William Severi

Caatinga revisited: ecology and conservation of an important seasonal dry forest.

Besides its extreme climate conditions, the Caatinga (a type of tropical seasonal forest) hosts an impressive faunal and floristic biodiversity. In the last 50 years there has been a considerable increase in the number of studies in the area. Here we aimed to present a review of these studies, focusing on four main fields: vertebrate ecology, plant ecology, human ecology, and ethnobiology. Furthermore, we identify directions for future research. We hope that the present paper will help defining actions and strategies for the conservation of the biological diversity of the Caatinga.

Water quality, phytoplankton composition and growth of Litopenaeus vannamei (Boone) in an integrated biofloc system with Gracilaria birdiae (Greville) and Gracilaria domingensis (Kützing)

A 28-day indoor trial was conducted to evaluate the water quality, phytoplankton composition and growth of Litopenaeus vannamei in an integrated biofloc system with Gracilariabirdiae and Gracilaria domingensis. The experimental design was completely randomized with three treatments: control (shrimp monoculture); SB (shrimp and G. birdiae) and SD (shrimp and G. domingensis), all with three replicates. Random sampling was done (6xa0% of total population per experimental unit) to confirm white spot syndrome Virus (WSSV) infection using nested-PCR analysis due to suspicion of presence of the virus in the experiment (treatment and control groups). Shrimp L. vannamei (2.63xa0±xa00.10xa0g) were stocked in experimental tanks at a density of 425 shrimp m−3, and the Gracilaria was stocked at a biomass of 2.0xa0kgxa0m−3. Shrimp mortality began in both the experimental and control groups at 10xa0days of culture. The integrated biofloc system (shrimp and seaweed) increased settleable solids (by 26–52xa0%); final weight (by 6–21xa0%); weekly growth (by 17–43xa0%); weight gain (by 17–43xa0%); specific growth rate (by 16–36xa0%); and yield (by 5–7xa0%) and decreased feed conversion ratio (by 21–28xa0%) and Cyanobacteria density about 16xa0% as compared to the control (shrimp monoculture). The use of red seaweed Gracilaria in an integrated biofloc system can enhance shrimp growth and reduce Cyanobacteria density in the presence of WSSV.

Estrutura da assembléia de peixes de uma lagoa marginal desconectada do rio, no submédio Rio São Francisco, Pernambuco

Samplings with various fishing devices were undertaken between March 2007 and February 2008, in the Curralinho lake, a marginal pond located in the submedium Sao Francisco river, aiming at evaluating the fish fauna composition after its isolation from the river channel and water depletion. A total of 4,638 specimens was collected, with a biomass of 129,782.84 g, distributed in 16 families and 47 species from the Orders Characiformes, Cyprinodontiformes, Siluriformes, Perciformes, Gymnotiformes and Clupeiformes. Characiformes were most abundant and 87.3% of the specimens were small (<100 mm) or medium-sized (<200 mm). Among the species collected, 26.7% were constant, 35.6% accessory and 37.8% accidental. Characidae encompasses most of the species and individuals, followed by Acestrorhynchidae. Moenkhausia costae, Triportheus guentheri, Pygocentrus piraya and Prochilodus argenteus were present in all samples. Invertivores and piscivores dominated quantitatively and their biomass indicate a predominance of predators, with detritivores presenting the second greatest biomass. Resident species prevailed, with few individuals of migratory fish belonging to Anostomidae and Prochilodontidae families and Salminus franciscanus. Fish richness, diversity and equitability were relatively high throughout the period of study. It may be concluded that the Curralinho lake is an important shelter, feeding and resting ground for the ichthyofauna, mainly for forage fish that serve as the basis of the trophic chain and fisheries´ sustainability. Therefore, there is an urgent need of environmental policy and management practices development that would preserve habitat integrity and functionability of their role in the conservation of ichthyodiversity of this stretch of the Sao Francisco basin.

Structural and morphological features of Piaractus mesopotamicus (Holmberg, 1887) gills

The pacu Piaractus mesopotamicus (Holmberg, 1887), is a commercially important serrasalmid fish endemic to the Paraná-Paraguay River basin, and one of the most widely cultivated native fish species in the Neotropics. As a migratory species, also inhabiting temporary pools subjected to hypoxic conditions, the species presents a high plasticity concerning respiratory adaptations. In order to supplement basic knowledge on the respiratory physiology and morphology of this species, some structural features of pacu gills, such as filament and lamellae structure, and circulatory pattern are described in this paper.

