frecuentes, se registraron en más del 50% de los 12 transectos muestreados. Cinco especies tuvieron una frecuencia intermedia (25 a 50%), mientras 13 fueron relativamente infrecuentes (menos del 25%). La mayoría de las especies (22) mostraron una presencia baja, encontrándose en menos del 10% de las 240 muestras (20 muestras cada mes durante 12 meses). Sólo cinco especies fueron recogidas en más del 50% de las muestras, fueron además responsables de casi toda la abundancia total (número de individuos capturados de todas las especies) mensual. Las curvas de acumulación de especies (observadas y estimadas) indicaron que se consiguió un muestreo suficiente y que se había recogido cerca del 92% de la fauna estimada de hormigas terrícolas forrajeras. Se recogieron 40 y 29 especies durante las estaciones seca y lluviosa, respectivamente, con una riqueza de especies mensual entre 13 y 28. La abundancia total de especies mostró una disminución drástica durante la estación de lluvias, y se encontró una correlación linear negativa entre la pluviosidad y la abundancia total de hormigas (R2=0.68). Una correlación linear negativa similar se encontró entre la ocurrencia de especies y la pluviosidad (R2=0.71), y entre el número medio de especies por trampa de caída y la pluviosidad (R2=0.71). Sin embargo, mientras se observó que algunas especies tenían la misma abundancia, presencia, y número medio de individuos por trampa de caída en ambas estaciones, otras tenían una abundancia y presencia mucho mayor durante la estación lluviosa. Se discute el uso de trampas de caída como método para muestrear el grupo de hormigas que forrajean en el suelo del bioma de la Caatinga, así como los factores potenciales responsables del rendimiento más bajo de las trampas de caída durante la estación lluviosa.