Vertical segregation of two species of Hyphessobrycon(Characiformes: Characidae) in the Cabiúnas coastal lagoon, southeastern Brazil

Metal Accumulation and Ion Regulation in the Fish Hyphessobrycon luetkenii Living in a Site Chronically Contaminated by Copper: Insights from Translocation Experiments

Fish living in the João Dias creek (southern Brazil) have to deal with trace-metal contamination in the long-term basis, as this aquatic environment has been historically impacted by copper mining activities. In order to survive in this harsh environment, the local biota had to develop adaptations related to pollution tolerance. The aim of this study was to test if biochemical mechanisms related to osmoregulation were among these adaptations, using translocation experiments. Water ionic and trace-metal compositions were measured in a nonmetal impacted site (NMIS) and in a metal impacted site (MIS) of this creek. Also, whole-body metal accumulation, ion concentration and branchial enzyme activity (Na,K-ATPase and carbonic anhydrase) were evaluated in Hyphessobrycon luetkenii. In both NMIS and MIS, fish were collected and immediately stored, kept caged or translocated from sites. The result shows that waterborne Cu was 3.4-fold higher at the MIS. Accordingly, animals that had contact with this site showed elevated whole-body Cu levels. Moreover, both translocated groups showed elevated Na,K-ATPase activity. Additionally, fish translocated from the NMIS to the MIS showed lower carbonic anhydrase activity. These findings indicate that H. luetkenii chronically or acutely exposed to naturally elevated waterborne Cu showed a rapid Cu bioaccumulation but was unable to readily excrete it. Moreover, classic Cu osmoregulatory toxicity related to Na,K-ATPase inhibition was not observed. Conversely, impacts in ammonia excretion related to carbonic anhydrase inhibition may have occurred.

Resource use by two electric fishes (Gymnotiformes) of the National Forest Saracá-Taquera, Oriximiná, Pará

ABSTRACT Fishes of the order Gymnotiformes have high diversity of oral and head morphology, which suggests trophic specializations within each clade. The aim of this study was to describe resource use patterns by two fish species (Gymnorhamphichthys rondoni and Gymnotus coropinae) in the National Forest Saracá-Taquera, Oriximiná - Pará, analyzing microhabitat use, diet composition, feeding strategies, niche breadth and niche overlap. Stomach contents of 101 individuals (41 G. rondoni and 60 G. coropinae), sampled in 23 headwater streams were analyzed and volume of food items was quantified to characterize their feeding ecology. Gymnorhamphichthys rondoni was captured mainly on sandy bottoms, whereas G. coropinae in crevices. Both species had a zoobenthivorous diet and consumed predominantly Sediment/Detritus and Diptera larvae, but also included allochthonous prey in their diet. These species had high niche overlap, with small variations related to the higher consumption of Ceratopogonidae larvae by G. rondoni and of Chironomidae larvae by G. coropinae. Both species had a generalist feeding strategy, but G. coropinae had a broader niche breadth. Our results demonstrate that G. rondoni and G. coropinae occupy different microhabitats but rely on similar food resources.

A new species of Hyphessobrycon Durbin(Characiformes: Characidae) from the rio Juruena basin, Central Brazil, with notes on H. loweae Costa & Géry

A new species of Hyphessobrycon, H. peugeoti, is described from the middle portions of the rio Juruena drainage, upper rio Tapajós basin, Mato Grosso State, Brazil. It can be distinguished from all congeners, with the exception of H. loweae and H. heliacus, by a filamentous elongation of the dorsal fin and the approximately straight margin of the anal fin in adult males. It can be distinguished from both H. loweae and H. heliacus by an overall red coloration in life (vs. a golden coloration in life in the latter). Additionally, it can be distinguished from H. heliacus by the lack of chevron-like dark markings along the midline (vs. presence of chevron-like dark-markings in H. heliacus), and from H. loweae by the presence of only five horizontal scale rows between the dorsal-fin origin and the lateral line (vs. 6-7 in H. loweae), and the higher number of branched anal-fin rays (21-24, modally 22, vs. 17-21, modally 20, in H. loweae). Additional meristic, morphometric, and distributional data are provided for Hyphessobrycon loweae, including its first record in the rio Araguaia/Tocantins basin. Comments on a putative monophyletic group including H. peugeoti, H. loweae, H. heliacus, H. elachys, and H. moniliger are presented.

Microhabitat use by Phalloceros harpagos Lucinda (Cyprinodontiformes: Poeciliidae) from a coastal stream from Southeast Brazil

The size-related microhabitat use of Phalloceros harpagos Lucinda, 2008 from Mato Grosso stream (Saquarema - RJ) was examined. We analyzed, during 8.3 h of underwater observation, a 200 m long reach in the upper Mato Grosso stream, quantifying the following microhabitat descriptors: (i) distance from the stream bank, (ii) water column depth, (iii) occurrence on riffle, pool or run mesohabitat, (iv) water velocity, (v) substratum, and (vi) subaquatic vegetal cover. Microhabitat selectivity was analyzed by comparing the microhabitat used by fish and the microhabitat available in the study site. Complementary analyses, based in the Ivlev Electivity Index were applied in order to test selectivity for the microhabitat use. We did not found differences in the microhabitat used by juvenile and adult individuals. Phalloceros harpagos was selective for five among the six analyzed microhabitat descriptors. The occurrence of Phalloceros in the studied stream was limited to shallow pools, close to the river bank, with low water velocities and mud substratum. Vegetal cover was not an important factor in the occurrence of the studied species.