Distribution of benthic macroinvertebrates in a tropical reservoir cascade

The functioning of systems arranged in cascades of reservoirs can be explained by the Cascading Reservoir Continuum Concept, providing a theoretical framework for addressing ecological processes. In this context, this study tested the following hypotheses: (i) the benthic macroinvertebrate assemblage shows a nested distribution along a reservoir cascade; and (ii) local factors explain the structure of the benthic assemblage in every reservoir along the cascade. Macroinvertebrates play essential role in aquatic systems, especially due to recycling and, in reservoirs, as important links in every food chain. Sampling was conducted quarterly between October 2006 and September 2010 in six reservoirs located in the São Francisco River, Brazil. The benthic macroinvertebrate assemblage showed nested distribution in the reservoirs, indicating that a loss of species occurs along the cascade. Each reservoir presented a different set of variables that explained the distribution of macroinvertebrates, showing the importance of local factors determining the composition and distribution of benthic assemblages in the reservoirs. Therefore, there is a clear interaction between the position of a reservoir along a cascade and the macroinvertebrate assemblages, which indicate the importance of considering this pattern during the decision-making process of constructing new dams on rivers already regulated.

Ventilatory flow relative to intrabuccal and intraopercular volumes in the serrasalmid fish Piaractus mesopotamicus during normoxia and exposed to graded hypoxia

Ventilation volume Vg - mlH2O.min-1 ), respiratory frequency (fR - breaths.min-1) and tidal volume (VT - mlH2O.breath-1 ) were measured in a group of Piaractus mesopotamicus (650.4 +/- 204.7 g; n = 10) during normoxia and in response to graded hypoxia. The fR was maintained constant, around 100 breaths.min-1, from normoxia until the O2 tension of the inspired water (PiO2) of 53 mmHg, below which it increased progressively, reaching maximum values (157.6 +/- 6.3 breaths.min-1) at 10 mmHg. The VT rose from 1.8 +/- 0.1 to 6.0 +/- 0.5 and 5.7 +/- 0.4 mlH2O. breath-1 in the PiO2 of 16 and 10 mmHg, respectively. The Vg increased from 169.3 11.0 (normoxia) to 940.1 +/- 85.6 mlH2O. min-1 at the PiO2 of 16 mmHg, below which it also tended to decrease. A second group of fish (29 to 1510.0 g, n = 34) was used for the evaluation of allometric relationships concerning ventilation and dimensions of the buccal and opercular cavities. At maximum Vg, the VT corresponded to 93.2 +/- 2.4% of the buccal volume and 94.9 2.3% of the opercular volume, suggesting that the Vg of P. mesopotamicus is limited by the volumes of buccal and opercular cavities in severe hypoxia.

O gradiente rio-barragem do reservatório de Sobradinho afeta a composição florística, riqueza e formas biológicas das macrófitas aquáticas?

O presente estudo teve por objetivo avaliar a riqueza, formas biologicas e composicao floristica de macrofitas aquaticas ao longo do eixo rio-barragem de um reservatorio no Nordeste do Brasil. Foram estabelecidas seis estacoes de amostragem ao longo de suas regioes lotica, de transicao e lentica. As coletas ocorreram nos meses de junho e julho de 2008 (periodo de estiagem), e em janeiro e fevereiro de 2009 (periodo chuvoso). Foram coletados individuos em estagio fertil ou vegetativo, tendo as especies sido categorizadas quanto as formas biologicas e os percentuais de frequencia de ocorrencia. A similaridade floristica entre os pontos de amostragem foi calculada utilizando-se o indice de Jaccard. Foram identificadas 43 especies, das quais 18 estiveram presentes na regiao lotica, 16 na de transicao e 25 na lentica. Salvinia auriculata Aubl. e Paspalum repens P.J. Bergius ocorreram em 100% das unidades amostrais. As regioes lotica e de transicao contemplaram, predominantemente, especies anfibias e emergentes, diferindo da regiao lentica, onde especies flutuantes, emergentes e submersas foram mais evidentes. A similaridade entre os ecossistemas lotico e de transicao foi maior que 50%, enquanto que entre esses ambientes e a regiao lentica foi menor que 25%.

Genetic Diversity of Captive and Wild Threatened Catfish Pseudoplatystoma corruscans in the São Francisco River

A genetic analysis was conducted of the critically endangered migratory catfish Pseudoplatystoma corruscans from the São Francisco River basin, the basin with the second highest hydropower capacity installed in Brazil. The analysis was conducted using five microsatellite markers previously described in the literature. Genetic diversity was analyzed and compared in three wild populations and a captive broodstock for a restocking program. Catfish populations of this river showed high genetic diversity in terms of heterozygosities; however, only half of the total number of alleles found in other basins were detected. Seven private alleles occurred in this basin and most of them at low frequencies, indicating they are under threat of extinction. Overall FST and assignment test suggested low differentiation among the three wild populations; however, a marked distinction between these populations and the captive broodstock was observed. The number of alleles and low average relatedness estimates found for the captive population suggest that it could be used for restocking in areas where the wild population has collapsed, but should not be used for stock enhancement in areas where the wild population is extant. These results are important as a reference for genetic aspects that should be considered in fish management activities.

Description of Atherinella brasiliensis (Quoy & Gaimard, 1825) (Atheriniformes: Atherinopsidae) larvae from the Jaguaribe River estuary, Itamaracá island, Northeastern Brazil

The present study describes the external morphology and morphometry of the initial development of Atherinella brasiliensis, and contributes toward broadening knowledge on its biology. A total of 88 larvae and 14 juveniles were used to characterize the morphological development and analyze body proportions. Fish with standard lengths (SL) from 1.4 to 77 mm were used in the study. Larvae hatch at an average of 1.4 mm SL. In the preflexion stage, the larval body is enveloped by a finfold, which begins behind the head. Pectoral fins are the first to be formed and preflexion larvae have four characteristic dendritic chromatophores on the head. The flexion stage begins at an average of 4.4 mm SL; dorsal and anal fins already exhibit pterygiophores and a terminal, somewhat up-turned mouth. At 6.8 mm SL, the flexion stage ends. In the postflexion stage, larvae present greater ossification of the dorsal and anal fin rays, exhibit pelvic fin buds and a darkening of lateral pigmentation. At an average of 8.8 mm SL, head pigmentation intensifies and pelvic fins exhibit conspicuous ossifying rays. Larvae at 11.8 mm SL have all fins formed; the second dorsal fin is the last to be formed at an insertion point posterior to the anal fin. The juvenile period begins at approximately 12 mm SL. At this stage, A. brasiliensis has an anal fin located at the median portion of the body and the posterior end of pectorals surpasses the origin of pelvic fins, which are located at the midpoint between the pectoral and anal fins. Scales are present on the dorsal-lateral region behind the head. The morphological features of A. brasiliensis herein described allow an adequate identification of its larvae and differentiate them from hemiramphid and other atheriniform larvae, thus broadening knowledge on the larval biology of the species.

Desenvolvimento inicial de larvas de Rhaphiodon vulpinus Agassiz (Characiformes, Cynodontidae)

The cynodontid fish Rhaphiodon vulpinus Agassiz, 1829, known as peixe-cachorro, is the only species of the family oceurring in the Pantanal of Mato Grosso. The initial development of its larvae was characterized, based on material collected with a 500 µm mesh size plankton-net, in several biotopes of the Pantanal of Barao de Melgaco, State of Mato Grosso, Central Brazil. The analysis was carried out with 72 larvae with standard length (SL) between 4.7 and 13.8 mm. The morphometric measurements varied positively with standard length, and body proportions ranged 8.1-17.8% for head length (HL), 6.2-10.1% for body height, and 63.673.5%, 16.8-21.6%, and 61.8-78.2% SL, respectively for pre-dorsal, pre-pectoral and pre-anal distances. The eye diameter varied positively with HL and its proportion varied between 9.1 -22.5% HL. The body relations did not show great variation along the larval development. The morphologicai characterization of larvae from 4.7 to 5.8 mm SL, in the pre-flexion phase, showed lhe presence of anembryonic finfold covering the unraycd fins, exposed branchial arches, absence of exogenous digestive content, unpigmented eyes and round shaped head. Larvae with SL between 8.1 and 13.8 mm SL were in the flexion phase, presenting a pointed head, mouth filled with externai and internai rows of numerous teeth, presence of exogenous food, pigmented eyes, branchial filaments still exposed, evident swimming-bladder, and formation of the first caudal, dorsal and anal fins rays. Only individuais in the pre-flexion and flexion phases were analyzed, and no completely developed fin was evidenced. A maximum number of 69 myomeres was counted and no evident pigmentation over the body observed. Comparing R. vulpinus larvae to those of other Characiformes, it was observed that this species and Apareiodon affinis Steindachner, 1879 present smaller body proportions, and variation range of body height, while R. vulpinus is characterized by a shorter eye diameter. The myomere number is a relevam feature for the idenlification of R. vulpinus larvae, since it is the Characiform that possesses the highest myomere number, among those species of this family studied so far.